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Shen L, Liu J, Luo A, Wang S. The stromal microenvironment and ovarian aging: mechanisms and therapeutic opportunities. J Ovarian Res 2023; 16:237. [PMID: 38093329 PMCID: PMC10717903 DOI: 10.1186/s13048-023-01300-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Accepted: 10/18/2023] [Indexed: 12/17/2023] Open
Abstract
For decades, most studies of ovarian aging have focused on its functional units, known as follicles, which include oocytes and granulosa cells. However, in the ovarian stroma, there are a variety of somatic components that bridge the gap between general aging and ovarian senescence. Physiologically, general cell types, microvascular structures, extracellular matrix, and intercellular molecules affect folliculogenesis and corpus luteum physiology alongside the ovarian cycle. As a result of damage caused by age-related metabolite accumulation and external insults, the microenvironment of stromal cells is progressively remodeled, thus inevitably perturbing ovarian physiology. With the established platforms for follicle cryopreservation and in vitro maturation and the development of organoid research, it is desirable to develop strategies to improve the microenvironment of the follicle by targeting the perifollicular environment. In this review, we summarize the role of stromal components in ovarian aging, describing their age-related alterations and associated effects. Moreover, we list some potential techniques that may mitigate ovarian aging based on their effect on the stromal microenvironment.
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Affiliation(s)
- Lu Shen
- National Clinical Research Center for Obstetrical and Gynecological Diseases, Department of Obstetrics and Gynecology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Junfeng Liu
- Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Aiyue Luo
- National Clinical Research Center for Obstetrical and Gynecological Diseases, Department of Obstetrics and Gynecology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
| | - Shixuan Wang
- National Clinical Research Center for Obstetrical and Gynecological Diseases, Department of Obstetrics and Gynecology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
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Purdue-Smithe AC, Kim K, Andriessen VC, Pollack AZ, Sjaarda LA, Silver RM, Schisterman EF, Mumford SL. Preconception leukocyte telomere length and pregnancy outcomes among women with demonstrated fecundity. Hum Reprod 2021; 36:3122-3130. [PMID: 34477845 DOI: 10.1093/humrep/deab201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 08/10/2021] [Indexed: 11/15/2022] Open
Abstract
STUDY QUESTION Is preconception leukocyte telomere length associated with fecundability, pregnancy loss and live birth among women attempting natural conception with a history of 1-2 prior pregnancy losses? SUMMARY ANSWER Preconception leukocyte telomere length is not associated with fecundability, pregnancy loss or live birth. WHAT IS KNOWN ALREADY As women increasingly delay childbearing, accessible preconception biomarkers to predict pregnancy outcomes among women seeking natural conception could improve preconception counseling. Findings of small case-control or cross-sectional studies suggest that telomere attrition is associated with adverse pregnancy outcomes among women undergoing fertility treatment, but prospective studies in non-clinical populations are lacking. STUDY DESIGN, SIZE, DURATION Participants included 1228 women aged 18-40 years with a history of 1-2 prior pregnancy losses who were recruited at four university medical centers (2006-2012). PARTICIPANTS/MATERIALS, SETTING, METHODS Preconception leukocyte telomere length was measured at baseline using PCR and reported as a ratio (T/S) in relation to population-specific standard reference DNA. Women were followed for up to six cycles while attempting to conceive. Associations of telomere length with fecundability, live birth and pregnancy loss were estimated using discrete Cox proportional hazards models and log-binomial models. MAIN RESULTS AND THE ROLE OF CHANCE After adjustment for age, BMI, smoking and other factors, preconception telomere length was not associated with fecundability (Q4 vs Q1 FOR = 1.00; 95% CI = 0.79, 1.27), live birth (Q4 vs Q1 RR = 1.00; 95% CI = 0.85, 1.19), or pregnancy loss (Q4 vs Q1 RR = 1.12; 95% CI = 0.78, 1.62). LIMITATIONS, REASONS FOR CAUTION Telomere length was measured in leukocytes, which is an accessible tissue in women attempting natural conception but may not reflect telomere length in oocytes. Most women were younger than 35 years, limiting our ability to evaluate associations among older women. Participants had a history of 1-2 prior pregnancy losses; therefore, our findings may not be widely generalizable. WIDER IMPLICATIONS OF THE FINDINGS Despite prior research suggesting that telomere length may be associated with pregnancy outcomes among women seeking fertility treatment, our findings suggest that leukocyte telomere length is not a suitable biomarker of pregnancy establishment or maintenance among women attempting natural conception. STUDY FUNDING/COMPETING INTEREST(S) This research was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (National Institutes of Health, Bethesda, MD, USA; contract numbers HHSN267200603423, HHSN267200603424 and HHSN267200603426). The authors have no conflicts of interest to disclose. TRIAL REGISTRATION NUMBER The trial was registered with ClinicalTrials.gov, number NCT00467363.
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Affiliation(s)
- Alexandra C Purdue-Smithe
- Epidemiology Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Keewan Kim
- Epidemiology Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Victoria C Andriessen
- Epidemiology Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Anna Z Pollack
- Department of Global and Community Health, College of Health and Human Services, George Mason University, Fairfax, VA, USA
| | - Lindsey A Sjaarda
- Epidemiology Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Robert M Silver
- Department of Obstetrics and Gynecology, University of Utah, Salt Lake City, UT, USA
| | - Enrique F Schisterman
- Department of Biostatistics, Epidemiology and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Sunni L Mumford
- Epidemiology Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
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3
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Singh P, Fragoza R, Blengini CS, Tran TN, Pannafino G, Al-Sweel N, Schimenti KJ, Schindler K, Alani EA, Yu H, Schimenti JC. Human MLH1/3 variants causing aneuploidy, pregnancy loss, and premature reproductive aging. Nat Commun 2021; 12:5005. [PMID: 34408140 PMCID: PMC8373927 DOI: 10.1038/s41467-021-25028-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 07/20/2021] [Indexed: 01/12/2023] Open
Abstract
Embryonic aneuploidy from mis-segregation of chromosomes during meiosis causes pregnancy loss. Proper disjunction of homologous chromosomes requires the mismatch repair (MMR) genes MLH1 and MLH3, essential in mice for fertility. Variants in these genes can increase colorectal cancer risk, yet the reproductive impacts are unclear. To determine if MLH1/3 single nucleotide polymorphisms (SNPs) in human populations could cause reproductive abnormalities, we use computational predictions, yeast two-hybrid assays, and MMR and recombination assays in yeast, selecting nine MLH1 and MLH3 variants to model in mice via genome editing. We identify seven alleles causing reproductive defects in mice including female subfertility and male infertility. Remarkably, in females these alleles cause age-dependent decreases in litter size and increased embryo resorption, likely a consequence of fewer chiasmata that increase univalents at meiotic metaphase I. Our data suggest that hypomorphic alleles of meiotic recombination genes can predispose females to increased incidence of pregnancy loss from gamete aneuploidy. Proper meiotic chromosome segregation requires mismatch repair genes MLH1 and MLH3, of which variants occur in the human population. Here, the authors use computational predictions and yeast assays to select human MLH1/3 variants for modelling in mice, observing reproductive defects from abnormal levels of crossing over.
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Affiliation(s)
- Priti Singh
- Dept of Biomedical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA.,Preclinical Modeling Core Lab, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Robert Fragoza
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, USA.,Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | | | - Tina N Tran
- Dept of Biomedical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA
| | - Gianno Pannafino
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Najla Al-Sweel
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Kerry J Schimenti
- Dept of Biomedical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA
| | | | - Eric A Alani
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Haiyuan Yu
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, USA.,Department of Computational Biology, Cornell University, Ithaca, NY, USA
| | - John C Schimenti
- Dept of Biomedical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, USA. .,Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA.
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4
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Chico-Sordo L, Córdova-Oriz I, Polonio AM, S-Mellado LS, Medrano M, García-Velasco JA, Varela E. Reproductive aging and telomeres: Are women and men equally affected? Mech Ageing Dev 2021; 198:111541. [PMID: 34245740 DOI: 10.1016/j.mad.2021.111541] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 07/01/2021] [Accepted: 07/05/2021] [Indexed: 02/06/2023]
Abstract
Successful reproduction is very important for individuals and for society. Currently, the human health span and lifespan are the object of intense and productive investigation with great achievements, compared to the last century. However, reproduction span does not progress concomitantly with lifespan. Reproductive organs age, decreasing the levels of sexual hormones, which are protectors of health through their action on several organs of the body. Thus, this is the starting point of the organismal decay and infertility. This starting point is easily detected in women. In men, it goes under the surface, undetected, but it goes, nevertheless. Regarding fertility, aging alters the hormonal equilibrium, decreases the potential of reproductive organs, diminishes the quality of the gametes and worsen the reproductive outcomes. All these events happen at a different pace and affecting different organs in women and men. The question is what molecular pathways are involved in reproductive aging and if there is a possible halting or even reversion of the aging events. Answers to all these points will be explained in the present review.
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Affiliation(s)
- Lucía Chico-Sordo
- IVI Foundation, Instituto de Investigación Sanitaria La Fe (IISLAFE), Valencia, Spain; Instituto de Investigación Sanitaria La Fe, Valencia, Spain.
| | - Isabel Córdova-Oriz
- IVI Foundation, Instituto de Investigación Sanitaria La Fe (IISLAFE), Valencia, Spain; Instituto de Investigación Sanitaria La Fe, Valencia, Spain.
| | - Alba María Polonio
- IVI Foundation, Instituto de Investigación Sanitaria La Fe (IISLAFE), Valencia, Spain; Instituto de Investigación Sanitaria La Fe, Valencia, Spain.
| | - Lucía Sánchez S-Mellado
- IVI Foundation, Instituto de Investigación Sanitaria La Fe (IISLAFE), Valencia, Spain; Instituto de Investigación Sanitaria La Fe, Valencia, Spain.
| | - Marta Medrano
- IVI Foundation, Instituto de Investigación Sanitaria La Fe (IISLAFE), Valencia, Spain; IVIRMA Madrid, Spain.
| | - Juan Antonio García-Velasco
- IVI Foundation, Instituto de Investigación Sanitaria La Fe (IISLAFE), Valencia, Spain; Instituto de Investigación Sanitaria La Fe, Valencia, Spain; IVIRMA Madrid, Spain; Rey Juan Carlos University, Madrid, Spain.
| | - Elisa Varela
- IVI Foundation, Instituto de Investigación Sanitaria La Fe (IISLAFE), Valencia, Spain; Instituto de Investigación Sanitaria La Fe, Valencia, Spain; Rey Juan Carlos University, Madrid, Spain.
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5
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Rosario R, Stewart HL, Walshe E, Anderson RA. Reduced retinoic acid synthesis accelerates prophase I and follicle activation. Reproduction 2021; 160:331-341. [PMID: 32520724 PMCID: PMC7424351 DOI: 10.1530/rep-20-0221] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 06/08/2020] [Indexed: 12/16/2022]
Abstract
In female mammals, reproductive potential is determined during fetal life by the formation of a non-renewable pool of primordial follicles. Initiation of meiosis is one of the defining features of germ cell differentiation and is well established to commence in response to retinoic acid. WIN 18,446 inhibits the conversion of retinol to retinoic acid, and therefore it was used to explore the impact of reduced retinoic acid synthesis on meiotic progression and thus germ cell development and subsequent primordial follicle formation. e13.5 mouse fetal ovaries were cultured in vitro and treated with WIN 18,446 for the first 3 days of a total of up to 12 days. Doses as low as 0.01 µM reduced transcript levels of the retinoic acid response genes Stra8 and Rarβ without affecting germ cell number. Higher doses resulted in germ cell loss, rescued with the addition of retinoic acid. WIN 18,446 significantly accelerated the progression of prophase I; this was seen as early as 48 h post treatment using meiotic chromosome spreads and was still evident after 12 days of culture using Tra98/Msy2 immunostaining. Furthermore, ovaries treated with WIN 18,446 at e13.5 but not at P0 had a higher proportion of growing follicles compared to vehicle controls, thus showing evidence of increased follicle activation. These data therefore indicate that retinoic acid is not necessary for meiotic progression but may have a role in the regulation of its progression and germ cell survival at that time and provide evidence for a link between meiotic arrest and follicle growth initiation.
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Affiliation(s)
- Roseanne Rosario
- MRC Centre for Reproductive Health, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Hazel L Stewart
- MRC Centre for Reproductive Health, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Emily Walshe
- MRC Centre for Reproductive Health, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Richard A Anderson
- MRC Centre for Reproductive Health, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
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Pendina AA, Krapivin MI, Efimova OA, Tikhonov AV, Mekina ID, Komarova EM, Koltsova AS, Gzgzyan AM, Kogan IY, Chiryaeva OG, Baranov VS. Telomere Length in Metaphase Chromosomes of Human Triploid Zygotes. Int J Mol Sci 2021; 22:ijms22115579. [PMID: 34070406 PMCID: PMC8197529 DOI: 10.3390/ijms22115579] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 05/19/2021] [Accepted: 05/21/2021] [Indexed: 02/02/2023] Open
Abstract
The human lifespan is strongly influenced by telomere length (TL) which is defined in a zygote—when two highly specialised haploid cells form a new diploid organism. Although TL is a variable parameter, it fluctuates in a limited range. We aimed to establish the determining factors of TL in chromosomes of maternal and paternal origin in human triploid zygotes. Using Q-FISH, we examined TL in the metaphase chromosomes of 28 human triploid zygotes obtained from 22 couples. The chromosomes’ parental origin was identified immunocytochemically through weak DNA methylation and strong hydroxymethylation in the sperm-derived (paternal) chromosomes versus strong DNA methylation and weak hydroxymethylation in the oocyte-derived (maternal) ones. In 24 zygotes, one maternal and two paternal chromosome sets were identified, while the four remaining zygotes contained one paternal and two maternal sets. For each zygote, we compared mean relative TLs between parental chromosomes, identifying a significant difference in favour of the paternal chromosomes, which attests to a certain “imprinting” of these regions. Mean relative TLs in paternal or maternal chromosomes did not correlate with the respective parent’s age. Similarly, no correlation was observed between the mean relative TL and sperm quality parameters: concentration, progressive motility and normal morphology. Based on the comparison of TLs in chromosomes inherited from a single individual’s gametes with those in chromosomes inherited from different individuals’ gametes, we compared intraindividual (intercellular) and interindividual variability, obtaining significance in favour of the latter and thus validating the role of heredity in determining TL in zygotes. A comparison of the interchromatid TL differences across the chromosomes from sets of different parental origin with those from PHA-stimulated lymphocytes showed an absence of a significant difference between the maternal and paternal sets but a significant excess over the lymphocytes. Therefore, interchromatid TL differences are more pronounced in zygotes than in lymphocytes. To summarise, TL in human zygotes is determined both by heredity and parental origin; the input of other factors is possible within the individual’s reaction norm.
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7
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Hassold T, Maylor-Hagen H, Wood A, Gruhn J, Hoffmann E, Broman KW, Hunt P. Failure to recombine is a common feature of human oogenesis. Am J Hum Genet 2021; 108:16-24. [PMID: 33306948 DOI: 10.1016/j.ajhg.2020.11.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Accepted: 11/09/2020] [Indexed: 12/16/2022] Open
Abstract
Failure of homologous chromosomes to recombine is arguably the most important cause of human meiotic nondisjunction, having been linked to numerous autosomal and sex chromosome trisomies of maternal origin. However, almost all information on these "exchangeless" homologs has come from genetic mapping studies of trisomic conceptuses, so the incidence of this defect and its impact on gametogenesis are not clear. If oocytes containing exchangeless homologs are selected against during meiosis, the incidence may be much higher in developing germ cells than in zygotes. To address this, we initiated studies of exchangeless chromosomes in fetal ovarian samples from elective terminations of pregnancy. In total, we examined more than 7,000 oocytes from 160 tissue samples, scoring for the number of foci per cell of the crossover-associated protein MLH1. We identified a surprisingly high level of recombination failure, with more than 7% of oocytes containing at least one chromosome pair that lacked an MLH1 focus. Detailed analyses indicate striking chromosome-specific differences, with a preponderance of MLH1-less homologs involving chromosomes 21 or 22. Further, the effect was linked to the overall level of recombination in the cell, with the presence of one or two exchangeless chromosomes in a cell associated with a 10%-20% reduction in the total number of crossovers. This suggests individuals with lower rates of meiotic recombination are at an increased risk of producing aneuploid offspring.
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8
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Effects of age on pregnancy outcomes in patients with simple tubal factor infertility receiving frozen-thawed embryo transfer. Sci Rep 2020; 10:18121. [PMID: 33093536 PMCID: PMC7581524 DOI: 10.1038/s41598-020-75124-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 10/12/2020] [Indexed: 11/17/2022] Open
Abstract
This study was to retrospectively analyze the effect of the age of embryos transfer and oocyte retrieval on the clinical pregnancy outcome in patients with simple tubal factor infertility (TFI) who received frozen-thawed embryo transfer. Patients (n = 3619) with simple TFI who underwent in vitro fertilization (IVF)/ intracytoplasmic sperm injection (ICSI) frozen-thawed embryo transfer at our hospital were enrolled. Univariate logistic regression analysis, categorical multivariate logistic regression analysis, curve fitting and threshold effect analysis were performed. Age of embryo transfer was a significant (P < 0.05) independent risk factor affecting the clinical pregnancy, live birth, and miscarriage rates. The Clinical pregnancy outcome declined significantly after the age of 34 years. After limiting the female oocyte retrieval age to ≤ 34 years, no significant change was detected in the clinical pregnancy, live birth, or miscarriage rate with increase of transplantation age. In conclusion, in patients with simple TFI undergoing IVF/ICSI frozen-thawed embryo transfer, age is a significant independent risk factor affecting the clinical pregnancy, live birth, and miscarriage rate. Aging of oocytes has a greater impact on the clinical pregnancy in women with simple TFI than the aging of the body. Patients with TFI can freeze embryos in advance to preserve fertility.
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9
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Monaghan P, Maklakov AA, Metcalfe NB. Intergenerational Transfer of Ageing: Parental Age and Offspring Lifespan. Trends Ecol Evol 2020; 35:927-937. [PMID: 32741650 DOI: 10.1016/j.tree.2020.07.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 07/06/2020] [Accepted: 07/09/2020] [Indexed: 12/21/2022]
Abstract
The extent to which the age of parents at reproduction can affect offspring lifespan and other fitness-related traits is important in our understanding of the selective forces shaping life history evolution. In this article, the widely reported negative effects of parental age on offspring lifespan (the 'Lansing effect') is examined. Outlined herein are the potential routes whereby a Lansing effect can occur, whether effects might accumulate across multiple generations, and how the Lansing effect should be viewed as part of a broader framework, considering how parental age affects offspring fitness. The robustness of the evidence for a Lansing effect produced so far, potential confounding variables, and how the underlying mechanisms might best be unravelled through carefully designed experimental studies are discussed.
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Affiliation(s)
- Pat Monaghan
- Institute of Biodiversity, Animal Health and Comparative Medicine, MVLS, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, UK.
| | - Alexei A Maklakov
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Neil B Metcalfe
- Institute of Biodiversity, Animal Health and Comparative Medicine, MVLS, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, UK
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10
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Monaghan P, Metcalfe NB. The deteriorating soma and the indispensable germline: gamete senescence and offspring fitness. Proc Biol Sci 2019; 286:20192187. [PMID: 31847776 DOI: 10.1098/rspb.2019.2187] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The idea that there is an impenetrable barrier that separates the germline and soma has shaped much thinking in evolutionary biology and in many other disciplines. However, recent research has revealed that the so-called 'Weismann Barrier' is leaky, and that information is transferred from soma to germline. Moreover, the germline itself is now known to age, and to be influenced by an age-related deterioration of the soma that houses and protects it. This could reduce the likelihood of successful reproduction by old individuals, but also lead to long-term deleterious consequences for any offspring that they do produce (including a shortened lifespan). Here, we review the evidence from a diverse and multidisciplinary literature for senescence in the germline and its consequences; we also examine the underlying mechanisms responsible, emphasizing changes in mutation rate, telomere loss, and impaired mitochondrial function in gametes. We consider the effect on life-history evolution, particularly reproductive scheduling and mate choice. Throughout, we draw attention to unresolved issues, new questions to consider, and areas where more research is needed. We also highlight the need for a more comparative approach that would reveal the diversity of processes that organisms have evolved to slow or halt age-related germline deterioration.
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Affiliation(s)
- Pat Monaghan
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow G12 8QQ, UK
| | - Neil B Metcalfe
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow G12 8QQ, UK
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11
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Marasco V, Boner W, Griffiths K, Heidinger B, Monaghan P. Intergenerational effects on offspring telomere length: interactions among maternal age, stress exposure and offspring sex. Proc Biol Sci 2019; 286:20191845. [PMID: 31575358 DOI: 10.1098/rspb.2019.1845] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Offspring produced by older parents often have reduced longevity, termed the Lansing effect. Because adults usually have similar-aged mates, it is difficult to separate effects of maternal and paternal age, and environmental circumstances are also likely to influence offspring outcomes. The mechanisms underlying the Lansing effect are poorly understood. Variation in telomere length and loss, particularly in early life, is linked to longevity in many vertebrates, and therefore changes in offspring telomere dynamics could be very important in this context. We examined the effect of maternal age and environment on offspring telomere length in zebra finches. We kept mothers under either control (ad libitum food) or more challenging (unpredictable food) circumstances and experimentally minimized paternal age and mate choice effects. Irrespective of the maternal environment, there was a substantial negative effect of maternal age on offspring telomere length, evident in longitudinal and cross-sectional comparisons (average of 39% shorter). Furthermore, in young mothers, sons reared by challenged mothers had significantly shorter telomere lengths than sons reared by control mothers. This effect disappeared when the mothers were old, and was absent in daughters. These findings highlight the importance of telomere dynamics as inter-generational mediators of the evolutionary processes determining optimal age-specific reproductive effort and sex allocation.
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Affiliation(s)
- Valeria Marasco
- Konrad Lorenz Institute of Ethology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine Vienna, Savoyenstraβe 1a, 1160 Vienna, Austria.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow G12 8QQ, UK
| | - Winnie Boner
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow G12 8QQ, UK
| | - Kate Griffiths
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow G12 8QQ, UK
| | - Britt Heidinger
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow G12 8QQ, UK.,Biological Sciences Department, North Dakota State University, Stevens Hall, Fargo, ND 58108, USA
| | - Pat Monaghan
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow G12 8QQ, UK
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12
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Pimentel RN, Navarro PA, Wang F, Robinson LG, Cammer M, Liang F, Kramer Y, Keefe DL. Amyloid-like substance in mice and human oocytes and embryos. J Assist Reprod Genet 2019; 36:1877-1890. [PMID: 31332596 DOI: 10.1007/s10815-019-01530-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 07/09/2019] [Indexed: 11/30/2022] Open
Abstract
PURPOSE To identify and characterize amyloid-like substance (ALS) in human and mouse oocytes and preimplantation embryos. METHODS An experimental prospective pilot study. A total of 252 mouse oocytes and preimplantation embryos and 50 immature and in vitro matured human oocytes and parthenogenetic human embryos, from 11 consenting fertility patients, ages 18-45. Fluorescence intensity from immunofluorescent staining and data from confocal microscopy were quantified. Data were compared by one-way analysis of variance, with the least square-MEANS post-test, Pearson correlation coefficients (r), and bivariate analyses (t tests). ALS morphology was verified using transmission electron microscopy. RESULTS Immunostaining for ALS appears throughout the zona pellucida, as well as in the cytoplasm and nucleus of mouse and human oocytes, polar bodies, and parthenogenetic embryos, and mouse preimplantation embryos. In mouse, 2-cell embryos exhibited the highest level of ALS (69000187.4 ± 6733098.07). Electron microscopy confirmed the presence of ALS. In humans, fresh germinal vesicle stage oocytes exhibited the highest level of ALS (4164.74088 ± 1573.46) followed by metaphase I and II stages (p = 0.008). There was a significant negative association between levels of ALS and patient body mass index, number of days of ovarian stimulation, dose of gonadotropin used, time between retrieval and fixation, and time after the hCG trigger. Significantly higher levels of ALS were found in patients with AMH between 1 and 3 ng/ml compared to < 1 ng/ml. CONCLUSION We demonstrate for the first time the presence, distribution, and change in ALS throughout some stages of mouse and human oocyte maturation and embryonic development. We also determine associations between ALS in human oocytes with clinical characteristics.
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Affiliation(s)
- Ricardo N Pimentel
- Research Scientist from the Department of Obstetrics and Gynecology, New York University School of Medicine, 550 First Avenue, NBV 9N1, New York, NY, USA.,Human Reproduction Division, Department of Obstetrics and Gynecology, Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto, SP, Brazil
| | - Paula A Navarro
- Human Reproduction Division, Department of Obstetrics and Gynecology, Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto, SP, Brazil
| | - Fang Wang
- Department of Obstetrics and Gynecology, Langone Medical Center, New York University, New York, NY, USA
| | - LeRoy G Robinson
- Department of Obstetrics and Gynecology, Langone Medical Center, New York University, New York, NY, USA
| | - Michael Cammer
- DART Microscopy Laboratory, New York University School of Medicine, New York, NY, USA
| | - Fengxia Liang
- DART Microscopy Laboratory, New York University School of Medicine, New York, NY, USA
| | - Yael Kramer
- Department of Obstetrics and Gynecology, Langone Medical Center, New York University, New York, NY, USA
| | - David Lawrence Keefe
- Department of Obstetrics and Gynecology, Langone Medical Center, New York University, New York, NY, USA.
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13
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Abstract
Primordial germ cells (PGCs) must complete a complex and dynamic developmental program during embryogenesis to establish the germline. This process is highly conserved and involves a diverse array of tasks required of PGCs, including migration, survival, sex differentiation, and extensive epigenetic reprogramming. A common theme across many organisms is that PGC success is heterogeneous: only a portion of all PGCs complete all these steps while many other PGCs are eliminated from further germline contribution. The differences that distinguish successful PGCs as a population are not well understood. Here, we examine variation that exists in PGCs as they navigate the many stages of this developmental journey. We explore potential sources of PGC heterogeneity and their potential implications in affecting germ cell behaviors. Lastly, we discuss the potential for PGC development to function as a multistage selection process that assesses heterogeneity in PGCs to refine germline quality.
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Affiliation(s)
- Daniel H Nguyen
- Department of Obstetrics, Gynecology and Reproductive Science, Center for Reproductive Sciences, Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California, San Francisco, CA, United States
| | - Rebecca G Jaszczak
- Department of Obstetrics, Gynecology and Reproductive Science, Center for Reproductive Sciences, Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California, San Francisco, CA, United States
| | - Diana J Laird
- Department of Obstetrics, Gynecology and Reproductive Science, Center for Reproductive Sciences, Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California, San Francisco, CA, United States.
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14
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Gao Z, Moorjani P, Sasani TA, Pedersen BS, Quinlan AR, Jorde LB, Amster G, Przeworski M. Overlooked roles of DNA damage and maternal age in generating human germline mutations. Proc Natl Acad Sci U S A 2019; 116:9491-9500. [PMID: 31019089 PMCID: PMC6511033 DOI: 10.1073/pnas.1901259116] [Citation(s) in RCA: 104] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The textbook view that most germline mutations in mammals arise from replication errors is indirectly supported by the fact that there are both more mutations and more cell divisions in the male than in the female germline. When analyzing large de novo mutation datasets in humans, we find multiple lines of evidence that call that view into question. Notably, despite the drastic increase in the ratio of male to female germ cell divisions after the onset of spermatogenesis, even young fathers contribute three times more mutations than young mothers, and this ratio barely increases with parental age. This surprising finding points to a substantial contribution of damage-induced mutations. Indeed, C-to-G transversions and CpG transitions, which together constitute over one-fourth of all base substitution mutations, show genomic distributions and sex-specific age dependencies indicative of double-strand break repair and methylation-associated damage, respectively. Moreover, we find evidence that maternal age at conception influences the mutation rate both because of the accumulation of damage in oocytes and potentially through an influence on the number of postzygotic mutations in the embryo. These findings reveal underappreciated roles of DNA damage and maternal age in the genesis of human germline mutations.
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Affiliation(s)
- Ziyue Gao
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305;
- Department of Genetics, Stanford University, Stanford, CA 94305
| | - Priya Moorjani
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
- Center for Computational Biology, University of California, Berkeley, CA 94720
| | - Thomas A Sasani
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112
| | - Brent S Pedersen
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112
| | - Aaron R Quinlan
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112
- Department of Biomedical Informatics, University of Utah School of Medicine, Salt Lake City, UT 84108
| | - Lynn B Jorde
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112
| | - Guy Amster
- Department of Biological Sciences, Columbia University, New York, NY 10027
| | - Molly Przeworski
- Department of Biological Sciences, Columbia University, New York, NY 10027;
- Department of Systems Biology, Columbia University, New York, NY 10027
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15
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Keefe DL. Telomeres and genomic instability during early development. Eur J Med Genet 2019; 63:103638. [PMID: 30862510 DOI: 10.1016/j.ejmg.2019.03.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 03/05/2019] [Indexed: 12/21/2022]
Abstract
Genomic instability is widespread during early embryo development. Aneuploidy, mosaicism, and copy number variants (CNVs) commonly appear in human preimplantation embryos. Both age-dependent meiotic aneuploidy and age-independent mitotic aneuploidy and CNVs occur In human embryos. Telomere attrition, which contributes to genomic instability in somatic cells, also may promote genomic instability in preimplantation embryos. Telomere dynamics during gametogenesis are strikingly dimorphic between females and males. Sperm telomeres lengthen with advancing paternal age, while oocyte telomeres are among the shortest in the body. Spermatogonia express telomerase activity throughout the life of the male, while oocytes and cleavage stage embryos express low or un-measureable levels of telomerase activity. Telomere attrition in oocytes contributes to meiotic dysfunction, including spindle dysmorphologies, reduced synapsis and chiasmata, as well as delayed, arrested and fragmented embryos. Cleavage stage embryos, with such inefficient telomere reconstitution, likely undergo NHEJ, which produces anaphase lag, chromosome bridges, micronuclei, and genomic instability, including mosaicism and CNVs. Cleavage stage embryos reconstitute the short telomeres inherited from their mothers by Alternative Lengthening of Telomeres (ALT), a DNA recombination based method involving RAD 50, MRE 11, Werner and Bloom proteins, as well as telomere sister chromatid exchange. ALT robustly reconstitutes telomeres, but also predisposes to genomic instability.
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Affiliation(s)
- David L Keefe
- Department of Ob/Gyn, NYU Langone Medical Center, 550 First Avenue, NBV 9N1A, New York, 10012, New York, USA.
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16
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Turner K, Lynch C, Rouse H, Vasu V, Griffin DK. Direct Single-Cell Analysis of Human Polar Bodies and Cleavage-Stage Embryos Reveals No Evidence of the Telomere Theory of Reproductive Ageing in Relation to Aneuploidy Generation. Cells 2019; 8:E163. [PMID: 30781491 PMCID: PMC6406255 DOI: 10.3390/cells8020163] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 01/28/2019] [Accepted: 02/13/2019] [Indexed: 01/18/2023] Open
Abstract
Reproductive ageing in women, particularly after the age of 35, is associated with an exponential increase in the proportion of chromosomally abnormal oocytes produced. Several hypotheses have attempted to explain this observation, including the 'limited oocyte pool' hypothesis and the 'two-hit' hypothesis, the latter explaining that a depletion in oocyte quality with age results from the multiple opportune stages for errors to occur in meiosis. Recently however, the telomere theory of reproductive ageing in women has been proposed. This suggests that shortened telomeres in oocytes of women of advanced maternal age render oocytes unable to support fertilization and embryogenesis. Despite a credible rationale for the telomere theory of reproductive ageing in women, very few studies have assessed telomere length directly in human oocytes or preimplantation embryos. Therefore, we directly assessed relative telomere length in first polar bodies and blastomeres from cleavage stage (day 3) embryos. In both cell types we tested the hypothesis that (1) older women have shorter telomeres and (2) chromosomally abnormal (aneuploid) gametes/embryos have shorter telomeres. In all cases, we found no evidence of altered telomere length associated with age-related aneuploidy.
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Affiliation(s)
- Kara Turner
- School of Biosciences, University of Kent, Giles Lane, Canterbury CT2 7NJ, UK.
| | - Colleen Lynch
- Cooper Genomics Nottingham, Medicity, D6 Building, Thane Road, Nottingham NG90 6BH, UK.
| | - Hannah Rouse
- Cooper Genomics Nottingham, Medicity, D6 Building, Thane Road, Nottingham NG90 6BH, UK.
| | - Vimal Vasu
- School of Biosciences, University of Kent, Giles Lane, Canterbury CT2 7NJ, UK.
- Department of Child Health, East Kent Hospitals University Foundation NHS Trust, William Harvey Hospital, Ashford TN24 0LZ, UK.
| | - Darren K Griffin
- School of Biosciences, University of Kent, Giles Lane, Canterbury CT2 7NJ, UK.
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17
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Farquhar CM, Bhattacharya S, Repping S, Mastenbroek S, Kamath MS, Marjoribanks J, Boivin J. Female subfertility. Nat Rev Dis Primers 2019; 5:7. [PMID: 30679436 DOI: 10.1038/s41572-018-0058-8] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Subfertility is common and affects one in six couples, half of whom lack an explanation for their delay in conceiving. Developments in the diagnosis and treatment of subfertility over the past 50 years have been truly remarkable. Indeed, current generations of couples with subfertility are more fortunate than previous generations, as they have many more opportunities to become parents. The timely access to effective treatment for subfertility is important as many couples have a narrow window of opportunity before the age-related effects of subfertility limit the likelihood of success. Assisted reproduction can overcome the barriers to fertility caused by tubal disease and low sperm count, but little progress has been made in reducing the effect of increasing age on ovarian function. The next 5-10 years will likely see further increases in birth rates in women with subfertility, a greater awareness of lifestyle factors and a possible refinement of current assisted reproduction techniques and the development of new ones. Such progress will bring challenging questions regarding the potential benefits and harms of treatments involving germ cell manipulation, artificial gametes, genetic screening of embryos and gene editing of embryos. We hope to see a major increase in fertility awareness, access to safe and cost-effective fertility care in low-income countries and a reduction in the current disparity of access to fertility care.
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Affiliation(s)
- Cynthia M Farquhar
- Department of Obstetrics and Gynaecology, University of Auckland, Auckland, New Zealand.
| | - Siladitya Bhattacharya
- College of Biomedical and Life Sciences, Cardiff University School of Medicine, Cardiff, UK
| | - Sjoerd Repping
- Amsterdam UMC, University of Amsterdam, Center for Reproductive Medicine, Amsterdam Reproduction & Development research institute, Amsterdam, Netherlands
| | - Sebastiaan Mastenbroek
- Amsterdam UMC, University of Amsterdam, Center for Reproductive Medicine, Amsterdam Reproduction & Development research institute, Amsterdam, Netherlands
| | - Mohan S Kamath
- Department of Reproductive Medicine, Christian Medical College, Vellore, India
| | - Jane Marjoribanks
- Department of Obstetrics and Gynaecology, University of Auckland, Auckland, New Zealand
| | - Jacky Boivin
- School of Psychology, College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK
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18
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Decline in Female Fertility After 40 Years. SERBIAN JOURNAL OF EXPERIMENTAL AND CLINICAL RESEARCH 2018. [DOI: 10.2478/sjecr-2018-0073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Abstract
Important factor related to the conception possibility is women age. The decline in fertility with aging is proven and evident in literature. Infertility is increasing and many couples seek help in advanced techniques such as IVF (in vitro fertilization) in order to overcome the problem caused by aging, but the quality of the oocytes is a significant limiting factor. With the aging the quantity and quality of oocytes decreases, such as the quality of the embryo after fertilization. The accelerated rhythm of life, liberty and women inclusion in all kinds of professions brought many benefits to women, but also increasingly postponing births. Each person is unique individual, and can be more or less fertile compared to the average at same age. Unfortunately, some women has a rapid decline in fertility - accelerate aging, very early, already in the early twenties and when testing them with different methods and exams, the result is very low number of oocytes, low value of anti-Müllerian hormone and also very poor quality of these oocytes, or low ovarian reserve. The problem is that when you have accelerate aging, even IVF techniques can not be of great help in achieving pregnancy. The pregnancy rate (17,65%) and the childbirth rate (5,88%) with the patients older than 40 is very low, although comparable to the data from the scientific literature and speaks in favour of the fact that the success of assisted reproductive techniques is very modest with women older than 44.
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19
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Lopes AC, Oliveira PF, Sousa M. Shedding light into the relevance of telomeres in human reproduction and male factor infertility†. Biol Reprod 2018; 100:318-330. [DOI: 10.1093/biolre/ioy215] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 09/05/2018] [Accepted: 10/01/2018] [Indexed: 12/20/2022] Open
Affiliation(s)
- Ana Catarina Lopes
- Laboratory of Cell Biology, Department of Microscopy, and Multidisciplinary Unit for Biomedical Research (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal
- Department of Life Sciences, Faculty of Sciences and Technology, New University of Lisbon (FCT-UNL), Campus Caparica, Caparica, Portugal
| | - Pedro F Oliveira
- Laboratory of Cell Biology, Department of Microscopy, and Multidisciplinary Unit for Biomedical Research (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal
- Department of Genetics, Faculty of Medicine, University of Porto, Porto, Portugal
- i3S- Institute of Research and Innovation in Health, University of Porto, Porto, Portugal
| | - Mário Sousa
- Laboratory of Cell Biology, Department of Microscopy, and Multidisciplinary Unit for Biomedical Research (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal
- Centre for Reproductive Genetics Professor Alberto Barros, Porto, Portugal
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20
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Greaney J, Wei Z, Homer H. Regulation of chromosome segregation in oocytes and the cellular basis for female meiotic errors. Hum Reprod Update 2017; 24:135-161. [PMID: 29244163 DOI: 10.1093/humupd/dmx035] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 09/12/2017] [Accepted: 11/26/2017] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Meiotic chromosome segregation in human oocytes is notoriously error-prone, especially with ageing. Such errors markedly reduce the reproductive chances of increasing numbers of women embarking on pregnancy later in life. However, understanding the basis for these errors is hampered by limited access to human oocytes. OBJECTIVE AND RATIONALE Important new discoveries have arisen from molecular analyses of human female recombination and aneuploidy along with high-resolution analyses of human oocyte maturation and mouse models. Here, we review these findings to provide a contemporary picture of the key players choreographing chromosome segregation in mammalian oocytes and the cellular basis for errors. SEARCH METHODS A search of PubMed was conducted using keywords including meiosis, oocytes, recombination, cohesion, cohesin complex, chromosome segregation, kinetochores, spindle, aneuploidy, meiotic cell cycle, spindle assembly checkpoint, anaphase-promoting complex, DNA damage, telomeres, mitochondria, female ageing and female fertility. We extracted papers focusing on mouse and human oocytes that best aligned with the themes of this review and that reported transformative and novel discoveries. OUTCOMES Meiosis incorporates two sequential rounds of chromosome segregation executed by a spindle whose component microtubules bind chromosomes via kinetochores. Cohesion mediated by the cohesin complex holds chromosomes together and should be resolved at the appropriate time, in a specific step-wise manner and in conjunction with meiotically programmed kinetochore behaviour. In women, the stage is set for meiotic error even before birth when female-specific crossover maturation inefficiency leads to the formation of at-risk recombination patterns. In adult life, multiple co-conspiring factors interact with at-risk crossovers to increase the likelihood of mis-segregation. Available evidence support that these factors include, but are not limited to, cohesion deterioration, uncoordinated sister kinetochore behaviour, erroneous microtubule attachments, spindle instability and structural chromosomal defects that impact centromeres and telomeres. Data from mice indicate that cohesin and centromere-specific histones are long-lived proteins in oocytes. Since these proteins are pivotal for chromosome segregation, but lack any obvious renewal pathway, their deterioration with age provides an appealing explanation for at least some of the problems in older oocytes. WIDER IMPLICATIONS Research in the mouse model has identified a number of candidate genes and pathways that are important for chromosome segregation in this species. However, many of these have not yet been investigated in human oocytes so it is uncertain at this stage to what extent they apply to women. The challenge for the future involves applying emerging knowledge of female meiotic molecular regulation towards improving clinical fertility management.
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Affiliation(s)
- Jessica Greaney
- Christopher Chen Oocyte Biology Research Laboratory, Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Royal Brisbane & Women's Hospital Campus, Herston QLD 4029, Australia
| | - Zhe Wei
- Christopher Chen Oocyte Biology Research Laboratory, Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Royal Brisbane & Women's Hospital Campus, Herston QLD 4029, Australia
| | - Hayden Homer
- Christopher Chen Oocyte Biology Research Laboratory, Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Royal Brisbane & Women's Hospital Campus, Herston QLD 4029, Australia
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21
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Abstract
Implantation rate decreases and miscarriage rate increases with advancing maternal age. The oocyte must be the locus of reproductive aging because donation of oocytes from younger to older women abrogates the effects of aging on fecundity. Nuclear transfer experiments in a mouse model of reproductive aging show that the reproductive aging phenotype segregates with the nucleus rather than the cytoplasm. A number of factors within the nucleus have been hypothesized to mediate reproductive aging, including disruption of cohesions, reduced chiasma, aneuploidy, disrupted meiotic spindles, and DNA damage caused by chronic exposure to reactive oxygen species. We have proposed telomere attrition as a parsimonious way to explain these diverse effects of aging on oocyte function. Telomeres are repetitive sequences of DNA and associated proteins, which form a loop (t loop) at chromosome ends. Telomeres prevent the blunt end of DNA from triggering a DNA damage response. Previously, we showed that experimental telomere shortening phenocopies reproductive aging in mice. Telomere shortening causes reduced synapsis and chiasma, chromosome fusions, embryo arrest and fragmentation, and abnormal meiotic spindles. Telomere length of polar bodies predicts the fragmentation of human embryos. Telomerase, the reverse transcriptase capable of reconstituting shortened telomeres, is only minimally active in oocytes and preimplantation embryos. Intriguingly, during the first cell cycles following activation, telomeres robustly elongate via a DNA double-strand break mechanism called alternative lengthening of telomeres (ALTs). Alternative lengthening of telomere takes place even in telomerase-null mice. This mechanism of telomere elongation previously had been found only in cancer cells lacking telomerase activity. We propose that ALT elongates telomeres across generations but does so at the cost of extensive genomic instability in preimplantation embryos.
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Affiliation(s)
- David L Keefe
- Department of Obstetrics and Gynecology, NYU Langone Medical Center, New York, NY, USA
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22
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Reichman R, Alleva B, Smolikove S. Prophase I: Preparing Chromosomes for Segregation in the Developing Oocyte. Results Probl Cell Differ 2017; 59:125-173. [PMID: 28247048 DOI: 10.1007/978-3-319-44820-6_5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Formation of an oocyte involves a specialized cell division termed meiosis. In meiotic prophase I (the initial stage of meiosis), chromosomes undergo elaborate events to ensure the proper segregation of their chromosomes into gametes. These events include processes leading to the formation of a crossover that, along with sister chromatid cohesion, forms the physical link between homologous chromosomes. Crossovers are formed as an outcome of recombination. This process initiates with programmed double-strand breaks that are repaired through the use of homologous chromosomes as a repair template. The accurate repair to form crossovers takes place in the context of the synaptonemal complex, a protein complex that links homologous chromosomes in meiotic prophase I. To allow proper execution of meiotic prophase I events, signaling processes connect different steps in recombination and synapsis. The events occurring in meiotic prophase I are a prerequisite for proper chromosome segregation in the meiotic divisions. When these processes go awry, chromosomes missegregate. These meiotic errors are thought to increase with aging and may contribute to the increase in aneuploidy observed in advanced maternal age female oocytes.
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Affiliation(s)
- Rachel Reichman
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA
| | - Benjamin Alleva
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA
| | - Sarit Smolikove
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA.
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23
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Abstract
As age at pubertal onset declines and age at first pregnancy increases, the mechanisms that regulate female reproductive lifespan become increasingly relevant to population health. The timing of menarche and menopause can have profound effects not only on fertility but also on the risk of diseases such as type 2 diabetes mellitus, cardiovascular disease and breast cancer. Genetic studies have identified dozens of highly penetrant rare mutations associated with reproductive disorders, and also ∼175 common genetic variants associated with the timing of puberty or menopause. These findings, alongside other functional studies, have highlighted a diverse range of mechanisms involved in reproductive ageing, implicating core biological processes such as cell cycle regulation and energy homeostasis. The aim of this article is to review the contribution of such genetic findings to our understanding of the molecular regulation of reproductive timing, as well as the biological basis of the epidemiological links between reproductive ageing and disease risk.
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Affiliation(s)
- John R.B. Perry
- MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Box 285 Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, CB2 0QQ
| | - Anna Murray
- Genetics of Complex Traits, University of Exeter Medical School, RILD Level 3, Royal Devon & Exeter Hospital, Barrack Road, Exeter, EX2 5DW
| | - Felix R Day
- MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Box 285 Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, CB2 0QQ
| | - Ken K Ong
- MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Box 285 Institute of Metabolic Science, Cambridge Biomedical Campus, Cambridge, CB2 0QQ
- Department of Paediatrics, University of Cambridge, Cambridge Biomedical Campus, Cambridge, CB2 0QQ
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24
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Telomere homeostasis in mammalian germ cells: a review. Chromosoma 2015; 125:337-51. [DOI: 10.1007/s00412-015-0555-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 10/19/2015] [Accepted: 10/20/2015] [Indexed: 02/03/2023]
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25
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Multicohort analysis of the maternal age effect on recombination. Nat Commun 2015; 6:7846. [PMID: 26242864 PMCID: PMC4580993 DOI: 10.1038/ncomms8846] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 06/18/2015] [Indexed: 11/09/2022] Open
Abstract
Several studies have reported that the number of crossovers increases with maternal age in humans, but others have found the opposite. Resolving the true effect has implications for understanding the maternal age effect on aneuploidies. Here, we revisit this question in the largest sample to date using single nucleotide polymorphism (SNP)-chip data, comprising over 6,000 meioses from nine cohorts. We develop and fit a hierarchical model to allow for differences between cohorts and between mothers. We estimate that over 10 years, the expected number of maternal crossovers increases by 2.1% (95% credible interval (0.98%, 3.3%)). Our results are not consistent with the larger positive and negative effects previously reported in smaller cohorts. We see heterogeneity between cohorts that is likely due to chance effects in smaller samples, or possibly to confounders, emphasizing that care should be taken when interpreting results from any specific cohort about the effect of maternal age on recombination.
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26
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Cordeiro MH, Kim SY, Ebbert K, Duncan FE, Ramalho-Santos J, Woodruff TK. Geography of follicle formation in the embryonic mouse ovary impacts activation pattern during the first wave of folliculogenesis. Biol Reprod 2015; 93:88. [PMID: 26246221 DOI: 10.1095/biolreprod.115.131227] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 08/04/2015] [Indexed: 11/01/2022] Open
Abstract
During embryonic development, mouse female germ cells enter meiosis in an anterior-to-posterior wave believed to be driven by retinoic acid. It has been proposed that ovarian follicle formation and activation follow the same general wave of meiotic progression; however, the precise anatomic specification of these processes has not been delineated. Here, we created a mouse line using Mvh, Gdf9, and Zp3 promoters to drive distinct temporal expression of three fluorescent proteins in the oocytes and to identify where the first follicle cohort develops. The fluorescent profile revealed that the first growing follicles consistently appeared in a specific region of the ovary, the anterior-dorsal region, which led us to analyze if meiotic onset occurred earlier in the dorsal ovarian region. Surprisingly, in addition to the anterior-to-posterior wave, we observed an early meiotic entry in the ventral region of the ovary. This additional anatomic stratification of meiosis contrasts with the localization of the initial follicle formation and activation in the dorsal region of the ovary. Therefore, our study suggests that the specification of cortical and medullar areas in the ventral and dorsal regions on the ovary, rather than the onset of meiosis, impacts where the first follicle activation event occurs.
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Affiliation(s)
- Marília H Cordeiro
- Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal Doctoral Programme in Experimental Biology and Biomedicine, Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - So-Youn Kim
- Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Katherine Ebbert
- Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Francesca E Duncan
- Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - João Ramalho-Santos
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - Teresa K Woodruff
- Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
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27
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Escape from crossover interference increases with maternal age. Nat Commun 2015; 6:6260. [PMID: 25695863 PMCID: PMC4335350 DOI: 10.1038/ncomms7260] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 01/09/2015] [Indexed: 11/25/2022] Open
Abstract
Recombination plays a fundamental role in meiosis, ensuring the proper segregation of chromosomes and contributing to genetic diversity by generating novel combinations of alleles. Here, we use data derived from direct-to-consumer genetic testing to investigate patterns of recombination in over 4,200 families. Our analysis reveals a number of sex differences in the distribution of recombination. We find the fraction of male events occurring within hotspots to be 4.6% higher than for females. We confirm that the recombination rate increases with maternal age, while hotspot usage decreases, with no such effects observed in males. Finally, we show that the placement of female recombination events appears to become increasingly deregulated with maternal age, with an increasing fraction of events observed within closer proximity to each other than would be expected under simple models of crossover interference. Recombination is a meiotic process that ensures accurate chromosome segregation. Here, the authors characterize recombination patterns in over 4,200 families. Their results show that recombination rate increases with maternal age, and highlight sex differences in the distribution of these events.
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Keefe D, Kumar M, Kalmbach K. Oocyte competency is the key to embryo potential. Fertil Steril 2015; 103:317-22. [DOI: 10.1016/j.fertnstert.2014.12.115] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 12/15/2014] [Accepted: 12/16/2014] [Indexed: 12/25/2022]
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Wang Y, Teng Z, Li G, Mu X, Wang Z, Feng L, Niu W, Huang K, Xiang X, Wang C, Zhang H, Xia G. Cyclic AMP in oocytes controls meiotic prophase I and primordial folliculogenesis in the perinatal mouse ovary. Development 2014; 142:343-51. [PMID: 25503411 DOI: 10.1242/dev.112755] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In mammalian ovaries, a fixed population of primordial follicles forms during the perinatal stage and the oocytes contained within are arrested at the dictyate stage of meiotic prophase I. In the current study, we provide evidence that the level of cyclic AMP (cAMP) in oocytes regulates oocyte meiotic prophase I and primordial folliculogenesis in the perinatal mouse ovary. Our results show that the early meiotic development of oocytes is closely correlated with increased levels of intra-oocyte cAMP. Inhibiting cAMP synthesis in fetal ovaries delayed oocyte meiotic progression and inhibited the disassembly and degradation of synaptonemal complex protein 1. In addition, inhibiting cAMP synthesis in in vitro cultured fetal ovaries prevented primordial follicle formation. Finally, using an in situ oocyte chromosome analysis approach, we found that the dictyate arrest of oocytes is essential for primordial follicle formation under physiological conditions. Taken together, these results suggest a role for cAMP in early meiotic development and primordial follicle formation in the mouse ovary.
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Affiliation(s)
- Yijing Wang
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China
| | - Zhen Teng
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China
| | - Ge Li
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China Guangdong Laboratory Animals Monitoring Institute, Guangzhou 510663, China
| | - Xinyi Mu
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China Department of Histology and Embryology, Chongqing Medical University, Chongqing 400016, China
| | - Zhengpin Wang
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China
| | - Lizhao Feng
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China
| | - Wanbao Niu
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China
| | - Kun Huang
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China
| | - Xi Xiang
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China
| | - Chao Wang
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China
| | - Hua Zhang
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg SE-405 30, Sweden
| | - Guoliang Xia
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, China
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Rowsey R, Gruhn J, Broman KW, Hunt PA, Hassold T. Examining variation in recombination levels in the human female: a test of the production-line hypothesis. Am J Hum Genet 2014; 95:108-12. [PMID: 24995869 DOI: 10.1016/j.ajhg.2014.06.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 06/10/2014] [Indexed: 11/17/2022] Open
Abstract
The most important risk factor for human aneuploidy is increasing maternal age, but the basis of this association remains unknown. Indeed, one of the earliest models of the maternal-age effect--the "production-line model" proposed by Henderson and Edwards in 1968--remains one of the most-cited explanations. The model has two key components: (1) that the first oocytes to enter meiosis are the first ovulated and (2) that the first to enter meiosis have more recombination events (crossovers) than those that enter meiosis later in fetal life. Studies in rodents have demonstrated that the first oocytes to enter meiosis are indeed the first to be ovulated, but the association between the timing of meiotic entry and recombination levels has not been tested. We recently initiated molecular cytogenetic studies of second-trimester human fetal ovaries, allowing us to directly examine the number and distribution of crossover-associated proteins in prophase-stage oocytes. Our observations on over 8,000 oocytes from 191 ovarian samples demonstrate extraordinary variation in recombination within and among individuals but provide no evidence of a difference in recombination levels between oocytes entering meiosis early in fetal life and those entering late in fetal life. Thus, our data provide a direct test of the second tenet of the production-line model and suggest that it does not provide a plausible explanation for the human maternal-age effect, meaning that-45 years after its introduction-we can finally conclude that the production-line model is not the basis for the maternal-age effect on trisomy.
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Affiliation(s)
- Ross Rowsey
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA
| | - Jennifer Gruhn
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA
| | - Karl W Broman
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Patricia A Hunt
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA
| | - Terry Hassold
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA.
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Mania A, Mantzouratou A, Delhanty JD, Baio G, Serhal P, Sengupta SB. Telomere length in human blastocysts. Reprod Biomed Online 2014; 28:624-37. [DOI: 10.1016/j.rbmo.2013.12.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2013] [Revised: 12/10/2013] [Accepted: 12/18/2013] [Indexed: 11/27/2022]
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Zheng W, Zhang H, Liu K. The two classes of primordial follicles in the mouse ovary: their development, physiological functions and implications for future research. Mol Hum Reprod 2014; 20:286-92. [PMID: 24448914 DOI: 10.1093/molehr/gau007] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Ovarian follicles are the basic functional units in the mammalian ovary. This review summarizes early pioneering studies and focuses on recent progress that has shown that there are two distinct classes of primordial follicles in the ovary: the first wave of primordial follicles that are activated immediately after they are formed and the adult primordial follicles that are activated gradually in later life. These two separate classes have been proposed for two decades, but sufficient experimental evidence to support this hypothesis has only been obtained recently using newly developed follicular tracing techniques in genetically modified mouse models. These two follicle populations differ from each other primarily in terms of their developmental dynamics and their contributions to ovarian physiology. It is apparent now that these two follicle populations should be treated separately, and such knowledge will hopefully lead to a more in-depth understanding of how distinct types of primordial follicles contribute to physiologic and pathologic alterations of the mammalian ovary.
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Affiliation(s)
- Wenjing Zheng
- Department of Chemistry and Molecular Biology, University of Gothenburg, SE-405 30 Gothenburg, Sweden
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Luyckx V, Scalercio S, Jadoul P, Amorim CA, Soares M, Donnez J, Dolmans MM. Evaluation of cryopreserved ovarian tissue from prepubertal patients after long-term xenografting and exogenous stimulation. Fertil Steril 2013; 100:1350-7. [DOI: 10.1016/j.fertnstert.2013.07.202] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 06/26/2013] [Accepted: 07/10/2013] [Indexed: 11/25/2022]
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Rowsey R, Kashevarova A, Murdoch B, Dickenson C, Woodruff T, Cheng E, Hunt P, Hassold T. Germline mosaicism does not explain the maternal age effect on trisomy. Am J Med Genet A 2013; 161A:2495-503. [PMID: 23950106 DOI: 10.1002/ajmg.a.36120] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 06/03/2013] [Indexed: 11/08/2022]
Abstract
A variety of hypotheses have been proposed to explain the association between trisomy and increasing maternal age in humans, virtually all of which assume that the underlying mechanisms involve meiotic errors. However, recently Hultén and colleagues [Hulten et al., 2010b] proposed a provocative model-the Oocyte Mosaicism Selection Model (OMSM)-that links age-dependent trisomy 21 to pre-meiotic errors in the ovary. Specifically, they propose that nondisjunctional events occur in a proportion of germ cells as they mitotically proliferate, resulting in mosaicism for trisomy 21. Assuming that the presence of an additional chromosome 21 delays meiotic progression, these cells would be ovulated later in reproductive life, resulting in an age-dependent increase in aneuploid eggs. Because this model has important clinical implications, we initiated studies to test it. We first analyzed oocytes from two trisomy 21 fetuses, combining immunostaining with FISH to determine the likelihood of detecting the additional chromosome 21 at different stages of meiosis. The detection of trisomy was enhanced during the earliest stage of prophase (leptotene), before homologs synapsed. Accordingly, in subsequent studies we examined the chromosome content of leptotene oocytes in seven second trimester female fetuses, analyzing three chromosomes commonly associated with human trisomies (i.e., 13, 16, and 21). In contrast to the prediction of the OMSM, we found no evidence of trisomy mosaicism for any chromosome. We conclude that errors in pre-meiotic germ cells are not a major contributor to human aneuploidy and do not provide an explanation for the age-related increase in trisomic conceptions.
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Affiliation(s)
- Ross Rowsey
- Washington State University School of Molecular Biosciences and Center for Reproductive Biology, Pullman, Washington
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35
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Gavrilov LA, Gavrilova NS. Determinants of exceptional human longevity: new ideas and findings. VIENNA YEARBOOK OF POPULATION RESEARCH 2013; 11:295-323. [PMID: 25237329 PMCID: PMC4165392 DOI: 10.1553/populationyearbook2013s295] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Studies of centenarians are useful in identifying factors leading to long life and avoidance of fatal diseases. In this article we consider several approaches to study effects of early-life and midlife conditions on survival to advanced ages: use of non-biological relatives as controls, the within-family analysis, as well as a sampling of controls from the same population universe as centenarians. These approaches are illustrated using data on American centenarians, their relatives and unrelated shorter-lived controls obtained from the online genealogies. The within-family analysis revealed that young maternal age at person's birth is associated with higher chances of exceptional longevity. Comparison of centenarians and their shorter-lived peers (died at age 65 and sampled from the same pool of online genealogies) confirmed that birth timing in the second half of the calendar year predicts survival to age 100. Parental longevity as well as some childhood and midlife characteristics also proved to be significant predictors of exceptional longevity.
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Kurahashi H, Tsutsumi M, Nishiyama S, Kogo H, Inagaki H, Ohye T. Molecular basis of maternal age-related increase in oocyte aneuploidy. Congenit Anom (Kyoto) 2012; 52:8-15. [PMID: 22348779 DOI: 10.1111/j.1741-4520.2011.00350.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Aneuploidy is one of the most common and serious pregnancy complications in humans. Most conceptuses with autosomal aneuploidy die in utero, resulting in early pregnancy loss. However, some fetuses with aneuploidy survive to term but suffer from disorders associated with congenital anomalies and mental retardation, such as Down syndrome with trisomy 21. Three general characteristics of this condition are well acknowledged: (i) in most cases the extra chromosome is of maternal origin; (ii) most cases are derived from a malsegregation event in meiosis I; and (iii) the frequency of these errors increases with maternal age. The basis for the age-dependent increase in meiosis I errors has been a long-standing enigma. Many investigators have addressed the nature of this biological phenomenon through genomic analyses of extra chromosome 21 using polymorphic markers to determine the frequency or location of crossovers that should ensure faithful chromosome segregation. Cytogenetic analyses of in vitro unfertilized oocytes have also been performed. However, no definitive conclusions regarding meiosis I errors have yet been reached from such studies. Recent findings in conditional knock-out mice for meiosis-specific cohesin have shed further light on this issue. The present review focuses on the current understanding of age-related aneuploidy and provides an overview of the mechanisms involved. We refer to recent data to illustrate some of the new paradigms that have arisen in this field.
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Affiliation(s)
- Hiroki Kurahashi
- Division of Molecular Genetics, Institute for Comprehensive Medical Science, Fujita Health University Department of Obstetrics and Gynecology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan.
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37
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Reizel Y, Itzkovitz S, Adar R, Elbaz J, Jinich A, Chapal-Ilani N, Maruvka YE, Nevo N, Marx Z, Horovitz I, Wasserstrom A, Mayo A, Shur I, Benayahu D, Skorecki K, Segal E, Dekel N, Shapiro E. Cell lineage analysis of the mammalian female germline. PLoS Genet 2012; 8:e1002477. [PMID: 22383887 PMCID: PMC3285577 DOI: 10.1371/journal.pgen.1002477] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Accepted: 11/23/2011] [Indexed: 01/11/2023] Open
Abstract
Fundamental aspects of embryonic and post-natal development, including maintenance of the mammalian female germline, are largely unknown. Here we employ a retrospective, phylogenetic-based method for reconstructing cell lineage trees utilizing somatic mutations accumulated in microsatellites, to study female germline dynamics in mice. Reconstructed cell lineage trees can be used to estimate lineage relationships between different cell types, as well as cell depth (number of cell divisions since the zygote). We show that, in the reconstructed mouse cell lineage trees, oocytes form clusters that are separate from hematopoietic and mesenchymal stem cells, both in young and old mice, indicating that these populations belong to distinct lineages. Furthermore, while cumulus cells sampled from different ovarian follicles are distinctly clustered on the reconstructed trees, oocytes from the left and right ovaries are not, suggesting a mixing of their progenitor pools. We also observed an increase in oocyte depth with mouse age, which can be explained either by depth-guided selection of oocytes for ovulation or by post-natal renewal. Overall, our study sheds light on substantial novel aspects of female germline preservation and development. Many aspects of mammalian female germline development during embryogenesis and throughout adulthood are either unknown or under debate. In this study we applied a novel method for the reconstruction of cell lineage trees utilizing microsatellite mutations, accumulated during mouse life, in oocytes and other cells, sampled from young and old mice. Analysis of the reconstructed cell lineage trees shows that oocytes are clustered separately from bone-marrow derived cells, that oocytes from different ovaries share common progenitors, and that oocyte depth (number of cell divisions since the zygote) increases significantly with mouse age.
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Affiliation(s)
- Yitzhak Reizel
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
| | - Shalev Itzkovitz
- Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Rivka Adar
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Judith Elbaz
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
| | - Adrian Jinich
- Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel
| | - Noa Chapal-Ilani
- Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel
| | - Yosef E. Maruvka
- Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel
| | - Nava Nevo
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
| | - Zipora Marx
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Inna Horovitz
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Adam Wasserstrom
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Avi Mayo
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Irena Shur
- Department of Cell and Developmental Biology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Dafna Benayahu
- Department of Cell and Developmental Biology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Karl Skorecki
- Rappaport Faculty of Medicine and Research Institute, Technion and Rambam Medical Center, Haifa, Israel
| | - Eran Segal
- Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel
| | - Nava Dekel
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
- * E-mail: (ND); (ES)
| | - Ehud Shapiro
- Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
- * E-mail: (ND); (ES)
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38
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Gavrilov LA, Gavrilova NS. Biodemography of exceptional longevity: early-life and mid-life predictors of human longevity. BIODEMOGRAPHY AND SOCIAL BIOLOGY 2012; 58:14-39. [PMID: 22582891 PMCID: PMC3354762 DOI: 10.1080/19485565.2012.666121] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This study explores the effects of early-life and middle-life conditions on exceptional longevity using two matched case-control studies. The first study compares 198 validated centenarians born in the United States between 1890 and 1893 to their shorter-lived siblings. Family histories of centenarians were reconstructed and exceptional longevity validated using early U.S. censuses, the Social Security Administration Death Master File, state death indexes, online genealogies, and other supplementary data resources. Siblings born to young mothers (aged less than 25 years) had significantly higher chances of living to 100 compared to siblings born to older mothers (odds ratio = 2.03, 95% CI = 1.33-3.11, p = .001). Paternal age and birth order were not associated with exceptional longevity. The second study explores whether people living to 100 years and beyond differ in physical characteristics at a young age from their shorter-lived peers. A random representative sample of 240 men who were born in 1887 and survived to age 100 was selected from the U.S. Social Security Administration database and linked to U.S. World War I civil draft registration cards collected in 1917 when these men were 30 years old. These validated centenarians were then compared to randomly selected controls who were matched by calendar year of birth, race, and place of draft registration in 1917. Results showed a negative association between "stout" body build (being in the heaviest 15 percent of the population) and survival to age 100. Having the occupation of "farmer" and a large number of children (4 or more) at age 30 increased the chances of exceptional longevity. The results of both studies demonstrate that matched case-control design is a useful approach in exploring effects of early-life conditions and middle-life characteristics on exceptional longevity.
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Hussin J, Roy-Gagnon MH, Gendron R, Andelfinger G, Awadalla P. Age-dependent recombination rates in human pedigrees. PLoS Genet 2011; 7:e1002251. [PMID: 21912527 PMCID: PMC3164683 DOI: 10.1371/journal.pgen.1002251] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 06/22/2011] [Indexed: 01/27/2023] Open
Abstract
In humans, chromosome-number abnormalities have been associated with altered recombination and increased maternal age. Therefore, age-related effects on recombination are of major importance, especially in relation to the mechanisms involved in human trisomies. Here, we examine the relationship between maternal age and recombination rate in humans. We localized crossovers at high resolution by using over 600,000 markers genotyped in a panel of 69 French-Canadian pedigrees, revealing recombination events in 195 maternal meioses. Overall, we observed the general patterns of variation in fine-scale recombination rates previously reported in humans. However, we make the first observation of a significant decrease in recombination rates with advancing maternal age in humans, likely driven by chromosome-specific effects. The effect appears to be localized in the middle section of chromosomal arms and near subtelomeric regions. We postulate that, for some chromosomes, protection against non-disjunction provided by recombination becomes less efficient with advancing maternal age, which can be partly responsible for the higher rates of aneuploidy in older women. We propose a model that reconciles our findings with reported associations between maternal age and recombination in cases of trisomies.
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Affiliation(s)
- Julie Hussin
- Department of Biochemistry, Faculty of Medicine, University of Montreal, Montreal, Canada
- Sainte-Justine Hospital Research Centre, Montreal, Canada
| | - Marie-Hélène Roy-Gagnon
- Sainte-Justine Hospital Research Centre, Montreal, Canada
- Department of Social and Preventive Medicine, Faculty of Medicine, University of Montreal, Montreal, Canada
| | | | - Gregor Andelfinger
- Sainte-Justine Hospital Research Centre, Montreal, Canada
- Department of Pediatrics, Faculty of Medicine, University of Montreal, Montreal, Canada
| | - Philip Awadalla
- Sainte-Justine Hospital Research Centre, Montreal, Canada
- Department of Pediatrics, Faculty of Medicine, University of Montreal, Montreal, Canada
- * E-mail:
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40
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Gavrilova NS, Gavrilov LA. Search for mechanisms of exceptional human longevity. Rejuvenation Res 2010; 13:262-4. [PMID: 20370503 DOI: 10.1089/rej.2009.0968] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
This study presents initial findings of a new ongoing research project aimed to identify important predictors and mechanisms of exceptional human longevity. For this purpose the detailed data on long-lived people surviving to 100 years in the Unites States are collected, validated, and analyzed. The study found that being born to a young mother is an important predictor of person's longevity. The study also found that the "stout" body build at age 30 years (being in the heaviest 15% of population) significantly decreases chances of survival to 100 years. These findings demonstrate that early-life and mid-life personal characteristics play an important role in human longevity.
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Affiliation(s)
- Natalia S Gavrilova
- Center on Aging, NORC and The University of Chicago, Chicago, Illinois 60637, USA.
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41
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Hartshorne GM, Lyrakou S, Hamoda H, Oloto E, Ghafari F. Oogenesis and cell death in human prenatal ovaries: what are the criteria for oocyte selection? Mol Hum Reprod 2009; 15:805-19. [PMID: 19584195 DOI: 10.1093/molehr/gap055] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Prenatal oogenesis produces hundreds of thousands of oocytes, most of which are discarded through apoptosis before birth. Despite this large-scale selection, the survivors do not constitute a perfect population, and the factors at the cellular level that result in apoptosis or survival of any individual oocyte are largely unknown. What then are the selection criteria that determine the size and quality of the ovarian reserve in women? This review focuses on new data at the cellular level, on human prenatal oogenesis, offering clues about the importance of the timing of entry to meiotic prophase I by linking the stages and progress through MPI with the presence or absence of apoptotic markers. The characteristics and responsiveness of cultured human fetal ovarian tissue at different gestational ages to growth factor supplementation and the impact of meiotic abnormalities upon apoptotic markers are discussed. Future work will require the use of a tissue culture model of prenatal oogenesis in order to investigate the fate of individual live oocytes at different stages of development.
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Affiliation(s)
- G M Hartshorne
- Clinical Sciences Research Institute, Warwick Medical School, University of Warwick, Coventry CV2 2DX, UK.
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42
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Abstract
Infertility, miscarriage and aneuploid offspring increase with age in women, and meiotic dysfunction underlies reproductive aging. How aging disrupts meiotic function in women remains unclear, but as women increasingly delay having children, solving this problem becomes an urgent priority. Telomeres consist of a (TTAGGG)(n) repeated sequence and associated proteins at chromosome ends, mediate aging in mitotic cells and may also mediate aging during meiosis. Telomeres shorten both during DNA replication and from the response to oxidative DNA damage. Oocytes do not divide in adult mammals, but their precursors do replicate during fetal oogenesis; eggs ovulated from older females have traversed more mitotic cell cycles before entering meiosis during fetal oogenesis than eggs ovulated from younger females. Telomeres also would be expected to shorten from inefficient DNA repair of oxidative damage, because the interval between fetal oogenesis and ovulation is exceptionally prolonged in women. We have tested the hypothesis that telomere shortening disrupts meiosis by shortening telomeres experimentally in mice, which normally do not exhibit age-related meiotic dysfunction. Interestingly, mouse telomeres are much longer than human telomeres, but genetic or pharmacological shortening of mouse telomeres recapitulates in mice the human reproductive aging phenotype as the mouse telomeres reach the length of telomeres from older women. These observations led us to propose a telomere theory of reproductive aging. Moreover, chronological oxidative stress increases with reproductive aging, leading to DNA damage preferentially at (TTAGGG)(n) repeats. Finally, if telomeres shorten with aging, how do they reset across generations? Telomerase could not play a significant role in telomere elongation during early development, because this enzyme is not active until the blastocyst stage, well after the stage when telomere elongation takes place. Rather, telomeres lengthen during the early cell cycles of development by a novel mechanism involving recombination and sister chromatid exchange. Telomere dysfunction resulting from oxidative stress, a DNA damage response or aberrant telomere recombination may contribute to reproductive aging-associated meiotic defects, miscarriage and infertility.
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Affiliation(s)
- David L Keefe
- Department of Ob/Gyn, University of South Florida, Tampa, FL 33606, USA.
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43
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Fertility in women with BRCA mutations: a case-control study. Fertil Steril 2009; 93:1805-8. [PMID: 19200971 DOI: 10.1016/j.fertnstert.2008.12.052] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2008] [Revised: 10/28/2008] [Accepted: 12/12/2008] [Indexed: 01/16/2023]
Abstract
OBJECTIVE To investigate whether or not fertility is reduced in women carrying mutations in the BRCA genes (BRCA1 and BRCA2), compared with noncarrier family members. DESIGN Matched case-control study. SETTING Academic. PATIENT(S) A total of 2,254 BRCA carriers and 764 noncarrier controls who were from the same families as the carriers, but tested negative for the BRCA mutation. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) History of fertility problems (yes/no) and prior use of fertility medications (yes/no) in cases and controls, obtained through administered questionnaire. RESULT(S) There was no difference in mean parity between carriers (1.9) and noncarriers (1.9). CONCLUSION(S) This study, which is the first epidemiologic study to specifically investigate the effect of carrying a BRCA mutation on parity and fertility, suggests that there is likely little or no effect of the BRCA gene mutation on fertility. To our knowledge previous epidemiologic studies have not investigated the effect of carrying a BRCA mutation on parity or fertility. However, we expect that if fertility differences exist, they would be toward the limits of reproductive life, thus larger studies with age-stratified analyses are needed to definitively answer this question.
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44
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Adriaens I, Smitz J, Jacquet P. The current knowledge on radiosensitivity of ovarian follicle development stages. Hum Reprod Update 2009; 15:359-77. [PMID: 19151106 DOI: 10.1093/humupd/dmn063] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND The aim of this paper is to review the available information on ovarian radiation sensitivity and the genetic hazard of ionizing radiation in female mammals including humans. METHODS The literature present in the author's laboratories (international papers from the 1970s) was complemented by a Medline literature search using the keywords 'ionizing radiation genetic effects', 'oocyte radiosensitivity' and 'oocyte DNA repair' (1990-2008). Further articles were acquired from citations in the research papers and reports. RESULTS Animal data show that oocyte radiosensitivity varies widely according to the follicle/oocyte stage and the species. Oocytes near ovulation show the highest susceptibility to radiation induction of mutational events. Congenital anomalies have been observed after exposure to high doses (1-5 Gy), but extrapolation of these data to humans requires caution. In humans, the dose required to induce permanent ovarian failure would vary from 20.3 Gy at birth to 14.3 Gy at 30 years. Most epidemiological studies found little evidence of genetic diseases at the doses at which medical, occupational or accidental exposure occurred. CONCLUSIONS The fact that genetic effects were observed in irradiated animals suggests that these could also occur in humans. The probability of such events remains low compared with the 'spontaneous' risks of genetic effects.
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Affiliation(s)
- I Adriaens
- Follicle Biology Laboratory, Free University of Brussels, Laarbeeklaan 101, B-1090 Jette, Belgium.
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Abstract
Oocytes are sequestered in primordial follicles before birth and remain quiescent in the ovary, often for decades, until recruited into the growing pool throughout the reproductive years. Therefore, activation of follicle growth is a major biological checkpoint that controls female reproductive potential. However, we are only just beginning to elucidate the cellular mechanisms required for either maintenance of the quiescent primordial follicle pool or initiation of follicle growth. Understanding the intracellular signalling systems that control oocyte maintenance and activation has significant implications for improving female reproductive productivity and longevity in mammals, and has application in domestic animal husbandry, feral animal population control and infertility in women.
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Affiliation(s)
- Eileen A McLaughlin
- Reproductive Science Group, School of Environmental & Life Sciences and ARC Centre of Excellence in Biotechnology & Development, University of Newcastle, Callaghan, New South Wales, Australia.
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Jones KT. Meiosis in oocytes: predisposition to aneuploidy and its increased incidence with age. Hum Reprod Update 2007; 14:143-58. [PMID: 18084010 DOI: 10.1093/humupd/dmm043] [Citation(s) in RCA: 150] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Mammalian oocytes begin meiosis in the fetal ovary, but only complete it when fertilized in the adult reproductive tract. This review examines the cell biology of this protracted process: from entry of primordial germ cells into meiosis to conception. The defining feature of meiosis is two consecutive cell divisions (meiosis I and II) and two cell cycle arrests: at the germinal vesicle (GV), dictyate stage of prophase I and at metaphase II. These arrests are spanned by three key events, the focus of this review: (i) passage from mitosis to GV arrest during fetal life, regulated by retinoic acid; (ii) passage through meiosis I and (iii) completion of meiosis II following fertilization, both meiotic divisions being regulated by cyclin-dependent kinase (CDK1) activity. Meiosis I in human oocytes is associated with an age-related high rate of chromosomal mis-segregation, such as trisomy 21 (Down's syndrome), resulting in aneuploid conceptuses. Although aneuploidy is likely to be multifactorial, oocytes from older women may be predisposed to be becoming aneuploid as a consequence of an age-long decline in the cohesive ties holding chromosomes together. Such loss goes undetected by the oocyte during meiosis I either because its ability to respond and block division also deteriorates with age, or as a consequence of being inherently unable to respond to the types of segregation defects induced by cohesion loss.
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Affiliation(s)
- Keith T Jones
- Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle, NE2 4HH, UK.
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Abstract
Paul Polani (1914-2006) was one of the key figures internationally in the beginnings and development of medical genetics. Best remembered scientifically for his highly original work on the basis of human sex chromosome disorders, notably Turner syndrome, he pioneered the application of basic biological research to clinical genetic problems. The unit that he founded in 1960, at Guys Hospital, London, provided an unparalleled model for combined research and service in medical genetics across a wide range of laboratory areas and helped to establish medical genetics as a specific discipline.
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Affiliation(s)
- Peter S Harper
- Institute of Medical Genetics, Cardiff University, Heath Park, Cardiff, UK.
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Abstract
PURPOSE OF REVIEW A unifying theory of reproductive aging, based on telomere shortening, is proposed. RECENT FINDINGS Telomere shortening may mediate both 'hits' involved in reproductive aging, that is late exit from the fetal production line and long interval to ovulation in the adult. SUMMARY As women age egg dysfunction increases, with meiotic nondisjunction, embryonic arrest, apoptosis, and miscarriage. Egg dysfunction results from two 'hits' - reduced formation of chiasmata during fetal oogenesis, and accumulation of reactive oxygen damage during the prolonged interval until ovulation. Late exit from a production line during oogenesis presumably contributes to the first hit. The later insult also involves meiotic spindle abnormalities. Telomeres, repetitive sequences of DNA, cap chromosome ends and dissipate during divisions. Oocytes do not divide, but oogonia do, and telomerase, the enzyme responsible for maintaining telomere length, is inefficient, and remains inactive in oocytes and embryos until blastocyst stage. Reactive oxygen also shortens telomeres, so the prolonged interval between birth and ovulation would further shorten telomeres from chronic exposure to reactive oxygen. In support of this theory, experimental shortening of telomeres in mice produced a phenotype similar to reproductive aging in women, with abnormal chiasmata, spindles, cell cycles, apoptosis, and genomic instability, and telomere length in human eggs correlated with in-vitro fertilization outcome.
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Affiliation(s)
- David L Keefe
- University of South Florida, Department of Obstetrics and Gynecology, Tampa, Florida 33606, USA.
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Ubaldi FM, Rienzi L, Ferrero S, Baroni E, Sapienza F, Cobellis L, Greco E. Management of poor responders in IVF. Reprod Biomed Online 2005; 10:235-46. [PMID: 15823231 DOI: 10.1016/s1472-6483(10)60946-7] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Correct controlled ovarian stimulation is of paramount importance in assisted reproductive technologies. Therefore, analysis of the ovarian reserve of the patient is mandatory to tailor the best ovarian stimulation regimen. When the ovarian reserve is reduced, the induction of a multifollicular growth remains a challenge. Several factors could be associated with reduced ovarian response. However, reduced ovarian reserve either in older patients or in young patients represents the most frequent aetiological factor. Whatever is the aetiology, one of the main problems is how to predict a reduced ovarian response, and although several tests have been suggested, no very accurate predictive test is available. A variety of different stimulation protocols have been suggested but the lack of any large-scale, prospective, randomized, controlled trials of the different management strategies and the lack of a uniform definition of the population may result in comparisons of heterogeneous groups of patients, making it difficult to draw any definitive conclusions. Natural cycle IVF may represent an easy and cheap approach in the management of this group of patients. Although no controlled large prospective randomized studies are available to compare the natural IVF procedure with ovarian stimulation IVF in poor responder patients, the efficacy of natural cycle IVF is hampered by high cancellation rates mainly due to untimely LH surge. The use of gonadotrophin-releasing hormone antagonists in the late follicular phase, which reduces the premature LH rise rate, and the improvements in laboratory conditions and fertilization techniques, increase the embryo transfer rates, making this procedure more cost-effective.
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Affiliation(s)
- F M Ubaldi
- Centre for Reproductive Medicine, European Hospital, Via Portuense 700-00148, Rome, Italy.
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Keefe DL, Franco S, Liu L, Trimarchi J, Cao B, Weitzen S, Agarwal S, Blasco MA. Telomere length predicts embryo fragmentation after in vitro fertilization in women--toward a telomere theory of reproductive aging in women. Am J Obstet Gynecol 2005; 192:1256-60; discussion 1260-1. [PMID: 15846215 DOI: 10.1016/j.ajog.2005.01.036] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OBJECTIVE Telomeres are DNA repeats which cap and protect chromosome ends, facilitate homologue pairing and chiasmata formation during early meiosis, and shorten with cell division and exposure to reactive oxygen to mediate aging. Early germ cells contain telomerase, a reverse transcriptase which adds telomeres to 3-prime DNA ends, but telomerase activity declines in oocytes, fixing telomere length earlier during development. Experimentally induced telomere shortening in mice disrupts meiosis, impairs chiasmata formation, halts embryonic cell cycles, and promotes apoptosis in embryos, a phenotype which mimics reproductive senescence in women. Ethical constraints limit study of human embryos to nondestructive assays, such as morphologic evaluation under transmission optics, but cytoplasmic fragmentation is a reliable marker of apoptosis. STUDY DESIGN Study design consisted of observational study of effect of telomere length in human eggs on cytoplasmic fragmentation, and on other morphologic features of preimplantation embryos. To test the hypothesis that telomere shortening triggers apoptosis in human embryos, we evaluated telomere length as a predictor of cytoplasmic fragmentation in embryos from women undergoing in vitro fertilization. RESULTS Telomere length negatively predicted fragmentation in day 3 preimplantation embryos, after controlling for patient age and basal follicle stimulating hormone level. Telomere length did not predict other features of preimplantation embryo morphology. CONCLUSION The finding that telomere length in human eggs predicts cytoplasmic fragmentation in embryos provides evidence that telomere shortening induces apoptosis in human preimplantation embryos, consistent with a telomere theory of reproductive senescence in women.
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Affiliation(s)
- David L Keefe
- Dept of Ob/Gyn, Brown University, Woman and Infants Hospital, 101 Dudley St, Providence, RI 02905, USA.
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