1
|
Aitken RJ. What is driving the global decline of human fertility? Need for a multidisciplinary approach to the underlying mechanisms. FRONTIERS IN REPRODUCTIVE HEALTH 2024; 6:1364352. [PMID: 38726051 PMCID: PMC11079147 DOI: 10.3389/frph.2024.1364352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 04/03/2024] [Indexed: 05/12/2024] Open
Abstract
An intense period of human population expansion over the past 250 years is about to cease. Total fertility rates are falling dramatically all over the world such that highly industrialized nations, including China and the tiger economies of SE Asia, will see their populations decline significantly in the coming decades. The socioeconomic, geopolitical and environmental ramifications of this change are considerable and invite a multidisciplinary consideration of the underlying mechanisms. In the short-term, socioeconomic factors, particularly urbanization and delayed childbearing are powerful drivers of reduced fertility. In parallel, lifestyle factors such as obesity and the presence of numerous reproductive toxicants in the environment, including air-borne pollutants, nanoplastics and electromagnetic radiation, are seriously compromising reproductive health. In the longer term, it is hypothesized that the reduction in family size that accompanies the demographic transition will decrease selection pressure on high fertility genes leading to a progressive loss of human fecundity. Paradoxically, the uptake of assisted reproductive technologies at scale, may also contribute to such fecundity loss by encouraging the retention of poor fertility genotypes within the population. Since the decline in fertility rate that accompanies the demographic transition appears to be ubiquitous, the public health implications for our species are potentially devastating.
Collapse
Affiliation(s)
- Robert John Aitken
- Priority Research Centre for Reproductive Science, Discipline of Biological Sciences, School of Environmental and Life Sciences, College of Engineering Science and Environment, University of Newcastle, Callaghan, NSW, Australia
- Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
| |
Collapse
|
2
|
Irigoyen P, Mansilla S, Castro L, Cassina A, Sapiro R. Mitochondrial function and reactive oxygen species production during human sperm capacitation: Unraveling key players. FASEB J 2024; 38:e23486. [PMID: 38407497 DOI: 10.1096/fj.202301957rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 01/22/2024] [Accepted: 01/30/2024] [Indexed: 02/27/2024]
Abstract
Sperm capacitation is a critical process for male fertility. It involves a series of biochemical and physiological changes that occur in the female reproductive tract, rendering the sperm competent for successful fertilization. The precise mechanisms and, specifically, the role of mitochondria, in sperm capacitation remain incompletely understood. Previously, we revealed that in mouse sperm mitochondrial activity (e.g., oxygen consumption, membrane potential, ATP/ADP exchange, and mitochondrial Ca2+ ) increases during capacitation. Herein, we studied mitochondrial function by high-resolution respirometry (HRR) and reactive oxygen species production in capacitated (CAP) and non-capacitated (NC) human spermatozoa. We found that in capacitated sperm from normozoospermic donors, the respiratory control ratio increased by 36%, accompanied by a double oxygen consumption rate (OCR) in the presence of antimycin A. Extracellular hydrogen peroxide (H2 O2 ) detection was three times higher in CAP than in NC sperm cells. To confirm that H2 O2 production depends on mitochondrial superoxide (O 2 · - $$ {\mathrm{O}}_2^{\cdotp -} $$ ) formation, we evaluated mitochondrial aconitase (ACO2) amount, activity, and role in the metabolic flux from the sperm tricarboxylic acid cycle. We estimated that CAP cells produce, on average by individual, (59 ± 22)% moreO 2 · - $$ {\mathrm{O}}_2^{\cdotp -} $$ in the steady-state compared to NC cells. Finally, we analyzed two targets of oxidative stress: lipid peroxidation by western blot against 4-hydroxynonenal and succinate dehydrogenase (SDH) activity by HRR. We did not observe modifications in lipoperoxidation nor the activity of SDH, suggesting that during capacitation, the increase in mitochondrial H2 O2 production does not damage sperm and it is necessary for the normal CAP process.
Collapse
Affiliation(s)
- Pilar Irigoyen
- Unidad Académica Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
- Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Santiago Mansilla
- Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
- Departamento de Métodos Cuantitativos, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Laura Castro
- Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Adriana Cassina
- Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Rossana Sapiro
- Unidad Académica Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
- Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| |
Collapse
|
3
|
Sawant S, Oluwayiose OA, Nowak K, Maxwell DL, Houle E, Paskavitz AL, Saddiki H, Bertolla RP, Pilsner JR. Associations between Sperm Epigenetic Age and Semen Parameters: An Evaluation of Clinical and Non-Clinical Cohorts. Curr Issues Mol Biol 2024; 46:1567-1578. [PMID: 38392219 PMCID: PMC10887546 DOI: 10.3390/cimb46020101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 02/08/2024] [Accepted: 02/12/2024] [Indexed: 02/24/2024] Open
Abstract
The well-documented relationship between chronological age and the sperm methylome has allowed for the construction of epigenetic clocks that estimate the biological age of sperm based on DNA methylation, which we previously termed sperm epigenetic age (SEA). Our lab demonstrated that SEA is positively associated with the time taken to achieve pregnancy; however, its relationship with semen parameters is unknown. A total of 379 men from the Longitudinal Investigation of Fertility and Environment (LIFE) study, a non-clinical cohort, and 192 men seeking fertility treatment from the Sperm Environmental Epigenetics and Development Study (SEEDS) were included in the study. Semen analyses were conducted for both cohorts, and SEA was previously generated using a machine learning algorithm and DNA methylation array data. Association analyses were conducted via multivariable linear regression models adjusting for BMI and smoking status. We found that SEA was not associated with standard semen characteristics in SEEDS and LIFE cohorts. However, SEA was significantly associated with higher sperm head length and perimeter, the presence of pyriform and tapered sperm, and lower sperm elongation factor in the LIFE study (p < 0.05). Based on our results, SEA is mostly associated with defects in sperm head morphological factors that are less commonly evaluated during male infertility assessments. SEA shows promise to be an independent biomarker of sperm quality to assess male fecundity.
Collapse
Affiliation(s)
- Savni Sawant
- C.S. Mott Center for Human Growth and Development, Department of Obstetrics and Gynecology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
- Department of Biochemistry, Microbiology, Immunology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Oladele A Oluwayiose
- C.S. Mott Center for Human Growth and Development, Department of Obstetrics and Gynecology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Karolina Nowak
- C.S. Mott Center for Human Growth and Development, Department of Obstetrics and Gynecology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - DruAnne L Maxwell
- C.S. Mott Center for Human Growth and Development, Department of Obstetrics and Gynecology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Emily Houle
- C.S. Mott Center for Human Growth and Development, Department of Obstetrics and Gynecology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Amanda L Paskavitz
- C.S. Mott Center for Human Growth and Development, Department of Obstetrics and Gynecology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Hachem Saddiki
- Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Ricardo P Bertolla
- Department of Surgery, Division of Urology, Human Reproduction Section, São Paulo Federal University, São Paulo 04024-001, Brazil
| | - J Richard Pilsner
- C.S. Mott Center for Human Growth and Development, Department of Obstetrics and Gynecology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI 48201, USA
| |
Collapse
|
4
|
Wyrwoll MJ, van der Heijden GW, Krausz C, Aston KI, Kliesch S, McLachlan R, Ramos L, Conrad DF, O'Bryan MK, Veltman JA, Tüttelmann F. Improved phenotypic classification of male infertility to promote discovery of genetic causes. Nat Rev Urol 2024; 21:91-101. [PMID: 37723288 DOI: 10.1038/s41585-023-00816-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/16/2023] [Indexed: 09/20/2023]
Abstract
An increasing number of genes are being described in the context of non-syndromic male infertility. Linking the underlying genetic causes of non-syndromic male infertility with clinical data from patients is important to establish new genotype-phenotype correlations. This process can be facilitated by using universal nomenclature, but no standardized vocabulary is available in the field of non-syndromic male infertility. The International Male Infertility Genomics Consortium aimed at filling this gap, providing a standardized vocabulary containing nomenclature based on the Human Phenotype Ontology (HPO). The "HPO tree" was substantially revised compared with the previous version and is based on the clinical work-up of infertile men, including physical examination and hormonal assessment. Some causes of male infertility can already be suspected based on the patient's clinical history, whereas in other instances, a testicular biopsy is needed for diagnosis. We assembled 49 HPO terms that are linked in a logical hierarchy and showed examples of morphological features of spermatozoa and testicular histology of infertile men with identified genetic diagnoses to describe the phenotypes. This work will help to record patients' phenotypes systematically and facilitate communication between geneticists and andrologists. Collaboration across institutions will improve the identification of patients with the same phenotypes, which will promote the discovery of novel genetic causes for non-syndromic male infertility.
Collapse
Affiliation(s)
- Margot J Wyrwoll
- Institute of Reproductive Genetics, University of Münster, Münster, Germany
| | | | - Csilla Krausz
- Department of Biomedical, Experimental and Clinical Sciences "Mario Serio", University of Florence, University Hospital of Careggi (AOUC), Florence, Italy
| | - Kenneth I Aston
- Andrology and IVF Laboratory, Department of Surgery (Urology), University of Utah, Salt Lake City, UT, USA
| | - Sabine Kliesch
- Centre of Reproductive Medicine and Andrology, Department of Clinical and Surgical Andrology, University of Münster, Münster, Germany
| | - Robert McLachlan
- Department of Clinical Research, Hudson Institute of Medical Research, Melbourne, Victoria, Australia
| | - Liliana Ramos
- Department of Obstetrics and Gynecology, Radboud University Medical Center, Nijmegen, Netherlands
| | - Donald F Conrad
- Department of Genetics, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR, USA
| | - Moira K O'Bryan
- School of BioSciences and Bio21 Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Joris A Veltman
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Frank Tüttelmann
- Institute of Reproductive Genetics, University of Münster, Münster, Germany.
| |
Collapse
|
5
|
Yang Z, Zhang L, Fan H, Yan B, Mu Y, Zhou Y, Pei C, Li L, Xiao X. Gaussian clustering and quantification of the sperm chromatin dispersion test using convolutional neural networks. Analyst 2024; 149:366-375. [PMID: 38044817 DOI: 10.1039/d3an01616a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Sperm DNA fragmentation is a sign of sperm nuclear damage. The sperm chromatin dispersion (SCD) test is a reliable and economical method for the evaluation of DNA fragmentation. However, the cut-off value for differentiation of DNA fragmented sperms is fixed at 1/3 with limited statistical justification, making the SCD test a semi-quantitative method that gives user-dependent results. We construct a collection of deep neural networks to automate the evaluation of bright-field images for SCD tests. The model can detect valid sperm nuclei and their locations from the input images captured with a 20× objective and predict the geometric parameters of the halo ring. We construct an annotated dataset consisting of N = 3120 images. The ResNet 18 based network reaches an average precision (AP50) of 91.3%, a true positive rate of 96.67%, and a true negative rate of 96.72%. The distribution of relative halo radii is fit to the multi-peak Gaussian function (p > 0.99). DNA fragmentation is regarded as those with a relative halo radius 1.6 standard deviations smaller than the mean of a normal cluster. In conclusion, we have established a deep neural network based model for the automation and quantification of the SCD test that is ready for clinical application. The DNA fragmentation index is determined using Gaussian clustering, reflecting the natural distribution of halo geometry and is more tolerable to disturbances and sample conditions, which we believe will greatly improve the clinical significance of the SCD test.
Collapse
Affiliation(s)
- Zheng Yang
- Institute of Reproductive Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China.
| | - Lei Zhang
- Institute of Reproductive Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China.
| | - Heng Fan
- Institute of Reproductive Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China.
| | - Bei Yan
- Institute of Reproductive Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China.
- Ningxia Human Sperm Bank, Institute of Medical Sciences, General Hospital of Ningxia Medical University, Yinchuan, 750004, PR China
| | - Yaoqin Mu
- Institute of Reproductive Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China.
| | - Yue Zhou
- Ningxia Human Sperm Bank, Institute of Medical Sciences, General Hospital of Ningxia Medical University, Yinchuan, 750004, PR China
| | - Chengbin Pei
- Ningxia Human Sperm Bank, Institute of Medical Sciences, General Hospital of Ningxia Medical University, Yinchuan, 750004, PR China
| | - Longjie Li
- School of Life Science and Technology, Wuhan Polytechnic University, Wuhan, 430023, PR China.
| | - Xianjin Xiao
- Institute of Reproductive Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, PR China.
- Hunan Provincial Key Laboratory of Regional Hereditary Birth Defects Prevention and Control, Changsha Hospital for Maternal and Child Health Care Affiliated to Hunan Normal University, Changsha, PR China
| |
Collapse
|
6
|
Esteves SC, Coimbra I, Hallak J. Surgically retrieved spermatozoa for ICSI cycles in non-azoospermic males with high sperm DNA fragmentation in semen. Andrology 2023; 11:1613-1634. [PMID: 36734283 DOI: 10.1111/andr.13405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 01/16/2023] [Accepted: 01/29/2023] [Indexed: 02/04/2023]
Abstract
Intracytoplasmic sperm injection (ICSI) using surgically retrieved spermatozoa outside the classic context of azoospermia has been increasingly used to overcome infertility. The primary indications include high levels of sperm DNA damage in ejaculated spermatozoa and severe oligozoospermia or cryptozoospermia, particularly in couples with ICSI failure for no apparent reason. Current evidence suggests that surgically retrieved spermatozoa for ICSI in the above context improves outcomes, mainly concerning pregnancy and miscarriage rates. The reasons are not fully understood but may be related to the lower levels of DNA damage in spermatozoa retrieved from the testis compared with ejaculated counterparts. These findings are consistent with the notion that excessive sperm DNA damage can be a limiting factor responsible for the failure to conceive. Using testicular in preference of low-quality ejaculated spermatozoa bypasses post-testicular sperm DNA damage caused primarily by oxidative stress, thus increasing the likelihood of oocyte fertilization by genomically intact spermatozoa. Despite the overall favorable results, data remain limited, and mainly concern males with confirmed sperm DNA damage in the ejaculate. Additionally, information regarding the health of ICSI offspring resulting from the use of surgically retrieved spermatoa of non-azoospermic males is still lacking. Efforts should be made to improve the male partner's reproductive health for safer ICSI utilization. A comprehensive andrological evaluation aiming to identify and treat the underlying male infertility factor contributing to sperm DNA damage is essential for achieving this goal.
Collapse
Affiliation(s)
- Sandro C Esteves
- ANDROFERT, Andrology and Human Reproduction Clinic, Av. Dr. Heitor Penteado, Campinas, SP, Brazil
- Department of Surgery (Division of Urology), Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas, SP, Brazil
- Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
| | - Igor Coimbra
- Department of Surgery, Division of Urology, University of São Paulo Medical School, São Paulo, SP, Brazil
| | - Jorge Hallak
- Department of Surgery, Division of Urology, University of São Paulo Medical School, São Paulo, SP, Brazil
- Department of Pathology, Reproductive Toxicology Unit, University of São Paulo Medical School, São Paulo, SP, Brazil
- Men's Health Study Group, Institute for Advanced Studies, University of São Paulo, São Paulo, SP, Brazil
- Androscience, Science and Innovation Center in Andrology and High-Complex Clinical and Andrology Research Laboratory, São Paulo, SP, Brazil
| |
Collapse
|
7
|
Aitken RJ. Sperm DNA integrity: a special issue exploring the causes, consequences, and treatment of DNA damage in human spermatozoa. Andrology 2023; 11:1541-1544. [PMID: 37854016 DOI: 10.1111/andr.13503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 07/27/2023] [Indexed: 10/20/2023]
Affiliation(s)
- Robert John Aitken
- Priority Research Centre for Reproductive Science, College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, Australia
- Hunter Medical Research Institute (HMRI), New Lambton, NSW, Australia
| |
Collapse
|
8
|
Alvarez JG, García-Peiró A, Barros A, Ferraz L, Sousa M, Sakkas D. Double strand DNA breaks in sperm: the bad guy in the crowd. J Assist Reprod Genet 2023; 40:745-751. [PMID: 36823317 PMCID: PMC10224897 DOI: 10.1007/s10815-023-02748-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 02/06/2023] [Indexed: 02/25/2023] Open
Abstract
PURPOSE The main objective of this opinion paper was to bring to light and enhance our understanding of the amount of double-strand DNA breaks in sperm and whether there is a threshold of no return when considering repair by the oocyte/embryo. METHODS A brief review of literature related to the theories proposed for the appearance of double-strand breaks in human spermatozoa. Further commentary regarding their detection, how oocytes or embryos may deal with them, and what are the consequences if they are not repaired. Finally, a strategy for dealing with patients who have higher levels of double-strand DNA breaks in sperm is proposed by reviewing and presenting data using testicular extracted sperm. RESULTS We propose a theory that a threshold may exist in the oocyte that allows either complete or partial DNA repair of impaired sperm. The closer that an embryo is exposed to the threshold, the more the effect on the ensuing embryo will fail to reach various milestones, including blastocyst stage, implantation, pregnancy loss, an adverse delivery outcome, or offspring health. We also present a summary of the role that testicular sperm extraction may play in improving outcomes for couples in which the male has a high double-strand DNA break level in his sperm. CONCLUSIONS Double-strand DNA breaks in sperm provide a greater stress on repair mechanisms and challenge the threshold of repair in oocytes. It is therefore imperative that we improve our understanding and diagnostic ability of sperm DNA, and in particular, how double-strand DNA breaks originate and how an oocyte or embryo is able to deal with them.
Collapse
Affiliation(s)
| | - Agustin García-Peiró
- Centro de Infertilidad Masculina y Análisis de Barcelona (CIMAB), Barcelona, Spain
| | - Alberto Barros
- Department of Genetics, Faculty of Medicine, University of Porto, Porto, Portugal
- Centro de Genética da Reprodução Alberto Barros, Porto, Portugal
- Institute for Research and Innovation in Health (i3S), University of Porto, Porto, Portugal
| | - Luís Ferraz
- Department of Urology, Hospital Centre of Vila Nova de Gaia/Espinho, Unit 1, Rua Conceição Fernandes 1079, 4434-502 Vila Nova de Gaia, Portugal
| | - Mário Sousa
- Laboratory of Cell Biology, Department of Microscopy, ICBAS-School of Medicine and Biomedical Sciences, University of Porto, Porto, Portugal
- UMIB-Unit for Multidisciplinary Research in Biomedicine/ITR-Laboratory for Integrative and Translational Research in Population Health, University of Porto, Porto, Portugal
| | | |
Collapse
|