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Gong JG, Campbell BK, Webb R. Defining the gonadotrophin requirement for the selection of a single dominant follicle in cattle. Reprod Fertil Dev 2021; 32:322-334. [PMID: 31656220 DOI: 10.1071/rd19060] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Accepted: 07/31/2019] [Indexed: 11/23/2022] Open
Abstract
The aim was to define the pattern and physiological concentrations of FSH and LH required for the selection of a single dominant follicle in mono-ovulatory species. A series of five experiments was carried out using gonadotrophin-releasing hormone agonist-induced hypogonadal heifers. Animals were infused with different patterns of either FSH and/or LH followed by an ovulatory dose of human chorionic gonadotrophin. Follicular response was monitored by ultrasound scanning and blood samples were collected to measure concentrations of FSH, LH, oestradiol and progesterone. The main findings were: (1) physiological concentrations of FSH given as a continuous infusion and for an adequate duration, in the presence of basal LH, with or without LH pulses, are capable of inducing a superovulatory response, (2) initial exposure to FSH followed by LH pulses alone stimulate the development of multiple preovulatory follicles, confirming that ovarian follicles are capable of transferring dependence on gonadotrophins from FSH to LH, (3) while LH pulses appear not to have a major effect on the pattern of preovulatory follicle development, adequate LH pulsatile support is required for full oestradiol synthesis and (4) the duration of initial exposure to FSH and the ability to transfer the dependence from FSH to LH are critical for the selection of a single dominant follicle. In conclusion, this experimental series confirms that the duration of initial exposure to FSH and the ability of the selected follicle to transfer its gonadotrophic dependence from FSH to LH are critical for the selection of a single dominant follicle in cattle.
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Affiliation(s)
- Jin G Gong
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, United Kingdom
| | - Bruce K Campbell
- School of Human Development, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom
| | - Robert Webb
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire LE12 5RD, United Kingdom; and Corresponding author.
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2
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Dias HP, Poole RK, Albuquerque JP, Dos Santos PH, Castilho ACS, Pohler KG, Vasconcelos JLM. Progesterone dose during synchronization treatment alters luteinizing hormone receptor and steroidogenic enzyme mRNA abundances in granulosa cells of Nellore heifers. Anim Reprod Sci 2020; 225:106681. [PMID: 33421819 DOI: 10.1016/j.anireprosci.2020.106681] [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: 06/11/2020] [Revised: 12/13/2020] [Accepted: 12/14/2020] [Indexed: 10/22/2022]
Abstract
The objective was to investigate effects of progesterone (P4) dose on abundance of luteinizing hormone receptor (LHCGR), aromatase (CYP19A1), 3β-hydroxysteroid dehydrogenase (HSD3B1), and other steroidogenic mRNA transcripts in granulosa cells from dominant follicles. Nellore heifers were assigned to one of six groups: new, first-use controlled internal drug release device (CIDR1) inserted for 5 days (Large-P4-dose-D5; n = 7) or 6 days (Large-P4-dose-D6; n = 8), prostaglandin (PG)F2α administered on D0 and 1 previously-used CIDR (CIDR3) inserted for 5 days (Small- P4-dose-D5; n = 8) or 6 days (Small-P4-dose-D6; n = 8), CIDR1 inserted on D0 and removed plus PGF2α on D5 (Large-P4-dose-proestrus (PE); n = 7), and CIDR3 and PGF2α on D0 and 1, CIDR3 removed plus PGF2α on D5 (Small-P4-dose-PE; n = 7). Duration of P4 treatment (D5 compared to D6) affected abundances of CYP19A1 mRNA transcripts, with there being greater abundances on D6 than D5 (P ≤ 0.05). Heifers treated with the large dose of P4 had a smaller dominant follicle, less serum and intra-follicular estradiol (E2) concentrations (P ≤ 0.05) and lesser LHCGR, CYP19A1, and HSD3B1 transcript abundances (P ≤ 0.05). Heifers treated to induce PE had a larger follicle diameter (P = 0.09), greater intra-follicular E2 concentrations and larger abundances of CYP19A1 mRNA transcript (P ≤ 0.05) than heifers of the D6 group. Overall, treatment with larger doses of P4 resulted in lesser abundances of LHCGR, HSD3B1, and CYP19A1 mRNA transcripts; thus, potentially leading to development of smaller dominant follicles and lesser E2 concentrations.
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Affiliation(s)
- H P Dias
- Department of Animal Production, São Paulo State University, Botucatu, 18168-000, Brazil
| | - R K Poole
- Department of Animal Science, Pregnancy and Developmental Programming Area of Excellence, Texas A&M University, College Station, TX, 77843, USA
| | - J P Albuquerque
- Department of Animal Production, São Paulo State University, Botucatu, 18168-000, Brazil
| | - P H Dos Santos
- Institue of Biosciences, São Paulo State University, Botucatu, 18168-000, Brazil
| | - A C S Castilho
- University of Western São Paulo, Presidente Prudente, Brazil
| | - K G Pohler
- Department of Animal Science, Pregnancy and Developmental Programming Area of Excellence, Texas A&M University, College Station, TX, 77843, USA.
| | - J L M Vasconcelos
- Department of Animal Production, São Paulo State University, Botucatu, 18168-000, Brazil.
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3
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Gomez-León VE, Andrade JP, Kirkpatrick BW, Moghbeli SM, García-Guerra A, Ginther OJ, Wiltbank MC. Selection of fewer dominant follicles in Trio carriers given GnRH antagonist and luteinizing hormone action replaced by nonpulsatile human chorionic gonadotropin†. Biol Reprod 2020; 103:1217-1228. [PMID: 32940667 DOI: 10.1093/biolre/ioaa167] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 09/03/2020] [Accepted: 09/07/2020] [Indexed: 12/11/2022] Open
Abstract
Studying selection of multiple dominant follicles (DFs) in monovulatory species can advance our understanding of mechanisms regulating selection of single or multiple DFs. Carriers of the bovine high fecundity Trio allele select multiple DFs, whereas half-sib noncarriers select a single DF. This study compared follicle selection during endogenous gonadotropin pulses versus during ablation of pulses with Acyline (GnRH antagonist) and luteinizing hormone (LH) action replaced with nonpulsatile human chorionic gonadotropin (hCG) treatment in Trio carriers (n = 28) versus noncarriers (n = 32). On Day 1.5 (Day 0 = ovulation), heifers were randomized: (1) Control, untreated; (2) Acyline, two i.m. doses (Days 1.5 and D3) of 3 μg/kg; (3) hCG, single i.m. dose of 50 IU hCG on Day 1.5 followed by daily doses of 100 IU; and (4) Acyline + hCG. Treatments with nonpulsatile hCG were designed to replace LH action in heifers treated with Acyline. Acyline treatment resulted in cessation of follicle growth on Day 3 with smaller (P < 0.0001) maximum follicle diameter in Trio carriers (6.6 ± 0.2 mm) than noncarriers (8.7 ± 0.4 mm). Replacement of LH action (hCG) reestablished follicle diameter deviation and maximum diameter of DFs in both genotypes (8.9 ± 0.3 mm and 13.1 ± 0.5 mm; P < 0.0001). Circulating follicle stimulating hormone (FSH) was greater in Acyline-treated than in controls. Finally, Acyline + hCG decreased (P < 0.0001) the number of DFs from 2.7 ± 0.2 to 1.3 ± 0.2 in Trio carriers, with most heifers having only one DF. This demonstrates the necessity for LH in acquisition of dominance in Trio carriers (~6.5 mm) and noncarriers (~8.5 mm) and provides evidence for a role of GnRH-induced FSH/LH pulses in selection of multiple DFs in Trio carriers and possibly other physiologic situations with increased ovulation rate.
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Affiliation(s)
- Victor E Gomez-León
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, USA.,Eutheria Foundation, Cross Plains, WI, USA
| | - João Paulo Andrade
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, USA
| | - Brian W Kirkpatrick
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, USA
| | | | | | - O J Ginther
- Eutheria Foundation, Cross Plains, WI, USA.,Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA
| | - Milo C Wiltbank
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, USA
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4
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Cheong SH, Fortune JE, Allen JJ, Butler WR, Gilbert RO. Androgen production in response to LH is impaired in theca cells from nonovulatory dominant follicles in early-postpartum dairy cows. Domest Anim Endocrinol 2020; 71:106385. [PMID: 31726391 DOI: 10.1016/j.domaniend.2019.106385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 07/27/2019] [Accepted: 08/03/2019] [Indexed: 11/29/2022]
Abstract
Most dairy cows develop a dominant follicle within two weeks postpartum, but 60% of these follicles fail to ovulate. In a previous study, we determined that cows destined to ovulate have higher LH pulse frequency and circulating estradiol. The latter characteristic provided a method for distinguishing ovulatory from nonovulatory follicles during development and we found that nonovulatory follicles have lower estradiol and androstenedione in their follicular fluid. We hypothesized that lower LH pulse frequency impairs androgen production by theca cells of nonovulatory cows, reducing their ability to make estradiol. In the present study, we applied our method for predicting follicle fate to collect dominant follicles from predicted ovulatory (n = 7) and nonovulatory (n = 3) follicles. Theca and granulosa cells were separated and cultured in the absence or presence of LH, FSH, and/or testosterone for three days, with daily collection of culture medium for steroid RIAs. Estradiol and progesterone production by granulosa cells were not different between ovulatory and nonovulatory follicles. By contrast, overall androstenedione production by theca cells from ovulatory follicles was significantly higher compared with nonovulatory follicles on all three days of culture and, as culture progressed, theca from nonovulatory follicles had increasingly poorer responses to LH. In the same cultures, the progesterone production by theca cells was similar in ovulatory and nonovulatory groups. In support of our hypothesis, the results show that estradiol production by granulosa cells from nonovulatory follicles is robust when androgen substrate is present, but that thecal androgen production in response to LH is impaired. This suggests that the initial defect in steroidogenesis in dominant follicles that fail to ovulate postpartum is lower production of androgen by theca cells.
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Affiliation(s)
- S H Cheong
- Department of Clinical Sciences, Cornell University, Ithaca, NY, USA.
| | - J E Fortune
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
| | - J J Allen
- Department of Animal Science, Cornell University, Ithaca, NY, USA
| | - W R Butler
- Department of Animal Science, Cornell University, Ithaca, NY, USA
| | - R O Gilbert
- Department of Clinical Sciences, Cornell University, Ithaca, NY, USA.
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5
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Marsters P, Kendall NR, Campbell BK. Pre-translational regulation of luteinizing hormone receptor in follicular somatic cells of cattle. Anim Reprod Sci 2015; 163:63-74. [PMID: 26507944 PMCID: PMC4679792 DOI: 10.1016/j.anireprosci.2015.09.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 09/28/2015] [Accepted: 09/30/2015] [Indexed: 11/29/2022]
Abstract
Differential regulation of LHR in theca cells (TC) and granulosa cells (GC) is important for normal follicular development. Unlike TC, GC only acquire LH-responsiveness during the later stages of antral follicle development. This study tested the hypothesis that differential LH-responsiveness in these two cell types may be due, in part, to shifts in cellular patterns of alternatively spliced LHR mRNA transcripts which may not be obvious from analysis of total LHR gene expression. It also further explored the role of translation inhibition by an LHR binding protein (LHBP), normally associated with the production of endogenous cholesterol. LHR mRNA variation arises as a result of the alternative splicing of two variable deletion sites (VDS) designated 5′ VDS and 3′ VDS, and it was proposed that differences in cell sensitivity to LH may be due in part to variations in the pattern of the mRNA expression of the receptor variants. The outcomes of the present study support a dynamic multi-facetted regulation of LHR during pre-translation. Not only did the ratio between variants change during antral follicle growth and in vitro cell differentiation but also between TC and GC. Regulation could also be linked to LH concentration feedback mechanisms as the absence of LH caused cultured TC to markedly up-regulate amounts of LHR mRNA. In both TC and GC, LHR mRNA was greatly reduced after treatment to block mevalonate production in the de novo cholesterol pathway, adding further support for a regulatory mechanism linked to enriched cellular amounts of mevalonate kinase.
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Affiliation(s)
- P Marsters
- University of Nottingham, Division of Child Health, Obstetrics and Gynaecology, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom.
| | - N R Kendall
- School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Leicestershire LE12 5RD, United Kingdom
| | - B K Campbell
- University of Nottingham, Division of Child Health, Obstetrics and Gynaecology, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom
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6
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Regan SLP, McFarlane JR, O'Shea T, Andronicos N, Arfuso F, Dharmarajan A, Almahbobi G. Flow cytometric analysis of FSHR, BMRR1B, LHR and apoptosis in granulosa cells and ovulation rate in merino sheep. Reproduction 2015; 150:151-63. [DOI: 10.1530/rep-14-0581] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 05/05/2015] [Indexed: 11/08/2022]
Abstract
The aim of the present study was to determine the direct cause of the mutation-induced, increased ovulation rate in Booroola Merino (BB) sheep. Granulosa cells were removed from antral follicles before ovulation and post-ovulation from BB (n=5) and WT (n=12) Merino ewes. Direct immunofluorescence measurement of mature cell surface receptors using flow cytometry demonstrated a significant up-regulation of FSH receptor (FSHR), transforming growth factor beta type 1, bone morphogenetic protein receptor (BMPR1B), and LH receptor (LHR) in BB sheep. The increased density of FSHR and LHR provide novel evidence of a mechanism for increasing the number of follicles that are recruited during dominant follicle selection. The compounding increase in receptors with increasing follicle size maintained the multiple follicles and reduced the apoptosis, which contributed to a high ovulation rate in BB sheep. In addition, we report a mutation-independent mechanism of down-regulation to reduce receptor density of the leading dominant follicle in sheep. The suppression of receptor density coincides with the cessation of mitogenic growth and steroidogenic differentiation as part of the luteinization of the follicle. The BB mutation-induced attenuation of BMPR1B signaling led to an increased density of the FSHR and LHR and a concurrent reduction in apoptosis to increase the ovulation rate. The role of BMPs in receptor modulation is implicated in the development of multiple ovulations.
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7
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Wei S, Chen S, Gong Z, Ouyang X, An L, Xie K, Dong J, Wei M. Alarelin active immunization influences expression levels of GnRHR, FSHR and LHR proteins in the ovary and enhances follicular development in ewes. Anim Sci J 2013; 84:466-75. [PMID: 23607296 DOI: 10.1111/asj.12030] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 10/14/2012] [Indexed: 11/27/2022]
Abstract
We investigated the effects of gonadotropin releasing hormone (GnRH) agonist on expressions of GnRH receptor (GnRHR), follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) proteins in the ovaries and follicular development in the ewes. Forty-two pre-pubertal ewes were assigned to experimental groups 1 to 5 (EG-I to EG-V) and control group (CG). Ewes in EG-I, EG-II and EG-III were subcutaneously injected with 200, 300 or 400 μg alarelin antigens twice (on days 0 and 14), respectively. Ewes in EG-IV and EG-V were subcutaneously injected with 200 μg and 300 μg alarelin antigen four times (on days 0, 7, 14 and 21). Ewes in CG were subcutaneously injected with a solvent twice (on days 0 and 14). Serum concentrations of GnRH antibody in the EGs increased and were higher than (P<0.05) that of CG from day 14 to day 60. GnRH antibody concentrations in EG-IV and EG-V were higher than that in EG-I, EG-II and EG-III from days 35 to 45. Expressions of GnRHR protein in EG-IV and EG-V were lower than that in CG (P<0. 01). Expressions of FSHR and LHR proteins in EGs increased. Levels of FSHR and LHR proteins in EG-IV and EG-V (P<0.05) were higher than CG. Ovarian weights in EGs increased. Values of follicle vertical diameter, follicle transverse diameter, follicle wall thickness, follicle externatheca thickness and follicle internatheca thickness in EG-III and EG-V were greater than other groups. Primordial follicles and primary follicles developed quickly in alarelin-immunized animals. Secondary follicles and mature follicles became more abundant. Mitochondria, mitochondrial cristaes and cortical granules increased. Serum FSH concentrations of EGs remained higher than that in CG from days 28 to 70 (P<0.05). Alarelin immunization stimulated GnRH antibody production, suppressed expression of GnRHR protein, enhanced expressions of FSHR and LHR proteins in ovaries, promoted FSH secretion and thereby accelerated the development of ovaries and follicles in ewes.
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Affiliation(s)
- Suocheng Wei
- College of Life Science and Engineering, Northwest University for Nationalities, Lanzhou, China.
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8
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GnRH agonist active immunization influences ovarian development and GnRH receptor mRNA expression levels of pituitary in Japanese white rabbits (Oryctolagus cuniculus). Livest Sci 2011. [DOI: 10.1016/j.livsci.2011.01.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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9
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Sales J, Crepaldi G, Girotto R, Souza A, Baruselli P. Fixed-time AI protocols replacing eCG with a single dose of FSH were less effective in stimulating follicular growth, ovulation, and fertility in suckled-anestrus Nelore beef cows. Anim Reprod Sci 2011; 124:12-8. [DOI: 10.1016/j.anireprosci.2011.02.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 01/19/2011] [Accepted: 02/07/2011] [Indexed: 11/15/2022]
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10
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Buratini J, Price CA. Follicular somatic cell factors and follicle development. Reprod Fertil Dev 2011; 23:32-9. [DOI: 10.1071/rd10224] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Considerable attention is currently paid to oocyte-derived secreted factors that act upon cumulus and granulosa cells. Also important for follicle development are somatic cell-derived secreted factors. This is illustrated by the ability of granulosa cell-derived Kit ligand (KITL) to promote primordial follicle activation, and the loss of follicle development that accompanies KITL gene disruption. This review summarises our current understanding of somatic cell factors during both preantral and antral follicle growth, involving not only signalling from granulosa cells to the oocyte, but also signalling between granulosa and theca cells. Principal granulosa cell-derived factors include activin, anti-Müllerian hormone (AMH), bone morphogenetic proteins (BMPs) and fibroblast growth factors (FGFs). Theca cells also secrete BMPs and FGFs. The interplay between these factors is equally important for follicle growth as the activity of oocyte-derived factors.
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Irving-Rodgers HF, Harland ML, Sullivan TR, Rodgers RJ. Studies of granulosa cell maturation in dominant and subordinate bovine follicles: novel extracellular matrix focimatrix is co-ordinately regulated with cholesterol side-chain cleavage CYP11A1. Reproduction 2009; 137:825-34. [PMID: 19261832 DOI: 10.1530/rep-08-0485] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
During growth of antral ovarian follicles granulosa cells first become associated with a novel type of extracellular matrix, focimatrix, and at larger sizes follicles become either subordinate or dominant. To examine this, bovine subordinate (9.0+/-S.E.M. 0.4 mm; n=16), partially dominant (12.0+/-0.6 mm; n=18) and fully dominant (15.0+/-0.4 mm; n=14) follicles were examined by real time RT-PCR analyses of granulosa cells and by immunohistochemistry of focimatrix. Changes in the expression of FSH receptor, LH receptor, cholesterol side-chain cleavage (CYP11A1), 3beta-hydroxysteroid dehydrogenase, aromatase (CYP19A1) and inhibin-alpha and beta-B were observed as expected for follicle sizes examined. After adjusting for size differences, only CYP11A1 was significantly different between the groups, and elevated in dominant follicles. Also after adjusting for differences in size there were no significant differences in expression of focimatrix components collagen type IV alpha-1 (COL4A1), laminin beta-2, nidogen 1 (NID1), and perlecan (HSPG2) or the volume density of NID1 and -2 and HSPG2. The volume density of focimatrix components in laminin 111 was significantly elevated in dominant follicles. Adjusting for analysis of more than one follicle per animal and for multiple correlations, CYP11A1 mRNA levels were highly correlated with the focimatrix genes COL4A1, NID1 and -2 and HSPG2. Thus, focimatrix may potentially regulate CYP11A1 expression, and the regulation of both could be important in follicular dominance.
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Affiliation(s)
- H F Irving-Rodgers
- Research Centre for Reproductive Health, Discipline of Obstetrics, University of Adelaide, Adelaide, South Australia 5005, Australia
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12
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Hayashi KG, Matsui M, Shimizu T, Sudo N, Sato A, Shirasuna K, Tetsuka M, Kida K, Schams D, Miyamoto A. The absence of corpus luteum formation alters the endocrine profile and affects follicular development during the first follicular wave in cattle. Reproduction 2008; 136:787-97. [DOI: 10.1530/rep-07-0480] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We previously established a bovine experimental model showing that the corpus luteum (CL) does not appear following aspiration of the preovulatory follicle before the onset of LH surge. Using this model, the present study aimed to determine the profile of follicular development and the endocrinological environment in the absence of CL with variable nadir circulating progesterone (P4) concentrations during the oestrous cycle in cattle. Luteolysis was induced in heifers and cows and they were assigned either to have the dominant follicle aspirated (CL-absent) or ovulation induced (CL-present). Ultrasound scanning to observe the diameter of each follicle and blood collection was performed from the day of follicular aspiration or ovulation and continued for 6 days. The CL-absent cattle maintained nadir circulating P4throughout the experimental period and showed a similar diameter between the largest and second largest follicle, resulting in co-dominant follicles. Oestradiol (E2) concentrations were greater in the CL-absent cows than in the CL-present cows at day −1, day 1 and day 2 from follicular deviation. The CL-absent cows had a higher basal concentration, area under the curve (AUC), pulse amplitude and pulse frequency of LH than the CL-present cows. After follicular deviation, the CL-absent cows showed a greater basal concentration, AUC and pulse amplitude of growth hormone (GH) than the CL-present cows. These results suggest that the absence of CL accompanying nadir circulating P4induces an enhancement of LH pulses, which involves the growth of the co-dominant follicles. Our results also suggest that circulating levels of P4and E2affect pulsatile GH secretion in cattle.
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13
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Abstract
Central roles in reproductive biology (i.e., growth and development of the oocyte, steroidogenesis, and ovulation) are played by the ovarian dominant follicle (DF). The DF is different from other follicles because it can escape atresia (the fate of all other follicles), and if exposed to the LH surge, its cells will differentiate into the corpus luteum. The DF was originally studied by looking at the surface of ovary through a surgical approach. Current studies employ a less-invasive ultrasound technique to track the growth and development of the DF. Recruitment and selection, the processes that give rise to the DF, and dominance, the physiological state of the mature DF, are important areas of basic research. Results of these basic studies are easily translated into real-world problems in farm animal reproduction. Superovulation, for example, overrides the selection mechanism and increases the number of ovulations. Understanding the factors that affect the size of the recruited pool should increase success rates (i.e., number of collected embryos) for superovulation. In most animals, the DF is short-lived, existing for long enough to allow for the final maturation of the oocyte. Some DF become atretic because they mature during the luteal phase and are never exposed to the LH surge. For other DF, the LH surge redirects the DF toward its ultimate demise (i.e., luteinization, ovulation, and differentiation into the corpus luteum). The DF is managed pharmacologically within protocols for timed AI. When timed AI fails, there may be abnormal corpus luteum development and early embryonic loss; outcomes that are secondary to inadequate follicular cell maturation and incomplete oocyte capacitation in the DF. Future work on the DF will clarify its underlying biological functions so that a variety of needs in farm animal reproduction can be efficiently managed.
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Affiliation(s)
- M C Lucy
- Department of Animal Sciences, University of Missouri, Columbia 65211
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14
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Schneider F, Tomek W, Gründker C. Gonadotropin-releasing hormone (GnRH) and its natural analogues: a review. Theriogenology 2006; 66:691-709. [PMID: 16650469 DOI: 10.1016/j.theriogenology.2006.03.025] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Revised: 01/20/2006] [Accepted: 03/17/2006] [Indexed: 11/29/2022]
Abstract
The pivotal role of gonadotropin-releasing hormone (GnRH) during the hormonal regulation of reproductive processes is indisputable. Likewise, many factors are known to affect reproductive function by influencing either GnRH release from hypothalamus or pituitary gland responsiveness to GnRH. In veterinary medicine, GnRH and its agonists (GnRHa) are widely used to overcome reduced fertility by ovarian dysfunction, to induce ovulation, and to improve conception rate. GnRHa are, moreover, integrative part of other pro-fertility treatments, e.g. for synchronization of the estrous cycle or stimulation for embryo transfer. Additionally, continuous GnRH which shows desensitizing effects of the pituitary-ovarian axis has been recommended for implementation in anti-fertility treatments like inhibition of ovulation or reversible blockade of the estrous cycle. Just as much, another group of GnRH analogues, antagonists, are now in principle disposable for use. For a few decades, GnRH was thought to be a unique structure with a primary role in regulation gonadotropins. However, it became apparent that other homologous ligands of the GnRH receptor (GnRHR) exist. In the meantime, more than 20 natural variants of the mammalian GnRH have been identified in different species which may compete for binding and/or have their own receptors. These GnRH forms (GnRHs) have apparently common and divergent functions. More studies on GnRHs should contribute to a better understanding of reproductive processes in mammals and interactions between reproduction and other physiological functions. Increased information on GnRHs might raise expectations in the application of these peptides in veterinary practice. It is the aim of this review to discuss latest results from evolutionarily based studies as well as first experimental tests and to answer the question how realistic might be the efforts to develop effective and animal friendly practical applications for endogenous GnRHs and synthetic analogues.
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Affiliation(s)
- Falk Schneider
- Department of Reproductive Biology, Research Institute for the Biology of Farm Animals, Wilhelm-Stahl-Allee 2, D-18196 Dummerstorf, Germany.
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15
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Schneider F, Heleil B, Alm H, Torner H, Becker F, Viergutz T, Nürnberg G, Kanitz W. Endocrine, morphological, and cytological effects of a depot GnRH agonist in bovine. Anim Reprod Sci 2006; 92:9-28. [PMID: 15990256 DOI: 10.1016/j.anireprosci.2005.05.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2005] [Revised: 05/13/2005] [Accepted: 05/23/2005] [Indexed: 11/18/2022]
Abstract
The present study was conducted to assess effects of the gonadotropin-releasing hormone agonist (GnRHa) triptorelin in dairy heifers. The peptide was released from a commercial 4-week depot formulation (Decapeptyl Depot) administered at animals' estrus (day 0). First experiment (EXP I, n=5), which was aimed to explore the availability of peptide, detected a maximum of triptorelin concentration between day 2 and 5 after depot injection, and the peptide remained detectable by RIA in peripheral blood for about 3 weeks. In further experiments, the peptide release was terminated on day 9 (EXP II, n=16) or day 21 (EXP III, n=47). Treatment effects were studied on follicular development, the characteristics of cumulus-oocyte complexes (COCs) (EXP II; EXP IIIa) and secretions of LH and progesterone (EXP IIIb). Results showed that the occurrence of the pre-ovulatory LH surge was more uniform in treated heifers than that in controls. The duration of ovulation periods was similar amongst the heifers of EXP II, but more compact amongst those of EXP III each compared with the respective controls. Post-ovulatory, the number of LH pulses was significantly reduced by treatment, whereas both basal LH and progesterone concentrations were elevated on a few days. Follicular growth was reduced only by the prolonged influence of the GnRHa. There were increased proportions of both degenerated COCs and immature oocytes from small follicles (<3mm in diameter), and meiotic configuration and quality of oocytes isolated from follicles 3-5mm were changed after the prolonged, 21-day treatment. These results indicate that a continuous influence of a GnRHa over more than 1 week may increasingly impair the development of bovine follicles and oocytes. This may have some significance for the development of novel GnRH-based techniques in regulating the reproductive function in cattle.
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Affiliation(s)
- F Schneider
- Unit of Reproductive Biology, Research Institute for the Biology of Farm Animals, Wilhelm-Stahl-Allee 2, D-18196 Dummerstorf, Germany.
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Affiliation(s)
- Grant S Frazer
- College of Veterinary Medicine, The Ohio State University, A100 Sisson Hall, 1920 Coffey Road, Columbus, OH 43210, USA.
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Fortune JE, Rivera GM, Yang MY. Follicular development: the role of the follicular microenvironment in selection of the dominant follicle. Anim Reprod Sci 2004; 82-83:109-26. [PMID: 15271447 DOI: 10.1016/j.anireprosci.2004.04.031] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The importance of endocrine signals in the regulation of follicular development has long been recognized. However, the follicular microenvironment also plays a critical role in determining follicular fate. This review summarizes our studies on the role of the intrafollicular IGF system in selection of the dominant follicle (DF) in cattle. During the bovine estrous cycle, the largest antral follicles develop in two or three successive waves of follicular recruitment and selection of a DF. High concentrations of estradiol in the follicular fluid are the hallmark of dominant and preovulatory follicles and are associated with lower concentrations of low molecular weight (MW) insulin-like growth factor binding proteins (IGFBP-2, -4, and -5), which can prevent binding of IGF to its receptor. Our studies have shown that dominant and preovulatory follicles also have much higher levels of an IGFBP-4/-5 protease activity, which is the bovine equivalent of the human IGFBP-4 protease, pregnancy-associated plasma protein-A (PAPP-A). Studies of follicles isolated just after the emergence of the DF showed that PAPP-A is present in the follicular fluid of the DF as soon as it can be detected as morphologically dominant. To examine whether higher levels of PAPP-A in one follicle of the cohort (the future DF) precedes morphological dominance, the four largest follicles were isolated from pairs of bovine ovaries obtained before one follicle of the cohort was significantly larger the others, around the time that one follicle was first detected as morphologically dominant and after dominance was well established. Analysis of the temporal sequence of changes in estradiol, low MW IGFBPs, free IGF, and PAPP-A in the follicular fluid suggested that an increase in PAPP-A is the earliest biochemical difference yet detected in the future DF and that follicular selection is the result of a progressive series of changes beginning with the acquisition of PAPP-A, which leads to a decrease in IGFBP-4 and -5 and an increase in free IGF, which synergizes with FSH to increase estradiol production. Co-dominant follicles, induced by injection of small doses of recombinant bovine (rb) FSH, both had levels of PAPP-A similar to the single DF of control heifers, supporting the hypothesized role of FSH in the induction of PAPP-A in the DF. Taken together, these results suggest a critical role for FSH-induced PAPP-A, and thus for free IGF, in the selection of the DF. In contrast, other experiments provided evidence for a deleterious effect of IGF on the initiation of bovine follicular growth and the survival of primordial and primary follicles in vitro. These results underscore the importance of the follicular microenvironment in determining follicular fate and indicate that its effects can be stage-specific.
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Affiliation(s)
- J E Fortune
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
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