Alterations in bone morphogenetic protein 15, growth differentiation factor 9, and gene expression in granulosa cells in preovulatory follicles of dairy cows given porcine LH

Morphologic, Steroidogenic, and Transcriptomic Assessment of the Corpus Luteum in Holstein Cows after Spontaneous or Hormone-Induced Ovulation

There is evidence that replacing the gonadotropin-releasing hormone (GnRH) with porcine luteinizing hormone (pLH) to synchronize ovulation prior to artificial insemination (AI) increased pregnancy per AI in dairy cows without affecting blood progesterone (P₄) concentrations. Whether morphologic, steroidogenic, and transcriptomic differences exist among corpora lutea (CL) formed after ovulation induced by GnRH and pLH is unclear. Our main objective, therefore, was to compare CL characteristics between GnRH- and pLH-induced CL. In 24 non-lactating Holstein cows, ovulations were spontaneous (Spont-Ov) or induced with 100 µg GnRH, 25 mg pLH, or 1 mg estradiol benzoate (EB), with CL excised 12 d after ovulation. In pLH- versus GnRH-treated cows, the duration of elevated LH (above baseline) was prolonged (10 versus 6 h, respectively, p < 0.01), but CL dimensions, pixel intensity of CL images, proportions of steroidogenic and non-steroidogenic luteal cells, and mean plasma LH did not significantly differ. Post-ovulation mean plasma P₄ (ng/mL) did not differ among Spont-Ov (3.0) pLH (3.1) or GnRH (3.0) cows but were lower in EB cows (2.0). In vitro P₄ concentration was greater in luteal explants of pLH-treated cows than in all other groups (combined means, 16.0 vs. 12.3 µg/mL, p < 0.02). Relative abundance of mRNA for oxytocin receptor (OXTR) was 2-fold higher (p < 0.01) in CL of pLH vs. GnRH cows and highest in Spont-Ov CL. In summary, pLH-treated cows had a longer LH peak, and greatest luteal tissue concentrations and in vitro production of P₄. We inferred that increased P₄ concentrations at the ovarian-uterine level in pLH-treated cows could have promoted embryo development and increased pregnancy per AI.

Conditions to optimise the developmental competence of immature equine oocytes

Optimising the developmental potential of immature equine oocytes and invitro-produced (IVP) embryos was explored through modifications of established media and holding temperature. In Experiment 1, delaying spontaneous resumption of meiosis through the process of simulated physiological oocyte maturation with the addition of the adenylate cyclase activator forskolin (50µM) and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (100µM) to overnight holding medium before maturation improved blastocyst production (P<0.05). In Experiment 2, the blastocyst production rate was increased significantly when cumulin (100ng mL-1) was added to the overnight holding or culture media (P<0.05). In Experiment 3, immature oocytes held overnight at 16°C before maturation had improved developmental competence than those held at 20°C and 5°C (P<0.05). There was no difference between maturation rates, but blastocyst formation per cleaved oocyte was significantly greater in oocytes held overnight at 16°C than at 20°C or 5°C. Furthermore, blastocyst formation per recovered oocyte and per fertilised oocyte was greater when oocytes were held before maturation at 16°C than at 5°C (P<0.05). In Experiment 4, the addition of sodium ascorbate (AC; 50µg mL-1) to the maturation and/or culture media of oocytes and IVP embryos did not improve blastocyst production, but did appear to lower cleavage rates compared with oocytes and embryos cultured without AC.

GDF9-β promotes folliculogenesis in sheep ovarian transplantation onto the chick embryo chorioallantoic membrane (CAM) in cryopreservation programs

PURPOSE

Ovarian tissue (OT) cryopreservation is a treatment option for fertility preservation among young cancer patients. However, the procedure may involve a reduction in the GDF9-β expression and a delay in follicular growth after thawing and transplantation. The aim of this study was to evaluate whether supplementation of GDF9-β can compensate the reduction of this factor during the cryopresevation process and promote folliculogenesis after transplantation of thawed sheep ovarian tissue.

METHODS

Sheep OT was cryopreserved using two methods of vitrification and slow freezing. Fresh and thawed OTs were then transplanted onto chick embryo chorioallantoic membrane (CAM) and then divided into two groups based on the addition of GDF9-β to the grafted tissue. After 5 days of culture, both histological and immunohistological (Ki-67) assessments were performed to evaluate follicular structure, development, and proliferation. The fibrotic and necrotic areas were measured using MICROVISIBLE software.

RESULTS

Folliculogenesis took place in all culture groups, but was significantly improved only in the +GDF9-β cultured group. Also, better follicular structure was preserved in the aforementioned group (p < 0.05). When GDF9-β was supplemented to the culture medium, more neovascularization (p < 0.05) and better transplantation (p > 0.05) was observed. Furthermore, the areas of fibrosis and necrosis were lower in this group rather than the controls. Follicular proliferative activity was significantly higher only in the slow freezing +GDF9-β cultured group.

CONCLUSIONS

GDF9-β, as a stimulatory factor, not only promoted the folliculogenesis in the fresh ovarian transplant, but also compensated for its reduction during the cryopreservation process.

Molecular Aspects and Clinical Relevance of GDF9 and BMP15 in Ovarian Function

Growth and differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) are oocyte-secreted factors with a leading role in the control of ovarian function in female reproduction, modulating both the cell fate of the somatic granulosa cells and the quality and developmental competence of the egg. This short review aims to consolidate the molecular aspects of GDF9 and BMP15 and their integral actions in female fertility to understand particularly their effects on oocyte quality and fetal growth. The significant consequences of mutations in the GDF9 and BMP15 genes in women with dizygotic twins as well as the clinical relevance of these oocyte factors in the pathogenesis of primary ovarian insufficiency and polycystic ovary syndrome are also addressed.

Molecular forms of ruminant BMP15 and GDF9 and putative interactions with receptors

Bone morphogenetic factor 15 (BMP15) and growth differentiation factor 9 (GDF9) are oocyte-secreted factors with demonstrable effects on ovarian follicular development and ovulation rate. However, the molecular forms of BMP15 and GDF9 produced by oocytes remain unclear. The aims herein, using Western blotting (WB) procedures with specific monoclonal antibodies (mabs), were to identify the molecular forms of BMP15 and GDF9 synthesised and secreted by isolated ovine (o) and bovine (b) oocytes in vitro The mabs were known to recognise the biological forms of BMP15 or GDF9 since they had previously been shown to inhibit their bioactivities in vitro and in vivo Using recombinant variants of oBMP15 and oGDF9, including a cysteine mutant form of oBMP15 (S356C) and a human (h) BMP15:GDF9 heterodimer (cumulin), it was established that the mabs were able to identify monomeric, dimeric, promature and higher-molecular-weight forms of BMP15 and GDF9 and cumulin (GDF9 mab only). After using non-reducing, reducing and reducing + cross-linking conditions, the major oocyte-secreted forms of o and b BMP15 and GDF9 were the cleaved and uncleaved monomeric forms of the promature proteins. There was no evidence for dimeric or heterodimeric forms of either mature BMP15 or GDF9. From in silico modelling studies using transforming growth factor beta (TGFB), activin or BMP crystal templates, and both present and previously published data, a model is proposed to illustrate how the monomeric forms of BMP15 and GDF9 may interact with their type II and type I cell-surface receptors to initiate the synergistic actions of these growth factors.