Expression of bone morphogenetic proteins and receptors in porcine cumulus-oocyte complexes during in vitro maturation

Supplementation with fibroblast growth factor 7 during in vitro maturation of porcine cumulus-oocyte complexes improves oocyte maturation and early embryonic development

In vitro generation of porcine embryos is an indispensable method in the realms of both agriculture and biomedicine. Nonetheless, the extant procedures encounter substantial obstacles pertaining to both the caliber and efficacy of the produced embryos, necessitating extensive research to in vitro maturation (IVM), the seminal commencement phase. One potentially fruitful approach may lie in refining the media and supplements composition utilized for oocyte maturation. Fibroblast growth factor-7 (FGF7), alternatively termed keratinocyte growth factor, is a theca-derived cytokine integral to folliculogenesis. This study aimed to examine the ramifications of supplementing FGF7 during the IVM phase. To determine the FGF7 location and its receptor in porcine ovaries, immunohistochemistry was executed based on follicle size categories (1-2, 3-6, and 7-9 mm). Regardless of follicle size, it was determined that FGF7 was expressed in theca and granulosa cells (GCs), whereas the FGF7 receptor was only expressed in the GCs of the larger follicles. During the IVM process, the maturation medium was supplied with various concentrations of FGF7, aiming to mature porcine cumulus-oocyte complexes (COCs). The data indicated a significant augmentation in the nuclear maturation rate only within the group treated with 10 ng/mL of FGF7 (p < 0.05). Post-IVM, the oocytes diameter exhibited a significant expansion in all groups that received FGF7 supplementation (p < 0.05). Additionally, all FGF7-supplemented groups exhibited a substantial elevation in intracellular glutathione levels, coupled with a noticeable reduction in reactive oxygen species levels (p < 0.05). With respect to gene expressions related to apoptosis, FGF7 treatment elicited a downregulation of pro-apoptotic genes and an upregulation of anti-apoptotic genes. The expression of genes associated with antioxidants underwent a significant enhancement (p < 0.05). In terms of the FGF7 signaling pathway-associated genes, there was a significant elevation in the mRNA expression of ERK1, ERK2, c-kit, and KITLG (p < 0.05). Remarkably, the group of 10 ng/mL of FGF7 demonstrated an appreciable uptick in the blastocyst formation rate during embryonic development post-parthenogenetic activation (p < 0.05). In conclusion, the FGF7 supplementation during IVM substantially augments the quality of matured oocytes and facilitates the subsequent development of parthenogenetically activated embryos. These results offer fresh perspectives on improved maturation and following in vitro evolution of porcine oocytes.

Expression Patterns and Gonadotropin Regulation of the TGF-β II Receptor (Bmpr2) during Ovarian Development in the Ricefield Eel Monopterus albus

Bmpr2 plays a central role in the regulation of reproductive development in mammals, but its role during ovarian development in fish is still unclear. To ascertain the function of bmpr2 in ovarian development in the ricefield eel, we isolated and characterized the bmpr2 cDNA sequence; the localization of Bmpr2 protein was determined by immunohistochemical staining; and the expression patterns of bmpr2 in ovarian tissue incubated with FSH and hCG in vitro were analyzed. The full-length bmpr2 cDNA was 3311 bp, with 1061 amino acids encoded. Compared to other tissues, bmpr2 was abundantly expressed in the ovary and highly expressed in the early yolk accumulation (EV) stages of the ovary. In addition, a positive signal for Bmpr2 was detected in the cytoplasm of oocytes in primary growth (PG) and EV stages. In vitro, the expression level of gdf9, the ligand of bmpr2, in the 10 ng/mL FSH treatment group was significantly higher after incubation for 4 h than after incubation for different durations. However, bmpr2 expression in the 10 ng/mL FSH treatment group at 2 h, 4 h and 10 h was significantly lower. Importantly, the expression level of bmpr2 and gdf9 in the 100 IU/mL hCG group had similar changes that were significantly decreased at 4 h and 10 h. In summary, Bmpr2 might play a pivotal role in ovarian growth in the ricefield eel, and these results provide a better understanding of the function of bmpr2 in ovarian development and the basic data for further exploration of the regulatory mechanism of gdf9 in oocyte development.

Ovarian Transcriptomic Analysis of Ninghai Indigenous Chickens at Different Egg-Laying Periods

Egg production is an essential indicator of poultry fertility. The ovary is a crucial organ involved in egg production; however, little is known about the key genes and signaling pathways involved in the whole egg-laying cycle of hens. In order to explore the mechanism of egg production at different stages of the egg-laying process, ovarian tissues from four chickens were randomly selected for transcriptome analysis at each of the three ages (145 d, 204 d, and 300 d in the early, peak, and late stages of egg laying). A total of 12 gene libraries were constructed, and a total of 8433 differential genes were identified from NH145d vs. NH204d, NH145d vs. NH300d and NH300d vs. NH204d (Ninghai 145-day-old, Ninghai 204-day-old, and Ninghai 300-day-old), with 1176, 1653 and 1868 up-regulated genes, and 621, 1955 and 1160 down-regulated genes, respectively. In each of the two comparison groups, 73, 1004, and 1030 differentially expressed genes were found to be co-expressed. We analyzed the differentially expressed genes and predicted nine genes involved in egg production regulation, including LRP8, BMP6, ZP4, COL4A1, VCAN, INHBA, LOX, PTX3, and IHH, as well as several essential egg production pathways, such as regulation adhesion molecules (CAMs), calcium signaling pathways, neuroactive ligand–receptor interaction, and cytokine–cytokine receptor interaction. Transcriptional analysis of the chicken ovary during different phases of egg-lay will provide a useful molecular basis for study of the development of the egg-laying ovary.

Estradiol Upregulates the Expression of the TGF-β Receptors ALK5 and BMPR2 during the Gonadal Development of Schizothorax prenanti

Simple Summary

Schizothorax prenanti, known as the ya-fish, is mainly distributed in regions adjacent to the Qinghai-Tibet Plateau (QTP) and is an endemic fish species with great economic importance in aquaculture in Western China. In the present study, we were aimed to explore the functions of ALK5 and BMPR2 during the gonadal development of S. prenanti. Our results suggest that ALK5 and BMPR2 may play a potentially vital role in both folliculogenesis and spermatogenesis in S. prenanti.

Abstract

TGF-β receptors play important roles in mediating TGF-β signals during gonadal development. To identify the functions of TGF-β receptors, including the type I receptor (activin receptor-like kinase 5, ALK5) and type II receptor (bone morphogenetic protein receptor 2, BMPR2), during the gonadal development of S. prenanti, the full-length cDNA sequences of ALK5 and BMPR2 were isolated and characterized. Their expression patterns in developing gonads and in the gonads of exogenous estradiol (E₂) -fed fish were analyzed. The cDNAs of ALK5 and BMPR2 were 1925 bp and 3704 bp in length and encoded 501 and 1070 amino acid residues, respectively. ALK5 and BMPR2 were mostly expressed in gonads, particularly in cortical alveoli stage ovaries and mid-spermatogenic stage testes; however, the overall level of BMPR2 mRNA was higher than that of ALK5 during gonadal development. Furthermore, immunohistochemical signals of ALK5 and BMPR2 were mostly detected at chromatin nucleolar oocytes and perinuclear oocytes in ovaries and at spermatocytes and spermatogonia in testes. Exogenous E₂ induces the gonadal expression of ALK5 and BMPR2, and BMPR2 is more responsive to E₂ than ALK5. These results suggest that ALK5 and BMPR2 might play a potentially vital role in both folliculogenesis and spermatogenesis in S. prenanti.

Expression of genes associated with BMP signaling pathway in porcine oocytes before and after IVM - a microarray approach

BACKGROUND

The full maturational capability of mammalian oocytes is accompanied by nuclear and cytoplasmic modifications, which are associated with proliferation and differentiation of surrounding cumulus cells. These events are regulated on molecular level by the expression of target genes involved in signal transduction pathways crucial for folliculogenesis and oogenesis. Transforming growth factor beta signaling includes several molecules that are involved in the regulation of oogenesis and embryo growth, including bone morphogenetic protein (BMP). However, the BMP-related gene expression profile in oocytes at different maturational stages requires further investigation.

METHODS

Oocytes were isolated from pubertal crossbred Landrace gilts follicles, selected with a use of BCB staining test and analyzed before and after in vitro maturation. Gene expression profiles were examined using an Affymetrix microarray approach and validated by RT-qPCR. Database for Annotation, Visualization, and Integrated Discovery (DAVID) software was used for the extraction of the genes belonging to a BMP-signaling pathway ontology group.

RESULTS

The assay revealed 12,258 different transcripts in porcine oocytes, among which 379 genes were down-regulated and 40 were up-regulated. The DAVID database indicated a "BMP signaling pathway" ontology group, which was significantly regulated in both groups of oocytes. We discovered five up-regulated genes in oocytes before versus after in vitro maturation (IVM): chordin-like 1 (CHRDL1), follistatin (FST), transforming growth factor-beta receptor-type III (TGFβR3), decapentaplegic homolog 4 (SMAD4), and inhibitor of DNA binding 1 (ID1).

CONCLUSIONS

Increased expression of CHRDL1, FST, TGFβR3, SMAD4, and ID1 transcripts before IVM suggested a subordinate role of the BMP signaling pathway in porcine oocyte maturational competence. Conversely, it is postulated that these genes are involved in early stages of folliculogenesis and oogenesis regulation in pigs, since in oocytes before IVM increased expression was observed.

Fibroblast growth factor 10 markedly improves in vitro maturation of porcine cumulus-oocyte complexes

Growth factors synthesized by ovarian somatic cells affect cumulus cell expansion and oocyte maturation in vitro. Fibroblast growth factor 10 (FGF10), for example, is a known regulator of mammalian cumulus-oocyte complex maturation. In this study, we investigated the effects of 0, 5, 10, 50, and 100 ng/mL FGF10 (5F, 10F, 50F, and 100F, respectively) on in vitro cumulus cell expansion, oocyte maturation, and embryo development. The percentage of fully expanded cumulus cells at the oocyte's metaphase-II (MII) stage was significantly higher in the 10F-treated group than in the control. Transcript abundance of the cumulus cell expansion-related gene encoding hyaluronian synthase 2 (HAS2) in cumulus cells at oocyte germinal vesicle breakdown (GVBD) was significantly higher in the 10F- and 50F-treated groups compared to untreated controls, whereas the mRNA abundance of the protease cathepsin B (CTSB) at the oocyte MII stage was remarkably decreased in the 10F-treated group. The percentage of oocytes with normal spindles was greater in the 10F- and 50F-treated group at GVBD than in the other groups; the 5F-, 10F-, and 100F-treated groups were higher than the control; and the 50F-treated group was highest at MII. The abundance of GDF9 and BMP15 transcript at GVBD and BMP15 and CCNB1 transcripts at MII increased in the 10F-treated group. Cleavage rate, blastocyst formation rate, and total cell number were significantly higher in the 5F- to 50F-treated groups. These results demonstrate that FGF10 markedly improves cumulus cell expansion, oocyte maturation, and subsequent embryo development. Mol. Reprod. Dev. 84: 67-75, 2017. © 2016 Wiley Periodicals, Inc.

Temporal expression of GDF-9 and BMP-15 mRNAs in canine ovarian follicles

This study aimed to investigate the expression profiles of growth differentiation factor 9 (GDF-9) and bone morphogenetic protein 15 (BMP-15) mRNA in canine oocytes and follicular cells throughout development at the different phases of the estrus cycle. Ovarian structures (follicles and CL) and plasma progesterone concentration were used to confirm the physiological status of each donor. Denuded oocytes and their follicular cells were recovered from follicles (n = 675) distributed into 4 types (preantral, small antral ∼0.2-0.39 mm, medium antral ∼0.4-5.9 mm, and large antral ∼6-8 mm). Total RNA was extracted and reverse transcribed, and the levels of expression for these 2 genes were determined using a quantitative real-time polymerase chain reaction technique; the data were evaluated by ANOVA. Relative expressions levels of GDF-9 and BMP-15 transcripts were detected in the oocyte and follicular cells in all follicular stages evaluated, showing differential changes (P < 0.05) during development over the estrus cycle. The expression patterns of both transcripts were highly correlated between follicles cells and oocytes (r > 0.8; P < 0.05 for GDF-9 and BMP-15), although GDF-9 was expressed at higher levels (P < 0.05) in the oocyte compared with the follicle cells. All cell types showed more GDF-9 mRNA abundance at early developing stages, mainly in the anestrus phase, and declining levels in the later stages (P < 0.05), whereas BMP-15 mRNA levels increased (P < 0.05) in follicular cells and oocytes from the preantral to the later stages, and remained constant during the final preovulatory stage. In conclusion, these two genes were detected in follicular cells and oocytes and were differentially expressed during the follicular development across the estrus cycle.

Expressão gênica em ovócitos suínos de diferentes classificações morfológicas

A produção in vitro de embriões suínos tem alcançado resultados insatisfatórios: ovócitos maturados in vivo produzem uma porcentagem maior de embriões em relação aos maturados in vitro. O sucesso da maturação in vitro está diretamente relacionado com a competência ovocitária. Somente ovócitos competentes são capazes de serem fecundados e terem desenvolvimento embrionário normal. A competência ovocitária pode ser avaliada por vários parâmetros. Recentemente têm sido utilizados como parâmetro os estudos da expressão de genes associados com a competência. O presente trabalho teve por objetivo avaliar diferenças na expressão dos genes BMP15, RYBP, MATER e ZAR1 em ovócitos imaturos de diferentes classes morfológicas, sendo elas: 1, 2, 3 e 4, com a finalidade de proporcionar importantes marcadores moleculares relacionados com a capacidade ovocitária. O RNA total dos ovócitos foi extraído e utilizado como molde para a síntese da primeira fita de cDNA. Os resultados da expressão gênica foram analisados utilizando-se modelo misto, considerando os dados de expressão gênica variável dependente e as classes ovocitárias variáveis independentes. Os genes BMP15, ZAR1 e RYBP apresentaram expressão semelhante nas classes ovocitárias 1, 2 e 3; somente a categoria 4 diferiu na expressão desses genes (P<0,05). O gene MATER foi expresso de forma semelhante em todas as classes ovocitárias estudadas (P>0,05). A técnica de RT-qPCR foi eficiente para detecção desses transcritos em ovócitos de diferentes classes. No entanto, para melhor entendimento do envolvimento desses transcritos na aquisição da competência ovocitária, são necessários mais estudos avaliando ovócitos de diferentes classes morfológicas, em diferentes fases de desenvolvimento, e implicação de outros genes envolvidos com a competência ovocitária.

Effect of BMP-6 on development and maturation of mouse preantral follicles in vitro

The aim of this study was to investigate the effect and mechanism of bone morphogenetic protein-6 (BMP-6) on the growth and maturation of mouse follicles in vitro. Preantral follicles isolated from mice were incubated with recombinant human BMP-6 (rhBMP-6) before analysis. BMP-6 expression was detected by immunofluorescence and western blot. Maturation of oocytes was observed microscopically. Estradiol (E₂) and progesterone (P₄) levels were measured by enzyme-linked immunosorbent assay. Expression of steroidogenesis-related genes was detected by reverse transcription quantitative polymerase chain reaction. There was a marked increase in the preantral follicles maturation in cells incubated with 50 ng/mL of rhBMP-6 for eight days, compared with the control. The levels of E₂, P₄ and steroidogenesis-related genes were also significantly increased in granulosa cells and theca cells cultured for 6, 10 and 11 days, respectively. Conversely, the preantral follicle maturing rate was remarkably decreased in cells incubated with 50 ng/mL of rhBMP-6 for day 11, accompanied with reduction in E₂, P₄ levels and steroidogenesis-related genes levels. Meanwhile, compared with the control, the maturing rate was not significantly different in cells incubated with 100 ng/mL of rhBMP-6 for day 8 or day 11. However, the E₂ levels and its relevant regulation gene expression all increased significantly, while the P₄ content and its relevant regulation gene expression decreased. The results indicate that BMP-6 can promote the maturation of preantral follicles in vitro in a concentration and time-dependent manner and may play a role in the regulation of steroid hormone synthesis and/or secretion.

Comparative expression profiles of genes related to oocyte development in goats after long-term feeding with biodiesel castor industry residues

The aim of this study was to determine whether the consumption of detoxified castor meal (DCM) by goats over a long period of time affects mRNA levels in oocytes, and in mural granulosa and cumulus cells. A total of 41 adult does were supplemented (DCM group, n=21) or not (control group, n=20) with detoxified castor meal (DCM) for a period of 500 days. Then, 13 and 12 does were randomly selected for slaughter from the DCM and control treatments groups, respectively, for the determination of the number of visible ovarian follicles, retrieved cumulus-oocyte complexes (COCs), and viable and non-viable oocytes. The relative expression levels for distinct genes were determined by quantitative PCR in viable immature oocytes prior to in vitro maturation (IVM), in oocytes attaining or not the metaphase stage after IVM, as well as in granulosa cells obtained upon oocyte collection, and in cumulus cells obtained after IVM. The number of follicles ≥4 mm did not differ between treatments (overall mean 23.3 ± 2.0) and no significant differences were observed in the recovery of viable, non-viable, or total mean numbers of oocytes (control group: 44.7 ± 4.6, DCM group: 54.9 ± 5.9, respectively) between control and DCM fed goats. The maturation rate was significantly higher for control than DCM oocytes (58.0% vs. 45.3%; P<0.05). The mRNA levels in immature COC for controls were significantly higher for GLUT1 and lower for HSP70 (P<0.05) than for DCM. Following maturation, MII oocytes from both treatments had mRNA levels that were significantly higher for GDF9 and lower for BMP15 than for NC oocytes (P<0.05). In cumulus cells, the mRNA levels were significantly higher for LHR, FSHR, LeptinR, and IGF1, and lower for MnSOD in the control group compared with the DCM group (P<0.05). In conclusion, the inclusion of DCM in goat feed for long periods of time changed gene expression in immature oocytes and in cumulus cells. This was reflected by a decrease in the in vitro oocyte maturation rate.

The effect of hormonal estrus induction on maternal effect and apoptosis-related genes expression in porcine cumulus-oocyte complexes

BACKGROUND

The effect of hormonal estrus induction on maternal effect (MATER - maternal antigen that embryo requires, ZAR-1 - zygote arrest 1, and BMP15 - bone morphogenetic protein 15) and apoptosis-related genes expression (BCL-2 and BAX) in porcine cumulus-oocyte complexes (COCs) and selected follicular parameters was investigated in this study.

METHODS

Gilts were divided into three groups: (I) with natural estrus; (II) stimulated with PMSG/hCG; and (III) with PMSG/hCG + PGF2alpha. Analysis of maternal effect and apoptosis-related transcripts expression in COCs, and progesterone synthesis pathway genes expression (P450scc and 3betaHSD) in granulosa cells was performed by qPCR. BMP15 protein expression in follicular fluid (FF) was analyzed by western blot. Oocyte nuclear maturation was assessed by aceto-orcein staining. Progesterone (P4) and estradiol (E2) concentrations in FF and serum were measured by ELISA. Data were analyzed with the one-way ANOVA and Bonferroni post-test or Kruskal-Wallis test and Dunns post-test.

RESULTS

The highest expression of MATER, ZAR-1, and BMP15 genes was found in COCs recovered from gilts treated with PMSG/hCG when compared to PMSG/hCG + PGF2alpha-stimulated or non-stimulated gilts. Hormonal treatment did not affect the BMP15 protein expression in FF, but increased the expression of genes participating in P4 synthesis in granulosa cells. The higher percentage of immature oocytes was found in PMSG/hCG-treated when compared to the non-stimulated gilts. The expression of BCL-2 and BAX mRNA, and BCL-2/BAX mRNA ratio was significantly higher in COCs derived from PMSG/hCG-treated when compared to PMSG/hCG + PGF2alpha-treated or non-stimulated subjects. The level of P4 in serum was similar in animals from all experimental groups, while its concentration in FF was greater in gilts subjected to PMSG/hCG treatment than in PMSG/hCG + PGF2alpha-stimulated and non-stimulated gilts. The concentration of E2 did not differ in the serum or FF between the control group and the hormonally stimulated groups.

CONCLUSIONS

Hormonal induction of estrus affected maternal effect gene transcripts levels in COCs and and oocyte nuclear maturation. The inclusion of PGF2alpha into the stimulation protocol enabled maintaining of physiological concentration of P4 in FF. Additionally, both hormonal treatments seem to be beneficial for apoptosis prevention through increasing BCL-2/BAX transcript ratio.

Follicular dynamics and gene expression in granulosa cells, corpora lutea and oocytes from gilts of breeds with low and high ovulation rates

Follicular dynamics and the expression of candidate genes using real-time polymerase chain reaction (PCR) were compared during the oestrous cycle of pig breeds with high (commercial line; n = 24) and low (local Brazilian Piau; n = 21) ovulation rates and prolificacy. Gilts were killed on Days 0, 4, 10 and 18 of the oestrous cycle and visible ovarian follicles were classified by follicular diameter. Recovered cumulus–oocyte complexes were classified as normal or atretic and frozen in liquid nitrogen until RNA extraction. Low ovulation rates and/or prolificacy in Piau gilts was associated with a different pattern of follicle development, with lower numbers of small follicles on Day 18, fewer large follicles on Days 0 and 18 (P ≤ 0.05) and a higher proportion of atretic follicles on Days 0 and 18 (P ≤ 0.05). Compared with commercial line gilts, less-prolific Piau gilts exhibited higher expression of apoptotic genes during luteolysis (CASP3 and FASL; P ≤ 0.05), decreased expression of TGFBR2 and BAX mRNA in the corpus luteum (P ≤ 0.05), higher expression of apoptotic genes (FAS, BCL2 and CASP8; P ≤ 0.05) in granulosa cells and a greater abundance (P ≤ 0.05) of genes controlling oocyte-secreted factors (GDF9, BMP15 and BMP6), suggesting underlying mechanisms controlling differences in follicular development, ovulation rate and inherent prolificacy in this pig breed.

Differential expression dynamics of Growth differentiation factor9 (GDF9) and Bone morphogenetic factor15 (BMP15) mRNA transcripts during in vitro maturation of buffalo (Bubalus bubalis) cumulus-oocyte complexes

The present study has evaluated the association of growth differentiation factor9 (GDF9) and bone morphogenetic protein15 (BMP15) mRNA expression in cumulus-oocyte complexes (COCs) of buffalo ovary during in vitro maturation (IVM). GDF9 and BMP15 are expressed specifically in mammalian oocytes and also participate in cumulus-oocyte crosstalk. Quantitative real-time polymerase chain reaction (qRT-PCR) technique was applied to investigate the relative abundance (RA) of GDF9 and BMP15 mRNA transcripts throughout the IVM process. Relative mRNA expression pattern of these specific genes were assessed in oocytes and cumulus cells at 0, 6, 12 and 24 h of in vitro culture. Our results revealed that RA of GDF9 during different hours of IVM showed significant reduction between 0 h and 24 h of maturation in oocytes and BMP15 transcript increased significantly (P<0.05) between 6 h and 12 h and decreased again between 12 h and 24. In cumulus cells, GDF9 remained stable during IVM upto 12 h of maturation and decreased significantly between 12 h and 24 h of maturation. Conversely, significant reduction of BMP15 was observed between 0 h and 6 h, stayed stable upto 12 h and became undetectable at 24 h of maturation. In conclusion, these two genes were differentially expressed during the period of oocyte maturation process and notably, BMP15 expression pattern is associated specifically with the period of cumulus cell expansion.

Effects of FSH on the expression of receptors for oocyte-secreted factors and members of the EGF-like family during in vitro maturation in cattle

FSH induces expansion of bovine cumulus–oocyte complexes (COCs) in cattle, which can be enhanced by oocyte-secreted factors (OSFs). In this study it was hypothesised that FSH stimulates COC expansion in part from direct stimulation of the epidermal growth factor (EGF)-like ligands amphiregulin (AREG), epiregulin (EREG) and betacellulin (BTC), but also in part through regulation of OSFs or their receptors in cumulus cells. Bovine COCs were cultured in defined medium with graded doses of FSH. In the absence of FSH, COCs did not expand. FSH caused cumulus expansion, and increased the abundance of AREG and EREG mRNA in a time- and dose-dependent manner, but decreased BTC mRNA levels. FSH had modest stimulatory effects on the levels of mRNA encoding the bone morphogenetic protein 15 (BMP15) receptor, BMPR1B, in cumulus cells, but did not alter mRNA expression of the growth and differentiation factor 9 (GDF9) receptor, TGFBR1. More interestingly, FSH dramatically stimulated levels of mRNA encoding two receptors for fibroblast growth factors (FGF), FGFR2C and FGFR3C, in cumulus cells. FSH also stimulated mRNA expression of FGFR1B, but not of FGFR2B in cumulus cells. Based on dose-response studies, FGFR3C was the receptor most sensitive to the influence of FSH. This study demonstrates that FSH stimulates the expression of EGF-like factors in bovine cumulus cells, and provides evidence that FSH differently regulates the expression of distinct receptors for OSFs in cumulus cells.

Bone morphogenetic protein-6 (BMP-6): mRNA expression and effect on steroidogenesis during in vitro maturation of porcine cumulus oocyte complexes

Oocyte secreted factors (OSFs) have emerged as important factors for follicular development. The present study investigated the effect of the potential OSF bone morphogenic protein (BMP)-6 on steroidogenesis in porcine cumulus oocyte complexes during in vitro maturation. Cumulus oocyte complexes (COCs), cumulus complexes (CCs) without oocytes and CCs with supplemented BMP-6 were cultured for 0, 5, 26 or 46 h. BMP-6 transcripts were detected in oocytes and cumulus cells at all time points. In both cell types the mRNA expression was most intense after 5h, and decreased during further maturation. After 26 and 46 h of culture, CCs secreted significantly less 17β-estradiol than COCs. This effect was reversed by adding BMP-6 to CCs cultures. In addition, a down-regulation of Cyp19A1, the rate-limiting enzyme of 17β-estradiol synthesis, was detected in CC cultures after 5h. As seen for 17β-estradiol secretion, the addition of BMP-6 caused a significant increase in Cyp19A1 mRNA levels after 5, 26 and 46 h of culture. Progesterone secretion and transcripts of steroidogenic marker proteins StAR and 3β-HSD were not affected considerably by oocyte removal or addition of BMP-6. Furthermore, BMP-6 did not affect the activity of the mitogen-activated protein kinase. The results indicated that BMP-6 is a potential OSF and is involved in the prevention of premature luteinisation in cumulus cells via enhancing 17β-estradiol synthesis.

The porcine Gpr3 gene: molecular cloning, characterization and expression level in tissues and cumulus-oocyte complexes during in vitro maturation

G protein-coupled receptor 3 (Gpr3) is a member of G protein-coupled receptor rhodopsin family, which is present throughout the follicle within the ovary and functions as a critical factor for the maintenance of meiotic prophase arrest in oocytes by a Gs protein-mediated pathway. In the current paper, attempts were made to clone and characterize a gene encoding Gpr3 from pigs and investigate its expression pattern in tissues and the whole cumulus-oocyte complexes (COCs) in vitro maturation (IVM). Rapid amplification of cDNA ends and RT-PCR gave rise to the full sequence of Gpr3 gene with its length being 2101 bp nucleotides, including an open reading frame of 993 bp, encoding a 331 amino acid polypeptide with the molecular weight of 35.2 kDa. Homology search and sequence multi-alignment demonstrated that the putative porcine Gpr3 protein sequence shared a high identity with other animal Gpr3 orthologs, including several highly conservative motifs and amino acids. Real-time PCR analysis showed that the Gpr3 gene was expressed in tissues of cerebrum, cerebellum, hypothalamus, pituitary, ovary, oviduct, uterus, heart, liver, spleen, lung, kidney, muscle, fat, testis, thymus and granulosa cell, oocyte and COCs at different expression levels. The expression levels of this gene in oocyte, uterus, liver, fat, pituitary and brain were higher than that in other tissues. Interestingly, the mRNA and protein levels of Gpr3 in the whole COCs were down-regulated, and its mRNA expression levels were significantly and negatively correlated with the degrees of cumulus expansion (r = -0.937, P < 0.01) during IVM, suggesting its important roles in cumulus expansion and oocyte maturation.

Effect of oocyte-secreted factors on porcine in vitro maturation, cumulus expansion and developmental competence of parthenotes

The oocyte is known from recent studies in the mouse, cow, sheep and human to be a central regulator of follicular cell function. However, in the pig, little information is known about the regulation of cumulus expansion by oocyte-secreted factors and oocyte quality. We investigated the possible effects of oocyte-secreted factors during in vitro maturation on cumulus expansion and on porcine oocytes as judged by subsequent embryonic development after parthenogenetic activation. Cumulus-oocyte complexes (COC) from antral follicles of pig ovaries collected from a local abattoir were divided into control and treatment groups and were cultured in tissue culture medium 199 supplemented with follicle-stimulating hormone. Treatment groups consisted of increasing numbers of denuded oocytes (DO) co-cultured with COC (at ratios of COC to DO of 1:1, 1:2, 1:3, 1:4 and 1:5). After incubation for 44 h, cumulus expansion and maturation rates were assessed and oocytes were activated parthenogenetically. Cumulus expansion in the 1 COC:4 DO and 1 COC:5 DO groups was low and altered because full dispersion of the outer layer did not occur. Cell viability was not affected, as measured by the automated cell counter, but scanning electron microscopy revealed only a scanty extracellular matrix. Blastocyst rate was significantly higher in the 1 COC:4 DO (34.4%) and in the 1 COC:5 DO (34.9%) groups (p < 0.05) when compared with other groups. Maturation rate, cleavage rate and total cell number showed no significant difference between control and treatment groups. Amplification by reverse transcription polymerase chain reaction (RT-PCR) showed up-regulation of growth differentiation factor 9 (GDF9) in the cumulus cells in the 1 COC:4 DO group at 44 h. We conclude that denuded porcine oocytes could improve the maturation of COC as evidenced by increased blastocyst development in the 1 COC:4 DO, even though cumulus expansion was poor. This improvement could be a result of the GDF9 up-regulation.

Steady-state level of bone morphogenetic protein-15 in goat ovaries and its influence on in vitro development and survival of preantral follicles

This study investigates steady-state level of bone morphogenetic protein-15 (BMP-15) mRNA in caprine follicles, and the effects of BMP-15 on in vitro development of preantral follicles. Ovarian fragments were cultured for one or seven days in Minimal Essential Medium (MEM(+)) with BMP-15 (0, 1, 10, 50, 100 or 200 ng/mL), and further analyzed by histology, transmission electron and fluorescent microscopy. BMP-15 mRNA in secondary follicles was higher than in primordial and primary follicles. After seven days, 10, 50 or 100 ng/mL of BMP-15 maintained the percentage of normal follicles similar to the control (non-cultured), and increased the oocyte and follicle diameters when compared to the control and MEM(+). BMP-15 at 100 ng/mL increased the secondary follicles and maintained their ultrastructural integrity. In conclusion, the BMP-15 mRNAs were detected in all follicular categories. BMP-15 (100 ng/mL) maintained the integrity and promoted the growth of caprine preantral follicles cultured for seven days.

Temporal effects of exogenous oocyte-secreted factors on bovine oocyte developmental competence during IVM

We investigated whether paracrine signalling between the bovine oocyte and cumulus cells is altered during the course of in vitro maturation (IVM). Bovine COCs were cocultured with denuded oocytes or treated with specific oocyte-secreted factors, namely recombinant bone morphogenetic protein (BMP)-15 or growth differentiation factor (GDF)-9, beginning from 0 or 9 h IVM. To generate a 9-h denuded oocyte (DO) group, COCs were cultured intact for the first 9 h of IVM and then denuded. Coculturing intact COCs with DOs denuded immediately after collection or following 9 h of maturation did not affect cleavage rate, but improved blastocyst yield (P < 0.05) on Day 8 (51 and 61%, respectively; P < 0.05) and cell number compared with COCs cultured alone (41%). Significantly, we observed higher levels of endogenous GDF-9 and BMP-15 protein in oocytes of COCs matured for 9 h compared with no incubation. The addition of 175 ng mL–1 GDF-9 or 10% v/v BMP-15 from partially purified transfected 293H cell supernatant for 24 h IVM significantly enhanced development to the blastocyst stage from 40% (control) to 51 and 47%, respectively (P < 0.05). However, treatment of COCs with GDF-9 or BMP-15 between 9 and 24 h of IVM did not increase blastocyst yield. These results provide evidence of quantitative and possibly qualitative temporal changes in oocyte paracrine factor production during IVM.

Differential expression of mRNAs encoding BMP/Smad pathway molecules in antral follicles of high- and low-fecundity Hu sheep

The Hu sheep is world-famous for its hyper-prolificacy and the bone morphogenetic protein (BMP)/Smad pathway and several other closely related molecules (GDF9, TGF-betaRI) have been shown to have a close relationship with reproduction in sheep. In order to investigate the mechanism of high fecundity in Hu sheep and its relationship with the BMP/Smad pathway, 147 Hu sheep were blood sampled for detection of the FecB mutation (A746G) in the BMPRIB gene by PCR-SSCP, and sixteen adult Hu ewes classified as either high-fecundity (HF) or low-fecundity (LF) animals were sacrificed for tissue and antral follicle sampling. The tissue distribution patterns of mRNAs encoding BMP/Smad pathway molecules including BMPs (BMP2, BMP4, BMP6, BMP7 and BMP15), BMP receptors (BMPRIA, BMPRIB and BMPRII), intracellular transducers (Smad1, Smad5 and Smad4) and closely related molecules (GDF9 and TGF-betaRI) were detected by RT-PCR and the gene expression levels in antral follicles were investigated by real-time PCR. The results showed that all experimental animals were homozygous for the BMPRIB (A746G) mutation, and all detected genes related to the BMP/Smad pathway and GDF9 and TGF-betaRI were expressed in the ovary. In addition, BMP4, BMPRIB, BMPRII, Smad4, GDF9 and TGF-betaRI mRNAs were more abundant in the antral follicles of HF animals than those of LF animals (P<0.05), but BMP15 mRNA was less abundant (P<0.01). This suggests that there could be an unidentified genetic mutation in BMPRIB, or other unidentified genes and unknown factors, which controls ovarian number by changing the expression patterns of genes known to regulate ovulation rate via the BMP/Smad pathway and closely related molecules (GDF9 and TGF-betaRI).

Involvement of polyadenylation status on maternal gene expression during in vitro maturation of porcine oocytes

During mammalian oocyte maturation, protein synthesis is mainly controlled through cytoplasmic polyadenylation of stored maternal mRNAs. In this study, the role of polyadenylation modification of maternal transcripts in pig oocytes was investigated by adding cordycepin (3'-dA), a potent polyadenylation inhibitor, to the culture medium of porcine oocytes maturing in vitro. 3'-dA significantly prevented cumulus expansion regardless of the concentration used, and inhibited pig oocyte maturation in a dose-dependent manner. Further, 3'-dA 1 microg/ml-treated MII oocytes experienced significantly lower rates of cleavage (29%) and blastocyst formation (15.35%) compared to control MII oocytes (58.6% and 35.3%, respectively). Western blotting revealed that the activity of mitogen-activated protein kinase (MAPK) and p34(cdc2) was significantly decreased in oocytes and cumulus cells treated with 3'-dA at a concentration of 1 microg/ml or greater. To further explore the underlying molecular mechanisms, expression patterns and polyadenylation states of four important genes, C-mos, cyclin B, GDF9 and BMP15, were studied as representative maternal transcripts by real-time PCR and the PAT assay. 3'-dA at concentrations above 1 microg/ml significantly prevented polyadenylation and caused aberrant expression of C-mos and GDF9 during oocyte maturation. These results suggest that polyadenylation inhibitor blocked pig oocyte maturation in vitro by one or more of the following actions: (1) inactivation of MAPK and MPF in oocytes, especially at the late stages (MI and MII); (2) prevention of cumulus cell expansion through inactivation of cellular MAPK; and (3) inhibition of the maternal mRNA polyadenylation process, which in reverse, disrupted the maternal mRNA patterns in pig oocytes' maturation in vitro.

Characterization and expression of bone morphogenetic protein 4 gene in postnatal pigs

Bone morphogenetic protein 4 (BMP4) is involved in animal embryonic development and reproductive physiology. The human and murine BMP4 genes have been isolated and characterized. The objectives of this study were to: (1) characterize the full mRNA and genomic sequence for porcine BMP4, and (2) examine BMP4 gene expression in 10 tissues of postnatal female pigs. Using RT-PCR, RACE and general PCR techniques, a 1,626 bp DNA including the full coding region of BMP4 was isolated and identified as a homologue of human BMP4 transcript variant (TV)-c. The porcine TV-c contained 3 exons and astride 3.6 kb in the isolated 7.8 kb porcine BMP4 genome. The In silicon cloning identified other three forms of mRNAs, including the homologues of human TV-1, TV-a and a novel variant related to human TV-3 (TV-3p). The porcine TV-c, TV-1 and TV-3p bear internal ribosome entry sites (IRES) in 5' untranslated region (UTR), while there are two ARE elements in the 3'UTR. The full genomic sequence of porcine BMP4 gene showed 81.38, 76.23 and 64.00% identity with that of bovine, human and murine, respectively. The expression of BMP4 mRNA was determined by RT-PCR in 7, 14, and 28 day old female piglets and non-gestational sows. The results showed that porcine BMP4 occurred in all 10 examined tissues (heart, lung, liver, kidney, ovary, spleen, spinal medulla, brain, duodenum and thymus). The mRNA expression levels were relatively higher in lung and kidney in 7 day old piglets, thymus in 14 day old piglets, and spleen in 28 day old piglets, respectively, while the higher expressions were detected in liver of non-gestational pigs (P < 0.05). Moreover, the mRNA amounts both in 7 day old piglets and sows were generally higher than those in 14 and 28 day old piglets in nearly all examined tissues, except in thymus. It is concluded that the structure of porcine BMP4 gene is highly conservative with other mammalian BMP4 genes, but some differences may present in the regulation of gene expression. BMP4 mRNAs are expressed in postnatal pigs, and is spatiotemporally regulated.

Effect of follicle size on mRNA expression in cumulus cells and oocytes of Bos indicus: an approach to identify marker genes for developmental competence

To identify the genes related to oocyte competence, we quantified transcripts for candidate genes in oocytes (H1Foo, H2A, H3A, GHR, GDF9, BMP15, OOSP1) and cumulus cells (FSHR, EGFR, GHR, PTX3, IGFII) using the follicle size model to select oocytes of better developmental quality. Follicles were dissected and distributed into four groups according to diameter as follows: 1.0-3.0, 3.1-6.0, 6.1-8.0 and >or=8.1 mm. Cumulus-oocyte complexes (COCs) were released, classified morphologically, matured, fertilised and cultured in vitro or denuded for measurement of diameter and determination of gene expression. Denuded germinal vesicle oocytes and their cumulus cells were used for gene expression analysis by reverse transcription-polymerase chain reaction. The blastocyst rate was highest for oocytes recovered from follicles>6 mm in diameter. In the oocyte, expression of the H2A transcript only increased gradually according to follicle size, being greater (P<0.05) in oocytes from follicles>or=8.1 mm in diameter than in oocytes from follicles<6.0 mm in diameter. In cumulus cells, expression of FSHR, EGFR and GHR mRNA increased with follicular size. In conclusion, we confirmed the importance of H2A for developmental competence and identified important genes in cumulus cells that may be associated with oocyte competence.

Temporal regulation of BMP2, BMP6, BMP15, GDF9, BMPR1A, BMPR1B, BMPR2 and TGFBR1 mRNA expression in the oocyte, granulosa and theca cells of developing preovulatory follicles in the pig

This study aimed to describe the abundance and localization ofBMP2,BMP6,BMP15,GDF9,BMPR1A,BMPR1B,BMPR2andTGFBR1mRNA during pig preovulatory follicular development and to evaluate their implication in improving follicular maturity in the preovulatory period preceding the second versus first post-weaning oestrus. Oocytes, granulosa (GC) and theca cells (TC) were recovered from antral follicles of primiparous sows at day 1, 2 and 4 after weaning and at day 14, 16 and 20 of their subsequent oestrous cycle. Real-time PCR analysis revealed that with the exception ofBMP6mRNA, which was absent in GC, all genes were expressed in every cell type. AlthoughBMP6,BMP15andGDF9mRNA were most abundant in the oocyte, their expression remained relatively constant during follicular development. By contrast, receptorBMPR1BandTGFBR1expressions in the GC and TC were temporally regulated.BMPR1BmRNA abundance was positively correlated with plasma oestradiol (E2) suggesting that its regulation by oestrogen may be implicated in normal folliculogenesis. Interestingly, the increase inBMPR1BmRNA and protein abundance during the periovulatory period in GC and TC suggests a role for bone morphogenetic protein (BMP) 15 in the ovulatory process. Finally, expression of these ligands and receptors was not associated with potential differences in follicle maturity observed during the second versus first post-weaning preovulatory follicular wave. In conclusion, our results clearly demonstrate the presence of a complex signalling system within the pig follicle involving the transforming growth factor-β superfamily and their receptors, and provide evidence to support a role for BMP15 and BMPR1B during ovulation.

Growth hormone pathway gene expression varies in porcine cumulus-oocyte complexes during in vitro maturation

Growth hormone (GH) plays important roles in oocyte development and facilitates the successful production of competent oocytes in many species both in vivo and in vitro. However, the mechanism of GH action on oocyte maturation is not well known. In this paper, the temporospatial messenger ribonucleic acid expression patterns of GH and several other GH-related factors were quantitatively analyzed in porcine cumulus-oocytes complex throughout in vitro maturation (IVM). GH expression was decreased in oocytes during IVM while absent in cumulus cells. GH receptor, insulin-like growth factor-1 (IGF-1), and IGF-1 receptor expressions were also downregulated in oocytes. In cumulus cells, the expression of IGF-1 decreased significantly while IGF-1 receptor expression remained constant. The transcripts of Janus kinase 2 increased in both oocytes and cumulus cells during IVM. The current precise gene expression information provides further evidence to explain the complex network of GH signaling involved in IVM of porcine oocyte.