Expression and Localization of Fas Ligand and Fas During Atresia in Porcine Ovarian Follicles

The potential role of the KFG and KITLG proteins in preventing granulosa cell apoptosis in Bubalus bubalis

BACKGROUND

The dynamics of mammalian follicular development and atresia is an intricate process involving the cell-cell communication mediated by secreted ovarian factors. These interactions are critical for oocyte development and regulation of follicular atresia which in part are mediated by keratinocyte growth factor (KGF) and kit ligand (KITLG), but their roles in the regulation of apoptosis in buffalo granulosa cells have not yet been defined. During mammalian follicular development, granulosa cell apoptosis triggers the atresia so ~ 1% follicles reach the ovulation stage. In the present study, we used buffalo granulosa cells to examine the effects of KGF and KITLG in apoptosis regulation and investigated potential mechanism on Fas-FasL and Bcl-2 signaling pathways.

RESULT

Isolated buffalo granulosa cells were cultured with KGF and KITLG proteins using different doses (0, 10, 20, and 50 ng/ml) independently or in combination. Expression analysis for both anti-apoptotic (Bcl-2, Bcl-xL, and cFLIP) and pro-apoptotic (Bax, Fas, and FasL) genes at transcriptional levels were carried out by real-time PCR. Upon treatments, expression levels of anti-apoptotic genes were significantly upregulated in a dose-dependent manner, showing an upregulation at 50 ng/ml (independently), and at 10 ng/ml in combination. Additionally, upregulation of growth-promoting factors, bFGF, and α-Inhibin was also observed.

CONCLUSIONS

Our findings suggest the potential roles of KGF and KITLG in determining granulosa cell growth and regulating apoptosis.

CPEB3 regulates the proliferation and apoptosis of bovine cumulus cells

Cytoplasmic polyadenylation element-binding protein 3 (CPEB3) is a member of the Cytoplasmic polyadenylation element-binding family, which has been found to regulate the translation of dormant and masked mRNA in Xenopus oocytes and plays potential roles in regulating biological functions in cells and tissues. However, its role in cumulus cells is not clear. In this study, the mRNA expression of CPEB3 in bovine cumulus cells was inhibited with small interfering RNA. Cell cycle progression, proliferation, and apoptosis were measured after inhibition of CPEB3. Subsequently, changes in intracellular Reactive oxygen species content, mitochondrial membrane potential and expansion-related gene expression were examined. The results showed that after CPEB3 inhibition, cumulus cells had an abnormal cell cycle, the numbers of cells in the S and G2/M phases were significantly increased, cell proliferation was increased and apoptosis rates were decreased. These effects were likely due CPEB3 inhibition-induced decreases in intracellular Reactive oxygen species levels; increases in mitochondrial membrane potential; decreases in apoptosis; downregulation of CCNA, CCND, CCNE, CDK2, CDK4, CDK6, p21, and p27 mRNA expression; and upregulation of CCNB, CDK1, HAS2, PTGS2, PTX3, and CEBPB mRNA expression. Therefore, CPEB3 plays potential roles in regulating the biological and physiological functions of bovine cumulus cell.

Grape Seed Procyanidin B2 Protects Porcine Ovarian Granulosa Cells against Oxidative Stress-Induced Apoptosis by Upregulating let-7a Expression

Oxidative stress is a causal factor and key promoter of all kinds of reproductive disorders related to granulosa cell (GC) apoptosis that acts by dysregulating the expression of related genes. Various studies have suggested that grape seed procyanidin B2 (GSPB2) may protect GCs from oxidative injury, though the underlying mechanisms are not fully understood. Therefore, whether the beneficial effects of GSPB2 are associated with microRNAs, which have been suggested to play a critical role in GC apoptosis by regulating the expression of protein-coding genes, was investigated in this study. The results showed that GSPB2 treatment protected GCs from a H₂O₂-induced apoptosis, as detected by an MTT assay and TUNEL staining, and increased let-7a expression in GCs. Furthermore, let-7a overexpression markedly increased cell viability and inhibited H₂O₂-induced GC apoptosis. Furthermore, the overexpression of let-7a reduced the upregulation of Fas expression in H₂O₂-treated GCs at the mRNA and protein levels. Dual-luciferase reporter assay results indicated that let-7a directly targets the Fas 3′-UTR. Furthermore, the overexpression of let-7a enhanced the protective effects of GSPB2 against GC apoptosis induced by H₂O₂. These results indicate that GSPB2 inhibits H₂O₂-induced apoptosis of GCs, possibly through the upregulation of let-7a.

Effective attenuation of glyphosate-induced oxidative stress and granulosa cell apoptosis by vitamins C and E in caprines

Pesticides are known to cause a wide range of reproductive problems that possess degenerative effects on mammalian fertility. Glyphosate (GLP), a broad-spectrum organophosphate herbicide, is known to be a potent mammalian toxicant. The present study aims at assessing the GLP-induced (0.1, 2.0, and 4.0 mg/ml) granulosa cells toxicity and evaluating the mitigating effects of vitamins C and E (0.5 mM and 1.0 mM) in healthy caprine antral follicles, cultured in vitro in a dose- and time-dependent manner (24, 48, and 72 hr) and subjected to various cytotoxic and geno-toxic analysis, namely, classic histology, EB/AO differential staining, oxidative stress parameters, and antioxidant enzymatic activity. The histomorphological analysis and EB/AO staining elucidated increase in the incidence of apoptotic attributes within granulosa cells with increasing dose and duration of the GLP treatment. The highest apoptotic frequency was observed at 4.0 mg/ml GLP after 72-hr exposure duration in comparison with the control. GLP exposure also led to a significant decline in the antioxidant enzymes' activity, namely, SOD, catalase, and GST along with enhanced lipid peroxidation and reduced FRAP activity in a dose- and time-dependent manner. Vitamins C and E supplementation decreased oxidative stress-mediated granulosa cells apoptosis, suggesting its efficiency to diminish GLP-mediated GCs cytotoxicity and thereby, preventing associated fertility disorders.

Expression and Mutation Analyses of Fas, FLIP and Bcl-2 in Granulosa Cell Tumor of Ovary

Aims and background

Mounting evidence indicates that evasion of apoptosis contributes to tumor pathogenesis. Although both Fas and Bcl-2 are crucial in apoptosis of normal ovarian cells, their roles in ovarian tumors, especially stromal tumors, are largely unknown. The aim of this study was to explore mutation of the Fas gene and expression of the apoptosis-related proteins Fas, FLICE-like inhibitory protein (FLIP) and Bcl-2 in granulosa cell tumor (GCT) of the ovary.

Methods

We analyzed the expression of Fas, FLIP and Bcl-2 in 20 GCT tissues by immunohistochemistry. We also analyzed somatic mutations of the Fas gene in the same GCT tissues by polymerase chain reaction and single-strand conformation polymorphism assay.

Results

Expression of Fas was evident in 12 GCTs (60%), but the remaining 8 GCTs showed no or markedly decreased Fas immunostaining. Expression of FLIP was identified in 30% of the GCT samples and expression of Bcl-2 in 75%. All GCTs with positive Fas expression (n = 12) showed either FLIP or Bcl-2 expression. The GCTs were found to carry no somatic Fas mutations.

Conclusions

Our data show that alterations of the apoptosis-related proteins Fas, FLIP and Bcl-2 are common in GCT, and suggest that expression of FLIP and Bcl-2 and loss of Fas expression might play role in the pathogenesis of GCT, possibly by inhibiting apoptosis.

Altered FoxO3 expression and apoptosis in granulosa cells of women with polycystic ovary syndrome

PURPOSE

To determine the level of apoptosis, and alteration of FoxO3 (forkhead box O3 transcription factor) expression and phosphorylation in human granulosa cells amongst polycystic ovary syndrome (PCOS) patients and control group.

METHODS

We recruited infertile women with PCOS (n = 14) and compared them with infertile women due to tubal blockage or male factor infertility (n = 14, controls). GnRH agonist and gonadotropins were used for ovarian stimulation. Follicular fluids from large follicles (>16 mm) were pooled and granulosa cells (GCs) were isolated using cell strainer methodology. Apoptosis of purified GCs was measured by flow cytometry using Annexin V and propidium iodide. Quantitative real-time PCR and western blotting were performed to assess alteration of FoxO3 expression and phosphorylation in GCs.

RESULTS

There were higher percentages of early and late apoptosis in GCs of PCOS patients than in the control group. FoxO3 mRNA level and total FoxO3 protein were significantly higher in PCOS group than in the control group. The ratio of p-FoxO3/total FoxO3 decreased significantly in PCOS than in the control group. It was inferred that unphosphorylated (active form) FoxO3 was higher in GCs of PCOS patients. Apoptosis was significantly and positively correlated with the total FoxO3 and negatively correlated with the p-FoxO3 protein levels in PCOS patients.

CONCLUSIONS

Activation and overexpression of FoxO3 in granulosa cells of PCOS women correlated with higher apoptosis levels in these cells suggesting that FoxO3 may be a candidate for the higher apoptosis in granulosa cells from women with PCOS.

Assessment of vitrification outcome by xenotransplantation of ovarian cortex pieces in γ-irradiated mice: morphological and molecular analyses of apoptosis

PURPOSE

The aim of this study was the investigation of caspase-3/7 activity and apoptosis related gene expression after vitrification and xenotransplantation of human ovarian fragments.

METHODS

Ovarian specimens were obtained from normal female-to-male transsexual women during laparoscopic surgery and cut into small pieces and were considered as vitrified and non-vitrified groups. The morphological study, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, caspase-3/7 activity and apoptosis related gene expression analysis were done in both non-vitrified and vitrified groups in two steps (before transplantation of ovarian tissues and 30 days after transplantation).

RESULT(S)

In spite of high rate of normal follicles in both non-transplanted tissues these rates were significantly decreased in vitrified and non-vitrified grafted tissues, moreover grafted-vitrified tissue showed significantly less normal follicles than grafted-non-vitrified group (P < 0.05). The expression of some pro and anti-apoptotic genes in vitrified-warmed tissues were not changed compared to non-vitrified ones but the expression of Fas and caspase8 was increased and the expression of BRIC5 was decreased in this group (P < 0.05). In transplanted vitrified group the Bcl2, FasL and BRIC5 gene expression was high and caspase8 was low (P < 0.05). The expression of all genes in both grafted groups was more than non-grafted tissues except for caspase8 (P < 0.05). The TUNEL positive signals and caspase-3/7 activity were increased in both grafted groups compared to non-grafted groups and this enzyme activity in grafted-vitrified group was more than grafted-non-vitrified group (P < 0.05).

CONCLUSION(S)

This study provides the first evidence on the significant effect of vitrification on follicular apoptosis of grafted human ovarian tissue at mRNA level. The signs of follicular survival or degeneration detected by morphological assessment and caspase-3/7 activity were closely correlated to the changes in expression of apoptosis-related genes.

Human ovarian tissue vitrification/warming has minor effect on the expression of apoptosis-related genes

BACKGROUND

In this study, we evaluated the incidence of apoptosis at the ultrastructural levels and expression of some apoptosis-related genes in vitrified human ovarian tissue just after warming.

METHODS

Human ovarian tissue biopsies from 23 women after caesarean section were transported to the laboratory within 2 hours, and then they were cut into small pieces. Some pieces were vitrified and warmed and the other samples were considered as control. Apoptosis was assessed by a transmission electron microscope and also by molecular analysis of pro-apoptotic (Fas, FasL, Bax, p53, caspase8, and caspase3) and antiapoptotic (Bcl-2 and BIRC5) genem RNA levels using real-time RT-PCR before and after vitrification.

RESULTS

No sign of apoptosis was shown ultrastructurally in vitrified samples. The level of FasL, Bcl-2, Bax, p53, and caspase3 mRNA and Bax:Bcl-2 ratio were similar in non-vitrified and vitrified groups; however, the expression of Fas and caspase8 genes was higher and BIRC5 was lower in vitrified samples compared to non-vitrified group (P<0.05).

CONCLUSION

The fine structure of human vitrified ovarian tissue was well preserved; moreover, vitrification was shown to affect the expression of some apoptosis-related genes. However, additional study is needed to confirm this observation.

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.

Follicular growth and atresia in mammalian ovaries: regulation by survival and death of granulosa cells

The mammalian ovary is an extremely dynamic organ in which a large majority of follicles are effectively eliminated throughout their reproductive life. Due to the numerous efforts of researchers, mechanisms regulating follicular growth and atresia in mammalian ovaries have been clarified, not only their systemic regulation by hormones (gonadotropins) but also their intraovarian regulation by gonadal steroids, growth factors, cytokines and intracellular proteins. Granulosa cells in particular have been demonstrated to play a major role in deciding the fate of follicles, serving molecules that are essential for follicular growth and maintenance as well as killing themselves by an apoptotic process that results in follicular atresia. In this review, we discuss the factors that govern follicular growth and atresia, with a special focus on their regulation by granulosa cells. First, ovarian folliculogenesis in adult life is outlined. Then, we explain about the regulation of follicular growth and atresia by granulosa cells, in which hormones, growth factors and cytokines, death ligand-receptor system and B cell lymphoma/leukemia 2 (BCL2) family members (mitochondria-mediated apoptosis) are further discussed.

miR-26b promotes granulosa cell apoptosis by targeting ATM during follicular atresia in porcine ovary

More than 99% of ovarian follicles undergo atresia in mammals, but the mechanism of follicular atresia remains to be elucidated. In this study, we explored microRNA (miRNA) regulation of follicular atresia in porcine ovary. A miRNA expression profile was constructed for healthy, early atretic, and progressively atretic follicles, and the differentially expressed miRNAs were selected and analyzed. We found that miR-26b, which was upregulated during follicular atresia, increased the number of DNA breaks and promoted granulosa cell apoptosis by targeting the ataxia telangiectasia mutated gene directly in vitro.

Involvement of the up-regulated FoxO1 expression in follicular granulosa cell apoptosis induced by oxidative stress

Follicular atresia is common in female mammalian ovaries, where most follicles undergo degeneration at any stage of growth and development. Oxidative stress gives rise to triggering granulosa cell apoptosis, which has been suggested as a major cause of follicular atresia. However, the underlying mechanism by which the oxidative stress induces follicular atresia remains unclear. FoxO transcription factors are known as critical mediators in the regulation of oxidative stress and apoptosis. In this study, the involvement of FoxO1 in oxidative stress-induced apoptosis of mouse follicular granulosa cells (MGCs) was investigated in vivo and in vitro. It was observed that increased apoptotic signals correlated with elevated expression of FoxO1 in MGCs when mice were treated with the oxidant. Correspondingly, the expressions of FoxO1 target genes, such as proapoptotic genes and antioxidative genes, were also up-regulated. In primary cultured MGCs, treatment with H(2)O(2) led to FoxO1 nuclear translocation. Further studies with overexpression and knockdown of FoxO1 demonstrated the critical role of FoxO1 in the induction of MGC apoptosis by oxidative stress. Finally, inactivation of FoxO1 by insulin treatment confirmed that FoxO1 induced by oxidative stress played a pivotal role in up-regulating the expression of downstream apoptosis-related genes in MGCs. Our results suggest that up-regulation of FoxO1 by oxidative stress leads to apoptosis of granulosa cells, which eventually results in follicular atresia in mice.

Effect of RNA interference of BID and BAX mRNAs on apoptosis in granulosa cell-derived KGN cells

In mitochondrion-dependent type II apoptosis, BH3-interacting domain death agonist (BID) and BCL-2-associated X protein (BAX) promote death ligand and receptor-mediated cell death. In porcine ovaries, the levels of BID and BAX increase in follicular granulosa cells during atresia. In the present study, to confirm the pro-apoptotic activity of BID and BAX in granulosa cells, we examined the effect of RNA interference of BID or BAX on apoptosis using a human ovarian granulosa tumor cell line, KGN. By reverse transcription polymerase chain reaction (RT-PCR) and Western blotting, expression of BID and BAX was detected in KGN cells. Then, we suppressed BID and BAX mRNA expression in KGN cells using small interfering RNA (siRNA). When BID or BAX was suppressed, a significant decrease in the apoptotic cell rate was noted. In granulosa-derived cells, BID and BAX showed pro-apoptotic activity. These results suggest that BID and BAX act as signal-transducing factors in mitochondrion-dependent type II apoptosis.

Disruption of the salmon reproductive endocrine axis through prolonged nutritional stress: changes in circulating hormone levels and transcripts for ovarian genes involved in steroidogenesis and apoptosis

Mechanisms regulating the normal progression of ovarian follicular growth versus onset of atresia in fishes are poorly understood. To gain a better understanding of these processes, we exposed immature female coho salmon (Oncorhynchus kisutch) to prolonged fasting to induce follicular atresia and monitored body growth, development of the ovarian follicles, changes in reproductive hormones, and transcripts for ovarian genes. Prolonged fasting reduced body and ovary weight and increased the appearance of atretic follicles relative to normally fed controls. Endocrine analyses showed that fasting reduced plasma insulin-like growth factor 1 (IGF1), estradiol-17β (E2), and pituitary, but not plasma, levels of follicle-stimulating hormone (FSH). Transcripts for ovarian fsh receptor (fshr) and steroidogenesis-related genes, such as steroidogenic acute regulatory protein (star), 3β-hydroxysteroid dehydrogenase (hsd3b), and P450 aromatase (cyp19a1a) were significantly lower in fasted fish. Ovarian expression of apoptosis-related genes, such as Fas-associated death domain (fadd), caspase 8 (casp8), caspase 3 (casp3), and caspase 9 (casp9) were significantly elevated in fasted fish compared to fed fish, indicating that apoptosis is involved in the process of atresia in this species. Interestingly, some genes such as fadd, casp8, casp3, and hsd3b, were differentially expressed prior to increases in the number of atretic follicles and reductions in hormone levels induced by fasting, and may therefore have potential as early indicators of atresia. Together these results suggest that prolonged nutritional stress may disrupt the reproductive system and induce follicular atresia in part via reductions in ovarian IGF and FSH signaling, and downstream effects on steroidogenesis-related genes and E2 production.

Bid and Bax are involved in granulosa cell apoptosis during follicular atresia in porcine ovaries

More than 99% of follicles undergo "atresia" during follicular development and growth. Follicular atresia is predominantly regulated by granulosa cell apoptosis. However, the intracellular signaling pathway of apoptosis in granulosa cells has not been revealed. In the present study, we examined changes in the expression of BH3-interacting domain death agonist (Bid) and Bcl-2-associated X protein (Bax), which are considered to promote the cell death ligand/receptor-mediated process in mitochondrion-dependent type II apoptosis, in porcine granulosa cells during atresia. Levels of mRNA and protein of Bid and Bax were determined by the reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting techniques, respectively. Levels of Bid and Bax mRNA and protein were markedly increased in granulosa cells of early atretic follicles compared with those of healthy follicles. In situ hybridization and immunohistochemical staining revealed that mRNA and protein of Bid and Bax were present in the granulosa cells, though only traces were found in healthy follicles; however, strong staining was noted in atretic follicles. These results indicate that Bid and Bax appear to be signal transduction factors in granulosa cells during follicular atresia and appear to play proapoptotic roles and confirm that the porcine granulosa cell is a mitochondrion-dependent type II apoptotic cell.

Gonadal steroids modulate Fas-induced apoptosis of lactotropes and somatotropes

We have previously reported that Fas activation induces apoptosis of anterior pituitary cells from rats at proestrus but not at diestrus and in an estrogen-dependent manner. In this study, we evaluated the effect of Fas activation on apoptosis of lactotropes and somatotropes during the estrous cycle and explored the action of gonadal steroids on Fas-induced apoptosis. Also, we studied whether changes in Fas expression are involved in the apoptotic response of anterior pituitary cells. Fas activation increased the percentage of TUNEL-positive lactotropes and somatotropes at proestrus but not at diestrus. FasL triggered apoptosis of somatotropes only when cells from ovariectomized rats were cultured in the presence of 17 β-estradiol (E2). Progesterone (P4) blocked the apoptotic action of the Fas/FasL system in lactotropes and somatotropes incubated with E2. Both E2 and P4 increased the percentage of cells expressing Fas at the cell membrane. Our results show that Fas activation induces apoptosis of lactotropes and somatotropes at proestrus but not at diestrus. Gonadal steroids may be involved in the apoptotic response of lactotropes and somatotropes, suggesting that Fas activation is implicated in the renewal of these pituitary subpopulations during the estrous cycle. The effect of gonadal steroids on Fas expression may be only partially involved in regulation of the Fas/FasL apoptotic pathway in the anterior pituitary gland.

Effects of follicular size and FSH on granulosa cell apoptosis and atresia in porcine antral follicles

The purpose of this study was to establish a culture model for isolated intact porcine antral follicles and investigate the relationship between granulosa cell apoptosis and follicular atresia. Small (<3 mm), medium (3-5 mm) and large (>5 mm) healthy porcine follicles were isolated and cultured in serum-free TCM199 with or without follicular stimulating hormone (FSH). Microscopic identification of healthy follicles was confirmed by histology. A spontaneous onset of apoptotic cell death in granulosa cells was observed from cultured antral follicles. The apoptotic rate of granulosa cells from small follicles cultured for 24 hr was higher than those of large and medium follicles, accompanied with high FasL mRNA abundance in granulosa cells. Supplementation with 3 or 5 IU/ml FSH significantly inhibited the percentage of granulosa cells that became apoptotic. FSH did not significantly alter estradiol secretion from cultured follicles. Progesterone secretion significantly decreased after culture for 48 hr, coinciding with the morphological changes observed. FasL and Fas mRNA were expressed in the healthy, early atretic, and progressed atretic porcine follicles regardless of follicular size. However, FasL but not Fas mRNA levels increased during follicular atresia. Addition of FSH significantly decreased FasL rather than Fas mRNA levels in granulosa cells and could attenuate apoptosis. Small follicles seemed to be more susceptible to atresia as compared to medium and large follicles.

Molecular cloning of a porcine (Sus scrofa) apoptosis inhibitory ligand, netrin-1, and its receptor, p53RDL1

The apoptosis inhibitory ligand (Netrin-1) and its receptor (p53-regulated receptor for death and life: p53RDL1) play an important role in the regulation of selective apoptosis. When Netrin-1 binds to p53RDL1, p53-dependent apoptosis is inhibited. We identified porcine (Sus scrofa) cDNAs encoding Netrin-1 [pNetrin-1; 1,803 base pairs (bp) and 600 amino acids (aa)] and p53RDL1 (pp53RDL1; 2,838 bp and 945 aa). Porcine p53RDL1 (pp53RDL1) contains a death domain (DD), a tandem specific amino acid region, in its C-terminal, suggesting that it mediates death signaling by binding with other pro-apoptotic factors via the DD. Porcine Netrin-1 (pNetrin-1), pp53RDL1 and the DD in pp53RDL1 showed high levels of identity in aa sequence with human and murine Netrin-1 (98 and 97%, respectively), p53RDL1 (94 and 91%, respectively) and the DD in p53RDL1 (96 and 95%, respectively). Reverse transcription-polymerase chain reaction (RT-PCR) revealed that the levels of pNetrin-1 and pp53RDL1 mRNAs were moderate in granulosa cells compared with their expression in other tissues and that their levels during follicular atresia were stable. The Netrin-1 and p53RDL1 system may regulate the induction of apoptosis in porcine granulosa cells.

Ovarian theca cells in follicular function

The role of theca cells in every aspect of ovarian follicular function is reviewed. A distinguishing feature of theca cells may be their ability to initiate follicle growth on differentiation from cortical stromal cells, stimulate follicle growth by granulosa cell mitosis through FSH-induced androgen receptor, and cause androgen-stimulated receptor formation of FSH. As LH not only stimulates androgen production by theca cells at tonic levels, but also induces morphological luteinization in addition to androgenesis at surge levels, the dual action concept of LH is proposed. Maturation of the selected dominant follicle and atresia of subordinate antral follicles is interpreted by this concept. Two-way signalling between oocytes and somatic theca cells with growth factors is shown to play a pivotal role in preantral folliculogenesis and atresia. Thus, theca cells have a more significant role in follicular function than previously thought.

Molecular Cloning of Porcine (Sus scrofa) Tumor Necrosis Factor Receptor 2

Tumor necrosis factor (TNF) alpha can induce both cell death and proliferation by binding to either TNF receptor (TNFR) 1 or 2. In the granulosa cells of porcine ovaries, TNFalpha is considered to act as an anti-apoptotic/survival factor during follicular atresia. As a first step toward elucidating the function of TNFR2 in regulating follicular development/growth and atresia in porcine ovaries, we isolated the porcine (Sus scrofa) cDNA encoding TNFR2, which was identified from a cDNA library prepared from the follicular granulosa cells of pig ovaries. Porcine TNFR2 (1,125 bp, 375 amino acid residues), which contains specific amino acid region of transmembrane, indicated high identities with human and murine TNFR2 (78 and 69% at mRNA level, respectively; 73 and 61% at protein level, respectively), suggesting that the function of porcine TNFR2 is similar to that of human and murine homologues. Understanding the expression patterns of porcine TNFR2 mRNA in various organs, which we confirmed by reverse transcription polymerase chain reaction analysis, would help to elucidate the physiological role of TNFR2 in the regulation of apoptosis in porcine organs.