Membrane type 1-matrix metalloproteinase (MMP)-associated MMP-2 activation increases in the rat ovary in response to an ovulatory dose of human chorionic gonadotropin

Gonadotropins stimulate ovarian proteolytic enzyme activity that is believed to be important for the remodeling of the follicular extracellular matrix. Membrane type 1-matrix metalloproteinase (MT1-MMP) has been identified in vitro as an activator of pro-MMP-2 by forming a complex with tissue inhibitors of metalloproteinase-2 (TIMP-2). In the present study, the expression pattern of MT1-MMP mRNA and the role of MT1-MMP were examined in the ovary using the gonadotropin-treated immature rat model. Ovaries were collected at selected times after eCG or hCG. RNase protection assays revealed a transient increase in MT1-MMP mRNA beginning 4 h after hCG. High expression of MT1-MMP mRNA was localized to the theca-interstitial layer of developing and preovulatory follicles, while low expression was observed in the granulosa cell layer of developing follicles by in situ hybridization. The localization pattern of MT1-MMP mRNA was compared with TIMP-2 mRNA. Both MMP-2 and TIMP-2 mRNA were expressed in the theca layer of preovulatory follicles, showing a similarity to MT1-MMP mRNA expression. To further determine whether MT1-MMP activates pro-MMP-2 in the ovary, crude plasma membrane fractions from preovulatory ovaries were analyzed by gelatin zymography. In plasma membrane fractions, pro-MMP-2 increased around the time of ovulation. Upon incubation, pro-MMP-2 was activated with the highest levels of activation at 12 h post-hCG. The addition of MT1-MMP antibody or excess TIMP-2 to membrane fractions inhibited pro-MMP-2 activation. The increase in MT1-MMP mRNA may be an important part of the mechanism necessary for the efficient generation of active MMP-2 during the ovulatory process.     

Altered expression of Bcl-2 and Bax in follicles within dehydroepiandrosterone-induced polycystic ovaries in rats

PCOS (polycystic ovary syndrome) is a heterogeneous disease characterized by hyperandrogenaemia, hirsutism, oligo- or amenorrhea, insulin resistance and anovulation. The aim of the present study was to evaluate if the balance between the ovarian expression of Bax (proapoptotic protein) and Bcl-2 (antiapoptotic protein) is altered in a PCOS model developed in rats by DHEA (dehydroepiandrosterone) administration. In addition, the ovarian morphology and the circulating progesterone levels were evaluated. Histological studies confirmed the presence of follicular cysts, atretic follicles and the absence of corpora lutea in the ovaries from the PCOS group and a significant decrease in circulating progesterone levels. Immunohistochemical studies showed that the expression of Bcl-2 and Bax were mainly localized in granulosa cells of AFs (antral follicles) in both groups. Bax expression was greater in preantral and AFs from PCOS ovarian sections than in the controls. In contrast, intense Bcl-2 immunostaining was observed in the control AFs, while Bcl-2 protein was either absent in PFs (preantral follicles) or weakly expressed in AFs from PCOS rats. These results were partially confirmed by Western studies. Data revealed that the ovarian level of Bcl-2 protein was lower in PCOS than in the control and that there were no differences in Bax ovarian levels between groups. However, Bax/Bcl-2 ratio was significantly higher in PCOS group than in the control group. In conclusion, an increase in ovarian apoptosis through an imbalance among the Bcl-2 family members may be involved in the transformation of growing follicles in cystic follicles in the ovaries from DHEA-induced PCOS rats.     

Expression and function of Fas antigen vary in bovine granulosa and theca cells during ovarian follicular development and atresia

Fas antigen is a receptor that triggers apoptosis when bound by Fas ligand (FasL). A role for Fas antigen in follicular atresia was studied in follicles obtained during the first wave of follicular development during the bovine estrous cycle (estrus is Day 0). Granulosa and theca cells were isolated from healthy dominant follicles and the two largest atretic subordinate follicles on Day 5, atretic dominant follicles on Days 10-12, and preovulatory follicles on Day 1. Fas antigen mRNA levels were highest in granulosa cells from subordinate as compared to other follicles, and lowest in theca cells from healthy Day 5 dominant as compared to other follicles. FasL alone had no effect on viability of granulosa or theca cells but became cytotoxic in the presence of interferon-gamma (IFN). IFN has been shown to induce responsiveness to Fas antigen-mediated apoptosis in other cell types. In the presence of IFN, killing of granulosa cells by FasL was greater in subordinate compared to healthy dominant follicles on Day 5, did not differ between healthy and atretic dominant follicles, and was similar in theca among all follicles. Granulosa cells from preovulatory follicles, which had been exposed to the LH surge in vivo, were completely resistant to FasL-induced killing. In summary, Fas antigen expression, and responsiveness to Fas antigen-mediated apoptosis, vary during follicular development.     

夏枯草胶囊对自身免疫性甲状腺炎大鼠甲状腺组织及Fas、FasL表达的影响

目的:探讨夏枯草胶囊对自身免疫性甲状腺炎(AITD)大鼠甲状腺组织病理学及Fas、FasL表达的影响。方法:将40只雌性SD大鼠按照随机数表法随机分为空白对照组、模型组、夏枯草胶囊组、硒酵母组,每组10只,空白对照组予以正常饲养,模型组和药物组予以PTg皮下注射建立AITD模型,夏枯草胶囊组、硒酵母组分别给予夏枯草胶囊与硒酵母片的生理水溶液灌胃,药物干预6周后处死大鼠,取甲状腺组织,HE染色电镜下观察各组大鼠甲状腺组织形态,免疫组化法检测各组大鼠甲状腺组织Fas、FasL蛋白的表达。结果:1)模型组大鼠甲状腺组织滤泡大量破坏,形态不规则,胶质分布不均匀,滤泡间隙增大,可见大量淋巴细胞及浆细胞浸润。夏枯草胶囊组滤泡形态尚规则,胶质含量较空白组少,滤泡间有少量淋巴细胞浸润。与模型组对比,夏枯草胶囊组与硒酵母组滤泡破坏及淋巴细胞浸润有显著改善。2)对照组大鼠甲状腺组织中Fas、FasL蛋白仅呈少量表达,模型组大鼠甲状腺组织中Fas、FasL蛋白表达较对照组显著增加(P0.01),夏枯草胶囊组大鼠甲状腺组织中Fas、FasL蛋白表达较模型组及硒酵母组均显著减少(P0.01)。结论:夏枯草胶囊可能通过减少Fas、FasL的表达,抑制甲状腺滤泡细胞凋亡,从而减轻甲状腺滤泡上皮的破坏。     

Expression and activity of the Fas antigen in bovine ovarian follicle cells

The Fas antigen is a cell surface receptor that triggers apoptosis when bound to Fas ligand (FasL). Studies were undertaken to determine whether the cow provides a suitable model to study the role of the Fas pathway in inducing apoptosis of ovarian cells during follicular atresia. Expression of Fas antigen mRNA and responsiveness to FasL-induced killing in vitro were measured. Effects of the cytokines tumor necrosis factor (TNF)-alpha and interferon-gamma (IFN) were studied because of previous demonstrations of their role in Fas-mediated apoptosis in other cell types. Fas antigen mRNA was detectable in cultured granulosa and theca cells, and expression was increased by treatment with IFN but not TNF. Granulosa and theca cells were resistant to FasL-induced killing unless pretreated with IFN. TNF had no effect on FasL-induced killing. Granulosa and theca cell cultures in which killing occurred in response to FasL stained positively for annexin V, an early marker for cells undergoing apoptosis. These results provide a basis for further studies using the bovine ovary to examine the role of the Fas antigen in follicular atresia.     

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. Mol. Reprod. Dev. 77: 670–678, 2010. © 2010 Wiley‐Liss, Inc.     

Involvement of the KIT/KITL signaling pathway in 4-vinylcyclohexene diepoxide-induced ovarian follicle loss in rats

Repeated daily dosing of rats with the occupational chemical 4-vinylcyclohexene diepoxide (VCD) depletes the ovary of primordial and primary follicles through an increase in the natural process of atresia. Additionally, in vitro exposure of Postnatal Day 4 (PND 4) rat ovaries to VCD causes similar follicular depletion. This study was designed to investigate survival signaling pathways that may be associated with VCD-induced ovotoxicity in small preantral follicles. Female Fischer 344 rats (PND 28) were dosed daily (80 mg/kg/day VCD i.p.; 12 days in vivo), and PND 4 ovaries were cultured (VCD 20 or 30 microM; 8 days in vitro). Microarray analysis identified a subset of 14 genes whose expression was increased or decreased by VCD in both experiments (i.e., via both exposure routes). Particularly, the analysis showed that relative to controls, VCD did not affect mRNA expression of growth and differentiation factor 9 (Gdf9), whereas there were decreases in mRNA encoding bone morphogenic protein receptor 1a (Bmpr1a) and Kit. To confirm findings from microarray, the genes Gdf9, Bmpr1a, and Kit were further examined. When growth factors associated with these pathways were added to ovarian cultures during VCD exposure, GDF9 and BMP4 had no effect on VCD-induced ovotoxicity; however, KITL attenuated this follicle loss. Additionally, there was a decrease in Kit and an increase in Kitl expression (mRNA and protein) following VCD exposure, relative to control. These results support that VCD compromises KIT/KITL signaling, which is critical for follicular survival in primordial and primary follicles.     

Lysyl oxidase and MMP-2 expression in dehydroepiandrosterone-induced polycystic ovary in rats

Polycystic ovary syndrome (PCOS) is characterized by cystogenesis; however, the cause of this cystogenesis is unknown. At ovulation, preovulatory collagenolytic activities in the ovarian follicles increase and various proteinases are needed to degrade the tissues surrounding the follicles. To clarify the roles of enzymes in collagen degradation of the follicular wall of polycystic ovary (PCO) in relation to the cystogenesis, we examined expression of lysyl oxidase (LOX), which initiates cross-link formation of the collagen and elastin in the extracellular matrix, and expression of matrix metalloproteinases (MMPs) in ovaries of model rats with PCO induced by dehydroepiandrosterone (DHEA) compared with MMP expression in control rats. DHEA treatment increased LOX mRNA expression to more than three times the control value (P: < 0.01). MMP-2 mRNA expression in control rats was threefold greater than that in the DHEA-induced group (P: < 0.05). Expression of both latent and active forms of MMP-2 in controls was more than twice that in the DHEA-induced group (P: < 0.05) as shown by Western blotting, and expression of the active form of MMP-2 was also twice as high in the controls as in the DHEA-treated group (P: < 0.05) as shown by zymography. Our results suggest that depression of MMP-2 activity and increased LOX expression may be one of the causes of the cystogenesis of PCO.     

Regulation of matrix metalloproteinase-19 messenger RNA expression in the rat ovary

Matrix metalloproteinases (MMPs) are instrumental in the constant tissue remodeling in the ovary. An induction of MMP-19 mRNA in periovulatory follicles has been reported in mouse ovaries. However, little is known about MMP-19 expression during the follicular and luteal periods or about the ovarian regulation of MMP-19 mRNA expression. We examined the expression pattern of MMP-19 mRNA during various reproductive phases and the periovulatory regulation of MMP-19 mRNA in the rat ovary. In gonadotropin-primed, immature rat ovaries, levels of MMP-19 mRNA transiently increased during both follicular growth and ovulation. The MMP-19 mRNA was localized to the theca-interstitial layer of growing follicles and to the granulosa and theca-interstitial layers of periovulatory follicles. A similar expression pattern of MMP-19 mRNA in periovulatory follicles was observed in ovaries from naturally cycling adult rats. Accumulation of MMP-19 mRNA was detected in regressing corpus luteum. The regulation of MMP-19 mRNA expression during the periovulatory period was investigated via in vivo studies and through in vitro culture studies on follicular cells. The hCG-induction of MMP-19 mRNA was mimicked by treating granulosa cells, but not theca-interstitial cells, from preovulatory follicles with LH or activators of the protein kinase (PK) A or PKC pathways. Cycloheximide blocked the LH- or forskolin-induced MMP-19 mRNA expression, demonstrating the requirement for new protein synthesis. In contrast, blocking activation of the progesterone receptor or prostaglandin synthesis had no effect on the increase in MMP-19 mRNA expression. In conclusion, the induction of MMP-19 mRNA suggests an important role of this proteinase during follicular growth, ovulation, and luteal regression.     

Changes in expression of anti-apoptotic protein, cFLIP, in granulosa cells during follicular atresia in porcine ovaries

Follicular selection is performed in mammalian ovaries, as most follicles undergo atresia during follicular development and growth. Follicular regression is indicated to begin with granulosa cell apoptosis. To reveal the molecular mechanisms of the selection, we examined the changes in the levels of cellular-Flice like inhibitory protein (cFLIP) expression in porcine granulosa cells. cFLIP is the homologue of intracellular apoptosis inducer (procaspase-8/Flice), and has two alternative splicing isoforms: cFLIP short form (cFLIP(S)) and long form (cFLIP(L)). By competing with caspase-8, cFLIP inhibits apoptosis initiated by death receptors. The changes in the levels of cFLIP(S) and cFLIP(L) mRNA and protein expression in granulosa cells were determined by RT-PCR and Western blotting, respectively. cFLIP(L) mRNA and protein were highly expressed in granulosa cells of healthy follicles and decreased during atresia. cFLIP(S) mRNA levels in granulosa cells were low and showed no change among the stages of follicular development, and its protein level was extremely low. We examined the changes in the localization of cFLIP mRNAs in pig ovaries by in situ hybridization and found that cFLIP(L) is abundant in granulosa cells of healthy follicles in comparison with those of atretic follicles. Immunohistochemical analyses demonstrated that the cFLIP protein is highly expressed in the granulosa cell of healthy follicles but weakly expressed in that of atretic follicles. We presumed that cFLIP, especially cFLIP(L), plays an anti-apoptotic role in the granulosa cells of healthy follicles of pig ovaries, and that cFLIP could be a major survival factor that determines whether growth or atresia occurs in porcine follicles.     

优思悦对多囊卵巢综合征模型大鼠卵巢功能的影响及其机制研究

摘要 目的：探讨优思悦对硫酸脱氢表雄酮（dehydroepiandrosterone,DHEA）诱导的多囊卵巢综合征模型大鼠体内性激素：睾酮( testosterone,T)、雌二醇( estradiol,E2 )、促黄体生成素( luteinizing hormone,LH)及卵泡刺激素( follicle－stimulating hormone,FSH)及PI3K /AKT信号通路的的影响。方法：将60只雌性SD大鼠随机均分为3组,包括空白组、模型组及治疗组。空白组每日颈部皮下注射0.2 mL大豆油,其余各组每日颈部皮下注射DHEA 60 mg/kg+0.2 mL大豆油,持续注射35 d。造模第21 d时,每日上午制备大鼠阴道涂片,将其放置在显微镜下观察,根据细胞形态判定大鼠的动情周期,无动情周期规律视为造模成功。造模第36 d时,连续4 w对大鼠进行灌胃,每天一次。检测大鼠阴道分泌物的细胞形态、大鼠卵巢中卵泡发育的情况。放射免疫法测定大鼠血清中T、E2、LH、FSH的含量;RT-qPCR法检测大鼠卵巢组织中PI3K /AKT信号通路相关因子（IＲS-1、AKT-2、CSK-3β、GLUT-4 mRNA和PTEN mRNA）的表达变化。结果：空白组大鼠的动情周期有规律性,而模型组大鼠的动情周期失去规律性,且模型组大鼠卵巢中的卵泡呈囊状扩张,血清中T、LH水平明显升高（P<0.05）,同时卵巢组织中的IRS-1、AKT-2、CSK-3β、GLUT-4 mRNA表达减少（P<0.05）,PTEN mRNA表达增多（P<0.05）。与模型组比较,优思悦可改善PCOS模型大鼠动情周期,降低血清T、LH水平（P<0.05）,改善卵泡发育,减少囊状扩张卵泡的形成,上调IRS-1、AKT-2、CSK-3β、GLUT-4 mRNA表达量,下调PTEN mRNA 表达量。结论：优思悦可有效治疗DHEA诱导的PCOS模型大鼠,与卵巢中的PI3K /AKT信号通路相关因子的基因表达相关。     

Expression of hyaluronan synthase 1 and distribution of hyaluronan during follicular atresia in pig ovaries

CD44 on macrophages is recognized as a phagocytic receptor involved in the phagocytosis of apoptotic cells. Recently, we detected CD44 on macrophages in atretic follicles during atresia. In this study, we evaluated the distribution of the principal CD44 ligand hyaluronan (HA) and the expressions of HA synthases (HAS: HAS1, HAS2, and HAS3) during atresia in pig ovaries. We determined the 2139-bp sequence of Sus scrofa HAS1 and raised an anti-HAS1 polyclonal antibody. The S. scrofa HAS1 sequence contained six putative HA-binding motifs and conserved amino acid residues crucial for GlcNac transferase activity. HAS1 mRNA expression was upregulated during atresia; however, HAS2 and HAS3 mRNA expression levels were low and very low to undetectable, respectively. Western blotting showed that HAS1 was markedly upregulated during atresia. Immunohistochemical analyses revealed HAS1 distribution in theca cells of healthy and early atretic (stages I and II) follicles and in progressing atretic (stage III) follicles. Hyaluronan was visualized with the HA-binding protein; it accumulated in the theca layer during all stages and in stage III follicles. Hyaluronan assay showed a significantly increased HA concentration in follicular fluid at stage III. Flow cytometry showed HAS1 expression in 55.7% of SIRPA-positive macrophages in stage III follicles. Our results suggest that the HA concentration in follicular fluids increased during atresia and that HAS1 may be the dominant HAS protein in theca cells to produce HA in pig ovaries.     

Overexpression of angiotensin II type 2 receptor promotes apoptosis and impairs insulin secretion in rat insulinoma cells

Proper follicular development is crucial for cumulus-oocyte complex (COC) maturation, ovulation and luteinisation. All these ovarian processes are regulated by finely tuned rapid tissue remodeling that involves hyaluronan and interconnecting hyaladherins-rich extracellular matrix synthesis and its breakdown by various proteinase systems like matrix metalloproteinase (MMP). Disrupted tissue remodeling machinery can result into pathophysiologies like atretic follicular cysts formation in polycystic ovary syndrome (PCOS). In present study, we employ superovulated (SO) and polycystic ovary (PCO) rat models and demonstrate that on contrary to SO, PCO rat ovary illustrates abnormal follicular morphology with differential levels of various ovarian factors [like HA (hyaluronan), TSG-6 (TNF-α-stimulated gene/protein 6), PTX-3 (pentraxin-3), HABP1 (hyaluronan binding protein 1), MMP2 (matrix metalloproteinase), MT1-MMP (membrane type 1-matrix metalloproteinase) and COX2 (Cyclooxygenase-2)] along with hyperactivities of gelatinases (like MMP9 and -2). Besides cultured COC expansion is blocked by anti-HABP1 antibody treatment showing reduced HABP1 expression. Overall, as MT1-MMP has inverse relation with HABP1 level and direct effect on MMP2 activity, the observations from current in vivo and in vitro studies indicate that disrupted ovarian HABP1 along with concurrent altered expression and hyperactivation of related MMPs can lead to abnormal follicular maturation resulting into ovarian dysfunction in PCO rat.     

Fas ligand expression coincides with alveolar cell apoptosis in late-gestation fetal lung development

Apoptosis plays a central role in the cellular remodeling of the developing lung. We determined the spatiotemporal patterns of the cell death regulators Fas and Fas ligand (FasL) during rabbit lung development and correlated their expression with pulmonary and type II cell apoptosis. Fetal rabbit lungs (25-31 days gestation) were assayed for apoptotic activity by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) and DNA size analysis. Fas and FasL expression were analyzed by RT-PCR, immunoblot, and immunohistochemistry. Type II cell apoptosis increased significantly on gestational day 28; the type II cell apoptotic index increased from 0.54 +/- 0.34% on gestational day 27 to 3.34 +/- 1.24% on day 28, P < 0.01 (ANOVA). This corresponded with the transition from the canalicular to the terminal sac stage of development. The day 28 rise in epithelial apoptosis was synchronous with a robust if transient 20-fold increase in FasL mRNA and a threefold increase in FasL protein levels. In contrast, Fas mRNA levels remained constant, suggestive of constitutive expression. Fas and FasL proteins were immunolocalized to alveolar type II cells and bronchiolar Clara cells. The correlation of this highly specific pattern of FasL expression with alveolar epithelial apoptosis and remodeling implicates the Fas/FasL system as a potentially important regulatory pathway in the control of postcanalicular alveolar cytodifferentiation.     

Steroidogenic changes and steady state amount of messenger RNA encoding steroidogenic enzymes, gonadotropin receptors and cell-death signalling in the dominant ovarian follicle during estradiol-induced atresia in cattle

Changes in steroidogenic function and associated gene expression were characterized in dominant ovarian follicles (DF) of cattle where follicles were induced to become atretic by systemic administration of estradiol benzoate (EB). In experiment 1, follicular fluid (FF) steroid concentrations in the DF were measured at 12-hourly time points for 48 h in heifers treated with 1 mg EB i.m./500 kg body weight (EB; n=20) as compared with untreated controls (C; n=19). Treatment with EB promoted a transient reduction in circulating FSH, a rapid (12 h) and sustained reduction in FF estradiol, a rapid (12 h) but transient reduction in FF progesterone and a delayed (36 h) increase in FF testosterone concentrations. In experiment 2, whole follicular wall tissue was collected from DF of mature non-lactating cows allocated to a 0 h control group (0 HC: n=7), a 24h control group (24 HC; n=7) or an EB-treated group where tissue was collected 24 h after administration of 1 mg EB i.m./500 kg body weight (EB; n=8). As for experiment 1, EB promoted a transient reduction in circulating FSH, a pronounced reduction in FF estradiol and a smaller but significant reduction in FF progesterone concentrations. Semi-quantitative RT-PCR on follicular wall tissue revealed that the loss in estrogen activity at 24 h after EB was associated with two-fold reduction in aromatase mRNA, with an apparent acceleration in loss of 17alpha-hydroxylase mRNA. Expression of genes for gonadotropin receptors (LHR and FSHR) and a cell-death signalling pathway (Fas antigen and Fas ligand) were unchanged during the initial 24h of EB-induced atresia. These results suggest that EB initiates atresia in dominant ovarian follicles through a rapid suppression of follicular estradiol synthesis, an effect associated with down-regulation of the aromatase gene. A transient suppression in circulating FSH following administration of EB appears to have initiated these events, and it is suggested that subsequent processes involved in atresia follow this loss in estrogenic function.     

Folliculogenesis is impaired and granulosa cell apoptosis is increased in leptin-deficient mice

Leptin purportedly plays an important role in pubertal development in a number of mammalian species. Adult leptin-deficient (ob/ob) female mice are infertile, but the mechanisms responsible for the reproductive failure have not been fully elucidated. The major objective of the current study was to assess the effects of a leptin deficiency on ovarian folliculogenesis and apoptosis. Beginning at 4 wk of age, control (n = 8) and ob/ob (n = 7) mice were weighed and examined daily for vaginal opening. After 3 wk the mice were killed, and the reproductive organs were weighed. Ovaries were paraffin-embedded for hematoxylin and eosin histology, TUNEL assay, and immunohistochemistry for Fas, Fas ligand (FasL), and proliferating cell nuclear antigen (PCNA). Vaginal opening was delayed, uteri were smaller, and the number of primordial follicles and total number of ovarian follicles were subnormal in ob/ob animals. Leptin-deficient animals also had a higher number of atretic follicles than controls. Granulosa cells (predominantly in preantral and early antral follicles) of ob/ob mice exhibited increased apoptotic activity as documented by TUNEL assay and elevated expression of the apoptotic markers Fas and FasL, compared with that in control animals. Ovarian expression of PCNA, a marker of DNA replication, repair, or both, did not differ between ob/ob and control mice. The data suggest that a leptin deficiency in mice is associated with impaired folliculogenesis, which results in increased follicular atresia. This impairment may be one of the causative components of infertility in leptin-deficient animals.