Differential effect of components of the extracellular matrix on differentiation and apoptosis

Integrative Proteomic and Phosphoproteomic Analyses of Granulosa Cells During Follicular Atresia in Porcine

Ovarian follicular atresia is a natural physiological process; however, the mechanism is not fully understood. In this study, quantitative proteomic and phosphoproteomic analyses of granulosa cells (GCs) in healthy (H), slightly atretic (SA), and atretic follicles (A) of porcine were performed by TMT labeling, enrichment of phosphopeptides, and liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis. In total, 6,201 proteins were quantified, and 4,723 phosphorylation sites of 1,760 proteins were quantified. In total, 24 (11 up, 13 down) and 50 (29 up, 21 down) proteins with a fold change (FC) > 5 were identified in H/SA and H/A, respectively. In addition, there were 20 (H/SA, up) and 39 (H/A, up) phosphosites with an FC > 7 that could serve as potential biomarkers for distinguishing different quality categories of follicles. Western blotting and immunofluorescence confirmed the reliability of the proteomic analysis. Some key proteins (e.g., MIF, beta catenin, integrin β2), phosphosites (e.g., S76 of caspase6, S22 and S636 of lamin A/C), pathways (e.g., apoptosis, regulation of actin cytoskeleton pathway), transcription factors (e.g., STAT5A, FOXO1, and BCLAF1), and kinases (e.g., PBK, CDK5, CDK12, and AKT3) involved in the atresia process were revealed via further analysis of the differentially expressed proteins (DEPs) and phosphorylated proteins (DEPPs). Further study showed that mutant caspase6 Ser76 to Ala increased the ratios of cleaved caspase6/caspase6 and cleaved caspase3/caspase3 and dephosphorylation of caspase6 at Ser76 increased cell apoptotic rate, a new potential pathway of follicular atresia. Collectively, the proteomic and phosphoproteomic profiling and functional research in the current study comprehensively analyzed the dynamic changes in protein expression and phosphorylation during follicular atresia and provided some new explanations regarding the regulation of this process.

Integrin-Linked Kinase Is a Novel Therapeutic Target in Ovarian Cancer

OBJECTIVE

The objective of this study is to identify and validate novel therapeutic target(s) in ovarian cancer.

BACKGROUND

Development of targeted therapeutics in ovarian cancer has been limited by molecular heterogeneity. Although gene expression datasets are available, most of them lack appropriate pair-matched controls to define the alterations that result in the transformation of normal ovarian cells to cancerous cells.

METHODS

We used microarray to compare the gene expression of treatment-naïve ovarian cancer tissue samples to pair-matched normal adjacent ovarian tissue from 24 patients. Ingenuity Pathway Analysis (IPA) was used to identify target pathways for further analysis. Integrin-linked kinase (ILK) expression in SKOV3 and OV90 cells was determined using Western blot. ILK was knocked down using CRISPR/Cas9 constructs. Subcutaneous xenograft study to determine the effect of ILK knockdown on tumor growth was performed in NOD SCID gamma mice.

RESULTS

Significant upregulation of the ILK pathway was identified in 22 of the 24 cancer specimens, identifying it as a potential player that could contribute to the transformation of normal ovarian cells to cancerous cells. Knockdown of ILK in SKOV3 cells resulted in decreased cell proliferation and tumor growth, and inhibition of downstream kinase, AKT (protein kinase B). These results were further validated using an ILK-1 chemical inhibitor, compound 22.

CONCLUSION

Our initial findings validate ILK as a potential therapeutic target for molecular inhibition in ovarian cancer, which warrants further investigation.

Dual functionality of the amyloid protein TasA in Bacillus physiology and fitness on the phylloplane

Bacteria can form biofilms that consist of multicellular communities embedded in an extracellular matrix (ECM). In Bacillus subtilis, the main protein component of the ECM is the functional amyloid TasA. Here, we study further the roles played by TasA in B. subtilis physiology and biofilm formation on plant leaves and in vitro. We show that ΔtasA cells exhibit a range of cytological symptoms indicative of excessive cellular stress leading to increased cell death. TasA associates to the detergent-resistant fraction of the cell membrane, and the distribution of the flotillin-like protein FloT is altered in ΔtasA cells. We propose that, in addition to a structural function during ECM assembly and interactions with plants, TasA contributes to the stabilization of membrane dynamics as cells enter stationary phase.

The amyloid protein TasA is a main component of the extracellular matrix in Bacillus subtilis biofilms. Here the authors show that, in addition to a structural function during biofilm assembly and interactions with plants, TasA contributes to the stabilization of membrane dynamics during stationary phase.

The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on the proteome of porcine granulosa cells

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a toxic man-made chemical compound contaminating the environment. The exposure of living organisms to TCDD may result in numerous disorders, including reproductive pathologies. By employing two-dimensional fluorescence difference gel electrophoresis we aimed to identify proteins potentially involved in the mechanism of TCDD action and toxicity in porcine granulosa cells. The porcine granulosa cells were treated with TCDD (100 nM) for 3, 12 or 24 h, and afterwards, cytoplasmic proteins were isolated and labeled with cyanines. Next, samples were separated by isoelectric focusing and SDS-PAGE. Proteins of interest were identified by MALDI-TOF/TOF MS analysis. A total of 75 differentially expressed protein spots (p < 0.05 and fold change ≥2.0) were found in granulosa cells treated with TCDD. After 3, 12 and 24 h of TCDD treatment, we were able to identify 29, 34 and 12 spots, respectively. Functional analysis showed that cytoskeletal proteins formed the largest class of proteins significantly affected by TCDD in all time points. We also demonstrated that most of the identified proteins were associated with the "structural constituent of cytoskeleton" and "chaperone binding" Gene Ontology categories. Based on the analysis of the porcine granulosa cell proteome, we demonstrated that TCDD may affect the ovarian follicle fate by the rearrangement of the cytoskeleton and extracellular matrix as well as the modulation of proteins important for the cellular response to stress. The results of the current study present an extended insight into the TCDD mechanism of action in porcine granulosa cells, providing new directions for future functional studies.

STAR and AKR1B10 are down-regulated in high-grade endometrial cancer

Endometrial cancer is the most frequent gynecological malignancy in the developed world. The majority of cases are estrogen dependent, and are associated with diminished protective effects of progesterone. Endometrial cancer is also related to enhanced inflammation and decreased differentiation. In our previous studies, we examined the expression of genes involved in estrogen and progesterone actions in inflammation and tumor differentiation, in tissue samples from endometrial cancer and adjacent control endometrium. The aims of the current study were to examine correlations between gene expression and several demographic characteristics, and to evaluate changes in gene expression with regard to histopathological and clinical characteristics of 51 patients. We studied correlations and differences in expression of 38 genes involved in five pathophysiological processes: (i) estrogen-stimulated proliferation; (ii) estrogen-dependent carcinogenesis; (iii) diminished biosynthesis of progesterone: (iv) enhanced formation of progesterone metabolites; and (v) increased inflammation and decreased differentiation. Spearman correlation coefficient analysis shows that expression of PAQR7 correlates with age, expression of SRD5A1, AKR1B1 and AKR1B10 correlate with body mass, while expression of SRD5A1 and AKR1B10 correlate with body mass index. When patients with endometrial cancer were stratified based on menopausal status, histological grade, myometrial invasion, lymphovascular invasion, and FIGO stage, Mann-Whitney U tests revealed significantly decreased expression of STAR (4.4-fold; adjusted p=0.009) and AKR1B10 (9-fold; adjusted p=0.003) in high grade versus low grade tumors. Lower levels of STAR might lead to decreased de-novo steroid hormone synthesis and tumor differentiation, and lower levels of AKR1B10 to diminished elimination of toxic electrophilic carbonyl compounds in high-grade endometrial cancer. These data thus reveal the potential of STAR and AKR1B10 as prognostic biomarkers, which calls for further validation at the protein level.

Mechanosensing by the α6-integrin confers an invasive fibroblast phenotype and mediates lung fibrosis

Matrix stiffening is a prominent feature of pulmonary fibrosis. In this study, we demonstrate that matrix stiffness regulates the ability of fibrotic lung myofibroblasts to invade the basement membrane (BM). We identify α₆-integrin as a mechanosensing integrin subunit that mediates matrix stiffness-regulated myofibroblast invasion. Increasing α₆-expression, specifically the B isoform (α₆B), couples β₁-integrin to mediate MMP-2-dependent pericellular proteolysis of BM collagen IV, leading to myofibroblast invasion. Human idiopathic pulmonary fibrosis lung myofibroblasts express high levels of α₆-integrin in vitro and in vivo. Genetic ablation of α₆ in collagen-expressing mesenchymal cells or pharmacological blockade of matrix stiffness-regulated α₆-expression protects mice against bleomycin injury-induced experimental lung fibrosis. These findings suggest that α₆-integrin is a matrix stiffness-regulated mechanosensitive molecule which confers an invasive fibroblast phenotype and mediates experimental lung fibrosis. Targeting this mechanosensing α₆(β₁)-integrin offers a novel anti-fibrotic strategy against lung fibrosis.

Matrix stiffening is a feature of pulmonary fibrosis, and is amplified by lung myofibroblasts. Here the authors find that a6 integrin expression is upregulated on lung myofibroblasts in response to matrix stiffness, and this integrin is required for myofibroblast invasion, and fibrosis in an experimental disease model.

Role of Notch signaling in granulosa cell proliferation and polyovular follicle induction during folliculogenesis in mouse ovary

In the fetal mouse ovary, oocytes are connected by an intercellular bridge and form germ cell cysts. Folliculogenesis begins after birth. To study the role of Notch signaling in folliculogenesis, double-immunohistochemical localization of laminin and Ki-67 was performed in mouse ovaries from embryonic day 17.5 (E17.5) to postnatal day 4 (P4). Most cysts and follicles contained Ki-67-negative cells; however, a few Ki-67-positive cells were present in cysts from E17.5 through P4, indicating that a small number of pre-granulosa cells continue to proliferate during folliculogenesis. To examine the effects of an inhibitor of Notch signaling (DAPT) and a synthetic estrogen (diethylstilbestrol [DES]) on folliculogenesis, an organ-culture system was established. The numbers of cysts, primordial follicles (PrFs) and primary follicles were unchanged by DES, whereas the total number of PrFs and of PrFs with Ki-67-negative cells was reduced by DAPT. In organ-cultured neonatal ovaries, only DAPT treatment increased degenerating cells defined as oocytes. On the contrary, the number of polyovular follicles (PFs) and the PF incidence were significantly increased in ovaries organ-cultured with DES at day 20 post-grafting. In organ-cultured fetal and neonatal ovaries, DAPT reduced Notch 3 and Hey2 mRNAs, whereas DES increased Hey2 mRNA. These results suggest that Notch signaling in fetal ovaries is involved with PrF assembly by the regulation of oocyte survival rather than by cell proliferation. In PF induction, as a result of the disruption of interactions between oocytes and pre-granulosa cells, DES and Notch signaling act independently.

Identifying a novel role for X-prolyl aminopeptidase (Xpnpep) 2 in CrVI-induced adverse effects on germ cell nest breakdown and follicle development in rats

Environmental exposure to endocrine-disrupting chemicals (EDCs) is one cause of premature ovarian failure (POF). Hexavalent chromium (CrVI) is a heavy metal EDC widely used in more than 50 industries, including chrome plating, welding, wood processing, and tanneries. Recent data from U.S. Environmental Protection Agency indicate increased levels of Cr in drinking water from several American cities, which potentially predispose residents to various health problems. Recently, we demonstrated that gestational exposure to CrVI caused POF in F1 offspring. The current study was performed to identify the molecular mechanism behind CrVI-induced POF. Pregnant rats were treated with 25 ppm of potassium dichromate from Gestational Day (GD) 9.5 to GD 14.5 through drinking water, and the fetuses were exposed to CrVI through transplacental transfer. Ovaries were removed from the fetuses or pups on Embryonic Day (ED) 15.5, ED 17.5, Postnatal Day (PND) 1, PND 4, or PND 25, and various analyses were performed. Results showed that gestational exposure to CrVI: 1) increased germ cell/oocyte apoptosis and advanced germ cell nest (GCN) breakdown; 2) increased X-prolyl aminopeptidase (Xpnpep) 2, a POF marker in humans, during GCN breakdown; 3) decreased Xpnpep2 during postnatal follicle development; and 4) increased colocalization of Xpnpep2 with Col3 and Col4. We also found that Xpnpep2 inversely regulated the expression of Col1, Col3, and Col4 in all the developmental stages studied. Thus, CrVI advanced GCN breakdown and increased follicle atresia in F1 female progeny by targeting Xpnpep2.

The fibroblast growth factor family: involvement in the regulation of folliculogenesis

Several growth factors have been identified as local regulators of follicle development and ovulation. Fibroblast growth factor (FGF) family members are potent mitogens and are involved in cell differentiation, cell migration and angiogenesis in many tissues and organs. In addition to FGF-2, which is the most-studied FGF, other important members are FGF-1, -5, -7, -8, -9 and -10. A number of studies have indicated that FGFs play important roles in regulating the initiation of primordial follicle growth, oocyte and follicle survival, granulosa and theca cell proliferation and differentiation, corpus luteum formation, steroidogenesis and angiogenesis. The purpose of this review is to highlight the importance of the FGFs on mammalian female reproduction, providing a better understanding of the roles of this family in ovarian physiology and female fertility.

LAMC1 gene is associated with premature ovarian failure

OBJECTIVES

Common variations with modest effect in complex and polygenic disease such as premature ovarian failure (POF) can be detected by a genome wide association study. We performed a genome wide association study to identify predisposing genes associated with an increased risk of POF.

STUDY DESIGN

In stage I, genome wide association study was performed using 24 POF patients and 24 matched controls. A strongly associated region was re-tested to confirm the association with POF in stage II using 98 patients and 218 matched controls.

RESULTS

In the stage I, we found a strongly associated region that was located on chromosome 1q31 and encoded the laminin gamma 1 (LAMC1) gene. All 22 single nucleotide polymorphisms (SNPs) in the LAMC1 formed a linkage disequilibrium block and two haplotypes were significantly associated with POF. In the stage II, 14 SNPs, the majority of which were SNPs located in coding region and tagging SNPs, were genotyped. Distributions of 9 SNPs of them including one nonsynonymous SNP (rs20558) and one haplotype (HT1, C-C-T-G-C-C-A-T-T-C) were significantly higher in POF patients than in control group (86.6% and 74.5%, respectively, OR=2.209, CI: 1.139-4.284, P=0.017).

CONCLUSIONS

We showed for the first time that LAMC1 is significantly associated with POF, and specifically, possession of at least one HT1 was associated with susceptibility to POF. This result means that HT1 may co-exist with causative variant for susceptibility to POF in linkage disequilibrium and that the LAMC1 may be involved in POF pathogenesis.

The use of a polyelectrolyte fibrous scaffold to deliver differentiated hMSCs to the liver

Liver transplantation as a therapy for liver failure is often hampered by a shortage of donor tissue. The delivery of liver-differentiated human mesenchymal stem cells (hMSCs) is a potential therapy to aid in liver regeneration. In this study, an RGD-modified chitosan-alginate polyelectrolyte complex (PEC) fibrous non-woven scaffold was employed to deliver differentiated hMSCs in vivo. Bone marrow-derived hMSCs were differentiated in vitro by a combination of extracellular matrix (ECM) and conditioned medium and seeded onto the RGD-modified chitosan-alginate fibrous scaffolds. The cell/scaffold construct was then implanted into the livers of a rat model, where 70% of the liver had been removed. Post-implantation analysis of the cell/scaffold constructs showed positive periodic acid-Schiff (PAS) staining for glycogen, and expression of the hepatic markers, AFP, CK19, CK18, albumin, HNF-3beta and MRP-2 by immunofluorescence labeling. In addition, human albumin was detectable in the rat serum by spot blot. These findings demonstrated that the RGD-modified chitosan-alginate fibrous scaffold was useful for delivering transdifferentiated hMSCs into the liver and maintaining the differentiated phenotype of the cells.

Composite scaffolds for the engineering of hollow organs and tissues

Several types of synthetic and naturally derived biomaterials have been used for augmenting hollow organs and tissues. However, each has desirable traits which were exclusive of the other. We fabricated a composite scaffold and tested its potential for the engineering of hollow organs in a bladder tissue model. The composite scaffolds were configured to accommodate a large number of cells on one side and were designed to serve as a barrier on the opposite side. The scaffolds were fabricated by bonding a collagen matrix to PGA polymers with threaded collagen fiber stitches. Urothelial and bladder smooth muscle cells were seeded on the composite scaffolds, and implanted in mice for up to 4 weeks and analyzed. Both cell types readily attached and proliferated on the scaffolds and formed bladder tissue-like structures in vivo. These structures consisted of a luminal urothelial layer, a collagen rich compartment and a peripheral smooth muscle layer. Biomechanical studies demonstrated that the tissues were readily elastic while maintaining their pre-configured structures. This study demonstrates that a composite scaffold can be fabricated with two completely different polymer systems for the engineering of hollow organs. The composite scaffolds are biocompatible, possess adequate physical and structural characteristics for bladder tissue engineering, and are able to form tissues in vivo. This scaffold system may be useful in patients requiring hollow organ replacement.

Preparation of extracellular matrices produced by cultured corneal endothelial and PF-HR9 endodermal cells

The ECM is an organized complex of collagens, proteoglycans, and glycoproteins, all interacting to produce a highly stable structure upon which cells migrate, proliferate, differentiate, and survive in vivo. Cultured bovine corneal endothelial (BCE) cells and PF-HR9 endodermal cells produce underlying ECMs that adhere strongly to plastic and closely resemble subendothelial and subepithelial basement membranes in vivo in their morphology, molecular composition, and biological activities. This unit describes the methods for preparation of these ECMs, their properties, and their cellular effects.

The role of the extracellular matrix in ovarian follicle development

Regulation of ovarian follicle development depends on endocrine- and paracrine-acting hormones, the 3-dimensional architecture of the follicle, and the physical rigidity of the surrounding tissue. These 3 forces are integrated throughout the life cycle of the follicle to ensure appropriate hormone secretion, differentiation of the somatic cells, and maturation of the oocyte. The process of in-follicle maturation provides a new tool for understanding ovarian follicle development under the influence of these factors.

Distribution of extracellular matrix proteins type I collagen, type IV collagen, fibronectin, and laminin in mouse folliculogenesis

The extracellular matrix (ECM) plays a prominent role in ovarian function by participating in processes such as cell migration, proliferation, growth, and development. Although some of these signaling processes have been characterized in the mouse, the relative quantity and distribution of ECM proteins within developing follicles of the ovary have not been characterized. This study uses immunohistochemistry and real-time PCR to characterize the ECM components type I collagen, type IV collagen, fibronectin, and laminin in the mouse ovary according to follicle stage and cellular compartment. Collagen I was present throughout the ovary, with higher concentrations in the ovarian surface epithelium and follicular compartments. Collagen IV was abundant in the theca cell compartment with low-level expression in the stroma and granulosa cells. The distribution of collagen was consistent throughout follicle maturation. Fibronectin staining in the stroma and theca cell compartment increased throughout follicle development, while staining in the granulosa cell compartment decreased. Heavy staining was also observed in the follicular fluid of antral follicles. Laminin was localized primarily to the theca cell compartment, with a defined ring at the exterior of the follicular granulosa cells marking the basement membrane. Low levels of laminin were also apparent in the stroma and granulosa cell compartment. Taken together, the ECM content of the mouse ovary changes during follicular development and reveals a distinct spatial and temporal pattern. This understanding of ECM composition and distribution can be used in the basic studies of ECM function during follicle development, and could aid in the development of in vitro systems for follicle growth.

Using the chorions of fertilized zebrafish eggs as a biomaterial for the attachment and differentiation of mouse stem cells

The development of proper biomaterials is critical for the success of cell therapy and modern tissue engineering. Here, we extruded the yolk and remaining inner mass from fertilized zebrafish eggs and used the resulting chorions as a biomaterial for the differentiation and attachment of mouse P19 embryonic carcinoma (EC) cells. Cells inserted into the chorion showed the spontaneous formation of embryoid body due to the repulsive cell adhesion of the chorion and differentiated specifically into neural cells and cardiomyocytes. In contrast, dissolved chorion extracellular matrix (ECM) conferred enhanced cell attachment on it, suggesting that a unique property of the zebrafish chorion with nanoporous structure appears to be responsible for the simple and controllable embryoid formation for stem cell differentiation. These results indicate that chorions from fertilized zebrafish eggs may be used as an extracellular matrix alternative and applied for stem cell differentiation to specific cell lineages.

Cytoskeleton reorganization mediates alpha6beta1 integrin-associated actions of laminin on proliferation and survival, but not on steroidogenesis of ovine granulosa cells

BACKGROUND

Laminin (LN) is one of the most abundant extracellular matrix components of the basal lamina and granulosa cell layers of ovarian follicles. Culture of ovine granulosa cells (GC) on LN substratum induces cell spreading, enhances cell survival and proliferation, and promotes luteinization. Previous investigations have shown that these effects are mostly mediated by the alpha6beta1 integrin, but its signalization pathways have not been investigated. This study aimed to assess the importance of the cytoskeleton in the alpha6beta1 integrin-mediated actions of laminin on survival, proliferation and steroidogenesis of ovine GC.

METHODS

The relationships between morphology and functions of ovine GC cultured on substrata containing LN or/and RGD peptides were investigated. The effects of (1) cytochalasin D, an actin cytoskeleton-disrupting drug, (2) a specific function-blocking antibody raised against alpha6 integrin subunit (anti-alpha6 IgG), and (3) an inhibitor of the ERK1/2 signalization pathway (PD98059) were assessed for GC shape, pyknosis and proliferation rates, oestradiol and progesterone secretions.

RESULTS

Cytoskeleton disruption by cytochalasin D induced cell rounding, inhibited proliferation, promoted pyknosis, inhibited progesterone secretion and enhanced oestradiol secretion by GC cultured on LN. When GC were cultured on various substrata containing LN and/or RGD peptides in the presence or absence of anti-alpha6 IgG, both the existence of close correlations between the percentage of round cells, and the GC proliferation rate (r = -0.87) and pyknotic rate (r = 0.76) were established, but no relationship was found between cell shape and steroidogenesis. Inhibition of the ERK1/2 signalization pathway by PD98059 had no effect on GC shape, proliferation or pyknotic rates. However, it dramatically reduced progesterone secretion, expression of cytochrome P450 cholesterol side-chain cleavage and 3beta-hydroxysteroid deshydrogenase enzymes, and enhanced oestradiol secretion, thereby reproducing all the effects of the anti-alpha6 IgG on steroidogenesis of GC cultured on LN.

CONCLUSION

LN may participate in the paracrine control of follicular development through different mechanisms. It could enhance proliferation and survival of GC through its alpha6beta1 integrin-mediated actions on cytoskeleton. In contrast, its stimulating action on GC luteinization could be partly mediated by the ERK1/2 pathway, irrespective of cell shape.

In vitro maturation of human oocytes and cumulus cells using a co-culture three-dimensional collagen gel system

BACKGROUND

Deficiencies remain in the ability of in vitro-matured human oocytes to acquire full developmental competence and give rise to a healthy pregnancy. A clear deficiency of current systems utilizing human oocytes has been the absence of cumulus cells. In the present study, a three-dimensional (3D) co-culture system exploiting an extracellular matrix was developed and compared to conventional methods for its ability to support maturation of human oocytes.

METHODS AND RESULTS

Cumulus cells were embedded into a 3D collagen gel matrix with individual oocytes added to each gel. Oocytes from the same patient cultured in the gel matrix matured to metaphase II at rates similar to those of cumulus-free oocytes cultured in individual microdrops. Following maturation of oocytes and fixation of intact gels, chromatin and cytoskeletal elements were assessed in oocytes and cumulus cells. The activities of the key cell cycle kinases, maturation-promoting factor (MPF) and mitogen-activated protein kinase (MAPK), were compared in oocytes matured under the two culture conditions. Compared with denuded oocytes, co-cultured oocytes exhibited increased MAPK activity, but no difference in MPF levels.

CONCLUSIONS

This work characterizes a novel and efficacious culture system that takes advantage of the unique properties of the extracellular matrix, a 3D microenvironment, and the presence of cumulus cells for maturing human oocytes in vitro.

Changes in the Distribution of Tenascin and Fibronectin in the Mouse Ovary During Folliculogenesis, Atresia, Corpus Luteum Formation and Luteolysis

Tenascin and fibronectin are components of the extracellular matrices that oppose and promote adhesion, respectively. Using immunohistochemical techniques, we studied the distribution of tenascin and fibronectin in the mouse ovary, in which dynamic reconstruction and degeneration occur during folliculogenesis, atresia, ovulation, corpus luteum formation and luteolysis. In growing follicles, tenascin was only detected in the theca externa layer, while fibronectin was detected in the theca externa layer, theca interna layer and basement membrane. During follicular atresia, granulosa cells, which are surrounded by the basement membrane, began to die through apoptosis. In atretic follicles, tenascin was detected in the basement membrane and theca externa layer. Distribution of fibronectin in atretic follicles was similar to that in healthy growing follicles, except that granulosa cells were slightly immunopositive for fibronectin. In young corpus luteum, luteal cells exhibit high 3 beta -hydroxysteroid dehydrogenase (3 beta -HSD) activity, an enzyme indispensable for progesterone production. Tenascin was barely detected in young luteal cells. 3 beta -HSD activity in luteal cells declines with corpus luteum age, and in older corpus luteum there is an increase in apoptotic death of luteal cells. Tenascin was intensely immunopositive in old luteal cells.In contrast, fibronectin immunostaining in luteal cells was relatively constant during corpus luteum formation and luteolysis. Our observations suggest that tenascin is critical in controlling the degenerative changes of tissues in mouse ovaries. Moreover, in all circumstances observed in this study, tenascin always co-localized with fibronectin, suggesting fibronectin is indispensable for the function of tenascin.

Distribution patterns of TGF-alpha, laminin and fibronectin and their relationship with folliculogenesis in rat ovary

Many growth factors are considered to be involved in regulatory functions in the ovary. Specific factors mediate local cell-cell interactions in relation to follicle development. As a result of the complexity of the estrous cycles in experimental models, it is not easy to determine the role of a growth factor such as transforming growth factor alpha (TGF-alpha) in the system. Moreover, little is known about possible interactions of TGF-alpha and laminin and fibronectin in basement membranes during estrous cycles in relation to follicle development. Therefore, the present study was designed to investigate distribution patterns of TGF-alpha, laminin and fibronectin and their possible roles during follicle maturation in normal rat ovary. Ovaries were obtained from 6 adult virgin female rats and fixed in buffered neutral formalin. TGF-alpha, laminin, and fibronectin distribution patterns were evaluated using 5-7-microm-thick serial sections using the immunoperoxidase method. It was found that TGF-alpha was predominantly localised in nuclei of oocytes. Varying amounts of TGF-alpha were found in granulosa cells and interstitial thecal cells which form follicles. In addition, laminin and fibronectin were found predominantly in vascular walls, outer layers of granulosa cells and basement membranes of cuboidal/columnar surface epithelium of rat ovary. Therefore, we suggest that TGF-alpha is involved in follicular maturation. Moreover, because laminin was found to be present in between parenchymal follicle cell layers, we suggest that they were attached to supportive stromal cells by fibronectin. As TGF-alpha is associated with follicles and their relationship with the extracellular matrix, TGF-alpha may also induce formation of basement membranes which contains laminin and fibronectin components.

The developing mouse dentition: a new tool for apoptosis study

Developing limb or differentiating neural and blood cells are traditional models used to study programmed cell death in mammals. The developing mouse dentition can also be an attractive model for studying apoptosis regulation. Apoptosis is most extant during early odontogenesis in mice. The embryonic tooth pattern is comprised not only of anlagen of functional teeth (incisor, molars), but also of vestiges of ancestral tooth primordia that must be suppressed. Apoptosis is involved in (a) the elimination of vestigial tooth primordia in the prospective toothless gap (diastema) between the incisor and molars and (b) the shaping of germs in functional teeth. This type of apoptosis occurs in the dental epithelium according to a characteristic temporo-spatial pattern. Where apoptosis concentrates, specific signaling is also found. We proposed a hypothesis to explain the stimulation of apoptosis in the dental epithelium by integrating two concepts: (1) The regulation of epithelial budding by positional information generated from interactions between growth-activating and growth-inhibiting signals, and (2) apoptosis stimulation by the failure of death-suppressing signals. During the budding of the dental epithelium, local excess in growth inhibitors (e.g., Bmps) might lead to the epithelial cells' failure to receive adequate growth-activating (apoptosis-suppressing) signals (e.g., Fgfs). The resulting signal imbalance leads to cell "suicide" by apoptosis. Understanding of apoptosis regulation in the vestigial tooth primordia can help to elucidate the mechanism of their suppression during evolution and to identify factors essential for tooth survival. The latter knowledge will be important for developing a technology of tooth engineering.

Activation of multiple signal transduction pathways by glucocorticoids: protection of ovarian follicular cells against apoptosis

We have recently demonstrated that glucocorticoids protect against serum-deprivation, cAMP-, TNFalpha-, and p53-induced apoptosis in ovarian follicular cells involved in up-regulation of Bcl-2. We demonstrated that dexamethasone, which enhances steroidogenesis by up-regulation of the p450scc enzyme system, stimulates the MAPK cascade by phosphorylation of ERK1, ERK2 as well as by Akt phosphorylation within 1-5min with no effect on p38 MAPK phosphorylation. Moreover, glucocorticoids enhance expression of connexin 43, formation of gap junctions, expression of cadherins, and formation of adherence junctions within 24h of hormone stimulation of ovarian granulosa cells. It is suggested that the protective effects of glucocorticoids against apoptosis are mediated by both genomic and non-genomic mechanisms. Moreover, for the first time we show that protein phosphorylation, cell-cell contact, and intracellular communication are important mediators in glucocorticoid protection against apoptosis in ovarian follicular cells.

Basic fibroblast growth factor (bFGF) regulation of the plasma membrane calcium ATPase (PMCA) as part of an anti-apoptotic mechanism of action

Basic fibroblast growth factor (bFGF) preserves the viability of at least 13 different cells, including epithelial, endothelial, smooth muscle and neuronal cells. In spite of this profound and rather universal effect on cell viability, detailed studies regarding the mechanism of bFGF's action have not been conducted. Rather, most studies have simply shown that bFGF inhibits cells from undergoing programmed cell death (i.e. apoptosis). The most mechanistic studies to date have been conducted on either neurons or ovarian (granulosa) cells. These studies have shown that bFGF prevents apoptosis through both genomic and acute actions. Basic FGF's acute actions involved the maintenance of normal levels of intracellular free calcium levels ([Ca(2+)](i)). In granulosa cells, bFGF maintained [Ca(2+)](i) through a protein kinase C(delta) (PKCdelta)-dependent mechanism. Further, bFGF-activated PKCdelta maintained [Ca(2+)](i) by stimulating calcium efflux. The ability of bFGF to stimulate calcium efflux involved the plasma membrane calcium ATPase (PMCA). Interestingly, bFGF-activated PKCdelta appeared to regulate PMCA activity in part by promoting its membrane localization.

Steroidogenesis and apoptosis in the mammalian ovary

Ovarian cell death is an essential process for the homeostasis of ovarian function in human and other mammalian species. It ensures the selection of the dominant follicle and the demise of excess follicles. In turn, this process minimizes the possibility of multiple embryo development during pregnancy and assures the development of few, but healthy embryos. Degeneration of the old corpora lutea in each estrous/menstrual cycle by programmed cell death is essential to maintain the normal cyclicity of ovarian steroidogenesis. Although there are multiple pathways that can determine cell death or survival, crosstalk among endocrine, paracrine and autocrine factors, as well as among protooncogenes, tumor suppressor genes, survival genes and death genes, plays an important role in determining the fate of ovarian somatic and germ cells. The establishment of immortalized rat and human steroidogenic granulosa cell lines and the investigation of pure populations of primary granulosa cells allows systematic studies of the mechanisms that control steroidogenesis and apoptosis in granulosa cells. We have discovered that during initial stages of granulosa cell apoptosis progesterone production does not decrease. In contrast, we found that it is elevated up to 24h following the onset of the apoptotic stimuli exerted by starvation, cAMP, p53 or TNF-alpha stimulation, before total cell collapse. These observations raise the possibility for an alternative unique apoptotic pathway, one not involving mitochondrial Cyt C release associated with the destruction of mitochondrial structure and steroidogenic function. Using mRNA from apoptotic cells and affymetrix DNA microarray technology we discovered that granzyme B, a protease that normally resides in T cytotoxic lymphocytes and natural killer cells of the immune system is expressed and activated in granulosa cells. Thus, the apoptotic signals could bypass mitochondrial signals for apoptosis, which can preserve their steroidogenic activity until complete cell destruction. This unique apoptotic pathway assures cyclicity of estradiol and progesterone release in the estrous/menstruous cycle even during the initial stages of apoptosis.

Pleiotropic anti-apoptotic activity of glucocorticoids in ovarian follicular cells

Glucocorticoids (GC) such as hydrocortisone and dexamethasone (DEX) protect steroidogenic granulosa cells against apoptosis induced by serum deprivation, cAMP, tumor necrosis factor alpha stimulation or p53 activation. The protective effects were evident both in primary rat and human granulosa cells, which comprise the main population of the ovarian follicular cells, as well as in steroidogenic granulosa cell lines established in our laboratory. A correlation between the expression of Bcl-2 protein and protection against apoptosis induced by DEX was found in granulosa cell lines expressing various levels of Bcl-2. Incubation with DEX leads to development of a rigid network of actin cytoskeleton and increased incidence of adherence and gap junctions. Higher content of connexin 43 and total cadherins were found in GC stimulated cells compared to non-stimulated, suggesting that cell contact and intracellular communication contribute to the DEX induced resistance to apoptotic signals. Activation by DEX of MAPK and Akt/PKB but not p38 supported the view of a pleiotropic action of GC against apoptotic signals. Granzyme B, a protease characteristic for induction of apoptosis by T-cytotoxic lymphocytes and natural killer cells, was expressed and augmented during stimulation of apoptosis in the granulosa cells, and its synthesis and activation was blocked by DEX. It is concluded that GC exerted their anti-apoptotic effects in granulosa cells by multiple characteristic pathways. Moreover, the presence of endogenous granzyme B in granulosa cells suggest a novel intrinsic alternative apoptotic pathway that was earlier reported to be mediated uniquely by T-cytotoxic lymphocytes and natural killer cells. The anti-apoptotic effect of GC may play an important role in the healing process of the ovulatory follicle subsequent to follicular rupture and its rapid conversion to an active corpus luteum.

Alternative pathways of ovarian apoptosis: death for life

Ovarian cell death is an essential process for the homeostasis of ovarian function in human and other mammalian species. It ensures the selection of the dominant follicle and the demise of excess follicles. In turn, this process minimizes the possibility of multiple embryo development during pregnancy and assures the development of few, but healthy embryos. Degeneration of the old corpora lutea in each estrus/menstrual cycle by programmed cell death is essential for maintaining the normal cyclicity of ovarian steroidogenesis. Although there are multiple pathways that can determine cell death or survival, crosstalk among endocrine, paracrine and autocrine factors, as well as among protooncogenes, tumor suppressor genes, survival genes and death genes, play an important role in determining the fate of ovarian somatic and germ cells. The establishment of immortalized rat and human steroidogenic granulosa cell lines and the investigation of pure populations of primary granulosa cells allows for systematic studies of the mechanisms that control steroidogenesis and apoptosis of granulosa cells. We have discovered that during initial stages of granulosa cell apoptosis progesterone production does not decrease. In contrast, we found that it is elevated for up to 24hr following the onset of the apoptotic stimuli exerted by starvation, cAMP, p53 or tumor necrosis factor alpha stimulation, before total cell collapse. These observations raise the possibility for an alternative unique apoptotic pathway, one that does not involve mitochondrial cytochrome C release associated with the destruction of mitochondrial structure and steroidogenic function. Using mRNA from apoptotic cells and Affymetrix DNA microarray we discovered that Granzyme B, a protease that normally resides in T cytotoxic lymphocytes and natural killer cells of the immune system is expressed and activated in granulosa cells, thereby allowing the apoptotic signals to bypass mitochondrial signals for apoptosis, which can preserve their steroidogenic activity until complete cell destruction. This unique apoptotic pathway assures the cyclicity of estradiol and progesterone release in the estrus/menstrus cycle even during the initial stage of apoptosis.

Novel genes modulated by FSH in normal and immortalized FSH-responsive cells: new insights into the mechanism of FSH action

Follicle-stimulating hormone (FSH) controls the development of follicle-enclosed oocytes in the mammalian ovary by interacting with specific receptors located exclusively on granulosa cells. Its biological activity involves stimulation of intercellular communication, intracellular signaling, and up-regulation of steroidogenesis; the entire spectrum of genes regulated by FSH is not yet fully characterized. We have established monoclonal rat FSH-responsive granulosa cell lines that express FSH receptors at 20-fold higher rates than with primary cells, and thus increased the probability of yielding a distinct spectrum of genes modulated by FSH. Using Affymetrix DNA microarrays, we discovered 11 genes not reported earlier to be up-regulated by FSH and 9 genes not reported earlier to be down-regulated by FSH. Modulation of signal transduction associated with G-protein signaling, phosphorylation of proteins, and intracellular-extracellular ion balance was suggested by up-regulation of decay accelerating factor GPI-form precursor (DAF), membrane interacting protein RGS16, protein tyrosine phosphatase (PTPase), oxidative stress-inducible protein tyrosine phosphatase (OSIPTPase), and down-regulation of rat prostatic acid phosphatase (rPAP), Na+, K+-ATPase, and protein phosphatase 1beta. Elevation in granzyme-like proteins 1 and 3, and natural killer (NK) cell protease 1 (NKP-1) along with reduction in carboxypeptidase E indicates possible FSH-mediated preparation of the cells for apoptosis. Up-regulation of vascular endothelial growth factors indicates the ability of FSH to produce angiogenic factors upon their maturation; whereas, reduction in insulin-like growth factor binding protein (IGFBP3) indicates its increased potential to promote p53-induced apoptosis. Striking similarities in FSH modulation of gene expression were found in primary cultures of human granulosa cells obtained from IVF patients although these cells expressed only 1% of FSH receptor compared with immortalized rat cells, as indicated by microarray technique, which probably is in the normal range of expression of this receptor in nontransformed cells. These findings should increase our understanding of the mechanism of FSH action in stimulating development of the ovarian follicular cells, of intracellular and intercellular communication, and of increasing the potential of ovarian follicular cells to undergo apoptosis during the process of selection of the dominant follicle.

Novel genes regulated by gonadotropins in granulosa cells: new perspectives on their physiological functions

Follicular stimulating hormone (FSH) is a key hormone secreted from the pituitary, which controls the development of the follicle-enclosed oocytes in the mammalian ovary by interacting with specific receptors located exclusively on granulosa cells. Its biological activity involves stimulation of intercellular communication and upregulation of steroidogenesis, yet the entire spectrum of genes which are regulated by FSH are not fully characterized. We have established rat and human FSH responsive granulosa cell lines, which express FSH receptors at 20-times higher rates compared to primary cells. Since the lines are monoclonal, they are expected to have a homogeneous composition of RNA among the entire cell population, which increases the probability of yielding a distinct view of genes modulated by FSH eliminating the possibility of other cell types contamination. Using Affymetrix DNA microarrays to uncover novel FSH-regulated genes, we discovered genes not reported earlier to be regulated by FSH. These include genes coding for (1) proteases; (2) growth factors and cytokines; (3) proteins involved in intercellular communication and connection with the nervous system; (4) protein phosphatases and kinases; (5) anti oxidants and anti-toxicants; (6) G-coupled proteins. These findings can deepen our understanding in the mechanism of FSH action in stimulation of the development of the ovarian follicular cells, in the modulation of ovarian intracellular and intercellular communication and in the process of selection of the dominant follicle. When human granulosa cells, obtained from in vitro fertilization patients were exposed to either hLH- or hFSH stimulation and mRNAs of these cells were analyzed by DNA microarrays, novel genes, similar to those found modulated by FSH in FSH responsive cell lines, were discovered in the human primary cells. This suggests that the immortalized cell systems established in our laboratory could serve as a useful system expanding the spectrum of authentic genes modulated by gonadotropin stimulation in normal ovarian function and in ovarian malfunction.

Stimulation of apoptosis in human granulosa cells from in vitro fertilization patients and its prevention by dexamethasone: involvement of cell contact and bcl-2 expression

Human granulosa cells obtained from in vitro fertilization patients are highly luteinized, but can still be stimulated by LH/cAMP for production of progesterone. This stimulation involved enhancement of apoptosis. Incubation of the cells with dexamethasone (Dex) reduced the apoptotic incidence compared with nontreated cells and completely abolished the increase in apoptosis stimulated by LH or forskolin, concomitantly with a pronounced increase in progesterone production. Organization of the actin cytoskeleton was dramatically reduced after LH/forskolin stimulation. In contrast, Dex prevented disorganization of the actin filament networks. LH and forskolin also decreased the organization of gap junctions, which could be prevented by Dex. However, the intracellular level of connexin 43 was elevated in the presence of LH, forskolin, and Dex. Endogenous levels of the survival gene protein Bcl-2 were significantly elevated in all cultures treated with Dex compared with either nonstimulated cultures or cultures stimulated with LH and forskolin. Our data suggest that LH/cAMP can stimulate steroidogenesis even during the initial stage of apoptosis of human granulosa cells, whereas Dex, which blocks apoptosis, could further elevate progesterone production. Moreover, the integrity of gap junctions and the actin cytoskeleton as well as elevated levels of Bcl-2 may play an important role in the suppression of apoptosis of human granulosa cells.

Effects of ovarian theca cells on apoptosis and proliferation of granulosa cells: changes during bovine follicular maturation

We have investigated the role of theca cells in the control of apoptosis and proliferation of granulosa cells during bovine ovarian follicular development using a coculture system in which granulosa and theca cells were grown on opposite sides of a collagen membrane. A DNA fluorescence flow cytometry was used to determine the extent of apoptosis and proliferation in populations of granulosa cells. When granulosa cells were isolated from small follicles (3-5 mm), the percentage of apoptotic cells gradually increased by 1.8-fold during the 3 days of culture. This change was reduced (3.1-fold) by the presence of theca cells. When the cells were isolated from large follicles (15-18 mm), the percentage of apoptotic granulosa cells was gradually reduced (3.4-fold) during the 3 days of culture in single-cultured groups. The percentage of apoptosis on Day 1 was reduced (1.6-fold) by the presence of theca cells. However, such an effect was not detected on Days 2 and 3 of the culture. Theca cells did not affect the proliferation of granulosa cells obtained from either small or large follicles. The present study suggests that theca cells regulate the fate of granulosa cells throughout the follicular maturation process by secreting factors that suppress apoptosis.

Matrix metalloproteinase expression and activity following prostaglandin F(2 alpha)-induced luteolysis

Luteal tissue contains matrix metalloproteinases (MMPs) that cleave specific components of the extracellular matrix (ECM) and are inhibited by tissue inhibitors of metalloproteinases (TIMPs). We previously reported a decrease in luteal TIMP-1 within 15 min of prostaglandin F(2 alpha) (PGF(2 alpha))-induced luteolysis. An increase in the MMP:TIMP ratio may promote ECM degradation and apoptosis, as observed in other tissues that undergo involution. The objectives of these experiments were to determine whether 1) PGF(2 alpha) affects expression of mRNA encoding fibrillar collagenases (MMP-1 and -13), gelatinases A and B (MMP-2 and -9), membrane type (mt)-1 MMP (MMP-14), stromelysin (MMP-3), and matrilysin (MMP-7), and 2) PGF(2 alpha) increases MMP activity during PGF(2 alpha)-induced luteolysis in sheep. Corpora lutea (n = 3-10/time point) were collected at 0, 15, and 30 min and 1, 2, 4, 6, 12, 24, and 48 h after PGF(2 alpha) administration. Northern blot analysis confirmed the presence of all MMPs except MMP-9. Expression of mRNA for the above MMPs (except MMP-2) increased significantly (P < 0.05) by 30 min, and all MMPs increased significantly (P < 0.05) by 6 h after PGF(2 alpha) administration. Expression of MMP-14 mRNA increased significantly (P < 0.05) by 15 min post-PGF(2 alpha) and remained elevated through 48 h. MMP activity in luteal homogenates (following proenzyme activation and inactivation of inhibitors) was increased significantly (P < 0.05) by 15 min and remained elevated through 48 h post-PGF(2 alpha). MMP activity was localized (in situ zymography) to the pericellular area of various cell types in the 0-h group and was markedly increased by 30 min post-PGF(2 alpha). MMP mRNA expression and activity were significantly increased following PGF(2 alpha) treatment. Increased MMP activity may promote ECM degradation during luteolysis.

Basal lamina of ovarian follicle regulates an inward Cl(-) current in differentiated granulosa cells

Patch-clamp experiments were conducted to study the effects of basal lamina (basement membrane) of preovulatory chicken ovarian follicle on membrane currents in differentiated chicken granulosa cells in a homologous system. The membrane capacitance (measure of total membrane area) was smaller in cells cultured on intact basal lamina than that of control cells. The granulosa cells expressed outward and two inward currents. A small fraction of the cells (3%) expressed only a transient fast-activating and -inactivating inward current carried by Ca(2+). The majority of the cells, however, expressed a slowly activating and inactivating inward current (carried by Cl(-)) that was superimposed on the transient Ca(2+) current. All cells expressed an outward current characteristic of the delayed-rectifier K(+) current. The removal of extracellular Ca(2+) led to elimination of the slow inward Cl(-) current, indicating that it is a Ca(2+)-dependent Cl(-) current. Both peak amplitude and current density of the inward Cl(-) current were significantly lower in cells cultured on freshly isolated intact basal lamina (or basal lamina stored at 4 degrees C for 12 mo) than those of control cells; however, basal lamina had no significant effect on the density of the outward current. Similar to the observations made for intact basal lamina, solubilized basal lamina suppressed the inward Cl(-) current in differentiated granulosa cells. These data show that homologous basal lamina modulates a Ca(2+)-dependent Cl(-) current in differentiated granulosa cells. These findings provide a partial explanation for the mechanisms that subserve the reported effects of basal lamina (basement membrane) on the metabolic functions of differentiated granulosa cells.

Effect of basal lamina of ovarian follicle on T- and L-type Ca(2+) currents in differentiated granulosa cells

Patch clamp experiments were conducted to study the effects of basal lamina (basement membrane) of chicken ovarian follicle on membrane Ca(2+) currents in differentiated chicken granulosa cells in a homologous system. The whole cell patch clamp technique was used to simultaneously monitor membrane capacitance (an indirect measure of total cell surface area) and currents flowing through voltage-dependent Ca(2+) channels (using Ba(2+) as the charge carrier). Membrane capacitance was smaller in cells incubated on intact basal lamina than in control cells (incubated on tissue culture-treated plastic substratum). Granulosa cells expressed both T- and L-type Ca(2+) currents, and the amplitudes of the currents in cells incubated on intact basal lamina were significantly lower than those of control cells. Also, granulosa cells incubated on intact basal lamina were found to have significantly lower T- or L-type Ca(2+) current densities than control cells. Intact basal lamina that had been stored for 12 mo produced effects on T- and L-type Ca(2+) currents similar to those caused by freshly isolated basal lamina. The basal lamina was solubilized completely in one step and used to coat glass coverslips (uncoated glass coverslips served as controls). Granulosa cells incubated on coverslips precoated with solubilized basal lamina assumed spherical shape similar to those incubated on intact basal lamina. Similar to the observations made for intact basal lamina, the solubilized basal lamina suppressed T- and L-type Ca(2+) currents in the differentiated granulosa cells. Moreover, fibronectin, laminin, and type IV collagen, obtained from commercial sources, attenuated T- and L-type Ca(2+) currents in the differentiated granulosa cells. This interplay between basal lamina and Ca(2+) currents may be one mechanism that subserves the effects of the matrix material on metabolic functions of granulosa cells.

Leptin attenuates follicular apoptosis and accelerates the onset of puberty in immature rats

Human and rat granulosa cells express receptors to leptin which synergies with glucocorticoid hormones in stimulation of ovarian steroidogenesis. To examine whether leptin affects follicular development and maturation, we injected recombinant ovine leptin (300 ng-10 microg/animal) daily to immature 21 day-old female rats. Non-treated rats reached puberty at 44.5+/-1.6 (n=9) days. In contrast, in leptin treated animals, puberty was reached at 34.5+/-1.6 (n=9) days. Ovarian sections revealed hypertrophy of granulosa cells in leptin treated animals. Moreover, the number of ovulations was 2-fold higher in the treated animals compared to controls (3-4 ovulations versus 7-8 on the first three estrous cycles, P<0.001). Leptin dramatically reduced incidence of follicular apoptosis measured by TUNEL, and was already evident after 7 days of leptin injection (12% of apoptosis in leptin treated group compared to 52% in controls, P<0.001). Maximal protection against apoptosis was achieved at 1-3 microg leptin/animal. The levels of FSH, LH, progesterone and the steroidogenic factors ADX and STAR were elevated earlier in development in the leptin treated animals compared to control animals which is in line with the achievement of early puberty in the leptin treated animals compared to non treated ones. To reveal whether modulation of death and survival genes is involved in leptin attenuation of follicular apoptosis, we examined the expression of the survival gene Bcl-2 and the death gene Bax in Western blots of ovarian homogenates. There was a pronounced elevation in Bcl-2 expression during 7-14 days of leptin injections up to 16.3-fold (P<0.001) compared to Bcl-2 expression in controls. Bax expression was elevated only 3.4 fold (P<0.001), leading to an increase in the Bcl-2/Bax ratio of 4.7 fold (P<0.001). Expression of the tumor suppressor gene p 53 and the oncogene Mdm2 did not change significantly. Our data suggests that leptin may be involved in accelerating follicular maturation by attenuating follicular atresia and increasing the ratio of Bcl-2/Bax.

Dependence on prolactin of the luteolytic effect of prostaglandin F2alpha in rat luteal cell cultures

Luteal regression is a multistep, prolonged process, and long-term luteal cultures are required for studying it in vitro. Cell suspensions from ovaries of superovulated rats were enriched with steroidogenic cells, seeded on laminin or fibronectin, and maintained in defined medium for up to 10 days. Progesterone secretion was much lower than that of 20alpha-dihydroprogesterone, a product of 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD). Prolactin added throughout the incubation period gradually increased the percent progesterone out of total progestins to fourfold, while reducing 20alpha-HSD mRNA by 73%. Luteinizing hormone accelerated the establishment of higher percent progesterone by prolactin but by itself had no effect. Prolactin did not increase total progestin production or cytochrome P450 side-chain cleavage (P450(scc)) mRNA. Cell viability was unaffected by prolactin and/or LH. Prostaglandin F2alpha (PGF2alpha) was added 7-8 days after seeding. In prolactin-treated cells, PGF2alpha reduced steroidogenesis after 4-45 h, and at 45 h total progestins and P450(scc) mRNA were reduced by 45%. At 8-45 h PGF2alpha reduced the percent progesterone out of total progestins, and at 45 h 20alpha-HSD mRNA was doubled. In contrast, in prolactin-deprived cultures, PGF2alpha had little effect on total progestins or 20alpha-HSD mRNA but doubled P450(scc) mRNA. Phospholipase C activity was stimulated by PGF2alpha regardless of prolactin. Thus, when prolactin-treated, our cultures are a good model for mature corpora lutea challenged with PGF2alpha; the finding that without prolactin PGF2alpha has an alternative set of actions could help in identifying the signaling pathways of PGF2alpha responsible for its luteolytic effects.

Apoptosis of granulosa cells and female infertility in achondroplastic mice expressing mutant fibroblast growth factor receptor 3G374R

Fibroblast growth factors play an important role in the control of ovarian folliculogenesis, but the complete repertoire of ovarian receptors which can transduce the fibroblast growth factor signals and their precise localization in the ovary have not yet been characterized. The most common form of inherited human dwarfism results from a point mutation in the transmembrane region of fibroblast growth factor receptor 3. A mouse model for achondroplasia was generated by introducing the human mutation (glycine 380-arginine) into the mouse fibroblast growth factor receptor 3 (G374R) by a "knock-in" approach using gene targeting leading to a constitutively active receptor. This resulted in the development of dwarf mice that share many features with human achondroplasia. Here we report that female (fibroblast growth factor receptor 3 G374R) dwarf mice become infertile. While no significant changes were observed in the anatomical and histological appearance of ovaries of 3-wk-old dwarf mice, a dramatic difference was observed in ovaries of 3-month-old mice. The normal ovary consists mainly of healthy corpora lutea and follicles at different stages of development, whereas the ovaries of the dwarf mice remain small and contain mainly follicles with a progressive apoptosis in the granulosa cells, and no corpora lutea could be observed. The levels of LH, FSH, and progesterone were lower by 72.3%, 38.0%, and 40.0%, respectively, in the blood of the dwarf mice compared with normal mice, and the total bioactivity of pituitary FSH and LH was lower by 65.6% and 79.6%, respectively, in the dwarf mice compared with normal mice. However treatment with PMSG and human CG of the dwarf mice led to rapid follicular development and formation of corpora lutea. Interestingly, the expression of the tumor suppressor gene p53 was increased dramatically in ovaries of the dwarf mice. The presence of the fibroblast growth factor receptor 3 cellular receptors in both normal and dwarf animals was demonstrated by Western blot and immunostaining. However, the distribution of the fibroblast growth factor receptors in the two strains shows significant differences. In the normal ovaries fibroblast growth factor receptor 3 was homogeneously distributed on the cell membrane of the granulosa cells and was absent in theca as well as corpora lutea cells, whereas in dwarf mice ovaries it was highly clustered on granulosa cells and very often appears in endocytic vesicles. Aged oocytes were more frequently observed in preantral follicles of ovaries of the dwarf mice. Nevertheless, oocytes isolated from antral follicles resume their meiotic division at a high percentage, similar to oocytes obtained from normal ovaries. The results imply fibroblast growth factor receptor 3 involvement in the control of follicular development through regulation of granulosa cell growth and differentiation, and that unovulation in the dwarf mice could be overcome in part by administration of exogenous gonadotropins. Moreover, it is suggested that the infertile phenotype is partially due to defects in the pituitary-gonadal axis.

The proteasome inhibitor MG132 promotes accumulation of the steroidogenic acute regulatory protein (StAR) and steroidogenesis

StAR, a protein synthesized in the cytoplasm and subsequently imported into mitochondria, regulates the rate-determining step in steroidogenesis, the transport of cholesterol from the outer to the inner mitochondrial membrane. The active form of StAR is the 37 kDa pre-protein, which has a short half-life. To determine whether proteasomes participate in the turnover of StAR, we incubated primary cultures of preovulatory rat granulosa cells and immortalized human granulosa cells in the presence of MG132, a specific inhibitor to proteasome catalysis. This treatment caused accumulation of StAR in unstimulated cells. Moreover, incubation of the cells with MG132 in the presence of forskolin (FK), luteinizing hormone/chorionic gonadotropin or follicular stimulating hormone augmented the accumulation of both the 37 kDa cytoplasmic protein and the 30 kDa mature mitochondrial protein, compared to cells incubated with FK or the gonadotropic hormones alone. Concomitantly, progesterone production was enhanced. In contrast no elevation in the 37 kDa StAR intracellular levels or progesterone production was observed following incubation of the cells with the cysteine protease inhibitor E-64. The increase of the 37 kDa StAR protein was evident after 15 min and 30 min of incubation with MG132 (143% and 187% of control values, respectively) with no significant elevation of the 30 kDa protein. Accumulation of the intermediate mitochondrial 32 kDa protein was evident after 1-2 h and the accumulation of the 30 kDa protein was evident only after 4 h of incubation with MG132. In contrast, no elevation in adrenodoxin, a component of the cytochrome P450scc enzyme system, was found. These data suggest that StAR protein is either directly or indirectly degraded by the proteasome which may explain, in part, its short half-life. Moreover, it seems that the cytosolic 37 kDa protein, which is responsible for the steroidogenic activity of StAR, is the primary proteasomal substrate and that the inhibition of its degradation by MG132 causes the up-regulation of progesterone production.

Glucocorticoids protect against apoptosis induced by serum deprivation, cyclic adenosine 3',5'-monophosphate and p53 activation in immortalized human granulosa cells: involvement of Bcl-2

Glucocorticoid hormones are known to enhance gonadotropin/cAMP-induced steroidogenesis in rat and human granulosa cells. As glucocorticoids induce apoptosis in numerous cell types, we investigated the role of glucocorticoids in the control of apoptosis in immortalized human granulosa cells (HO-23) transfected with a temperature-sensitive mutant of p53 (Val(135)). When HO-23 were incubated with forskolin in the presence or absence of dexamethasone (Dex) at 32 or 37 C, progesterone production was higher by 4- and 8-fold in the presence of Dex at 37 or 32 C, respectively (P: < 0. 01). The expression of adrenodoxin (ADX), which is an intrinsic part of the cytochrome P450 side-chain cleavage enzyme system, remained the same in the presence or absence of Dex in forskolin-stimulated cells. Dex reduced apoptosis (to 33% of control) in cultures after activation of p53 by shifting the temperature from 37 to 32 C. Moreover, Dex suppressed apoptosis induced by serum deprivation (to 40% of control) or forskolin stimulation (to 28% and 40% at 37 and at 32 C, respectively). The protective effect of Dex on cAMP-, p53-, and serum deprivation-induced apoptosis was confirmed by both 4',6-diamido-2-phenylindole hydrochloride DNA staining and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling with an ED(50) of 7 nM Dex. Hydrocortisone showed a similar antiapoptotic effect. The protective effect of glucocorticoids against apoptosis was completely abolished by RU486 when cells were coincubated with 10 nM Dex and 10-100 nM RU486. The protection against apoptosis by glucocorticoid involved a sharp elevation in intracellular levels of Bcl-2 (3-7.6 fold; P: < 0.01). In contrast to the effect of Dex in the prevention of apoptosis in HO-23 granulosa cells, Dex dramatically stimulated apoptosis by 3-fold in LTR-6 myeloid leukemia cells expressing the same temperature-sensitive mutant (Val(135) p53) and the same amount of glucocorticoid receptor-alpha. Forskolin did not stimulate apoptosis when incubated with these cells. However, it augmented by 1.2-fold the p53-induced apoptosis in cells shifted from 37 to 32 C. Dex further enhanced apoptosis by 1.9-fold in p53-activated cultures (32 C). Incubation of the cells with Dex dramatically reduced Bcl-2 levels to 15% of control at 37 C (P: < 0.01) or 32 C in the presence or absence of forskolin (P: < 0.01). Our data suggest that glucocorticoids exert a protective effect against induced apoptosis in immortalized granulosa cells and a stimulatory effect on apoptosis in myeloid leukemia cells. Moreover, modulation of Bcl-2 levels plays an important role in mediating the glucocorticoid effect on cell survival. The opposite effect of glucocorticoids on Bcl-2 levels in the two cell lines may be due to the different ontogeneses of the two cell types: epithelial for granulosa cells vs. mesenchymal for myeloid cells studied in the present work.

Discoidin domain receptor (DDR) 1 and 2: collagen-activated tyrosine kinase receptors in the cornea

Discoidin domain receptor (DDR) 1 and 2 have recently been found to serve as receptors for several collagen types. These receptors have been found to modulate cell proliferation and metalloprotease expression in response to collagen stimulation. The purpose of this study was to examine expression of DDR1 and DDR2 in the cornea and to determine the effect of several collagen types on proliferation and response to pro-apoptotic cytokines by corneal fibroblasts. DDR1 and DDR2 mRNAs were detected by RT-PCR. Proteins were detected by immunocytochemistry and immunoprecipitation with Western blotting. Cell proliferation in response to acetic acid-solubilized collagen type I, II, IV, IX or X was determined by cell counting. The effect of these collagen types on Fas-stimulating antibody-induced cell death was determined by trypan blue assay. DDR1 and DDR2 mRNAs were detected in each major human cell type of the cornea. Both were also detected in ex vivo human corneal epithelium. DDR1 and DDR2 proteins were detected in all three major cell types in culture and in human corneal tissue. Collagen types I, II, IV, IX and X stimulated proliferation, but had no effect on Fas-mediated apoptosis, of corneal fibroblasts. DDR1 and DDR2 tyrosine kinase receptors are expressed in the cornea. Collagen-stimulated mitosis of corneal fibroblasts in culture is likely mediated by the DDR receptors. Collagen had no effect on Fas-mediated apoptosis of corneal fibroblasts.

Caspase-mediated cleavage of p130cas in etoposide-induced apoptotic Rat-1 cells

Apoptosis causes characteristic morphological changes in cells, including membrane blebbing, cell detachment from the extracellular matrix, and loss of cell-cell contacts. We investigated the changes in focal adhesion proteins during etoposide-induced apoptosis in Rat-1 cells and found that during apoptosis, p130cas (Crk-associated substrate [Cas]) is cleaved by caspase-3. Sequence analysis showed that Cas contains 10 DXXD consensus sites preferred by caspase-3. We identified two of these sites (DVPD(416)G and DSPD(748)G) in vitro, and point mutations substituting the Asp of DVPD(416)G and DSPD(748)G with Glu blocked caspase-3-mediated cleavage. Cleavage at DVPD(416)G generated a 74-kDa fragment, which was in turn cleaved at DSPD(748)G, yielding 47- and 31-kDa fragments. Immunofluorescence microscopy revealed well-developed focal adhesion sites in control cells that dramatically declined in number in etoposide-treated cells. Cas cleavage correlated temporally with the onset of apoptosis and coincided with the loss of p125FAK (focal adhesion kinase [FAK]) from focal adhesion sites and the attenuation of Cas-paxillin interactions. Considering that Cas associates with FAK, paxillin, and other molecules involved in the integrin signaling pathway, these results suggest that caspase-mediated cleavage of Cas contributes to the disassembly of focal adhesion complexes and interrupts survival signals from the extracellular matrix.

MAP kinase pathway signalling is essential for extracellular matrix determined mammary epithelial cell survival

Mammary epithelial cells in primary cell culture require both growth factors and specific extracellular matrix (ECM)-attachment for survival. Here we demonstrate for the first time that inhibition of the ECM-induced Erk 1/Erk 2 (p42/44 MAPK) pathway, by PD 98059, leads to apoptosis in these cells. Associated with this cell death is a possible compensatory signalling through the p38 MAP kinase pathway the inhibition of which, by SB 203580, leads to a more rapid onset of apoptosis. This provides evidence for a hitherto undescribed Erk 1/Erk 2 to p38 MAP kinase pathway 'cross-talk' that is essential for the survival of these cells. The cell death associated with inhibition of these two MAP kinase pathways however, occurred in the presence of insulin that activates the classical PI-3 kinase-dependent Akt/PKB survival signals and Akt phosphorylation. Cell death induced by inhibition of the MAP kinase pathways did not affect Akt phosphorylation and may, thus, be independent of PI-3 kinase signalling.

Effect of basal lamina on progesterone production by chicken granulosa cells in vitro--influence of follicular development

Experiments were conducted in vitro to study the regulation of progesterone production in chicken granulosa cells by homologous basal lamina isolated from preovulatory follicles of chicken ovary. The majority of components of the basal lamina (90-95% by weight) were solubilized with guanidine-HCl (and designated fraction 1); the remaining components were solubilized with beta-mercaptoethanol containing guanidine-HCl (and designated fraction 2). The ability of fraction 1 to regulate progesterone production in granulosa cells obtained from the largest (F(1), mature), third largest (F(3), growing), fifth to seventh largest (F(5-7), growing) follicles and a pool of small yellow follicles (SYF, immature) of chicken ovary was assessed. Granulosa cells isolated from SYF follicles were in the least differentiated (undifferentiated) and those obtained from F(1) follicles were in the most differentiated state. The ability of fraction 1 to regulate progesterone production by chicken granulosa cells was influenced both by the state of cell differentiation and the form of the matrix material (whether solid or liquid). When fraction 1 was added as liquid to the incubation mixture, it promoted progesterone production by granulosa cells at all stages of differentiation; however, it caused a greater relative increase in the amount of progesterone produced by undifferentiated (SYF) and differentiating (F(3)) granulosa cells than by differentiated (F(1)) ones. In the presence of the liquid-form of fraction 1, luteinizing hormone (LH) stimulated progesterone production in differentiated (F(1)) and differentiating (F(5-7)) granulosa cells. Similarly, follicle-stimulating hormone (FSH) stimulated progesterone production by differentiating (F(3)) and undifferentiated (SYF) granulosa cells in the presence of the liquid-form of fraction 1 protein. In culture wells that had been pre-coated with fraction 1 (solid-form), progesterone production by less differentiated (SYF, F(5-7)) granulosa cells was enhanced, whereas progesterone production by differentiated (F(1)) cells was reduced. The solid-form of fraction 1 augmented LH-stimulated progesterone production by less differentiated (F(5-7)) granulosa cells however, it attenuated LH-induced progesterone production in differentiated (F(1)) cells. FSH-promoted progesterone production in granulosa cells from immature follicles (SYF) was augmented by solid-form of fraction 1 whereas the effect of FSH on cells obtained from older follicle (F(3)) was suppressed by solid-form of fraction 1. In experiments in which gonadotropin action was attenuated by solid-form of fraction 1, the amount of progesterone produced in the presence of maximally inhibiting concentrations of fraction 1 protein was greater than control values (no fraction 1, no gonadotropin). These results show that basal lamina of the ovarian follicle can regulate progesterone production by granulosa cells. The data demonstrate that the interactions between the components of basal lamina and LH or FSH on granulosa cell function were dependent on the stage of follicular development and were influenced by the form of the matrix material. It is concluded that the basal lamina of the chicken ovarian follicle is biologically active and regulates granulosa cell function.

Thyrotropin prevents apoptosis by promoting cell adhesion and cell cycle progression in FRTL-5 cells

Apoptosis has been shown to be involved in endocrine tissue homeostasis as well as regression due to hormone deprivation. The goal of this study was to induce apoptosis and to investigate a potential role of TSH as a survival factor in thyroid follicular cells (FRTL-5) in vitro. Our results indicated that FRTL-5 cells underwent anchorage-dependent apoptosis when plated in the absence of serum and hormones, but when the cells became attached to the substrate by addition of TSH in the medium, apoptosis was prevented. The apoptosis was evaluated by positive terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick end labeling staining, typical apoptotic bodies by electron microscopy, DNA ladder by gel electrophoresis, and subdiploidy by propidium iodide-stained flow cytometry. TSH was shown to prevent apoptosis and maintain cell viability. cAMP partly mimicked this effect, which was inhibited by a specific inhibitor of protein kinase A, H-89. While investigating the mechanisms of apoptosis, we observed that the phosphorylated focal adhesion kinase was strengthened by TSH. Furthermore, FRTL-5 cells were found to undergo growth arrest in the G1 phase in the absence of TSH, accompanied by an elevated level of cyclin-dependent kinase inhibitor, p27, and a decreased level of cyclin D. In contrast, TSH promoted transition from G1 to S phase by decreasing P27 protein and increasing cyclin D expression. We concluded that in addition to regulating growth and differentiation, TSH may function as a survival factor in thyroid cells by preventing anchorage-dependent apoptosis in FRTL-5 cells partly via the cAMP pathway.

Cell-based gene transfer to the pulmonary vasculature: Endothelial nitric oxide synthase overexpression inhibits monocrotaline-induced pulmonary hypertension

To circumvent the problems of in vivo transfection and avoid the use of viral vectors or proteins, we sought to establish whether smooth-muscle cells (SMCs) transfected ex vivo could be delivered via the systemic venous circulation into the pulmonary bed to achieve local transgene expression in the lung. Primary cultures of pulmonary artery SMCs from Fisher 344 rats were labeled with a fluorescent, membrane-impermeable dye chloromethyl trimethyl rhodamine or transfected with the beta-galactosidase (betaGal) reporter gene under the control of the cytomegalovirus (CMV) enhancer/promoter (pCMV-beta). Transfected or labeled SMCs (5 x 10(5) cells/animal) were delivered to syngeneic recipient rats by injection into the jugular vein; the animals were killed at intervals between 15 min and 2 wk; and the lungs, spleens, kidneys, and skeletal muscle were excised and examined. At 15 min after transplantation, injected cells were detected mainly in the lumen of small pulmonary arteries and arterioles, often in groups of three or more cells. After 24 h, labeled SMCs were found incorporated into the vascular wall of pulmonary arterioles, and transgene expression persisted in situ for 14 d with no evidence of immune response. Using simple geometric assumptions, it was calculated that approximately 57 +/- 5% of the labeled cells reintroduced into the venous circulation could be identified in the lungs after 15 min, 34 +/- 7% at 48 h, 16 +/- 3% at 1 wk, and 15 +/- 5% at 2 wk. Similar results were observed using cells transfected with the reporter gene betaGal. To determine whether this method of gene transfer could prove effective in inhibiting the development of pulmonary vascular disease, pulmonary artery SMCs were transfected with either the full-length coding sequence of endothelial nitric oxide synthase (NOS) under the control of the CMV enhancer/promoter or with the control vector (pcDNA3.1) and injected simultaneously with the pulmonary endothelial toxin monocrotaline. At 28 d after injection the right ventricular systolic pressure was significantly decreased from 50 +/- 4 mm Hg in animals injected with the null-transfected cells to 33 +/- 3 mm Hg in animals injected with the NOS-transfected cells (P < 0.01). These results suggest that a cell-based strategy of ex vivo transfection may provide an effective nonviral approach for the selective delivery of foreign transgenes to pulmonary microvessels in the treatment of pulmonary vascular disease.

Three-dimensional environments preserve extracellular matrix compartments of ovarian follicles and increase FSH-dependent growth

In this study we performed a systematic comparative analysis of two culture environments-flat/adhesive liquid and three-dimensional collagen gel-upon in vitro ovarian follicle development. We paid particular attention to the effects of in vitro environments upon the preservation of follicular structure and of peri- and intra-follicular extracellular matrix. We show that flat/adhesive environment leads to an obvious distortion of follicle morphology, marked extracellular matrix modifications and high rates of spontaneous, i.e., FSH-independent, follicle disruption. In contrast, three-dimensional collagen gel environments are able to maintain follicular structure with an in vivo-like basal lamina architecture, minimizing spontaneous disruption. Follicle distortions found in flat/adhesive culture systems include a pronounced flattening, causing the follicle horizontal diameters not to adequately reflect follicle volume. Our volume data, based on three-axis follicle diameter measurements, indicate that three-dimensional collagen gel environments increase follicle growth, particularly in response to FSH. This study demonstrates that preservation of both peri- and intra-follicular extracellular matrix compartments during the in vitro growth and differentiation of ovarian follicles is highly desirable, and is now possible through the use of appropriate three-dimensional collagen gel culture environments. This system allows a better understanding of the specific roles played by each of the follicle compartments during development.

Induction of apoptosis in luteinized granulosa cells by the MAP kinase kinase (MEK) inhibitor PD98059

Our objective is to test the hypothesis that inhibition of mitogen-activated protein (MAP) kinase kinase (MEK) with PD98059 in human luteinized granulosa cells will block epidermal growth (EGF)-stimulated MAP kinase activity and induce apoptosis. Luteinized granulosa cells from human in vitro fertilization aspirates were cultured and treated with the following: (1) vehicle; (2) PD98059; (3) EGF; (4) PD98059 + EGF. Treatment with PD98059 suppressed MAP kinase activity, inhibited MAP kinase phosphorylation by Western blot analysis, blocked nuclear translocation of phosphorylated MAP kinase by confocal microscopy, and increased percentages of subdiploid apoptotic nuclei by flow cytometry. Our data are the first evidence that a relationship may exist between the MAP kinase pathway and control of apoptosis in human luteinized granulosa cells. These results support the hypothesis that suppression of the MAP kinase pathway may lead to apoptosis in these cells.

Crosstalk Among Multiple Signaling Pathways Controlling Ovarian Cell Death

Ovarian cell death is an essential process for the homeostasis of ovarian function in human and other mammalian species. It ensures the selection of the dominant follicle and the demise of excess follicles. In turn, this process minimizes the possibility of multiple embryo development during pregnancy and assures the development of few but healthy embryos. Degeneration of the old corpora lutea in each estrous/menstrual cycle by programmed cell death is essential to maintain the normal cyclicity of ovarian steroidogenesis. Although there are multiple pathways that can determine cell death or survival, crosstalk among endocrine, paracrine and autocrine factors, as well as among protooncogenes, tumor suppressor genes, survival genes and death genes, plays an important role in determining the fate of ovarian somatic and germ cells. The establishment of immortalized rat and human steroidogenic granulosa cell lines and the investigation of pure populations of primary granulosa cells allows systematic studies of the mechanisms that control steroidogenesis and apoptosis of granulosa cells. These cells are the most abundant type of somatic follicular cell. Moreover, crosstalk between p53 and extracellular matrix components such as laminin, fibronectin and basic fibroblast growth factor, between cAMP- and p53-generated signals and between steroid hormones and Bcl-2, can explain some of the fine tuning that controls ovarian steroidogenesis and apoptosis. Further study of the mechanisms of ovarian cell death will lead to a better understanding of the processes involved and permit the formulation of novel strategies for the treatment of ovarian malfunctions, such as polycystic ovarian syndrome and ovarian cancer.

Immunolocalization and expression of the steroidogenic acute regulatory protein during the transitional stages of rat follicular differentiation

This study was designed to determine the pattern of expression and cellular distribution of the steroidogenic acute regulatory protein (StAR) during the transitional stages of follicular differentiation in rat ovary. Using specific antisera against the StAR, immunohistochemistry, Western blotting, and immunoprecipitation analyses provide evidence confirming the localization and expression of StAR in granulosa cells (GCs) of juvenile rat ovaries before and after PMSG treatment. The results also show that StAR expression occurs in theca intersitial cells surrounding preantral, antral, and larger antral follicles in adult diestrous ovaries. Furthermore, we have demonstrated heterogenous StAR immunoreactivity in the granulosa cell layers and cells of the corpora lutea. A novel finding presented here is that, during ongoing growth and differentiation of the follicle, the immunoreactivity of StAR tends to shift from the GC of early antral follicles to the theca cell layers in the adult. The spatiotemporal changes or shifts in StAR expression and cellular localization also coincide with the appearance of more acidic isoforms of the 30-kD protein, as determined by two-dimensional gel electrophoresis. Although the functional implications of these observations remain unclear, the acute temporal changes in StAR expression and localization may not only reflect the dynamic steroidogenic capacity of follicular cells but may also support a possible role for FSH in the induction of follicular maturation.

Functionality and cell anchorage dependence of the African swine fever virus gene A179L, a viral bcl-2 homolog, in insect cells

The African swine fever virus gene A179L has been shown to be a functional member of the ced9/bcl-2 family of apoptosis inhibitors in mammalian cell lines. In this work we have expressed the A179L gene product (p21) under the control of the baculovirus polyhedrin promoter using a baculovirus system. Expression of the A179L gene neither altered the baculovirus replication phenotype nor delayed the shutoff of cellular protein synthesis, but it extended the survival of the infected insect cells to very late times postinfection. The increase in cell survival rates correlated with a marked apoptosis reduction after baculovirus infection. Interestingly, prevention of apoptosis was observed when recombinant baculovirus infections were carried out in monolayer cell cultures but not when cells were infected in suspension, suggesting a cell anchorage dependence for p21 function in insect cells. Cell survival was enhanced under optimal conditions of cell attachment and cell-to-cell contact as provided by extracellular matrix components or poly-D-lysine. Since it was observed that cytoskeleton organization varied depending on culture conditions of insect cells (grown in monolayer versus grown in suspension), these results suggested that A179L might regulate apoptosis in insect cells only when the cytoskeletal support of intracellular signaling is maintained upon cell adhesion. Thus, cell shape and cytoskeleton status might allow variations in intracellular transduction of signals related to cell survival in virus-infected cells.