Androgen receptor gene deficiency results in the reduction of steroidogenic potential in porcine luteal cells

Luteal steroidogenesis is critical to implantation and pregnancy maintenance in mammals. The role of androgen receptors (AR) in the progesterone (P4) producing luteal cells of porcine corpus luteum (CL) remains unexplored. The aim of the present study was to establish AR gene knock out (KO) porcine luteal cell culture system model by CRISPR/Cas9 genome editing technology and to study the downstream effects of AR gene deficiency on steroidogenic potential and viability of luteal cells. For this purpose, genomic cleavage detection assay, microscopy, RT-qPCR, ELISA, annexin, MTT, and viability assay complemented by bioinformatics analysis were employed. There was significant downregulation (p < 0.05) in the relative mRNA expression of steroidogenic marker genes STAR, CYP11A1, HSD3B1 in AR KO luteal cells as compared to the control group, which was further validated by the significant (p < 0.05) decrease in the P4 production. Significant decrease (p < 0.05) in relative viability on third passage were also observed. The relative mRNA expression of hypoxia related gene HIF1A was significantly (p < 0.05) downregulated in AR KO luteal cells. Protein-protein interaction analysis mapped AR to signaling pathways associated with luteal cell functionality. These findings suggests that AR gene functionality is critical to luteal cell steroidogenesis in porcine.

Genome-wide methylation profiling in granulosa lutein cells of women with polycystic ovary syndrome (PCOS)

Polycystic Ovary Syndrome (PCOS) is the most common endocrine disorder amongst women of reproductive age, whose aetiology remains unclear. To improve our understanding of the molecular mechanisms underlying the disease, we conducted a genome-wide DNA methylation profiling in granulosa lutein cells collected from 16 women suffering from PCOS, in comparison to 16 healthy controls. Samples were collected by follicular aspiration during routine egg collection for IVF treatment. Study groups were matched for age and BMI, did not suffer from other disease and were not taking confounding medication. Comparing women with polycystic versus normal ovarian morphology, after correcting for multiple comparisons, we identified 106 differentially methylated CpG sites with p-values <5.8 × 10^-8 that were associated with 88 genes, several of which are known to relate either to PCOS or to ovarian function. Replication and validation of the experiment was done using pyrosequencing to analyse six of the identified differentially methylated sites. Pathway analysis indicated potential disruption in canonical pathways and gene networks that are, amongst other, associated with cancer, cardiogenesis, Hedgehog signalling and immune response. In conclusion, these novel findings indicate that women with PCOS display epigenetic changes in ovarian granulosa cells that may be associated with the heterogeneity of the disorder.

FSH up-regulates angiogenic factors in luteal cells of buffaloes

Follicle-stimulating hormone has been widely used to induce superovulation in buffaloes and cows and usually triggers functional and morphologic alterations in the corpus luteum (CL). Several studies have shown that FSH is involved in regulating vascular development and that adequate angiogenesis is essential for normal luteal development. Angiogenesis is regulated by many growth factors, of which vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2) have an established central role. Therefore, we have used a combination of in vitro and in vivo studies to assess the effects of FSH on the expression of VEGF and FGF2 and their receptors in buffalo luteal cells. The in vivo model consisted of 12 buffalo cows, divided into control (n = 6) and superovulated (n = 6) groups, and CL samples were collected on day 6 after ovulation. In this model, we analyzed the gene and protein expression of FGF2 and its receptors and the protein expression of VEGFA systems with the use of real-time PCR, Western blot analysis, and immunohistochemistry. In the in vitro model, granulosa cells were collected from small follicles (diameter, 4-6 mm) of buffaloes and cultured for 4 d in serum-free medium with or without FSH (10 ng/mL). To induce in vitro luteinization, LH (250 ng/mL) and fetal bovine serum (10%) were added to the medium, and granulosa cells were maintained in culture for 4 d more. The progesterone concentration in the medium was measured at days 4, 5, and 8 after the beginning of cell culture. Cells were collected at day 8 and subjected to real-time PCR, Western blot analysis, and immunofluorescence for assessment of the expression of FGF2, VEGF, and their receptors. To address the percentage of steroidogenic and growth factor-expressing cells in the culture, flow cytometry was performed. We observed that in superovulated buffalo CL, the FGF2 system mRNA expression was decreased even as protein expression was increased and that the VEGF protein was increased (P < 0.05). In vitro experiments with granulosa cells showed an increase in the mRNA expression of VEGF and FGF2 and its receptors 1 and 2 and protein expression of VEGF, kinase insert domain receptor, FGF receptor 2, and FGF receptor 3 in cells treated with FSH (P < 0.05), in contrast to the in vivo experiments. Moreover, the progesterone production by FSH-treated cells was elevated compared with untreated cells (P < 0.05). Our findings indicate that VEGF, FGF2, and their receptors were differentially regulated by FSH in vitro and in vivo in buffalo luteal cells, which points toward a role of CL environment in modulating cellular answers to gonadotropins.

The relationship between the production and the anti-gonadotrophic action of prostaglandin F 2 alpha in luteal cells from the marmoset monkey (Callithrix jacchus) in the early and mid-luteal phase

To address the potential luteolytic role for prostaglandin F(2 alpha) (PGF(2 alpha)) in the corpus luteum of the common marmoset monkey (Callithrix jacchus), the ability of marmoset luteal cells, maintained in monolayer culture, to produce PGF(2 alpha) was determined in vitro in the presence and absence of human chorionic gonadotrophin (hCG) and other established pharmacological modulators of PGF(2 alpha) synthesis. We also assessed the effects of the PGF(2 alpha) analogue, cloprostenol, on progesterone output from luteal cells isolated in the early luteal phase versus the mid-luteal phase (days 3 and 14 post ovulation, respectively). Cloprostenol had no effect on progesterone output from luteal cells isolated on day 3 of the luteal phase, whereas it significantly inhibited both basal and hCG-stimulated progesterone synthesis by day 14 luteal cells during the culture period 48-72 h (P<0.001). Intra-luteal PGF(2 alpha) concentrations were 5-fold higher in luteal cells isolated in the early luteal phase than in mid-luteal phase cells (16.5+/-3.5 versus 3.5+/-0.6 pmol/10(5) cells). While PGF(2 alpha) production was unaffected by hCG in vitro, it was decreased by indomethacin (1000 ng/ml) (P<0.05) and stimulated by the calcium ionophore A23187 (10 micromol/l) (P<0.05) in luteal cells from both stages of the luteal phase. Phospholipase A(2) did not influence PGF(2 alpha) production by day 3 luteal cells whereas at 10 IU/ml, it significantly stimulated PGF(2 alpha) production by day 14 luteal cells (P<0.05). Hence, the timing of luteolysis in the common marmoset monkey appears to involve changes in both the luteal cell response to and production of PGF(2 alpha).

Endothelin-1, endothelin converting enzyme-1 and endothelin receptors in the porcine corpus luteum

Porcine corpora lutea (CL) fail to show a luteolytic response to prostaglandin-F-2alpha (PGF-2alpha) (ie, luteolytic sensitivity [LS]) until about day 12-13 of the estrous cycle. Although little is known of the control of LS in any species, endothelin-1 (EDN1) is believed to play a role in LS control in ruminants. Therefore, we measured mRNA and protein expression and examined the cellular localization of EDN1 precursor (pre-pro EDN1, or ppEDN1), EDN-converting enzyme-1 (ECE1), and EDN receptors (A, EDNRA and B, EDNRB) in porcine CLs collected on days 4, 7, 10, 13, and 15 of the estrous cycle to look for differences between CLs displaying (days 13-15) versus those lacking (days 4-10) LS. Abundance of ppEDN1 mRNA was greatest (and significant vs all other days) on day 7 of the cycle, whereas EDN1 protein expression did not vary during the cycle and was localized exclusively to endothelial cells (EC). Abundance of ECE1 mRNA was also greatest on day 7 (vs all other days), but ECE1 protein was significantly elevated on day 10 (vs day 4) and was immunolocalized to ECs and large luteal cells (LLC). Abundance of EDNRA mRNA was also maximal on day 7 (vs all other days) of the cycle, whereas EDNRA protein expression was not significantly changed during the cycle and was observed in LLCs, ECs, and small luteal cells (SLC). On day 13, EDNRB mRNA was significantly decreased (versus day 7). Expression of EDNRB protein was decreased on day 10 (versus all other days), and on days 13-15 (vs day 4), and was primarily localized to ECs. In conclusion, the observed elevation in ECE1 protein concentrations on day 10 and the presence of EDNRA on LLC suggests a possible role for EDN1 (resulting from the actions of ECE1) acting via EDNRA in the control of LS in the pig.

A Quantitative Study of Blood Capillary Formation (Angiogenesis) Concomitant with Parenchymal Tissue Differentiation

Examination of the rat corpus luteum (CL) provided quantitative data supporting adaptation of the developing vasculature to maximise efficient acceptance of steroids secreted from the luteal cells. Numbers of endothelial cells (ECs) significantly increased during the initial formation of the CL, followed by a further significant proliferation from day 10 to day 16 when there was maximal growth of the CL. As a consequence, there was significant growth of the vascular compartment during this time interval. The final phase of expanding endothelium (days 10 to 16) was a result of increased ECs volume with elongation of the EC in the direction of growth. Continued increase in capillary surface area and a corresponding marked reduction in diffusion distance between LC and ECs evidenced adaptation of the developing microvasculature to enable efficient endocrine function by day 16, when steroid secretion is maximal. Furthermore, from day 1 to day 3 there was close apposition of pericytes to the endothelium, suggesting the important role of pericytes in the initiation of angiogenesis. However, this degree of association was reduced from day 10 to day 16 and was a consequence of expansion of the EC cytoplasm to provide a greater surface area for transport of steroids.

KIT receptor-positive cells in the bovine corpus luteum are primarily theca-derived small luteal cells

The tyrosine kinase KIT receptor, the protooncogene CD117, plays a key role in growth and maturation of oocytes and follicles. Relevant data are sparse for the corpus luteum (CL). We first confirmed the presence ofKITmRNA and KIT protein in bovine CL homogenates. We then localized KIT-positive (KIT+) cells in CL sections by immunohistochemistry. At the CL stage of early development, the former theca transforming into capsule/septa showed a strong band-like KIT+ immunoresponse. In addition, CD45+ leukocytes in septa included subpopulations of CD45+/KIT+ and CD14+/KIT+ leukocytes as validated by double immunofluorescence localization. At the early secretory stage, KIT+ cells appeared within the septa/capsule region and in the periphery of the CL parenchyma, there forming a complex network. This was separate from the capillary bed as determined by double staining for CD117 and FVIII-related endothelial cell antigen (FVIIIr). The KIT+ network coincided with cells positive for cytochrome P450 17α-hydroxylase, a thecal cell-specific enzyme. The late secretory stage was defined by an advanced manifestation of the KIT+ network in the CL periphery. At the stage of regression, the KIT+ network was absent. The CL of pregnancy expressed high levels ofKITmRNA and KIT protein uniformly throughout pregnancy. The KIT+ immunolocalization revealed small fibroblast-like cells, luteal cells with granules, and clusters of large luteal cells with staining of the cell membrane. We conclude that a majority of KIT+ cells in the bovine CL are primarily theca-derived small luteal cells, and that a minority represent KIT+ leukocytes, in some cases KIT+ monocytes.

11beta-Hydroxysteroid dehydrogenase expression and activities in bovine granulosa cells and corpora lutea implicate corticosteroids in bovine ovarian physiology

Cortisol-cortisone metabolism is catalysed by the bi-directional NADP(H)-dependent type 1 11beta-hydroxysteroid dehydrogenase (11betaHSD1) enzyme and the oxidative NAD(+)-dependent type 2 11betaHSD (11betaHSD2). This study related the expression of 11betaHSD1 and 11betaHSD2 enzymes (mRNA and protein) to net 11-ketosteroid reductase and 11beta-dehydrogenase (11beta-DH) activities in bovine follicular granulosa and luteal cells. Granulosa cells were isolated from follicles of < 4, 4-8, > 8 and > 12 mm in diameter in either the follicular or luteal phase of the ovarian cycle. Luteal cells were obtained from corpora lutea (CL) in the early non-pregnant luteal phase. Enzyme expression was assessed by reverse transcription-PCR and western blotting, while enzyme activities were measured over 1 h in cell homogenates using radiometric conversion assays with 100 nM [(3)H]cortisone or [(3)H]cortisol and pyridine dinucleotide cofactors. Irrespective of follicle diameter, the expression of 11betaHSD2 and NAD(+)-dependent oxidation of cortisol predominated in granulosa cells harvested in the follicular phase. In contrast, in granulosa cells obtained from luteal phase follicles and in bovine luteal cells, expression of 11betaHSD1 exceeded that of 11betaHSD2 and the major enzyme activity was NADP(+)-dependent cortisol oxidation. Increasing follicular diameter was associated with progressive increases in expression and activities of 11betaHSD2 and 11betaHSD1 in follicular and luteal phase granulosa cells respectively. In follicular phase granulosa cells from antral follicles < 12 mm, 11betaHSD1 migrated with a molecular mass of 34 kDa, whereas in the dominant follicle, CL and all luteal phase granulosa cells, a second protein band of 68 kDa was consistently detected. In all samples, 11betaHSD2 had a molecular mass of 48 kDa, but in large antral follicles (> 8 mm), there was an additional immunoreactive band at 50 kDa. We conclude that 11betaHSD2 is the predominant functional 11betaHSD enzyme expressed in follicular phase granulosa cells from growing bovine antral follicles. In contrast, in bovine granulosa cells from dominant or luteal phase follicles, and in bovine luteal cells from early non-pregnant CL, 11betaHSD1 is the major glucocorticoid-metabolising enzyme. The increasing levels of cortisol inactivation by the combined NADP(+)- and NAD(+)-dependent 11beta-DH activities suggest a need to restrict cortisol access to corticosteroid receptors in the final stages of follicle development.

Constitutive steroidogenesis in ovine large luteal cells may be mediated by tonically active protein kinase A

The mechanisms responsible for the increased basal rates of progesterone secretion from large steroidogenic luteal cells (LLC) relative to small steroidogenic luteal cells (SLC) have not been clearly defined. To determine if protein kinase A (PKA) is tonically active in LLC, the adenylate cyclase activator forskolin and a specific PKA inhibitor (PKI) were utilized in a 2 x 2 factorial treatment with each steroidogenic cell type. Progesterone and cAMP production were quantified after the different treatments. In addition, the effects of the treatments on the concentrations and relative phosphorylation status of the steroidogenic acute regulatory (STAR) protein in the two cell types were determined as a measure of PKA activity. Treatment with PKI blocked forskolin-induced increases in progesterone secretion by SLC without affecting the production of cAMP. The treatment of LLC with PKI significantly decreased basal progesterone secretion in the presence or absence of forskolin, indicating that the high level of steroidogenesis in this cell type requires PKA activity. There were no differences in the steady-state concentrations of STAR protein in either cell type after treatment. However, the percentage of relative STAR phosphorylation was higher in the LLC than in SLC, and PKI treatment significantly decreased the phosphorylation of STAR in the LLC. The relative phosphorylation status of STAR and the concentrations of progesterone in the media were significantly correlated with the treatments in both cell types. The amount of progesterone secreted per picogram of cAMP was higher in the LLC than in the SLC, and this was accompanied by a significant increase in the ratio of relative STAR phosphorylation to the steady-state concentration of STAR protein. These data are compatible with the theory that LLC are constitutively steroidogenic, partly because they have tonically active PKA. In addition, the phosphorylation of STAR appears to be a primary activity of PKA in both types of ovine steroidogenic luteal cells.

Localization and temporal regulation of tissue inhibitor of metalloproteinases-4 in mouse ovary

Tissue inhibitors of metalloproteinases (TIMPs) are potential regulators of tissue remodeling in the ovary. The aim of the present study was to examine the localization and temporal regulation of TIMP-4 protein in the mouse ovary. An induced superovulation model (eCG/hCG) was employed in immature mice to evaluate TIMP-4 protein expression profiles in ovaries collected during the follicular phase, the pre ovulatory period, and the luteal lifespan. Immunofluorescence results indicated that TIMP-4 protein was localized to theca of both antral and preovulatory follicles and adjacent ovarian stroma. After the initiation of luteinization with hCG, TIMP-4 was observed within the luteinizing granulosa cells and persisted throughout the lifespan of the corpus luteum. In the cycling ovary, TIMP-4 signaling localized to corpus luteum from previous estrous cycles, the theca of preovulatory follicles, and appeared to be lower in newly forming corpus luteum. Western analysis further showed that the levels of TIMP-4 increased significantly during the luteinization process of granulosa cells, but no significant change was found among all corpus luteum stages. A putative regulatory mechanism of TIMP-4 expression was identified utilizing an in vitro model. Treatment of cultured granulosa cells with hCG significantly augmented TIMP-4 protein expression levels. Together our data indicate that the luteinization process of granulosa cells is associated with up-regulation of TIMP-4 and that TIMP-4 might play an essential role in maintenance of the luteal function during the whole lifespan of corpus luteum.

The effect of human chorionic gonadotrophin on the expression of progesterone receptors in human luteal cells in vivo and in vitro

The human corpus luteum expresses genomic progesterone receptors (PRs) suggesting that progesterone may have an autocrine or paracrine role in luteal function. We hypothesised that the reduction in luteal PR reported in the late-luteal phase augmented progesterone withdrawal and had a role in luteolysis. We therefore tested the hypothesis that luteal rescue with human chorionic gonadotrophin (hCG) would maintain PR expression. PR was immunolocalised to different cell types in human corpora lutea (n = 35) from different stages of the luteal phase and after luteal rescue with exogenous hCG. There was no change in the staining intensity of theca-lutein cell or stromal cell PR throughout the luteal phase or after luteal rescue. In the late-luteal phase, granulosa-lutein cell PR immunostaining was reduced (P < 0.05) but the trend to reduction was also seen after luteal rescue with hCG (P = 0.055). To further investigate the effect of hCG on granulosa-lutein cell PR expression, an in vitro model system of cultured human luteinised granulosa cells was studied. Cells were cultured for 12–13 days exposed to different patterns of hCG and aminoglutethamide to manipulate progesterone secretion (P < 0.0001). Expression of PR A/B and PR B isoforms was examined by quantitative real-time RT-PCR. PR A/B mRNA was lower (P < 0.05) after 11–13 days of culture than after 7 days of culture. This reduction could not be prevented by hCG in the presence (P < 0.05) or absence (P < 0.05) of stimulated progesterone secretion. The expression of PR B mRNA showed a similar pattern (P = 0.054). Simulated early pregnancy in vivo and hCG treatment of luteinised granulosa cells in vitro did not appear to prevent the down-regulation of PR seen during luteolysis.

Expression of sex hormone-binding globulin (SHBG) in human granulosa-lutein cells

Sex hormone-binding globulin (SHBG) was classically thought to be a plasma steroid-carrying protein of hepatic origin, but recently, locally produced, membrane-bound SHBG has been shown to influence cell functions in several steroid-responsive tissues. In the ovary, SHBG is known to be present in the follicular fluid, but information about a possible intracellular presence of SHBG in this organ is still very scarce. In this study the presence of SHBG was assessed by immunohistochemistry in human granulosa-lutein cells (GLC) collected by follicle puncture for in vitro fertilization. SHBG was detected in the cytoplasm of GLC before and after in vitro culture for up to 96 h. The presence of full-length SHBG messenger RNA was demonstrated in GLC by reverse transcription-polymerase chain reaction (RT-PCR) in both cultured and uncultured cells. These results demonstrate a local synthesis of SHBG in GLC and raise the question of the physiological significance of these findings in follicular physiology.

Differential expression of steroidogenic factor-1 and FTF/LRH-1 in the rodent ovary

Steroidogenic factor-1 (SF-1) (NR5A1) is an orphan nuclear receptor that plays a premier role in ovarian organogenesis. Recent studies document mRNA expression of the structurally related factor NR5A2 (FTF, LRH-1, SF-2) in the adult ovary and more specifically in granulosa cells and luteal cells but not theca cells. Conversely, SF-1 was shown to be expressed at higher levels in theca/interstitial cells. These latter observations raised the possibility that FTF/LRH-1 may control target gene expression in granulosa cells of developing follicles. Using quantitative PCR our results show that FTF/LRH-1 message is expressed at higher levels in the ovary than in liver or other tissues analyzed. We show by in situ hybridization and LacZ expression in ovaries of transgenic mice bearing an FTF-promoter-LacZ fusion gene that FTF/LRH-1 is selectively expressed in granulosa cells of rat and mouse ovaries and is not present in theca cells or interstitial cells. However, by a variety of approaches, we showed that SF-1 mRNA and protein are expressed in greater amounts than FTF/LRH-1 in granulosa cells of follicles at all stages of development. Expression of SF-1 mRNA and protein in granulosa cells was verified by in situ hybridization, immunohistochemistry of ovarian sections, and immunocytochemistry of cultured rat granulosa cells. The significance of SF-1 in regulating target gene activation was supported by EMSA. An abundant granulosa cell protein binding to the SF-1-binding motif (CCAAGGTCA) present in the aromatase promoter and an FTF/LRH-1 motif (TGTCCTTGAACA) in the alpha-fetoprotein promoter was supershifted by two SF-1-specific antibodies but not by an FTF antibody. Conversely, with the same probes, a less abundant protein/DNA complex present in liver and ovarian cell extracts was shifted by an FTF antibody but not by the SF-1 antibodies. SF-1 and FTF/LRH-1 were differentially regulated in vivo by estradiol, FSH and prolactin. Collectively these data indicate that granulosa cells of small and preovulatory follicles express both SF-1 and FTF/LRH-1 and that each orphan receptor may regulate target gene expression in these cells.

Cyclic changes of granulocyte colony-stimulating factor (G-CSF) mRNA in the human follicle during the normal menstrual cycle and immunolocalization of G-CSF protein

BACKGROUND

Ovulation has several similarities with inflammation and is closely connected to the activity of leukocytes and inflammatory cytokines. Since granulocytes are one of the major leukocytes, we focused our attention on the presence and local production of granulocyte colony-stimulating factor (G-CSF) in the human ovary.

METHODS

The presence of G-CSF protein in the follicular fluid and perifollicular tissues was examined by Western blot analysis (n = 5) and immunohistochemical staining (n = 10). The relative expression levels of G-CSF mRNA in relation to GAPDH in granulosa, theca and luteal cells during the menstrual cycle were measured by quantitative RT-PCR using TaqMan technology (n = 15).

RESULTS

G-CSF protein was detected in all follicular fluid and located mainly in granulosa cells of the follicle and luteal cells. The expression level of G-CSF mRNA in the late follicular phase was 137.6 +/- 18.5, which was approximately 10-fold greater than other phases during the menstrual cycle (P < 0.05).

CONCLUSIONS

These results demonstrate that G-CSF is produced in the human follicle shortly before the ovulatory phase and may play an important role in the mechanism of ovulation.

Cell-specific distribution of progesterone receptors in the bovine ovary

This study describes the localization of progesterone receptors (PR) in the bovine ovary. Ovaries were obtained from 11 non-pregnant and two pregnant cows. Progesterone receptors were visualized by immunohistochemistry on paraffin sections. Nuclear staining for PR was observed in cells of the follicles, corpora lutea, theca layers, surface epithelium, tunica albuginea, and in superficial and deep stroma cells. No staining was noticed in apoptotic bodies of atretic follicles. Expression of PR in follicle cells indicates an intrafollicular role of progesterone. The higher expression in thecal cells compared with follicle cells indicates that thecal cells mediate some effects of progesterone on the follicular development. Superficial stroma cells showing high expression might have a similar influence on primordial and primary follicles. In general, luteal cells had a lower expression than follicle cells, which may be explained by the down-regulatory effect of locally produced progesterone. The lower expression in luteal cells during pregnancy can be due to the longer life span of this corpus luteum and concomitant degeneration of its PR. The high and rather constant expression of PR in cells of the surface epithelium remains to be elucidated.

Angiogenesis in the Corpus Luteum of Early Pregnancy in the Marmoset and the Effects of Vascular Endothelial Growth Factor Immunoneutralization on Establishment of Pregnancy

This study investigated vascular and molecular changes in the corpus luteum (CL) of early pregnancy in the marmoset. Ovaries were studied on Days 21 (n = 6) and 28 (n = 6) of pregnancy and compared with corpora lutea from Day 21 (late luteal) of the nonconception cycle (n = 8). Endothelial cell proliferation was measured by immunocytochemical detection of incorporated bromodeoxyuridine. Endothelial cell and pericyte area were assessed by quantitative immunocytochemistry for CD31 and alpha-smooth muscle actin, respectively. Vascular endothelial growth factor (VEGF) and its receptors, kinase insert domain-containing region (KDR) and fms-like tyrosine kinase (Flt) mRNA, were localized and quantified in in situ hybridization. In addition, the effects of immunoneutralization of VEGF on establishment and maintenance of pregnancy were investigated by administering a VEGF neutralizing antibody on Days 0-10 of the luteal phase during potentially fertile cycles (n = 10) and compared with fertile controls (n = 6). No differences in the cellular or morphological parameters were found between pregnant and structurally intact nonpregnant corpora lutea. No major differences were found in expression of VEGF, Flt, or KDR in these CL. VEGF immunoneutralization markedly suppressed plasma progesterone secretion during treatment, but pregnancy rate was not significantly reduced. Thus, a role for VEGF in early pregnancy in the marmoset remains to be established. These results show that, by the late luteal phase in the marmoset, the corpus luteum has established a mature vascular system and the molecular capacity to synthesize VEGF and its receptors. A pregnancy-induced spurt of angiogenesis or gene expression does not appear to take place; rather, maintenance of the existing vasculature is all that is required for the establishment of pregnancy.

Cell-specific distribution of progesterone receptors in the bovine ovary

This study describes the localization of progesterone receptors (PR) in the bovine ovary. Ovaries were obtained from 11 non-pregnant and two pregnant cows. Progesterone receptors were visualized by immunohistochemistry on paraffin sections. Nuclear staining for PR was observed in cells of the follicles, corpora lutea, theca layers, surface epithelium, tunica albuginea, and in superficial and deep stroma cells. No staining was noticed in apoptotic bodies of atretic follicles. Expression of PR in follicle cells indicates an intrafollicular role of progesterone. The higher expression in thecal cells compared with follicle cells indicates that thecal cells mediate some effects of progesterone on the follicular development. Superficial stroma cells showing high expression might have a similar influence on primordial and primary follicles. In general, luteal cells had a lower expression than follicle cells, which may be explained by the down-regulatory effect of locally produced progesterone. The lower expression in luteal cells during pregnancy can be due to the longer life span of this corpus luteum and concomitant degeneration of its PR. The high and rather constant expression of PR in cells of the surface epithelium remains to be elucidated.

Distinct expression of endothelin receptor subtypes A and B in luteinized human granulosa cells

Endothelins (ET) are potent vasoconstrictive peptides originally isolated from vascular endothelial cells. Their biological effects are mediated through two different receptors, the endothelin-1 (ET-1)-selective endothelin receptor subtype ETA and the non-selective receptor subtype ETB. ET-1 protein has been found in human ovarian follicular fluid and ET-1 mRNA expression has been demonstrated in ovarian tissue. These findings indicate that the endothelin-system participates in the modulation of ovarian function, probably acting in an autocrine/paracrine manner. In the current study we used freshly aspirated, luteinized human granulosa cells (hGC) representing an in vitro model of the early corpus luteum. By means of RT-PCR and immunocytochemistry we investigated whether luteinized human granulosa cells express ETA and ETB receptors. Specific amplification products of ETA transcripts were detected in all samples investigated. In contrast, only after using a three-fold amount of ETB reverse transcripts we were able to demonstrate specific, but weak amplification products. In addition, immunocytochemical staining for ETA but not for ETB was found in granulosa cell preparations. The present study provides clear evidence that human granulosa cells predominantly express ETA receptor subtype mRNA and protein hinting to its possible role in follicle maturation and corpus luteum formation.

Immunolocalization of progesterone receptors in the canine ovary and their relation to sex steroid hormone concentrations

The aim of the present study was to describe the normal cellular distribution of progesterone receptors in the canine ovary at different stages of the oestrous cycle. Samples of both ovaries were obtained from 75 healthy adult bitches of various breeds and ages, including five pregnant bitches and three bitches that had just delivered. The presence of progesterone receptors was visualized by immunohistochemistry on paraffin wax sections using a monoclonal antibody. Nuclear staining for progesterone receptors was observed in the surface epithelium, cortical tubules, rete ovarii, follicle cells, thecal cells, luteal cells, granulosa cell cords and ovarian stroma. The staining intensity for progesterone receptors in the follicle cells increased with the stage of follicle development, indicating an intrafollicular role of progesterone in the mechanism of ovulation and luteinization. The stronger staining intensities for progesterone receptors in thecal cells compared with follicle cells may be explained by the fact that thecal cells mediate some effects of steroid hormones on the follicle cells in secondary and tertiary follicles. Little correlation was found between the expression of progesterone receptors in follicle cells and oestradiol, progesterone or testosterone concentrations. This finding indicates a different regulating mechanism for progesterone receptors in canine ovarian follicles compared with other tissues of the genital tract. During pregnancy all groups of ovarian cells had lower staining intensity scores than during the oestrous cycle, although the sex steroid hormone concentrations in pregnant bitches were similar to those in non-pregnant bitches during the luteal phase of the oestrous cycle. The lower expression of progesterone receptors during pregnancy may be due to higher tissue concentrations of progesterone that are not reflected in the serum because of haemodilution and increased metabolism and clearance during pregnancy.

Immunolocalization of relaxin in the corpus luteum of the dromedary camel. (Camelus dromedarius)

The objective of this study was to determine the distribution of the peptide hormone relaxin in ovarian tissues of the pregnant and non-pregnant dromedary (Camelus dromedarius). Using light and electron microscopy we here describe the presence of relaxin in cells of the corpus luteum at various stages of the reproductive cycle of this important species.

Involvement of membrane surface charge in thermal stability of the rat ovarian LH/hCG receptor

Analysis of fluorescence of membrane-bound 8-anilino-1-naphthalene sulfonate and monodansylcadaverine probes revealed that a negative membrane surface charge derived from free fatty acids (FFA) resulted in destabilization of structure-functional properties of the rat ovarian LH/hCG receptor. Removal of FFA from rat luteal and porcine ovarian granulosa cells by BSA increased gonadotropin responsiveness of cells in cAMP formation.

Effects of high density lipoprotein containing high or low beta-carotene concentrations on progesterone production and beta-carotene uptake and depletion by bovine luteal cells

Luteal cells were isolated from mid-luteal heifer ovaries by collagenase digestion. Cells were cultured with DMEM/Ham's F12 medium in serum pre-treated plastic culture dishes for periods of up to 11 days. As beta-carotene is almost completely insoluble in all polar solvents, it was added to cultures in either dimethyl sulphoxide (DMSO), tetrahydrofuran (THF) or as high-density lipoprotein (HDL) containing high or low beta-carotene concentrations. Medium was replaced after 24 h, thereafter medium was changed every 48 h. Treatment of cells with DMSO alone or with beta-carotene (5 micromol/l) in DMSO both resulted in significant (P<0.01) stimulation of progesterone production. beta-Carotene (5 micromol/l) in THF did not alter progesterone production but 50 micromol/l beta-carotene in THF resulted in significant inhibition (P<0.02) of progesterone production on days 3 and 7. Cultures were also supplemented with bovine HDL preparations containing equal concentrations of cholesterol (25 microg/ml) but high or low beta-carotene (12.4 or 0.44 microg/mg of cholesterol). Both HDL preparations significantly stimulated progesterone production (P<0. 001) but the high beta-carotene HDL was significantly (P<0.02) more effective than the low beta-carotene HDL. However, when given together with bovine luteinizing hormone (bLH) or dibutyryl cAMP (dbcAMP), the high beta-carotene HDL stimulated progesterone production less than did the low HDL (P<0.01). Uptake and depletion of beta-carotene by luteal cells were also examined in culture. beta-Carotene supplementation increased luteal cell beta-carotene from an initial level of 373 ng per 10(6) cells to 2030 ng per 10(6) cells by day 6. In contrast, the levels in control cells decreased to 14% of starting values during the same period. Cells treated with HDL containing high beta-carotene on day 1 or days 1 and 3 were then incubated with or without bLH or dbcAMP for a further 2 days to investigate the effect of bLH and dbcAMP on depletion of beta-carotene by luteal cells. beta-Carotene depletion in the luteal cells was significantly higher (P<0.05) in LH- and dbcAMP-treated cells than in the control cells in both groups. These results indicate that the use of solvents such as DMSO or THF may have undesirable effects due to alteration of cell membrane permeability. Supplementation with bLH or dbcAMP may increase the metabolism of beta-carotene in luteal cells. bLH or dbcAMP together with high beta-carotene HDL may, when combined with the effect of increased beta-carotene metabolism, give less stimulation than with low beta-carotene HDL.

Characterization and regulation of type A endothelin receptor gene expression in bovine luteal cell types

Our previous studies demonstrated that endothelin-1 (ET-1), a 21-amino acid vasoconstrictor peptide, has a paracrine regulatory role in bovine corpus luteum (CL). The peptide is produced within the gland where it inhibits progesterone production by acting via the selective type A endothelin (ETA) receptors. The present study was designed to characterize ETA receptor gene expression in different ovarian cell types and its hormonal regulation. ETA receptor messenger RNA (mRNA) levels were high in follicular cells as well as in CL during luteal regression. At this latter stage, high ETA receptor expression concurred with low prostaglandin F2alpha receptor mRNA. The ETA receptor gene was expressed by all three major cell populations of the bovine CL; i.e. small and large luteal cells, as well as in luteal endothelial cells. Among these various cell populations, the highest ETA receptor mRNA levels were found in endothelial cells. cAMP elevating agents, forskolin and LH, suppressed ETA receptor mRNA expression in luteinized theca cells (LTC). This inhibition was dose dependent and was evident already after 24 h of incubation. In luteinized granulosa cells (LGC), 10 and 100 ng/ml of insulin-like growth factor I and insulin (only at a concentration of 2000 ng/ml) markedly decreased ETA receptor mRNA levels. In both LGC and LTC there was an inverse relationship between ETA receptor gene expression and progesterone production; insulin (in LGC) and forskolin (in LTC) enhanced progesterone production while inhibiting ETA receptor mRNA levels. Our findings may therefore suggest that, during early stages of luteinization when peak levels of both LH and insulin-like growth factor I exist, the expression of ETA receptors in the gland are suppressed. This study demonstrates physiologically relevant regulatory mechanisms controlling ETA receptor gene expression and further supports the inhibitory role of ET-1 in CL function.

Expression of the steroidogenic acute regulatory protein and luteinizing hormone receptor and their regulation by tumor necrosis factor alpha in rat corpora lutea

Expression of both mRNA and protein of the steroidogenic acute regulatory protein (StAR), in correlation with progesterone (P) production and LH receptor (LHR) mRNA expression, was studied in the corpora lutea (CL) of gonadotropin-induced-pseudopregnant and pregnant rats at various stages of CL development. Immature female rats, 21-22 days old, were injected s.c. with 20 IU eCG to stimulate follicle growth and then with 20 IU hCG 48 h later to induce ovulation. The ovaries were removed at various stages of CL development; either CL were isolated and snap frozen for total RNA analysis, or whole ovaries were fixed in Bouin's fluid for paraffin sectioning. The results of in situ hybridization, immunohistochemistry, and Northern blotting showed that the increase in StAR mRNA and protein expression was well correlated with the increase in serum P concentration. StAR expression was restricted to the luteal cells or theca cells in antral follicles. Both StAR mRNA and protein in the CL of pseudopregnant rats increased steadily on Day 1 and Day 4, reached highest levels on Day 4, and then dropped sharply on Day 8 when luteolysis takes place. LHR mRNA content was high on Day 1 but dropped significantly on Day 2. LHR mRNA increased to high levels on Day 4 and 8 and then declined on Day 12. StAR mRNA and protein levels in the CL of pregnant rats were high during early luteal development (Day 2, 4), increased even further on Day 9, and decreased on Day 13 when luteolysis takes place. It is therefore suggested that the expression of StAR coincides well with the capacity of P production in the CL and that StAR expression can be used as a functional "marker" of CL development. To study the possible effect of cytokines on StAR expression, pseudopregnant rats on Day 5 were injected s.c. with 10 IU hCG plus 20 microg prolactin (PRL), with or without 500 IU tumor necrosis factor alpha (TNFalpha) 30 min later. TNFalpha significantly inhibited hCG/PRL-induced StAR and LHR mRNA expression at 1 and 3 h post-TNFalpha. It is suggested that the luteolytic effect of TNFalpha may be mediated by its direct inhibition on StAR expression or by an indirect decrease in LHR expression.

Co-localization of Rab3B and oxytocin to electron dense granules of the sheep corpus luteum during the estrous cycle

Oxytocin and its carrier protein, neurophysin, are both associated with luteal secretory granules which migrate from the paranuclear region to the cell membrane where exocytosis takes place. Rab3 proteins are thought to be associated with membrane vesicles or granules undergoing exocytotic fusion with the plasma membrane. The objective of this study was to determine whether Rab3B is co-localized with oxytocin within the same secretory granules of large luteal cells obtained from corpora lutea of 16 Merino cross ewes at day 3, 7, 12 or 15 of the estrous cycle using immunocytochemistry. The mean granule density (granules/microm3) was not significantly different (P > 0.05) between the days examined. Electron microscopic immunocytochemistry showed that oxytocin and Rab3B were co-localized to the secretory granules on all days evaluated. Rab3B immunostaining was primarily located within secretory granules scattered throughout the cytoplasm. The mean intensity of labelling (number of gold particles) for oxytocin per microm2 cytoplasmic luteal tissue was significantly decreased on day 15 compared to those observed on days 3, 7 and 12 of estrous cycle. No significant changes were observed in the mean intensity of the Rab3B label at the different times of the cycle. The present study provides evidence that a member of the subfamily of Rab proteins, Rab3B, is present and co-localized with oxytocin in the same secretory granules of the ovine corpus luteum. These results implicate Rab3B protein directly or indirectly in the hormone secretory pathway of ovarian tissue.

Detection and functional characterisation of the transcription factor peroxisome proliferator-activated receptor gamma in lutein cells

A prominent functional change during differentiation of lutein cells from follicular thecal and granulosa cells is an enhanced production and secretion of progestins. The regulation of this process is not fully understood but may be associated with the expression of transcription factors which activate genes, products of which are involved in pathways of the cholesterol and lipid metabolism. As peroxisome proliferator-activated receptors (PPARs) play a role in both pathways, we were interested in the expression of PPARgamma, a PPAR form which is involved in adipogenic differentiation. First, we were able to show the expression of PPARgamma in bovine lutein cells (day 12 of the ovarian cycle) at the mRNA and protein level by imaging, flow cytometry and blot analysis, and secondly a role of PPARgamma in the secretion of progesterone. The cells (24 h culture) responded dose dependently by increasing progesterone secretion (up to 1.5-fold of the basal level) to an endogenous ligand of PPARgamma, 15-deoxy-delta12,14 prostaglandin J2 (15-dPGJ2) and to the thiazolidinedione ciglitizone. Aurintricarboxylic acid (ATA) was found to reduce the intracellular PPARgamma level and to promote cell cycle progress, indicating that ATA can be used as a tool for experimental changes of PPARgamma proteins in intact cells and for studying the physiological consequences. The ATA-mediated decrease of PPARgamma was accompanied by reduced progesterone production and a progression of the cell cycle, suggesting a function of PPARgamma in both processes. The response to ATA was abrogated by a high dose (>490 nM) of 15-dPGJ2, suggesting that 15-dPGJ2 exerts its effect on steroidogenic activity via PPARgamma and that the 15-dPGJ2-PPARgamma system plays a role in the maintenance of a differentiated quiescent stage in lutein cells.

Immunohistochemical detection of the melanocortin 1 receptor in human testis, ovary and placenta using specific monoclonal antibody

We describe the immunohistochemical detection of the melanocortin 1 receptor (MC1R) protein in human gonadal tissues using a specific monoclonal antibody. The MC1R was found to be present in Leydig's cells in testis, in lutein cells in the corpus luteum and in the nucleus of the trophoblastic cells of the placenta. Though it has been speculated earlier that MC1R is present in gonadal tissues, this is the first report demonstrating the presence of MC1R protein in these cells.

Immunohistochemical localization of basic fibroblast growth factor (bFGF) during folliculogenesis in the human ovary

Basic fibroblast growth factor (bFGF) has been suggested to be one of the intraovarian regulators of ovarian folliculogenesis, but its localization in the human ovary remains to be determined. We examined the immunohistochemical reactivity for bFGF in the course of follicular development and corpora lutea formation in the human ovary. Pregranulosa cells in the primordial follicle were negative, but at the preantral stage both granulosa and theca cells showed weakly positive immunostaining for bFGF. In the antral follicles, both granulosa and theca interna cells showed stronger staining for bFGF with the increase in follicular diameter. In atretic follicles at various stages, granulosa cells were negative or weakly positive for bFGF, whereas luteinized theca cells showed strong immunoreactivity. In the corpora lutea during the early luteal phase, granulosa lutein cells were strongly positive for bFGF but in the late luteal phase became immunonegative. On the other hand, bFGF staining in theca lutein cells was strong throughout the course of corpora lutea formation and regression. These findings suggest that bFGF is localized not only in granulosa cells but also in theca cells, and in the latter, bFGF immunoreactivity is associated with luteinization.

Immunodetection of cotinine protein in granulosa-lutein cells of women exposed to cigarette smoke

OBJECTIVE

To detect immunoreactivity to cotinine protein, a major metabolite of nicotine, in granulosa-lutein cells from patients exposed to cigarette smoke, as measured by levels of cotinine in follicular fluid (FF) samples.

DESIGN

Controlled immunocytochemical study.

SETTING

Hospital IVF-ET program treating infertile patients.

PATIENT(S)

Twenty-eight women classified by self-reported smoking habits: active smokers (n = 17), passive smokers (n = 4), and nonsmokers (n = 7).

INTERVENTION(S)

Ovarian hyperstimulation.

MAIN OUTCOME MEASURE(S)

Grades of immunostaining intensity were assessed in granulosa-lutein cells. Patient scores of cell immunostaining were calculated and regressed on levels of FF cotinine.

RESULT(S)

Cotinine levels in FF were higher in active smokers than in passive smokers or nonsmokers. Cotinine immunostaining was visualized in the nucleus and cytoplasm of granulosa-lutein cells. Mean grades and mean scores of immunostaining intensity were higher in active smokers than in passive smokers or nonsmokers. There was a strong positive correlation between scores of cell immunostaining and FF cotinine levels.

CONCLUSION(S)

The association between cotinine expression in granulosa-lutein cells and FF cotinine provides reliable evidence for a dose-related effect. This constituent of cigarette smoke appears to interact directly with and incorporate into these ovarian cells. Our approach seems useful for monitoring ovarian exposure to environmental toxins.

Multiple steroidogenic factor 1 binding elements in the human steroidogenic acute regulatory protein gene 5'-flanking region are required for maximal promoter activity and cyclic AMP responsiveness

A proximal element from the human StAR gene promoter, containing the sequence (-105)TATCCTTGAC(-95), was shown to confer responsiveness to 8-Br-cAMP in the presence of steroidogenic factor 1 (SF-1) when placed behind a minimal thymidine kinase promoter or an SV40 promoter and transfected into BeWo cells which normally lack StAR and SF-1. This element was also transactivated by SF-1 in a yeast one-hybrid system. The -105 to -95 sequence was protected by SF-1 in footprint analysis and a double-stranded oligonucleotide containing the element bound SF-1 specifically in electrophoretic mobility shift assays. Another SF-1-binding sequence 35 bp upstream of the transcription start site ((-42)CAGCCTTC(-35)) was identified in the DNase 1 footprint analysis and, when mutated, markedly reduced SF-1-dependent and 8-Br-cAMP-stimulated StAR promoter activity in BeWo cells. The two proximal SF-1 response elements were shown to be critical for StAR promoter function in human granulosalutein cells, which express SF-1 and respond to cAMP with increased transcription of the StAR gene. Mutation of either element substantially reduced basal and forskolin-stimulated promoter activity, although mutation of the -105 to -95 element had more pronounced effects. Mutation of a third, more distal, SF-1-binding site at -926 to -918 also reduced basal but not forskolin-stimulated promoter activity in the granulosa-lutein cells. These findings demonstrate that multiple SF-1 response elements are required for maximal StAR promoter activity and regulation by cAMP.

The expression of sf-1/Ad4BP is related to the process of luteinization in the marmoset (Callithrix jacchus) ovary

Expression of the nuclear receptor, steroidogenic factor-1 (SF-1/Ad4BP), was studied in a primate (marmoset) ovary using immunohistochemical, RT-PCR, and immunoblot techniques. The periovulatory phase was compared with the luteal phase. With PCR we found a marmoset homolog of SF-1/Ad4BP to be expressed in ovarian and other steroidogenic tissues. Characteristically, the periovulatory ovaries consisted of growing (non-luteinized) small follicles together with large luteinizing follicles and many corpora lutea accessoria (Clas), which had developed from atretic large follicles. During the luteal phase, true corpora lutea (Cls) were additionally found. In general, we found that small follicles were devoid of any immunoreactivity of SF-1/Ad4BP. In large follicles, the luteinizing theca and granulosa cells express SF-1/Ad4BP. All luteal cells of Clas showed a nuclear staining in both ovary types. In Cls, only a few luteal cells were positive. Large follicles of different sizes showed no differences in expression level, as evidenced by immunoblot analysis. Our results indicate that SF-1/ Ad4BP participates in the activation of genc transcription during the onset of luteinization and that Clas are essential for ovarian luteal function.

Immunohistological localization and expression of alpha-actin in the baboon (Papio anubis) corpus luteum

We have recently shown the presence of E-cadherin and of alpha- and gamma-catenins in human and baboon corpora lutea. These are components of adherens junctions between cells. The cytoplasmic catenins link the cell membrane-associated cadherins to the actin-based cytoskeleton. This interaction is necessary for the functional activity of the E-cadherins. Our aim therefore was to determine the presence of alpha-actin in the baboon corpus luteum, to further establish whether the necessary components for E-cadherin activity are present in this tissue. An antibody specific for the smooth muscle isoform of actin, alpha-actin, was used for these studies. The results using immunohistochemistry show that (a) alpha-actin is present in steroidogenic cells of the active corpus luteum, theca externa of the corpus luteum, cells of the vasculature, and the tunica albuginea surrounding the ovary. The intensity of immunoreactivity for alpha-actin varied, with the cells of the vasculature reacting more intensely than the luteal cells. A difference in intensity of immunoreactivity was also observed among the luteal cells, with the inner granulosa cells showing stronger immunoreactivity than the peripheral theca lutein cells. There was no detectable immunoreactivity in the steroidogenic cells of the atretic corpus luteum. However, in both the active and atretic corpora lutea, alpha-actin-positive vascular cells were dispersed within the tissue. (b) Total alpha-actin (luteal and non-luteal), as determined by Western blot analyses, does not change during the luteal phase and subsequent corpus luteum demise (atretic corpora lutea). (c) hCG stimulated the expression of alpha-actin and progesterone secretion by the early luteal phase (LH surge + 1-5 days) and mid-luteal phase (LH surge + 6-10 days) cells in culture, but only progesterone in the late luteal phase (LH surge + 11-15 days). The data show that alpha-actin is present in luteal cells and that its expression is regulated by hCG, thus suggesting that E-cadherin may form functional adherens junctions in the corpus luteum.

Ovarian intrabursal administration of transforming growth factor beta 1 inhibits follicle rupture in gonadotropin-primed mice

We hypothesized that over-expression and/or activation of latent transforming growth factor betas (TGF betas) by various ovarian cell types may lead to disturbances in ovulation and fertilization. To test this hypothesis, active TGF beta ranging from 1 to 500 ng was administered intrabursally into the ovaries of gonadotropin-primed mice, and the rates of ovum recovery and fertilization were determined. Furthermore, the presence and cellular distribution of endogenous TGF betas and TGF beta type I and type II receptors were determined immunohistochemically in the ovarian tissues of TGF beta 1-treated and untreated groups. The total number of ova recovered per ovary from ovaries treated as pairs or treated singly with TGF beta 1 at 1 to 10 ng/ovary was similar to that from controls, whereas the number recovered from ovaries treated as pairs or singly with 50 or 100 ng of TGF beta 1 per ovary was significantly lower than the number from respective controls (p < 0.05, 0.001). The number of ova recovered per ovary from ovaries treated as pairs or singly with TGF beta 1 at 200 or 500 ng/ovary was similar to the number of ova obtained from ovaries treated with TGF beta 1 at 100 ng/ovary. The rate of in vitro fertilization was low in ova recovered from ovaries treated with 50, 100, 200, and 500 ng/ovary of TGF beta 1, compared to that in ova from untreated ovaries. Histologically, the TGF beta 1-treated ovaries contained large numbers of unruptured follicles, whereas untreated ovaries contained large numbers of corpora lutea. Immunohistochemically, the endogenous TGF beta 1 and TGF beta 2 was localized in theca, granulosa, and luteal cells, without a substantial difference in intensity or distribution, in both TGF beta 1-treated ovaries and in controls. Theca cells were the primary site of immunoreactive TGF beta protein. TGF beta type I and type II receptors were also present in these cells, and their relative immunoreactive intensity was considerably reduced, particularly in granulosa cells in TGF beta 1-treated ovaries compared to controls. The results support our hypothesis and suggest that TGF betas play an important regulatory role in follicular development, oocyte maturation, and the ovulatory process.

Immunohistochemical localization of activin A and follistatin in human tissues

We immunohistochemically investigated the localization of activin A and follistatin in various human tissues with specific antibodies to recombinant human (rh-) activin A and rh-follistatin. Specific immunostaining of activin A was detected in Leydig and Sertoli cells of the testis. In the ovary, granulosa cells of mature follicle and luteal cells of the corpus luteum stained for activin A. Immunoreactive activin A was present in somatotrophs of the pituitary gland and insulin-positive B cells of the pancreatic islets. Immunoreactivity for activin A was also found in thyroid follicular cells, adrenocortical cells, neuronal cells of the cerebrum and monocytoid cells in the bone marrow. Follistatin, an activin-binding protein, was immunostained in the same tissues as activin A. These findings indicated that activin A and follistatin are widely distributed in human tissues, suggesting that activin plays important roles as a common regulator in various tissues under the control of co-existing follistatin.

Epidermal growth factor (EGF) receptor localization in cultured human granulosa lutein cells and the stimulation of progesterone production by EGF and transforming growth factor-alpha (TGF-alpha)

PURPOSE

The purpose of this study was to investigate the expression of EGF receptor (EGF-R) in human granulosa cells undergoing luteinization and progesterone production by these cells in response to EGF an TGF-alpha alone or in combination with luteinizing hormone (LH). Granulosa cells were obtained from IF patients following oocyte retrieval 34 to 36 hr post-hCG injection. EGF receptor was localized in cells by means of immunoperoxidase staining using a polyclonal primary antibody directed against the human EGF-R. To assess progesterone production, cells were seeded overnight, washed, and cultured with the growth factors +/- LH. Medium and treatments were changed every 24 hr for 3 days.

RESULTS

Specific EGF-R staining was observed in the cultured cells compared to those incubated with antibody that was preabsorbed with a 10-fold excess of EGF. Basal progesterone accumulation per 24-hr period was stimulated dose dependently on each day of culture, by both EGF (up to 3.5-fold at 5 or 50 ng/ml) and TGF-alpha (up to 4-fold at 50 ng/ml). The addition of LH alone also stimulated progesterone accumulation daily, and this effect was further enhanced dose dependently by cotreatment with EGF or TGF-alpha. Furthermore, tyrphostin, an EGF-R-specific tyrosine kinase inhibitor, inhibited both basal and growth factor-stimulated progesterone production.

CONCLUSION

These data suggest an EGF receptor-mediated physiological role for EGF and TGF-alpha in human luteal function involving an autocrine and/or a paracrine stimulation of progesterone production.

Expression and selective cellular localization of granulocyte-macrophage colony-stimulating factor (GM-CSF) and GM-CSF alpha and beta receptor messenger ribonucleic acid and protein in human ovarian tissue

Reverse transcription-polymerase chain reaction (RT-PCR), in situ hybridization, and immunohistochemical observations revealed that human ovarian tissue expressed granulocyte-macrophage colony-stimulating factor (GM-CSF) as well as GM-CSF alpha and beta receptor (R) mRNA and protein. The RT-PCR products revealed the predicted 286-, 546-, and 380-bp fragments for GM-CSF, GM-CSF alpha R, and GM-CSF beta R, respectively, which were further verified by restriction enzyme digestion analysis. In situ hybridization revealed that the theca interna of the large follicles and luteal cells are the exclusive site of GM-CSF mRNA expression. Furthermore, immunohistochemical studies using specific monoclonal antibodies indicated that the theca interna of the large follicles are the exclusive site of GM-CSF protein, whereas theca externa and to a lesser extent the granulosa cells are the major sites of GM-CSF alpha R and beta R proteins. Atretic follicles and follicular cysts showed very low or no detectable levels of GM-CSF and GM-CSF alpha R and beta R. In the luteal tissue, both the small and large luteal cells of early luteal (Days 14-19) and midluteal (Days 20-25) phase expressed GM-CSF mRNA and protein as well as GM-CSF alpha R and beta R proteins, and their immunostaining intensity was similar to that seen with theca cells. Luteal cells from late luteal phase (Days 26-28), corpus albicans, and ectopic pregnancy expressed a low level of GM-CSF, GM-CSF alpha R, and GM-CSF beta R mRNA and protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Gene expression and peptide localization for epidermal growth factor receptor and its ligands in porcine luteal cells

The present study was undertaken to determine the expression of the genes for epidermal growth factor receptor (EGF-R), and two of its ligands, epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) in isolated large (LLC) and small (SLC) porcine luteal cells by reverse transcription-polymerase chain reaction (RT-PCR), and to localize their peptides in whole corpora lutea (CL) as well in isolated LLC and SLC by immunocytochemistry. RT-PCR revealed strong cDNA signals for EGF-R and EGF in both LLC and SLC, and for TGF-alpha in LLC. The signal for TGF-alpha message in SLC was relatively weaker but detectable. Immunocytochemistry revealed intense EGF-R staining in LLC and SLC in both isolated and intact CL preparations. On the other hand, immunoreactive EGF and TGF-alpha appeared to be present only in LLC in intact CL sections, and isolated luteal cell preparations confirmed their presence in LLC and absence in SLC. These results suggest an autocrine/paracrine role for EGF and TGF-alpha in luteal functions.

Cytokeratin expression in bovine corpora lutea

Cytokeratin (CK)-positive cells were obtained from bovine corpora lutea. When cultured, these cells behave like CK-positive endothelial cells obtained from bovine large blood vessels. The origin of CK-positive cells has now been studied in 45 bovine corpora lutea of different estrous cycle stages. Additionally, 7 corpora lutea of pregnant cows were examined. The tissues were grouped into early stage (days 2 to 4), secretory stage (days 5 to 17) and late stage (days 18 to 21) according to gross morphology, wet weight and total progesterone content. One portion of a corpus luteum was used for immunohistochemistry, and another for Western blot analysis. Twenty-six of the 45 corpora lutea showed CK expression, as confirmed by immunostaining and Western blotting. Cytokeratin expression was found in all corpora lutea from the early stage, in 14 of 26 corpora lutea from the secretory stage, and 3 of 10 from the late stage. Early stage corpora lutea displayed "zonation" such that a high number of CK-positive luteal cells occurred in the region of the previous granulosa layer and a very low number in the previous thecal layer. Secretory CK-positive corpora lutea showed uniformly distributed, predominantly large luteal cells. In secretory corpora lutea of group A, CK-positive cells and a distinct microvascular tree were seen, the latter visualized by factor VIII-related antigen immunolabelling of endothelial cells. Group B showed none or very few CK-positive cells. Corpora lutea of pregnant cows behaved like corpora lutea of group B. Roughly 1% of CK-positive cells closely associated with the capillary wall were sometimes reminiscent of endothelial cell sprouts.

Expression of vascular permeability factor/vascular endothelial growth factor by human granulosa and theca lutein cells. Role in corpus luteum development

Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) is a cytokine that is overexpressed in many tumors, in healing wounds, and in rheumatoid arthritis. VPF/VEGF is thought to induce angiogenesis and accompanying connective tissue stroma in two ways: 1), by increasing microvascular permeability, thereby modifying the extracellular matrix and 2), as an endothelial cell mitogen. VPF/VEGF has been reported in animal corpora lutea and we investigated the possibility that it might be present in human ovaries and have a role in corpus luteum formation. We here report that VPF/VEGF mRNA and protein are expressed by human ovarian granulosa and theca cells late in follicle development and, subsequent to ovulation, by granulosa and theca lutein cells. Therefore, VPF/VEGF is ideally positioned to provoke the increased permeability of thecal blood vessels that occurs shortly before ovulation. VPF/VEGF likely also contributes to the angiogenesis and connective tissue stroma generation that accompany corpus luteum/corpus albicans formation. Finally, VPF/VEGF was overexpressed in the hyperthecotic ovarian stroma of Stein-Leventhal syndrome in which it may also have a pathophysiological role.

Oxytocin gene expression and oxytocin immunoactivity in the ovary of the common marmoset monkey (Callithrix jacchus)

Oxytocin was identified in ovaries recovered on Day 5 (+/- 1) of the luteal phase from three female marmoset monkeys (Callithrix jacchus). With use of a reverse transcription-polymerase chain reaction assay, expression of mRNA for oxytocin and oxytocin receptor was detected in both luteal tissue and in the ovarian remnant. Evidence for ovarian synthesis of oxytocin was provided by immunohistochemistry, which showed positive staining for oxytocin and neurophysin in the cytoplasm of the luteal cells. Some luteal cells had a more intensely stained perinuclear region than others for oxytocin immunoreactivity, whereas the staining for neurophysin was evenly distributed. Granulosa and theca cells of antral follicles also showed positive staining for oxytocin immunoreactivity; no reactivity was found in fibroblast or endothelial cells. Oxytocin immunoreactivity was also detected in the luteal tissue of all animals by immunoassay, with values ranging from 2.8 to 12.1 ng/g wet weight. The oxytocin concentration for the ovarian remnant was either very low (0.55-0.75 ng/g wet weight) or nondetectable (< 0.5 ng/g wet weight). Local production of oxytocin within the ovary was suggested by the measurement of higher oxytocin concentrations in the blood from ovaries containing corpora lutea compared with peripheral blood. Collectively, these results provide evidence for ovarian biosynthesis of oxytocin and suggest the possibility of a paracrine role in the regulation of primate ovarian function.

Hormonal and immunological characterization of the 32 kilodalton ovarian-specific protein

Recent studies from this laboratory have shown that the large luteal cell of the pregnant rat contains an abundant 32 kilodalton (32K) phosphoprotein which is up-regulated by estradiol. In order to assess the potential importance of this protein and to more fully understand its function, a specific polyclonal antibody was produced against the 32K and was used to examine its intraovarian localization, its tissue specificity, and its developmental regulation. Immunocytochemical localization of the 32K in the ovary of the pregnant rat found this protein to be selectively and abundantly expressed in the corpus luteum. Immunofluorescence study of small and large luteal cell populations clearly revealed an extensive localization of the 32K in the large luteal cells. Western blot analysis revealed that the 32K was absent from all steroidogenic and nonsteroidogenic tissues. Whereas this protein was absent from all other tissues examined in the rat, it was clearly expressed in corpora lutea of different animal species, including the mouse, hamster, cow, human, and pig. Although undetectable by immunohistochemistry, Western blot analysis showed this protein to be present in the follicle but at levels markedly lower than in the corpus luteum. Analysis of theca and granulosa cells revealed the presence of the 32K in both cell types. To further examine the developmental expression of this protein throughout gestation, Western blot analysis of microsomal fractions isolated from rat corpora lutea on days 3-21 of pregnancy was performed. The 32K was detected at low levels in early pregnancy, increased markedly on day 11, reached a peak on days 14-15, and remained elevated through day 21. Treatment with estradiol and PRL increased the content of the 32K in the corpus luteum. Human CG, known to cause follicular development to the preovulatory stage and to enhance luteal estradiol synthesis, also increased levels of the 32K in the corpus luteum, while it concomitantly decreased this protein in the follicle. In summary, the presence of a unique ovarian-specific 32 kilodalton protein has been established. This protein, which is present in low abundance in theca and granulosa cells, is localized to the large luteal cell and becomes abundantly expressed during midpregnancy, a time when there is a remarkable increase in luteal cell size and activity. Results of this study also demonstrate a multihormonal regulation of the 32K by tropic hormones. Thus, because of its apparent uniqueness and its timely and highly regionalized expression, the 32K may play a central role in the regulation of corpus luteum growth and function.

Differential capacity for cholesterol transport and processing in large and small rat luteal cells

The aim of this investigation was to determine whether a specific luteal subpopulation is responsible for the hypertrophic development of the corpus luteum at midpregnancy in the rat and to determine whether there was an underlying cellular basis for the differential production of steroids by the luteal cell subtypes. To examine this, we have dispersed and separated rat luteal steroidogenic cell populations into small (< 20 microns) and large (> 30 microns) cell types by elutriation. Luteal cells were examined at early (day 3) and midpregnancy (day 14) for differences in protein content and for differential expression of proteins required for steroid production. Specific proteins examined include the P450side chain cleavage enzyme (P450scc), adrenodoxin and adrenodoxin reductase, proteins required for cholesterol conversion to progestagens in the corpus luteum, and sterol carrier protein-2 (SCP2), a protein thought to be involved in intracellular cholesterol transport. The cytochrome P450(17)alpha hydroxylase (P450(17)alpha), a key enzyme responsible for androgen biosynthesis was also examined in the isolated luteal cells. The large luteal cell population displayed an increase in total cellular protein content while the small cell type did not change with luteal development. In addition, the large luteal cells expressed proteins unique to or elevated in that cell type. Analysis by two-dimensional polyacrylamide gel electrophoresis revealed that the large cell-specific proteins had molecular masses of 23 K and 32 K and that a 14 kilodalton (kDa) protein was elevated in the large cell type relative to the small cells. The small luteal cell on day 3 of pregnancy expressed a 36 kDa protein which was barely detectable in the large cell. Immunocytochemical and Western analysis indicated that the large luteal cells contain 5.3-fold more SCP2 (P < 0.05) and 5.6-fold more P450scc (P < 0.001) relative to the small cell type. Immunocytochemical staining of adrenodoxin and adrenodoxin reductase indicate these proteins were elevated in the large cell as well. Human CG administration stimulated P450(17)alpha expression mainly in the large luteal cell population. The results of this investigation indicate, for the first time, that the large luteal cell of the rat, in contrast to the small cell type, undergoes a dramatic increase in protein content with luteal development, and that with this increase in cell size there is a concomitant increase in the large cell capacity to produce steroids. This occurs as a direct result of the enhanced expression of SCP2, P450scc, adrenodoxin and adrenodoxin reductase, proteins specifically required to transport and process cholesterol for steroid production in the large luteal cell.