Immunolocalization of tissue inhibitor of metalloproteinases-1 within ovine periovulatory follicular and luteal tissues

Cellular and molecular mechanisms of the preovulatory follicle differenciation and ovulation: What do we know in the mare relative to other species

Terminal follicular differentiation and ovulation are essential steps of reproduction. They are induced by the increase in circulating LH, and lead to the expulsion from the ovary of oocytes ready to be fertilized. This review summarizes our current understanding of cellular and molecular pathways that control ovulation using a broad mammalian literature, with a specific focus to the mare, which is unique in some aspects of ovarian function in some cases. Essential steps and key factors are approached. The first part of this review concerns LH, receptors and signaling, addressing the description of the equine gonadotropin and cloning, signaling pathways that are activated following the binding of LH to its receptors, and implication of transcription factors which better known are CCAAT-enhancer-binding proteins (CEBP) and cAMP response element-binding protein (CREB). The second and major part is devoted to the cellular and molecular actors within follicular cells during preovulatory maturation. We relate to 1) molecules involved in vascular permeability and vasoconstriction, 2) involvement of neuropeptides, such as kisspeptin, neurotrophins and neuronal growth factor, neuropeptide Y (NPY), 3) the modification of steroidogenesis, steroids intrafollicular levels and enzymes activity, 4) the local inflammation, with the increase in prostaglandins synthesis, and implication of leukotrienes, cytokines and glucocorticoids, 5) extracellular matrix remodelling with involvement of proteases, antiproteases and inhibitors, as well as relaxin, and finaly 6) the implication of oxytocine, osteopontin, growth factors and reactive oxygen species. The third part describes our current knowledge on molecular aspect of in vivo cumulus-oocyte-complexe maturation, with a specific focus on signaling pathways, paracrine factors, and intracellular regulations that occur in cumulus cells during expansion, and in the oocyte during nuclear and cytoplasmic meiosis resumption. Our aim was to give an overall and comprehensive map of the regulatory mechanisms that intervene within the preovulatory follicle during differentiation and ovulation.

Expression pattern of matrix metalloproteinases changes during folliculogenesis in the cat ovary

Matrix metalloproteinase (MMP) has been implicated as having roles in ovarian folliculogenesis. Here, we determined the expression pattern of six MMPs (MMP1, MMP2, MMP3, MMP7, MMP9 and MMP13) and their endogenous tissue inhibitor, TIMP1, during cat follicle growth. Different developmental stage follicles were mechanically isolated and gene expression analysed by real-time qPCR while MMP1, 2, 9 and 13 localization was determined by immunohistochemistry. With the exception of MMP13, the amount of MMP mRNA was lowest in primordial follicles and increased thereafter. Peak levels were detected in early antral follicles for MMP1 (72.2-fold increase above primordial follicle amount), MMP2 (10-fold), MMP3 (57-fold) and MMP9 (2.8-fold). MMP7 transcripts increased 2-fold by the primary follicle stage and then plateaued. MMP13 mRNA peaked in primary follicles (2.5-fold) and was lower in more advanced counterparts. TIMP1 sharply increased (6-fold) in secondary follicles and gradually declined in the later stages. MMP1 and MMP9 expression were expressed in the granulosa cells of all follicle stages. MMP2 was immunoreactive in early and antral follicles, especially at granulosa cells adjacent to the antral cavity. By contrast, the MMP13 was weakly detected in primary follicles onward. In summary, there are distinctive and consistent changes in MMPs and TIMP1 expression during follicle development, suggesting that these enzymes play one or more roles in cat folliculogenesis. In particular, high mRNA and protein expression levels of MMP1 and MMP2, especially at the antral stage, indicate that these enzymes likely are involved in antrum formation and expansion.

Ovarian matrix metalloproteinases are differentially regulated during the estrous cycle but not during short photoperiod induced regression in Siberian hamsters (Phodopus sungorus)

BACKGROUND

Matrix metalloproteinases (MMPs) are implicated as mediators for ovarian remodeling events, and are involved with ovarian recrudescence during seasonal breeding cycles in Siberian hamsters. However, involvement of these proteases as the photoinhibited ovary undergoes atrophy and regression had not been assessed. We hypothesized that 1) MMPs and their tissue inhibitors, the TIMPs would be present and differentially regulated during the normal estrous cycle in Siberian hamsters, and that 2) MMP/TIMP mRNA and protein levels would increase as inhibitory photoperiod induced ovarian degeneration.

METHODS

MMP-2, -9, -14 and TIMP-1 and -2 mRNA and protein were examined in the stages of estrous (proestrus [P], estrus [E], diestrus I [DI], and diestrus II [DII]) in Siberian hamsters, as well as after exposure to 3, 6, 9, and 12 weeks of inhibitory short photoperiod (SD).

RESULTS

MMP-9 exhibited a 1.6-1.8 fold decrease in mRNA expression in DII (p<0.05), while all other MMPs and TIMPs tested showed no significant difference in mRNA expression in the estrous cycle. Extent of immunostaining for MMP-2 and -9 peaked in P and E then significantly declined in DI and DII (p<0.05). Extent of immunostaining for MMP-14, TIMP-1, and TIMP-2 was significantly more abundant in P, E, and DI than in DII (p<0.05). Localization of the MMPs and TIMPs had subtle differences, but immunostaining was predominant in granulosa and theca cells, with significant differences noted in staining intensity between preantral follicles, antral follicles, corpora lutea, and stroma classifications. No significant changes were observed in MMP and TIMP mRNA or extent of protein immunostaining with exposure to 3, 6, 9, or 12 weeks of SD, however protein was present and was localized to follicular and luteal steroidogenic cells.

CONCLUSIONS

Although MMPs appear to be involved in the normal ovarian estrus cycle at the protein level in hamsters, those examined in the present study are unlikely to be key players in the slow atrophy of tissue as seen in Siberian hamster ovarian regression.

Evidence for a potential role of neuropeptide Y in ovine corpus luteum function

Neuropeptide Y (NPY) is a neurohormone that is typically associated with food intake, but it has also been reported to affect the production of progesterone from luteal tissue in vitro. However, NPY has not been previously immunolocalized in the ovine ovary or in the corpus luteum (CL) of any species, and the effects of this neurohormone on luteal function in vivo are not known. Thus, we performed fluorescent immunohistochemistry (IHC) to localize NPY in the ovine ovary and used avidin-biotin immunocytochemistry (ICC) to further define the intracellular localization within follicles and the CL. We then infused NPY directly into the arterial supply of the autotransplanted ovaries of sheep to determine the in vivo effect of exogenous NPY on ovarian blood flow and on the luteal secretion rate of progesterone and oxytocin. Immunohistochemistry revealed that the NPY antigen was localized to cells within the follicles and CL, in the nerve fibers of the ovarian stroma, and in the vessels of the ovarian hilus. In the follicle, the NPY antigen was localized to nerves and vessels within the theca interna layer, and strong staining was observed in the granulosal cells of antral follicles. In the CL, NPY was localized in large luteal cells and in the vascular pericytes and/or endothelial cells of blood vessels, found dispersed throughout the gland and within the luteal capsule. In vivo incremental infusions of NPY at 1, 10, 100, and 1,000 ng/min, each for a 30-min period, into the arterial supply of the transplanted ovary of sheep bearing a CL 11 d of age increased (P< or =0.05) ovarian blood flow. The intra-arterial infusions of NPY also increased (P< or =0.05) in a dose-dependent manner the secretion rate of oxytocin, which was positively correlated (P< or =0.05) with the observed increase in ovarian blood flow. The infusions of NPY had a minimal effect on the secretion rate of progesterone, and similar intra-arterial infusions of NPY into sheep with ovarian transplants bearing a CL over 30 d of age had no significant effect on ovarian blood flow or on the secretion rate of progesterone. These results suggest that NPY acts on the luteal vascular system and the large luteal cells to rapidly stimulate blood flow and the secretion of oxytocin, respectively, which collectively implies a putative role for NPY during the process of luteolysis when increasing amounts of oxytocin are secreted from the ovine CL in response to uterine pulses of prostaglandin F2alpha.

Morphological characteristics of the bovine corpus luteum during the estrous cycle and pregnancy

The corpus luteum, one of the biological clocks of the estrous cycle and pregnancy, is known foremost for its production of progesterone that blocks the pituitary release of gonadotropins and prepares the uterus for a pregnancy. The cellular sources of this progesterone are the steroidogenic small and large luteal cells. Other luteal cells that are not steroidogenic, but are believed to have an important role in the function of this gland are the fibroblast, macrophages and endothelial cells. The most prominent luteal cell is the large steroidogenic cell characterized by an abundance of smooth endoplasmic reticulum and densely packed spherical mitochondria that are indicative of its contribution to most of the circulating progesterone believed to be constitutively secreted and not under the control of LH. Other distinguishing features of the large luteal cell are the presence of rough endoplasmic reticulum, prominent Golgi, and secretory granules that are indicative of endocrine cells. This cell undergoes dynamic changes across the estrous cycle and pregnancy, believed to reflect a change in progesterone and protein secretion that will eventually influence a successful pregnancy or another ovulation if pregnancy fails. The morphological characteristics of the bovine luteal cells are the focus of this review.

Temporal and spatial expression of tissue inhibitors of metalloproteinases 1 and 2 (TIMP-1 and -2) in the bovine corpus luteum

The matrix metalloproteinases (MMPs) and their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs), may mediate the dramatic structural and functional changes in the corpus luteum (CL) over the course of its life span. In addition to regulating MMP activity, TIMPs are also involved in a variety of cellular processes, including cell proliferation and steroidogenesis. In a series of initial studies, we determined that matrix metalloproteinase inhibitory activity was present in protein extracts from early (4 days old, estrus = day 0), mid (10-12 days old) and late (16 days old) CL (n = 3 for each stage). Reverse zymography revealed four metalloproteinase inhibitory protein bands with relative molecular masses that are consistent with those reported for TIMP-1 to -4. In order to gain a better understanding of TIMPs and their role in luteal function, we further characterized this inhibitory activity with a particular focus on the temporal and spatial expression of TIMP-1 and TIMP-2 in the bovine CL. Northern blotting revealed that the TIMP-1 transcript (0.9 kb) was expressed at a higher (p < 0.05) level in early and mid cycle CL than in the late stage. In contrast, two TIMP-2 mRNA species, one major 1 kb species and one minor 3.5 kb species, were significantly (p < 0.05) increased in the mid and late cycle CL than in the early. Western blotting analyses demonstrated no differences in TIMP-1 (29 kDa) protein levels between early and mid stages, while its levels decreased (p < 0.05) from the mid to late stage CL. Conversely, TIMP-2 (22 kDa) protein was detected at a low level in the early CL, but significantly (p < 0.05) increased in the mid and late stages. Immunohistochemistry revealed that both TIMP-1 and -2 were localized to large luteal cells from all three ages of CL. TIMP-1 was also localized in capillary smooth muscle cells, while TIMP-2 was restricted to the endothelial cells in the capillary compartment. In conclusion, the different temporal expression patterns of TIMP-1 and TIMP-2 suggest that TIMP-1 may be important for luteal formation and development, while TIMP-2 may play significant roles during luteal development and maintenance. Furthermore, the distinct localization of these two inhibitors in the vascular compartment indicates that they may serve diverse physiological functions during different stages of luteal angiogenesis.

The matrix metalloproteinase system: changes, regulation, and impact throughout the ovarian and uterine reproductive cycle

The ovary and uterus undergo extensive tissue remodeling throughout each reproductive cycle. This remodeling of the extracellular environment is dependent upon the cyclic hormonal changes associated with each estrous or menstrual cycle. In the ovary, tissue remodeling is requisite for growth and expansion of the follicle, breakdown of the follicular wall during the ovulatory process, transformation of the postovulatory follicle into the corpus luteum, as well as the structural dissolution of the corpus luteum during luteal regression. In the uterus, there is extraordinary turnover of the endometrial connective tissue matrix during each menstrual cycle. This turnover encompasses the complete breakdown and loss of this layer, followed by its subsequent regrowth. With implantation, extensive remodeling of the uterus occurs to support placentation. These dynamic changes in the ovarian and uterine extracellular architecture are regulated, in part, by the matrix metalloproteinase (MMP) system. The MMP system acts to control connective tissue remodeling processes throughout the body and is comprised of both a proteolytic component, the MMPs, and a regulatory component, the associated tissue inhibitors of metalloproteinases. The current review will highlight the key features of the MMPs and tissue inhibitors of metalloproteinases, focus on the changes and regulation of the MMP system that take place throughout the estrous and menstrual cycles, and address the impact of the dynamic tissue remodeling processes on ovarian and uterine physiology.

Expression of gelatinases and their tissue inhibitors in rat corpus luteum during pregnancy and postpartum

Extensive tissue remodeling occurs in the corpus luteum (CL) during both formation and luteolysis. Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are believed to play pivotal roles in these processes. In the present study, to evaluate the potential roles of matrix degrading proteases in luteal development and regression, we examined gelatinases and TIMP-1, -2, -3 mRNA expressions, as well as gelatinase activity in rat CL during pregnancy and postpartum using Northern blot, in situ hybridization, and gelatin zymography, respectively. The results showed that MMP-2 mRNA was only expressed at the early stages of pregnancy; TIMP-2 mRNA was highly expressed at the early and late pregnancy and day 1 postpartum, but could not be detected during the mid-phase of pregnancy; TIMP-3 mRNA expression was abundant during early pregnancy and peaked at day 7, but was absent from other time points examined. MMP-9 and TIMP-1 mRNAs in rat CL were below detectable level in the current study. Furthermore, the active MMP-2 was only present during the early stages of pregnancy, and no MMP-9 activity was observed in the zymogram. Taken together, our results suggest that MMP-2 and TIMP-3 may have functional roles in rat luteal formation, while TIMP-2 may be implicated in both formation and regression of the pregnant CL.

Effect of the preovulatory gonadotropin surge on matrix metalloproteinase (MMP)-14, MMP-2, and tissue inhibitor of metalloproteinases-2 expression within bovine periovulatory follicular and luteal tissue

The matrix metalloproteinases (MMPs) have been implicated in the ovulatory process, but the specific roles of individual MMPs are unclear. This study examined the effect of the preovulatory gonadotropin surge on localization and regulation of MMP-2, MMP-14, and tissue inhibitor of metalloproteinases-2 (TIMP-2) mRNA and MMP-2 and TIMP-2 activity in bovine preovulatory follicles and new corpora lutea (CL). Ovaries containing ovulatory follicles or new CL were collected at approximately 0, 6, 12, 18, 24, and 48 h (CL) after a GnRH-induced gonadotropin surge. Messenger RNA for TIMP-2 and MMP-14 increased within 6 and 24 h of the gonadotropin surge, respectively, whereas MMP-2 mRNA was constitutively expressed. Activity for MMP-2 in follicular fluid and follicle homogenates was not changed, but follicular fluid TIMP-2 activity increased in response to the gonadotropin surge. Messenger RNA for MMP-2 was localized to the thecal layer of bovine preovulatory follicles, whereas MMP-14 mRNA was localized primarily to the thecal layer and adjacent ovarian stroma. Expression of MMP-14 was also observed in the granulosal layer after the gonadotropin surge. In contrast, TIMP-2 mRNA was localized predominantly to the granulosal layer with intense expression in the antral portion of the granulosal layer in response to the gonadotropin surge. These data support the hypothesis that increased expression of MMP-14 and TIMP-2 may help regulate follicle rupture and/or the ovulatory follicle-CL transition in cattle.

Ovarian tissue remodeling: role of matrix metalloproteinases and their inhibitors

Follicular formation, growth or atresia, and ovulation as well as luteal formation and subsequent regression are dependent upon cyclical remodeling of the extracellular matrix (ECM). The proteinaceous and nonproteinaceous components of the ECM provide the tissue specific, extracellular architecture to which cells attach. Furthermore, the ECM modulates cellular activities through cellular surface receptors and serves as a reservoir for specific growth factors, cytokines, and binding proteins. The ability of the ECM to direct the proliferation, differentiation and function of cells implicates ECM remodeling in normal ovarian function. Specific components of the ECM are cleaved by matrix metalloproteinases (MMPs) whose activities are specifically inhibited by tissue inhibitors of metalloproteinases (TIMPs). MMPs are zinc- and calcium-dependent enzymes that collectively degrade proteinaceous components of the ECM. Controlled turnover of ECM by MMPs and TIMPs may be essential for creating and (or) preserving microenvironments conducive to follicular and luteal function and is likely dependent upon the ratio of enzyme to inhibitor. To date, most studies have focused upon correlating ovarian expression of MMPs and TIMPs with various stages of the reproductive cycle. From these studies, many potential key regulators of ovarian ECM remodeling have been identified. This review presents evidence for the involvement of MMPs and TIMPs in ECM remodeling associated with follicular and luteal function.

Analysis of luteal tissue inhibitor of metalloproteinase-1, -2, and -3 during prostaglandin F(2alpha)-induced luteolysis

Increased matrix metalloproteinase (MMP) expression and activities help to mediate tissue involution through increasing extracellular matrix remodeling and promoting dedifferentiation and, ultimately, apoptosis. Therefore, we hypothesized that prostaglandin (PG) F(2alpha) administration would decrease expression of the tissue inhibitor of metalloproteinase (TIMP)-1, -2, and -3 and effectively increase the MMP:TIMP ratio, leading to glandular involution. In experiment 1, we tested the effects of PGF(2alpha) administration (Day 10 postestrus; Day 0 = estrus) on luteal TIMP-1, -2, and -3 mRNA and protein expression. Corpora lutea were collected at 0, 15, or 30 min or at 1, 2, 4, 6, 12, 24, and 48 h following PGF(2alpha) administration (n = 3-9 animals/time point). Following PGF(2alpha) administration, TIMP-1 mRNA levels decreased (P < 0.05) at 1 and 2 h relative to 0 h (controls), then increased to levels greater than controls at 4 and 6 h. In contrast, TIMP-2 and -3 mRNA levels did not decrease following PGF(2alpha) administration. The TIMP-1, -2, and -3 proteins were localized to large luteal cells (LLCs) within control (untreated) tissues. However, histodepletion of TIMP-1 within LLCs was evident within 30 min (earliest time point collected) following PGF(2alpha) injection and continued through 48 h. Luteal concentration of TIMP-1, as determined by RIA, was decreased (P < 0.05) by 15 min (earliest time point collected) following PGF(2alpha) administration and remained low through 48 h. In contrast, TIMP-2 and -3 immunolocalization was not altered by PGF(2alpha) administration. Experiment 2 was conducted to determine if PGF(2alpha) could initiate the preceding changes in TIMP-1 in early (Day 3) corpora lutea that can bind PGF(2alpha) but are refractory to its luteolytic effects. Serum concentrations of progesterone and luteal concentrations of TIMP-1 mRNA and protein were similar at 0 and 6 h after PGF(2alpha) injection on Day 3 postestrus. These data suggest that an early and sustained effect of PGF(2alpha) is the specific depletion of TIMP-1 within LLCs that are capable of responding to the luteolytic action of PGF(2alpha). This action may increase the MMP:TIMP-1 ratio, creating an environment that favors extracellular matrix degradation and, thereby, facilitates both functional and structural regression.

Matrix metalloproteinase (2, 9, and 14) expression, localization, and activity in ovine corpora lutea throughout the estrous cycle

Members of the matrix metalloproteinase (MMP) family collectively degrade extracellular matrix (ECM) and help regulate luteal function. The objectives of these experiments were to characterize the mRNA expression, localization, and activity of MMPs 2, 9, and 14 in ovine corpora lutea (CL). Ovine CL were collected on Days 2, 4, 10, and 15 of the estrous cycle (Day 0 = estrus). Messenger RNA transcripts for MMPs 2 and 14 were detected using Northern analysis; however, expression of MMP-9 was undetectable. Expression of MMP-14 mRNA (membrane type-1 MMP) was increased (P < 0.05) on Day 4; whereas, expression of MMP-2 mRNA was highest (P < 0.05) on Day 10, which corresponded to the observed increases in gelatinolytic activity in luteal homogenates as measured by a fluroscein-labeled gelatin substrate assay. MMP 2 and 9 proteins were localized predominantly to large luteal cells (LLCs), whereas MMP-14 was localized primarily to cells other than LLCs as demonstrated by immunohistochemistry. Immunolocalization of MMP-2 to putative endothelial cells was also observed on Day 15. Localization of MMP activity was determined using in situ zymography. Luteal tissues contained gelatinolytic activity primarily localized pericellularly to various cell types, including LLCs. These results support the hypothesis that ECM remodeling occurs throughout the luteal phase and may help potentiate cellular migration, differentiation, angiogenesis, and growth factor bioavailability.

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.

Tumor necrosis factor alpha regulates collagenolytic activity in preovulatory ovine follicles: relationship to cytokine secretion by the oocyte-cumulus cell complex

The pleiotropic cytokine tumor necrosis factor (TNF)-alpha has been implicated in the mechanism of ovulation. Experiments were designed to test the hypothesis that TNF-alpha secreted from the oocyte-cumulus cell complex stimulates follicular collagenase production and thereby contributes to ovarian wall degradation and ovulatory rupture. Proestrous ewes were treated with GnRH to synchronize the onset of the gonadotropin surge; ovulation occurs approximately 24 h later. There was an increase in TNF-alpha (immunoassay) in antral fluid of preovulatory follicles at 18 h after GnRH, which was related to tissue collagenolytic bioactivity (radiolabeled type I substrate digestion by enzymatic extract) and collagen (hydroxyproline) depletion. Intrafollicular injection of TNF-alpha antibodies at 12 h after GnRH negated the rise in follicular collagenolytic bioactivity (and is known to block ovulation in the sheep). Moreover, collagenase production was enhanced when follicular tissues (0 h GnRH) were incubated (6 h) with recombinant TNF-alpha; this effect was abolished by the transcriptional inhibitor actinomycin D. Secretion of TNF-alpha by oocyte-cumulus cell complexes isolated from preovulatory follicles simulated the in vivo circumstance. Immunostaining indicated that TNF-alpha was confined mainly to the oocyte before GnRH administration, accumulated in cumulus cells during the mid-to-late preovulatory period, and was expended with the imminent approach of ovulation. To our knowledge, this is the first report specifying that up-regulation of collagenase expression is a target mode of TNF-alpha action in preovulatory follicles. The oocyte-cumulus cell complex is an apparent source of soluble TNF-alpha.

Expression of matrix metalloproteinases and their tissue inhibitor messenger ribonucleic acids in macaque periovulatory granulosa cells: time course and steroid regulation

Progesterone appears essential for ovulation and luteinization of the primate follicle, but specific gene targets of progesterone action remain elusive. Limited evidence supports a role for progesterone in the induction of collagenolytic activity in the periovulatory follicle of primate and nonprimate species. This study was designed to elucidate the pattern of expression and progesterone regulation of mRNAs for the matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in macaque granulosa cells during controlled ovarian stimulation cycles before (0 h) and after (up to 36 h) administration of an ovulatory hCG bolus. Levels of mRNAs for interstitial collagenase, gelatinase A, matrilysin, TIMP-1 and TIMP-2 increased (p < 0.05) within 12 h of hCG, while gelatinase B mRNA increased later, by 36 h after hCG. Administration of a 3beta-hydroxysteroid dehydrogenase inhibitor (Trilostane [TRL]) during hCG treatment decreased (p < 0.05) mRNA levels for interstitial collagenase, gelatinase B, matrilysin, TIMP-1, and TIMP-2. Progestin (R5020) replacement during hCG+TRL treatment returned interstitial collagenase and TIMP-1 mRNAs to control levels. These data suggest that one action of progesterone, and possibly other steroids, in the cascade of events leading to ovulation and luteinization of the primate follicle is to regulate the expression of specific ovarian proteases and protease inhibitors.

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.

Effects of elevated concentrations of prostaglandin F2 alpha on pregnancy rates in progestogen supplemented cattle

An experiment was performed to determine the effect of elevated prostaglandin F2 alpha (PGF2 alpha) on pregnancy rates of progestogen-treated bred cows in the presence or absence of luteal tissue. Ninety-one beef cows were bred (Day 0) and assigned randomly to receive either 3 mL saline (CON), 15 mg PGF2 alpha, or 15 mg PGF2 alpha + lutectomy (P + L) administered intramuscularly (i.m.) at 8 h intervals on either Days 5-8, 10-13, or 15-18 postbreeding. Lutectomies were performed by transrectal digital pressure before initiation of treatment on Day 5, 10, or 15 for the respective treatment groups. All cows were fed 4 mg/day of melengesterol acetate from two days prior to initiation of treatment until Day 30 postbreeding. Mean concentrations of 13,14-dihydro-15-keto-PGF2 alpha (PGFM) were increased in cows administered PGF2 alpha and P + L treatments (398 +/- 23 and 413 +/- 22 pg/ml, respectively; p < 0.01) compared to the CON group (80 +/- 29 pg/ml) regardless of treatment group. Mean concentrations of oxytocin (OT) were increased in cows given PGF2 alpha on Day 10 and 15 (p < or = 0.0001) and tended to be increased on d 5 when compared to CON and P + L treatment groups on Day 5. Pregnancy rates were reduced (p < or = 0.03) in the PGF2 alpha treatment group (23%) and by Day 5-8 compared to CON (72%). Lutectomy tended to improve pregnancy rate in P + L (5-8; 55%) compared to PGF2 alpha (5-8; p = 0.1). Pregnancy rates tended (p < or = 0.07) to increase in the PGF2 alpha treatment groups on Days 5-8 treatment (23%, 50%, and 60% for Days 5-8, 10-13, and 15-18, respectively). The later the treatments were initiated pregnancy rates did not differ between treatments given on Days 10-13 and 15-18. In conclusion, the most susceptible period of embryonic growth to the negative effects of PGF2 alpha was during morula to blastocyst development. Removal of luteal tissue diminishes the negative effects of PGF2 alpha through interruption of the luteal oxytocin-uterine PGF2 alpha feedback loop.

Ontogenies of messenger RNA encoding tissue inhibitor of metalloproteinases 1 and 2 within bovine periovulatory follicles and luteal tissue

Tissue inhibitors of metalloproteinases 1 and 2 (TIMP-1 and TIMP-2) are important regulators of extracellular matrix remodeling and also possess growth factor activity. The objective of these studies was to characterize TIMP-1 and TIMP-2 mRNA expression by bovine periovulatory follicles/ corpora hemorrhagica (Experiment 1) and luteal tissue (Experiment 2). In Experiment 1, beef heifers (n = 27) were ovariectomized at-16 (n = 6), 0 (n = 5), 8 (n = 3), 16 (n = 4), 24 (n = 4), or 48 (n = 5) hr relative to a gonadotropin-releasing hormone induced gonadotropin surge (40 hr after prostaglandin F2 alpha-induced luteolysis). Total cellular RNA was isolated from the large steroidogenically active follicle or corpus hemorrhagicum obtained from each animal, and the expression of TIMP-1 and TIMP-2 mRNA was subsequently examined by northern and dot blot analysis. The expression of TIMP-1 or TIMP-2 mRNa did not differ in preovulatory follicles collected at -16 vs. 0 hr. Concentrations of both TIMP-1 and TIMP-2 mRNA (picograms per microgram of tissue DNA) were increased (P < 0.05) at 8 hr postgonadotropin surge, had declined to presurge levels by 24 hr (P < 0.05), and were increased (P < 0.05) in corpora hemorrhagica collected at 48 hr after a gonadotropin surge. In Experiment 2, corpora lutea were collected from beef heifers on Days 4, 10, 15 (n = 4 each), or 19 (n = 3) postestrus (Day 0 = estrus). Concentrations of TIMP-1 mRNA (picograms per microgram of tissue DNA) were greater in corpora lutea collected on Day 4 (P < 0.05) vs. Day 10, 15, or 19. Concentrations of TIMP-2 mRNA increased (P < 0.05) from Day 4 to 15 and decreased (P < 0.05) by Day 19. We conclude that: 1) during the periovulatory period, the ontogenies of TIMP-1 and TIMP-2 mRNA expression are similar, whereas 2) during luteal phase, TIMP-1 mRNA expression is maximal during the early luteal phase, whereas concentrations of TIMP-2 mRNA peak during the midluteal phase. TIMP-1 and TIMP-2 may play important roles in the regulation of extracellular matrix remodeling during the periovulatory period and the subsequent luteal phase.