Species-related differences in the mechanism of apoptosis during structural luteolysis

Expression and localization of anti-Müllerian hormone and its receptors in bovine corpus luteum

Although anti-Müllerian hormone (AMH) is involved in the regulation of granulosa cell function in female animals, its role in tissues other than ovarian follicles remains poorly understood. It has also been suggested that cows with high circulating AMH concentrations have increased fertility; however, the mechanism has not been elucidated. This study was conducted to identify the presence of the AMH-signaling system and its target cells in the bovine corpus luteum formed from an ovulated follicle. Immunoblotting revealed that the proteolytically cleaved C-terminal region in AMH (AMHC), a biologically active peptide, was present in trace amounts in the early corpus luteum and significantly increased during the mid to regressed stages. AMHC and cleaved N-terminal region (AMHN) in AMH generate a noncovalent isoform that improves the activity of AMH signaling. An immunohistochemical analysis revealed that AMHC, AMHN, and type II AMH receptor (AMHR2) were localized to luteal cells during the entire estrous cycle. AMH in the corpus luteum seemed to be newly synthesized since AMH expression was detected. These findings suggest that AMH signaling is involved in the regulation of luteal cell function through an autocrine and post-translational processing mechanism. The level of AMHR2 and mRNA expression of AMHR2 and type I AMH receptors (activin-like kinase 2, 3, and 6) were highest in the mid stage. Thus, AMH signaling in the corpus luteum may also be regulated by changes in the receptor levels. Since the transforming growth factor-beta superfamily, to which AMH belongs, is a multifunctional polypeptide growth factor, further studies are needed to evaluate whether AMH signaling has a role in facilitating or inhibiting luteal cell functions.

Autophagic and apoptotic proteins in goat corpus luteum and the effect of Adiponectin/AdipoRon on luteal cell autophagy and apoptosis

The most abundant adipokine Adiponectin (APN) is present in ovaries. AdipoRon is a small molecule oral APN receptor agonist that binds and activates APN receptors. However, the function of APN/AdipoRon in regulation of luteal cell processes has not been elucidated. To investigate autophagic and apoptotic proteins in goat CLs and effects of APN/AdipoRon on goat luteal autophagy and apoptosis, goat CLs were collected during the early, mid and late luteal stages of the estrous cycle to evaluate autophagic and apoptotic protein patterns. LC3B, Beclin 1, Caspase-3 and Bax/Bcl-2 as well as p-AMPK were differentially abundant at different stages of CL development. All these proteins were primarily localized in large and small luteal steroidogenic cells. Then, isolated luteal steroidogenic cells were evaluated to ascertain the functions and mechanism of APN/AdipoRon in luteal autophagy and apoptosis. Treatment with AdipoRon (25 and 50 μM) and APN (1 μg/mL) for 48 h resulted in a decrease in cell viability and P4 level, increased autophagic and apoptotic proteins. Treatment with AdipoRon (25 μM) led to rapid and transient p-AMPK activation, with p-AMPK elevated at 30 min to 1 h with there being a return to a basal concentration at 2 h post-treatment. Moreover, treatment with AdipoRon led to an increase in autophagy by activating AMPK, which was markedly reduced with treatment with an AMPK inhibitor Compound C and siAMPK, however, abundances of apoptotic proteins were not affected by these treatments. In conclusion, autophagy and apoptosis are involved in the structural regression of goat CL. APN/AdipoRon led to a lesser cell viability and P4 concentration, and activated autophagy through induction of the AMPK while there was induction of apoptosis through an AMPK - independent pathway in goat luteal cells.

Prostaglandins as local regulators of ovarian physiology in ruminants

Prostaglandins are synthesized from arachidonic acid through the catalytic activities of cyclooxygenase, while the production of different prostaglandin types, prostaglandin F2 alpha (PGF) and prostaglandin E2 (PGE), are regulated by specific prostaglandin synthases (PGFS and PGES). Prostaglandin ligands (PGF and PGE) bind to specific high-affinity receptors and initiate biologically distinct signalling pathways. In the ovaries, prostaglandins are known to be important endocrine regulators of female reproduction, in addition to maintaining local function through autocrine and/or paracrine effect. Many research groups in different animal species have already identified a variety of factors and molecular mechanisms that are responsible for the regulation of prostaglandin functions. In addition, prostaglandins stimulate their intrafollicular and intraluteal production via the pathway of prostaglandin self-regulation in the ovary. Therefore, the objective of the review article is to discuss recent findings about local regulation patterns of prostaglandin ligands PGF and PGE during different physiological stages of ovarian function in domestic ruminants, especially in bovine. In conclusion, the discussed local regulation mechanisms of prostaglandins in the ovary may stimulate further research activities in different methodological approaches, especially during final follicle maturation and ovulation, as well as corpus luteum formation and function.

Plasma cell-free DNA concentration increases during luteolysis in beef cows

During cell death, DNA is fragmented and reaches the bloodstream in the form of cell-free DNA (cfDNA). Luteal cells must undergo an apoptotic process during structural luteolysis to begin a new oestrous cycle. We hypothesized that cfDNA concentrations would increase when inducing luteolysis by applying prostaglandin F2α (PGF2α) analog to the cycling cow. Multiparous non-pregnant and non-lactating Angus cows (Bos taurus; n = 15) were synchronized using the 7-day CoSynch + CIDR protocol. Ten days after oestrus was detected, two treatments were applied (PGF2α, n = 10; or Con, n = 5). Twice a day, grey mode and colour Doppler ultrasonography were used to calculate area (CL-A) and luteal blood perfusion (LBP%). Additionally, we collected one blood sample for plasma progesterone (P4) and cfDNA concentrations for four consecutive days. Data analysis was performed using the GLM procedure of SAS. The luteolysis induction was demonstrated by a decrease in P4 concentrations (p ≤ .01) and CL-A (p ≤ .01) in the PGF2α group after 12 h of the PGF2α injection. Reduction of LBP% (p ≤ .01) in the PGF2α group after 36 h of the injection. The concentration of cfDNA showed a significant increase (p = .05) after 48 h of the PGF2α application in the PGF2α group. In conclusion, cfDNA showed a significantly increased concentration after luteolysis induction, which can imply that cfDNA could be used as a luteolysis biomarker in plasma.

Functional and morphological maturation of the full-sized and mini-pig corpus luteum by programmed cell death mechanism

Introduction

The formation and function of the corpus luteum (CL) increase the likelihood of pregnancy and efficiently manage implantation. Apoptosis must occur at an appropriate time in the formation of the CL. This also affects its function. However, it is still unclear if the type of apoptosis affects the function.

Material and Methods

We conducted morphological analysis of the CL collected on day 15 between the middle and late oestrous phases of Yorkshire pigs and mini-pigs, and measured the difference in hormone expression and apoptosis using an immunoassay method and messenger RNA level.

Results

The CL cells were more uniform in the Yorkshire pigs than in the mini-pigs, and the composition of the CL was also fuller. The expression of luteinising hormone was higher in the Yorkshire pigs. Apoptosis and the rate of action of matrix metalloproteinases (MMPs) were different between the two pig types. Expression of MMPs was higher in the Yorkshire pigs than in the mini-pigs. However, the expression of caspase 3 and 20alpha-hydroxysteroid dehydrogenase, a progesterone inhibitor, was potentiated in the mini-pigs.

Conclusion

Autophagy throughout the CL was more extensive in the Yorkshire pigs than in the mini-pigs, suggesting that autophagy and cell reorganisation by MMPs were highly correlated. The occurrence of autophagy in the formation and function of the CL may affect the action of hormones and expression of cell reconstitution factors.

Prokineticin 1 is a novel factor regulating porcine corpus luteum function

Prokineticin 1 (PROK1) is a pleiotropic factor secreted by endocrine glands; however, its role has not been studied in the corpus luteum (CL) during pregnancy in any species. The present study aimed to investigate the contribution of PROK1 in regulating processes related to porcine CL function and regression: steroidogenesis, luteal cell apoptosis and viability, and angiogenesis. The luteal expression of PROK1 was greater on Days 12 and 14 of pregnancy compared to Day 9. PROK1 protein expression during pregnancy increased gradually and peaked on Day 14, when it was also significantly higher than that on Day 14 of the estrous cycle. Prokineticin receptor 1 (PROKR1) mRNA abundance increased on Days 12 and 14 of pregnancy, whereas PROKR2 elevated on Day 14 of the estrous cycle. PROK1, acting via PROKR1, stimulated the expression of genes involved in progesterone synthesis, as well as progesterone secretion by luteal tissue. PROK1-PROKR1 signaling reduced apoptosis and increased the viability of luteal cells. PROK1 acting through PROKR1 stimulated angiogenesis by increasing capillary-like structure formation by luteal endothelial cells and elevating angiogenin gene expression and VEGFA secretion by luteal tissue. Our results indicate that PROK1 regulates processes vital for maintaining luteal function during early pregnancy and the mid-luteal phase.

The Temporal Associations of B-Mode and Power-Doppler Ultrasonography, and Ovarian Steroid Changes of the Periovulatory Follicle and Corpus Luteum During Luteogenesis and Luteolysis in Jennies

This study aimed to determine the associations between B-mode and Power-doppler ultrasonography and ovarian steroids of the periovulatory follicle and respective corpus luteum (CL) during luteogenesis and luteolysis in jennies. Twenty-four periovulatory follicles/estrus of correspondent one inter-ovulatory interval (n = 12 jennies) were assessed in the study. B-mode ultrasonography and teasing were carried out once day until the detection of a periovulatory follicle (≥28 mm, uterine edema, and signs of estrus). Thereafter, jennies were monitored at 4-hour-intervals by B-mode and Power-doppler ultrasonography. Closer to ovulation, jennies were hourly checked. Each CL was checked daily from luteogenesis to luteolysis. Plasma concentrations of estradiol and progesterone were assessed daily with chemiluminescence immunoassay. Granulosa echogenicity and thickness increased from -36 hour to -1 hour before ovulation in 70% of follicles (P < .05) and were strongly associated with impending ovulation (r = 0.80 and r = 0.70, respectively). The follicular-wall blood flow increased from -72 to -24 hour pre-ovulation, while the estradiol concentration declined from 42 pg/mL by -72 hour to 31.6 pg/mL by 24 hour before ovulation (P < .05). The vascularization of the periovulatory follicle decreased from 62% (-36 hour) to 37% (-1 hour) before ovulation (P < .05). The CL vascularization and progesterone concentration gradually increased, reaching the peak at 11- and 10-day after the ovulation, respectively (P < .05). The CL vascularization started to decline 3 day before luteolysis, while progesterone concentrations started to drop 4 day before luteolysis (P < .05). In conclusion, the structural changes of the periovulatory follicle detected on B-mode and Power-doppler can be used to detect impending ovulation in donkeys; however, Power-doppler, but not B-mode ultrasonography, can be used to assess CL function in jennies.

Progesterone Induces Apoptosis and Steroidogenesis in Porcine Placental Trophoblasts

Placentation and placental steroidogenesis are important for pregnancy and maternal−fetal health. As pregnancy progresses, the main site of progesterone (P4) synthesis changes from the corpus luteum to the placenta, in which placental trophoblasts are the main cell type for P4 synthesis. Therefore, this study investigated the effects of P4 on apoptosis and steroidogenesis in porcine placental trophoblasts and the underlying molecular mechanisms. Porcine placental trophoblasts were treated with different concentrations of P4 for 48 h in a serum-free medium in vitro. Cell number, steroidogenesis, and relevant gene and protein expression levels were detected. A high dose of P4 (10.0 μM) significantly increased P4 (p < 0.01), androstenedione (p < 0.05), testosterone (p < 0.05), and estradiol (p < 0.05) production in porcine placental trophoblasts compared with that in control cells, while a low dose of P4 (1 × 10−3 μΜ) had no marked impact on steroid production. The mRNA expression of apoptosis-related genes (CASP3, CASP8, and Bax) (p < 0.05) and steroidogenesis-related genes (CYP11A1, CYP19A1, and StAR) (p < 0.01) was upregulated, and the expression of HSD3B and HSD17B4 was inhibited (p < 0.05) in the porcine placental trophoblasts treated with high doses of P4. Low doses of P4 had a lighter effect on gene expression than high doses. The expression of apoptosis-related proteins CASP3 (p < 0.05), and Bax (p < 0.01) and steroidogenesis-related proteins CYP19A1 (p < 0.05) and StAR (p < 0.01) was raised, but the proliferation-related protein CCND2 (p < 0.01) was downregulated in the pTr cells treated with high dose of P4. In comparison, a low dose of P4 inhibited the expression of Bax, CYP11A1 (all p < 0.01), and CCND2 (p < 0.05), but the expression of CASP3 (p < 0.05) and StAR (p < 0.01) was upregulated. In summary, excessive P4 can induce the apoptosis of porcine placental trophoblasts and lead to abnormal steroidogenesis in the placenta and hormone imbalance.

Analysis of changes in the proteomic profile of porcine corpus luteum during different stages of the oestrous cycle: effects of PPAR gamma ligands

CONTEXT

The corpus luteum (CL) is an endocrine gland in the ovary of mature females during the oestrous cycle and pregnancy. There is evidence of a relationship between the secretory function of the CL and PPARs.

AIMS

In this study, we investigated the changes in the proteome of the CL in relation to the phase of the oestrous cycle and the impact of PPARγ ligands on the proteomic profile of the CL during the mid- and late-luteal phase of the oestrous cycle.

METHODS

The porcine CL explants were incubated in vitro for 6h in the presence of PPARγ ligands (agonist pioglitazone, antagonist T0070907) or without ligands. Global proteomic analysis was performed using the TMT-based LC-MS/MS method.

KEY RESULTS

The obtained results showed the disparity in proteomic profile of the untreated CL - different abundance of 23 and 28 proteins for the mid- and late-luteal phase, respectively. Moreover, seven proteins were differentially regulated in the CL tissue treated with PPARγ ligands. In the mid-luteal phase, one protein, CAND1, was downregulated after treatment with T0070907. In the late-luteal phase, the proteins SPTAN1, GOLGB1, TP53BP1, MATR3, RRBP1 and SRRT were upregulated by pioglitazone.

CONCLUSIONS

Comparative proteomic analysis revealed that certain proteins constitute a specific proteomic signature for each examined phase. Moreover, the study showed that the effect of PPARγ ligands on the CL proteome was rather limited.

IMPLICATIONS

The results provide a broader insight into the processes that may be responsible for the structural luteolysis of the porcine CL, in addition to apoptosis and autophagy.

Regulatory changes of local produced prostaglandins in corpus luteum after experimentally induced luteolysis in the cow

The objective of the study was to evaluate the expression patterns of prostaglandin F2alpha (PGF), prostaglandin E2 (PGE), PGF receptor (FP), PGE receptors (EP2 and EP4), prostaglandin-endoperoxide synthase 2 (PTGS2) and prostaglandin synthases (PGFS and PGES) in corpora lutea (CL) during experimentally induced luteolysis in cow. The Fleckvieh cows in the mid-luteal phase (days 8-12, control group) were injected with cloprostenol (PGF analogue), and CL were collected by transvaginal ovariectomy before (days 8-12, control group) and at 0.5, 2, 4, 12, 24, 48 and 64 h after PGF application (n = 5 per group). The mRNA expression was determined by RT-qPCR, the hormone concentrations by enzyme immunoassay and localization by immunohistochemistry. PTGS2 gene expression increased significantly 2 h after PGF application, followed by continuous and significant downregulation afterwards. The PGF tissue concentration increased significantly just after PGF injection and again during structural luteolysis (after 12 h), whereas PGE concentration significantly decreased during structural luteolysis. The FP receptor mRNA decreased significantly at 2 h and again at 12 h after PGF. In contrast, EP4 receptor mRNA increased significantly just after the PGF application (0.5 h). The immunostaining of PGES and PTGS2 on day 15-17 shows numerous positive luteal cells, followed by lower activity afterwards on day 18 (luteolysis). In conclusion, the changes of examined prostaglandin family members in CL tissue after PGF application may be key components of the local mechanisms regulating the cascade of actions leading to functional and subsequent structural luteolysis in the bovine ovary.

Changes in Porcine Corpus Luteum Proteome Associated with Development, Maintenance, Regression, and Rescue during Estrous Cycle and Early Pregnancy

Corpus luteum (CL), a transitory gland, undergoes rapid growth in a limited time to produce progesterone (P4) followed by its regression. A complex molecular signaling is involved in controlling luteal P4 production. In the present study, 2D gel electrophoresis-based proteomics and in silico functional analysis were used to identify changes in key proteins and pathways in CL along the different stages of the estrous cycle as its development progresses from early (Day 3) to mid-luteal phase (Day 9), effective functioning (Day 12) followed by regression (Day 15) or, in the case of pregnancy, rescue of function (Day 15). A total of 273 proteins were identified by MALDI-MS/MS analysis that showed significant changes in abundances at different stages of CL development or regression and rescue. Functional annotation of differentially abundant proteins suggested enrichment of several important pathways and functions during CL development and function maintenance including cell survival, endocytosis, oxidative stress response, estradiol metabolism, and angiogenesis. On the other hand, differentially abundant proteins during CL regression were associated with decreased steroid synthesis and metabolism and increased apoptosis, necrosis, and infiltration of immune cells. Establishment of pregnancy rescues CL from regression by maintaining the expression of proteins that support steroidogenesis as pathways such as the super-pathway of cholesterol biosynthesis, RhoA signaling, and functions such as fatty acid metabolism and sterol transport were enriched in CL of pregnancy. In this study, some novel proteins were identified along CL development that advances our understanding of CL survival and steroidogenesis.

CHEMERIN as a modulator of angiogenesis and apoptosis processes in the corpus luteum of pigs: An in vitro study

The corpus luteum (CL) undergoes rapid changes, and its functional capabilities are influenced by processes such as angiogenesis and apoptosis. According to the literature, chemerin - a protein which participates in the regulation of energy homeostasis and the immune response, may also affect angiogenesis and apoptosis. Therefore, the aim of this study was to investigate the in vitro effect of chemerin on angiogenesis and apoptosis in porcine luteal cells (Lc) during specific phases related to CL physiology. Luteal cells were harvested from gilts during the early-, mid-, and late-luteal phases of the estrous cycle. The cells were preincubated for 48 h and incubated for 24 h with chemerin or a serum-free medium (controls). The abundance of angiogenesis- and apoptosis-related proteins was determined by ELISA in spent culture media, or by ELISA and Western Blot in protein extracts. The current study demonstrated that chemerin stimulates the production of VEGF-A and bFGF by porcine Lc and increases the protein abundance of angiogenic factors receptors (VEGFR1, VEGFR2, VEGFR3, FGFR1, FGFR2) in these cells. The study also revealed that chemerin exerts a modulatory effect (stimulatory/inhibitory, depending on the phase of the cycle) on the protein abundance of Fas, FasL, Bcl-2 and caspase-3 in porcine Lc. These results imply that chemerin may affect angiogenesis and apoptosis processes in the porcine CL, as evidenced by its modulatory effect of chemerin on the protein abundance of crucial angiogenesis- and apoptosis-related factors, observed in an in vitro study of porcine Lc.

Transcriptome profiling of different developmental stages of corpus luteum during the estrous cycle in pigs

To better understand the molecular basis of corpus luteum (CL) development and function RNA-Seq was utilized to identify differentially expressed genes (DEGs) in porcine CL during different physiological stages of the estrous cycle viz. early (EL), mid (ML), late (LL) and regressed (R) luteal. Stage wise comparisons obtained 717 (EL vs. ML), 568 (EL vs. LL), 527 (EL vs. R), 786 (ML vs. LL), 474 (ML vs. R) and 534 (LL vs. R) DEGs with log₂(FC) ≥1 and p < 0.05. The process of angiogenesis, steroidogenesis, signal transduction, translation, cell proliferation and tissue remodelling were significantly (p < 0.05) enriched in EL, ML and LL stages, where as apoptosis was most active in regressed stage. Pathway analysis revealed that most annotated genes were associated with lipid metabolism, translation, immune and endocrine system pathways depicting intra-luteal control of diverse CL function. The network analysis identified genes AR, FOS, CDKN1A, which were likely the novel hub genes regulating CL physiology.

[Clinical, ethologic, endokrinologic, and metabolic aspects of the peripartal period in pigs]

The aim of this review article is to provide an overview of the literature relevant to the peripartal period in swine. As in all other mammals, the farrowing process in pigs is divided into 3 phases (I-III; opening, expulsion, and postnatal stage), during which various essential endocrine and metabolic mechanisms initiate or maintain parturition. These include the hormones progesterone, cortisol, prostaglandin F_2α, oxytocin, estradiol, relaxin as well as electrolytes, enzymes, and metabolites such as calcium, magnesium, inorganic phosphate, glucose, creatine kinase, lactate, non-esterified free fatty acids, and β-hydroxybutyrate. Exogenous or endogenous disruptive factors may result in a delay or even stagnation of labor. For example, the form of husbandry may represent a possible exogenous disruptive factor. Endogenous disruptive factors may arise from insufficient storage and/or distribution of the above-mentioned labor-associated parameters. Subsequent dystocia leads to temporary or permanent consequences for maternal reproductive fitness and impairs piglet vitality at the time of birth, possibly resulting in lower survival rates.

In vivo response of the corpus luteum to progesterone treatment of gilts during early gestation

Supplementation of progesterone (P₄) in pregnant gilts increases concentrations of circulating P₄ and stimulates the secretory activity of the endometrium. In this study, there was examination of the consequences of exogenous P₄ administration on luteal P₄ content and the expression of genes related to the corpus luteum (CL) function. Gilts with gonadotropin-induced estrus were administered daily injections of corn oil (n = 8) or P₄ (n = 8) on days 3 through 10 after insemination. The animals were slaughtered on day 12 of pregnancy to obtain corpora lutea for real-time polymerase chain reaction analyses of selected genes and for enzyme immunoassay of P₄. Injections with P₄ had no effect on the concentration of P₄ and the relative abundance of mRNA transcripts of cholesterol transport-related proteins, steroidogenic enzymes, and receptors for luteotropic factors in the luteal tissue. The abundance of prostaglandin (PG) endoperoxide synthase 2, PGI2 synthase, PGI2 receptor, fibroblast growth factor 2, peroxisome proliferator-activated receptor γ, and tumor necrosis factor α receptor type I transcripts increased after P₄ treatment. In contrast, the relative abundance of angiopoietin 2 mRNA decreased in response to P₄ administration. In summary, P₄ supplementation in pregnant gilts does not affect luteal steroidogenesis but modulates the abundance of factors related to vascular function. Given that the endometrium is the main target tissue for P₄, an indirect uterine-mediated effect of exogenous P₄ on CL function is likely.

Transcription Analysis of the Chemerin Impact on Gene Expression Profile in the Luteal Cells of Gilts

Chemerin is a recently discovered adipokine that participates in the regulation of many physiological and disorder-related processes in mammals, including metabolism, inflammatory reactions, obesity, and reproduction. We investigated how chemerin affects the transcriptome profile of porcine luteal cells. The luteal cells were acquired from mature gilts. After the in vitro culturing with and without chemerin, the total RNAs were isolated and high-throughput sequencing was performed. Obtained datasets were processed using bioinformatic tools. The study revealed 509 differentially expressed genes under the chemerin influence. Their products take part in many processes, important for the functions of the corpus luteum, such as steroids and prostaglandins synthesis, NF-κB and JAK/STAT signal transducing pathways, and apoptosis. The expression of the CASP3, HSD3B7, IL1B, and PTGS2 genes, due to their important role in the physiology of the corpus luteum, was validated using the quantitative real-time polymerase chain reaction (qPCR) method. The qPCR confirmed the changes of gene expression. Chemerin in physiological concentrations significantly affects the expression of many genes in luteal cells of pigs, which is likely to result in modification of physiological processes related to reproduction.

Expression and localization of cellular FLICE-like inhibitory protein (cFLIP), an anti-apoptotic factor, in corpora lutea during the estrous cycle and pregnancy in Thai swamp buffalo <i>(Bubalus bubalis)</i>

In female mammals, luteal cells rapidly proliferate and form corpora lutea (CLs) after ovulation. The corpus luteum (CL) plays crucial roles in establishing and maintaining pregnancy. To gain further insights into the role of cellular FLICE-like inhibitory protein (cFLIP), an anti-apoptosis factor that is structurally similar to procaspase-8 but lacks proteolytic enzyme activity, we examined the expression in CLs of Thai swamp buffalos (Bubalus bubalis) during the early, mid, and late stage of the estrous cycle and pregnancy. cFLIP short form and long form (cFLIP<inf>S</inf> and cFLIP<inf>L</inf>, respectively) mRNA and protein levels were assessed by reverse transcription-polymerase chain reaction and western blotting, respectively. cFLIP<inf>S</inf> mRNA levels were low in the mid and late stages of the estrous cycle and increased during pregnancy (P < 0.05). cFLIP<inf>L</inf> mRNA was highly expressed in CLs during pregnancy and was lower in the mid and late stages of the estrous cycle. The level of cFLIP<inf>S</inf> protein was high in CLs during pregnancy and low levels were noted in the mid stage of the estrous cycle (P < 0.05). Higher levels of cFLIP<inf>L</inf> protein were demonstrated in CLs during pregnancy and lower levels were found in CLs during the early stage of the estrous cycle. Strong positive immunohistochemical staining for cFLIP<inf>S/L</inf> proteins was observed in luteal cells during pregnancy. The present findings revealed that cFLIP was at the highest level in CLs during pregnancy, and this may act as a dominant survival anti-apoptotic factor by inhibiting intracellular apoptosis signal transduction in luteal cells of CLs during pregnancy.

Development of the Timed Re-Insemination (TRI-synch) program re-inseminating 24 days after the initial service in dairy cows

For the timed re-insemination at the minimal interbreeding interval, cows were treated with a progesterone (P4 )-releasing intravaginal device from Days 13-15 to 21 post-insemination (Day 0 = estrus), followed by plasma P4 assay on Day 23 and then subjected to the Experiments 1 and 2. In Experiment 1, of 18 cows, 6 cows were determined as luteolysis with low (<1 ng/ml) plasma P4 concentrations on Day 23 and ovulated on Days 24 (3 cows), 25 (1 cow), and 26 (1 cow) except a cow affected by ovarian quiescence. In Experiment 2, all cows were treated with GnRH on Day 23. Cows with low (<1 ng/ml) plasma P4 concentrations on Day 23 were diagnosed as non-pregnant and subjected to the re-insemination in the morning of Day 24 irrespective of estrous signs. Of 36 cows, 15 cows were diagnosed as being non-pregnant on Day 23. Fourteen cows of the non-pregnant animals were re-inseminated in the morning of Day 24 irrespective of estrous signs and the pregnancy rate of re-insemination was 36%. The conception rates of initial and re-inseminations were 50% (18/36) and 36% (5/14), respectively. The overall pregnancy rate by adding the rates of initial and re-inseminations was 64% (23/36).

Genomic variant in porcine TNFRSF1A gene and its effects on TNF signaling pathway in vitro

Our initial genome-wide association study (GWAS) revealed the presence of single nucleotide polymorphisms (SNPs) related to immune traits in the tumor necrosis factor receptor superfamily member 1A (TNFRSF1A) gene, suggesting the association of this gene with immune function in pigs. To better understand the immune functions of the TNFRSF1A gene, SNPs within the TNFRSF1A gene were detected by sequencing. One SNP (c.1394C > T) in exon 6 of TNFRSF1A was identified, and association analysis in two pig populations was subsequently performed. The results showed that this SNP was significantly associated with CD4^-CD8^-CD3^-, CD4⁺CD8^-CD3⁺, and CD4⁺/CD8⁺ (P = 0.0038, P = 0.0007, and P = 0.0076, respectively). Based on quantitative real-time polymerase chain reaction (RT-qPCR), the TNFRSF1A mRNA was shown to be widely expressed in six different tissues. Finally, functional verification of the TNFRSF1A gene was performed in vitro to better understand its role. RNAi was used to generate a porcine PK15 cell line with a silenced TNFRSF1A gene, and a vector was also constructed to assess overexpression of TNFRSF1A. RT-qPCR was then used to detect changes in the expression levels of five critical genes. Our results indicated that TNFRSF1A activated the TNF signaling pathway and inhibited the NFκB signaling pathway in vitro. These findings provide evidence for an immune-related regulatory function for porcine TNFRSF1A.

Expression of matrix metalloproteinases to induce the expression of genes associated with apoptosis during corpus luteum development in bovine

Here we investigated the expressions of apoptosis-associated genes known to induce programed cell death through mRNA expressions of two matrix metalloproteinases (MMPs) that are involved in the degradation of collagen and basal membrane in luteal cells cultured in the treatment media. Our results show that the activity of MMP-2 gelatinase was higher in the CL2 and CL1 of luteal phase, was gradually decreased in the CH2 and CH3 of luteal phase. In particular, the expressions of P4-r and survival-associated genes (IGFr, PI3K, AKT, and mTOR) were strongly induced during CL3 stage, whereas the levels of these genes in corpus luteum (CL) were lower during CL2 and CL1 stages. In the cultured lutein cells analyzed, we found that as MMPs increase, genes related to apoptosis (20α-hydroxy steroid dehydrogenase and caspase-3) also increase. In other words, the results for P4-r and survival-related gene expression patterns in the luteal cells were contrary to the MMPs activation results. These results indicate that active MMPs are differentially expressed to induce the expression of genes associated with programed cell death from the degrading luteal cells. Therefore, our results suggest that the MMPs activation may lead to luteal cell development or death.

Differential effect of parity on rat mammary carcinogenesis after pre- or post-pubertal exposure to radiation

Radiation exposure during the peri-pubertal period is a proven risk factor for breast cancer, whereas parity is an established protective factor. The present study investigated whether parity imposes differential protective effects against radiation-induced rat mammary carcinoma depending on the age at exposure. Pre- and post-pubertal female rats, irradiated or left unirradiated, were mated and allowed to nurse until weaning or left unmated. Appearance of mammary tumors was monitored, and serum concentrations of estradiol and progesterone were measured following weaning. Carcinomas were evaluated by immunohistochemistry for estrogen receptor, progesterone receptor, and the cell proliferation marker Ki-67. Parity reduced the risk of carcinoma in unirradiated and pre-pubertally irradiated rats but not post-pubertally irradiated rats. Although radiation exposure increased serum progesterone level, parity after pre-pubertal exposure significantly decreased the elevated progesterone to a normal level, reflecting a protective effect. Moreover, parity significantly decreased the proportion of hormone receptor-positive carcinomas after pre-pubertal exposure. Parity was also related to the observed positive association between progesterone receptor and Ki-67 indices in cancer tissue, implying progesterone receptor-dependent cell proliferation. Thus, parity protects against radiation-induced rat mammary carcinogenesis depending on the age at exposure; the mechanisms may involve changes in hormone levels and cancer tissue.

The expression of autophagy-related proteins within the corpus luteum lifespan in pigs

Autophagy is a cellular process that involves the degradation of intracellular components. Recent studies suggested a role for autophagy in corpus luteum (CL) regression; however, a complete understanding of its contribution to CL function remains unclear. The present research using porcine CLs obtained from gilts at the early (CL1, n = 5), middle (CL2, n = 5), and late (CL3, n = 5) luteal phase of the estrous cycle aimed to assess the incidence of autophagy during CL development. The stages of collected CLs were verified through morphological analysis and intraluteal progesterone concentration. The presence of autophagosomes was assessed using transmission electron microscopy, and the expression of autophagic markers was examined at mRNA (BECN1 and Lamp1) and protein (Beclin 1, LC3-II, and Lamp 1) levels. Lamp 1 immunolocalization was also performed in luteal tissue. Double-membrane autophagosomes and autophagy-related proteins were found in all examined CLs. Interestingly, there was a greater expression of Beclin 1 (P = 0.005 and P = 0.025) and Lamp 1 (P = 0.009 and P = 0.032) protein in CL3 as compared with CL1 and CL2. In addition, the presence of autolysosomes in CL3 indicated advanced autophagy at that developmental stage. Overall, the occurrence of autophagy throughout CL development and regression suggests it has a role in the regulation of CL lifespan in pigs. In the early and mature CL, autophagy is proposed to promote luteal formation and function, whereas in the late CL, it may participate in luteal regression.

Role of luteal biosynthesis of prostaglandin F2α on function and structure of the corpus luteum during luteolysis in heifers

The role of endogenous prostaglandin F2α (PGF) in the induction of luteolysis by exogenous PGF was studied by simultaneous inhibition of endogenous PGF with flunixin meglumine (FM). Groups were controls (n = 8), PGF treated (n = 8), and FM + PGF treated (n = 9). Treatments were given 10 d postovulation at hours 0, 8, and 16. The protocol was based on (1) the assumption that luteolytic characteristics of exogenous PGF would be altered if the synthesis of endogenous PGF is simultaneously inhibited and (2) the reports that luteolysis involves a direct effect of uterine PGF on large luteal cells followed by an effect of the large cells on the small cells. At hour 48, progesterone concentration was greater in the controls (7.6 ± 0.8 ng/mL) than that in the FM + PGF group (3.0 ± 0.5 ng/mL) and lower in the PGF group (0.7 ± 0.3 ng/mL) than in the FM + PGF group (interaction, P < 0.0001). The effects of each of the 3 groups on percentage change in CL volume were similar to the effects on progesterone. At hour 48, the percentage of CL tissue with color-Doppler signals of blood flow was similar between the controls (56.2% ± 3.8%) and FM + PGF group (50.0% ± 6.4%) and lowest in the PGF group (15.6% ± 7.2%) (interaction, P < 0.0001). A resurgence in progesterone concentration began at hours 24 or 48 in 6 of 9 heifers in the FM + PGF group compared to 0 of 8 heifers in each of the other groups (P < 0.007). The progesterone resurgence in the FM + PGF group was associated with the maintenance of percentage of CL tissue with blood-flow signals. The experimental hypothesis that an inhibitor of endogenous PGF reduces the luteolytic response to exogenous PGF was supported.

The Dynamics of microRNA Transcriptome in Bovine Corpus Luteum during Its Formation, Function, and Regression

The formation, function, and subsequent regression of the ovarian corpus luteum (CL) are dynamic processes that enable ovary cyclical activity. Studies in whole ovary tissue have found microRNAs (miRNAs) to by critical for ovary function. However, relatively little is known about the role of miRNAs in the bovine CL. Utilizing small RNA next-generation sequencing we profiled miRNA transcriptome in bovine CL during the entire physiological estrous cycle, by sampling the CL on days: d 1–2, d 3–4, and d 5–7 (early CL, eCL), d 8–12 (mid CL, mCL), d 13–16 (late CL, lCL), and d > 18 (regressed CL, rCL). We characterized patterns of miRNAs abundance and identified 42 miRNAs that were consistent significantly different expressed (DE) in the eCL relative to their expression at each of the analyzed stages (mCL, lCL, and rCL). Out of these, bta-miR-210-3p, −2898, −96, −7-5p, −183-5p, −182, and −202 showed drastic up-regulation with a fold-change of ≥2.0 and adjusted P < 0.01 in the eCL, while bta-miR-146a was downregulated at lCL and rCL vs. the eCL. Another 24, 11, and 21 miRNAs were significantly DE only between individual comparisons, eCL vs. the mCL, lCL, and rCL, respectively. Irrespective of cycle stage two miRNAs, bta-miR-21-5p and bta-miR-143 were identified as the most abundant miRNAs species and show opposing expression abundance. Whilst bta-miR-21-5p peaked in number of reads in the eCL and was significantly downregulated in the mCL and lCL, bta-miR-143 reached its peak in the rCL and is significantly downregulated in the eCL. MiRNAs with significant DE in at least one cycle stage (CL class) were further grouped into eight distinct clusters by the self-organizing tree algorithm (SOTA). Half of the clusters contain miRNAs with low-expression, whilst the other half contain miRNAs with high-expression levels during eCL. Prediction analysis for significantly DE miRNAs resulted in target genes involved with CL formation, functionalization and CL regression. This study is the most comprehensive profiling of miRNA transcriptome in bovine CL covering the entire estrous cycle and provides a compact database for further functional validation and biomarker identification relevant for CL viability and fertility.

The effects of dexamethasone administered during pregnancy on the postpartum spiny mouse ovary

Excessive exposure to glucocorticoids can alter ovarian function by modulating oogenesis, folliculogenesis and steroidogenesis. The aim of the present study was to examine the effects of dexamethasone (DEX) administered during pregnancy on folliculogenesis and corpus luteum development in the postpartum spiny mouse ovary. DEX (125 μg kg^-1 body weight per day) was applied to pregnant spiny mouse from day 20 of gestation to parturition. The obtained ovaries were fixed and used for immunohistochemistry and TEM analysis. The expression of proteins related to apoptosis (caspase-3, Bax, Bcl-2) and autophagy (Beclin1, Lamp1) as well as PCNA and GR receptors were evaluated by western-blot. In comparison with DEX-treated group a higher percentage of TUNEL positive granulosa and luteal cells was observed in the control group. These data were consistent with changes in caspase-3 and Bax expression, which increased in the control and decreased after DEX exposure. In turn, the proliferation index and PCNA expression were higher in the DEX-treated group. Moreover, the higher level of Beclin1, Lamp1, anti-apoptotic Bcl-2 protein and GR was observed in the DEX-treated females than in the control group. Beclin1 and Lamp1 were strongly expressed in luteal cells which exhibited an autophagic ultrastructure. Surprisingly, DEX augmented the number of ovarian follicles and corpora lutea, which resulted in a significant increase in ovarian weight. These findings suggest that DEX exerts anti-apoptotic action on granulosa layer and stimulates follicular maturation. Moreover, DEX induces autophagy in luteal cells promoting cell survival rather than cell death, which can prolong the corpus luteum life span.

Gp91phox NADPH oxidase modulates litter size by regulating mucin1 in the uterus of mice

Active oxygen derived from gp91phox is critical for gestation. However, no reports have evaluated the relationship between reactive oxygen species (ROS) and the number of births in a given pregnancy. In this study, we examined the influence of ROS produced by gp91phox activity on the number of births using C57BL/6j (control) and gp91phox-knockout (gp91phox^-/-) mice. The number of births in gp91phox^-/- mice was found to be lower than that in control mice. We observed sequential increases in gp91phox, ROS, nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3), caspase-1, and interleukin-18 (IL-18), followed by increased expression of mucin1 (MUC1), in control mice. However, none of these markers were upregulated in gp91phox^-/- mice. In addition, in control mice administered IL-18 or MUC1 inhibitors, the number of births decreased to a number similar to that of gp91phox^-/- mice. These results suggest that ROS derived from gp91phox activity altered the inflammatory system and produced IL-18, which subsequently increased the expression of MUC1, thereby modulating fetal development.

ABBREVIATIONS

IL-1 β: interleukin-1β; IL-18: interleukin-18; NLRP3: nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3; IgA: immunoglobulin A; MUC1: mucin1.

Type-dependent differences in Fas expression and phagocytes distribution in rat corpora lutea during natural regression: an immunohistochemical evidence

Though Fas/Fas ligand (FasL) system-dependent apoptosis is considered to be the primary form of cell death in regressing corpus luteum (CL), the cellular identity and regulation of expression of the ligand and receptor molecules are not fully understood. Here, we focused on immunohistochemical determination of Fas expression during natural regression with comparison of three different types of rat CLs. Detected Fas was in good spatial association with cleaved caspase-3 and FasL proteins and with macrophages and neutrophils. In CLs of the cycle and pseudopregnancy, Fas-positive cell types included large and small luteal (steroidogenic) cells and capillary endothelial cells mainly, and blood-derived immune cells occasionally. Fas signals were abundant at multiple focal inflammatory-like sites. In contrast, Fas signals in CL of pregnancy did not localize in steroidogenic cells, but almost exclusively in endothelial cells and granulocytes. The signals scattered evenly throughout the CL tissue as phagocytes also did. In all CLs types, the numbers of Fas-expressing cells increased transiently after functional inactivation and at the early phase of structural regression. This observation revealed spatio-temporally regulated expression of Fas that was highly associated with apoptotic and phagocytotic systems and type-dependent differences in Fas expression and phagocytes dynamics in naturally regressing CL of rats.

Expressions of lipoprotein receptors and cholesterol efflux regulatory proteins during luteolysis in bovine corpus luteum

The corpus luteum (CL) synthesises and secretes progesterone (P4), which is essential for the establishment and maintenance of pregnancy in mammals. P4 is synthesised from cholesterol. Cholesterol is internalised by low-density lipoprotein receptor (LDLR) and/or scavenger receptor B1 (SR-BI), and is effluxed by ATP-binding cassette (ABC) transporter A1 (ABCA1) and G1 (ABCG1). To test the hypothesis that lipoprotein receptors and ABC transporters are involved in functional luteolysis, we examined the expression of LDLR, SR-BI, ABCA1 and ABCG1 in bovine CL during the luteal stages and after injection of prostaglandin (PG) F2α on Day 10 after ovulation. Expression of LDLR and SR-BI mRNA and protein was lower in the regressed luteal than late luteal stage. Injection of cows with a PGF2α did not affect LDLR mRNA and protein levels in the CL. Although expression of SR-BI mRNA did not change, SR-BI protein expression decreased 12 and 24 h after PGF2α injection. The overall findings of the present study suggest that the decreased expression of SR-BI induced by PGF2α is one of the factors responsible for the continuous decrease in P4 production during functional luteolysis.

Programmed necrosis - a new mechanism of steroidogenic luteal cell death and elimination during luteolysis in cows

Programmed necrosis (necroptosis) is an alternative form of programmed cell death that is regulated by receptor-interacting protein kinase (RIPK) 1 and 3-dependent, but is a caspase (CASP)-independent pathway. In the present study, to determine if necroptosis participates in bovine structural luteolysis, we investigated RIPK1 and RIPK3 expression throughout the estrous cycle, during prostaglandin F2α (PGF)-induced luteolysis in the bovine corpus luteum (CL), and in cultured luteal steroidogenic cells (LSCs) after treatment with selected luteolytic factors. In addition, effects of a RIPK1 inhibitor (necrostatin-1, Nec-1; 50 μM) on cell viability, progesterone secretion, apoptosis related factors and RIPKs expression, were evaluated. Expression of RIPK1 and RIPK3 increased in the CL tissue during both spontaneous and PGF-induced luteolysis (P < 0.05). In cultured LSCs, tumor necrosis factor α (TNF; 2.3 nM) in combination with interferon γ (IFNG; 2.5 nM) up-regulated RIPK1 mRNA and protein expression (P < 0.05). TNF + IFNG also up-regulated RIPK3 mRNA expression (P < 0.05), but not RIPK3 protein. Although Nec-1 prevented TNF + IFNG-induced cell death (P < 0.05), it did not affect CASP3 and CASP8 expression. Nec-1 decreased both RIPK1 and RIPK3 protein expression (P < 0.05). These findings suggest that RIPKs-dependent necroptosis is a potent mechanism responsible for bovine structural luteolysis induced by pro-inflammatory cytokines.

Novel concepts on the role of prostaglandins on luteal maintenance and maternal recognition and establishment of pregnancy in ruminants

In ruminants, the corpus luteum (CL) of early pregnancy is resistant to luteolysis. Prostaglandin (PG)E2 is considered a luteoprotective mediator. Early studies indicate that during maternal recognition of pregnancy (MRP) in ruminants, a factor(s) from the conceptus or gravid uterus reaches the ovary locally through the utero-ovarian plexus (UOP) and protects the CL from luteolysis. The local nature of the embryonic antiluteolytic or luteoprotective effect precludes any direct effect of a protein transported or acting between the gravid uterus and CL in ruminants. During MRP, interferon tau (IFNT) secreted by the trophoblast of the conceptus inhibits endometrial pulsatile release of PGF2α and increases endometrial PGE2. Our recent studies indicate that (1) luteal PG biosynthesis is selectively directed toward PGF2α at the time of luteolysis and toward PGE2 at the time of establishment of pregnancy (ESP); (2) the ability of the CL of early pregnancy to resist luteolysis is likely due to increased intraluteal biosynthesis and signaling of PGE2; and (3) endometrial PGE2 is transported from the uterus to the CL through the UOP vascular route during ESP in sheep. Intrauterine co-administration of IFNT and prostaglandin E2 synthase 1 (PGES-1) inhibitor reestablishes endometrial PGF2α pulses and regresses the CL. In contrast, intrauterine co-administration of IFNT and PGES-1 inhibitor along with intraovarian administration of PGE2 rescues the CL. Together, the accumulating information provides compelling evidence that PGE2 produced by the CL in response to endometrial PGE2 induced by pregnancy may counteract the luteolytic effect of PGF2α as an additional luteoprotective mechanism during MRP or ESP in ruminants. Targeting PGE2 biosynthesis and signaling selectively in the endometrium or CL may provide luteoprotective therapy to improve reproductive efficiency in ruminants.

Prolactin modulates luteal regression from the coeliac ganglion via the superior ovarian nerve in the late-pregnant rat

There is considerable evidence of the neuroendocrine control involved in luteal regression in the rat. In addition, circulating prolactin (PRL), which increases during the night before parturition, may gain access to the coeliac ganglion (CG), indirectly impacting the physiology of the ovary because of the known connection between the CG and the ovary via the superior ovarian nerve (SON). In this work we investigated in the CG–SON–ovary system and whether PRL added to the CG has an impact, indirectly via the SON, on luteal regression on Day 21 of pregnancy. The system was incubated without (control) or with PRL added to the CG. We measured the ovarian release of progesterone (P), oestradiol and prostaglandin F2 alpha (PGF2α) by radioimmunoassay, and nitrites (NO) by the Griess method. Luteal mRNA expression of 3β-hydroxysteroid dehydrogenase (3β-HSD), 20α-HSD, aromatase, inducible nitric oxide synthase (iNOS) and apoptosis regulatory factors was analysed by reverse transcription–polymerase chain reaction. P release, the expression of Bcl-2 and the Bcl-2 : Bax ratio was lower than control preparations, while the expression of 20α-HSD and the release of NO and PGF2α were higher in the experimental group. In conclusion, PRL acts at the CG and, by a neural pathway, modulates luteal function at the end of pregnancy.

Apoptosis-Related Factors in the Luteal Phase of the Domestic Cat and Their Involvement in the Persistence of Corpora Lutea in Lynx

The corpus luteum (CL) is a transient gland formed in the ovary after ovulation and is the major source of progesterone. In the Iberian and Eurasian lynx, CL physiologically persist after parturition and retain their capacity to produce progesterone, thus suppressing the ovarian activity. This unique reproductive characteristic has a big impact on the success of assisted reproduction techniques in the endangered Iberian lynx. The mechanisms behind CL persistence are not yet understood and require extensive studies on potential luteotropic and luteolytic factors in felids. Because the apoptosis system has been shown to be involved in structural regression of CL in many species, we aimed to investigate the capacity of perCL to undergo apoptosis. In addition, we performed initial studies on the apoptosis system in the luteal phase of the domestic cat. No previous research on this system has been made in this species. Our factors of interest included agents of the intrinsic apoptosis pathway, i.e., pro-survival B-cell CLL/lymphoma 2 (BCL2) and pro-apoptotic BCL2-associated X protein (BAX), the executioner caspase-3 (CASP3), as well as of the extrinsic pathway, i.e., pro-apoptotic receptor FAS, and tumor necrosis factor (TNF) and its receptors (pro-apoptotic TNFRSF1A and pro-survival TNFRSF1B). We analyzed the relative mRNA levels of these factors, as well as protein localization of CASP3 and TNF during stages of pregnancy and the non-pregnant luteal phase in CL of domestic cats. The same factors were investigated in freshly ovulated CL (frCL) and perCL of Iberian and Eurasian lynx, which were histologically analyzed. All factors were present in the CL tissue of both domestic cat and lynx throughout all analyzed stages. The presence of pro-apoptotic factors BAX, CASP3, FAS and TNFRSF1A in perCL of the Eurasian and Iberian lynx might indicate the potential sensitivity of perCL to apoptotic signals. The expression of pro-survival factors BCL2 and TNFRSF1B was significantly higher in perCL compared to frCL of studied Iberian lynx, suggesting the potential involvement of these factors in the structural integrity of perCL. In both Iberian lynx and pregnant and non-pregnant domestic cats, the expression of TNFRSF1A was significantly higher in forming CL compared to other stages, suggesting the conserved involvement of this factor in the tissue reorganization during formation of the feline CL. The mRNA levels of CASP3 and TNFRSF1B were highest during regression stages of domestic cat CL. The current study provides initial results on the possible involvement of the apoptosis system in the structure and function of the feline CL and in its physiological persistence.

Noradrenaline modulates the presence of gonadotropin-releasing hormone in ovary. The importance of its interrelation on the ovarian steroidogenesis and apoptosis on dioestrus II in rat

The aim of this work was to investigate if noradrenaline (NA), added in the coeliac ganglion -superior ovarian nerve- ovary system (CG-SON-O) and in ovary incubation, modifies the release of ovarian progesterone (P4), gonadotropin-releasing hormone (GnRH) and oestradiol (E2), and the expression of 3β-HSD and 20α-HSD and proapoptotic bax and antiapoptotic bcl-2 on dioestrus II in the rat. The CG-SON-O system and the ovary were removed and placed in one cuvette containing Krebs-Ringer solution (control groups), and NA was added to the ganglion compartment in the ex vivo system and in the ovary compartment in the ovary incubation (experimental groups). P4, GnRH and E2 were measured by RIA, and gene expression was measured by RT-PCR. In the ex-vivo system, the release of ovarian P4 and GnRH and the expression of 3β-HSD and bax decreased; E2 and bcl-2 increased, and the bax/bcl-2 ratio decreased. However, in the ovary incubation, P4, GnRH, the expression of 3β-HSD and bax increased; E2, the expression of 20α-HSD and bcl-2 decreased while the bax/bcl-2 ratio increased, thus favoring apoptosis. The peripheral nervous system protected the ovary from the apoptotic mechanisms while in the ovary incubation the effect was reverted. Our results indicate that NA regulates ovarian steroidogenesis and apoptosis by modulating GnRH release from the coeliac ganglion and ovary, being NA a possible generator of a GnRH-gonadotropins axis in the ovary. This work is expected to contribute with new evidence of the clinical importance of catecholamines and GnRH in therapy and prevention of ovarian pathologies.

Neuromodulation of the luteal regression: presence of progesterone receptors in coeliac ganglion

NEW FINDINGS

What is the central question of this study? The processes involved in luteal involution have not yet been clarified and, in general, have been studied only from a hormonal point of view. We investigated whether progesterone, from the coeliac ganglion through the superior ovarian nerve, is able to modify the luteal regression of late pregnancy in the rat. What is the main finding and its importance? We showed that the luteal regression might be reversed by the neural effect of progesterone and demonstrated the presence of its receptors in the coeliac ganglion. This suggests that the peripheral neural pathway, through neuron-hormone interaction, represents an additional mechanism to control luteal function in addition to the classical endocrine regulation. The corpus luteum (CL) is a transitory endocrine gland that produces progesterone (P). At the end of its useful life, it suffers a process of functional and structural regression until its complete disappearance from the ovary. To investigate whether P is able to regulate the process of luteal regression through the peripheral neural pathway, we used the coeliac ganglion (CG)-superior ovarian nerve-ovary system from rats on day 21 of pregnancy. We stimulated the CG with P and analysed the functional regression through ovarian P release measured by radioimmunoassay, expression by RT-PCR and activity of luteal 3β- and 20α-hydroxysteroid dehydrogenase (anabolic and catabolic P enzymes, respectively). The luteal structural regression was evaluated through a study of apoptosis measured by TUNEL assay and the expression of apoptotic factors, such as Bcl-2, Bax, Fas and Fas ligand (FasL) by RT-PCR. To explore whether the effects mediated by P on the CL may be associated with P receptors, their presence in the CG was investigated by immunohistochemistry. In the group stimulated with P in the CG, the ovarian P release and the 3β-hydroxysteroid dehydrogenase activity increased, whereas the expression and activity of 20α-hydroxysteroid dehydrogenase decreased. In addition, a decrease in the number of apoptotic nuclei and a decrease of the expression of FasL were observed. We demonstrated the presence of P receptors in the CG. Overall, our results suggest that the regression of the CL of late pregnancy may be reprogrammed through the peripheral neural pathway, and this effect might be mediated by P bound to its receptor in the CG.

The luteotrophic function of galectin-1 by binding to the glycans on vascular endothelial growth factor receptor-2 in bovine luteal cells

The corpus luteum (CL) is a temporary endocrine gland producing a large amount of progesterone, which is essential for the establishment and maintenance of pregnancy. Galectin-1 is a β-galactose-binding protein that can modify functions of membrane glycoproteins and is expressed in the CL of mice and women. However, the physiological role of galectin-1 in the CL is unclear. In the present study, we investigated the expression and localization of galectin-1 in the bovine CL and the effect of galectin-1 on cultured luteal steroidogenic cells (LSCs) with special reference to its binding to the glycans on vascular endothelial growth factor receptor-2 (VEGFR-2). Galectin-1 protein was highly expressed at the mid and late luteal stages in the membrane fraction of bovine CL tissue and was localized to the surface of LSCs in a carbohydrate-dependent manner. Galectin-1 increased the viability in cultured LSCs. However, the viability of LSCs was decreased by addition of β-lactose, a competitive carbohydrate inhibitor of galectin-1 binding activity. VEGFR-2 protein, like galectin-1, is also highly expressed in the mid CL, and it was modified by multi-antennary glycans, which can be recognized by galectin-1. An overlay assay using biotinylated galectin-1 revealed that galectin-1 directly binds to asparagine-linked glycans (N-glycans) on VEGFR-2. Enhancement of LSC viability by galectin-1 was suppressed by a selective inhibitor of VEGFR-2. The overall findings suggest that galectin-1 plays a role as a survival factor in the bovine CL, possibly by binding to N-glycans on VEGFR-2.

Expression of matrix metalloproteinases in bovine luteal cells induced by prostaglandin F2α, interferon γ and tumor necrosis factor α

We recently demonstrated that luteal cells flow out from the ovary via lymphatic vessels during luteolysis. However, the regulatory mechanisms of the outflow of luteal cells are not known. Matrix metalloproteinases (MMPs) can degrade the extracellular matrix and basal membrane, and tissue inhibitors of matrix metalloproteinases (TIMPs) inhibit the activity of MMPs. To test the hypothesis that MMP expression in luteal cells is regulated by luteolytic factors, we investigated the effects of prostaglandin F2α (PGF), interferon γ (IFNG) and tumor necrosis factor α (TNF) on the mRNA expression of MMPs and TIMPs in cultured luteal cells. Luteal cells obtained from the CL at the mid-luteal stage (days 8–12 after ovulation) were cultured with PGF (0.01, 0.1, 1 μM), IFNG (0.05, 0.5, 5 nM) and TNF (0.05, 0.5, 0.5 nM) alone or in combination for 24 h. PGF and IFNG significantly increased the expression of MMP-1 mRNA. In addition, 1 μM PGF in combination with 5 nM IFNG stimulated MMP-1 and MMP-9 mRNA expression significantly more than either treatment alone. In contrast, IFNG significantly decreased the level of MMP-14 mRNA. The mRNA expression of TIMP-1, which preferentially inhibits MMP-1, was suppressed by 5 nM INFG. One μM PGF and 5 nM IFNG suppressed TIMP-2 mRNA expression. These results suggest a new role of MMPs: luteal MMPs stimulated by PGF and IFNG break down the extracellular matrix surrounding luteal cells, which accelerates detachment from the CL during luteolysis, providing an essential prerequisite for outflow of luteal cells from the CL to lymphatic vessels.

Potential role of hCG in apoptosis of human luteinized granulosa cells

The corpus luteum (CL) forms after ovulation and acts as a temporary endocrine gland that produces progesterone (P4), a hormone that is essential for implantation and maintenance of pregnancy in mammals. In pregnant women, human chorionic gonadotropin (hCG) secreted by the conceptus prevents luteolysis. hCG also increases the survival of cultured human luteinized granulosa cells (hLGCs). To clarify the maintenance mechanism of the human CL, we investigated the effects of hCG and P4 receptor antagonists, onapristone (OP) and RU486, on the viability of hLGCs. With the patients’ consent, hLGCs were isolated from follicular aspirates for in vitro fertilization. The cells were cultured with hCG (0.1, 1, 10, 100 IU/ml), OP (10, 25, 50, 100 μM), RU486 (100 μM), P4 (1, 10, 25, 50 μM) or some combination of the four for 24 h. Cell viability was significantly increased by hCG (100 IU/ml) and significantly decreased by OP (100 μM) compared with the control. Cells treated with hCG and OP together were significantly less viable than the control and OP-treated cells. The combined treatment also significantly increased CASP3 activity and cleaved CASP3 protein expression. Furthermore, P4 addition reversed the reduction in cell viability caused by the combination of hCG and OP treatment. The overall findings suggest that hCG cooperates with P4 to increase survival of hLGCs and to induce apoptosis when P4 action supported by hCG is attenuated in the human CL.

The role of BH3-only proteins in apoptosis within the ovary

BH3-only proteins are pro-apoptotic members of the BCL2 family that play pivotal roles in embryonic development, tissue homeostasis and immunity by triggering cell death through the intrinsic apoptosis pathway. Recent in vitro and in vivo studies have demonstrated that BH3-only proteins are also essential mediators of apoptosis within the ovary and are responsible for the initiation of the cell death signalling cascade in a cell type and stimulus-specific fashion. This review gives a brief overview of the intrinsic apoptosis pathway and summarise the roles of individual BH3-only proteins in the promotion of apoptosis in embryonic germ cells, oocytes, follicular granulosa cells and luteal cells. The role of these proteins in activating apoptosis in response to developmental cues and cell stressors, such as exposure to chemotherapy, radiation and environmental toxicants, is described. Studies on the function of BH3-only proteins in the ovary are providing valuable insights into the regulation of oocyte number and quality, as well as ovarian endocrine function, which collectively influence the female reproductive lifespan and health.

Expression of factors associated with apoptosis in the porcine corpus luteum throughout the luteal phase of the estrous cycle and early pregnancy: their possible involvement in acquisition of luteolytic sensitivity

The studies on the acquisition of luteolytic sensitivity have been focused mainly on molecular changes induced in the luteal tissue after treatment with exogenous PGF2α or on physiological changes occurring during the estrous cycle. The comparison of changes leading to the acquisition of luteolytic sensitivity after Day 12 of the estrous cycle and corresponding days of pregnancy has not been investigated in the pig. The present study was undertaken to evaluate (1) apoptosis measured as the proportions of early apoptotic, late apoptotic, and viable cells; (2) expression of factors involved in the extrinsic (TNFA/TNFα, TNFRSF1A/TNFR1, TNFRSF1B/TNFR2, FAS/Fas, and FASLG/FasL) and intrinsic (CASP3/Casp3, TP53/p-53, BAX/Bax, and BCL2/Bcl-2) apoptotic pathways, with two components of the activating protein-1 complex, i.e., FOS/Fos and JUN/Jun and IFNG/IFNγ; and (3) concentrations of luteal and blood plasma progesterone (P4) throughout the luteal phase of the estrous cycle and early pregnancy. Corpora lutea (CL) were collected postmortem on Days 8, 10, 12, and 14 of the estrous cycle and the corresponding days of pregnancy. The luteal tissue was subjected to RNA and/or protein isolation and disaggregation of CL cells followed by flow cytometry analysis aimed to determine apoptotic changes. Luteal and blood plasma P4 concentrations decreased on Day 14 of the estrous cycle versus pregnancy (P < 0.05 and P < 0.001, respectively). A significant increase in the number of early apoptotic cells and a decrease in the number of viable cells were observed on Day 14 of the estrous cycle (P < 0.001 and P < 0.05, respectively). Increase (P < 0.05) of TNFA messenger RNA (mRNA) level coincided with that of IFNG on Day 12 of the estrous cycle but not on the corresponding day of pregnancy. The content of FAS mRNA and protein increased on Day 14 of the estrous cycle versus pregnancy (P < 0.05). The mRNA expression of CASP3, BCL-2 and BAX was unchanged in cyclic and pregnant CL, while level of TP53 increased (P < 0.05) on Day 12 of the estrous cycle versus Day 8. The level of FOS and JUN mRNA increased (P < 0.05) on Day 14 of the estrous cycle versus the remaining days. The level of FOS and JUN mRNA was significantly higher (P < 0.001 and P < 0.05, respectively) on Day 14 of the estrous cycle than that on the corresponding day of pregnancy. In summary, the simultaneous increase of TNFA and IFNG transcript in cyclic CL suggests the crucial role of both cytokines in sensitization of porcine CL to further luteolytic action of PGF2α. The upregulated expression of FAS, FOS, and JUN mRNA in the late luteal phase in cyclic CL can indicate their involvement in structural luteolysis. The increased viability of luteal cells and elevated P4 concentrations in pregnant CL confirm the protective role of luteal P4 against apoptosis.

Profiling of luteal transcriptome during prostaglandin F2-alpha treatment in buffalo cows: analysis of signaling pathways associated with luteolysis

In several species including the buffalo cow, prostaglandin (PG) F2α is the key molecule responsible for regression of corpus luteum (CL). Experiments were carried out to characterize gene expression changes in the CL tissue at various time points after administration of luteolytic dose of PGF2α in buffalo cows. Circulating progesterone levels decreased within 1 h of PGF2α treatment and evidence of apoptosis was demonstrable at 18 h post treatment. Microarray analysis indicated expression changes in several of immediate early genes and transcription factors within 3 h of treatment. Also, changes in expression of genes associated with cell to cell signaling, cytokine signaling, steroidogenesis, PG synthesis and apoptosis were observed. Analysis of various components of LH/CGR signaling in CL tissues indicated decreased LH/CGR protein expression, pCREB levels and PKA activity post PGF2α treatment. The novel finding of this study is the down regulation of CYP19A1 gene expression accompanied by decrease in expression of E2 receptors and circulating and intra luteal E2 post PGF2α treatment. Mining of microarray data revealed several differentially expressed E2 responsive genes. Since CYP19A1 gene expression is low in the bovine CL, mining of microarray data of PGF2α-treated macaques, the species with high luteal CYP19A1 expression, showed good correlation between differentially expressed E2 responsive genes between both the species. Taken together, the results of this study suggest that PGF2α interferes with luteotrophic signaling, impairs intra-luteal E2 levels and regulates various signaling pathways before the effects on structural luteolysis are manifest.

Luteal activity of pregnant rats with hypo-and hyperthyroidism

Background

Luteal activity is dependent on the interaction of various growth factors, cytokines and hormones, including the thyroid hormones, being that hypo- and hyperthyroidism alter the gestational period and are also a cause of miscarriage and stillbirth. Because of that, we evaluated the proliferation, apoptosis and expression of angiogenic factors and COX-2 in the corpus luteum of hypo- and hyperthyroid pregnant rats.

Methods

Seventy-two adult female rats were equally distributed into three groups: hypothyroid, hyperthyroid and control. Hypo- and hyperthyroidism were induced by the daily administration of propylthiouracil and L-thyroxine, respectively. The administration began five days before becoming pregnant and the animals were sacrificed at days 10, 14, and 19 of gestation. We performed an immunohistochemical analysis to evaluate the expression of CDC-47, VEGF, Flk-1 (VEGF receptor) and COX-2. Apoptosis was evaluated by the TUNEL assay. We assessed the gene expression of VEGF, Flk-1, caspase 3, COX-2 and PGF2α receptor using real time RT-PCR. The data were analyzed by SNK test.

Results

Hypothyroidism reduced COX-2 expression on day 10 and 19 (P < 0.05), endothelial/pericyte and luteal cell proliferation on day 10 and 14 (p < 0.05), apoptotic cell numbers on day 19 (p < 0.05) and the expression of Flk-1 and VEGF on day 14 and 19, respectively (p < 0.05). Hyperthyroidism increased the expression of COX-2 on day 19 (P < 0.05) and the proliferative activity of endothelial/pericytes cells on day 14 (p <0.05), as well as the expression of VEGF and Flk-1 on day 19 (P < 0.05).

Conclusions

Hypothyroidism reduces the proliferation, apoptosis and expression of angiogenic factors and COX-2in the corpus luteum of pregnant rats, contrary to what is observed in hyperthyroid animals, being this effect dependent of the gestational period.

Histological characteristics of the regression of corpora lutea in wistar hannover rats: the comparisons with sprague-dawley rats

We examined the ovaries of 44 Wistar Hannover (RccHan^TM:WIST) (WH) and 30 Sprague-Dawley (SD) rats at 32-weeks of age to determine whether the ovarian structure and formation/regression of the corpora lutea (CLs) differ between the two strains. The average ovary weight was higher in WH rats. The average number of all CLs, including currently formed and previously formed CLs, was higher in WH rats in all cycles; however, no appreciable difference was detected in the number of newly or currently formed CLs between the two strains. CLs regression characterized by degeneration and necrosis of luteal cells began to appear in diestrus in both strains; however, the distribution of degenerated/necrotic cells in CLs differed. Necrotic cells were scattered in SD rats but were focally observed in the center of the CL in WH rats. The reduction in size of previously formed CLs accompanied by regression started about 2 or more stages later in WH rats than in those of SD rats. In conclusion, the higher number of CLs in WH rats is considered to be due to slow CL regression compared with in SD rats.

Lymphatic involvement in the disappearance of steroidogenic cells from the corpus luteum during luteolysis

In mammals, the corpus luteum (CL) is an essential endocrine gland for the establishment and maintenance of pregnancy. If pregnancy is not established, the CL regresses and disappears rapidly from the ovary. A possible explanation for the rapid disappearance of the CL is that luteal cells are transported from the ovary via lymphatic vessels. Here, we report the presence of cells positive for 3β-hydroxysteroid dehydrogenase (3β-HSD), an enzyme involved in progesterone synthesis, in the lumen of lymphatic vessels at the regressing luteal stage and in the lymphatic fluid collected from the ovarian pedicle ipsilateral to the regressing CL. The 3β-HSD positive cells were alive and contained lipid droplets. The 3β-HSD positive cells in the lymphatic fluid were most abundant at days 22–24 after ovulation. These findings show that live steroidogenic cells are in the lymphatic vessels drained from the CL. The outflow of steroidogenic cells starts at the regressing luteal stage and continues after next ovulation. The overall findings suggest that the complete disappearance of the CL during luteolysis is involved in the outflow of luteal cells from the CL via ovarian lymphatic vessels.

Effect of prolactin acting on the coeliac ganglion via the superior ovarian nerve on ovarian function in the postpartum lactating and non-lactating rat

Whether prolactin (PRL) has a luteotrophic or luteolytic effect in the rat ovary depends on the nature of the corpora lutea present in the ovaries and the hormonal environment to which they are exposed. The aim was to investigate the effect of PRL acting on the coeliac ganglion (CG) on the function of the corpora lutea on day 4 postpartum under either lactating or non-lactating conditions, using the CG-superior ovarian nerve-ovary system. The ovarian release of progesterone (P), estradiol, PGF2α, and nitrites was assessed in the ovarian compartment at different incubation times. Luteal mRNA expression of 3β-HSD, 20α-HSD, aromatase, PGF2α receptor, iNOS, Bcl-2, Bax, Fas and FasL was analysed in the corpus luteum of pregnancy at the end of the experiments. Comparative analysis of control groups showed that the ovarian release of P, nitrites, and PGF2α, the expression of PGF2α receptor, and the Bcl-2/Bax ratio were lower in non-lactating rats, with increased release of estradiol, and higher expression of aromatase, Fas and FasL, demonstrating the higher luteal functionality in ovaries of lactating animals. PRL added to the CG compartment increased the ovarian release of P, estradiol, nitrites and PGF2α, and decreased the Bcl-2/Bax ratio in non-lactating rats; yet, with the exception of a reduction in the release of nitrites, such parameters were not modified in lactating animals. Together, these data suggest that the CG is able to respond to the effect of PRL and, via a neural pathway, fine-tune the physiology of the ovary under different hormonal conditions.

Roles of antioxidant enzymes in corpus luteum rescue from reactive oxygen species-induced oxidative stress

Progesterone produced by the corpus luteum (CL) regulates the synthesis of various endometrial proteins required for embryonic implantation and development. Compromised CL progesterone production is a potential risk factor for prenatal development. Reactive oxygen species (ROS) play diverse roles in mammalian reproductive biology. ROS-induced oxidative damage and subsequent adverse developmental outcomes constitute important issues in reproductive medicine. The CL is considered to be highly exposed to locally produced ROS due to its high blood vasculature and steroidogenic activity. ROS-induced apoptotic cell death is involved in the mechanisms of CL regression that occurs at the end of the non-fertile cycle. Luteal ROS production and propagation depend upon several regulating factors, including luteal antioxidants, steroid hormones and cytokines, and their crosstalk. However, it is unknown which of these factors have the greatest contribution to the maintenance of CL integrity and function during the oestrous/menstrual cycle. There is evidence to suggest that antioxidants play important roles in CL rescue from luteolysis when pregnancy ensues. As luteal phase defect impacts fertility by preventing implantation and early conceptus development in livestock and humans, this review attempts to address the importance of ROS-scavenging antioxidant enzymes in the control of mammalian CL function and integrity. The corpus luteum (CL) is a transient endocrine organ that develops after ovulation from the ovulated follicle during each reproductive cycle. The main function of the CL is the production and secretion of progesterone which is necessary for embryonic implantation and development. Compromised CL progesterone production is a potential risk factor for prenatal development and pregnancy outcomes. Reactive oxygen species (ROS), which are natural by-products of cellular respiration and metabolism, play diverse roles in mammalian reproductive biology. ROS-induced oxidative damage and subsequent development of adverse pregnancy outcomes constitute important issues in reproductive medicine. Before the end of the first trimester, a high rate of human and animal conceptions end in spontaneous abortion and most of these losses occur at the time of implantation in association with ROS-induced oxidative damage. Every cell in the body is normally able to defend itself against the oxidative damage caused by the ROS. The cellular antioxidant enzymes constitute the first line of defence against the toxic effects of ROS. The CL is considered to be highly exposed to locally produced ROS due to its high blood vasculature and metabolic activity. There is now evidence to suggest that cellular antioxidants play important roles in CL rescue from regression when pregnancy ensues. As defective CL function impacts fertility by preventing implantation and early conceptus development in livestock and humans, this review attempts to address the importance of antioxidant enzymes in the control of mammalian CL function and integrity.

Rapid accumulation of polymorphonuclear neutrophils in the Corpus luteum during prostaglandin F(2α)-induced luteolysis in the cow

Prostaglandin F_2α (PGF_2α) induces luteolysis within a few days in cows, and immune cells increase in number in the regressing corpus luteum (CL), implying that luteolysis is an inflammatory-like immune response. We investigated the rapid change in polymorphonuclear neutrophil (PMN) numbers in response to PGF_2α administration as the first cells recruited to inflammatory sites, together with mRNA of interleukin-8 (IL-8: neutrophil chemoattractant) and P-selectin (leukocyte adhesion molecule) in the bovine CL. CLs were collected by ovariectomy at various times after PGF_2α injection. The number of PMNs was increased at 5 min after PGF_2α administration, whereas IL-8 and P-selectin mRNA increased at 30 min and 2 h, respectively. PGF_2α directly stimulated P-selectin protein expression at 5–30 min in luteal endothelial cells (LECs). Moreover, PGF_2α enhanced PMN adhesion to LECs, and this enhancement by PGF_2α was inhibited by anti-P-selectin antibody, suggesting that P-selectin expression by PGF_2α is crucial in PMN migration. In conclusion, PGF_2α rapidly induces the accumulation of PMNs into the bovine CL at 5 min and enhances PMN adhesion via P-selectin expression in LECs. It is suggested that luteolytic cascade by PGF_2α may involve an acute inflammatory-like response due to rapidly infiltrated PMNs.