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In Brief: PI3K-AKT signaling activates steroidogenesis by inducing estradiol and progesterone production, while MEK-ERK1/2 signaling regulates steroidogenesis by inhibiting estradiol and inducing progesterone production in granulosa cells (GCs). Both pathways are essential for glycolytic and mitochondrial metabolism in these cells., Abstract: The PI3K-AKT and MEK-ERK1/2 signaling pathways are integral to fundamental cellular processes, such as proliferation, viability and differentiation. In GCs, these pathways are activated by follicle-stimulating hormone (FSH) and IGF1 through respective receptors. We investigated the comparative transcriptome changes induced by the AKT and ERK (ERK1/2) pathways using corresponding inhibitors in GCs. GCs isolated from antral follicles showed positive signals for phospho-AKT and phospho-ERK proteins. Treatment of cultured GCs with FSH and IGF1 induced phospho-AKT and phospho-ERK levels. Transcriptome analysis revealed 1436 genes regulated by AKT and 654 genes regulated by the ERK pathway. Among these, 94 genes were commonly downregulated and 11 genes were commonly upregulated in both datasets, while 110 genes were oppositely regulated. Bioinformatics analysis revealed that the inhibition of the PI3K-AKT and MEK-ERK pathways downregulates key reproductive processes and upstream molecules. Notably, AKT inhibition affected FSH, ESRRG and HIF1 pathways, while ERK inhibition impacted CG, FOS, TGFβ, EGR1 and LH pathways. Transcriptome data showed that genes related to estradiol production were inhibited by ERK and induced by the AKT pathway. This was verified by radioimmunoassays, and mRNA and protein analysis of CYP19A1 and STAR genes. In addition, transcriptome data suggested the downregulation of glucose metabolism in GCs. Using validation experiments, we confirm that both pathways are essential for glucose uptake, lactate production and mitochondrial activity in GCs. These data provide a resource for informing future research for analyzing various novel candidate genes regulated by the AKT and ERK pathways in GCs and other cell types.

The current study presents the analysis of stromal cells obtained from an hyperplastic left-ovary of a Holstein cow. Cultured hyperplastic stromal cells displayed a fibroblast-like morphology and ceased proliferation after the 8th passage. The non-cancerous nature of stromal cells was confirmed by in vitro cell proliferation and migration assays. Negligible amounts of E2 were detected in the spent media of cultured stromal cells, which suggests that stromal cells were non-estradiol synthesizing cells. As revealed in immunofluorescence and gene expression analysis, the hyperplastic stromal cells explicitly expressed vimentin in their cytoskeleton. Upon hematoxylin staining, a highly dense population of stromal cells was observed in the stromal tissue of the hyperplastic ovary. To explore genome-wide alterations, mRNA microarray analysis was performed using Affymetrix Bovine Gene 1.0ST Arrays compared to normal ovarian derived stromal cells. The microarray identified 1396 differentially expressed genes, of which 733 were up- and 663 down-regulated in hyperplastic stromal cells. Importantly, asporin (ASPN) and vascular cell adhesion molecule 1 (VCAM1) were among the highly up-regulated genes. Higher expression of ASPN was also confirmed by immunohistochemistry and RT-qPCR analysis. Ingenuity pathway analysis (IPA) identified about 98 significantly enriched (-log (p value ≥ 1.3) canonical pathways, importantly of which the "Sirutin Signaling Pathway" and "Mitochondrial Dysfunction" were highly activated while "Oxidative phosphorylation" was inhibited. Additionally, higher proportion of hyperplastic stromal cells in the S-phase of cell cycle, could be attributed to higher expression levels of cell proliferation genes such as CCND2 and CDK6., (© 2024. The Author(s).)

Fatty acids have been shown to modulate glucose metabolism in vitro and in vivo. However, there is still a need for substantial evidence and mechanistic understanding in many cell types whether both saturated and unsaturated fatty acids (SFAs and UFAs) pose a similar effect and, if not, what determines the net effect of fatty acid mixes on glucose metabolism. In the present study, we asked these questions by treating granulosa cells (GCs) with the most abundant non-esterified fatty acid species in bovine follicular fluid. Results revealed that oleic and alpha-linolenic acids (UFAs) significantly increased glucose consumption compared to palmitic and stearic acids (SFAs). A significant increase in lactate production, extracellular acidification rate, and decreased mitochondrial activity indicate glucose channeling through aerobic glycolysis in UFA treated GCs. We show that insulin independent glucose transporter GLUT10 is essential for UFA driven glucose consumption, and the induction of AKT and ERK signaling pathways necessary for GLUT10 expression. To mimic the physiological conditions, we co-treated GCs with mixes of SFAs and UFAs. Interestingly, co-treatments abolished the UFA induced glucose uptake and metabolism by inhibiting AKT and ERK phosphorylation and GLUT10 expression. These data suggest that the net effect of fatty acid induced glucose uptake in GCs is determined by SFAs under physiological conditions., (© 2024. The Author(s).)

Estradiol and progesterone are the primary sex steroids produced by the ovary. Upon luteinizing hormone surge, estradiol-producing granulosa cells convert into progesterone-producing cells and eventually become large luteal cells of the corpus luteum. Signaling pathways and transcription factors involved in the cessation of estradiol and simultaneous stimulation of progesterone production in granulosa cells are not clearly understood. Here, we decipher that phosphorylated ERK1/2 regulates granulosa cell steroidogenesis by inhibiting estradiol and inducing progesterone production. Down-regulation of transcription factor FOXL2 and up-regulation of SOX9 by ERK underpin its differential steroidogenic function. Interestingly, the incidence of SOX9 is largely uncovered in ovarian cells and is found to regulate FOXL2 along with CYP19A1 and STAR genes, encoding rate-limiting enzymes of steroidogenesis, in cultured granulosa cells. We propose that the novel ERK1/2-SOX9/FOXL2 axis in granulosa cells is a critical regulator of ovarian steroidogenesis and may be considered when addressing pathophysiologies associated with inappropriate steroid production and infertility in humans and animals., (© 2023 Baddela et al.)

Ovarian cycle is controlled by circulating levels of the steroid hormone 17-β-estradiol, which is predominantly synthesized by the granulosa cells (GCs) of ovarian follicles. Our earlier studies showed that unsaturated fatty acids (USFs) downregulate and saturated fatty acids (SFAs) upregulate estradiol production in GCs. However, it was unclear whether pituitary gonadotropins induce accumulation of free fatty acids (FFAs) in the follicular fluid since follicle-stimulating hormone induces and luteinizing hormone inhibits estradiol production in the mammalian ovary. Interestingly, we show here the gas chromatography analysis of follicular fluid revealed no differential accumulation of FFAs between pre- and post-luteinizing hormone surge follicles. We therefore wondered how estradiol production is regulated in the physiological context, as USFs and SFAs are mutually present in the follicular fluid. We thus performed in vitro primary GC cultures with palmitate, palmitoleate, stearate, oleate, linoleate, and alpha-linolenate, representing >80% of the FFA fraction in the follicular fluid, and analyzed 62 different cell culture conditions to understand the regulation of estradiol biosynthesis under diverse FFA combinations. Our analyses showed co-supplementation of SFAs with USFs rescued estradiol production by restoring gonadotropin receptors and aromatase, antagonizing the inhibitory effects of USFs. Furthermore, transcriptome data of oleic acid-treated GCs indicated USFs induce the ERK and Akt signaling pathways. We show SFAs inhibit USF-induced ERK1/2 and Akt activation, wherein ERK1/2 acts as a negative regulator of estradiol synthesis. We propose SFAs are vital components of the follicular fluid, without which gonadotropin signaling and the ovarian cycle would probably be shattered by USFs., Competing Interests: Conflicts of interest The authors declare no financial and nonfinancial competing/conflicting interests that could have appeared to influence the findings reported in the present article. All authors approved the article., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

A majority of common metabolic diseases can result in excessive lipolysis, leading to elevated levels of non-esterified fatty acids (NEFAs) in the body fluids. In females, increased NEFA levels in the follicular fluid markedly alter the functions of intrafollicular cells such as granulosa cells (GCs) and oocytes. Therefore, elevated levels of NEFAs have been suggested to be a significant player of subfertility in females of both human and economically important animal species such as cattle, buffalo, sheep, pig, chicken, and dog. However, the effects imposed by saturated and unsaturated fatty acids (SFAs and UFAs) on ovarian follicles are controversial. The present review emphasizes that SFAs induce apoptosis in granulosa and cumulus cells of ovarian follicles in different species. They further could adversely affect oocyte maturation and developmental competence. Many types of UFAs affect steroidogenesis and proliferation processes and could be detrimental for follicular cells, especially when at elevated concentrations. Interestingly, monounsaturated fatty acids (MUFAs) appear to contribute to the etiology of the polycystic ovarian syndrome (PCOS) as they were found to induce the transcription and translation of the androgenic transcription factor SOX9 while downregulating its estrogenic counterpart FOXL2 in GCs. Overall, this review presents our revised understanding of the effects of different fatty acids on the female reproductive success, which may allow other researchers and clinicians to investigate the mechanisms for treating metabolic stress-induced female infertility.

Hypoxia-inducible factor 1 (HIF1) is a heterodimeric transcription factor, consisting of a constitutively expressed β-subunit (HIF1B) and a regulated α-subunit (HIF1A). In the present study, we analyzed the HIF1 driven transcriptional activity in bovine granulosa cells (GC). Treatment of GC with FSH (follicle stimulating hormone) and IGF1 (insulin-like growth factor 1) resulted in the upregulation of HIF1A mRNA expression under normoxia. Immunohistochemistry of bovine ovarian sections showed distinct staining of HIF1A in the GC layer of different staged ovarian follicles. Suppression of HIF1 using echinomycin and gene knockdown procedures revealed that HIF1 transcriptionally regulates the genes associated with steroidogenesis (STAR, HSD3B and CYP19A1) and proliferation (CCND2 and PCNA) of GC. Further, our data suggest that CYP19A1, the key gene of estradiol production, is one of the plausible downstream targets of HIF1 in bovine GC as shown by gene expression, radioimmunoassay, and chromatin precipitation analysis. Based on these results, we propose that HIF1 driven transcriptional activity plays a crucial role in GC functionality, especially steroidogenesis and proliferation in developing bovine ovarian follicles.

Here we assessed the effects of dietary essential fatty acids on the developmental competence of oocytes in cows and on the functionality of follicular granulosa cells (GC). Lactating German Holstein cows were supplemented from week 9 ante partum (ap) until week 8 post-partum (pp) in four dietary groups designed as (i) control (CTRL: coconut oil), (ii) essential fatty acid (EFA: linseed and safflower oil), (iii) conjugated linoleic acid (CLA: Lutalin®), and (iv) EFA+CLA (mixture of linseed oil, safflower oil and Lutalin®). EFA, CLA or EFA+CLA supplementation did not improve in vitro embryo production. However, higher proportions of α-linolenic acid (ALA) and cis-9, trans-11 CLA were observed in the follicular fluid suggesting the exposure of GC to relatively high levels of ALA and cis-9, trans-11 CLA. Consequently, we tested different concentrations of ALA and cis-9, trans-11 CLA in a bovine GC culture model for their effects on steroid production, marker gene expression and viability. Both fatty acids upregulated CD36 and downregulated the expression of FOXL2 , while ALA significantly increased SOX 9 transcript levels. Both ALA and cis-9, trans-11 CLA reduced the CCND2 expression and cis-9, trans-11 CLA induced apoptosis. ALA and cis-9, trans-11 CLA significantly down-regulated the expression of STAR, CYP19A1, FSHR, LHCGR and decreased the 17β-Estradiol (E2) and progesterone (P4) production. In conclusion, dietary lipids did not improve in vitro embryo production, while ALA and cis-9, trans-11 CLA affected the morphology and functionality of GC. This could suggestively lead to compromised follicle development and ovarian cyclicity in dairy cows., (Copyright © 2020 Sharma, Baddela, Roettgen, Vernunft, Viergutz, Dannenberger, Hammon, Schoen and Vanselow.)

High-yielding dairy cows postpartum face the challenge of negative energy balance leading to elevated free fatty acids levels in the serum and follicular fluid thus affecting the ovarian function. Here, we investigated effects of physiological concentrations of palmitic acid (PA), stearic acid (SA) and oleic acid (OA) on the viability, steroid production and gene expression in a bovine granulosa cell (GC) culture model. Treatment with individual and combined fatty acids increased the CD36 gene expression, while no significant apoptotic effects were observed. Both PA and SA significantly upregulated the expression of FSHR, LHCGR, CYP19A1, HSD3B1, CCND2 and increased 17β-estradiol (E2) production, while OA downregulated the expression of these genes and reduced E2. Interestingly, STAR was equally downregulated by all fatty acids and combination treatment. E2 was significantly reduced after combination treatment. To validate the effects of OA, in vivo growing dominant follicles (10-19 mm) were injected with bovine serum albumin (BSA) with/without conjugated OA. The follicular fluid was recovered 48 h post injection. As in our in vitro model, OA significantly reduced intrafollicular E2 concentrations. In addition, expression of CD36 was significantly up- and that of CYP19A1 and STAR significantly downregulated in antral GC recovered from aspirated follicles. The ovulation rates of OA-injected follicles tended to be reduced. Our results indicate that elevated free fatty acid concentrations specifically target functional key genes in GC both in vitro and in vivo. Suggestively, this could be a possible mechanism through which elevated free fatty acids affect folliculogenesis in dairy cows postpartum.

Genome wide mRNA expression analysis of small and large luteal cells, isolated from the mature staged corpora lutea (CL), was not performed in any species. In the current study, we have isolated bovine small and large luteal cells from mid-cycle (day 10-11) animals and characterized their transcriptomes using "GeneChip™ Bovine Gene 1.0 ST Arrays". A total of 1276 genes were identified to be differentially expressed between small and large luteal cells. Data evaluation revealed that novel functions, extracellular matrix synthesis and immune cell recruitment, were enriched in small luteal cells. On contrary, functions regarding the regulation of folliculogenesis, luteal regression, fatty acid and branched chain amino acid metabolism were differentially enriched in large luteal cells. Overall, the current data offer a first and detailed insight into the functional roles of small and large luteal cells in the mature bovine corpus luteum., (Copyright © 2018 Elsevier B.V. All rights reserved.)

During follicle maturation, oxygen levels continuously decrease in the follicular fluid and reach lowest levels in the preovulatory follicle. The current study was designed to comprehensively understand effects of low oxygen levels on bovine granulosa cells (GC) using our established estrogen active GC culture model. As evident from flow cytometry analysis the viability of GC was not found to be affected at severely low oxygen condition (1% O 2 ) compared to normal (atmospheric) oxygen condition (21% O 2 ). Estimations of hormone concentrations using competitive radioimmunoassay revealed that the production of estradiol and progesterone was significantly reduced at low oxygen condition. To understand the genome-wide changes of gene expression, mRNA microarray analysis was performed using Affymetrix's Bovine Gene 1.0 ST Arrays. This resulted in the identification of 1104 differentially regulated genes of which 505 were up- and 599 down-regulated under low oxygen conditions. Pathway analysis using Ingenuity pathway analyzer (IPA) identified 36 significantly affected ( p < 0.05) canonical pathways. Importantly, pathways like "Estrogen-mediated S-phase Entry" and "Cyclins and Cell Cycle Regulation" were found to be greatly down-regulated at low oxygen levels. This was experimentally validated using flow cytometry based cell cycle analysis. Up-regulation of critical genes associated with angiogenesis, inflammation, and glucose metabolism, and down-regulation of FSH signaling, steroidogenesis and cell proliferation indicated that low oxygen levels induced early luteinization associated changes in granulosa cells. Identification of unmethylated CpG sites in the CYP19A1 promoter region suggests that granulosa cells were not completely transformed into luteal cells under the present low oxygen in vitro condition. In addition, the comparison with earlier published in vivo microarray data indicated that 1107 genes showed a similar expression pattern in granulosa cells at low oxygen levels ( in vitro ) as found in preovulatory follicles after the LH surge ( in vivo ). Overall, our findings demonstrate for the first time that low oxygen levels in preovulatory follicles may play an important role in supporting early events of luteinization in granulosa cells.

Transcriptome profiling of FACS purified small luteal cells (SLC) and large luteal cells (LLC), isolated from mid-cycle corpora lutea (day 10-11), was performed using Affymetrix GeneChip Bovine Gene 1.0 ST Arrays. Gene expression was recorded using an Affymetrix gene chip scanner 3000. The corresponding expression array intensity (.CEL) files were deposited in the Gene Expression Omnibus (GSE106641). The subsequent expression analyses of CEL files were carried out for identifying important transcripts and their functions associated with SLC and LLC. These data have been comprehensively evaluated and interpreted in the companion article, "Global gene expression analysis indicates that small luteal cells are involved in extracellular matrix modulation and immune cell recruitment in the bovine corpus luteum" [1].

Estrus or sexual receptivity determination is utmost important for efficient breeding programs for female buffaloes. Prominent estrus behavioral symptoms are the result of several molecular and neuroendocrine events involving the ovary and the brain. Expression of estrus behavior is poor in buffaloes during the summer season. Hence, the discovery of biomarkers specific to the estrus stage or its related ovarian events, like the presence of dominant ovarian follicle, is helpful for developing an easy estrus determination method. MicroRNA are small non-coding RNA with a potential to be biomarkers. Therefore, the present study targeted to investigate the potential of estrogen responsive miRNAs (miR-24, miR-200c, miR-16, miR-191, miR-223 and miR-203) as estrus biomarkers in buffalo saliva, a non-invasive fluid representing animals' pathophysiology. There was a significant (P < 0.05) increase in the salivary presence of the miR-16, miR-191 and miR-223 at 6th and 18th-19th days than the 0 day (estrus), 10th day and the following consecutive estrus day. These observations may indicate an association between the representative lower presence of these miRNA in saliva and the presence of dominant ovarian follicles. To test this association, pathway analysis, target gene identification, functional annotation and protein-protein interaction networks (PPI) were performed for miR-16, miR-191 and miR-223 by different bioinformatics tools. Interestingly, the top pathways (fatty acid biosynthesis and oocyte meiosis), target genes (FGF, BDNF and IGF1) and PPI hub genes (KRAS, BCL2 and IGF1) of these miRNAs were found essential for ovarian follicular dominance. In conclusion, the miR-16, miR-191 and miR-223 may not be the perfect estrus stage-specific biomarkers. However, their lower presence in saliva at estrus and 9th-10th day of estrous cycles, when the ovary usually has a dominant follicle in buffaloes, may intuitively indicate the follicular dominance. Further studies are needed to prove this association in a large population.

The developmental reorganization of ovarian follicular granulosa cells (GC) during follicular maturation, ovulation, and luteinization require a well-controlled regulation of dynamic gene expression profiles. Recently, microRNAs (miRNAs) were found to be key players of ovarian follicular dynamics. The current study aimed to understand the miRNA regulatory role in follicular-luteal transition by characterizing the miRNA profile through miRNA-seq at different follicular (small, medium, and large) and luteal (early, mid, and late) stages in Indian water buffaloes, mono-ovulatory animals like humans. A total of 517 miRNAs were identified in follicular granulosa cells (GC) and corpus luteum (CL) together. Among them, 2 unique and 40 novel miRNAs were in GC; 15 unique and 45 novel miRNAs were in CL. Among the remaining 415 annotated common miRNAs between GC and CL, 43 have showed significant (p < 0.05) differential expression between GC and CL. Particularly, 39 and 4 miRNAs showed higher expression in CL and GC, respectively, with respect to each other. Genome mapping analysis revealed that 71.7% of differential miRNAs having higher expression in CL compared to GC, and 93% of the unique miRNAs in CL were mapped to a short chromosomal region of 0.7 Mb (67.4 to 68.1 Mb) on chromosome 21 of cows which is syntenic to the buffalo chromosome 20. Clustering of all these miRNAs at this locus suggests it as a chromosomal hotspot for miRNAs involved in follicular-luteal transition, especially for CL physiological functions.

Estrus detection is a major problem in buffalo husbandry because of inconsistent expression of estrous signs at different seasons, and a high prevalence of the silent heat and postpartum anestrus in this species. Around 50% of the estrus events in buffaloes are currently undetected in the field conditions, resulting in a huge economic loss. Although the cervicovaginal fluid fern patterns confirm the estrus for a breeding decision, the fluid discharge is absent during the silent-heat condition. Therefore, the present study focused on the crystallization patterns of the saliva as an alternative method for estrus detection in buffaloes. Saliva is a body fluid available regularly, and its ferning ability before ovulation was established in women. In this study, eight female nonpregnant Murrah buffaloes (Bubalus bubalis) were considered during two experimental periods of 3 months each. One period was in summer with five animals, and another period was in rainy season with three animals. Estrus was determined by the estrus symptoms, ovarian ultrasonography, and salivary estradiol (E2) to progesterone (P4) ratio. A total of 450 saliva samples were collected from these animals on the daily basis. The salivary smear was prepared with 20 μL of the cell-free saliva on a clean glass slide, and its microscopic images were captured at a magnification of × 200. The images were used for fractal analysis as the salivary crystallization or fern patterns follow the fractal geometry. Saliva at estrus showed a typical symmetrical fern-like crystallization patterns with significantly (P < 0.05) lower fractal dimension values. Salivary estradiol levels and E2/P4 ratio were significantly (P < 0.05) higher at the estrus stage than those at the diestrus stage. An average period of an estrous cycle was 21.7 ± 2.7 days (n = 18 estrous cycles) in buffaloes on the basis of distinct salivary crystallization patterns. The proportion of estrus detection by the salivary fern patterns was very significantly (P < 0.01) higher (0.84) than the proportion of estrus detection (0.5) in the field conditions. Altogether, salivary fern patterns along with the current methods can help reduce estrus detection problem in buffaloes., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Milk is a natural nutraceutical produced by mammals. The nanovesicles of milk play a role in horizontal gene transfer and confer health-benefits to milk consumers. These nanovesicles contain miRNA, mRNA, and proteins which mediate the intercellular communication. In this work, we isolated and characterized the buffalo milk-derived nanovesicles by dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), scanning electron microscopy (SEM), Western probing, and Fourier transform infrared (FTIR) spectroscopy. The DLS data suggested a bimodal size distribution with one mode near 50 nm and the other around 200 nm for the nanovesicles. The NTA and SEM data also supported the size of nanovesicles within a range of 50-200 nm. The FTIR measurements of nanovesicles identified some prominent absorption bands attributable to the proteins (1300-1700 cm(-1), amide A and amide B bands), lipids (2800-3100 cm(-1)), polysaccharides, and nucleic acids (900-1200 cm(-1)). The comparative expression profiles of immune miRNA signatures (miR-15b, miR-21, miR-27b, miR-125b, miR-155, and miR-500) in nanovesicles isolated from milk, serum, and urine revealed that these miRNAs are present abundantly (P < 0.05) in milk-derived nanovesicles. Milk miRNAs (miR-21 and 500) that were also found stable under different household storage conditions indicated that these could be biologically available to milk consumers. Overall, nanovesicles are a new class of bioactive compounds from buffalo milk with high proportion of stable immune miRNAs compared to urine and plasma of same animals.

Salivary RNA-based biomarkers are not available for any physiological condition in farm animals. Hence, an objective of this study was to perform salivary transcript analysis in buffaloes. Saliva, after removal of the cells and particulate matter, was directly used for RT-PCR without RNA isolation. Direct saliva transcript analysis (DSTA) showed a suggestively significant higher expression of the Heat shock protein 70 (HSP70) and Toll-like receptor 4 (TLR4) at oestrus than the diestrous period in buffaloes by a non-parametric Mann-Whitney U test. Therefore, DSTA without RNA isolation is an easy method to identify salivary RNA markers for oestrus detection in buffaloes.

Precise regulation of cell type-specific gene expression profiles precedes the profound morphological reorganization of somatic cell layers during folliculogenesis, ovulation and luteinization. Cell culture models are essential to the study of corresponding molecular mechanisms of gene regulation. In a recent study, it was shown that an increased cell plating density can largely change gene expression profiles of cultured bovine granulosa cells. In our present study, we comparatively analyzed cell plating density effects on cultured bovine and buffalo granulosa cells. Cells were isolated from small- to medium-sized follicles (2-6 mm) and cultured under serum-free conditions at different plating densities. The abundance of selected marker transcripts and associated miRNA candidates was determined by quantitative real-time RT-PCR. We found in both species that the abundance of CYP19A1, CCNE1 and PCNA transcripts was remarkably lower at a high plating density, whereas VNN2 and RGS2 transcripts significantly increased. In contrast, putative regulators of CYP19A1, miR-378, miR-106a and let-7f were significantly higher in both species or only in buffalo, respectively. Also miR-15a, a regulator of CCNE1, was upregulated in both species. Thus, increased plating density induced similar changes of mRNA and miRNA expression in granulosa cells from buffalo and cattle. From these data, we conclude that specific miRNA species might be involved in the observed density-induced gene regulation.

Background: Bovine granulosa cell culture models are important to understand molecular mechanisms of ovarian function. Folliculogenesis and luteinization are associated with increasing density of cells and local hypoxic conditions. The current study identified two reliable housekeeping genes useful for gene normalization in granulosa cells under different in vitro conditions., Methods: During the current experiments cells were subjected to different biological and physical stimuli, follicle stimulating hormone, different initial cell plating density and hypoxia. Transcript abundance of seven housekeeping genes was quantified by real-time RT-PCR with co-amplification of the respective external standard., Results: Three of the genes, GAPDH, HMBS, and HPRT1 were found to be regulated by initial cell plating density, five of them, GAPDH, HMBS, HPRT1, RPLP0 and RPS18 under hypoxic conditions, but none of them after FSH stimulation. In detail, GAPDH was up regulated, but HPRT1 and HMBS were down regulated at high density and under hypoxia. Expression of RPLP0 and RPS18 was inconsistent, but was significantly down-regulated in particular at high cell density combined with hypoxia. In contrast, TBP and B2M genes were neither regulated under different plating density conditions nor by hypoxia as they showed similar expression levels under all conditions analyzed., Conclusions: The present data indicate that TBP and B2M are appropriate housekeeping genes for normalization of transcript abundance measured by real-time RT-PCR in granulosa cells subjected to different plating densities, oxygen concentrations and FSH stimulation.