WNT2在绵羊卵泡颗粒细胞的表达及功能研究

旨在探究WNT2在绵羊卵泡颗粒细胞（GCs）中的表达及功能。本研究选取4~6月龄健康母羊20只,采集双侧卵巢,免疫组化技术检测WNT2蛋白在卵泡中的表达定位;qRT-PCR及Western blot技术检测其在不同发育阶段卵泡颗粒细胞中的表达差异;siRNA沉默GCs中的 Wnt2基因后,qRT-PCR技术检测Wnt2基因及参与经典WNT信号通路关键基因CTNNB1的相对表达量,并测定GCs凋亡情况。结果表明：1）WNT2蛋白在绵羊卵泡内膜细胞、颗粒细胞以及卵丘细胞内均有表达。2）qRT-PCR及Western blot结果基本一致,均表明Wnt2 mRNA及蛋白在不同发育阶段卵泡颗粒细胞表达差异显著（P<0.05）,且在大卵泡颗粒细胞内表达量显著高于中卵泡颗粒细胞（P<0.05）,中卵泡颗粒细胞内表达量显著高于小卵泡颗粒细胞（P<0.05）。3）基因沉默后,沉默组Wnt2和CTNNB1的表达量均显著低于无义序列siRNA组（NC组）以及空白对照组（P<0.05）,而Wnt2基因沉默组细胞凋亡率显著高于其他两组（P<0.05）。综上表明,WNT2是通过WNT2/CTNNB1信号通路促进绵羊卵泡颗粒细胞生物学功能的。     

Hematologic and biochemical reference intervals for specific pathogen free 6-week-old Hampshire-Yorkshire crossbred pigs

Background

Heifers not used as breeding stock are often implanted with steroids to increase growth efficiency thereby altering hormone profiles and potentially changing the environment in which ovarian follicles develop. Because bovine granulosa cell culture is a commonly used technique and often bovine ovaries are collected from abattoirs with no record of implant status, the objective of this study was to determine if the presence of an implant during bovine granulosa cell development impacts follicle stimulating hormone-regulated steroidogenic enzyme expression. Paired ovaries were collected from 16 feedlot heifers subjected to 1 of 3 treatments: non-implanted (n?=?5), Revalor 200 for 28 d (n?=?5), or Revalor 200 for 84 d (n?=?6). Small follicle (1 to 5 mm) granulosa cells were isolated from each pair and incubated with phosphate buffered saline (n?=?16) or 100 ng/mL follicle stimulating hormone (n?=?16) for 24 h.

Results

Granulosa cells of implanted heifers treated with follicle stimulating hormone produced medium concentrations of progesterone similar (P?=?0.22) to non-implanted heifers, while medium estradiol concentrations were increased (P?<?0.10) at 28 and 84 d compared to non-implanted heifers indicating efficacy of treatment. Additionally, real-time PCR analysis in response to follicle stimulating hormone treatment demonstrated a decrease in steroidogenic acute regulatory protein (P?=?0.05) mRNA expression in heifers implanted for 84 d and an increase in P450 side chain cleavage mRNA in granulosa cells of heifers implanted for 28 (P?<?0.10) or 84 d (P?<?0.05) compared to non-implanted females. However, no difference in expression of 3-beta-hydroxysteroid dehydrogenase (P?=?0.57) and aromatase (P?=?0.23) were demonstrated in implanted or non-implanted heifers.

Conclusions

These results indicate follicles which develop in the presence of high concentrations of androgenic and estrogenic steroids via an implant tend to demonstrate an altered capacity to respond to follicle stimulating hormone stimulation. Thus, efforts should be made to avoid the use of implanted heifers to study steroidogenesis in small follicle granulosa cell culture systems.     

Regulation of secondary follicle growth by theca cells and insulin-like growth factor 1

Ovaries contain follicles at various stages of development, including primordial, primary, secondary, antral and Graafian follicles. Although the growth of these follicles is controlled to maintain regular ovulation, the mechanism through which this occurs remains unclear. In our study, we found that the growth rate of cultured secondary follicles separated from mice ovaries differed between follicles. After 4 days of culture, the size of some secondary follicles was markedly increased, while that of others had either slightly increased, remained unchanged or shrunk. We compared the expression levels of growth factors between these secondary follicles and found that the growth rate of cultured secondary follicles correlated with the expression level of insulin-like growth factor 1 (Igf1) mRNA. Igf1 mRNA expression level in secondary follicles containing theca cells was higher than that in secondary follicles without theca cells, and the granulosa cell proliferation around follicles containing theca cells was increased. Furthermore, an IGF1 inhibitor also inhibited the granulosa cell proliferation, and administration of IGF1 to secondary follicles without growth promoted granulosa cell proliferation. These results indicated that the theca cells of secondary follicles induced the expression of IGF1 and promoted the follicle growth.     

Bone morphogenetic protein 4 (BMP‐4) and BMP‐7 induce vascular endothelial growth factor expression in bovine granulosa cells

Bone morphogenetic protein‐4 (BMP‐4) and BMP‐7, theca cell‐derived growth factors, directly affect the granulosa cell function. The aim of this study was to examine the involvement of BMP‐4 or BMP‐7 in vascular endothelial growth factor (VEGF) expression in bovine granulosa cells. Granulosa cells were collected from small follicles (4–6 mm) and seeded at a density of 2–5 × 10⁵ cells per well in Dulbecco's modified Eagle's medium (DMEM)/F12 medium with BMP‐4 or BMP‐7. The expression of VEGF messenger RNA and protein was the maximum when 1.0 ng/mL of BMP‐4 was added to the culture medium. On the other hand, 10 ng/mL of BMP‐7 significantly increased the expression of the VEGF gene and protein. In addition, BMP‐4 stimulated the expression of Smad1 and Smad5 genes in granulosa cells, whereas BMP‐7 stimulated the expression of Smad5 gene. These results suggested that BMP‐4 and BMP‐7 may be associated with VEGF expression via several specific Smads in bovine granulosa cells: BMP‐4 via Smad1/Smad5 and BMP‐7 via Smad5. In conclusion, theca cell‐derived BMP‐4 and BMP‐7 might contribute to follicular vasculature and development by inducing VEGF expression in granulosa cells.     

The endothelial nitric oxide synthase/nitric oxide system is involved in the defective quality of bovine oocytes from low mid-antral follicle count ovaries

In a previous survey concerning cows of reproductive age, we demonstrated that oocytes isolated from ovaries with <10 medium antral follicles of 2 to 6 mm in diameter (low ovaries; Lo) show less developmental competence than oocytes collected from ovaries with >10 medium antral follicles (high ovaries; Hi). The aim of the present study was to evaluate whether a defective endothelial nitric oxide synthase/nitric oxide (eNOS/NO) system and vasculature in healthy medium antral follicles is likely to reduce oocyte competence from Lo ovaries. Thus, experiments were conducted to 1) immunolocalize eNOS protein during folliculogenesis; 2) quantify eNOS protein/vasculature in the follicle wall; and 3) verify if NO donor, S-nitroso acetyl penicillamine (SNAP) administration during in vitro maturation affects developmental competence of oocytes isolated from Lo ovaries. Endothelial nitric oxide synthase protein was detected in granulosa and theca cells, as well as in blood vessels from primordial to antral follicles. Quantitative analysis indicated that in medium antral follicles from Lo ovaries, eNOS protein expression and vasculature were reduced (P < 0.05). The addition of SNAP improved blastocyst and hatching rates of oocytes from Lo ovaries, promoting a percentage similar to oocytes from Hi ovaries, and reduced the percentage of apoptotic nuclei in in vitro-produced blastocysts (P < 0.05). Results from our study suggest that in bovine ovaries with small mid antral follicle number, a defective eNOS/NO system is related to a reduced follicle vasculature and may affect oocyte quality, thus inducing a premature decline of fertility.     

The Expression of FSH Receptor (FSHR) in the Neonatal Porcine Ovary and its Regulation by Flutamide

This study was designed to reveal the FSHR mRNA and protein expression in the neonatal porcine ovary and to determine whether maternal administration of antiandrogen flutamide may affect FSHR expression in the ovary of newborn piglets using real‐time PCR, immunohistochemistry and Western blot analysis. Pregnant sows were injected with flutamide at a dose of 50 mg/kg body weight, given five times, every second day, starting at day 20 post‐coitum (p.c.) or day 80 p.c., and ovaries were obtained from neonatal pigs. The FSHR mRNA expression was significantly decreased after flutamide administration. Furthermore, higher down‐regulation was observed following exposure to antiandrogen at day 20 than at day 80 p.c. Immunohistochemistry showed the positive immunostaining for FSHR in the oocytes, granulosa cells of primary follicles and the surface epithelium of the ovaries from both control and flutamide‐treated pigs. However, oocytes and granulosa cells of primary follicles in the ovaries exposed in utero to flutamide were weakly immunostained when compared to those in the control ones. The presence of FSHR protein in all investigated ovaries was confirmed by Western blot analysis. Based on our findings, we suggest that FSHR may be involved in the early follicle formation in pigs, which begins during prenatal life. Furthermore, the regulation of FSHR mRNA and protein expression in neonatal porcine ovaries after maternal exposure to flutamide confirms that androgens play a crucial role in porcine folliculogenesis at the early stages.     

Effects of the phytoestrogen,genistein, and protein tyrosine kinase inhibitor–dependent mechanisms on steroidogenesis and estrogen receptor expression in porcine granulosa cells of medium follicles

The use of soy-based products in pig diets had raised concerns regarding the reproductive toxicity of genistein, the predominant isoflavone in soybeans. Genistein was reported to exhibit weak estrogenic activity but its mechanism of action is not fully recognized. The aim of the study was to examine the in vitro effects of genistein on (1) progesterone (P₄) and estradiol (E₂) secretion by porcine granulosa cells harvested from medium follicles, (2) the viability of cultured granulosa cells, and (3) the mRNA and protein expression of estrogen receptors α and β (ERα and ERβ) in these cells. In addition, to verify the role of protein tyrosine kinase (PTK)–dependent mechanisms possibly involved in genistein biological action, we tested the effects of lavendustin C, the nonsteroidal PTK inhibitor, on granulosa cell steroidogenesis. We found that genistein inhibited (P < 0.05) basal P₄ secretion by granulosa cells harvested from medium follicles of pigs. In contrast, lavendustin C did not affect basal P₄ secretion by the cells. Moreover, genistein increased (P < 0.05) basal granulosal secretion of E₂. In contrast, lavendustin C did not alter basal E₂ secretion by porcine granulosa cells. In addition, we demonstrated that genistein increased mRNA and protein expression of ERβ (P < 0.05) in the examined cells. The expression of ERα mRNA was not affected by genistein and ERα protein was not detected in the cultured granulosa cells of pigs. In summary, the genistein action on follicular steroidogenesis in pigs involved changes in the granulosal expression of ERβ. However, the genistein action on P₄ and E₂ production by granulosa cells harvested from medium follicles did not seem to be associated with PTK.     

Resveratrol-induced mitochondrial synthesis and autophagy in oocytes derived from early antral follicles of aged cows

Mitochondrial numbers increase during oocyte growth. In this study, we collected oocytes and granulosa cell complexes (OGCs) from early antral follicles (EAFs) of aged cows (> 120 months of age) and examined the effects of resveratrol on mitochondrial generation, degradation, and quality in oocytes grown in vitro. We also examined the effects of resveratrol on gene expression of the granulosa cells. Resveratrol (20 µM) enhanced the expression of SIRT1 and induced autophagy in both granulosa cells and oocytes derived from aged cows. Culturing the OGCs with resveratrol increased mitochondrial DNA copy numbers in oocytes grown in vitro. Furthermore, resveratrol increased the ATP content in oocytes and improved the developmental ability of the oocytes to the blastocyst stage. Gene expression profiles in granulosa cells, as evaluated by next-generation sequencing technology, revealed that resveratrol enhanced the expression of EIF2-related genes but downregulated the expression of mammalian target of rapamycin (mTOR)-, inflammation-, and cholesterol homeostasis-related genes in granulosa cells. In conclusion, resveratrol affected both oocytes and granulosa cells derived from aged cows and improved the quality of oocytes grown in vitro through upregulation of mitochondrial biogenesis and degradation in growing oocytes and conditioning of granulosa cells.     

牦牛FHL2基因的克隆、组织表达与蛋白定位分析

旨在获得牦牛FHL2基因序列，阐明该基因序列、蛋白质结构与性质、mRNA的组织表达模式、在雌性生殖器官及颗粒细胞的蛋白表达特性。本研究以5头健康空怀成年母牦牛的心、肝、脾、肺、肾、卵巢、子宫、输卵管组织及5头妊娠2个月左右母牦牛的子宫、输卵管和卵巢为研究材料，利用逆转录PCR(RT-PCR)技术克隆FHL2基因，并使用在线分子生物学软件分析其生物信息学特性；利用实时荧光定量PCR(RT-qPCR)技术分析FHL2基因的组织表达特性；应用免疫组化(IHC)和免疫荧光(IF)技术检测FHL2蛋白在雌性生殖器官的分布和颗粒细胞上的亚细胞定位。结果发现，FHL2基因CDS区全长840 bp (ON456866),编码279个氨基酸，FHL2蛋白属于弱碱性亲水不稳定蛋白，没有跨膜结构。不同物种的FHL2氨基酸序列比对和进化树分析表明，FHL2基因编码区在物种进化中比较保守。RT-qPCR结果显示，FHL2基因在检测的组织都有表达，在心的表达量极显著高于其他检测组织(P<0.01);在肺、卵巢、输卵管和子宫中的表达量极显著高于肝、脾和肾(P<0.01)。FHL2基因在妊娠期子宫中的表达...     

FSH up-regulates angiogenic factors in luteal cells of buffaloes

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

Gene expression and immunolocalization of fibroblast growth factor 2 in the ovary and its effect on the in vitro culture of caprine preantral ovarian follicles

This study quantified Fibroblast growth factor 2 (FGF-2) mRNA and localized FGF-2 protein in different categories of follicles isolated from goat ovaries. In addition, we verified the effects of this factor on the in vitro culture of preantral follicles isolated from goats. For mRNA quantification, we performed real-time PCR using primordial, primary and secondary follicles, as well as cumulus-oocyte complexes (COCs) and mural granulosa and theca cells of small and large antral follicles. For FGF-2 protein localization, the ovaries were subjected to conventional immunohistochemical procedures. Preantral follicles were isolated and cultured in vitro for 12 days in either control (basic) or supplemented with FGF-2 medium. The expression of FGF-2 mRNA was detected in all categories of follicles and there was no difference in preantral follicles and COCs or granulosa/theca cells from small and large antral follicles. However, in large antral follicles, COCs showed expression levels significantly lower than in granulosa/theca cells (p < 0.05). We observed moderate expression of FGF-2 protein in preantral follicles but not in granulosa cells of primordial follicles and theca cells of secondary follicles. In both small and large antral follicles, strong, moderate and weak staining was observed in oocytes, granulosa and theca cells, respectively. The addition of FGF-2 caused a significant increase in the daily follicular growth rate compared to the control group. We conclude that FGF-2 mRNA is expressed throughout follicular development and that its protein can be found in different patterns in preantral and antral follicles. Furthermore, FGF-2 increases the follicular growth rate in vitro.     

Mechanistic target of rapamycin is activated in bovine granulosa cells after LH surge but is not essential for ovulation

The LH surge induces functional and morphological changes in granulosa cells. Mechanistic target of rapamycin (mTOR) is an integrator of signalling pathways in multiple cell types. We hypothesized that mTOR kinase activity integrates and modulates molecular pathways induced by LH in granulosa cells during the preovulatory period. Cows were ovariectomized and granulosa cells collected at 0, 3, 6, 12 and 24 hr after GnRH injection. While RHEB mRNA levels increased at 3 and 6 hr, returning to basal levels by 12 hr after GnRH treatment, RHOA mRNA levels increased at 6 hr and remained high thereafter. Western blot analyses revealed increased S6K phosphorylation at 3 and 6 hr after GnRH injection. Similarly, mRNA levels of ERK1/2, STAR and EGR‐1 were higher 3 hr after GnRH treatment. Rapamycin treatment inhibited mTOR activity and increased AKT activity, but did not alter ERK1/2 phosphorylation and EGR1 protein levels in cultured bovine granulosa cells. Rapamycin also inhibited LH‐induced increase in EREG mRNA abundance in granulosa cells in vitro. However, intrafollicular injection of rapamycin did not suppress ovulation. These findings suggest that mTOR is involved in the control of EREG expression in cattle, which may be triggered by LH surge stimulating RHEB and S6K activity.