Lack of FSH support enhances LIF–STAT3 signaling in granulosa cells of atretic follicles in cattle

Abstract

Subordinate follicles (SFs) of bovine follicular waves undergo atresia due to declining FSH concentrations; however, the signalling mechanisms have not been fully deciphered. We used an FSH-induced co-dominance model to determine the effect of FSH on signalling pathways in granulosa cells of the second-largest follicles (SF in control cows and co-dominant follicle (co-DF2) in FSH-treated cows). The SF was smaller than DF in control cows while diameters of co-DF1 and co-DF2 in FSH-treated cows were similar. The presence of cleaved CASP3 protein confirmed that granulosa cells of SFs, but not of DFs and co-DFs, were apoptotic. To determine the effect of FSH on molecular characteristics of the second-largest follicles, we generated relative variables for the second largest follicle in each cow. For this, variables of SF or co-DF2 were divided by the variables of the largest follicle DF or co-DF1 in each cow. There was higher transcript abundance of MAPK1/3 and AKT1/2/3 but lower abundance of phosphorylated MAPK3/1 in SF than co-DF2 granulosa cells. Abundance of mRNA and phosphorylated protein of STAT3 was higher in granulosa cells of control SF than FSH-treated co-DF2. SF granulosa cells had higher levels of LIFR and IL6ST transcripts, the two receptors involved in STAT3 activation. Further, lower transcript abundance of interleukin 6 receptor (IL6R), another receptor involved in STAT3 activation, indicated that STAT3 activation in SF granulosa cells could be mainly due to leukemia inhibitory factor (LIF) signalling. These results indicate that atresia due to lack of FSH is associated with activated LIF-STAT3 signalling in SF granulosa cells, as FSH treatment reversed such activation. Reproduction (2015) 150 395-403

Regulation of Anti‐Müllerian Hormone and Its Receptor Expression around Follicle Deviation in Cattle

“…As mentioned above, diameter profiles of follicles in FSH‐treated and control cows have already been published (Ilha et al. ). Follicular diameters were similar in co‐dominant follicles of FSH‐treated cows, but larger (p < 0.05) for DFs than SFs of control cows.…”

“…Granulosa cell samples for this experiment were obtained from our recently published study (Ilha et al. ). Briefly, beef cows (4 to 7 years old) with regular oestrous cycles were synchronized with two injections of sodium cloprostenol (Ciosin; Intervet/Schering‐Plough; 250 μg; i.m.)…”

Molecular characteristics of granulosa and cumulus cells and oocyte competence in Nelore cows with low and high numbers of antral follicles

“…This gene is known to mediate cytokines’ signalling and regulate oocyte cytoplasmic and nuclear maturation, stimulate cell proliferation and differentiation, and mediate cell apoptosis (Dang‐Nguyen et al., ; Rawlings, Rosler, & Harrison, ). It has been shown that the STAT3 signalling pathway is involved in granulosa cell apoptosis during follicular atresia (Gasperin et al., ; Ilha et al., ). Interestingly, we have observed that STAT3 mRNA was only differently expressed in the cumulus but not in granulosa cells from low vs. high AF cows.…”

Methods to study ovarian function in monovulatory species using the cow as a model

“…The two largest follicles can be collected at specific time-points, such as 12 h after the last dose of FSH or saline (day 4; Fig. 1B; Ilha et al, 2015). Using this model, it is possible to study the molecular signals induced by FSH treatment in follicular cells, compare dominant, codominant and subordinated follicles, as well as compare the levels of proteins diluted in the follicular fluid and plasma.…”

“…Recently, our group adopted the simultaneous extraction of RNA, DNA and protein from the same sample using commercial kits Ilha et al, 2015;Rosa et al, 2016). This approach allows the evaluation of candidate genes and proteins at both transcriptional and translational levels in the same samples (Fig.…”