circRNA3669 promotes goat endometrial epithelial cells proliferation via miR-26a/RCN2 to activate PI3K/AKT-mTOR and MAPK pathways

The development of receptive endometrium(RE) from pre-receptive endometrium(PE) for successful embryo implantation is a complex dynamic process in which the morphology and physiological states of the endometrial epithelium undergo a series of significant changes, including cell proliferation and apoptosis. However, the molecular mechanisms are not yet fully understood. In this study, a higher circRNA3669 level was observed in PE than in RE of goats. Functional assays revealed that this overexpression promoted the proliferation of goat endometrial epithelial cells(GEECs) by activating the expression of genes related to the PI3K/AKT-mTOR and MAPK pathways,thereby inhibiting apoptosis in vitro. Furthermore, circRNA3669 functioned as a competing endogenous RNA(ceRNA) to upregulate Reticulocalbin-2(RCN2) expression at the post-transcriptional level by interacting with and downregulating miR-26a in GEECs. In addition, RCN2, which is highly expressed in the PE of goats, was found to be regulated by β-estradiol(E2) and progesterone(P4). Our results demonstrated that RCN2 also affected the key proteins PI3K, AKT, mTOR, JNK, and P38 in the PI3K/AKT-mTOR and MAPK pathways, thereby facilitating GEECs proliferation and suppressing their apoptosis in vitro. Collectively, we constructed a new circRNA3669-miR-26aRCN2 regulatory network in GEECs, which further provides strong evidence that circRNA could potentially play a crucial regulatory role in the development of RE in goats.

Gut microbiota-derived metabolites contribute negatively to hindgut barrier function development at the early weaning goat model

Early weaning induces intestinal injury,leading to a series of long-term symptoms such as inflammation,malabsorption and diarrhea.In this study,we hypothesized that microbes and theirmetabolitesmodulate the host's inflammatory response to early weaning stress in a goatmodel.A total of 18 female Tibetan goat kids(n?9)wereweaned fromtheirmothers at 28 d(D28)and 60 d(D60)postpartum.D60 and D28 groupswere fed the same solid diet ad libitum fromweaning to 75 d of age.The colonic epithelium was subject to RNAsequencing,the caecal digesta metabolomics were assessed by liquid chromatographyetandem mass spectrometry(LC-MS/MS),and the caecal microbiota composition was analysed by 16S ribosomal RNA gene sequencing.We foundthatearlyweaningsubstantially increased the colonic pro-apoptotic gene expressionof B-cell lymphoma associated X(Bax),caspase-9,and caspase-3,and decreased the expression of zonula occludens-1(ZO-1)and claudin-1(P<0.01).In addition,a significant Bacteroides acidifaciens enrichmentwas observed in the hindgut of early-weaned goats(P<0.01),which negatively correlated with lysophosphatidylcholine products.Similarly,the chemokine signaling,IL-17 signaling,and peroxisome proliferatorsactivated receptor(PPAR)signaling pathways were upregulated in the colonic mucosa of the early-weaned goats.By applying caecal microbiota transplantation from goats to defaunated C57/6J mice,we confirmed that caecalmicrobiota of D28 goat kids increased the relative abundance of B.acidifaciens and significantly upregulated the genes of Bax,G proteinecoupled receptor(GPR)109A,GPR 43,fatty acid binding protein 6,nuclear receptor subfamily 1 group H member 3,angiotensin converting enzyme 2,and IL-6 expression(P<0.05),and decreased ZO-1,and claudin-1 protein expression in the mice jejunum and colon(P<0.001).These results proposed that the hindgut microbiota andmetabolites mediate the barrier functionweakening duringearlyweaning,and the relative abundance of B.acidifacienswas negatively correlatedwiththe hindgut barrier gene expression.This studydemonstrateshowweaningstress canaffectkeyhostemicrobe interaction regulators in the hindgut,in a lysophosphatidylcholine dependent and independent manner.Furthermore,based on our mice data,these results are transferable to other mammal species.