Repertoire of noncoding RNAs in corpus luteum of early pregnancy in buffalo (Bubalus bubalis)

Urinary Cell-Free miR-99a-5p as a Potential Biomarker for Estrus Detection in Buffalo

Accurate estrus detection method is the need of the hour to improve reproductive efficiency of buffaloes in dairy industry, as the currently available estrus detection methods/tools lack high sensitivity and specificity. Recently, circulating miRNAs have been shown as non-invasive biomarkers by various studies. Hence, in order to evaluate their potential as estrus biomarkers, the objective of this study was to identify and compare the levels of 10 hormone-responsive miRNAs in the urine collected at proestrus (PE), estrus (E), and diestrus (DE) phases of buffaloes (n = 3) pertaining to a discovery sample. Among 10 urinary miRNAs, the levels of bta-mir-99a-5p (E/PE 0.5-fold, P < 0.05; DE/PE 1.9-fold), bta-miR-125b (E/PE 0.5-fold; DE/PE 0.7-fold), bta-mir-145 (E/PE 1.5-fold; DE/PE 0.7-fold), bta-mir-210 (E/PE 1.2-fold, DE/PE 0.7-fold), mir-21 (E/PE 1.5-fold, DE/PE 2-fold), and bta-mir-191 (E/PE 1.3-fold; DE/PE 0.8-fold) were found to be altered during different phases of buffalo estrous cycle. In contrast, bta-mir-126-3p, bta-let-7f, bta-mir-16b, and bta-mir-378 were undetected in buffalo urine. Furthermore, a validation study in an independent group of 25 buffalo heifers showed the increased levels of urinary bta-mir-99a-5p during the DE (3.92-fold; P < 0.0001) phase as compared to the E phase. Receiver operating characteristic curve analyses also revealed the ability of urinary miR-99a-5p in distinguishing the E from the DE phase (area under the curve of 0.6464; P < 0.08). In silico analysis further showed an enrichment of miR-99a-5p putative targets in various ovarian signaling pathways, including androgen/estrogen/progesterone biosynthesis and apoptosis signaling, implicating the role of miR-99a-5p in ovarian physiology. In conclusion, significantly lower levels of bta-mir-99a-5p at the E phase than the DE phase in buffalo urine indicate its biomarker potential, which needs to be further explored in a large cohort in the future studies.

Heat exposure affected the reproductive performance of pregnant mice: Enhancement of autophagy and alteration of subcellular structure in the corpus luteum

To investigate whether autophagy and subcellular changes are involved in the corpus luteum after heat exposure, a total of 30 early pregnant mice were divided equally into heat stress (HS) and non-HS (NHS) groups (n = 15). Mice in the HS group were exposed to 40.5 ± 0.2 ℃ for 7 consecutive days. Ovaries were collected for immunohistochemistry (IHC), western blot (WB) analysis and transmission electron microscopy (TEM). Serum was collected to determine progesterone by RIA and uteri were collected to count the implantation sites. Results showed that heat exposure increased rectal temperature, decreased body weight and number of implantation sites. WB analysis revealed that ovarian expression of LC3B and Atg7 was up-regulated, while p62 was down-regulated in the HS group. IHC results demonstrated that ovarian staining intensity of LC3B was more intense in the HS group than that of the NHS group. LC3B was mainly localized in the granulosa cells, oocytes and luteal steroidogenic cells of the HS group. TEM results revealed double-layered separated membranes indicative of autophagosomes in the luteal steroidogenic cells of the HS group. Moreover, TEM showed that the mitochondrial cristae became dearth, structure-less, swollen after HS. Additionally, the nucleus expanded and accumulation of lipid droplets increased after HS. Results also showed that heat exposure decreased serum progesterone level and ovarian P450scc expression. These results indicate that HS enhanced autophagy and altered the subcellular structure of luteal steroidogenic cells, which may contribute to interfering with the maintenance of luteal function in early pregnant mice.

Endogenous and Exogenous Modulation of Nrf2 Mediated Oxidative Stress Response in Bovine Granulosa Cells: Potential Implication for Ovarian Function

Nrf2 is a redox sensitive transcription factor regulating the expression of antioxidant genes as defense mechanism against various stressors. The aim of this study is to investigate the potential role of noncoding miRNAs as endogenous and quercetin as exogenous regulators of Nrf2 pathway in bovine granulosa cells. For this cultured granulosa cells were used for modulation of miRNAs (miR-28, 153 and miR-708) targeting the bovine Nrf2 and supplementation of quercentin to investigate the regulatory mechanisms of the Nrf2 antioxidant system. Moreover, cultured cells were treated with hydrogen peroxide to induce oxidative stress in those cells. Our results showed that, oxidative stress activated the expression of Nrf2 as a defense mechanism, while suppressing the expression of those miRNAs. Overexpression of those miRNAs resulted in downregulation of Nrf2 expression resulted in higher ROS accumulation, reduced mitochondrial activity and cellular proliferation. Quercetin supplementation showed its protective role against oxidative stress induced by H₂O₂ by inducing the expression of antioxidant enzymes. In conclusion, this study highlighted the involvement of miR-153, miR-28 and miR-708 in regulatory network of Nrf2 mediated antioxidant system in bovine granulosa cells function. Furthermore, quercetin at a low dose played a protective role in bovine granulosa cells against oxidative stress damage.