The Dynamics of microRNA Transcriptome in Bovine Corpus Luteum during Its Formation, Function, and Regression

Abstract

The formation, function, and subsequent regression of the ovarian corpus luteum (CL) are dynamic processes that enable ovary cyclical activity. Studies in whole ovary tissue have found microRNAs (miRNAs) to by critical for ovary function. However, relatively little is known about the role of miRNAs in the bovine CL. Utilizing small RNA next-generation sequencing we profiled miRNA transcriptome in bovine CL during the entire physiological estrous cycle, by sampling the CL on days: d 1–2, d 3–4, and d 5–7 (early CL, eCL), d 8–12 (mid CL, mCL), d 13–16 (late CL, lCL), and d > 18 (regressed CL, rCL). We characterized patterns of miRNAs abundance and identified 42 miRNAs that were consistent significantly different expressed (DE) in the eCL relative to their expression at each of the analyzed stages (mCL, lCL, and rCL). Out of these, bta-miR-210-3p, −2898, −96, −7-5p, −183-5p, −182, and −202 showed drastic up-regulation with a fold-change of ≥2.0 and adjusted P < 0.01 in the eCL, while bta-miR-146a was downregulated at lCL and rCL vs. the eCL. Another 24, 11, and 21 miRNAs were significantly DE only between individual comparisons, eCL vs. the mCL, lCL, and rCL, respectively. Irrespective of cycle stage two miRNAs, bta-miR-21-5p and bta-miR-143 were identified as the most abundant miRNAs species and show opposing expression abundance. Whilst bta-miR-21-5p peaked in number of reads in the eCL and was significantly downregulated in the mCL and lCL, bta-miR-143 reached its peak in the rCL and is significantly downregulated in the eCL. MiRNAs with significant DE in at least one cycle stage (CL class) were further grouped into eight distinct clusters by the self-organizing tree algorithm (SOTA). Half of the clusters contain miRNAs with low-expression, whilst the other half contain miRNAs with high-expression levels during eCL. Prediction analysis for significantly DE miRNAs resulted in target genes involved with CL formation, functionalization and CL regression. This study is the most comprehensive profiling of miRNA transcriptome in bovine CL covering the entire estrous cycle and provides a compact database for further functional validation and biomarker identification relevant for CL viability and fertility.

Thrombospondin-1 at the crossroads of corpus luteum fate decisions

“…Based on these findings, miR-221 is expected to be elevated during CL formation and reduced in late and regressed CL. Indeed, small RNA next-generation sequencing demonstrated that miR-221 levels vary in CL during the estrous cycle, with lower expression in late and regressed bovine CL and abundant expression in early CL (Gecaj et al 2017). This temporal expression profile of miR-221 in CL is also supported by a study reporting that miR-221 expression in bovine plasma was lower on day 16 compared with day 8 of the estrous cycle (Ioannidis & Donadeu 2016).…”

NORFA, long intergenic noncoding RNA, maintains sow fertility by inhibiting granulosa cell death

“…miRNAs have been shown to target ovarian function-related genes and control various ovarian function such as steroidogenesis 23 , folliculogenesis 24 , ovulation 25 , and luteogenesis 26 . However, little is known of the role of lncRNAs in ovarian function 27 .…”

Inflammation and angiogenesis in the corpus luteum

“…The binding between VEGF‐A and VEGFR‐2 is mainly responsible for the stimulation of angiogenesis in EC of the bovine CL . Recently, one group found that the expression of VEGF and VEGFR‐2 reached its highest level during days 1–7 of the estrous cycle in the bovine CL . As a VEGFR‐2 inhibitor, SU 1498 has been added into the luteal endothelial network in vitro using a well‐defined induced pluripotent stem cells (iPSC)‐derived EC type (iPSC‐EC) .…”

“…68 Recently, one group found that the expression of VEGF and VEGFR-2 reached its highest level during days 1-7 of the estrous cycle in the bovine CL. 69 As a VEGFR-2 inhibitor, SU 1498 has been added into the luteal endothelial network in vitro using a welldefined induced pluripotent stem cells (iPSC)-derived EC type (iPSC-EC). 70 The number of endothelial networks was reduced by 52%, and the endothelial network length decreased by 50%.…”