Knockdown of CEBPβ by RNAi in porcine granulosa cells resulted in S phase cell cycle arrest and decreased progesterone and estradiol synthesis

Cultured ovarian granulosa cells (GCs) are essential models to study molecular mechanisms of gene regulation during folliculogenesis. CCAAT enhancer binding proteins beta (CEBP beta) has been identified in the ovary and is critical for follicular growth, ovulation and luteinization in mice. In the present study, hormonal treatment indicated that luteinizing hormone (LH) and exogenous human chorionic gonadotropins (hCG) significantly increased the expression of CEBP beta in porcine GCs. By RNAi-Ready pSIREN-RetroQ-ZsGreen Vector mediated recombinant pshRNA vectors, CEBP beta gene was successfully knocked down in porcine GCs, confirmed by mRNA and protein level analyzed by real time PCR and western blot, respectively. We further found that knockdown of CEBP beta significantly increased the expression of p-ERK1/2. Furthermore, CEBP beta knockdown arrested the GCs at S phase of cell cycle, but had no effects on cell apoptosis. More importantly, it markedly down regulated the concentration of estradiol (E2) and progesterone (P4) in the culture medium. To uncover the regulatory mechanism of CEBP beta knockdown on cell cycle and steroids synthesis, we found that the mRNA expression of bcl-2 (anti-apoptosis), StAR and Runx2 (steroid hormone synthesis) was up-regulated, while genes related to apoptosis (Caspase-3 and p53), hormonal synthesis (CYP11A1) and cell cycle (cyclinA1, cyclinB1, cyclinD1) were down-regulated, suggesting that knockdown of CEBP beta may inhibit apoptosis, regulate cell cycle and hormone secretions at the transcriptional level in porcine GCs. Furthermore, knockdown of CEBP beta significantly increased the expression of PTGS2 and decreased the expression of IGFBP4, Has2 and PTGFR which are important for folliculogenesis in porcine GCs. In conclusion, this study reveals that CEBP beta is a key regulator of porcine GCs through modulation of cell cycle, apoptosis, steroid synthesis, and other regulators of folliculogenesis. (C) 2014 Elsevier Ltd. All rights reserved.