Expression of tissue factor pathway inhibitor 2 in the follicles of chicken ovaries and its regulatory mechanism in cultured granulosa cells

Tissue factor pathway inhibitor 2 (TFPI2) plays a key role in female reproduction. However, its expression and function in chickens are still unclear. In this study, RNA-seq was performed on ovarian tissues from chickens aged 30 and 15 weeks to identify the differentially expressed gene TFPI2. The full-length cDNA of TFPI2 was obtained from adult chicken ovaries by rapid-amplification of cDNA ends (RACE), and the putative TFPI2 protein was found to share a highly conserved amino acid sequence with known bird homologs. In addition, TFPI2 was widely expressed in the tissues of adult chicken follicles according to quantitative real-time PCR (qRT-PCR) and Western blotting. Immunohistochemistry suggested that the TFPI2 protein existed in chicken ovary follicles at different developmental states, such as primordial follicles, the ovarian stroma, and the granulosa and theca layers of prehierarchical follicles (6–8 mm) and preovulatory follicles (F1). In vitro, follicle stimulating hormone or luteinizing hormone (FSH/LH) stimulated the expression of TFPI2 in chicken granulosa cells. FSH-/LH-induced TFPI2 mRNA expression was mediated by signaling pathways such as the PKA, PKC, PI3K, and mTOR pathways. Functionally, TFPI2 promoted the proliferation and viability of cultured granulosa cells and decreased the secretion of Progesterone (P4) and Estrogen (E2) and the mRNA abundance of key steroidogenic enzymes (STAR, Cyp17a1, Cyp19a1 and 3B-HSD) as well as MMPs (MMP2, 7, 9 and 11). Mechanistically, TFPI2 inhibited the expression of MMP7 via the Wnt signaling pathway. These findings indicate that TFPI2 may play an important role in regulating chicken follicular development and ovulation and suggest the molecular regulation mechanisms.