Expression and functional role of Bone Morphogenetic Proteins (BMPs) in cyclical corpus luteum in buffalo (Bubalus bubalis)

The role of growth factors in the modulation of ovarian function is an interesting area of research in reproductive biology. Recently, we have shown the expression and role of IGF, EGF, VEGF and FGF in the follicle and CL. Here, we report the presence of Bone Morphogenetic Proteins (BMPs) and their functional receptors in the corpus luteum (CL) of buffalo. The bubaline CL was classified into four stages according to the morphology and progesterone (P4) concentration. The qPCR, immunoblot and immunohistochemistry studies revealed that BMP2 and BMP Receptors (BMPR1A, BMPR1B and BMPR2) were significantly upregulated during the mid stage whereas BMP4 and BMP7 were upregulated during the early stage of CL (P < 0.05). Studies on primary luteal cell culture (LCC) using mid CL showed a significant time and concentration dependent effect of BMP4 and BMP7 (P < 0.05). At 100 ng ml−1, the BMPs maximally stimulated the transcripts of StAR, CYP11A1 and 3βHSD that paralleled with P4 accretion in the media (P < 0.05). Further, the BMP4 as well as BMP7 upregulated the transcripts of PCNA and downregulated CASPASE3 in the LCC at the same concentration (P < 0.05). Though the combined effect of BMP4 and 7 was significantly higher (P < 0.05) than that of individual one, it was not additive. In conclusion, the expression of BMPs and their receptors were dependent on the stages of CL in the buffalo. Treatment of LCC with BMPs in vitro confirmed the presence of functional receptors that stimulated the P4 production and luteal cell survival. Moreover, the results support the concept that the upregulation of P4 and its biosynthetic pathway enzymes such as CYP11A1, StAR and 3βHSD in the CL is likely due to the autocrine and /or paracrine effects of BMP4 and BMP7 under physiological milieu.