TGF-β1 Down-Regulates Vascular Cell Adhesion Molecule 1 in Porcine Follicular Granulosa Cells Through Smad2 Signalling Pathways.

The TGF-β/Smad signalling pathway plays a critical regulatory role in mammalian follicular development. Vascular Cell Adhesion Molecule 1 (VCAM1), as a member of the immunoglobulin (Ig) superfamily, is commonly expressed in various cells of the mammalian ovary and affects ovarian development. Previous studies have shown that TGF-β1 is a regulator that down-regulates the expression of VCAM1 in human granulosa cells, but its specific mechanism remains unclear. In this study, we revealed that in porcine follicular granulosa cells, TGF-β1 reduces VCAM1 expression by activating TGF-β receptor type I and through the Smad pathway. This down-regulation can be completely reversed by knockdown of Smad2, but not Smad3, suggesting that Smad2 may exert a non-redundant, specialised function in the regulation of VCAM1 by the TGF-β/Smad signalling pathway. These results enhance the understanding of the regulatory mechanisms of the TGF-β signalling pathway in reproduction and provide a theoretical basis for the regulation of reproductive traits.