Function and regulation of transforming growth factor β1 signalling in antler chondrocyte proliferation and differentiation

Objectives Chondrocyte proliferation and differentiation are crucial for endochondral ossification, but their regulatory mechanism remains unclear. The present study aimed to determine the physiological function of TGF beta 1 signalling in the proliferation and differentiation of antler chondrocytes and explore its relationship with Notch, Shh signalling and Foxa. Materials and methods Immunofluorescence, Western blot, MTS assay, flow cytometry, RNA interference and real-time PCR were used to analyse the function and regulatory mechanisms of TGF beta 1 signalling in antler chondrocyte proliferation and differentiation. Results TGF beta 1, TGFBR1 and TGFBR2 were highly expressed in antler cartilage. TGF beta 1 promoted chondrocyte proliferation, increased the proportion of S-phase cells and induced the expression of hypertrophic chondrocyte markers Col X, Runx2 and Alpl. However, this induction was weakened by TGF beta receptor inhibitor SB431542 and Smad3 inhibitor SIS3. Simultaneously, TGF beta 1 activated Notch and Shh signalling whose blockage attenuated the above effects of rTGF beta 1, whereas addition of rShh rescued the defects in chondrocyte proliferation and differentiation elicited by SB431542 and SIS3. Further analysis revealed that inhibition of Notch signalling impeded TGF beta 1 activation of the Shh pathway. Knockdown of Foxa1, Foxa2 and Foxa3 abrogated the effects of TGF beta 1 on chondrocyte differentiation. Notch and Shh signalling mediated the regulation of Foxa transcription factors by TGF beta 1. Conclusions TGF beta 1 signalling could induce the proliferation and differentiation of antler chondrocytes through Notch-Shh-Foxa pathway.