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 TGFβ1 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 TGFβ1 signalling in antler chondrocyte proliferation and differentiation.

Results: TGFβ1, TGFBR1 and TGFBR2 were highly expressed in antler cartilage. TGFβ1 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 TGFβ receptor inhibitor SB431542 and SMAD3 inhibitor SIS3. Simultaneously, TGFβ1 activated Notch and Shh signalling whose blockage attenuated the above effects of rTGFβ1, 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 TGFβ1 activation of the Shh pathway. Knockdown of Foxa1, Foxa2 and Foxa3 abrogated the effects of TGFβ1 on chondrocyte differentiation. Notch and Shh signalling mediated the regulation of Foxa transcription factors by TGFβ1.

Conclusions: TGFβ1 signalling could induce the proliferation and differentiation of antler chondrocytes through Notch-Shh-Foxa pathway.