Regulation Of Runx On The Chondrocyte Differentiation Of Sika Deer Antlers

Sika deer is one of the important medicinal economic animals, and its antlers arewidely used as precious traditional Chinese medicines. Deer antler is the uniquemammalian organ that can fully grow back once lost from its pedicle-the base fromwhich it grows. Therefore, antlers probably offer the most pertinent model forstudying organ regeneration in mammals. The Runx transcription factor familymembers Runx1, Runx2and Runx3share a high degree of sequence homology withinmost of their coding regions. The members of Runx are important factors forchondrocytes maturation and differentiation. Runx2is highly expressed inprehypertrophic chondrocytes and hypertrophic chondrocytes to induce chondrocytesto differentiate into hypertrophic chondrocytes and endochondral ossification. Runx1and Runx3also play an essential role in chondrocytes development. But theRegulation of Runx on the chondrocytes differentiation in sika deer antlers were stillunknown.The aim of this study was to investigate the expression of Runx1, Runx2andRunx3in sika deer antlers and their effects on antler chondrocytes differentiationusing in situ hybridization, real-time PCR and siRNA. Runx1, Runx2and Runx3werehighly expressed in the dermal fibroblasts, perichondrium fibrous, mesenchyme andchondrocytes, indicating that Runx1, Runx2and Runx3might be very important insika deer antler regeneration. To further understand the effects of Runx on antlerchondrocytes, we added Runx recombinant proteins or transfected Runx siRNAs intochondrocytes and then detected the expression level of chondrocyte molecularmarkers (Col II, AGC and COMP), hypertrophy chondrocyte molecular marker (ColX) and prehypertrophic chondrocytes secretory factor (IHH). The real-time PCRresults showed that the expression of Col II, AGC, COMP, Col X and MMP13wereenhanced comparing to the control after the chondrocytes were treated with Runx1recombinant protein, but the expression of IHH was significantly inhibited in antlerchondrocytes. After transfection with Runx1siRNA, Col II, AGC, COMP, Col X and MMP13were markedly declined. Meanwhile, the IHH mRNA expression was alsoinhibited. These results showed that Runx1could inhibit antler chondrocytes todifferentiate into prehypertrophic chondrocytes and induce prehypertrophicchondrocytes to differentiate into hypertrophic chondrocytes. Runx2could obviouslyinhibit the expression of Col II, AGC and COMP, but enhance markedly Col X, IHHand MMP13mRNA expression in antler chondrocytes. However, Col II, AGC andCOMP were significantly increased and Col X and IHH were declined aftertransfection with Runx2siRNA, indicating that Runx2might promote the antlerchondrocytes maturation and differentiation. After treatment with Runx3recombinantprotein, the expression of Col II, AGC, COMP, Col X and MMP13were inhibitedwhile IHH was enhanced in antler chondrocytes, while inhibition of Runx3couldenhance the expression of Col II, AGC, COMP, Col X and MMP13and decrease IHHmRNA expression, indicating that Runx3could promote antler chondrocytes todifferentiate into prehypertrophic chondrocytes and inhibit prehypertrophicchondrocytes to differentiate into hypertrophic chondrocytes.In conclusion，the Runx family members of transcription factor were closelyrelated to the maturation and differentiation of chondrocytes in sika deer antlers. Thepresent study will provide important theoretical foundation to further understand thefunction of Runx in antler regeneration.