MiR‐9 regulates cell survival by targeting protogenin during chondrogenesis

The purpose of this study was to investigate the role of miR‐9 during the chondrogenic differentiation of limb mesenchymal cells. Treatment of JNK inhibitor suppressed precartilage condensation and chondrogenic differentiation of chick limb mesenchymal cells by upregulating apoptotic cell death. Furthermore, the expression level of miR‐9 was down‐regulated by the blockade of JNK signaling. Consistent with data with JNK exposure, inhibition of miR‐9 using PNA‐based ASOs increased apoptotic cell death and resulted in a decreased cellular condensation. Target validation system was confirmed that miR‐9 is responsible for post‐translational regulation of Prtg that suppressed chondrogenic differentiation in a manner similar to that observed when these cells were introduced by miR‐9 inhibitor or JNK inhibitor. This study suggest that Prtg regulated post‐translationally by miR‐9 exploit inhibitory action on cell proliferation/survival during chondrogenesis.