Repair of Calvarial Bone Defect Using Jarid1a-Knockdown Bone Mesenchymal Stem Cells in Rats

Histone methylation is regarded as an important epigenetic event during stem cell differentiation. Jumonji AT-rich interactive domain 1A (Jarid1a) is a histone demethylase that specifically catalyzes demethylation of dimethyl or trimethyl histone H3K4me3, which is normally associated with transcriptionally active genes. Runt-related transcription factor 2 (Runx2) has been identified as a key transcription factor in the early stage of osteogenesis. A better understanding of this epigenetic mechanism that governs osteogenic differentiation of bone mesenchymal stem cells (BMSCs) can provide new insights into BMSC-based bone tissue engineering. To define the function and regulatory mechanisms of Jarid1a in the osteogenic differentiation of BMSCs, we compared the expression of Jarid1a between undifferentiated and osteoinductive BMSCs. The expression of osteogenic transcriptional factors in BMSCs after Jarid1a knockdown was explored using western blot. To determine whether Jarid1a was associated with Runx2 during osteogenic differentiation, endogenous coimmunoprecipitation (co-IP) experiments were performed with osteoinductive BMSCs extracts. Then, we systematically evaluated the function of si-Jarid1a in enhancing BMSCs osteogenesis and the therapeutic potential of si-Jarid1a-modified BMSCs in a rat calvarial bone defect model with β-tricalcium phosphate scaffolds. Knockdown of Jarid1a by small interfering RNA enhanced osteogenic differentiation of BMSCs in vitro. Knockdown of Jarid1a significantly improved the mRNA and protein expression of bone-specific factors. Furthermore, co-IP in BMSCs lysate suggested that Jarid1a was physically and functionally associated with Runx2. The repair potential of bone defect was dramatically improved by Jarid1a-knockdown BMSCs, including increased bone volume, increased bone mineral density, and decreased scaffold residue in vivo. Altogether, this study explores the functional and regulatory role of Jarid1a in osteogenic differentiation and bone regeneration of BMSCs, and provides a new approach for bone defect repairing using epigenetic modification in vitro and in vivo.