<p>In the process of bone metabolism, osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is closely related to bone formation, remodeling and repair. As a type I transmembrane protein, DCBLD2 regulates relapsing polychondritis, but its function in the osteogenic differentiation of BMSCs remains unclear. This study aimed to investigate the effects of DCBLD2 on osteogenic differentiation in BMSCs and the underlying regulatory mechanism. Human mesenchymal stem cell osteogenic differentiation medium was used to induce the differentiation of BMSCs into osteoblasts. Osteogenic differentiation of the BMSCs was detected via ALP staining and alizarin red staining, and related genes and proteins were identified via bioinformatics analysis, RT‒qPCR and Western blotting. The binding of miR-34c-3p to DCBLD2 was detected via AGO2-RIP and dual-luciferase reporter gene experiments. This study revealed that DCBLD2 expression is downregulated during osteogenic differentiation of BMSCs. Overexpression of DCBLD2 inhibited the differentiation activity and mineralization of BMSCs while decreasing the expression of OCN, OPN, Runx2, and collagen I and ultimately inhibited the osteogenic differentiation of BMSCs. In addition, the phosphorylation levels of PI3K and AKT increased during osteogenic differentiation of BMSCs, and the PI3K activator 740 Y-P effectively reversed the inhibitory effect of DCBLD2 overexpression on BMSCs osteogenic differentiation. Conversely, miR-34c-3p expression is also upregulated during BMSCs osteogenic differentiation, and miR-34c-3p has a targeted binding relationship with DCBLD2. Knocking down DCBLD2 expression partially weakened the effect of the miR-34c-3p inhibitor and promoted the differentiation of BMSCs. In concludion, miR-34c-3p activates the PI3K/AKT signaling pathway by inhibiting the expression of DCBLD2, thereby promoting osteogenic differentiation of BMSCs.</p>