Bone Marrow Mesenchymal Stem Cell-Derived Exosomal miR-4787-3p Promoted Osteogenic Differentiation by Targeting PDCD4 in Osteonecrosis of Femoral Head.

Impaired osteogenic differentiation serves as a pivotal pathogenic mechanism underlying osteonecrosis of the femoral head (ONFH). This study systematically investigated the pro-osteogenic effects of exosomal miR-4787-3p derived from bone marrow mesenchymal stem cells (BMSCs) in the pathogenesis of ONFH. Bone marrow was collected from both healthy donors and patients with post-traumatic ONFH. BMSC and BMSC-derived exosomes were isolated and characterized. BMSCs were transfected with miR-4787-3p mimic and inhibitor to collect exosomes. These exosomes were used to treat BMSCs stimulated by dexamethasone (DEX). A dual luciferase reporter gene assay was employed to verify the binding of miR-4787-3p and programmed cell death 4 (PDCD4). BMSCs were transfected with PDCD4 shRNA and stimulated by DEX. BMSCs transfected by PDCD4 vectors were stimulated by exosomes and DEX. Cell counting kit-8 assay, Alizarin red staining, and ALP activity detection were performed on BMSCs. Molecular analyses included qRT-PCR and Western blot of osteogenic markers and PDCD4 signaling components. BMSC and BMSC-derived exosomes were successfully isolated. Relative to healthy donors, miR-4787-3p was downregulated in BMSC-derived exosomes from patients with traumatic ONFH. Exosomal miR-4787-3p enhanced BMSCs' viability and osteogenic differentiation, as evidenced by increased mineralization, ALP activity, and upregulation of ALP/OPN/Runx2. PDCD4 was a target of miR-4787-3p. PDCD4 was up-modulated in BMSCs from patients with traumatic ONFH. PDCD4 knockdown enhanced BMSCs' viability, Alizarin red staining, ALP activity, ALP, OPN and Runx2 expression. PDCD4 reversed BMSC-derived exosomal miR-4787-3p promotion on BMSCs' viability, Alizarin red staining, ALP activity, ALP, OPN and Runx2 expression. BMSC-derived exosomal miR-4787-3p promoted BMSCs' osteogenic differentiation through direct targeting of PDCD4. These findings suggest its potential therapeutic application for ONFH by reversing impaired osteogenesis.