BackgroundAnimal studies have demonstrated the therapeutic effect of mesenchymal stem cells (MSCs) on osteogenesis, but little is known about the functions of exosomes (Exos) released by bone MSCs (BMSCs). Here, we investigated the effect of BMSC Exos on steroid-induced femoral head necrosis (SFHN) and explored the vital genes involved in this process.Materials and methodsBMSCs were isolated from healthy and SFHN rats. BMSC Exos were isolated using the Exosome Precipitation Kit and characterized by transmission electron microscopy and Western blotting. SFHN BMSCs were incubated with Exos from healthy BMSCs. Osteogenic ability was assessed by oil red O staining and alizarine red staining. Differentially expressed genes (DEGs) induced by Exos were screened using the Osteogenesis RT2 Profiler PCR Array. The effect of upregulated Sox9 was examined using lentivirus-mediated siRNA.ResultsThe results revealed that BMSC Exos were 100–150 nm in size and expressed CD63. Moreover, BMSC Exo-treated SFHN cells exhibited suppressed adipogenesis compared to model cells. PCR array showed that eleven and nine genes were upregulated and downregulated, respectively, in the BMSC Exo-treated SFHN cells compared to the model group. Among the DEGs, osteogenesis-related genes, including Bmp2, Bmp6, Bmpr1b, Mmp9, and Sox9, may play important roles in SFHN. Furthermore, the DEGs were mainly involved in immune response, osteoblast differentiation, and in the transforming growth factor-β/bone morphogenetic protein signaling pathway. The level of the SOX9 protein was upregulated by Exos, and Sox9 silencing significantly decreased the osteogenic effect of BMSC Exos.ConclusionOur data suggest that Exos derived from BMSCs mainly affect SFHN osteogenesis, and this finding can be further investigated to develop a novel therapeutic agent for SFHN.

Purpose Steroids are known to inhibit osteogenic differentiation and subsequent bone formation in bone mesenchymal stem cells (BMSCs). However, little is known about the role of BMSC exosomes (Exos) and tRNA-derived small RNAs (tsRNAs) in steroid-induced osteonecrosis of the femoral head (SONFH). The objective of this study was to characterize the tsRNA expression profiles of plasma Exos collected from SONFH patients and healthy individuals using small RNA sequencing and further explore the effect of BMSC Exos carrying specific tsRNAs on osteogenic differentiation. Materials and Methods Based on insights from small RNA sequencing, five differentially expressed (DE) tsRNAs were selected for quantitative real-time polymerase chain reaction (qRT-PCR). The regulatory networks associated with interactions of the tsRNAs-mRNA-pathways were reconstructed. The osteogenesis and adipogenesis in BMSCs were detected via ALP and oil red O staining methods, respectively. Results A total of 345 DE small RNAs were screened, including 223 DE tsRNAs. The DE tsRNAs were enriched in Wnt signaling pathway and osteogenic differentiation. We identified five DE tsRNAs, among which tsRNA-10277 was significantly downregulated in plasma Exos of SONFH patients compared to that in healthy individuals. Dexamethasone-induced BMSCs were associated with an increased fraction of lipid droplets and decreased osteogenic differentiation, whereas BMSC Exos restored the osteogenic differentiation of that. After treatment of tsRNA-10277-loaded BMSC Exos, the lipid droplets and osteogenic differentiation ability were found to be decreased and enhanced in dexamethasone-induced BMSCs, respectively. Conclusion An altered tsRNA profile might be involved in the pathophysiology of SONFH. tsRNA-10277-loaded BMSC Exos enhanced osteogenic differentiation ability of dexamethasone-induced BMSCs. Our results provide novel insights into the osteogenic effect of BMSC Exos carrying specific tsRNAs on SONFH.

Mesenchymal stem cell (MSC)-derived exosomes (Exos) enhanced new bone formation, coupled with positive effects on osteogenesis and angiogenesis. This study aims to define the role of microRNA (miR)-21-5p delivered by human umbilical MSC-derived Exos (hucMSC-Exos) in the osteonecrosis of the femoral head (ONFH). We first validated that miR-21-5p expression was downregulated in the cartilage tissues of ONFH patients. Besides, hucMSCs delivered miR-21-5p to hFOB1.19 cells and human umbilical vein endothelial cells (HUVECs) through the secreted Exos. Loss- and gain-of-function approaches were performed to clarify the effects of Exo-miR-21-5p, SOX5, and EZH2 on HUVEC angiogenesis and hFOB1.19 cell osteogenesis. It was established that Exo-miR-21-5p augments HUVEC angiogenesis and hFOB1.19 cell osteogenesis in vitro, as reflected by elevated alkaline phosphatase (ALP) activity and calcium deposition, and increased the expression of osteogenesis-related markers OCN, Runx2 and Collagen I. Mechanistically, miR-21-5p targeted SOX5 and negatively regulated its expression, while SOX5 subsequently promoted the transcription of EZH2. Ectopically expressed SOX5 or EZH2 could counterweigh the effect of Exo-miR-21-5p. Further, hucMSC-Exos containing miR-21-5p repressed the expression of SOX5 and EZH2 and augmented angiogenesis and osteogenesis in vivo. Altogether, our study uncovered the role of miR-21-5p shuttled by hucMSC-Exos, in promoting angiogenesis and osteogenesis, which may be a potential therapeutic target for ONFH.

Objective The present study aimed to identify the relationship of α‐2‐macroglobulin and microvascular vessel pathology with steroid‐induced femoral head necrosis in the Southeast Chinese population. Methods This study enrolled 40 patients diagnosed with steroid‐induced necrosis of the femoral head. Patients had various stages of femoral head necrosis. The differential expression of serum proteins and mRNA from patients with steroid‐induced necrosis of the femoral head (SINFH) and healthy volunteers was analyzed by western blot and quantitative polymerase chain reaction (QT‐PCR). The pathological change in osteocyte necrosis was indicated by hematoxylin and eosin stain and immunohistochemistry. Results Hematoxylin and eosin stain showed histopathology changes in the necrotic area of patients with steroid‐induced INFH: bone trabeculae were fewer and thinner, became broken, fragmented and structurally disordered; intraosseous adipose cells became enlarged; the arrangement of the osteoblasts became irregular; and vacant bone lacunae increased. QT‐PCR showed significantly lower levels of α‐2‐macroglobulin in the serum of patients with SINFH than in controls (P < 0.05). Immunohistochemical staining and western blotting demonstrated that the expression of α‐2‐macroglobulin was significantly decreased in the necrotic area of SINFH patients (P < 0.05). Conclusion The α‐2‐macroglobulin may be associated with the pathology of SINFH. The multiple pathological reactions occur in SINFH and α‐2‐macroglobulin may serve as a potential biomarker for the diagnosis of SINFH or a promising therapeutic target.

Background: Osteonecrosis of femoral head (ONFH) is a common ischemic disease that induces femoral head necrosis. The role of exosomes and miRNA in ONFH has been elucidated, however, whether miRNA-modified exosomes improve the therapy of ONFH is not clear.Methods: We screened ONFH-related miRNAs by RNA sequencing in plasma exosomes of ONFH patients and healthy donors. The key miRNA was overexpressed in bone marrow mesenchymal stem cells (BMSC) exosomes. The regulatory functions of miRNA-modified BMSC exosomes in vascular endothelial cells were illustrated through angiogenesis assay and scratch assay.Results: We identified 9 differently expressed miRNAs (DEmiRNAs) in plasma exosomes between ONFH and healthy groups, with 6 up-regulated and 3 down-regulated miRNAs. Function and pathway analysis revealed DEmiRNAs were primarily involved in angiogenesis, cell migration, focal adhesion. Moreover, miR-150-5p was declined in ONFH exosomes and regulated multiple angiogenesis-related pathways. The miR-150-5p-overexpressed BMSC exosomes were successfully obtained and transported miR-150-5p to endothelial cells. Moreover, the miR-150-5p-modified BMSC exosomes promoted the angiogenesis and migration of endothelial cells.Conclusion: Our results elucidate the exosomal miRNA expression profiles in ONFH, and miR-150-5p-modified BMSC exosomes protect against ONFH by promoting angiogenesis, suggesting a new molecular knowledge for the clinical application of ONFH.