Single‑cell Transcriptomic Profiling of Bone Marrow Mesenchymal Stem Cells Reveals Lineage Heterogeneity and Dysregulated Osteoblast Genes in Osteoporosis Versus Osteoarthritis

INTRODUCTION: Osteoporosis (OP) and osteoarthritis (OA) are two skeletal disorders characterized by disrupted bone homeostasis. Transplantation of bone marrow mesenchymal stem cells (BM-MSCs) has emerged as a promising therapeutic strategy for both conditions; however, the precise molecular mechanisms mediating their beneficial effects remain poorly defined. METHODS: The GSE147287 dataset containing scRNA-seq data from BM-MSCs from OA and OP patients was obtained. Dimensionality reduction and cell clustering were performed using the Seurat R package, pseudotime trajectory analysis was carried out with the Monocle 2 package, and transcription factor (TF)-target gene regulatory networks were inferred using the GENIE3 R package. RT-qPCR quantified mRNA levels in a rat OP model, which was established via bilateral ovariectomy. RESULTS: Nine distinct BM-MSC subtypes were classified. OP samples had higher osteocytes and neutrophils and lower macrophages, chondroblasts, monocytes, and plasma B cells than OA samples. Chondroblasts (4 clusters), 2/3 linked to autophagy, may drive OA-to-OP progression. Osteoblasts (the largest OP-OA difference) showed reduced osteoblast differentiation, downregulated Wnt pathway genes, and upregulated ossification genes in late stages. In the rat model, CAT, CHRDL1, RUNX1, ETS1, FOXO3, and TAL1 were dysregulated. DISCUSSION: OP and OA exhibit distinct BM-MSC lineage heterogeneity. OA-to-OP progression involves enhanced oxidative phosphorylation and reduced autophagy. Downregulated RUNX1 (inhibiting NF-κB/IL-6) and Wnt pathway in OP were consistent with previous findings, showing the potential to serve as biomarkers for predicting disease progression and therapy response. CONCLUSION: This study preliminarily examined BM-MSC lineage heterogeneity in OP and OA, clarifying the dynamic development, transcriptional regulation, and biological functions of chondrocytes and osteoblasts in these two bone diseases.