Mitochondrial donor source selection for osteoporosis therapy: functional heterogeneity and quality criteria for osteogenic efficacy

Mitochondrial failure is now viewed as an active driver of bone loss in osteoporosis, not merely a downstream consequence of aging. Defective mitochondria impair osteoblast differentiation, increase osteoclast activity, and disturb redox balance in the bone marrow niche. These findings have encouraged mitochondrial transplantation as a way to restore bioenergetics and remodel the bone microenvironment. However, donor mitochondria are not interchangeable. Their metabolic phenotype, respiratory capacity, proteome, mitochondrial DNA (mtDNA) integrity, redox state, and disease history can determine whether transfer supports or suppresses osteogenesis. Osteoblast-derived mitochondria have been reported to increase alkaline phosphatase activity and osteogenic gene expression, whereas myoblast and fibroblast-derived mitochondria may inhibit osteogenic differentiation. Mitochondria from OXPHOS-dependent MG63 cells also appear to promote mesenchymal stem cells (MSCs) osteogenesis more effectively than those from glycolysis-dominant MSCs. This suggests that donor metabolic phenotype must be matched to the metabolic needs of recipient cells. Donor quality is further shaped by the pathological microenvironment. For example, osteoporosis-associated macrophages may release oxidatively damaged mitochondria that impair, rather than restore, MSC osteogenic potential. Yet the field still lacks agreed criteria for donor selection, mitochondrial manufacturing, and functional quality control. Membrane potential, respiratory capacity, mtDNA integrity, purity, sterility, immunogenicity, and biological potency are rarely measured in a harmonized manner. Disease-specific criteria for donor age, pathological exposure, metabolic phenotype, and donor–recipient compatibility are also missing. This review argues that donor mitochondrial selection is a core determinant of therapeutic direction and efficacy in osteoporosis. We classify potential donor sources in the bone microenvironment, summarize their source-dependent effects on osteogenic and osteoclastogenic processes, analyze the molecular basis of mitochondrial functional heterogeneity, and propose quality criteria relevant to osteoporosis therapy. However, many of the proposed donor-selection and quality-control criteria remain to be validated in vivo , and their clinical translation will require standardized potency assays and disease-specific preclinical models.