MicroRNA network regulation of developmental bone toxicity in a human embryonic stem cell osteogenic model

Developmental exposure to environmental toxicants is a cause of skeletal abnormalities. Yet the molecular mechanisms linking early exposure to impaired bone formation remain undefined. Skeletal tissues arise from both neural crest- and mesoderm-derived lineages that rely on shared osteogenic differentiation programs, suggesting that disruption of common regulatory processes may contribute to diverse skeletal outcomes. MicroRNAs (miRNAs) are key post-transcriptional regulators of gene networks and have appeared as indicators of toxicant-induced perturbation. In this study, we examined whether developmentally relevant toxicants are associated with miRNA regulatory networks during osteogenic differentiation. Using a human embryonic stem cell (hESC)-based osteogenic differentiation model, we assessed the effects of nine toxicants spanning distinct primary mechanisms. Toxicant exposure impaired osteogenic differentiation at their IC50, as reflected by altered expression of osteogenic markers and transcriptional remodeling. Global miRNA profiling revealed dysregulation of miRNAs enriched for bone-related biological processes, including regulators of osteogenic commitment and differentiation timing. Integrated miRNA-mRNA network analysis identified a subset of miRNAs linked to core osteogenic and lineage-associated pathways, including RUNX2-dependent transcription and BMP and Wnt signaling. Modulation of representative miRNAs produced osteogenic outcomes consistent with those observed following toxicant exposure and, in some cases, was associated with partial restoration of differentiation in exposed cultures. Collectively, these findings indicate that chemically diverse developmental toxicants are associated with miRNA-mediated regulatory patterns during osteogenic differentiation. Identification of shared miRNA regulatory features provides mechanistic insight into developmental bone toxicity and supports the use of miRNA network analysis as a human-relevant endpoint for skeletal hazard identification.