Molecular profiling of osteoprogenitor cells reveals FOS as a master regulator of bone non-union [timecourse]

Despite the advances in bone fracture treatment, a significant fraction of fracture patients will develop non-union. Most non-unions are treated with surgery since identifying the molecular causes of these defects is exceptionally challenging. In this study, compared with marrow bone, we generated a transcriptional atlas of human osteoprogenitor cells derived from healing callus and non-union fractures. Detailed comparison among the three conditions revealed a substantial similarity of callus and nonunion at the gene expression level. Nevertheless, when assayed functionally, they showed different osteogenic potential. Utilizing longitudinal transcriptional profiling of the osteoprogenitor cells, we identified FOS as a putative master regulator of non-union fractures. We validated FOS activity by profiling a validation cohort of 31 tissue samples. Our work identified new molecular targets for non-union classification and treatment while providing a valuable resource to better understand human bone healing biology. OPC were cultured in basal medium (DMEM with 1 g/L glucose, supplemented with 1x GlutaMax, 1% penicillin/streptomycin and 10% FBS). Cells were harvested at mac 80% confluence and processed for RNASeq (sampes "day 0") or seeded in 6-well plates to undergo a timecourse of osteogenic differentiation in basal medium supplemented with dexamethasone 10 nM, beta-glycerophosphate 2 mM and L-ascorbic acid-2-phosphate 50 ug/mL. Cells were then harvested after 7, 14, 21 or 28 days of differentiation (samples "day 7", "day 14", "day 21" or "day 28" respectively)