Elucidating the Mechanism of Radiation Therapy on Mesenchymal Cell Fate in Heterotopic Ossification

Radiation therapy is a clinically proven, localized preventive measure for heterotopic ossification (HO). Despite its efficacy, there is a lack of standardization of radiation prescription dosing and fractionation, and the mechanism of the impact of radiation in HO prevention remains unknown. Here, using an established mouse model of traumatic HO induced by burn and tenotomy, we demonstrate that 7Gy in one fraction delivered to the injury site within 72 hours postoperatively significantly decreases HO formation and improves hindlimb range of motion. In-depth single-cell transcriptomic analyses, in combination with immunofluorescent staining, demonstrate decreased cellular numbers as well as aberrant endochondral differentiation and downregulation of associated upstream signaling pathways in irradiated mesenchymal progenitor cells. Our study provides the framework for future mechanistic and clinically relevant studies exploring radiation efficacy in preventing HO formation. To investigate the unknown mechanism of how postoperative radiotherapy prevents HO formation in a traumatic HO mouse model, cells from tenotomy inury site in control and post-radiation day 3 mice were isolated at 7 days post-injury for scRNA-seq.