To uncover the mechanism of fibroproliferative tissue formation in early-stage fibrodysplasia ossificans progressiva (FOP), mesenchymal stromal cells (MSCs) from patient-derived induced pluripotent stem cells and FOP model mice carrying the human ACVR1 (R206H) allele were examined. This evidence concerns the gene ACVR1 and fibrodysplasia ossificans progressiva.