For 25 years, Alain Chapel has been developing gene and cell therapy using non-human primates, immune-tolerant mice, and rats to protect against the side effects of radiation. He collaborates with clinicians to develop strategies for the treatment of patients after radiotherapy overexposures. He has participated in the first establishment of proof of the concept of the therapeutic efficacy of mesenchymal stem cells (MSCs) for the treatment of hematopoietic deficit, radiodermatitis, and overdosages of radiotherapy. He has contributed to the first reported correction of deficient hematopoiesis in patients (graft failure and aplastic anemia) thanks to intravenous injection of MSCs restoring the bone marrow microenvironment, mandatory to sustain hematopoiesis after total body irradiation. He is a scientific investigator of a Clinical phase II trial evaluating the efficacy of systemic MSC injections for the treatment of severe and chronic radiotherapy-induced abdominopelvic complications refractory to standard therapy (NCT02814864Hirsch Index 27).