Preprints

Fanconi Anemia (FA) is an inherited DNA-repair deficiency caused by mutations in diverse Fanc genes that leads to bone marrow failure and malignancies. FA disease begins at early embryonic stages, and while FA prenatal testing has long been available, no fetal therapies for FA currently exist. Postnatally, FA hematologic disease can be cured through allogeneic hematopoietic stem cell transplantation (HSCT); however, this requires chemotherapy and/or irradiation-based conditioning which amongst various side-effects also increases likelihood of malignancies later in life in these fragile patients. Given fetal immune tolerance and the competitive advantage of healthy hematopoietic stem and progenitor cells (HSPCs) over failing FA HSPCs, in utero HSCT without conditioning may be an alternative approach to stabilization of the hematopoietic system without conventional toxicities. We performed in utero HSCT using HSPCs from wildtype (WT) donors into two FA mouse models ( Fancd2 −/− , Fanca −/− ) and observed robust multi-lineage hematopoietic donor engraftment in homozygous FA mice compared to both heterozygous FA and WT littermates. Upon serial assessments, we also observed increasing donor chimerism up to 94.1%, showcasing the competitive advantage of WT donor HSPCs over FA HSPCs. Given that 1% donor chimerism is predicted to stabilize FA BM, in utero HSCT may be a safe and curative prenatal treatment for all subtypes of FA.