In utero transplantation (IUT) is becoming a viable option for the treatment of various immune and metabolic disorders diagnosed early in gestation. In this study, donor fetal liver cells had a 10-fold competitive engraftment advantage relative to adult bone marrow in allogeneic fetal severe combined immunodeficient (SCID) recipients compared with adult recipients. In contrast, adult bone marrow cells engrafted slightly better than fetal liver cells in allogeneic adult SCID transplant recipients. By using different ratios of fetal and adult cell mixtures, fetal liver cells repopulated 8.2 times better than adult bone marrow cells in fetal recipients, but only 0.8 times as well in adult recipients. Fetal SCID recipients were more permissive to an allogeneic donor graft than adult recipients. These data indicate that the recipient microenvironment may regulate the engraftment efficiency of a given stem cell source and suggest that the use of cord blood should be tested in clinical IUT.

In allogeneic hematopoietic stem cell transplant recipients, restoration of humoral immunity is delayed and can remain impaired for years. In many severe combined immune deficiency (SCID) patients given haploidentical bone marrow (BM), lesions in humoral immunity are exacerbated by poor engraftment of donor B cells. The nature of these defects is important to understand as they render patients susceptible to infection. Previous work in mice suggested that in utero transplantation (

Mucopolysaccharidosis type I (MPS IH) is a lysosomal storage disease (LSD) caused by inactivating mutations to the alpha-L-iduronidase (IDUA) gene. Treatment focuses on IDUA enzyme replacement and currently employed methods can be non-uniform in their efficacy particularly for the cardiac and craniofacial pathology. Therefore, we undertook efforts to better define the pathological cascade accounting for treatment refractory manifestations and demonstrate a role for the renin angiotensin system (RAS) using the IDUA −/− mouse model. Perturbation of the RAS in the aorta was more profound in male animals suggesting a causative role in the observed gender dimorphism and angiotensin receptor blockade (ARB) resulted in improved cardiac function. Further, we show the ability of losartan to prevent shortening of the snout, a common craniofacial anomaly in IDUA −/− mice. These data show a key role for the RAS in MPS associated pathology and support the inclusion of losartan as an augmentation to current therapies.