Biodistribution of transplanted hematopoietic precursor cells injected through different administration routes in newborn mice.

Hematopoietic stem cell transplantation has been studied for several decades now, mostly as a treatment for malignancies and hematological diseases but also for genetic metabolic disorders. Since many diseases that could be potentially treated with this approach develop early in life, studies of cell transplantation in newborn mice are needed, especially for gene therapy protocols. However, the small size of pups restricts the possibilities for routes of administration, and the ones available are normally technically challenging. Our goal was to test different routes of administration of Lin- cells in 2-days-old mice: intraperitoneal (IP), intravenous via temporal vein (TV), and intravenous via retro-orbital sinus (RO). Routes were evaluated by their easiness of execution and their influence in the biodistribution of cells in short (48 h) and medium (30 d) term. In either 48 h or 30 d, all three routes presented similar results, with cells goings mostly to bone marrow, liver and spleen in roughly the same amount. Retro-orbital injection resulted in quick distribution of cells to the brain, suggesting better performance than the others. Rate of failure was higher for the TV route, which was also the hardest to execute, while the other two were considered easier. In conclusion, while TV was the hardest to perform, all routes seemed to demonstrate similar results for cell biodistribution. In particular, the RO injection results in quicker biodistribution of cells to the brain, which is particularly important in the study of genetic metabolic disorders with a neurological component.