Donor hematopoietic engraftment into newborn transplanted MPS I mice. (A) Experimental scheme. Newborn WT and MPS I (CD45.2) mice were conditioned with busulfan (20 mg/kg) on day 1 to 2 after birth and transplanted with 2 × 10⁶ adult BM nucleated cells (CD45.1) on the next day, as indicated. Groups were WT untreated (WT), MPS I untreated (MPS I), MPS I mice transplanted with CD45.1 donor BM cells (MPS I nBMT), and WT mice transplanted with CD45.1 donor BM cells (WT nBMT). Chimerism was determined at 4 weeks of age, and at 37 weeks of age, mice were killed for detection of long-term engraftment, biochemical, radiographic, and histological analyses. (B) Long-term donor chimerism (engraftment of CD45.1⁺ cells) was determined using flow cytometry in PB and spleen at 37 weeks of age. Upper horizontal line of box represents the 75th percentile, the lower horizontal line of box represents the 25th percentile, the horizontal bar within the box represents the median, the square within box represents the mean, and vertical lines outside the box represent the minimum and maximum. P value was calculated using Wilcoxon nonparametric unpaired test, 2 sides. (C) Representative multilineage donor-derived reconstitution was analyzed, using flow cytometry in spleen (macrophages [MAC], granulocytes [GRAN], B and T lymphoid cells) and thymus (T lymphoid cells) of recipient WT nBMT and MPS I nBMT mice.