Behavior and Therapeutic Efficacy of β-Glucuronidase–Positive Mononuclear Phagocytes in a Murine Model of Mucopolysaccharidosis Type VII

Bone marrow transplantation (BMT) is relatively effective for the treatment of lysosomal storage diseases. To better understand the contribution of specific hematopoietic lineages to the efficacy of BMT, we transplanted β-glucuronidase–positive mononuclear phagocytes derived from either the peritoneum or from bone marrow in vitro into syngeneic recipients with mucopolysaccharidosis type VII (MPS VII). Cell surface marking studies indicate that the bone marrow-derived cells are less mature than the peritoneal macrophages. However, both cell types retain the ability to home to tissues rich in cells of the reticuloendothelial system after intravenous injection into MPS VII mice. The half-life of both types of donor macrophages is approximately 7 days, and some cells persist for at least 30 days. In several tissues, therapeutic levels of β-glucuronidase are present, and histopathologic analysis demonstrates that lysosomal storage is dramatically reduced in the liver and spleen. Macrophages intravenously injected into newborn MPS VII mice localize to the same tissues as adult mice but are also observed in the meninges and parenchyma of the brain. These data suggest that macrophages play a significant role in the therapeutic efficacy of BMT for lysosomal storage diseases and may have implications for treatments such as gene therapy.