BONE-MARROW TRANSPLANTATION HAS A SIGNIFICANT EFFECT ON ENZYME LEVELS AND STORAGE OF GLYCOSAMINOGLYCANS IN TISSUES AND IN ISOLATED HEPATOCYTES OF MUCOPOLYSACCHARIDOSIS TYPE-VII MICE

The effect of bone marrow transplantation (BMT) on enzyme and glycosaminoglycan levels of various tissues and isolated parenchymal cells of lethally irradiated gus(mps/) gus(mps) mice was studied. These mice have an inherited deficiency of the lysosomal enzyme beta-glucuronidase with less than 1% of normal enzyme activity present in all tissues and represent a model of human mucopolysaccharidosis type VII. Tissues were evaluated 200 d after BMT and liver parenchymal cells 300 d after BMT. Normal levels of beta-glucuronidase activities were present in spleen and peripheral blood leukocytes of gus(mps)/gus(mps) mice that underwent transplantations. Intermediate activities were found in lung (73%), kidney (4%), liver (10%), heart (53%), muscle (55%), brain (6%), and liver parenchymal cells (10% of normal controls). A concomitant decrease in activity of the secondarily increased enzyme beta-hexosaminidase was observed. BMT also led to a substantial reduction in storage of glycosaminoglycans in lung (130 to 100%), heart (350 to 106%), kidney (439 to 217%), brain (177 to 91%), liver (613 to 125%), and liver parenchymal cells (443 to 161% of normal controls). These findings were supported by electron microscopy. A normalization of the storage process was seen in the visceral organs spleen and liver and in the histiocytes of the heart. The kidney showed variable improvement depending on the cell type. In the brain, a substantial improvement of neuronal storage was observed, but BMT apparently had no effect on storage in glial cells. The subcellular localization of beta-glucuronidase was investigated in liver parenchymal cells of mice that underwent transplantation. Subcellular fractionation provided evidence for a lysosomal localization of beta-glucuronidase, indicating that transfer of beta-glucuronidase of donor origin to the lysosomal compartment of parenchymal cells might at least partly be responsible for the observed decrease in storage of glycosaminoglycans in these cells.