CONTINUOUS SYSTEMIC SECRETION OF A LYSOSOMAL-ENZYME BY GENETICALLY-MODIFIED MOUSE SKIN FIBROBLASTS

Lysosomal enzymes secreted or externally supplied into the extracellul ar medium can be internalized by cells and targeted to lysosomes after binding to specific membrane receptors. This process allows for the r eplacement of the missing enzyme activity in deficient cells. Using a retroviral vector, we have introduced the human beta-glucuronidase cDN A into primary mouse skin fibroblasts. The genetically modified cells were then engrafted into neo-organs that had been previously implanted in the peritoneal cavity of syngeneic recipient mice. The hypervascul arized structures, made of collagen and basic fibroblast growth factor -coated synthetic fibers embedded into extracellular matrix gel, allow ed in vivo survival of engrafted fibroblasts that expressed the human beta-glucuronidase cDNA for at least 3 months. The human enzyme was de tected in the liver, lung, and spleen of experimental animals, but bec ame undetectable after removal of the neo-organ. This observation indi cated that the human enzyme was secreted into the serum and then captu red by distant organs. The use of genetically modified fibroblasts imp lanted into neo-organs may, therefore, represent a convenient approach to enzyme replacement therapy in lysosomal storage diseases.