Microcapsules as Bio‐organs for Somatic Gene Therapya

Current human gene therapy relies on genetic modification of the patient's own cells. An alternate non-autologous approach is to use universal cell lines engineered to secrete therapeutic products. Protection with immuno-isolation devices would allow the same recombinant cell line to be used for different patients, thus potentially lowering the cost of treatment. The feasibility of this idea has now been demonstrated in vitro and in vivo. Recombinant gene products with potential therapeutic applications (human growth hormone, factor IX, lysosomal enzymes, adenosine deaminase) have been expressed from genetically modified cells after encapsulation with alginate-poly-L-lysine-alginate or hydroxyethyl methacrylate-methyl methacrylate. We have also demonstrated the feasibility of this idea in vivo. After intraperitoneal implantation, genetically modified mouse Ltk- fibroblasts or C2C12 myoblasts encapsulated in alginate-poly-L-lysine-alginate could deliver recombinant gene products (human growth hormone, human factor IX) to the systemic circulation of mice. The clinical efficacy of this novel approach to gene therapy has now been shown in murine models of human diseases. In the Snell dwarf mice deficient in growth hormone production, implantation of encapsulated mouse myoblasts engineered to secrete mouse growth hormone resulted in increases in body weight, length and organ sizes, some to > 25% above those of the controls. In the Gus/Gus mice suffering from the lysosomal storage disease mucopolysaccharidosis type VII due to deficient beta-glucuronidase, implantation of encapsulated mouse fibroblasts engineered to secrete mouse beta-glucuronidase resulted in delivery of normal levels of the enzyme in the plasma and significant correction of the organ histopathology. Hence, delivery of recombinant gene products through bioartificial devices appears to be a promising strategy for the treatment of genetic diseases.