UPTAKE OF ALPHA-(L)-IDURONIDASE PRODUCED BY RETROVIRALLY TRANSDUCED FIBROBLASTS INTO NEURONAL AND GLIAL-CELLS IN-VITRO

The uptake of recombinant alpha-(L)-iduronidase into glial and neurona l cells, produced by retrovirally transduced NIH3T3 fibroblasts, was s tudied. We demonstrate that: (1) neuronal and glial cells take up alph a-(L)-iduronidase released into the medium by retrovirally transduced fibroblasts expressing high levels of alpha-(L)-iduronidase; (2) both glial and neuronal cells express the cation independent mannose-6-phos phate receptor responsible for lysosomal enzyme uptake; and (3) uptake of the lysosomal enzyme can be blocked by excess free mannose-6-phosp hate, but not glucose-6-phosphate. Thus, various brain cells take up a lpha-(L)-iduronidase, possibly through a cation independent mannose-6- phosphate receptor mediated pathway, and this uptake is higher in acti vely dividing or immature brain cells. Consequently, (1) neuronal meta bolism ought to be capable of cross correction by enzyme provided by g enetically engineered and transplanted cells provided by bone marrow t ransplantation (BMT); (2) that BMT could have a more beneficial effect on neurological function if performed as early as possible; and (3) g iven that the uptake mechanism of glial cells has a higher capacity, i t might be easier to target diseases like the leukodystrophies in whic h lysosomal enzymes are needed in glial cells, compared to diseases wh ere lysosomal enzymes ought to be delivered into neurons.