SECRETION OF RECOMBINANT PROTEINS FROM HYDROXYETHYL METHACRYLATE-METHYL METHACRYLATE CAPSULES

Current human gene therapy relies on genetic modification of the patie nt's own cells. An alternate nonautologous approach is to use universa l cell lines engineered to secrete therapeutic products. Protection wi th immunoisolation devices before implantation would allow the use of the same recombinant cell line for treating different patients, thus p otentially lowering the cost of treatment. To study the properties of a mechanically stable synthetic biomaterial, hydroxyethyl methyacrylat e-methyl methacrylate (HEMA-MMA) as the immune-isolation device, we en capsulated recombinant mouse fibroblast cells engineered to secrete pr oducts ranging from 27 to 300 kDa in size (human growth hormone, mouse beta-hexosaminidase and beta-glucuronidase) in the presence or absenc e of the extracellular matrix Matrigel. Both viability and cell number in the microcapsules increased with time after encapsulation and cell morphology indicated viable cell growth, thus showing that the capsul e membrane barrier was compatible with nutrient/waste exchange necessa ry for normal metabolic activity. The intracellular levels of these re combinant gene products were constant throughout the experimental peri od of 22 days in the presence or absence of Matrigel, thus demonstrati ng that the microenvironment did not lead to downregulation of the tra nsgenes. However, the extracellular levels of the gene products secret ed from the cells and trapped within the microcapsules were dependent on the molecular size of the product and presence of Matrigel. With th e 27-kDa human growth hormone, the presence of Matrigel caused its ret ention within this intracapsular space, but its release from the micro capsules to the culture medium was not impeded. With the 120-kDa beta- hexosaminidase or the 300-kDa beta-glucuronidase, they were retained w ithin the microcapsule space regardless of the presence or absence of Matrigel, and their passage from the microcapsules to the media was to tally blocked. In conclusion, the HEMA-MMA microcapsules are supportiv e of recombinant cell growth and maintained their molecular cutoff at similar to 100 kDa. Inclusion of extracellular matrix was unable to im prove cell growth and may impede the exit of some gene products. (C) 1 996 John Wiley & Sons, Inc.