Microencapsulation of normal and transfected L929 fibroblasts in a HEMA-MMA copolymer

Mouse L929 fibroblasts transfected to express a secreted form of human alka line phosphatase (SEAP) mere encapsulated in similar to 400-mu m poly(hydro xyethyl methacrylate-co-methyl methacrylate) (HEMA-MMA) microcapsules as a baseline for the use of genetically engineered cells in encapsulation thera py. Although incubation of microcapsules with serum-containing medium resul ted in maintaining the number of live encapsulated cells with the passage o f time, incubation in a serum-free medium resulted in a three-fold prolifer ation of the encapsulated cells within a 3-week observation period. Similar to the results for incubation with serum-containing medium, co-encapsulati on with a bovine dermal type I collagen, i.e., the inclusion of a matrix in the core of the capsules, resulted in maintenance of the initial number of live cells with the passage of time. SEAP measurements indicated that the transfected cells not only continued to express the transgene product after encapsulation, but also adapted to the capsule microenvironment to secrete SEAP at progressively larger amounts with the passage of time. However, SE AP expression only occurred when the transfected cells (encapsulated or non -encapsulated) were cultivated in serum-containing medium.