Effect of an immobilization matrix and capsule membrane permeability on the viability of encapsulated HEK cells

The effect of inclusion of an immobilization matrix and the capsule membrane permeability on the viability, metabolic activity, and proliferation of encapsulated HEK cells was investigated in vitro. In the absence of a matrix, a particular transfected HEK cell line formed a single aggregate in the core of the poly(hydroxyethyl methacrylate-co-methyl methacrylate) (HEMA–MMA) capsule, and the number of live cells decreased significantly with the passage of time. In contrast, co-encapsulation with a 1% (w/v) ultralow gelling temperature agarose matrix promoted the proliferation of the encapsulated cells. The initial number of 200 live cells/capsule doubled 14 d after encapsulation and reached a plateau of 500 live cells/capsule 28 d after encapsulation. The agarose matrix provided uniform distribution of the cells within the capsule core giving rise to multiple aggregates upon proliferation. Reduction of the polymer solution concentration, and hence the increase of the permeability of the capsule membrane, did not have an effect on the extent or rate of proliferation of cells co-encapsulated with agarose, and did not improve the viability of cells that were encapsulated without a matrix. These cells (transfected with the cDNA for human hepatic lipase) served as a model as part of a program evaluating the use of encapsulated cells for gene therapy.