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 membran e permeability on the viability, metabolic activity, and proliferation of e ncapsulated HEK cells was investigated in vitro. In the absence of a matrix , a particular transfected HEK cell line formed a single aggregate in the c ore of the poly(hydroxyethyl methacrylate-co-methyl methacrylate) (HEMA-MMA ) capsule, and the number of live cells decreased significantly with the pa ssage of time. In contrast, co-encapsulation with a 1% (w/v) ultralow gelli ng temperature agarose matrix promoted the proliferation of the encapsulate d cells. The initial number of similar to 200 live cells/capsule doubled 14 d after encapsulation and reached a plateau of similar to 500 live cells/c apsule 28 d after encapsulation. The agarose matrix provided uniform distri bution of the cells within the capsule core giving rise to multiple aggrega tes upon proliferation. Reduction of the polymer solution concentration, an d hence the increase of the permeability of the capsule membrane. did not h ave an effect on the extent or rate of proliferation of cells co-encapsulat ed with agarose, and did not improve the viability of cells that were encap sulated 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 o f encapsulated cells for gene therapy. (C) 2000 Elsevier Science Ltd. All r ights reserved.