TRANSPLANTATION OF POLYMER ENCAPSULATED PC12 CELLS: USE OF CHITOSAN AS AN IMMOBILIZATION MATRIX

Polymer capsules were fabricated to encapsulate PC12 cells within a semipermeable and immunoprotective barrier. The inclusion of precipitated chitosan as an immobilization matrix within the polymer capsules increased the survival and physiological functioning of the PC12 cells. In an initial study, HPLC analysis revealed that the inclusion of a chitosan matrix resulted in an increased output of catecholamines from the encapsulated PC12 cells under both basal conditions, and following high potassium depolarization at 2 and 4 wk following encapsulation in vitro. Furthermore, implantation of cohort PC12 cell-loaded capsules into guinea pig striata revealed that chitosan enhanced PC 12 cell survival after 6 wk. A second study determined that 12 wk after implantation into guinea pig striatum, abundant tyrosine hydroxylase-positive PC12 cells were evenly distributed within capsules containing chitosan. The long-term biocompatibility of these implants was good as determined by the absence of inflammatory or immune cells, and minimal GFAP reactivity surrounding the implant site. In contrast, implantation of unencapsulated PC12 cells resulted in a marked host tissue reaction, and destruction of the implanted cells within 4 wk. It is concluded that the inclusion of precipitated chitosan as an immobilization matrix enhanced the viability of encapsulated PC12 cells, and that altering the internal milieu of polymeric capsules may represent an effective transplant strategy for ameliorating human diseases characterized by secretory cell dysfunction.