Alginate‐poly‐L‐lysine microcapsule biocompatibility: A novel RT‐PCR method for cytokine gene expression analysis in pericapsular infiltrates

Transplantation of microencapsulated islets of Langerhans is impaired by a pericapsular host reaction that eventually induces graft failure. We are studying the role of cytokines in the pathogenesis of this reaction, using the model of alginate-polylysine microcapsule implantation in rat epididymal fat pads. The objectives were: (1) to develop a method to measure, by semiquantitative PCR, TGF-β1 gene expression in fat pad pericapsular infiltrates, and (2) to use this method to evaluate TGF-β1 gene expression 14 days after microcapsule implantation. TGF-β1 mRNA level was significantly higher in pericapsular infiltrate cells than in nonimplanted tissue cells and saline-injected tissue cells (p < 0.0001 and p < 0.01, respectively). There was no significant difference between the TGF-β1 mRNA levels of the two types of controls (p = 0.0945). These results suggest that TGF-β1 plays a role in the pathogenesis of the pericapsular reaction. The method developed can be used to study the role of other fibrogenic cytokines potentially involved. This will shed light on the mechanisms underlying the pericapsular reaction and will serve as a basis for the development of strategies to control this reaction. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res, 45, 223–230, 1999.