SYSTEMIC DELIVERY OF A RECOMBINANT PROTEIN BY GENETICALLY-MODIFIED MESOTHELIAL CELLS RESEEDED ON THE PARIETAL PERITONEAL SURFACE

To evaluate the ability of genetically modified peritoneal mesothelial cells to deliver recombinant proteins to the systemic circulation, we used our previously described mesothelial cell-based ex vivo gene the rapy strategy.(1) Rat primary peritoneal mesothelial cells; isolated f rom parietal peritoneum by enzymatic digestion, were stably transfecte d (using strontium phosphate DNA co-precipitation) with the plasmid pS VTKgh to express a secreted reporter gene product, human growth hormon e (hgh). Such hgh-secreting mesothelial were reseeded on the denuded p eritoneal surface of syngeneic recipients and delivery of the reporter gene product to the systemic circulation was monitored by analysis of serum samples for the presence of hgh at various times after mesothel ial cell implantation. Polymerase chain reaction(PCR) analysis demonst rated that the hgh-transfected mesothelial cells repopulated the denud ed areas and remained attached there for at least 12 weeks. Moreover t hese genetically modified mesothelial cells continued to express the r eporter gene product in vivo and secreted hgh in sufficient quantity t o be detected in the systemic circulation (ie statistically significan t amounts of hgh could be measured in the serum of cyclosporine A-trea ted rats for at least 2 months; Mann-Whitney test, P <0.05). Our resul ts demonstrate the successful, sustained, systemic delivery of a recom binant protein by genetically modified peritoneal mesothelial cells fo llowing their reattachment to the peritoneal surface, and suggest the potential of ex vivo mesothelial cell-mediated gene therapy for the tr eatment of inherited or acquired disorders requiring delivery of thera peutic proteins to the circulation.