MODULATION OF TRANSGENE EXPRESSION IN MESOTHELIAL CELLS BY ACTIVATIONOF AN INDUCIBLE PROMOTER

Background. The efficacy of peritoneal dialysis and its success as a l ong-term treatment depends on the preservation of the integrity of the peritoneal membrane. With increasing time on dialysis, the membrane m ay become compromised resulting in decreased dialysing capacity. We ha ve pursued an innovative strategy, i.e. genetic modification of the me sothelial cell to change the properties of the membrane to potentially improve its dialysing capacity and longevity, and have demonstrated t he feasibility of this approach in a rat model of ex vivo gene transfe r. The potential to regulate transgene expression in this model is exa mined here. Methods. Rat peritoneal mesothelial cells (MCs) were stabl y modified to express human growth hormone (hGH) under control of the heavy metal ion and glucocorticoid-regulatable murine metallothionein- l promoter. The effect of zinc and the synthetic glucocorticoid dexame thasone on hGH expression was analysed in MC clones maintained in cont inuous passage or stationary phase, and in our rat model of ex vivo ge ne transfer. Results. Exposure of these clones to zinc and dexamethaso ne, either singly or in combination, resulted in significant (i.e. 2-2 00-fold) increases in hGH production. Zinc-induced modulation of hGH p roduction was demonstrated in cells in continuous passage and stationa ry culture. Regulation was also demonstrated after ex vivo gene transf er by both the intraperitoneal administration of zinc ions or the syst emic administration of dexamethasone. Conclusions. Our results demonst rate the modulation of transgene expression in MCs in vitro and in viv o, and suggest the potential for the regulation of gene expression in a genetically modified mesothelium that may ultimately be used for the delivery of therapeutic proteins to maintain peritoneal membrane viab ility in the peritoneal dialysis patient.