Modulation of transgene expression in mesothelial cells by activation of an inducible promoter.
BACKGROUND
The efficacy of peritoneal dialysis and its success as a long-term treatment depends on the preservation of the integrity of the peritoneal membrane. With increasing time on dialysis, the membrane may become compromised resulting in decreased dialysing capacity. We have pursued an innovative strategy, i.e. genetic modification of the mesothelial cell to change the properties of the membrane to potentially improve its dialysing capacity and longevity, and have demonstrated the feasibility of this approach in a rat model of ex vivo gene transfer. The potential to regulate transgene expression in this model is examined here.


METHODS
Rat peritoneal mesothelial cells (MCs) were stably modified to express human growth hormone (hGH) under control of the heavy metal ion and glucocorticoid-regulatable murine metallothionein-1 promoter. The effect of zinc and the synthetic glucocorticoid dexamethasone on hGH expression was analysed in MC clones maintained in continuous passage or stationary phase, and in our rat model of ex vivo gene transfer.


RESULTS
Exposure of these clones to zinc and dexamethasone, either singly or in combination, resulted in significant (i.e. 2-200-fold) increases in hGH production. Zinc-induced modulation of hGH production was demonstrated in cells in continuous passage and stationary culture. Regulation was also demonstrated after ex vivo gene transfer by both the intraperitoneal administration of zinc ions or the systemic administration of dexamethasone.


CONCLUSIONS
Our results demonstrate the modulation of transgene expression in MCs in vitro and in vivo, 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 viability in the peritoneal dialysis patient.
Hoff
C M
CM
Renal Division Scientific Affairs, Baxter Healthcare Corporation, McGaw Park, IL 60085, USA.
Cusick
J L
JL
Masse
E M
EM
Jackman
R W
RW
Nagy
J A
JA
Shockley
T R
TR
D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D002999:Clone Cells; D017931:DNA Primers / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D018014:Gene Transfer Techniques; D005938:Glucocorticoids / Q000494:pharmacology; D019382:Human Growth Hormone / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D051379:Mice; D010530:Peritoneal Dialysis; D010537:Peritoneum / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000187:drug effects; D051381:Rats; D015032:Zinc / Q000494:pharmacology
D017931:DNA Primers; D005938:Glucocorticoids; D019382:Human Growth Hormone; D003907:Dexamethasone; D015032:Zinc