Regeneration of renal proximal tubule cells in primary culture following toxicant injury: Response to growth factors

Growth factors may play an important role in the repair of the renal proximal tubule epithelium following toxic injury. This study investigated the regeneration of rabbit renal proximal tubule cell (RPTC) monolayers following exposure to the nephrotoxicants tert-butylhydroperoxide (TBHP) and 1,2-dichlorovinyl-L-cysteine (DCVC), and the effect of exogenous growth factors on the regeneration process. Confluent monolayers exposed to TBHP or DCVC for 1.5-2 hr were 23 and 43% confluent, respectively, after 24 hr. Confluency increased to 63 and 80% 4 days after TBHP or DCVC exposure, but decreased to 29 and 24% after 8 days. Monolayer DNA content did not increase after TBHP or DCVC exposure; however, monolayer protein/DNA ratio increased above control values after DCVC exposure. Recovery of confluency was not sensitive to RGD-containing peptides that inhibit the binding of integrins to extracellular matrix. Epidermal growth factor (EGF) treatment resulted in complete recovery of confluency, and protein and DNA contents 4-6 days after injury. Unlike EGF, IGF-1 or insulin treatment produced a small increase in confluency following TBHP exposure. These results suggest that hypertrophy following DCVC exposure and migration/spreading after TBHP and DCVC exposure play a partial and temporary role in the regeneration of RPTC monolayers, that in the absence of exogenous growth factors proliferation and complete regeneration of the monolayer does not occur, that toxicants may alter the production of mitogenic factors, and that EGF is a potent and efficacious growth factor in promoting regeneration.