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A role for platelet-derived growth factor (PDGF) receptor(R) signaling/pathway in the fibrosis of Autosomal Dominant Polycystic Kidney Disease (ADPKD): potential for therapy.
Dr Johanna Donovan Prof Patricia D. Wilson, Dr Jill T. Norman
UCL Centre for Nephrology Royal Free Hospital
Background:
The onset of end-stage renal disease (ESRD) in ADPKD is highly variable. This variability is thought, to be due,at least in part,to the degree of pericystic and interstitial fibrosis. Targeting fibrosis may represent a novel contribution to new therapeutic strategies in ADPKD, however, little is known about the underlying processes. We have previously shown that human ADPKD fibroblasts show increased pro-fibrotic functions including increased proliferation, increased myofibroblast differentiation, increased cell-matrix adhesion, cell spreading and migration as well as increased collagen gel contractility. In detailed studies of growth factor responsiveness, we have also identified PDGF as a potent mediator of ADPKD hyper-proliferation. We hypothesise that PDGFR-mediated signaling may play an important role in ADPKD fibrosis.
Methods:
Primary cultures of fibroblasts from age-matched,adult normal human kidney (NHK) and ADPKD kidneys were subjected to comparative gene expression and functional analyses. Pharmacological inhibition and gene knock-down are being used to evaluate the effects of PDGFR inactivation on pro-fibrotic function including migration. Confluent,serum-starved NHK and ADPKD fibroblast monolayers were scratch-wounded and incubated in serum-containing media in the presence or absence of Mitomycin C (5 ng/ml) and the selective small molecular PDGFR tyrosine kinase inhibitor, Imatinib (0-10M) for 48hrs. Migration of cells into the denuded scratch area was scored by imaging and the % of the denuded area repopulated calculated.
Results:
Gene array analysis showed up-regulation of the PDGF receptors, PDGFR and PDGFR, 4.7-fold and 5-fold, respectively, in ES-ADPKD cells. ES-ADPKD fibroblasts showed accelerated migration compared to NHK fibroblasts: 20% ±7.3 repopulated scratch area in ES-ADPKD compared to 1.6% ±1.6 in NHK fibroblasts. Imatinib showed no toxicity in with NHK and ES-ADPKD fibroblasts. The inhibitor had no effect on NHK fibroblast migration but suppressed migration of ES-ADPKD fibroblasts in a dose-dependent manner. Imatinib, 0.37µM, significantly reduced ES-ADPKD fibroblast migration to levels equivalent to NHK, with maximum inhibition at 1.1µM Imatinib.
Conclusion:
These data suggest inhibition of PDGFR signaling can attenuate the ADPKD fibrotic phenotype and supports small molecule inhibition or genetic manipulation of these receptors as a potential therapeutic approach to slow the progression of ADPKD.