Transcriptomic profiling and regulatory pathway modeling in a renal allograft transplantation model

Chronic allograft dysfunction (CAD) following kidney
transplantation is characterized by progressive fibrosis and a
smoldering inflammatory infiltrate. A modified Fischer 344 (RT1lvl)
to Lewis (RT1l) rat renal allograft model was used to study
transcriptomic changes during the initiation and progression of CAD
and to identify potential therapeutic modes of action of treatment
with 13cRA previously shown to limit the development of CAD.
Transcriptomic profiling was performed using Affymetrix DNA arrays
at time points 0, 7, 14 and 56 days after transplantation. The
animal model showed development of significant chronic fibrotic
damage with accompanying inflammatory infiltrate by day 56 after
transplantation. Regulatory pathways were identified by the
Database for Annotation, Visualization, and Integrated Discovery
(DAVID) and modulated, based on the Kyoto Encyclopedia of Genes and
Genomes (KEGG) pathways database. Microarray analysis revealed
dramatic changes in the mRNA expression levels of genes associated
with inflammation and fibrosis, as well as the hedgehog and WNT
pathways, with a gradual increase in the number of differentially
regulated genes during progression of tissue damage. Disease
phenotype, as well as differential regulation of select components
of the hedgehog, canonical WNT and WNT-Ca2+ signaling pathways
could be verified by quantitative PCR (qPCR) and
immunohistochemistry. Treatment with 13cRA, not only attenuated
disease progression, but even reversed early effects of CAD. The
overall effects of the treatment are mediated by a potentially
direct influence on fibrosis and inflammation associated gene
expression, as well as by a specific modulation, observed for
hedgehog and WNT pathway activations. The results identify a series
of potential pathways that may represent therapeutic targets in
chronic allograft dysfunction.