GENE EXPRESSION PROFILES IN CHRONIC ALLOGRAFT NEPHROPATHY (CAN): SELECTION OF MARKERS FOR NON-INVASIVE DIAGNOSIS.Room: Hall C
Valeria Mas, Daniel Maluf, Kellie Archer, Kenneth Yanek, Anne King, Eric Gibney, Robert Fisher, Marc Posner. Surgery, Virginia Commonwealth University, Richmond, VA.
Background: CAN is the main cause of renal allograft loss after 1 yr of transplantation (Tx). Non-invasive assays for detecting early organ damage are crucial for the long-term success of Tx.
Patients and Methods: We evaluated gene expression (Gexp) profiles of kidney tissue from kidney transplant patients (KTP) with CAN (N=12) compared to control allografts (NC) by high-density oligonucleotide microarrays. The robust-multiarray average method was used to estimate probe set (Pset) expression summaries. Average linkage hierarchical clustering was performed. The significance analysis of microarrays method was used to identify Psets significantly differentially expressed while controlling for the false discovery rate (FDR). Five markers resulting from the microarray analysis were tested in urine (Ur) and peripheral blood (PB) samples from the CAN patients (Pts) (collected at the biopsy time) using RT-real time-PCR.
Results: Serum creatinine mean levels were 3.80.2 mg/dL with proteinuria >300 mg/dL. Biopsies were grade 2 or 3 CAN per Banff classification. Hierarchical clustering analysis of the kidney biopsies revealed differential GExp patterns in CAN vs. NC biopsies. Assuming unequal variances between tissues, using an FDR of 0.005, and running all possible permutations (n=220), 634 Psets were identified as being differentially expressed. Up regulated genes were related to fibrosis and extracellular matrix deposition (i.e., MMP9, TGF-). Genes related to immunoglobulin, B cells, T cell receptor, nuclear factor of activated T cells, cytokine receptors, and chemokines receptors were up regulated. VEGF, EGF, EGFR and FGFR2, IGF2 were down regulated in CAN samples compared to NC. Down regulated genes also included genes associated to apoptosis induction and regulation (i.e., BCL2L13, CASP6). Moreover, the mRNA levels of the selected markers from the microarray results (EGF, TGF-, fibronectin, thrombospondin, VEGF) were significantly different in Ur (p=0.04, 0.032, 0.05, 0.02, and 0.045, respectively) but not in PB of the KTP compared to NC Ur samples and in correlation with the microarray results (r=0.83).
Conclusions: Profibrotic growth factors, immune response, and apoptosis regulator genes were found differentially expressed in CAN. Markers resulting from the microarray analysis were found differentially expressed in Ur samples of the CAN Pts and in concordance with the microarray profiles.
Keywords: Gene expression; Kidney transplantation; Rejection
Tuesday, July 25, 2006 12:30 PM
Poster Session: Immune Profiling and Molecular Monitoring (12:30 PM-2:00 PM)