Pre-Transplant recipients’ gene expression profiles in peripheral blood mononuclear cells correlate with the development of delayed graft function in kidney transplantation. Pre-Transplant recipients’ gene expression profiles in peripheral blood mononuclear cells correlate with the development of delayed graft function in kidney transplantation

Delayed graft function (DGF) is associated with a reduced long-term graft survival. Ischemia-reperfusion damage and donors' features have been always considered as key pathogenic factors in this setting. The aim of our study was to evaluate the role of recipients' characteristics in the development of DGF to discover early genomics biomarkers in peripheral blood mononuclear cells (PBMC) in order to identify patients at risk. We prospectively enrolled 932 kidney graft recipients from 466 donors for both kidneys. A total of 226 recipients experienced DGF. Among the 466 donors, 290 couples of recipients both patients presented with early graft function (EGF, group A), 50 couples experienced DGF (group B) and 126 couples of recipients were discordant as one presented DGF and the other promptly recovered graft function (group C). In group C we randomly selected 10 couples of DGF/EGF recipients. Peripheral blood mononuclear cells (PBMC) were harvested before transplantation; their transcriptomic profile was investigated by a microarray approach and microarray results were validated by qPCR in an independent group (DGF n=25; EGF n=25). In the whole study group, DGF was independently associated with both donors’ and recipient’s features. Moreover, group A, B and C presented significant differences in both donors’ and recipients’ characteristics. In group C of patients, DGF was significantly associated with body mass index, dialysis modality and number of mismatches. Two-hundred and seventy-three genes were differentially expressed before transplantation in discordant EGF/DGF patients of group C. Their main biological functions were immune dysfunction and inflammation. Among the differentially expressed genes, we observed a significant increase in the expression of CCR2, the MCP-1 receptor, in DGF patients. CCR-2 and MCP-1 up-regulation was confirmed in an independent cohort of patients. Our results suggest that recipients' clinical and immunological features, potentially modulated by dialysis modality, are associated with the development of DGF independently of donors' features. Overall design: In group C, including couples of discordant recipients from the same donor as one presented DGF and the other promptly recovered graft function, we randomly selected ten EGF/DGF couples for microarray analysis (training group). Twenty ml of whole blood were harvested from the selected patients at the time of transplantation, before the administration of induction therapy. PBMCs were isolated by density separation over a Ficoll-PaqueTM (GE healthcare, Uppsala, Sweden). Total RNA was extracted using the RNeasy Mini Kit (Qiagen AG, Basel, Switzerland) and qualitatively and quantitatively analyzed through Agilent Bioanalyzer (Agilent Technologies, Santa Clara, CA). Only samples with good quality, indicated by a RIN> 8, were used in the microarray experiment. For the microarray experiments, we used the GeneChip® Human Genome U133A oligonucleotide microarray (Affymetrix, Santa Clara, CA) which contains 22,283 gene probe sets, representing 12,357 human genes, plus approximately 3,800 expressed sequence tag clones (ESTs), according to manufacturer’s instructions. We used the default settings of Affymetrix Microarray Suite software version 5 (MAS 5.0; Affymetrix) to calculate scaled gene expression values.