Noninvasive analyses of kidney injury molecule-1 messenger RNA in kidney transplant recipients with graft dysfunction.

BACKGROUND: Kidney graft fibrosis is a major factor related to chronic loss of kidney function. At present, the finding of fibrosis depends on the analysis of tissue in the renal biopsy, which has important limitations. In this study, we evaluated the messenger mRNA transcription and gene expression of kidney injury molecule-1 (KIM-1) in kidney tissue and in urinary sediment cells of kidney transplant patients with graft dysfunction aiming at the development of techniques that may allow the noninvasive diagnosis of interstitral fibrosis/tubular atrophy (IF/TA). PATIENTS AND METHODS: RNA extracted from cells in tissue and urine of 77 renal transplant patients whose biopsies were classified according to the Banff scheme-2007. Four diagnostic groups were established: (1) acute tubular necrosis (n = 9); (2) acute rejection (n = 49); (3) acute calcineurin inhibitors nephrotoxicity (n = 10); and (4) interstitial fibrosis and tubular atrophy (IFTA, n = 29). Tissue and urine cell RNA was amplified and quantification were made by real-time polymerase chain reactron. Data from the quantification of gene expression are presented as median and 25th to 75th percentiles. RESULTS: Messenger RNA levels of the KIM-1 gene were higher in the biopsies (26.17; 3.38-294.53) and urinary sediment cells (0.09; 0-5.81) of the patients classified as having IF/TA as compared with all others groups. A significant correlation between gene expression in samples of urine and tissue cells was found (P < .01). CONCLUSION: These initial data suggests that KIM-1 gene mRNA quantification can be used as a noninvasive biomarker of IF/TA.

Quantitative analyses of kidney injury molecule-1 messenger RNA in kidney transplant recipients with graft dysfunction.

BACKGROUND: Kidney injury molecule-1 (KIM-1), a type I transmembrane protein that is not expressed in normal renal tissue, shows increased expression in dedifferentiated cells within damaged regions of the proximal tubule. We evaluated mRNA transcription of the KIM-1 gene in renal tissue of kidney transplant patients who were experiencing graft dysfunction searching for an accurate biomarker of kidney graft injury. PATIENTS AND METHODS: mRNA analysis was performed on 59 biopsies from kidney transplant patients who had been classified according to the Banff 1997 scheme. Biopsies were categorized in 5 diagnostic groups: acute tubular necrosis (ATN) with superimposed acute rejection episode (ARE), ATN; ARE; calcineurin inhibitor nephrotoxicity (CIN); or interstitial fibrosis and tubular atrophy (IFTA). Amplified tissue RNA was quantified by real-time polymerase chain reaction. RESULTS: Renal tissue evaluations showed significantly increased KIM-1 mRNA expression as shown by median values, 25-75 percentiles, and averages of the logarithmic transformation: namely, CIN group (50.6; 1.8-285, 1; 1.24) and IFTA group (7.5; 1.26-14.6; 0.62), displayed significant differences (P > .05). In contrast, expression was lower among the ATN (0.47; 0.28-1.06; -0.13); ARE (0.21; 0.11-0.78; -0.45), and ATN+ARE (0.46; 0.06-3.27; -0.25) cohorts. CONCLUSION: These preliminary data suggested that KIM-1 mRNA might be useful biomarker of tubular damage associated with CIN and IFTA.

Association between the presence of anti-HLA antibodies with acute rejection and chronic allograft nephropathy in the first year after kidney transplantation.

The clinical relevance of anti-HLA antibodies following kidney transplantation has been a recent focus of research. Patients who present anti-HLA antibodies in the posttransplantation period have shown higher incidences of acute rejection episodes (ARE) and chronic allograft nephropathy (CAN). The objective of this study was to evaluate the presence of anti-HLA antibodies during the first year after kidney transplantation and their association with the occurrence of ARE and CAN. Eighty-eight kidney transplant recipients were evaluated for the presence of IgG anti-HLA antibodies using an enzyme-linked immunosorbent assay (LAT-M and LAT-1240, One Lambda Inc, Calif, United States). Protocol kidney biopsies were performed in consenting patients. ARE and CAN were diagnosed by clinical, laboratory, and histopathological criteria. Anti-HLA antibodies were observed in 20 (22.7%) patients. At 1 year follow-up, 26.1% presented ARE and 51.2% developed CAN. Nine patients (45%) with antibodies developed ARE as opposed to 20.6% without antibodies and 64.7% developed CAN as opposed to 47.8% of those without antibodies. In the histological analysis, the anti-HLA antibodies were associated with Banff IIA ARE (P = .001) and Banff grade II CAN (P = .012). Routine posttransplantation search for antibodies may identify cases at higher risk for acute and chronic rejection, and perhaps help to tailor the immunosuppressive regimen.

Non-invasive diagnosis of acute rejection in kidney transplants with delayed graft function.

Delayed graft function (DGF) often occurs in kidney transplants from deceased donors. We wanted to provide studies giving more accurate non-invasive tests for acute rejection (AR). Using real-time PCR, we examined the expression of cytolytic molecules such as perforin, granzyme B, and fas-ligand along with serpin proteinase inhibitor-9. We also measured the expression of FOXP3, a characteristic gene of T-regulatory cells known to be involved in AR. These studies were conducted on peripheral blood monocytes, urinary cells, and 48 surveillance kidney biopsies taken from a total of 35 patients with DGF. Of these patients, 20 had a histopathological diagnosis of AR, whereas other 28 had characteristics of acute tubular necrosis (ATN). Expression of cytolytic and apoptotic-associated genes in the biopsy tissue, peripheral blood leukocytes, and urinary cells was significantly higher in patients with AR than that in patients with ATN. Diagnostic parameters associated with FOXP3 gene expression were most accurate in peripheral blood leukocytes and urine cells with sensitivity, specificity, positive and negative predictive values, and accuracy between 94 and 100%. Our study shows that quantification of selected genes in peripheral blood leukocytes and urinary cells from renal transplant patients with DGF may provide a useful and accurate non-invasive diagnosis of AR.