Two-dimensional difference gel electrophoresis urinary proteomic profile in the search of nonimmune chronic allograft dysfunction biomarkers.

INTRODUCTION: Despite advances in therapeutics, graft loss associated with chronic allograft dysfunction (CAD) remains high. Urinary proteomic analysis is a noninvasive method that could be used to detect and evaluate CAD in renal transplant recipients. This study was aimed to establish the normal proteome map of stable transplant patients and to validate the utility of two-dimensional difference gel electrophoresis (2DE-DIGE) in identifying new candidates as urinary biomarkers of CAD. METHODS: Morning spot urine samples that were collected from kidney transplant recipients with biopsy-proven interstitial fibrosis and tubular atrophy (IFTA) stages 0-I-II/III (n=8/group) under immunosuppressive treatment with tacrolimus plus mycophenolate with or without prednisone. 2DE silver staining and mass spectrometry analyses were used to establish the normal proteome map, and 2DE-DIGE and mass spectrometry were used to identify proteins exhibiting differential abundance. RESULTS AND CONCLUSIONS: This study defines the normal proteome of stable renal transplant patients, which is composed of several plasma proteins, as well as of immunologic proteins that are probably specific to transplant recipients. The 2DE-DIGE study showed 19 proteins with differential concentrations, depending on the IFTA histologic score. These 19 proteins could be used as urinary biomarkers of the severity of IFTA in renal transplant recipients.

Mammalian target of rapamycin inhibition prevents glomerular hypertrophy in a model of renal mass reduction.

BACKGROUND: Sirolimus (SRL) is a potent and specific immunosuppressive drug used in organ transplantation, as basic therapy or in combination with calcineurin inhibitors. Although SRL is a nonnephrotoxic drug, many reports have related its use with the development of proteinuria, especially after conversion. Therefore, the aim of this study was to elucidate the interrelation between early and late SRL administration on the development of glomerular hypertrophy and proteinuria in a model of renal mass reduction (RMR). METHODS: Rats underwent 2/3 cryoablation of the left kidney and subsequent right nephrectomy (n=42) or sham operations (n=29). Two weeks before (early study) or 12 weeks after (late study) surgery, SRL or vehicle was administered three times weekly. Creatinine clearance and proteinuria were determined throughout the study, and a complete histologic analysis was performed at the end of the study. RESULTS: Treatment with SRL had no effect on creatinine clearance, independently of the administration time. Four weeks after RMR, a significant increase in proteinuria was observed. Proteinuria was stabilized after early and late SRL administration, whereas vehicle-treated animals showed a further increase in proteinuria. Glomerular hypertrophy was strongly associated with proteinuria, and early SRL introduction prevented glomerular enlargement. The histologic analysis showed less structural damage in the two groups of animals treated with SRL than in the control group. CONCLUSION: Although early SRL introduction blocked glomerular hypertrophy, SRL treatment revealed the potential to halt progression of proteinuria and histologic damage at any time of administration in a model of RMR.

Urine proteomics biomarkers in renal transplantation: an overview.

A major goal of clinical proteomics was to identify biomarkers that can aid in the diagnosis and prognosis of different conditions. These biomarkers will not only assist the clinician in the diagnosis of a disease but they will also give directions as to which therapy may be more appropriate for each patient, thus contributing to the development of personalized medicine. This review discusses the current concepts in urine proteomics aimed at identifying predictive biomarkers that could detect the presence of acute rejection or chronic allograft dysfunction early on and for instance be used to personalize immunosuppressive therapies for kidney transplant patients.

Urine proteomics to detect biomarkers for chronic allograft dysfunction.

Despite optimal immunosuppressive therapy, more than 50% of kidney transplants fail because of chronic allograft dysfunction. A noninvasive means to diagnose chronic allograft dysfunction may allow earlier interventions that could improve graft half-life. In this proof-of-concept study, we used mass spectrometry to analyze differences in the urinary polypeptide patterns of 32 patients with chronic allograft dysfunction (14 with pure interstitial fibrosis and tubular atrophy and 18 with chronic active antibody-mediated rejection) and 18 control subjects (eight stable recipients and 10 healthy control subjects). Unsupervised hierarchical clustering showed good segregation of samples in groups corresponding mainly to the four biomedical conditions. Moreover, the composition of the proteome of the pure interstitial fibrosis and tubular atrophy group differed from that of the chronic active antibody-mediated rejection group, and an independent validation set confirmed these results. The 14 protein ions that best discriminated between these two groups correctly identified 100% of the patients with pure interstitial fibrosis and tubular atrophy and 100% of the patients with chronic active antibody-mediated rejection. In summary, this study establishes a pattern for two histologic lesions associated with distinct graft outcomes and constitutes a first step to designing a specific, noninvasive diagnostic tool for chronic allograft dysfunction.