Urinary Monocyte Chemoattractant Protein-1 (MCP-1) in Renal Transplant Recipients: Implications in Proteinuric Patients

Background: After the first year of transplantation chronic allograft nephropathy is the most important cause of renal graft loss and hypertension and proteinuria occur commonly. In native nephropathies, proteinuria and progression to renal failure are linked and renal tubulo-interstitial fibrosis determines prognosis. Monocyte chemoattractant protein-1 (MCP-1) is a powerful chemokine promoting tubulo-interstitial fibrosis but data are limited in a transplant context. Hence this observational cross-sectional study. Methods: The MAP, 24h urinary creatinine clearance, proteinuria and MCP-1 were measured in 81 renal transplant patients (43 with chronic allograft nephropathy). Most patients were on calcineurin-inhibitor based immunosuppression. Regression analysis was applied and comparisons made with 64 patients with native nephropathies and comparable function. Results: One fifth (18/81) of all renal transplant patients had less than optimally controlled hypertension. Proteinuria was heaviest in non-transplanted patients (average 3.0 g/24h, 0.1-12.2) and the ciclosporin-treated transplant patients (1.2 g/24h, 0.02-6.4). Proteinuria and MCP-1 were positively correlated in all patients (r 0.54, p<0.0001) and r 0.84, p<0.0001 in 19 transplant patients receiving angiotensin-converting enzyme inhibitors. MCP-1 levels were highest in non-transplant and ciclosporin-treated patients; geometric mean (SE), 412.4(1.16) and 314.5(1.21) pg/24h respectively. MCP-1 levels were unrelated to age, MAP, creatinine clearance, or blood ciclosporin or tacrolimus levels. Conclusions: Urinary MCP-1 may be a useful non-invasive marker of chronic graft dysfunction in transplant patients facilitating monitoring of progression and response to treatment even in proteinuric patients.