Serum HSP27 is associated with medullary perfusion in kidney allografts

BACKGROUND: Heat shock protein 27 (HSP27) is a small HSP up-regulated in response to stress in the kidney. The relationship between HSP27 and intrarenal oxygenation in patients with native and transplant kidney disease is unknown. METHODS: We compared HSP27 levels, intrarenal oxygenation measured by blood oxygen-level dependent (BOLD) imaging using R(2)* values, and perfusion determined by arterial spin labeling (ASL) magnetic resonance imaging (MRI), between patients with native and transplant kidney disease (n=28). RESULTS: There were no statistical differences in mean age (53.9 vs. 47.1 years), kidney function (63.6 vs. 50.7 ml/min per 1.73 m(2)), mean arterial blood pressure (91.6 vs. 91.1 mm Hg), hematocrit (40.6% vs. 39.3%), diuretic or angiotensin-converting enzyme inhibitor use, serum or urine levels of hydrogen peroxide, nitric oxide, F(2) isoprostanes and HSP27 between native and transplant kidneys. BOLD-MRI studies demonstrated comparable patterns in intrarenal oxygen bioavailability (medullary R(2)* 18.1 vs. 18.3/s and cortical R(2)* 12 vs. 11.7/s, respectively). However, medullary perfusion was significantly lower in transplant kidneys (36.4 vs. 78.7 ml/100 g per minute, p=0.0002). There was a linear relationship between serum HSP27 concentrations and medullary perfusion in kidney allografts (HSP27 concentration [ng/mL] = 0.78 + 0.09 medullary perfusion, R(2)=0.43, p=0.01). CONCLUSIONS: Our study demonstrates that medullary perfusion is significantly lower in kidney allografts compared with native kidneys with comparable renal function. We further noted a direct association between serum HSP27 levels and medullary perfusion after transplantation. Additional studies are needed to examine the role of HSP27 as a biomarker of kidney disease progression.