67 Molecular and Cellular Biochemistry 259: 67–70, 2004. © 2004 Kluwer Academic Publishers. Printed in the Netherlands. Evidence of apoptosis in human diabetic kidney Dinender Kumar, 1 Susan Robertson, 4 and Kevin D. Burns 2,3 1 Cardiovascular Research Centre, Department of Medicine, University of Wisconsin, Madison, WI, USA; 2 Departments of Cellular and Molecular Medicine; 3 Medicine, Division of Nephrology, Kidney Research Centre, Ottawa Health Research Institute, University of Ottawa; 4 Department of Laboratory Medicine, Ottawa Hospital, Ottawa, Ontario, Canada Received 9 June 2003; accepted 30 July 2003 Abstract Diabetic nephropathy is characterized by an early period of renal growth with glomerular and tubular cell hypertrophy, but this is followed by progressive glomerulosclerosis and tubulointerstitial fibrosis, associated with loss of renal tissue. We studied whether apoptotic cell death occurs in human diabetic nephropathy. Percutaneous renal biopsy samples were obtained from five patients with diabetic nephropathy who were receiving insulin and/or angiotensin-converting enzyme inhibitor therapy. Apoptosis was determined by the presence of DNA fragmentation, detected by in situ TUNEL staining, and by characteristic features on electron microscopy, such as chromatin condensation. Apoptosis was present in all five biopsy specimens, either in epithelial cells of the proximal or distal tubules, or in endothelial cells or interstitial cells. No apoptosis was detected in cells of the glomeruli. The present study provides evidence for apoptosis in human diabetic kidney, and suggests a role for apoptosis in the gradual loss of renal mass. (Mol Cell Biochem 259: 67–70, 2004) Key words: apoptosis, diabetic kidney, tubulointerstitium, endothelial cell Introduction Diabetic nephropathy is a common cause of chronic renal fail- ure and is characterized by initial hypertrophy of glomerular and tubular epithelial cells, thickening of basement membranes, enhanced renal blood flow and glomerular hyperfiltration [1]. With the passage of time, however, diabetic kidneys undergo progressive loss of mass, associated with the development of glomerulosclerosis and tubulointerstitial fibrosis. This sug- gests that cell death may be accelerated in chronic diabetic nephropathy. Apoptosis is a morphologically distinct, genetically con- trolled type of cell death and involves cell shrinkage, chro- matin condensation and fragmentation of nucleosomal DNA [2]. Apoptosis is only rarely observed in the normal kidney [3], but it has been reported in various experimental kidney disease models such as renal ischemia/reperfusion injury [4], unilateral ureteral obstruction [5], Thy 1.1 glomerulonephritis [6, 7], chronic renal failure [8], glomerular sclerotic lesions of IgA nephropathy, lupus nephritis [9] and mouse diabetic kidneys [10]. In the diabetic rat, apoptosis has been detected in tubular cells, and is prevented by treatment with inhibition of the renin-angiotensin system [11]. To determine if apoptosis is present in human diabetic kidney, we utilized in situ TUNEL assay and electron microscopy to examine kidney biopsy speci- mens from five individuals with diabetic nephropathy. Materials and methods Tissue samples Percutaneous core renal biopsy specimens were done origi- nally for clinical diagnoses from five patients. All patients showed histological evidence of diabetic nephropathy. The specimens were examined further for detection of apoptosis, as described below. Information on the patients’ medical pro- files was obtained by review of the medical records. The study was approved by the Research Ethics Board of the Ottawa Hospital. Address for offprints: K.D. Burns, Division of Nephrology, The Ottawa Hospital and University of Ottawa, 1967 Riverside Dr., Rm. 535, Ottawa, Ontario, Canada, K1H 7W9 (E-mail: kburns@ottawahospital.on.ca)