Background: Significance of podocyte injury in the progression of diabetic nephropathy is not well-understood. In this study, we examined whether alteration of gap junction protein connexin43 (Cx43) expression in podocytes is associated with the progression of overt diabetic nephropathy.
Methods: We recruited 29 type 2 diabetic patients with overt nephropathy who underwent renal biopsy. Nephrectomized kidney samples obtained from seven subjects with localized neoplasm and biopsy specimens from five patients diagnosed as minor glomerular abnormalities were used as controls. Cx43 staining on paraffin-embedded kidney sections were studied by immunohistochemistry.
Results: In controls, Cx43 was expressed at podocytes in a linear pattern along the glomerular basement membrane. In contrast, downregulation and loss of uniformly linear staining of Cx43 (Cx43 heterogeneity) in podocytes were observed in diabetic nephropathy. Cx43 intensity correlated with current renal function (R = 0.647, P < 0.005), whereas the magnitude of Cx43 heterogeneity correlated well with the degree of future decline in renal function (R = -0.705, P < 0.001).
Conclusions: Alteration of Cx43 expression in podocytes was closely associated with the progression of overt diabetic nephropathy. These results indicate that change in Cx43 expression at podocytes represents a progressive stage in overt diabetic nephropathy and that it may be a convenient way to predict future decline in renal function.