Clinical applications of the quick-freezing and deep-etching method to human diabetic nephropathy

Mesangial expansion and glomerular basement membrane (GBM) thickening were not different between normoalbuminuric (NA) and microalbuminuric (MA) type 2 diabetic patients. The quick-freezing and deep-etching (QF-DE) method allows us to examine three-dimensional ultrastructures of human renal glomeruli in vivo at high resolution. In the present study, the QF-DE method was applied to the renal biopsy from 6 type 2 diabetic patients without definable renal diseases other than diabetic nephropathy. Four patients were NA and the other two were MA. Three control specimens were normal parts in surgically resected kidneys of renal cell carcinoma. Replica membranes were prepared by the QF-DE method as previously described. By the QF-DE method, both GBM middle layer and mesangial matrix (MM) were composed of polygonal meshwork structures. The mesh pores of GBM and MM were more enlarged in size and irregular in shape in NA diabetic patients than those of the controls, and these ultrastructural changes became more obvious in MA patients. The diameters of mesh pores in the diabetic patients were significantly larger than those in the control subjects. In conclusion, the QF-DE method could be applied to needle renal biopsy and the present study has firstly clarified the difference of ultrastructural changes between NA and MA type 2 diabetic patients, which had not been disclosed by the conventional electron microscopy, were revealed by the QF-DE method.