Quantification of collagen in renal glomeruli isolated from human nondiabetic and diabetic kidneys

Abstract

Previous studies of diabetic renovascular complications have measured morphologic changes in relatively few glomerular vessels by electron microscopy. The present study samples 20,000 to 80,000 glomeruli from each of ten nondiabetic and ten diabetic age and sex-matched subjects. Glomeruli were isolated and fractionated by size with a sieving method. Three samples of glomeruli from each subject were analyzed for size, mass, and hydroxyproline content as an index of basement membrane collagen. Approximately 40 per cent of the glomeruli in each sample were isolated. Glomeruli comprised 94 per cent of the tissue elements present, and 92 per cent of the isolated glomeruli were intact. Diabetic glomeruli are larger than nondiabetic glomeruli (mean diameter ± S.E.M. = 258 ± 10 μ versus 196 ± 6 μ) and heavier (499 ± 63 ng. versus 232 ± 16 ng.). Diabetic glomeruli have greater hydroxyproline content than nondiabetic glomeruli when content is expressed per glomerulus (21.9 ± 3.3 ng. versus 7.1 ± 0.5 ng.) and when expressed per milligram dry weight of glomeruli (44.0 ± 2.4 μg. versus 31.6 ± 1.9 μg.). Glomeruli from diabetics of longest duration show the greatest increases in mass and hydroxyproline values. A pathologist's semiquantitative estimation of diffuse glomerulosclerosis revealed a high correlation between hydroxyproline values and histologic determination of the extent of the renal lesion. These measurements allow quantification of basement membrane collagen and may be used to follow development of diabetic vascular complications.