Efficient morphometric analysis of glomerular mesangium in insulin-dependent diabetic patients with early nephropathy

Abstract

Expansion of the glomerular mesangium at the expense of glomerular capillary filtration surface area is a key mechanism leading to progressive loss of renal function in diabetic nephropathy 11]. Careful, precise analysis of mesangial changes may give information about pathogenesis and prognosis, and provide an index of the efficacy of therapeutic intervention [2, 31. Mesangial volume density (V) is defined as the fractional volume of mesangium relative to its containing glomerular volume. Debate persists as to the most efficient and precise method of assessing mesangial volume fraction. The majority of workers have sampled three or more glomeruli at one randomly selected level within the glomerulus [4—7], but using a single level could predispose to bias in the estimate by sampling peripheral areas of the glomerulus that are unrepresentative of the whole due to the arborization of the mesangium [8]. The observed variation in the estimate of mesangial volume fraction in individual glomeruli from the same patient has led to the development of a sampling regime examining three or more levels from each of three glomeruli, in an attempt to improve precision [9—11]. Such multiple level sampling is laborious, placing great demands on technician time and necessitating additional, expensive electron microscopy. Extra time is also required for morphometric analysis of the micrographs. Using the multiple sampling technique as described by and Gundersen [II], an analysis of the contribution of between patient, between glomerulus and between level variance within each glomerulus to the overall variability in the estimate of