Scanning and transmission electron microscopic studies of normal and diabetic acellular glomerular and retinal microvessel basement membranes

Abstract

Basement membranes (BMs) were first described in the mid-19th century, but they were not isolated and prepared for compositional studies until nearly 100 years later. Early methods of isolation were carried out on renal glomeruli, which were first sub-fractionated from kidney tissues by sieving. BMs were then isolated from the glomeruli by ultrasonic disruption, which, following low speed centrifugation, yielded "purified" but highly fragmented BM material. In an effort to obviate the mechanical damage to BMs produced by ultrasound, a sequential detergent solubilization technique was introduced that resulted in morphologically intact BMs from a variety of tissue sub-fractions. This was highly advantageous because "acellular" BMs produced by the procedure could be examined critically by light and electron microscopic methods. Subsequently, this procedure has been utilized to demonstrate the substructural heterogeneity of vascular and non-vascular BMs from a wide variety of animal species. The current review describes the results of scanning and transmission electron microscopic studies of acellular BMs prepared from renal glomeruli and from the retinal microvessels of the eye. These BMs are of particular interest to basic scientists and clinicians because they are altered in several disease states, most notably diabetes mellitus. An effort is made to point out the implications of glomerular and retinal vessel BM changes to the pathogenesis of diabetic kidney and retinal vessel BM disease.

Retinal Vessel Diameters and the Incidence of Gross Proteinuria and Renal Insufficiency in People With Type 1 Diabetes

“…The association of larger venular diameter with incident gross proteinuria probably and renal insufficiency is consistent with other research that links more severe diabetic retinopathy with basement membrane thickening and changes in glomerular extracellular volume in experimental studies (9) and with incident gross proteinuria and renal failure in our previous analysis in the WESDR (11,12). Our data now suggest that retinal venular dilation, independent of more advanced retinopathy, is also related to the development of nephropathy in people with type 1 diabetes.…”

“…The retinal microcirculation, accessible to direct noninvasive visualization, shares similar physiological and pathological characteristics with the renal microcirculation (7)(8)(9). Previous studies have documented the strong association between advanced stages of diabetic retinal disease (e.g., proliferative retinopathy) and nephropathy (10 -15).…”

The Relationship of Diabetic Retinopathy to Preclinical Diabetic Glomerulopathy Lesions in Type 1 Diabetic Patients

“…Thickening of basement membrane in both retinal and glomerular capillary vessels has been shown in late stages of diabetic retinopathy and nephropathy (9). In 86 patients with type 1 diabetes with more severe disease who were being evaluated for pancreatic transplant alone, all subjects had retinopathy, 70% (60 of 86) of whom had proliferative retinopathy, and 73% (63 of 86) had clinical nephropathy, defined as persistent microalbuminuria or overt proteinuria but without advanced renal insufficiency (GFR Ն102 Ϯ 30 ml ⅐ min Ϫ1 ⅐ 1.73 m Ϫ2 ) (2).…”

“…However, renal anatomical changes, sometimes quite advanced, can also occur in the absence of renal functional abnormalities in patients with type 1 diabetes (5,6). Only a few small studies have examined relationships between the anatomical lesions of retinopathy and nephropathy in patients with diabetes (7)(8)(9)(10). The purpose of this report is to describe the association of severity of retinopathy with histological measures of nephropathy in a well-characterized cohort of normotensive patients with type 1 diabetes with normal renal function.…”

Relationship of Blood Pressure to Retinal Vessel Diameter in Type 1 Diabetes Mellitus

“…Understanding the relation of these drugs to retinal arteriolar narrowing and venular widening is important because the latter are thought to be markers of microvascular changes in the cerebral, coronary, peripheral, and renal circulations, and possibly of pathogenetic processes damaging to other targets of diabetic microvascular injury 4,5,12-20. In this report, we examine the relation of ACEI or ARB treatment and blood pressure to changes in retinal vessel caliber in a randomized controlled clinical trial of normotensive normoalbuminuric (NA) persons with T1DM 21…”