Quantitative electron microscopic study of capillaries in diabetes mellitus.

A systematic microscopic examination of all elements of the capillary wall was performed on quadriceps muscle biopsies from 9 diabetic patients and 8 controls. The capillary basement membrane (CBM) was markedly thicker in diabetics; it consisted of several lamellae and contained large vacuoles which were never observed in non-diabetic subjects. Large magnifications revealed fibrils in greater number and markedly larger in diameter in diabetics, these accounting for a considerable volume of the CBM and the adventitia and increased diameter and thickness of the capillary wall, without encroaching on the lumen. The intracellular fibrils in pericytes and endothelial cells were also larger and thicker in diabetic subjects. The prevalence of fibrillar material in the vascular disease of diabetes mellitus suggests the importance of research into possible measures to arrest fibril formation.