Overview article: basal lamina of epidermis, muscle fibers, muscle capillaries, and renal tubules: changes with aging and in diabetes mellitus.

Using autopsy material from 14 diabetics and 10 controls (8-84 years old), the authors measured the thickness of basal lamina (BL) in skeletal muscle capillaries, renal tubules, skeletal muscle fibers, and epidermis to determine whether BL accumulation is a generalized phenomenon or limited only to certain anatomic structures. The four structures were selected because earlier experiments in animals have shown that in two (muscle capillaries and renal tubules) BL accumulates as a by-product of cell renewal while in the other two (muscle fibers and epidermis) it does not. In human tissues we found that BL accumulates in muscle capillaries and renal tubules but not in muscle fibers and epidermis, in muscle capillaries and in renal tubules it accumulates in controls and in diabetics as a function of aging, more BL in both anatomic structures accumulates in diabetics than in controls, and the extent of BL accumulation in muscle capillaries and renal tubules does not correlate with duration of diabetes mellitus. In addition to the fact that BL does not accumulate in all anatomic structures in which BL is normally present, the observations indicate that diabetes alone is not responsible for BL accumulation, diabetes exaggerates age-dependent accumulation of BL, and accumulation of BL in man is probably a by-product of cell renewal.