Ultrastructure of isolated basement membranes in the acellular human renal cortex

Transplant quality human kidneys were sliced (approximately equal to 2 mm thick) and cortical regions further minced to approximately 1 mm3. These samples were treated successively with EDTA and detergents to solubilize cellular materials but leave the extracellular matrix (ECM), including basement membranes (BMs) intact. Resultant acellular cortices bear a remarkable resemblance to their in vivo counterparts. By light microscopy, patent, expanded tubular BM (TBM), peritubular capillary BM (PTCBM) and Bowman's capsule BM (BCBM) are surrounded by a swollen ECM which is occasionally fibrillar. Glomerular BM (GBM) lacks supporting interstitium but nevertheless remains convoluted and does not collapse. At the level of transmission electron microscopy, the diverse morphological characteristics of each BM type are evident. Random thickness measurements (lamina densa only) show that BCBMs are thickest (approximately equal to 2,400 nm) followed by TBMs (approximately equal to 750 nm), GBMs (approximately equal to 335 nm) and PTCBMs (approximately equal to 125 nm). Power transformations to normalize right-sided skew of thickness distribution curves reduce their arithmetic means 3-16%. SEM studies confirm LM and TEM observations that isolated GBMs maintain their free-standing spheroidal shapes and indicate that they may be intrinsically rigid. Moreover, their surface topographical details are preserved. We conclude that the acellular cortex offers a clarified view of renal interstitial morphology and demonstrates structural diversity among major renal BM types. Moreover, it provides a baseline of morphological information on which to assess pathological conditions of renal cortical extracellular matrix.