Relationship of Glomerular Basement Membrane Alterations to Epithelial Cell Structure and Clinical Parameters in Alport Syndrome

ABSTRACT

PURPOSE: This study was performed to evaluate the relationship between glomerular basement membrane (GBM) alterations to epithelial cell (EpC) structure and renal function in Alport Syndrome (AS) patients. METHODS: Fifteen patients diagnosed with AS (4-26yrs) were examined. The GBM in AS was categorized as C1) normal, C2) minor alterations (widening of lamina rara interna or externa without lamina densa change), C3) nonspecific splitting of lamina densa, C4) basket-weaving pattern of lamina densa splitting. The length of each GBM portion along the epithelial side was measured on the systematically obtained electron microscopic photographs. Furthermore to obtain an objective assessment of the degree of glomerular EpC foot process change, the number of slit pores along 10 microm of peripheral GBM in each category was obtained. RESULTS: The percentage of normal GBM portion (C1) correlated inversely with daily protein excretion (g/day/m2, P <0.05) and sum of the percentage of abnormal GBM portion (C2+C3+C4) had direct correlation with daily protein excretion (g/day/m2, P <0.05). There were no significant relationships between the percentages of other categories of GBM alterations and creatinine clearance or protein excretion. There were no significant relationships between of creatinine clearance in relation to normal GBM(C1) portion as well as that in relation to sum of the percentage of abnormal GBM portion (C2+C3+C4). GBM abnormality did not correlate with age at biopsy. CONCLUSION: The extent of GBM structural abnormality is related to proteinuria in AS but the epithelial response is uniform even though the GBM ultrastructural lesions are not.