The ultrastructure of human tubulo-interstitial fibrosis

Tubulo-interstitial fibrosis, comprising tubular atrophy, infiltration by inflammatory cells, accumulation of extracellular matrix, and proliferation of mesenchymal cells in the interstitium, is a major characteristic of most progressive chronic renal diseases leading to end-stage renal failure, regardless of cause. All of the ultrastructural characteristics of tubulo-interstitial fibrosis can correlate with clinically defined features of chronic renal dysfunction. The present review illustrates ultrastructural features, emphasising some novel findings, in tubulo-interstitial fibrosis, including widespread expression of actin filaments, fatty degeneration of tubular epithelial cells, presence of cilia, and infiltration of leukocytes into the tubular lumen. The hypothesised development of interstitial myofibroblasts from tubular epithelial cells, and the relationship between tubule injury and capillary abnormality are also discussed.