The renal cortical interstitium: morphological and functional aspects

Abstract

The renal interstitial compartment, situated between basement membranes of epithelia and vessels, contains two contiguous cellular networks. One network is formed by interstitial Wbroblasts, the second one by dendritic cells. Both are in intimate contact with each other. Fibroblasts are interconnected by junctions and connected to basement membranes of vessels and tubules by focal adhesions. Fibroblasts constitute the "skeleton" of the kidney. In the renal cortex, Wbroblasts produce erythropoietin and are distinguished from other interstitial cells by their prominent F-actin cytoskeleton, abundance of rough endoplasmic reticulum, and by ecto-5Ј-nucleotidase expression in their plasma membrane. The resident dendritic cells belong to the mononuclear phagocyte system and fulWl a sentinel function. They are characterized by their expression of MHC class II and CD11c. The central situation of Wbroblasts suggests that signals from tubules, vessels, and inXammatory cells converge in Wbroblasts and elicit an integrated response. Following tubular damage and inXammatory signals Wbroblasts proliferate, change to the myoWbroblast phenotype and increase their collagen production, potentially resulting in renal Wbrosis. The acquisition of a proWbrotic phenotype by Wbroblasts in renal diseases is generally considered a main causal event in the progression of chronic renal failure. However, it might also be seen as a repair process.

Human Nephrosclerosis Triggers a Hypoxia-Related Glomerulopathy

“…Although considerable controversy exists in the literature, cellular plasticity has been reported for renal cells. 71 Tubular cells may change their differentiation during hypoxia, 3,72 and podocytes have also been reported to be capable of undergoing changes of differentiation in vitro. 73,74 We found potential markers for a change of differentiation in the microarray gene expression analysis of glomeruli from NSC, eg, down-regulation of the epithelial marker keratin 1 (q Ͻ 0.01) and up-regulation of the mesenchymal markers S100 calcium binding protein A4 (q Ͻ 0.01) and smooth muscle actin, ␣2 (q Ͻ 0.01) (Supplemental Table S1, see http://ajp.amjpathol.org).…”

The Interface Between Generating Renal Tubules and a Polyester Fleece in Comparison to the Interstitium of the Developing Kidney

“…7b), the interstitial space is of great importance in the healthy kidney. 14 The interstitium consists of extracellular matrix, the surrounding fluid and the interstitial cells. The skeletonal portion contains mainly collagen type III sustaining the three-dimensional structure of the organ.…”

Physiology of the Renal Interstitium

“…Furthermore, medullary fibroblasts often have a stouter appearance and harbor cytoplasmatic lipid droplets (8). However, such ultrastructural analysis revealed little about distinct functions of fibroblast populations (1,2,8,17). Attempts to link ultrastructural appearance to function were followed by studies that aimed to define renal fibroblast populations through use of fibroblast markers.…”

“…This may partially be attributed to the fact that it was long considered the exclusive domain of descriptive ultrastructural research, which implied that the interstitium was mostly a passive tissue that structurally supported the tubular epithelium (1,2). The renal interstitium received increasing interest in the context of kidney abnormalities, when the role of interstitial fibrosis in progression of CKD became obvious (3)(4)(5).…”