Abstract
Repair of parenchyma by stem/progenitor cells is seen as a possible alternative to cure acute and chronic renal failure in future. To learn about this therapeutic purpose, the formation of nephrons during organ growth is under focus of present research. This process is triggered by numerous morphogenetic interactions between epithelial and mesenchymal cells within the renal stem/progenitor cell niche. Recent data demonstrate that an astonishingly wide interstitial interface separates both types of stem/progenitor cells probably controlling coordinated cell-to-cell communication. Since conventional fixation by glutaraldehyde (GA) does not declare in transmission electron microscopy the spatial separation, improved contrasting procedures were applied. As a consequence, the embryonic cortex of neonatal rabbit kidneys was fixed in solutions containing glutaraldehyde in combination with cupromeronic blue, ruthenium red or tannic acid. To obtain a comparable view to the renal stem/progenitor cell niche, the specimens had to be orientated along the cortico-medullary axis of lining collecting ducts. Analysis of tissue samples fixed with GA, in combination with cupromeronic blue, demonstrates demasked extracellular matrix. Numerous braces of proteoglycans cover, as well, the basal lamina of epithelial stem/progenitor cells as projections of mesenchymal stem/progenitor cells crossing the interstitial interface. Fixation with GA containing ruthenium red or tannic acid illustrates strands of extracellular matrix that originate from the basal lamina of epithelial stem/progenitor cells and line through the interstitial interface. Thus, for the first time, improved contrasting techniques make it possible to analyze in detail a microheterogeneous composition of the interstitial interface within the renal stem/progenitor cell niche.
Highlights
Acute and chronic renal failure in humans are worldwide on an increase, possibly reaching epidemic proportions in the future [1]
The renal stem progenitor cell niche is found in the outer cortex and in close vicinity to the Capsula fibrosa (CF)
Epithelial stem/progenitor cells are enclosed within the collecting duct (CD) ampulla tip, while neighboring mesenchymal stem/progenitor cells are separated by the interstitial interface
Summary
Acute and chronic renal failure in humans are worldwide on an increase, possibly reaching epidemic proportions in the future [1]. The situation is further complicated as renal parenchyma does not derive from a single stem/progenitor cell lineage, but originates by interactions between nephrogenic mesenchymal and epithelial stem/progenitor cells. For avoiding loss of bioactive information one expects that the concentration of secreted morphogenetic molecules is high and that the distance for diffusion is short to reach the target [14] This again implies that a close contact should exists between both kinds of stem/progenitor cells. A remarkable microarchitecture can be recognized, when contained extracellular matrix is demasked by fixation of specimens in glutaraldehyde containing cupromeronic blue, ruthenium red or tannic acid All of these new findings demonstrate that cells within the renal stem/progenitor cell niche are not accidentally distributed, but are kept in a sustainable order. To gather more detailed information about structural compounds of the interstitial interface within the renal stem/progenitor cell niche, the present investigation was performed
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