Figure 5

TEM of the renal stem/progenitor cell niche after fixation in GA and tannic acid. Low (a), higher (b) and high (c) magnifications illustrate the interstitial interface (asterisk) at the tip of a CD ampulla labeled by a cross (+). (a) Low magnification depicts that tannic acid covers as a dense coat the basal lamina of a CD ampulla. Further label lines along cellular protrusions of mesenchymal stem/progenitor cells (arrow). A punctuate pattern of tannic acid is found at the interstitial interface (asterisk). (b) Higher magnification illustrates a discontinuous label pattern at the lamina rara (L.r.; white dot), while the lamina densa (L.d.) and fibroreticularis (L.f.) depict an intense coat of tannic acid label. Further bundles of amorphous extracellular matrix are stained by tannic acid at the interstitial interface. (c) High magnification points out that label after tannic acid staining is not equally distributed but shows dense and less dense concentration. Clear arrow head marks fibers at the lamina fibroreticularis.