Atypical Features in Regenerating Tubules Point to a Risk for Implantation of Renal Stem/Progenitor Cells

Stem/progenitor cells are seen as a therapeutic option for repair of diseased renal parenchyma. However, actual data show that survival of implanted stem/progenitor cells is impeded by harmful interstitial environment. To learn about parameters for cell adaptation, renal stem/progenitor cells were mounted in a polyester (POSI-4) interstitium during perfusion culture. Controlled fluid environment was maintained by chemically defined CO2 - independent culture media for 13 days. Cell biological features were then analyzed by immunohistochemistry, while structural details were investigated by advanced fixation of specimens for microscopy. When stem/progenitor cells are kept in Leibovitz’s L-15 Medium or CO2 Independent Medium, spatial development of numerous tubules is observed. Immunolabel for TROMAIII, cingulin and laminin ?1 depicts that a homogenous cell population is contained. Semithin sections of specimens fixed in traditional glutaraldehyde (GA) solution reflect an unobtrusive morphology. In contrast, fixation by GA solution including ruthenium red unveils in tubules a thickened basal lamina. Fixation by GA solution including tannic acid illustrates atypical development of a heterogeneous epithelium consisting of bright and dark cells. Thus, advanced fixation of specimens makes pathological features visible, when regeneration is investigated by renal stem/ progenitor cells. To what extent a comparable risk lurks behind an implantation, has to be elaborated.