The role of long-term label-retaining cells in the regeneration of adult mouse kidney after ischemia/reperfusion injury

Abstract

BackgroundLabel-retaining cells (LRCs) have been recognized as rare stem and progenitor-like cells, but their complex biological features in renal repair at the cellular level have never been reported. This study was conducted to evaluate whether LRCs in kidney are indeed renal stem/progenitor cells and to delineate their potential role in kidney regeneration.MethodsWe utilized a long-term pulse chase of 5-bromo-2'-deoxyuridine (BrdU)-labeled cells in C57BL/6J mice to identify renal LRCs. We tracked the precise morphological characteristics and locations of BrdU+LRCs by both immunohistochemistry and immunofluorescence. To examine whether these BrdU+LRCs contribute to the repair of acute kidney injury, we analyzed biological characteristics of BrdU+LRCs in mice after ischemia/reperfusion (I/R) injury.ResultsThe findings revealed that the nuclei of BrdU+ LRCs exhibited different morphological characteristics in normal adult kidneys, including nuclei in pairs or scattered, fragmented or intact, strongly or weakly positive. Only 24.3 ± 1.5 % of BrdU+ LRCs co-expressed with Ki67 and 9.1 ± 1.4 % of BrdU+ LRCs were positive for TUNEL following renal I/R injury. Interestingly, we found that newly regenerated cells formed a niche-like structure and LRCs in pairs tended to locate in this structure, but the number of those LRCs was very low. We found a few scattered LRCs co-expressed Lotus tetragonolobus agglutinin (LTA) in the early phase of injury, suggesting differentiation of those LRCs in mouse kidney.ConclusionsOur findings suggest that LRCs are not a simple type of slow-cycling cells in adult kidneys, indicating a limited role of these cells in the regeneration of I/R injured kidney. Thus, LRCs cannot reliably be considered stem/progenitor cells in the regeneration of adult mouse kidney. When researchers use this technique to study the cellular basis of renal repair, these complex features of renal LRCs and the purity of real stem cells among renal LRCs should be considered.

Phenotypic Analysis of BrdU Label-Retaining Cells during the Maturation of Conducting Airway Epithelium in a Porcine Lung

“…The composition of major epithelial cell types or BrdU-labeled cells in epithelium of a porcine lung was ascertained by following a standard histomorphometric analysis, recently set by the American Thoracic Society (ATS) [ 11 ]. Following the HE staining or immunohistochemistry staining on the serial transverse sections, epithelial cell counts were blindly made on every tenth section and then the cells with cell type-specific staining were counted by three senior technicians under a light microscope.…”

“…While the ciliated, secretory, and columnar cells constitute the primary host defense barrier, basal cells are a subpopulation of proliferating cuboidal-shaped cells that provide the major stem/progenitor cell function from which other airway epithelial cells are derived [ 5 – 9 ]. Submucosal glands (SMGs) in the airway are beneath the epithelium and restricted to the highest reaches of the cartilaginous region of airway, which have been demonstrated as the stem cell niche of the cartilaginous tracheal airway [ 10 , 11 ].…”

“…Encouragingly, pigs have been used as a model for biomedical research and a potential donor of organs for xenotransplantation in human, owing to the similarity between the pigs and human in characteristics of physiology, cell composition, and the structure and size of organs [ 11 , 15 , 16 ]. The anatomy, bronchoscopy such as bronchial tree, lobular division, and blood vessels, and the biomechanical and biochemical characterization of a porcine lung have been previously studied [ 17 ].…”

Gcm1 is involved in cell proliferation and fibrosis during kidney regeneration after ischemia–reperfusion injury

“…6c,d). In addition, we analyzed whether the proliferating cells were tubular or interstitial cells on day 3, which is the point when cell proliferation is considered the most increased after IRI 39,40 . When the number of EdU-positive cells was evaluated by dividing the cells into tubular and interstitial cells, the proliferative capacity with regard to both tubular and interstitial cells was significantly lower in cKO mice than in control mice, and the difference was especially prominent for renal tubular cells (Fig.…”

“…It has been shown that the replacement cells ultimately form normal epithelial cells 48 . Some reports have mentioned that peak cell proliferative capacity is noted 3–4 days after IRI 39,40 . Consistent with the results of previous reports, our results indicate that cell proliferation in control mice increased on day 3 rather than on day 1 after IRI.…”