Hypoxia modulates the undifferentiated phenotype of human renal inner medullary CD133(+) progenitors through Oct4/miR-145 balance
ABSTRACT Low-oxygen tension is an important component of the stem cell microenvironment. In rodents, renal resident stem cells have been described in the papilla, a relatively hypoxic region of the kidney. In the present study, we found that CD133(+) cells, previously described as renal progenitors in the human cortex, were enriched in the renal inner medulla and localized within the Henle's loop and thin limb segments. Once isolated, the CD133(+) cell population expressed renal embryonic and stem-related transcription factors and was able to differentiate into mature renal epithelial cells. When injected subcutaneously in immunodeficient mice within Matrigel, CD133(+) cells generated canalized structures positive for renal specific markers of different nephron segments. Oct4A levels and differentiation potential of papillary CD133(+) cells were higher than those of CD133(+) cells from cortical tubuli. Hypoxia was able to promote the undifferentiated phenotype of CD133(+) progenitors from papilla. Hypoxia stimulated clonogenicity, proliferation, vascular endothelial growth factor synthesis, and expression of CD133 that were in turn reduced by epithelial differentiation with parallel HIF-1α downregulation. In addition, hypoxia downregulated microRNA-145 and promoted the synthesis of Oct4A. Epithelial differentiation increased microRNA-145 and reduced Oct4 level, suggesting a balance between Oct4 and microRNA-145. MicroRNA-145 overexpression in CD133(+) cells induced downrelation of Oct4A at the protein level, inhibited cell proliferation, and stimulated terminal differentiation. This study underlines the role of the hypoxic microenvironment in controlling the proliferation and maintaining a progenitor phenotype and stem/progenitor properties of CD133(+) cells of the nephron. This mechanism may be at the basis of the maintenance of a CD133(+) population in the papillary region and may be involved in renal regeneration after injury.
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ABSTRACT: Experimental models are inevitably a compromise between accurately reproducing a pathological situation and schematically simplifying it, which is intended to provide both relevance and conclusiveness. In-vivo models are very relevant, but multiple cell-types undergoing various changes may hinder the observation of individual molecular events. Here, we describe a method for analyzing and isolating specific cell types from the kidney and studying the phenotype they have acquired in vivo. Using flow cytometry, immunofluorescence, and RT-PCR, we show that our method is suitable for studying and isolating proximal tubular cells with an anti Prominin-1 antibody. Kidneys are subjected to mechanical dissociation followed by flow-cytometry analysis. Hundreds of thousands of proximal tubular cells are then isolated by magnetic separation followed by direct analysis or primary cell culture. Using our method, we detect phenotypic changes in the proximal tubular cells after renal ischemia reperfusion, and we isolate the proximal tubular cells, with a purity over 80%. This method is efficient, quick, simple, and cheap, and should be useful for studying cell-type specific parameters after in vivo experimental studies. It is also a simple method to obtain a specific primary cell culture from any animal strain.BMC Cell Biology 01/2015; 16(1):12. DOI:10.1186/s12860-015-0058-4 · 2.84 Impact Factor
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ABSTRACT: As in several body fluids, urine is a rich reservoir of extracellular vesicles (EVs) directly originating from cells facing the urinary lumen, including differentiated tubular cells, progenitor cells and infiltrating inflammatory cells. Several markers of glomerular and tubular damage, such as WT-1, ATF3 and NGAL, as well as of renal regeneration, such as CD133, have been identified representing an incredible source of information for diagnostic purposes. In addition, urinary extracellular vesicles (uEVs) appear to be involved in the cell-to-cell communication along the nephron, although this aspect needs further elucidation. Finally, uEVs emerge as potential amplifying or limiting factors in renal damage. Vesicles from injured cells may favour fibrosis and disease progression whereas those from cells with regenerative potential appear to promote cell survival. Here, we will discuss the most recent findings of the literature, on the light of the role of EVs in diagnosis and therapy for damage and repair of the renal tissue.02/2015; 8(1):23-30. DOI:10.1093/ckj/sfu136
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ABSTRACT: Acute kidney injury is a serious global health problem and determinant of morbidity and mortality. Recent advancements in the field of stem cell research raise hopes for stem cell-based regenerative approaches to treat acute kidney diseases. In this review, the authors summarized the latest research advances of the adult resident renal progenitor cells (ARPCs) on kidney repair, the role of ARPCs on tubular regeneration after acute kidney injury, the current understanding of the mechanisms related to ARPC activation and modulation, as well as the challenges that remain to be faced.11/2014; 12(6):469-475. DOI:10.1016/S2095-4964(14)60053-4