TTRV30M oligomeric aggregates inhibit proliferation of renal progenitor cells but maintain their capacity to differentiate into podocytes in vitro

Publicado em: The Proceedings of the XIIIth International Symposium on Amyloidosis, May 6-10, 2012, Groningen, The NetherlandsIn Familial Amyloidotic Polyneuropathy, the amyloid deposition of mutant transthyretin TTR V30M can lead to renal complications. An unexplored mechanism is the toxicity of oligomeric TTR aggregates. A subset of renal progenitor cells (RPC) in the adult human kidney can induce regeneration of podocytes and tubular structures of the nephron, which can be critical for preventing irreversible renal failure. We assessed whether RPC are vulnerable, in vitro, to TTRV30M oligomers. RPC proliferation was reduced by 16.3±9.7% and 32.6±6.3% after 48 and 72 hours, respectively, in the presence of the oligomers. However, oligomers did not induce apoptosis or alterations in cell cycle to any significant extent, and did not influence RPC differentiation into podocytes. From this first attempt, we can say that TTRV30M oligomers inhibit RPC proliferation but do not influence their capacity to differentiate into mature podocytes, and thus should not compromise tissue regeneration.FC

Toward the Identification of a “Renopoietic System”?

Chronic kidney disease is a leading cause of mortality and morbidity in Western countries and is estimated to affect 11% of the adult population. The possibility of treatment of chronic kidney disease has been severely impaired by our poor knowledge of the regenerative properties of the kidney. Recent results obtained in humans, together with genetic tagging experiments performed in rodents, demonstrated that the epithelial components of the cortical nephron share a unique progenitor, which can generate podocytes as well as tubular cells. Accordingly, lineage tracing experiments demonstrated that bone marrow-derived interstitial or papillary cells are not involved in the repair of injured adult renal epithelium. In addition, assessment of the markers CD24 and CD133 in adult human kidney as well as genetic tagging in rodents allowed us to identify a hierarchical population of renal progenitors arranged in a precise sequence within Bowman's capsule. The results of all of these studies suggest that the kidney contains a “renopoietic system,” with a progenitor localized at the urinary pole of Bowman's capsule, from where it can initiate the replacement and regeneration of glomerular, as well as tubular, epithelial cells. Knowledge of renal progenitor cell biology may enable a better comprehension of the mechanisms of renal repair as well as more effective targeted therapies for acute and chronic kidney diseases

Essential but differential role for CXCR4 and CXCR7 in the therapeutic homingof human renal progenitor cells

Recently, we have identified a population of renal progenitor cells in human kidneys showing regenerative potential for injured renal tissue of SCID mice. We demonstrate here that among all known chemokine receptors, human renal progenitor cells exhibit high expression of both stromal-derived factor-1 (SDF-1) receptors, CXCR4 and CXCR7. In SCID mice with acute renal failure (ARF), SDF-1 was strongly up-regulated in resident cells surrounding necrotic areas. In the same mice, intravenously injected renal stem/progenitor cells engrafted into injured renal tissue decreased the severity of ARF and prevented renal fibrosis. These beneficial effects were abolished by blocking either CXCR4 or CXCR7, which dramatically reduced the number of engrafting renal progenitor cells. However, although SDF-1–induced migration of renal progenitor cells was only abolished by an anti-CXCR4 antibody, transendothelial migration required the activity of both CXCR4 and CXCR7, with CXCR7 being essential for renal progenitor cell adhesion to endothelial cells. Moreover, CXCR7 but not CXCR4 was responsible for the SDF-1–induced renal progenitor cell survival. Collectively, these findings suggest that CXCR4 and CXCR7 play an essential, but differential, role in the therapeutic homing of human renal progenitor cells in ARF, with important implications for the development of stem cell–based therapies

Enhanced propagation of adult human renal epithelial progenitor cells to improve cell sourcing for tissue‐engineered therapeutic devices for renal diseases

Renal cell therapy employing cells derived from adult renal epithelial cell (REC) progenitors promises to reduce the morbidity of patients with renal insufficiency due to acute renal failure and end stage renal disease. To this end, tissue engineered devices addressing the neglected biologic component of renal replacement therapy are being developed. Because human donor tissue is limited, novel enhanced progenitor cell propagation (EP) techniques have been developed and applied to adult human kidney transplant discards from six donors. Changes include more efficient digestion and the amplification of progenitors prior to terminal epithelial differentiation promoted by contact inhibition and the addition of retinoic acid. Differentiated morphology in EP populations was demonstrated by the ability to form polarized epithelium with tight junctions, apical central cilia and expression of brush border membrane enzymes. Evaluation of lipopolysaccharide stimulated interleukin‐8 secretion and γ –glutamyl transpeptisade activity in EP derived cells was used to confirm therapeutic equivalence to REC obtained using published techniques, which have previously shown efficacy in large animal models and clinical trials. Yield exceeded 10 16 cells/gram cortex from the only kidney obtained due to an anatomical defect, while the average yield from diseased kidneys ranged from 1.1×10 9 to 8.8×10 11 cells/gram cortex, representing an increase of more than 10 doublings over standard methods. Application of the EP protocol to REC expansion has solved the problem of cell sourcing as the limiting factor to the manufacture of cell based therapies targeting renal diseases and may provide a method for autologous device fabrication from core kidney biopsies. Copyright © 2012 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92407/1/term471.pd

Regenerative Medicine Therapies: lessons from the kidney

We focus on three strategies for renal regenerative medicine; administering cells to replace damaged tissue, promoting endogenous regeneration, and growing stem cell-derived organs. Mouse kidney regeneration can be promoted by stem cells injected into the circulation which do not become new kidney tissue but seem to secrete regeneration-promoting humoral factors. This argues against direct replacement but encourages developing pharmacological stimulators of endogenous regeneration. Simple 'kidneys' have been made from stem cells, but there is a large gap between what has been achieved and a useful transplantable organ. Most current work aims to stimulate endogenous regeneration or to grow new organs but much remains to be done; misplaced hype about short-term prospects of regenerative medicine helps neither researchers nor patients

Adult kidney stem/progenitor cells contribute to regeneration through the secretion of trophic factors

Adult kidney stem cells are known to have important roles in renal regeneration after acute kidney injury. Although trophic factors from tissue stem cells have been reported to promote the regeneration of other organs, there is limited number of evidence of this phenomenon in the kidneys. Here, we explored the effects of secreted factors from kidney stem cells. We intraperitoneally administered culture supernatant obtained from adult rat kidney stem/progenitor cells into rat kidney ischemia/reperfusion injury models, and the treatment significantly ameliorated renal tubulointerstitial injury, suppressed tubular cell apoptosis, diminished inflammation and promoted the proliferation of both residual renal cells and immature cells. In vitro, treatment with culture supernatant from kidney stem cells significantly promoted cell proliferation and suppressed cisplatin-induced cell apoptosis in both normal rat kidney cells and kidney stem cells. In addition, treatment with culture supernatant increased the expression of nestin in normal rat kidney cells, suggesting the dedifferentiation of tubular cells into stem-like cells. Analysis of the culture supernatant revealed that it contained a variety of growth factors. Taken together, the results suggest that these factors together lead to renal regeneration. In conclusion, adult kidney stem cells contribute to renal regeneration indirectly through the secretion of regenerative factors

Fresh and cryopreserved, uncultured adipose tissue-derived stem and regenerative cells ameliorate ischemia–reperfusion-induced acute kidney injury

Background. Acute kidney injury (AKI) represents a major clinical problem with high mortality and limited causal treatments. The use of cell therapy has been suggested as a potential modality to improve the course and outcome of AKI

Renal stem cells: fact or science fiction?

The kidney is widely regarded as an organ without regenerative abilities. However, in recent years this dogma has been challenged on the basis of observations of kidney recovery following acute injury, and the identification of renal populations that demonstrate stem cell characteristics in various species. It is currently speculated that the human kidney can regenerate in some contexts, but the mechanisms of renal regeneration remain poorly understood. Numerous controversies surround the potency, behaviour and origins of the cell types that are proposed to perform kidney regeneration. The present review explores the current understanding of renal stem cells and kidney regeneration events, and examines the future challenges in using these insights to create new clinical treatments for kidney disease

Expression of Stem Cell Markers in the Human Fetal Kidney

In the human fetal kidney (HFK) self-renewing stem cells residing in the metanephric mesenchyme (MM)/blastema are induced to form all cell types of the nephron till 34th week of gestation. Definition of useful markers is crucial for the identification of HFK stem cells. Because wilms' tumor, a pediatric renal cancer, initiates from retention of renal stem cells, we hypothesized that surface antigens previously up-regulated in microarrays of both HFK and blastema-enriched stem-like wilms' tumor xenografts (NCAM, ACVRIIB, DLK1/PREF, GPR39, FZD7, FZD2, NTRK2) are likely to be relevant markers. Comprehensive profiling of these putative and of additional stem cell markers (CD34, CD133, c-Kit, CD90, CD105, CD24) in mid-gestation HFK was performed using immunostaining and FACS in conjunction with EpCAM, an epithelial surface marker that is absent from the MM and increases along nephron differentiation and hence can be separated into negative, dim or bright fractions. No marker was specifically localized to the MM. Nevertheless, FZD7 and NTRK2 were preferentially localized to the MM and emerging tubules (<10% of HFK cells) and were mostly present within the EpCAMneg and EpCAMdim fractions, indicating putative stem/progenitor markers. In contrast, single markers such as CD24 and CD133 as well as double-positive CD24+CD133+ cells comprise >50% of HFK cells and predominantly co-express EpCAMbright, indicating they are mostly markers of differentiation. Furthermore, localization of NCAM exclusively in the MM and in its nephron progenitor derivatives but also in stroma and the expression pattern of significantly elevated renal stem/progenitor genes Six2, Wt1, Cited1, and Sall1 in NCAM+EpCAM- and to a lesser extent in NCAM+EpCAM+ fractions confirmed regional identity of cells and assisted us in pinpointing the presence of subpopulations that are putative MM-derived progenitor cells (NCAM+EpCAM+FZD7+), MM stem cells (NCAM+EpCAM-FZD7+) or both (NCAM+FZD7+). These results and concepts provide a framework for developing cell selection strategies for human renal cell-based therapies