Academic literature on the topic 'Acute Kidney Injury, Tubular Progenitor, Tubular regeneration, Stem Cells'

Renal tubular epithelium has the capacity to regenerate, repair, and reepithelialize in response to a variety of insults. Previous studies with several kidney injury models demonstrated that various growth factors, transcription factors, and extracellular matrices are involved in this process. Surviving tubular cells actively proliferate, migrate, and differentiate in the kidney regeneration process after injury, and some cells express putative stem cell markers or possess stem cell properties. Using fate mapping techniques, bone marrow-derived cells and endothelial progenitor cells have been shown to transdifferentiate into tubular components in vivo or ex vivo. Similarly, it has been demonstrated that, during tubular cell regeneration, several inflammatory cell populations migrate, assemble around tubular cells, and interact with tubular cells during the repair of tubular epithelium. In this review, we describe recent advances in understanding the regeneration mechanisms of renal tubules, particularly the characteristics of various cell populations contributing to tubular regeneration, and highlight the targets for the development of regenerative medicine for treating kidney diseases in humans.

Acute kidney injury (AKI) is a major clinical problem associated with increased morbidity and mortality. Despite intensive research, the clinical outcome remains poor, and apart from supportive therapy, no other specific therapy exists. Furthermore, acute kidney injury increases the risk of developing chronic kidney disease (CKD) and end-stage renal disease. Acute tubular injury accounts for the most common intrinsic cause of AKI. The main site of injury is the proximal tubule due to its high workload and energy demand. Upon injury, an intratubular subpopulation of proximal epithelial cells proliferates and restores the tubular integrity. Nevertheless, despite its strong regenerative capacity, the kidney does not always achieve its former integrity and function and incomplete recovery leads to persistent and progressive CKD. Clinical and experimental data demonstrate sexual differences in renal anatomy, physiology, and susceptibility to renal diseases including but not limited to ischemia-reperfusion injury. Some data suggest the protective role of female sex hormones, whereas others highlight the detrimental effect of male hormones in renal ischemia-reperfusion injury. Although the important role of sex hormones is evident, the exact underlying mechanisms remain to be elucidated. This review focuses on collecting the current knowledge about sexual dimorphism in renal injury and opportunities for therapeutic manipulation, with a focus on resident renal progenitor stem cells as potential novel therapeutic strategies.

The kidney has the capacity for regeneration and repair after a variety of insults. Over the past few decades, factors that promote repair of the injured kidney have been extensively investigated. By using kidney injury animal models, the role of intrinsic and extrinsic growth factors, transcription factors, and extracellular matrix in this process has been examined. The identification of renal stem cells in the adult kidney as well as in the embryonic kidney is an active area of research. Cell populations expressing putative stem cell markers or possessing stem cell properties have been found in the tubules, interstitium, and glomeruli of the normal kidney. Cell therapies with bone marrow-derived hematopoietic stem cells, mesenchymal stem cells, endothelial progenitor cells, and amniotic fluid-derived stem cells have been highly effective for the treatment of acute or chronic renal failure in animals. Embryonic stem cells and induced pluripotent stem cells are also utilized for the construction of artificial kidneys or renal components. In this review, we highlight the advances in regenerative medicine for the kidney from the perspective of renotropic factors, renal stem/progenitor cells, and stem cell therapies and discuss the issues to be solved to realize regenerative therapy for kidney diseases in humans.

AbstractWith few curative treatments for kidney diseases, increasing attention has been paid to regenerative medicine as a new therapeutic option. Recent progress in kidney regeneration using human-induced pluripotent stem cells (hiPSCs) is noteworthy. Based on the knowledge of kidney development, the directed differentiation of hiPSCs into two embryonic kidney progenitors, nephron progenitor cells (NPCs) and ureteric bud (UB), has been established, enabling the generation of nephron and collecting duct organoids. Furthermore, human kidney tissues can be generated from these hiPSC-derived progenitors, in which NPC-derived glomeruli and renal tubules and UB-derived collecting ducts are interconnected. The induced kidney tissues are further vascularized when transplanted into immunodeficient mice. In addition to the kidney reconstruction for use in transplantation, it has been demonstrated that cell therapy using hiPSC-derived NPCs ameliorates acute kidney injury (AKI) in mice. Disease modeling and drug discovery research using disease-specific hiPSCs has also been vigorously conducted for intractable kidney disorders, such as autosomal dominant polycystic kidney disease (ADPKD). In an attempt to address the complications associated with kidney diseases, hiPSC-derived erythropoietin (EPO)-producing cells were successfully generated to discover drugs and develop cell therapy for renal anemia. This review summarizes the current status and future perspectives of developmental biology of kidney and iPSC technology-based regenerative medicine for kidney diseases.

A kidney is an organ with relatively low basal cellular regenerative potential. However, renal cells have a pronounced ability to proliferate after injury, which undermines that the kidney cells are able to regenerate under induced conditions. The majority of studies explain yielded regeneration either by the dedifferentiation of the mature tubular epithelium or by the presence of a resident pool of progenitor cells in the kidney tissue. Whether cells responsible for the regeneration of the kidney initially have progenitor properties or if they obtain a “progenitor phenotype” during dedifferentiation after an injury, still stays the open question. The major stumbling block in resolving the issue is the lack of specific methods for distinguishing between dedifferentiated cells and resident progenitor cells. Transgenic animals, single-cell transcriptomics, and other recent approaches could be powerful tools to solve this problem. This review examines the main mechanisms of kidney regeneration: dedifferentiation of epithelial cells and activation of progenitor cells with special attention to potential niches of kidney progenitor cells. We attempted to give a detailed description of the most controversial topics in this field and ways to resolve these issues.

New and effective treatment for acute kidney injury remains a challenge. Here, we induced mouse hematopoietic stem and progenitor cells (HSPC) to differentiate into cells that partially resemble a renal cell phenotype and tested their therapeutic potential. We sequentially treated HSPC with a combination of protein factors for 1 wk to generate a large number of cells that expressed renal developmentally regulated genes and protein. Cell fate conversion was associated with increased histone acetylation on promoters of renal-related genes. Further treatment of the cells with a histone deacetylase inhibitor improved the efficiency of cell conversion by sixfold. Treated cells formed tubular structures in three-dimensional cultures and were integrated into tubules of embryonic kidney organ cultures. When injected under the renal capsule, they integrated into renal tubules of postischemic kidneys and expressed the epithelial marker E-cadherin. No teratoma formation was detected 2 and 6 mo after cell injection, supporting the safety of using these cells. Furthermore, intravenous injection of the cells into mice with renal ischemic injury improved kidney function and morphology by increasing endogenous renal repair and decreasing tubular cell death. The cells produced biologically effective concentrations of renotrophic factors including VEGF, IGF-1, and HGF to stimulate epithelial proliferation and tubular repair. Our study indicates that hematopoietic stem and progenitor cells can be converted to a large number of renal-like cells within a short period for potential treatment of acute kidney injury.

Introduction. Currently, the possibilities of cell therapy using stem cells for the correction of functional disorders of organs, including kidneys, are being widely investigated. The main mechanism of action of stem cells is considered to be the activation of cellular regeneration and the inhibition of apoptosis by the products of their secretion (secretome), which makes it necessary to study the mechanisms of action of the stem cells secretome. Aim of study. To study the relationship of the nephroprotective effect of the drug, which is a protein-peptide secretom of embryonic brain cells (SESC), with its effect on the regeneration of kidney cells damaged by ischemia and the activity of their apoptosis. Material and methods. Experiments were carried out on 40 mongrel male rats weighing 280-320 g. Acute kidney injury of varying severity was caused by removal of the right kidney and ischemia of the remaining left kidney for 60 minutes or 90 minutes (20 rats per group). In each of these groups, 10 rats were injected daily subcutaneously with SESC at a dose of 0.1 ml/kg (10 injections), and the other 10 rats were not treated. After 3, 7 and 14 days, the ischemic kidney was removed and subjected to histological examination and histochemical determination of the expression of the proliferation marker Ki-67 and the anti-apoptotic protein Bcl-2 in the kidney structures. Results. In the treatment of SESC, up to 20% of hypertrophied renal glomeruli were detected already on the 3rd day in the absence of glomeruli with glomerulosclerosis, whereas in control experiments at this time hypertrophied glomeruli were not detected, and the proportion of glomeruli with signs of glomerulosclerosis was 5-10%. On the 7th and 14th days in both groups, the proportion of hypertrophied glomeruli increased, being compared in the group with 60-minute ischemia, but maintaining higher values in experiments with 90-minute ischemia and SESC therapy compared with the control. Glomeruli with glomerulosclerosis were significantly less frequently detected in the treatment of SESC, regardless of the severity of ischemic damage. At the same time, the expression of Bcl-2 in renal glomerular cells during SESC therapy decreased significantly to a lesser extent than in control experiments, confirming the relationship of inhibition of apoptosis during SESC therapy with inhibition of the development of sclerotic processes. A significant increase in the number of epithelial cells expressing the proliferation marker Ki-67 on the 3rd day, followed by a gradual decrease in their number, was detected in the renal tubules during SESC therapy, whereas in the control an increase in the number of labeled cells occurred only on the 7th and 14th days. With an increase in the severity of ischemic damage, the proliferation-stimulating effect of SESC was prolonged up to 14 days. The proliferative effect of SESC therapy was accompanied by a decrease in damage to the renal tubules, and the percentage of tubules with necrotic epithelium progressively decreased from 3-5% to 0-1% with an increase in the period after the start of therapy (7 and 14 days), indicating epithelial regeneration, while in the control their proportion remained at a higher level. Conclusion. Stimulation of cell proliferation and inhibition of apoptosis of damaged cells play an essential role in the nephroprotective effect of SESC, as in stem cells.

During kidney development, progressively committed progenitor cells give rise to the distinct segments of the nephron, the functional unit of the kidney. Similar segment-committed progenitor cells are thought to be involved in the homeostasis of adult kidney. However, markers for most segment-committed progenitor cells remain to be identified. Here, we evaluate Troy/TNFRSF19 as a segment-committed nephron progenitor cell marker. Troy is expressed in the ureteric bud during embryonic development. During postnatal nephrogenesis, Troy+ cells are present in the cortex and papilla and display an immature tubular phenotype. Tracing of Troy+ cells during nephrogenesis demonstrates that Troy+ cells clonally give rise to tubular structures that persist for up to 2 y after induction. Troy+ cells have a 40-fold higher capacity than Troy− cells to form organoids, which is considered a stem cell property in vitro. In the adult kidney, Troy+ cells are present in the papilla and these cells continue to contribute to collecting duct formation during homeostasis. The number of Troy-derived cells increases after folic acid-induced injury. Our data show that Troy marks a renal stem/progenitor cell population in the developing kidney that in adult kidney contributes to homeostasis, predominantly of the collecting duct, and regeneration.

Renal disease is a major worldwide public health problem that affects one in ten people. Renal failure is caused by the irreversible loss of the structural and functional units of kidney (nephrons) due to acute and chronic injuries. In humans, new nephrons (nephrogenesis) are generated until the 36th week of gestation and no new nephron develops after birth. However, in rodents, nephrogenesis persists until the immediate postnatal period. The postnatal mammalian kidney can partly repair their nephrons. The kidney uses intrarenal and extra-renal cell sources for maintenance and repair. Currently, it is believed that dedifferentiation of surviving tubular epithelial cells and presence of resident stem cells have important roles in kidney repair. Many studies have shown that stem cells obtained from extra-renal sites such as the bone marrow, adipose and skeletal muscle tissues, in addition to umbilical cord and amniotic fluid, have potential therapeutic benefits. This review discusses the main mechanisms of renal regeneration by stem cells after a kidney injury.

Evaluation of tubular regenerative response in AKI-induced trasngenic rodent models. Discovered the existence of a progenitor population scattered in kidney tubule of adut mice devoted to tubular epithelium recovery after ischemic injury.

Acute kidney injury (AKI), regardless of its aetiology, can elicit persistent or permanent kidney tissue changes that are associated with progression to end-stage renal disease and a greater risk of chronic kidney disease (CKD). In other cases, AKI may result in complete repair and restoration of normal kidney function. The pathophysiological mechanisms of renal injury and repair include vascular, tubular, and inflammatory factors. The initial injury phase is characterized by rarefaction of peritubular vessels and engagement of the immune response via Toll-like receptor binding, activation of macrophages, dendritic cells, natural killer cells, and T and B lymphocytes. During the recovery phase, cell adhesion molecules as well as cytokines and chemokines may be instrumental by directing the migration, differentiation, and proliferation of renal epithelial cells; recent data also suggest a critical role of M2 macrophage and regulatory T cell in the recovery period. Other processes contributing to renal regeneration include renal stem cells and the expression of growth hormones and trophic factors. Subtle deviations in the normal repair process can lead to maladaptive fibrotic kidney disease. Further elucidation of these mechanisms will help discover new therapeutic interventions aimed at limiting the extent of AKI and halting its progression to CKD or ESRD.