Bone-marrow-derived cells contribute to glomerular endothelial repair in experimental glomerulonephritis

The unique structural and functional characteristics of glomerular endothelial cell fenestrations and their potential as a therapeutic target in kidney disease

Glomerular endothelial cell (GEnC) fenestrations are a critical component of the glomerular filtration barrier. Their unique nondiaphragmed structure is key to their function in glomerular hydraulic permeability, and their aberration in disease can contribute to loss of glomerular filtration function. This review provides a comprehensive update of current understanding of the regulation and biogenesis of fenestrae. We consider diseases in which GEnC fenestration loss is recognized or may play a role and discuss methods with potential to facilitate the study of these critical structures. Literature is drawn from GEnCs as well as other fenestrated cell types such as liver sinusoidal endothelial cells that most closely parallel GEnCs.

Sex-reversal and Histopathological Assessment of Potential Endocrine-Disrupting Effects of Graphene Oxide on Japanese medaka (Oryzias latipes) Larvae

Sex-ratio is considered as an end point during endocrine disrupting chemicals (EDCs) evaluation. Many fish species including Japanese medaka have XX/XY sex determination mechanism, however, sex reversal (SR) can be induced by external and genetic factors. SR imposed an imbalance in natural sex ratio of a population living in any ecosystem. Considering SR as an end point, we aimed to investigate the potential EDC effects of graphene oxide (GO), a nanocarbon, using Japanese medaka as a model. One-day post-hatch (dph) medaka fries were exposed to GO (2.5, 5.0, 10.0 and 20 mg/L) for 96 h without food, followed by 6 weeks depuration in a GO-free environment with feeding. Phenotypic sex was determined by gonad histology; genotypic sex by genotyping Y-chromosome-specific male sex determining gene, dmy. Our data indicated testes in both XY and XX genotypes, while ovaries were only in XX females. Histopathology of XY and XX testis showed isogenic spermatocysts with active spermatogenesis. Distribution of spermatocytes (SPTs), not the spermatogonium (SPGs), showed enhancement in XY than XX testis. Female phenotypes had single ovary, either in stage 0 or 1. Ovo-testis/testis-ova were absent in XX or XY gonads. GO (2.5-20 mg/L) had inconsistent concentration-dependent effect in both SPGs and SPTs; however, no effect on ovarian follicles. Despite genotypic differences (XY/XX), in the histopathology/histochemistry of liver and kidneys GO effects was found to be minimum. Taken together, present study showed spontaneous induction of SR in some XX genotypes; however, exposure of fasting fries to GO had no apparent EDC effects.

Extracellular Vesicles Derived from Endothelial Progenitor Cells Protect Human Glomerular Endothelial Cells and Podocytes from Complement- and Cytokine-Mediated Injury

Glomerulonephritis are renal inflammatory processes characterized by increased permeability of the Glomerular Filtration Barrier (GFB) with consequent hematuria and proteinuria. Glomerular endothelial cells (GEC) and podocytes are part of the GFB and contribute to the maintenance of its structural and functional integrity through the release of paracrine mediators. Activation of the complement cascade and pro-inflammatory cytokines (CK) such as Tumor Necrosis Factor α (TNF-α) and Interleukin-6 (IL-6) can alter GFB function, causing acute glomerular injury and progression toward chronic kidney disease. Endothelial Progenitor Cells (EPC) are bone-marrow-derived hematopoietic stem cells circulating in peripheral blood and able to induce angiogenesis and to repair injured endothelium by releasing paracrine mediators including Extracellular Vesicles (EVs), microparticles involved in intercellular communication by transferring proteins, lipids, and genetic material (mRNA, microRNA, lncRNA) to target cells. We have previously demonstrated that EPC-derived EVs activate an angiogenic program in quiescent endothelial cells and renoprotection in different experimental models. The aim of the present study was to evaluate in vitro the protective effect of EPC-derived EVs on GECs and podocytes cultured in detrimental conditions with CKs (TNF-α/IL-6) and the complement protein C5a. EVs were internalized in both GECs and podocytes mainly through a L-selectin-based mechanism. In GECs, EVs enhanced the formation of capillary-like structures and cell migration by modulating gene expression and inducing the release of growth factors such as VEGF-A and HGF. In the presence of CKs, and C5a, EPC-derived EVs protected GECs from apoptosis by decreasing oxidative stress and prevented leukocyte adhesion by inhibiting the expression of adhesion molecules (ICAM-1, VCAM-1, E-selectin). On podocytes, EVs inhibited apoptosis and prevented nephrin shedding induced by CKs and C5a. In a co-culture model of GECs/podocytes that mimicked GFB, EPC-derived EVs protected cell function and permeselectivity from inflammatory-mediated damage. Moreover, RNase pre-treatment of EVs abrogated their protective effects, suggesting the crucial role of RNA transfer from EVs to damaged glomerular cells. In conclusion, EPC-derived EVs preserved GFB integrity from complement- and cytokine-induced damage, suggesting their potential role as therapeutic agents for drug-resistant glomerulonephritis.

Serial intravital imaging captures dynamic and functional endothelial remodeling with single-cell resolution

Endothelial cells are important in the maintenance of healthy blood vessels and in the development of vascular diseases. However, the origin and dynamics of endothelial precursors and remodeling at the single-cell level have been difficult to study in vivo owing to technical limitations. Therefore, we aimed to develop a direct visual approach to track the fate and function of single endothelial cells over several days and weeks in the same vascular bed in vivo using multiphoton microscopy (MPM) of transgenic Cdh5-Confetti mice and the kidney glomerulus as a model. Individual cells of the vascular endothelial lineage were identified and tracked owing to their unique color combination, based on the random expression of cyan/green/yellow/red fluorescent proteins. Experimental hypertension, hyperglycemia, and laser-induced endothelial cell ablation rapidly increased the number of new glomerular endothelial cells that appeared in clusters of the same color, suggesting clonal cell remodeling by local precursors at the vascular pole. Furthermore, intravital MPM allowed the detection of distinct structural and functional alterations of proliferating endothelial cells. No circulating Cdh5-Confetti⁺ cells were found in the renal cortex. Moreover, the heart, lung, and kidneys showed more significant clonal endothelial cell expansion compared with the brain, pancreas, liver, and spleen. In summary, we have demonstrated that serial MPM of Cdh5-Confetti mice in vivo is a powerful technical advance to study endothelial remodeling and repair in the kidney and other organs under physiological and disease conditions.

Stem/progenitor cell in kidney: characteristics, homing, coordination, and maintenance

Renal failure has a high prevalence and is becoming a public health problem worldwide. However, the renal replacement therapies such as dialysis are not yet satisfactory for its multiple complications. While stem/progenitor cell-mediated tissue repair and regenerative medicine show there is light at the end of tunnel. Hence, a better understanding of the characteristics of stem/progenitor cells in kidney and their homing capacity would greatly promote the development of stem cell research and therapy in the kidney field and open a new route to explore new strategies of kidney protection. In this review, we generally summarize the main stem/progenitor cells derived from kidney in situ or originating from the circulation, especially bone marrow. We also elaborate on the kidney-specific microenvironment that allows stem/progenitor cell growth and chemotaxis, and comment on their interaction. Finally, we highlight potential strategies for improving the therapeutic effects of stem/progenitor cell-based therapy. Our review provides important clues to better understand and control the growth of stem cells in kidneys and develop new therapeutic strategies.

Understanding Mesangial Pathobiology in AL-Amyloidosis and Monoclonal Ig Light Chain Deposition Disease

Patients with plasma cell dyscrasias produce free abnormal monoclonal Ig light chains that circulate in the blood stream. Some of them, termed glomerulopathic light chains, interact with the mesangial cells and trigger, in a manner dependent of their structural and physicochemical properties, a sequence of pathological events that results in either light chain–derived (AL) amyloidosis (AL-Am) or light chain deposition disease (LCDD). The mesangial cells play a key role in the pathogenesis of both diseases. The interaction with the pathogenic light chain elicits specific cellular processes, which include apoptosis, phenotype transformation, and secretion of extracellular matrix components and metalloproteinases. Monoclonal light chains associated with AL-Am but not those producing LCDD are avidly endocytosed by mesangial cells and delivered to the mature lysosomal compartment where amyloid fibrils are formed. Light chains from patients with LCDD exert their pathogenic signaling effect at the cell surface of mesangial cells. These events are generic mesangial responses to a variety of adverse stimuli, and they are similar to those characterizing other more frequent glomerulopathies responsible for many cases of end-stage renal disease. The pathophysiologic events that have been elucidated allow to propose future therapeutic approaches aimed at preventing, stopping, ameliorating, or reversing the adverse effects resulting from the interactions between glomerulopathic light chains and mesangium.

Endothelium structure and function in kidney health and disease

The kidney harbours different types of endothelia, each with specific structural and functional characteristics. The glomerular endothelium, which is highly fenestrated and covered by a rich glycocalyx, participates in the sieving properties of the glomerular filtration barrier and in the maintenance of podocyte structure. The microvascular endothelium in peritubular capillaries, which is also fenestrated, transports reabsorbed components and participates in epithelial cell function. The endothelium of large and small vessels supports the renal vasculature. These renal endothelia are protected by regulators of thrombosis, inflammation and complement, but endothelial injury (for example, induced by toxins, antibodies, immune cells or inflammatory cytokines) or defects in factors that provide endothelial protection (for example, regulators of complement or angiogenesis) can lead to acute or chronic renal injury. Moreover, renal endothelial cells can transition towards a mesenchymal phenotype, favouring renal fibrosis and the development of chronic kidney disease. Thus, the renal endothelium is both a target and a driver of kidney and systemic cardiovascular complications. Emerging therapeutic strategies that target the renal endothelium may lead to improved outcomes for both rare and common renal diseases.

Endothelium structure and function in kidney health and disease

The kidney harbours different types of endothelia, each with specific structural and functional characteristics. The glomerular endothelium, which is highly fenestrated and covered by a rich glycocalyx, participates in the sieving properties of the glomerular filtration barrier and in the maintenance of podocyte structure. The microvascular endothelium in peritubular capillaries, which is also fenestrated, transports reabsorbed components and participates in epithelial cell function. The endothelium of large and small vessels supports the renal vasculature. These renal endothelia are protected by regulators of thrombosis, inflammation and complement, but endothelial injury (for example, induced by toxins, antibodies, immune cells or inflammatory cytokines) or defects in factors that provide endothelial protection (for example, regulators of complement or angiogenesis) can lead to acute or chronic renal injury. Moreover, renal endothelial cells can transition towards a mesenchymal phenotype, favouring renal fibrosis and the development of chronic kidney disease. Thus, the renal endothelium is both a target and a driver of kidney and systemic cardiovascular complications. Emerging therapeutic strategies that target the renal endothelium may lead to improved outcomes for both rare and common renal diseases.

A role for bone marrow-derived cells in diabetic nephropathy

Diabetes mellitus causes systemic disorders. We previously demonstrated that diabetic condition forced bone marrow-derived cells (BMDCs) to express TNF-α, leading to the development of diabetic neuropathy in mice. Here, we hypothesized that these abnormal BMDCs are also involved in diabetic nephropathy. To test our hypothesis, mice were irradiated to receive total bone marrow (BM) from the transgenic mice expressing green fluorescent protein before diabetes was induced by streptozotocin. Confocal microscopy showed that the diabetic glomerulus had more BMDCs compared with the nondiabetic glomerulus. Most of these cells exhibited endothelial phenotypes, being negative for several markers, including podocin (a maker of podocyte), α8 integrin (mesangial cell), CD68, and F4/80 (macrophage). Next, the total BM of diabetic mice was transplanted into nondiabetic mice to examine if diabetic BM per se could cause glomerular injury. The recipient mice exhibiting normal glycemia developed albuminuria and mesangial expansion with an increase in capillary area. The number of BMDCs increased in the glomerulus of the recipient mice. These cells were found to exhibit the endothelial phenotype and to express TNF-α. These data suggest that diabetic BMDCs per se could initiate glomerular disease. Finally, eNOS knockout mice were used to examine if residential endothelial injury could attract BMDCs into the glomerulus. However, endothelial dysfunction due to eNOS deficiency failed to attract BMDCs into the glomerulus. In summary, BMDCs may be involved in the development of diabetic nephropathy.-Nobuta, H., Katagi, M., Kume, S., Terashima, T., Araki, S., Maegawa, H., Kojima, H., Nakagawa, T. A role for bone marrow-derived cells in diabetic nephropathy.

Endothelial Progenitor Cells and Kidney Diseases

Endothelial progenitor cells (EPC) are bone marrow derived or tissue-resident cells that play major roles in the maintenance of vascular integrity and repair of endothelial damage. Although EPCs may be capable of directly engrafting and regenerating the endothelium, the most important effects of EPCs seem to be depended on paracrine effects. In recent studies, specific microvesicles and mRNAs have been found to mediate the pro-angiogenic and regenerative effects of EPCs on endothelium. EPC counts have important prognostic implications in cardiovascular diseases (CVD). Uremia and inflammation are associated with lower EPC counts which probably contribute to increased CVD risks in patients with chronic kidney disease. Beneficial effects of the EPC therapies have been shown in studies performed on different models of CVD and kidney diseases such as acute and chronic kidney diseases and glomerulonephritis. However, lack of a clear definition and specific marker of EPCs is the most important problem causing difficulties in interpretation of the results of the studies investigating EPCs.

Application of Muse Cell Therapy for Kidney Diseases

The kidney plays an essential role in the maintenance of homeostasis in healthy individuals, e.g., by regulating the amount of water and concentration of electrolyte in the body. Owing to the structural complexity, renal dysfunction is caused by a myriad of diseases and conditions, and in severe cases, it progresses to end-stage renal disease in which patients require renal replacement therapy, i.e., maintenance dialysis or kidney transplantation. The currently available therapeutic modalities, with the exception of renal transplantation, cannot recover severely deteriorated renal function. Thus, regenerative medicine holds considerable promise as a potential means for developing next-generation renal therapeutics. Mesenchymal stem cell (MSC) transplantation has been investigated in acute kidney injury and chronic kidney disease models, and clinical studies have already been started for some kinds of kidney diseases. However, most of these studies concluded that the main underlying mechanism of therapeutic effect of MSC transplantation was paracrine. Recently, we reported that Muse cell therapy in a murine model of chronic kidney disease resulted in differentiation of intravenously injected Muse cells into glomerular cells after preferential homing to damaged glomerulus and improvement in renal function. The result suggested the potentiality of Muse cell therapy for glomerular regeneration. Muse cells are a promising cell source for regenerative therapy for kidney diseases.

Decellularized scaffold of cryopreserved rat kidney retains its recellularization potential

The multi-cellular nature of renal tissue makes it the most challenging organ for regeneration. Therefore, till date whole organ transplantations remain the definitive treatment for the end stage renal disease (ESRD). The shortage of available organs for the transplantation has, thus, remained a major concern as well as an unsolved problem. In this regard generation of whole organ scaffold through decellularization followed by regeneration of the whole organ by recellularization is being viewed as a potential alternative for generating functional tissues. Despite its growing interest, the optimal processing to achieve functional organ still remains unsolved. The biggest challenge remains is the time line for obtaining kidney. Keeping these facts in mind, we have assessed the effects of cryostorage (3 months) on renal tissue architecture and its potential for decellularization and recellularization in comparison to the freshly isolated kidneys. The light microscopy exploiting different microscopic stains as well as immuno-histochemistry and Scanning electron microscopy (SEM) demonstrated that ECM framework is well retained following kidney cryopreservation. The strength of these structures was reinforced by calculating mechanical stress which confirmed the similarity between the freshly isolated and cryopreserved tissue. The recellularization of these bio-scaffolds, with mesenchymal stem cells quickly repopulated the decellularized structures irrespective of the kidneys status, i.e. freshly isolated or the cryopreserved. The growth pattern employing mesenchymal stem cells demonstrated their equivalent recellularization potential. Based on these observations, it may be concluded that cryopreserved kidneys can be exploited as scaffolds for future development of functional organ.

Stem cell therapy: An emerging modality in glomerular diseases

The kidney has been considered a highly terminally differentiated organ with low proliferative potential and thus unlikely to undergo regeneration. Glomerular disease progresses to end-stage renal disease (ESRD), which requires dialysis or renal transplantation for better quality of life for patients with ESRD. Because of the shortage of implantable kidneys and complications such as immune rejection, septicemia and toxicity of immunosuppression, kidney transplantation remains a challenge. Therapeutic options available for glomerular disease include symptomatic treatment and strategies to delay progression. In an attempt to develop innovative treatments by promoting the limited capability of regeneration and repair after kidney injury and overcome the progressive pathological process that is uncontrolled with conventional treatment modalities, stem cell-based therapy has emerged as novel intervention due to its ability to inhibit inflammation and promote regeneration. Recent developments in cell therapy have demonstrated promising therapeutic outcomes in terms of restoration of renal structure and function. This review focuses on stem cell therapy approaches for the treatment of glomerular disease, including the various cell sources used and recent advances in preclinical and clinical studies.

Characterization of a Fetal Liver Cell Population Endowed with Long-Term Multiorgan Endothelial Reconstitution Potential

Stable reconstitution of vascular endothelial beds upon transplantation of progenitor cells represents an important challenge due to the paucity and generally limited integration/expansion potential of most identified vascular related cell subsets. We previously showed that mouse fetal liver (FL) hemato/vascular cells from day 12 of gestation (E12), expressing the Stem Cell Leukaemia (SCL) gene enhancer transgene (SCL‐PLAP⁺ cells), had robust endothelial engraftment potential when transferred to the blood stream of newborns or adult conditioned recipients, compared to the scarce vascular contribution of adult bone marrow cells. However, the specific SCL‐PLAP⁺ hematopoietic or endothelial cell subset responsible for the long‐term reconstituting endothelial cell (LTR‐EC) activity and its confinement to FL developmental stages remained unknown. Using a busulfan‐treated newborn transplantation model, we show that LTR‐EC activity is restricted to the SCL‐PLAP⁺VE‐cadherin⁺CD45⁻ cell population, devoid of hematopoietic reconstitution activity and largely composed by Lyve1⁺ endothelial‐committed cells. SCL‐PLAP⁺ Ve‐cadherin⁺CD45⁻ cells contributed to the liver sinusoidal endothelium and also to the heart, kidney and lung microvasculature. LTR‐EC activity was detected at different stages of FL development, yet marginal activity was identified in the adult liver, revealing unknown functional differences between fetal and adult liver endothelial/endothelial progenitors. Importantly, the observations that expanding donor‐derived vascular grafts colocalize with proliferating hepatocyte‐like cells and participate in the systemic circulation, support their functional integration into young livers. These findings offer new insights into the engraftment, phonotypical, and developmental characterization of a novel endothelial/endothelial progenitor cell subtype with multiorgan LTR‐EC activity, potentially instrumental for the treatment/genetic correction of vascular diseases. Stem Cells2017;35:507–521

Regeneration and bioengineering of the kidney: current status and future challenges

The prevalence of chronic kidney disease continues to outpace the development of effective treatment strategies. For patients with advanced disease, renal replacement therapies approximate the filtration functions of the kidney at considerable cost and inconvenience, while failing to restore the resorptive and endocrine functions. Allogeneic transplantation remains the only restorative treatment, but donor shortage, surgical morbidity and the need for lifelong immunosuppression significantly limit clinical application. Emerging technologies in the fields of regenerative medicine and tissue engineering strive to address these limitations. We review recent advances in cell-based therapies, primordial allografts, bio-artificial organs and whole-organ bioengineering as they apply to renal regeneration. Collaborative efforts across these fields aim to produce a bioengineered kidney capable of restoring renal function in patients with end-stage disease.

Mesenchymal stem cells, not conditioned medium, contribute to kidney repair after ischemia-reperfusion injury

INTRODUCTION

Studies have shown that stem cells exert their therapeutic effects on acute kidney injury (AKI) through paracrine/endocrine actions. If the protective effect is mediated in an endocrine manner, the injection of the factors that these cells secrete could be effective, but the effect of conditioned medium (CM) remains controversial.

METHODS

In this study, we cultured mesenchymal stem cells (MSCs) and then transplanted them into an ischemia-reperfusion (I/R) injury model. CM was also injected into mice, and the histological changes, level of cell proliferation, loss of peritubular capillaries and anti-inflammatory and anti-apoptotic effects were examined at different time points.

RESULTS

The results showed that MSC infusion improved renal function and histological alterations, leading to significantly reduced mortality. MSC administration also promoted kidney microvasculature repair, attenuated kidney peritubular capillary loss, increased the proliferation of parenchymal cells and decreased CD68-positive macrophage infiltration and apoptotic cells. Although we determined that CM contained proangiogenic factors, including hepatocyte growth factor (HGF), vascular endothelial growth factor-A (VEGF-A) and insulin-like growth factor-1 (IGF-1), no favorable effects were observed during the course of repair.

CONCLUSIONS

Our data show that MSC infusion promotes kidney repair in a variety of ways, including enhancement of the repair of peritubular capillaries and tubular epithelial cells and anti-inflammatory and anti-apoptotic effects. MSCs can secrete high levels of proangiogenic growth factors, but CM results in a nonsignificant improvement, indicating that MSCs play a role in kidney repair through paracrine rather than endocrine mechanisms. These results indicate that MSC infusion is a promising therapeutic strategy for promoting kidney repair after injury.

Stem cell-based cell therapy for glomerulonephritis

Glomerulonephritis (GN), characterized by immune-mediated inflammatory changes in the glomerular, is a common cause of end stage renal disease. Therapeutic options for glomerulonephritis applicable to all cases mainly include symptomatic treatment and strategies to delay progression. In the attempt to yield innovative interventions fostering the limited capability of regeneration of renal tissue after injury and the uncontrolled pathological process by current treatments, stem cell-based therapy has emerged as novel therapy for its ability to inhibit inflammation and promote regeneration. Many basic and clinical studies have been performed that support the ability of various stem cell populations to ameliorate glomerular injury and improve renal function. However, there is a long way before putting stem cell-based therapy into clinical practice. In the present article, we aim to review works performed with respect to the use of stem cell of different origins in GN, and to discuss the potential mechanism of therapeutic effect and the challenges for clinical application of stem cells.

Collecting duct-derived cells display mesenchymal stem cell properties and retain selective in vitro and in vivo epithelial capacity

We previously described a mesenchymal stem cell (MSC)-like population within the adult mouse kidney that displays long-term colony-forming efficiency, clonogenicity, immunosuppression, and panmesodermal potential. Although phenotypically similar to bone marrow (BM)-MSCs, kidney MSC-like cells display a distinct expression profile. FACS sorting from Hoxb7/enhanced green fluorescent protein (GFP) mice identified the collecting duct as a source of kidney MSC-like cells, with these cells undergoing an epithelial-to-mesenchymal transition to form clonogenic, long-term, self-renewing MSC-like cells. Notably, after extensive passage, kidney MSC-like cells selectively integrated into the aquaporin 2-positive medullary collecting duct when microinjected into the kidneys of neonatal mice. No epithelial integration was observed after injection of BM-MSCs. Indeed, kidney MSC-like cells retained a capacity to form epithelial structures in vitro and in vivo, and conditioned media from these cells supported epithelial repair in vitro. To investigate the origin of kidney MSC-like cells, we further examined Hoxb7(+) fractions within the kidney across postnatal development, identifying a neonatal interstitial GFP(lo) (Hoxb7(lo)) population displaying an expression profile intermediate between epithelium and interstitium. Temporal analyses with Wnt4(GCE/+):R26(tdTomato/+) mice revealed evidence for the intercalation of a Wnt4-expressing interstitial population into the neonatal collecting duct, suggesting that such intercalation may represent a normal developmental mechanism giving rise to a distinct collecting duct subpopulation. These results extend previous observations of papillary stem cell activity and collecting duct plasticity and imply a role for such cells in collecting duct formation and, possibly, repair.

Regenerative medicine in urology

Repair and reconstruction of damaged tissues and organs has been a major issue in the medical field. Regenerative medicine and tissue engineering, as rapid evolving technologies, may offer alternative treatments and hope for patients with serious defects and end-stage diseases. Most urologic diseases could benefit from the development of regenerative medicine and tissue engineering. This article discusses the role of cells and materials in regenerative medicine, as well as the status of current role of regenerative medicine for the generation of specific urologic organs.

Hematopoietic microRNA-126 protects against renal ischemia/reperfusion injury by promoting vascular integrity

Ischemia/reperfusion injury (IRI) is a central phenomenon in kidney transplantation and AKI. Integrity of the renal peritubular capillary network is an important limiting factor in the recovery from IRI. MicroRNA-126 (miR-126) facilitates vascular regeneration by functioning as an angiomiR and by modulating mobilization of hematopoietic stem/progenitor cells. We hypothesized that overexpression of miR-126 in the hematopoietic compartment could protect the kidney against IRI via preservation of microvascular integrity. Here, we demonstrate that hematopoietic overexpression of miR-126 increases neovascularization of subcutaneously implanted Matrigel plugs in mice. After renal IRI, mice overexpressing miR-126 displayed a marked decrease in urea levels, weight loss, fibrotic markers, and injury markers (such as kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin). This protective effect was associated with a higher density of the peritubular capillary network in the corticomedullary junction and increased numbers of bone marrow-derived endothelial cells. Hematopoietic overexpression of miR-126 increased the number of circulating Lin(-)/Sca-1(+)/cKit(+) hematopoietic stem and progenitor cells. Additionally, miR-126 overexpression attenuated expression of the chemokine receptor CXCR4 on Lin(-)/Sca-1(+)/cKit(+) cells in the bone marrow and increased renal expression of its ligand stromal cell-derived factor 1, thus favoring mobilization of Lin(-)/Sca-1(+)/cKit(+) cells toward the kidney. Taken together, these results suggest overexpression of miR-126 in the hematopoietic compartment is associated with stromal cell-derived factor 1/CXCR4-dependent vasculogenic progenitor cell mobilization and promotes vascular integrity and supports recovery of the kidney after IRI.

Stem cells and kidney regeneration

Kidney disease is an escalating burden all over the world. In addition to preventing kidney injury, regenerating damaged renal tissue is as important as to retard the progression of chronic kidney disease to end stage renal disease. Although the kidney is a delicate organ and has only limited regenerative capacity compared to the other organs, an increasing understanding of renal development and renal reprogramming has kindled the prospects of regenerative options for kidney disease. Here, we will review the advances in the kidney regeneration including the manipulation of renal tubular cells, fibroblasts, endothelial cells, and macrophages in renal disease. Several types of stem cells, such as bone marrow-derived cells, adipocyte-derived mesenchymal stem cells, embryonic stem cells, and induced pluripotent stem cells are also applied for renal regeneration. Endogenous or lineage reprogrammed renal progenitor cells represent an attractive possibility for differentiation into multiple renal cell types. Angiogenesis can ameliorate hypoxia and renal fibrosis. Based on these studies and knowledge, we hope to innovate more reliable pharmacological or biotechnical methods for kidney regeneration medicine.

Induced autologous stem cell transplantation for treatment of rabbit renal interstitial fibrosis

Introduction

Renal interstitial fibrosis (RIF) is a significant cause of end-stage renal failure. The goal of this study was to characterize the distribution of transplanted induced autologous stem cells in a rabbit model of renal interstitial fibrosis and evaluate its therapeutic efficacy for treatment of renal interstitial fibrosis.

Methods

A rabbit model of renal interstitial fibrosis was established. Autologous fibroblasts were cultured, induced and labeled with green fluorescent protein (GFP). These labeled stem cells were transplanted into the renal artery of model animals at 8 weeks.

Results

Eight weeks following transplantation of induced autologous stem cells, significant reductions (P < 0.05) were observed in serum creatinine (SCr) (14.8 ± 1.9 mmol/L to 10.1 ± 2.1 mmol/L) and blood urea nitrogen (BUN) (119 ± 22 µmol/L to 97 ± 13 µmol/L), indicating improvement in renal function.

Conclusions

We successfully established a rabbit model of renal interstitial fibrosis and demonstrated that transplantation of induced autologous stem cells can repair kidney damage within 8 weeks. The repair occurred by both inhibition of further development of renal interstitial fibrosis and partial reversal of pre-existing renal interstitial fibrosis. These beneficial effects lead to the development of normal tissue structure and improved renal function.

Stem cells: potential and challenges for kidney repair

Renal damage resulting from acute and chronic kidney injury poses an important problem to public health. Currently, patients with end-stage renal disease rely solely on kidney transplantation or dialysis for survival. Emerging therapies aiming to prevent and reverse kidney damage are thus in urgent need. Although the kidney was initially thought to lack the capacity for self-repair, several studies have indicated that this might not be the case; progenitor and stem cells appear to play important roles in kidney repair under various pathological conditions. In this review, we summarize recent findings on the role of progenitor/stem cells on kidney repair as well as discuss their potential as a therapeutic approach for kidney diseases.

Injured kidney endothelium is only marginally repopulated by cells of extrarenal origin

The role of bone marrow marrow-derived cells after kidney endothelial injury is controversial. In this study, we investigated if and to what extent extrarenal cells incorporate into kidney endothelium after acute as well as during chronic endothelial injury. Fischer F-344 wt (wild type) rat kidney grafts were transplanted into R26- hPAP (human placental alkaline phosphatase) transgenic Fischer F-344 recipient rats to allow identification of extrarenal cells by specific antibody staining. A severe model of renal thrombotic microangiopathy was induced via graft perfusion with antiglomerular endothelial cell (GEN) antibody and resulted in eradication of 85% of the glomerular and 69% of the peritubular endothelium (GEN group). At week 4 after injury, renal endothelial healing as well as recovery of the kidney function was seen. Endothelial chimerism was evaluated by double staining for hPAP and endothelial markers RECA-1 or JG-12. Just 0.25% of the glomerular and 0.1% of the peritubular endothelium was recipient derived. In a second experiment, chronic endothelial injury was induced by combination of kidney transplantation with 5/6 nephrectomy (5/6 Nx group). After 14 wk, only 0.86% of the peritubular and 0.05% of the glomerular endothelium was of recipient origin. In summary, despite demonstration of extensive damage and loss as well as excellent regeneration, just a minority of extrarenal cells were incorporated into kidney endothelium in rat models of acute and chronic renal endothelial cell injury. Our results highlight that kidney endothelial regeneration after specific and severe injury is almost exclusively of renal origin.

Healthy bone marrow cells reduce progression of kidney failure better than CKD bone marrow cells in rats with established chronic kidney disease

Chronic kidney disease (CKD) is a major health care problem. New interventions to slow or prevent disease progression are urgently needed. We studied functional and structural effects of infusion of healthy and CKD bone marrow cells (BMCs) in a rat model of established CKD. CKD was induced by 5/6 nephrectomy (SNX) in Lewis rats, and disease progression was accelerated with L-NNA and 6% NaCl diet. Six weeks after SNX, CKD rats received healthy eGFP(+) BMCs, CKD eGFP(+) BMCs, or vehicle by single renal artery injection. Healthy BMCs were functionally effective 6 weeks after administration: glomerular filtration rate (GFR; inulin clearance) (0.48±0.16 vs. 0.26±0.14 ml/min/100 g) and effective renal plasma flow (RPF; PAH clearance) (1.6±0.40 vs. 1.0±0.62 ml/min/100 g) were higher in healthy BMC- versus vehicle-treated rats (both p < 0.05). Systolic blood pressure (SBP) and proteinuria were lower 5 weeks after treatment with healthy BMCs versus vehicle (SBP, 151±13 vs. 186±25 mmHg; proteinuria, 33±20 vs. 59±39 mg/day, both p < 0.05). Glomerular capillary density was increased, and less sclerosis was detected after healthy BMCs (both p < 0.05). Tubulointerstitial inflammation was also decreased after healthy BMCs. eGFP(+) cells were present in the glomeruli and peritubular capillaries of the remnant kidney in all BMC-treated rats. CKD BMCs also reduced SBP, proteinuria, glomerulosclerosis, and tubular atrophy versus vehicle in CKD rats. However, CKD BMC therapy was not functionally effective versus vehicle [GFR: 0.28±0.09 vs. 0.26±0.16 ml/min/100 g (NS), RPF: 1.15±0.36 vs. 0.78±0.44 ml/min/100 g (NS)], and failed to decrease tubulointerstitial inflammation and fibrosis. Single intrarenal injection of healthy BMCs in rats with established CKD slowed progression of the disease, associated with increased glomerular capillary density and less sclerosis, whereas injection of CKD BMCs was less effective.

Kallikrein transduced mesenchymal stem cells protect against anti-GBM disease and lupus nephritis by ameliorating inflammation and oxidative stress

Previously we have shown that kallikreins (klks) play a renoprotective role in nephrotoxic serum induced nephritis. In this study, we have used mesenchymal stem cells (MSCs) as vehicles to deliver klks into the injured kidneys and have measured their therapeutic effect on experimental antibody induced nephritis and lupus nephritis. Human KLK-1 (hKLK1) gene was transduced into murine MSCs using a retroviral vector to generate a stable cell line, hKLK1-MSC, expressing high levels of hKLK1. 129/svj mice subjected to anti-GBM induced nephritis were transplanted with 10⁶ hKLK1-MSCs and hKLK1 expression was confirmed in the kidneys. Compared with vector-MSCs injected mice, the hKLK1-MSCs treated mice showed significantly reduced proteinuria, blood urea nitrogen (BUN) and ameliorated renal pathology. Using the same strategy, we treated lupus-prone B6.Sle1.Sle3 bicongenic mice with hKLK1-MSCs and demonstrated that hKLK1-MSCs delivery also attenuated lupus nephritis. Mechanistically, hKLK1-MSCs reduced macrophage and T-lymphocyte infiltration into the kidney by suppressing the expression of inflammation cytokines. Moreover, hKLK1 transduced MSCs were more resistant to oxidative stress-induced apoptosis. These findings advance genetically modified MSCs as potential gene delivery tools for targeting therapeutic agents to the kidneys in order to modulate inflammation and oxidative stress in lupus nephritis.

A small molecule inhibitor to plasminogen activator inhibitor 1 inhibits macrophage migration

OBJECTIVE

Macrophage (Mϕ) migration rests on the adhesion/detachment between Mϕ surface components and extracellular matrixes, and the contribution of numerous inflammatory disorders. Plasminogen activator inhibitor (PAI)-1, a serine protease inhibitor, influences Mϕ motility through an action distinct from its classical modulation of the plasmin-based fibrinolytic process. We rely here on a small molecule PAI-1 inhibitor (TM5275) to investigate the role of PAI-1 in Mϕ migration in the pathogenesis of renal injury.

APPROACH AND RESULTS

Mϕ migration was inhibited both in vitro and in vivo by TM5275. It was also reduced in T-cell-deficient nude mice, but not in PAI-1-deficient mice. Mϕ migration hinged on the interaction of PAI-1 with low-density lipoprotein receptor-related protein, an interaction prevented by TM5275, but not with vitronectin, urokinase-type plasminogen activator, or tissue-type plasminogen activator. Fed to rats with anti-Thy-1-induced nephritis, TM5275 significantly decreased Mϕ accumulation and ameliorated the progression of renal injury.

CONCLUSIONS

These findings suggest that a small molecule PAI-1 inhibitor represents a novel class of anti-inflammatory agents targeting Mϕ migration by the inhibition of the interaction of PAI-1 with low-density lipoprotein receptor-related protein.

De novo kidney regeneration with stem cells

Recent studies have reported on techniques to mobilize and activate endogenous stem-cells in injured kidneys or to introduce exogenous stem cells for tissue repair. Despite many recent advantages in renal regenerative therapy, chronic kidney disease (CKD) remains a major cause of morbidity and mortality and the number of CKD patients has been increasing. When the sophisticated structure of the kidneys is totally disrupted by end stage renal disease (ESRD), traditional stem cell-based therapy is unable to completely regenerate the damaged tissue. This suggests that whole organ regeneration may be a promising therapeutic approach to alleviate patients with uncured CKD. We summarize here the potential of stem-cell-based therapy for injured tissue repair and de novo whole kidney regeneration. In addition, we describe the hurdles that must be overcome and possible applications of this approach in kidney regeneration.

Mesenchymal stem cells ameliorate postpyelonephritic renal scarring in rats

OBJECTIVE

To evaluate the efficiency of mesenchymal stem cells in ameliorating renal scarring in a rat pyelonephritis model.

METHODS

Three groups each, including 8 Sprague-Dawley rats were formed: Group 1 = sham operated (4 were given mesenchymal stem cells); group 2 = pyelonephritis induced by Escherichia coli; and group 3 = pyelonephritis and mesenchymal stem cells. Rats not given mesenchymal stem cells in group 1 and 4 rats in groups 2 and 3 were sacrificed on the eighth day for evaluation of inflammation, and the remaining rats were sacrificed at the sixth week to determine renal scarring along with migration of mesenchymal stem cells to renal tubules and differentiation to tubular cells expressing aquaporin-1.

RESULTS

Rats in group 3 had lower scores of both acute (8th day) and chronic (6th week) histopathological alterations compared with rats in group 2. By contrast, although rats in group 3 were shown to have mesenchymal stem cells expressing aquaporin-1 in their renal tubules, these cells were not detected in kidney tissue of mesenchymal stem cells-treated sham rats.

CONCLUSION

These results indicate that mesenchymal stem cells migrated to renal tissues and ameliorated renal scarring in this rat model of pyelonephritis.

Human embryonic mesenchymal stem cell-derived conditioned medium rescues kidney function in rats with established chronic kidney disease

Chronic kidney disease (CKD) is a major health care problem, affecting more than 35% of the elderly population worldwide. New interventions to slow or prevent disease progression are urgently needed. Beneficial effects of mesenchymal stem cells (MSC) have been described, however it is unclear whether the MSCs themselves or their secretome is required. We hypothesized that MSC-derived conditioned medium (CM) reduces progression of CKD and studied functional and structural effects in a rat model of established CKD.

CKD was induced by 5/6 nephrectomy (SNX) combined with L-NNA and 6% NaCl diet in Lewis rats. Six weeks after SNX, CKD rats received either 50 µg CM or 50 µg non-CM (NCM) twice daily intravenously for four consecutive days. Six weeks after treatment CM administration was functionally effective: glomerular filtration rate (inulin clearance) and effective renal plasma flow (PAH clearance) were significantly higher in CM vs. NCM-treatment. Systolic blood pressure was lower in CM compared to NCM. Proteinuria tended to be lower after CM. Tubular and glomerular damage were reduced and more glomerular endothelial cells were found after CM. DNA damage repair was increased after CM. MSC-CM derived exosomes, tested in the same experimental setting, showed no protective effect on the kidney. In a rat model of established CKD, we demonstrated that administration of MSC-CM has a long-lasting therapeutic rescue function shown by decreased progression of CKD and reduced hypertension and glomerular injury.

Renal differentiation of amniotic fluid stem cells: perspectives for clinical application and for studies on specific human genetic diseases

BACKGROUND

Owing to growing rates of diabetes, hypertension and the ageing population, the prevalence of end-stage renal disease, developed from earlier stages of chronic kidney disease, and of acute renal failure is dramatically increasing. Dialysis and preferable renal transplantation are widely applied therapies for this incurable condition. However these options are limited because of morbidity, shortage of compatible organs and costs. Therefore, stem cell-based approaches are becoming increasingly accepted as an alternative therapeutic strategy.

DESIGN

This review summarizes the current findings on the nephrogenic potential of amniotic fluid stem (AFS) cells and their putative implications for clinical applications and for studies on specific human genetic diseases.

RESULTS

Since their discovery in 2003, AFS cells have been shown to be pluripotent with the potential to form embryoid bodies. Compared to adult stem cells, induced pluripotent stem cells or embryonic stem cells, AFS cells harbour a variety of advantages, such as their high differentiation and proliferative potential, no need for ectopic induction of pluripotency and no somatic mutations and epigenetic memory of source cells, and no tumourigenic potential and associated ethical controversies, respectively.

CONCLUSIONS

Recently, the results of different independent studies provided evidence that AFS cells could indeed be a powerful tool for renal regenerative medicine.

Kidney injury and cell therapy: Preclinical study

The aim of this study is to show histological and immunofluorescence analysis of renal parenchyma of agoutis affected by gentamicin-induced renal disease after the infusion of bone marrow mononuclear cells (BMMC) stained with Hoechst®. Nine agouti's males were divided into three groups: Test group (TG): renal disease by gentamicin induced (n = 3), cell therapy group (CTG): renal disease by gentamicin induced and BMMC infusion (n = 3), and control group (CG): nonrenal disease and BMMC infusion (n = 3). TG and CTG were submitted to the protocol of renal disease induction using weekly application of gentamicin sulfate for 4 months. CG and CTG received a 1 × 108 BMMC stained with Hoechst and were euthanized for kidney examination 21 days after BMMC injection and samples were collected for histology and immunofluorescence analysis. Histological analysis demonstrated typical interstitial lesions in kidney similarly to human disease, as tubular necrosis, glomerular destruction, atrophy tubular, fibrotic areas, and collagen deposition. We conclude that histological analysis suggest a positive application of agouti's as a model for a gentamicin inducing of kidney disease, beyond the immunofluorescence analysis suggest a significant migration of BMMC to sites of renal injury in CTG.

Podocyte biology in segmental sclerosis and progressive glomerular injury

During the past 2 decades, progress has been made in understanding the biology and mechanisms of podocyte injury and the relationship of these processes to glomerulosclerosis. In addition, studies of human biopsies and animal models have provided insights into the mechanisms of glomerular disease progression and repair. These new developments are critical for establishing better therapeutic guidelines that target specific pathways, which otherwise would lead to irreversible injury.

ACE Inhibition in Anti-Thy1 Glomerulonephritis Limits Proteinuria but Does Not Improve Renal Function and Structural Remodeling

Background/Aims

ACE inhibitor (ACE-I) treatment effectively inhibits proteinuria and ameliorates the course of various renal diseases. In experimental glomerulonephritis, however, angiotensin II (AngII) infusion has also been shown to be renoprotective. We evaluated the long-term (28 days) course of anti-Thy1 glomerulonephritis in animals with suppressed AngII formation by ACE-I treatment.

Methods

Brown Norway rats received perindopril (2.8 mg/kg/day, n = 12), dihydropyridine calcium-antagonist amlodipine (Ca-A; 13 mg/kg/day, n = 6) or were left untreated (n = 14). All animals were monitored for blood pressure, proteinuria, and creatinine clearance after anti-Thy1 injection. Renal histology was assessed at day 7 and 28.

Results

Systolic blood pressure was equally reduced by ACE-I and Ca-A treatment. AngII suppression prevented development of proteinuria, but did not protect against glomerular microaneurysm formation or reduction in creatinine clearance. After resolution of the microaneurysms, animals with suppressed AngII production showed a modest increase in glomerulosclerosis and vasculopathic thickening of intrarenal vessels.

Conclusions

In anti-Thy1 glomerulonephritis, suppression of AngII formation does not protect against the induction of glomerular damage and is associated with mild aggravation of adverse renal fibrotic remodeling. Proteinuria, however, is effectively prevented by ACE-I treatment. Ca-A treatment did not affect the course of glomerulonephritis, indicating that ACE-I effects are blood pressure independent.

Angiotensin receptor blockade attenuates glomerulosclerosis progression by promoting VEGF expression and bone marrow-derived cells recruitment

BACKGROUND

Previous studies have demonstrated that angiotensin Type I receptor blockade (ARB) reduces proteinuria, reverses glomerular injury and glomerulosclerosis in rat models of diabetic nephropathy and glomerulonephritis. However, the cellular and molecular mechanisms are unclear. To investigate the role of cells of the bone marrow (BM) in glomerular repair seen during ARB administration, we induced progressive glomerulosclerosis in enhanced green fluorescent protein BM chimeric rats by a single injection of anti-Thy 1.1 monoclonal antibody, followed by unilateral nephrectomy.

METHODS

Cohorts of rats received valsartan or no treatment from Week 2 to Week 8 after induction of disease. Renal function, urinary protein excretion and histological changes were examined 8 weeks after anti-Thy-1.1 monoclonal antibody injection.

RESULTS

Valsartan administration improved renal function, reduced severity of glomerulosclrosis and markedly reduced mortality. Valsartan administration promoted regeneration of the glomerular tuft, lowered proteinuria and resulted in enhanced vascular endothelial growth factor (VEGF) expression in the cortex and glomerular tuft. In addition, valsartan promoted increased recruitment of BM-derived cells (BMDCs) many of which expressed VEGF and likely contributed directly to glomerular repair. Nearly all BMDCs recruited to the glomerulus expressed the monocyte/macrophage marker CD68.

CONCLUSIONS

In conclusion, the data shows that ARB by valsartan prevents glomerulosclerosis progression by enhancing glomerular capillary repair which is associated with the recruitment of VEGF producing 'reparative' monocytes and macrophages from the BM.

14S,21R-dihydroxy-docosahexaenoic acid treatment enhances mesenchymal stem cell amelioration of renal ischemia/reperfusion injury

Bone marrow mesenchymal stem cells (MSCs) have shown potential to improve treatment of renal failure. The prohealing functions of MSCs have been found to be enhanced by treatment with the lipid mediator, 14S,21R-dihydroxy-docosa4Z,7Z,10Z,12E,16Z,19Z-hexaenoic acid (14S,21R-diHDHA). In this article, using a murine model of renal ischemia/reperfusion (I/R) injury, we found that treatment with 14S,21R-diHDHA enhanced MSC amelioration of renal I/R injury. Treated MSCs more efficiently inhibited I/R-induced elevation of serum creatinine levels, reduced renal tubular cell death, and inhibited infiltration of neutrophils, macrophages, and dendritic cells in kidneys. Conditioned medium from treated MSCs reduced the generation of tumor necrosis factor-α and reactive oxygen species by macrophages under I/R conditions. Infusion of treated MSCs more efficiently reduced I/R-damage to renal histological structures compared with untreated MSCs (injury score: 7.9±0.4 vs. 10.5±0.5). Treated MSCs were resistant to apoptosis in vivo when transplanted under capsules of I/R-injured kidneys (active caspase-3+ MSCs: 4.2%±2.8% vs. 11.7%±2.4% of control) and in vitro when cultured under I/R conditions. Treatment with 14S,21R-diHDHA promoted viability of MSCs through a mechanism involving activation of the phosphoinositide 3-kinase -Akt signaling pathway. Additionally, treatment of MSCs with 14S,21R-diHDHA promoted secretion of renotrophic hepatocyte growth factor and insulin growth factor-1. Similar results were obtained when 14S,21RdiHDHA was used to inhibit apoptosis of human MSCs (hMSCs) and to increase the generation of renotrophic cytokines from hMSCs. These findings provide a lead for new strategies in the treatment of acute kidney injury with MSCs.

Cells derived from young bone marrow alleviate renal aging

Bone marrow-derived stem cells may modulate renal injury, but the effects may depend on the age of the stem cells. Here we investigated whether bone marrow from young mice attenuates renal aging in old mice. We radiated female 12-mo-old 129SvJ mice and reconstituted them with bone marrow cells (BMC) from either 8-wk-old (young-to-old) or 12-mo-old (old-to-old) male mice. Transfer of young BMC resulted in markedly decreased deposition of collagen IV in the mesangium and less β-galactosidase staining, an indicator of cell senescence. These changes paralleled reduced expression of plasminogen activator inhibitor-1 (PAI-1), PDGF-B (PDGF-B), the transdifferentiation marker fibroblast-specific protein-1 (FSP-1), and senescence-associated p16 and p21. Tubulointerstitial and glomerular cells derived from the transplanted BMC did not show β-galactosidase activity, but after 6 mo, there were more FSP-1-expressing bone marrow-derived cells in old-to-old mice compared with young-to-old mice. Young-to-old mice also exhibited higher expression of the anti-aging gene Klotho and less phosphorylation of IGF-1 receptor β. Taken together, these data suggest that young bone marrow-derived cells can alleviate renal aging in old mice. Direct parenchymal reconstitution by stem cells, paracrine effects from adjacent cells, and circulating anti-aging molecules may mediate the aging of the kidney.

Kidney repair and stem cells: a complex and controversial process

Over the last decade, stem cells have been the topic of much debate and investigation for their regenerative potential in the case of renal injury. This review focuses on bone marrow stem cells (BMSC) for renal repair and the potential origins of the controversial results between studies. Some authors have shown that BMSC can differentiate into renal cells and reverse renal dysfunction while others obtained contradictory results. One significant variation between these studies is the choice of BMSC used. According to the literature and our own experience, unfractionated bone marrow cells and hematopoietic stem cells are able to lead to long-term cell tissue engraftment and repair, whereas mesenchymal stem cells have a short-term paracrine effect. Detection of the bone-marrow-derived cells is also an important source of error. However, the major difference between studies is the model of kidney injury used. Two categories of models have to be distinguished: acute and chronic kidney disease. However, variation within these categories also exists. The outcomes of various strategies for BMSC transplantation after injury to the kidney must be compared within a single model and cannot be transposed from one model to another.

Mesenchymal stem cells as a therapeutic approach to glomerular diseases: benefits and risks

Most studies using adult stem cells (ASCs) and progenitor cells as potential therapeutics for kidney disorders have been conducted in models of acute kidney injury, where the damage mainly affects the tubulointerstitium. The results are promising, whereas the underlying mechanisms are still being discussed controversially. Glomerular diseases have not received as much attention. Likely reasons include the often insidious onset, rendering the choice of optimal treatment timing difficult, and the fact that chronic diseases may require long-term therapy. In this mini review, we summarize current strategies in adult stem cell-based therapies for glomerular diseases. In addition, we focus on possible side effects of stem cell administration that have been reported recently, that is, profibrotic actions and maldifferentiation of mesenchymal stem cells.

Endothelial progenitor cells (EPC) in sepsis with acute renal dysfunction (ARD)

Introduction

Sepsis is characterized by systemic microvascular dysfunction. Endothelial progenitor cells (EPCs) are critically involved in maintaining vascular homeostasis under both physiological and pathological conditions. The aim of the present study was to analyze the endothelial progenitor cell system in patients suffering from sepsis with acute renal dysfunction.

Methods

Patients with newly diagnosed sepsis were recruited from the ICU in a nonrandomized prospective manner. Blood samples were obtained within the first 12 hours after the diagnosis of sepsis. For quantifying endothelial progenitor cells (EPCs), CD133⁺/Flk-1⁺ cells were enumerated by cytometric analysis. Analysis of EPC proliferation was performed by a colony-forming units (CFU) assay. Blood concentrations of proangiogenic mediators were measured by ELISA. Acute renal dysfunction was diagnosed according to the Acute Kidney Injury Network (AKIN) criteria. Depending on the overall mean creatinine concentration during the stay at the ICU, patients were either assigned to a 'normal creatinine group' or to a 'high creatinine group'. Survival rates, frequency of dialysis, the simplified acute physiology score (SAPS) II scores, and different laboratory parameters were collected/used for further clinical characterization

Results

Circulating EPCs were significantly higher in all sepsis patients included in the study as opposed to healthy controls. Patients within the 'high creatinine group' showed an even more pronounced EPC increase. In contrast, EPC proliferation was severely affected in sepsis. Neither total circulating EPCs nor EPC proliferation differed between patients requiring dialysis and patients without renal replacement therapy. Cell numbers and cell proliferation also did not differ between surviving patients and patients with sepsis-related death. Serum levels of vascular endothelial growth factor (VEGF), stromal derived factor-1 (SDF-1), and Angiopoietin-2 were higher in sepsis than in healthy controls. Sepsis patients within the 'high creatinine group' showed significantly higher mean serum levels of uric acid.

Conclusions

Sepsis significantly affects the endothelial progenitor cell system, as reflected by increased EPC numbers, increased concentrations of proangiogenic mediators, and reduced proliferative capacity of the cells. This occurs independently from the frequency of dialysis and from patient survival. Increased serum levels of uric acid are possibly responsible for stronger EPC mobilization in sepsis patients with higher average creatinine levels.

The role of graft-versus-host disease in haematopoietic cell transplantation-associated glomerular disease

BACKGROUND

Glomerular disease among haematopoietic cell transplantation recipients has been attributed to chronic graft-versus-host disease. Clinical outcomes of this population may be influenced by the haematopoietic cell transplantation conditioning regimen, donor factors and chronic graft-versus-host disease.

METHODS

In this review, 95 cases of haematopoietic cell transplantation-associated glomerular disease were identified from literature review for analysis. Patient characteristics, the association of chronic graft-versus-host disease with glomerular diseases, and the impact of host and haematopoietic cell transplantation regimen on outcomes were evaluated.

RESULTS

The median onset of glomerular disease from haematopoietic cell transplantation and from cessation of immunosuppressive agents was 15.5 and 1 month, respectively. Although chronic graft-versus-host disease was common among haematopoietic cell transplant recipients with glomerulonephritis (72%), this was no different from that observed in the overall haematopoietic cell transplantation population. Membranous nephropathy and minimal change disease are the most prevalent glomerular diseases among haematopoietic cell transplantation recipients. Chronic graft-versus-host disease, donor factors and haematopoietic cell transplant regimen did not significantly impact outcomes in this study population.

CONCLUSIONS

Pathogenic mechanisms in addition to (or other than) chronic graft-versus-host disease are likely contribute to haematopoietic cell transplantation-associated glomerular disease. Further investigation will be required to delineate clearly the pathogenesis.

Regeneration and the kidney

PURPOSE OF REVIEW

Following any injury, various intracellular and intercellular pathways must be activated and coordinated if tissue integrity and homeostasis need to be restored. In most injuries, repair results in once-functional tissue becoming a patch of cells and disorganized extracellular matrix that is referred to as a scar. However, most adult organs of the body, including the kidney, have the potential to regenerate functional tissues if appropriate conditions are restored. In this review, we highlight the burst of recent knowledge leading to discovery of regenerative mechanisms also in adult kidneys.

RECENT FINDINGS

A large body of evidence has recently shown that the parietal epithelium of the Bowman's capsule represents a reservoir of renal progenitors in adult kidney.

SUMMARY

The discovery of a hierarchical population of renal progenitors within the Bowman's capsule which can generate novel podocytes and also proximal tubular cells provides a new point of view for the understanding of renal physiology. In addition, the observation that renal progenitors can also generate hyperplastic glomerular lesions opens up a novel view of the pathogenesis of different types of glomerular disorders, which may at least in part result from abnormal regenerative responses to podocyte injury.

Allogenic fetal membrane-derived mesenchymal stem cells contribute to renal repair in experimental glomerulonephritis

Mesenchymal stem cells (MSC) have been reported to be an attractive therapeutic cell source for the treatment of renal diseases. Recently, we reported that transplantation of allogenic fetal membrane-derived MSC (FM-MSC), which are available noninvasively in large amounts, had a therapeutic effect on a hindlimb ischemia model (Ishikane S, Ohnishi S, Yamahara K, Sada M, Harada K, Mishima K, Iwasaki K, Fujiwara M, Kitamura S, Nagaya N, Ikeda T. Stem Cells 26: 2625-2633, 2008). Here, we investigated whether allogenic FM-MSC administration could ameliorate renal injury in experimental glomerulonephritis. Lewis rats with anti-Thy1 nephritis intravenously received FM-MSC obtained from major histocompatibility complex-mismatched ACI rats (FM-MSC group) or a PBS (PBS group). Nephritic rats exhibited an increased urinary protein excretion in the PBS group, whereas the FM-MSC group rats had a significantly lower level of increase (P < 0.05 vs. PBS group). FM-MSC transplantation significantly reduced activated mesangial cell (MC) proliferation, glomerular monocyte/macrophage infiltration, mesangial matrix accumulation, as well as the glomerular expression of inflammatory or extracellular matrix-related genes including TNF-α, monocyte chemoattractant protein 1 (MCP-1), type I collagen, TGF-β, type 1 plasminogen activator inhibitor (PAI-1) (P < 0.05 vs. PBS group). In vitro, FM-MSC-derived conditioned medium significantly attenuated the expression of TNF-α and MCP-1 in rat MC through a prostaglandin E(2)-dependent mechanism. These data suggest that transplanted FM-MSC contributed to the healing process in injured kidney tissue by producing paracrine factors. Our results indicate that allogenic FM-MSC transplantation is a potent therapeutic strategy for the treatment of acute glomerulonephritis.