Combination of small molecules enhances differentiation of mouse embryonic stem cells into intermediate mesoderm through BMP7-positive cells

Induced pluripotent stem cells derived renal tubular cells from a patient with pseudohypoparathyroidism and its response to parathyroid hormone stimulation

INTRODUCTION

Creating induced pluripotent stem cells (iPSCs) from somatic cells of patients with genetic diseases offers a pathway to generate disease-specific iPSCs carrying genetic markers. Differentiating these iPSCs into renal tubular cells can aid in understanding the pathophysiology of rare inherited renal tubular diseases through cellular experiments.

MATERIALS AND METHODS

Two Japanese patients with Pseudohypoparathyroidism (PHP), a 49-year-old woman and a 71-year-old man, were studied. iPSC-derived tubular cells were established from their peripheral blood mononuclear cells (PBMCs). We examined changes in intracellular and extracellular cyclic adenosine monophosphate (cAMP) levels in these cells in response to parathyroid hormone (PTH) stimulation.

RESULTS

Renal tubular cells, differentiated from iPSCs of a healthy control (648A1), showed a PTH-dependent increase in both intracellular and extracellular cAMP levels. However, the renal tubular cells derived from the PHP patients' iPSCs showed inconsistent changes in cAMP levels upon PTH exposure.

CONCLUSION

We successfully created disease-specific iPSCs from PHP patients' PBMCs, differentiated them into tubular cells, and replicated the distinctive response of the disease to PTH in vitro. This approach could enhance our understanding of the pathophysiology of inherited renal tubular diseases and contribute to developing effective treatments.

Endoderm and mesoderm derivatives in embryonic stem cell differentiation and their use in developmental toxicity testing

Embryonic stem cell differentiation models have increasingly been applied in non-animal test systems for developmental toxicity. After the initial focus on cardiac differentiation, attention has also included an array of neuro-ectodermal differentiation routes. Alternative differentiation routes in the mesodermal and endodermal germ lines have received less attention. This review provides an inventory of achievements in the latter areas of embryonic stem cell differentiation, with a view to possibilities for their use in non-animal test systems in developmental toxicology. This includes murine and human stem cell differentiation models, and also gains information from the field of stem cell use in regenerative medicine. Endodermal stem cell derivatives produced in vitro include hepatocytes, pancreatic cells, lung epithelium, and intestinal epithelium, and mesodermal derivatives include cardiac muscle, osteogenic, vascular and hemopoietic cells. This inventory provides an overview of studies on the different cell types together with biomarkers and culture conditions that stimulate these differentiation routes from embryonic stem cells. These models may be used to expand the spectrum of embryonic stem cell based new approach methodologies in non-animal developmental toxicity testing.

Human reconstructed kidney models

The human kidney, which consists of up to 2 million nephrons, is critical for blood filtration, electrolyte balance, pH regulation, and fluid balance in the body. Animal experiments, particularly mice and rats, combined with advances in genetically modified technology have been the primary mechanism to study kidney injury in recent years. Mouse or rat kidneys, however, differ substantially from human kidneys at the anatomical, histological, and molecular levels. These differences combined with increased regulatory hurdles and shifting attitudes towards animal testing by non-specialists have led scientists to develop new and more relevant models of kidney injury. Although in vitro tissue culture studies are a valuable tool to study kidney injury and have yielded a great deal of insight, they are not a perfect model. Perhaps, the biggest limitation of tissue culture is that it cannot replicate the complex architecture, consisting of multiple cell types, of the kidney, and the interplay between these cells. Recent studies have found that pluripotent stem cells (PSCs), which are capable of differentiation into any cell type, can be used to generate kidney organoids. Organoids recapitulate the multicellular relationships and microenvironments of complex organs like kidney. Kidney organoids have been used to successfully model nephrotoxin-induced tubular and glomerular disease as well as complex diseases such as chronic kidney disease (CKD), which involves multiple cell types. In combination with genetic engineering techniques, such as CRISPR-Cas9, genetic diseases of the kidney can be reproduced in organoids. Thus, organoid models have the potential to predict drug toxicity and enhance drug discovery for human disease more accurately than animal models.

Reduced expression of odd-skipped related transcription factor 1 promotes proliferation and invasion of breast cancer cells and indicates poor patient prognosis

Odd-skipped related transcription factor 1 (OSR1) serves an important role in the development of the intermediate mesoderm; however, its expression in cancer remains unknown. The present study aimed to explore the expression and role of OSR1 in breast cancer development. Immunohistochemistry was performed to detect OSR1 expression in breast cancer tissue and western blot analysis was used to evaluate the expression of OSR1 and related proteins, including β-catenin, c-Myc and cyclin D1. OSR1 expression was increased following transfection of MCF7 cells with OSR1 overexpression vector (MCF7-OSR1) and reduced by transfecting MDA-MB-231 cells with small interfering (si)RNA targeting OSR1 (MDA-MB-231-siOSR1). Cell proliferation and Matrigel™ invasion assays were used to investigate the effects of OSR1 on the proliferation and invasion of breast cancer cells. OSR1 was downregulated in breast cancer tissue compared with that in normal breast tissue and associated with lymph node metastases and estrogen receptor (ER) expression. Furthermore, reduced expression of OSR1 was associated with poor patient prognosis. Overexpression of OSR1 inhibited the proliferation and invasion of breast cancer cells. Western blot analysis of MCF7-OSR1 cells demonstrated that compared with that in the control cells, the expression of E-cadherin was increased, whereas that of key epithelial-mesenchymal transition (EMT) proteins, N-cadherin and Snail, was decreased. In addition, overexpression of OSR1 significantly decreased the expression level of β-catenin and Wnt target genes, such as c-Myc and cyclin D1, compared with that in the control cells. These expression patterns were reversed in the MDA-MB-231-siOSR1 cells. The results of the present study suggested that OSR1 downregulates the activity of the Wnt signaling pathway and EMT, which inhibits the proliferative and invasive abilities of breast cancer cells.

Synthesis of orotic acid derivatives and their effects on stem cell proliferation

Orotic acid, a natural product, is involved in many biological processes. Human mesenchymal stem cells (hMSCs) have the potential of self-renewable and proliferation. They are commonly isolated from the bone marrow aspirates of large bones. The osteogenic potential of these stem cells has been extensively exploited by scientists in the past to evaluate the performance of synthetic scaffolds developed for tissue engineering. In this study, N-arylhydrazone derivatives of orotic acid have been synthesized, and their potential as stimulators of human mesenchymal stem cells has been evaluated. Some of the analogs exhibit well to moderate effect on the proliferation rate.

Improved differentiation of human enriched CD133+CD24+ renal progenitor cells derived from embryonic stem cell with embryonic mouse kidney-derived mesenchymal stem cells co-culture

End-stage renal disease (ESRD) is a major global public health issue. In the past decade, regenerative medicine and cell-based therapies were recommended for treatment of devastating diseases like ESRD. Renal progenitor (RP) cells are essential players in such treatment approaches. The major practical difficulties in application of RP cells are generation of these cells and preservation of their self-renewal capacity; also, they should lack identified appropriate cell surface markers. To identify and isolate RP cells, two cell surface markers namely, CD133 and CD24 were recently used. In this study, we used these markers to facilitate selection and purification of RP cells from embryoid bodies (EBs), and assessed the impact of the use of bFGF on frequency of CD133⁺CD24⁺ expression in cells presented in EBs. Moreover, following isolation of CD133⁺CD24⁺ cells from EBs, we evaluated the effect of embryonic, neonatal and adult mouse kidney-derived mesenchymal stem cells (E-KMSC, N-KMSC and A-KMSC respectively) and fibronectin on further differentiation of the sorted cells. Hence, we cultured undifferentiated human embryonic stem cells (hESCs) in suspension state in the presence or absence of bFGF and determined maximum number of CD133⁺CD24⁺ cells in bFGF-treated EBs on day 7. Then, we tested the effect of E-KMSC co-culture and seeding on fibronectin-coated plated on differentiation of the sorted cells into renal epithelial cells. Results revealed down-regulation of several RP cells, markers in CD133⁺CD24⁺ cells. In contrast, renal epithelial marker gene expressions were up-regulated after 7 days of co-culture with E-KMSC. Furthermore, fibronectin resulted in higher expression of renal epithelial markers compared to the E-KMSC co-cultured cells. All in all, bFGF could enhance the number of RP cells expressing CD133 and CD24 markers, in human EBs. We suggest E-KMSC and fibronectin as a promising supplementary factor to further induce differentiation of RP cells into renal epithelial cells.

Embryonic Stem Cells Derived Kidney Organoids as Faithful Models to Target Programmed Nephrogenesis

The kidney is a complex organ that is comprised of thousands of nephrons developing through reciprocal inductive interactions between metanephric mesenchyme (MM) and ureteric bud (UB). The MM undergoes mesenchymal to epithelial transition (MET) in response to the signaling from the UB. The secreted protein Wnt4, one of the Wnt family members, is critical for nephrogenesis as mouse Wnt4^−/− mutants fail to form pretubular aggregates (PTA) and therefore lack functional nephrons. Here, we generated mouse embryonic stem cell (mESC) line lacking Wnt4 by applying the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated systems 9 (Cas9). We describe here, differentiation of the wild type and Wnt4 knockout mESCs into kidney progenitors, and such cells induced to undergo nephrogenesis by the mouse E11.5 UB mediated induction. The wild type three-dimensional (3D) self-organized organoids depict appropriately segmented nephron structures, while the Wnt4-deficient organoids fail to undergo the MET, as is the case in the phenotype of the Wnt4 knockout mouse model in vivo. In summary, we have established a platform that combine CRISPR/Cas9 and kidney organoid technologies to model kidney development in vitro and confirmed that mutant organoids are able to present similar actions as in the in vivo studies.

Kidney Organoids: A Translational Journey

Human pluripotent stem cells (hPSCs) are attractive sources for regenerative medicine and disease modeling in vitro. Directed hPSC differentiation approaches have derived from knowledge of cell development in vivo rather than from stochastic cell differentiation. Moreover, there has been great success in the generation of 3D organ-buds termed 'organoids' from hPSCs; these consist of a variety of cell types in vitro that mimic organs in vivo. The organoid bears great potential in the study of human diseases in vitro, especially when combined with CRISPR/Cas9-based genome-editing. We summarize the current literature describing organoid studies with a special focus on kidney organoids, and discuss goals and future opportunities for organoid-based studies.

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.

Generation of functional podocytes from human induced pluripotent stem cells

Generating human podocytes in vitro could offer a unique opportunity to study human diseases. Here, we describe a simple and efficient protocol for obtaining functional podocytes in vitro from human induced pluripotent stem cells. Cells were exposed to a three-step protocol, which induced their differentiation into intermediate mesoderm, then into nephron progenitors and, finally, into mature podocytes. After differentiation, cells expressed the main podocyte markers, such as synaptopodin, WT1, α-Actinin-4, P-cadherin and nephrin at the protein and mRNA level, and showed the low proliferation rate typical of mature podocytes. Exposure to Angiotensin II significantly decreased the expression of podocyte genes and cells underwent cytoskeleton rearrangement. Cells were able to internalize albumin and self-assembled into chimeric 3D structures in combination with dissociated embryonic mouse kidney cells. Overall, these findings demonstrate the establishment of a robust protocol that, mimicking developmental stages, makes it possible to derive functional podocytes in vitro.

•

Human iPSC differentiation into podocytes recapitulates kidney developmental stages.

•

The differentiation protocol is reproducible and highly efficient.

•

The generated podocytes reflect primary cell behaviour and are functional.

The origin of the mammalian kidney: implications for recreating the kidney in vitro

The mammalian kidney, the metanephros, is a mesodermal organ classically regarded as arising from the intermediate mesoderm (IM). Indeed, both the ureteric bud (UB), which gives rise to the ureter and the collecting ducts, and the metanephric mesenchyme (MM), which forms the rest of the kidney, derive from the IM. Based on an understanding of the signalling molecules crucial for IM patterning and kidney morphogenesis, several studies have now generated UB or MM, or both, in vitro via the directed differentiation of human pluripotent stem cells. Although these results support the IM origin of the UB and the MM, they challenge the simplistic view of a common progenitor for these two populations, prompting a reanalysis of early patterning events within the IM. Here, we review our understanding of the origin of the UB and the MM in mouse, and discuss how this impacts on kidney regeneration strategies and furthers our understanding of human development.

Kidney regeneration from human induced pluripotent stem cells

PURPOSE OF REVIEW

Human induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs) are potential unlimited cell sources for renal cells in regenerative medicine. This review highlights recent advance in the directed differentiation of human iPSCs into kidney lineages and discusses the remaining challenges to generate functional or mature renal cells from human iPSCs.

RECENT FINDINGS

Recently, directed differentiation methods from human iPSCs/ESCs into embryonic renal progenitor cells, such as those included in metanephric mesenchyme and ureteric bud, that mimic embryonic development have been reported. These studies show the developmental potential of progenitor cells by forming renal tubule-like or glomerulus-like structures in vitro. However, it has not been verified whether the physiological functions of the induced progenitors are equivalent to their in-vivo counterparts. The establishment of definitive marker genes for kidney lineages and functional assay systems is essential for the verification. Such achievement is needed before kidney regeneration can provide cell replacement therapy, reliable disease models and elucidation of the mechanisms of kidney development.

SUMMARY

In conclusion, this review outlines milestones in directed differentiation methods for functional renal cell types from human iPSCs toward clinical application and practical use.

Pluripotent Stem Cells to Rebuild a Kidney: The Lymph Node as a Possible Developmental Niche

Kidney disease poses a global challenge. Stem cell therapy may offer an alternative therapeutic approach to kidney transplantation, which is often hampered by the limited supply of donor organs. While specific surface antigen markers have yet to be identified for the analysis and purification of kidney stem/progenitor cells for research or clinical use, the reprogramming of somatic cells to pluripotent cells and their differentiation into the various kidney lineages might represent a valuable strategy to create a renewable cell source for regenerative purposes. In this review, we first provide an overview of kidney development and explore current knowledge about the role of extra- and intrarenal cells in kidney repair and organogenesis. We then discuss recent advances in the 1) differentiation of rodent and human embryonic stem cells (ESCs) into renal lineages; 2) generation of induced pluripotent stem cells (iPSCs) from renal or nonrenal (kidney patient-derived) adult cells; 3) differentiation of iPSCs into renal lineages; and 4) direct transcriptional reprogramming of adult renal cells into kidney progenitor cells. Finally, we describe the lymph node as a potential three-dimensional (3D) in vivo environment for kidney organogenesis from pluripotent stem cells.

Renal progenitors derived from human iPSCs engraft and restore function in a mouse model of acute kidney injury

Acute kidney injury (AKI) is one of the most relevant health issues, leading to millions of deaths. The magnitude of the phenomenon remarks the urgent need for innovative and effective therapeutic approaches. Cell-based therapy with renal progenitor cells (RPCs) has been proposed as a possible strategy. Studies have shown the feasibility of directing embryonic stem cells or induced Pluripotent Stem Cells (iPSCs) towards nephrogenic intermediate mesoderm and metanephric mesenchyme (MM). However, the functional activity of iPSC-derived RPCs has not been tested in animal models of kidney disease. Here, through an efficient inductive protocol, we directed human iPSCs towards RPCs that robustly engrafted into damaged tubuli and restored renal function and structure in cisplatin-mice with AKI. These results demonstrate that iPSCs are a valuable source of engraftable cells with regenerative activity for kidney disease and create the basis for future applications in stem cell-based therapy.

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.

Directed differentiation of pluripotent stem cells to kidney cells

Regenerative medicine affords a promising therapeutic strategy for the treatment of patients with chronic kidney disease. Nephron progenitor cell populations exist only during embryonic kidney development. Understanding the mechanisms by which these populations arise and differentiate is integral to the challenge of generating new nephrons for therapeutic purposes. Pluripotent stem cells (PSCs), comprising embryonic stem cells, and induced pluripotent stem cells (iPSCs) derived from adults, have the potential to generate functional kidney cells and tissue. Studies in mouse and human PSCs have identified specific approaches to the addition of growth factors, including Wnt and fibroblast growth factor, that can induce PSC differentiation into cells with phenotypic characteristics of nephron progenitor populations with the capacity to form kidney-like structures. Although significant progress has been made, further studies are necessary to confirm the production of functional kidney cells and to promote their three-dimensional organization into bona fide kidney tissue. Human PSCs have been generated from patients with kidney diseases, including polycystic kidney disease, Alport syndrome, and Wilms tumor, and may be used to better understand phenotypic consequences of naturally occurring genetic mutations and to conduct "clinical trials in a dish". The capability to generate human kidney cells from PSCs has significant translational applications, including the bioengineering of functional kidney tissue, use in drug development to test compounds for efficacy and toxicity, and in vitro disease modeling.

Recreating kidney progenitors from pluripotent cells

Access to human pluripotent cells theoretically provides a renewable source of cells that can give rise to any required cell type for use in cellular therapy or bioengineering. However, successfully directing this differentiation remains challenging for most desired endpoints cell type, including renal cells. This challenge is compounded by the difficulty in identifying the required cell type in vitro and the multitude of renal cell types required to build a kidney. Here we review our understanding of how the embryo goes about specifying the cells of the kidney and the progress to date in adapting this knowledge for the recreation of nephron progenitors and their mature derivatives from pluripotent cells.

Priming the renal progenitor cell

The mammalian kidney arises from OSR1(+) progenitor cells in the intermediate mesoderm. However, these cells must acquire unique properties before they can respond to inductive signals that launch the differentiation program. Recent data indicate that the transcription factor, WT1, plays a master role in this transition. Interestingly, some of these embryonic nephron progenitor cells are retained in the adult organ where they may participate in tissue regeneration after acute kidney injury. A better understanding of the biology of these cells may one day allow progenitor cell-based therapeutic strategies to help regenerate damaged adult nephrons.

Rapid and efficient differentiation of human pluripotent stem cells into intermediate mesoderm that forms tubules expressing kidney proximal tubular markers

Human pluripotent stem cells (hPSCs) can generate a diversity of cell types, but few methods have been developed to derive cells of the kidney lineage. Here, we report a highly efficient system for differentiating human embryonic stem cells and induced pluripotent stem cells (referred to collectively as hPSCs) into cells expressing markers of the intermediate mesoderm (IM) that subsequently form tubule-like structures. Treatment of hPSCs with the glycogen synthase kinase-3β inhibitor CHIR99021 induced BRACHYURY(+)MIXL1(+) mesendoderm differentiation with nearly 100% efficiency. In the absence of additional exogenous factors, CHIR99021-induced mesendodermal cells preferentially differentiated into cells expressing markers of lateral plate mesoderm with minimal IM differentiation. However, the sequential treatment of hPSCs with CHIR99021 followed by fibroblast growth factor-2 and retinoic acid generated PAX2(+)LHX1(+) cells with 70%-80% efficiency after 3 days of differentiation. Upon growth factor withdrawal, these PAX2(+)LHX1(+) cells gave rise to apically ciliated tubular structures that coexpressed the proximal tubule markers Lotus tetragonolobus lectin, N-cadherin, and kidney-specific protein and partially integrated into embryonic kidney explant cultures. With the addition of FGF9 and activin, PAX2(+)LHX1(+) cells specifically differentiated into cells expressing SIX2, SALL1, and WT1, markers of cap mesenchyme nephron progenitor cells. Our findings demonstrate the effective role of fibroblast growth factor signaling in inducing IM differentiation in hPSCs and establish the most rapid and efficient system whereby hPSCs can be differentiated into cells with features characteristic of kidney lineage cells.

Human kidney cell reprogramming: applications for disease modeling and personalized medicine

The ability to reprogram fully differentiated cells into a pluripotent embryonic state, termed induced pluripotent stem cells (iPSCs), has been met with great excitement. iPSC technology has advanced the fundamental study of disease modeling with the potential for cell-replacement therapy, especially in the neuronal and cardiac fields. However, renal medicine as of yet has not benefited from similar advancements. This review summarizes the unique characteristics of iPSCs and their potential applications for modeling kidney disease. Pioneering such endeavors could yield constructs that recapitulate disease phenotypes, open avenues for more targeted drug development, and potentially serve as replenishable sources for replacement of kidney cells in the setting of human disease.

Monitoring and robust induction of nephrogenic intermediate mesoderm from human pluripotent stem cells

A method for stimulating the differentiation of human pluripotent stem cells into kidney lineages remains to be developed. Most cells in kidney are derived from an embryonic germ layer known as intermediate mesoderm. Here we show the establishment of an efficient system of homologous recombination in human pluripotent stem cells by means of bacterial artificial chromosome-based vectors and single-nucleotide polymorphism array-based detection. This system allowed us to generate human-induced pluripotent stem cell lines containing green fluorescence protein knocked into OSR1, a specific intermediate mesoderm marker. We have also established a robust induction protocol for intermediate mesoderm, which produces up to 90% OSR1(+) cells. These human intermediate mesoderm cells can differentiate into multiple cell types of intermediate mesoderm-derived organs in vitro and in vivo, thereby supplying a useful system to elucidate the mechanisms of intermediate mesoderm development and potentially providing a cell source for regenerative therapies of the kidney.

Kidney specific protein-positive cells derived from embryonic stem cells reproduce tubular structures in vitro and differentiate into renal tubular cells

Embryonic stem cells and induced pluripotent stem cells have the ability to differentiate into various organs and tissues, and are regarded as new tools for the elucidation of disease mechanisms as well as sources for regenerative therapies. However, a method of inducing organ-specific cells from pluripotent stem cells is urgently needed. Although many scientists have been developing methods to induce various organ-specific cells from pluripotent stem cells, renal lineage cells have yet to be induced in vitro because of the complexity of kidney structures and the diversity of kidney-component cells. Here, we describe a method of inducing renal tubular cells from mouse embryonic stem cells via the cell purification of kidney specific protein (KSP)-positive cells using an anti-KSP antibody. The global gene expression profiles of KSP-positive cells derived from ES cells exhibited characteristics similar to those of cells in the developing kidney, and KSP-positive cells had the capacity to form tubular structures resembling renal tubular cells when grown in a 3D culture in Matrigel. Moreover, our results indicated that KSP-positive cells acquired the characteristics of each segment of renal tubular cells through tubular formation when stimulated with Wnt4. This method is an important step toward kidney disease research using pluripotent stem cells, and the development of kidney regeneration therapies.

iPS cell technology-based research for the treatment of diabetic nephropathy

Regenerative medicine strategies using induced pluripotent stem (iPS) cells are among the candidate approaches to treat diabetic nephropathy caused by type 1 diabetes. Cell transplantation therapy and disease modeling with patient-derived iPS cells should be examined for diabetic renal disease. Considerable work already has been performed with regard to the generation of renal lineage cells from mouse embryonic stem cells, however, few reports have described research with human embryonic stem cells or iPS cells. Further elucidation of the mechanisms of kidney development and establishing the method for directed differentiation from human iPS cells into renal lineage cells will be required for the development of iPS cell technology-based treatment for diabetic nephropathy.

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.

The directed differentiation of human iPS cells into kidney podocytes

The loss of glomerular podocytes is a key event in the progression of chronic kidney disease resulting in proteinuria and declining function. Podocytes are slow cycling cells that are considered terminally differentiated. Here we provide the first report of the directed differentiation of induced pluripotent stem (iPS) cells to generate kidney cells with podocyte features. The iPS-derived podocytes share a morphological phenotype analogous with cultured human podocytes. Following 10 days of directed differentiation, iPS podocytes had an up-regulated expression of mRNA and protein localization for podocyte markers including synaptopodin, nephrin and Wilm’s tumour protein (WT1), combined with a down-regulation of the stem cell marker OCT3/4. In contrast to human podocytes that become quiescent in culture, iPS-derived cells maintain a proliferative capacity suggestive of a more immature phenotype. The transduction of iPS podocytes with fluorescent labeled-talin that were immunostained with podocin showed a cytoplasmic contractile response to angiotensin II (AII). A permeability assay provided functional evidence of albumin uptake in the cytoplasm of iPS podocytes comparable to human podocytes. Moreover, labeled iPS-derived podocytes were found to integrate into reaggregated metanephric kidney explants where they incorporated into developing glomeruli and co-expressed WT1. This study establishes the differentiation of iPS cells to kidney podocytes that will be useful for screening new treatments, understanding podocyte pathogenesis, and offering possibilities for regenerative medicine.

Intravenous renal cell transplantation for rats with acute and chronic renal failure

Acute kidney injury (AKI) and chronic renal failure (CKD) are the most challenging problems in nephrology. Multiple therapies have been attempted but these interventions have minimal effects on the eventual outcomes, and all too often the result is end-stage renal disease (ESRD). The only effective therapy for ESRD is renal transplantation but only a small fraction of patients receive transplants. In this work we introduce a novel approach to transplantation designed to regenerate kidneys afflicted by severe AKI or CKD: intravenous renal cell transplantation (IRCT) with adult rat primary renal cells reprogrammed to express the SAA gene localized and engrafted in kidneys of rat recipients that had severe AKI or CKD. IRCT significantly resolved renal dysfunction and limited kidney damage, inflammation, and fibrosis. Severe CKD was successfully improved by IRCT using kidney cells from donor rats or by renal cell self-donation in a form of autotransplantation. We propose that IRCT with adult primary renal cells reprogrammed to express the SAA gene can be used to effectively treat AKI and CKD.

Successful disease-specific induced pluripotent stem cell generation from patients with kidney transplantation

Introduction

End-stage renal disease (ESRD) is a major public health problem. Although kidney transplantation is a viable therapeutic option, this therapy is associated with significant limitations, including a shortage of donor organs. Induced pluripotent stem (iPS) cell technology, which allows derivation of patient-specific pluripotent stem cells, could provide a possible alternative modality for kidney replacement therapy for patients with ESRD.

Methods

The feasibility of iPS cell generation from patients with a history of ESRD was investigated using lentiviral vectors expressing pluripotency-associated factors.

Results

In the present article we report, for the first time, generation of iPS cells from kidney transplant recipients with a history of autosomal-dominant polycystic kidney disease (ADPKD), systemic lupus erythematosus, or Wilms tumor and ESRD. Lentiviral transduction of OCT4, SOX2, KLF4 and c-MYC, under feeder-free conditions, resulted in reprogramming of skin-derived keratinocytes. Keratinocyte-derived iPS cells exhibited properties of human embryonic stem cells, including morphology, growth properties, expression of pluripotency genes and surface markers, spontaneous differentiation and teratoma formation. All iPS cell clones from the ADPKD patient retained the conserved W3842X mutation in exon 41 of the PKD1 gene.

Conclusions

Our results demonstrate successful iPS cell generation from patients with a history of ESRD, PKD1 gene mutation, or chronic immunosuppression. iPS cells from autosomal kidney diseases, such as ADPKD, would provide unique opportunities to study patient-specific disease pathogenesis in vitro.

The Osr1 and Osr2 genes act in the pronephric anlage downstream of retinoic acid signaling and upstream of Wnt2b to maintain pectoral fin development

Vertebrate odd-skipped related genes (Osr) have an essential function during the formation of the intermediate mesoderm (IM) and the kidney structures derived from it. Here, we show that these genes are also crucial for limb bud formation in the adjacent lateral plate mesoderm (LPM). Reduction of zebrafish Osr function impairs fin development by the failure of tbx5a maintenance in the developing pectoral fin bud. Osr morphant embryos show reduced wnt2b expression, and increasing Wnt signaling in Osr morphant embryos partially rescues tbx5a expression. Thus, Osr genes control limb bud development in a non-cell-autonomous manner, probably through the activation of Wnt2b. Finally, we demonstrate that Osr genes are downstream targets of retinoic acid (RA) signaling. Therefore, Osr genes act as a relay within the genetic cascade of fin bud formation: by controlling the expression of the signaling molecule Wnt2ba in the IM they play an essential function transmitting the RA signaling originated in the somites to the LPM.

Regenerative medicine of the kidney

End stage renal disease is a major health problem in this country and worldwide. Although dialysis and kidney transplantation are currently used to treat this condition, kidney regeneration resulting in complete healing would be a desirable alternative. In this review we focus our attention on current therapeutic approaches used clinically to delay the onset of kidney failure. In addition we describe novel approaches, like Tissue Engineering, Stem cell Applications, Gene Therapy, and Renal Replacement Therapy that may one day be possible alternative therapies for patients with the hope of delaying kidney failure or even stopping the progression of renal disease.

In vitro regeneration of kidney from pluripotent stem cells

Although renal transplantation has proved a successful treatment for the patients with end-stage renal failure, the therapy is hampered by the problem of serious shortage of donor organs. Regenerative medicine using stem cells, including cell transplantation therapy, needs to be developed to solve the problem. We previously identified the multipotent progenitor cells in the embryonic mouse kidney that can give rise to several kinds of epithelial cells found in adult kidney, such as glomerular podocytes and renal tubular epithelia. Establishing the method to generate the progenitors from human pluripotent stem cells that have the capacity to indefinitely proliferate in vitro is required for the development of kidney regeneration strategy. We review the current status of the research on the differentiation of pluripotent stem cells into renal lineages and describe cues to promote this research field.