Generation of infant- and pediatric-derived urinary induced pluripotent stem cells competent to form kidney organoids

Urine-derived stem cells: a sustainable resource for advancing personalized medicine and dental regeneration

Urine-based therapy, an ancient practice, has been utilized across numerous civilizations to address a wide range of ailments. Urine was considered a priceless resource in numerous traditional therapeutic applications due to its reported medicinal capabilities. While the utilization of urine treatment is contentious and lacks significant support from modern healthcare, the discovery of urine-derived stem cells (UDSCs) has introduced a promising avenue for cell-based therapy. UDSCs offer a noninvasive and easily repeatable collection method, making them a practical and viable option for therapeutic applications. Research has shown that UDSCs contribute to organ preservation by promoting revascularization and decreasing inflammatory reactions in many diseases and conditions. This review will outline the contemporary status of UDSCs research and explore their potential applications in both fundamental science and medical practice.

Distinct molecular profiles and shared drug vulnerabilities in pancreatic metastases of renal cell carcinoma

Clear-cell renal cell carcinoma (ccRCC) is the most common origin of pancreatic metastases (PM). Distinct genomic aberrations, favorable prognosis, and clinical observations on high angiogenesis, and succeeding tyrosine kinase inhibitor (TKI) sensitivity have been reported in PM-ccRCC. However, no functional or single-cell studies have been conducted thus far. We recruited five PM-ccRCC patients and investigated the genomic, single-cell transcriptomic, and drug sensitivity profiles of their patient-derived cells (PDCs). The PM depicted both expected and novel genomic alterations. Further, the transcriptomics differed from both primary and metastatic ccRCC, with upregulations of the PI3K/mTOR and - supporting the clinical observations - angiogenesis pathways. Data integration at pathway level showed that transcriptomics explained drug sensitivities the best. Accordingly, PM-ccRCC PDCs shared sensitivity to many PI3K/mTOR inhibitors. Altogether, we show distinct genomic and transcriptomic signatures in PM-ccRCC, highlight the superiority of transcriptomics in interpreting drug sensitivities, and encourage the use of TKIs and PI3K/mTOR inhibitors in PM-ccRCC.

Application prospects of urine-derived stem cells in neurological and musculoskeletal diseases

Urine-derived stem cells (USCs) are derived from urine and harbor the potential of proliferation and multidirectional differentiation. Moreover, USCs could be reprogrammed into pluripotent stem cells [namely urine-derived induced pluripotent stem cells (UiPSCs)] through transcription factors, such as octamer binding transcription factor 4, sex determining region Y-box 2, kruppel-like factor 4, myelocytomatosis oncogene, and Nanog homeobox and protein lin-28, in which the first four are known as Yamanaka factors. Mounting evidence supports that USCs and UiPSCs possess high potential of neurogenic, myogenic, and osteogenic differentiation, indicating that they may play a crucial role in the treatment of neurological and musculoskeletal diseases. Therefore, we summarized the origin and physiological characteristics of USCs and UiPSCs and their therapeutic application in neurological and musculoskeletal disorders in this review, which not only contributes to deepen our understanding of hallmarks of USCs and UiPSCs but also provides the theoretical basis for the treatment of neurological and musculoskeletal disorders with USCs and UiPSCs.

Exploiting urine-derived induced pluripotent stem cells for advancing precision medicine in cell therapy, disease modeling, and drug testing

The field of regenerative medicine has witnessed remarkable advancements with the emergence of induced pluripotent stem cells (iPSCs) derived from a variety of sources. Among these, urine-derived induced pluripotent stem cells (u-iPSCs) have garnered substantial attention due to their non-invasive and patient-friendly acquisition method. This review manuscript delves into the potential and application of u-iPSCs in advancing precision medicine, particularly in the realms of drug testing, disease modeling, and cell therapy. U-iPSCs are generated through the reprogramming of somatic cells found in urine samples, offering a unique and renewable source of patient-specific pluripotent cells. Their utility in drug testing has revolutionized the pharmaceutical industry by providing personalized platforms for drug screening, toxicity assessment, and efficacy evaluation. The availability of u-iPSCs with diverse genetic backgrounds facilitates the development of tailored therapeutic approaches, minimizing adverse effects and optimizing treatment outcomes. Furthermore, u-iPSCs have demonstrated remarkable efficacy in disease modeling, allowing researchers to recapitulate patient-specific pathologies in vitro. This not only enhances our understanding of disease mechanisms but also serves as a valuable tool for drug discovery and development. In addition, u-iPSC-based disease models offer a platform for studying rare and genetically complex diseases, often underserved by traditional research methods. The versatility of u-iPSCs extends to cell therapy applications, where they hold immense promise for regenerative medicine. Their potential to differentiate into various cell types, including neurons, cardiomyocytes, and hepatocytes, enables the development of patient-specific cell replacement therapies. This personalized approach can revolutionize the treatment of degenerative diseases, organ failure, and tissue damage by minimizing immune rejection and optimizing therapeutic outcomes. However, several challenges and considerations, such as standardization of reprogramming protocols, genomic stability, and scalability, must be addressed to fully exploit u-iPSCs' potential in precision medicine. In conclusion, this review underscores the transformative impact of u-iPSCs on advancing precision medicine and highlights the future prospects and challenges in harnessing this innovative technology for improved healthcare outcomes.

Advances and potential of regenerative medicine in pediatric nephrology

The endogenous capacity of the kidney to repair is limited, and generation of new nephrons after injury for adequate function recovery remains a need. Discovery of factors that promote the endogenous regenerative capacity of the injured kidney or generation of transplantable kidney tissue represent promising therapeutic strategies. While several encouraging results are obtained after administration of stem or progenitor cells, stem cell secretome, or extracellular vesicles in experimental kidney injury models, very little data exist in the clinical setting to make conclusions about their efficacy. In this review, we provide an overview of the cutting-edge knowledge on kidney regeneration, including pre-clinical methodologies used to elucidate regenerative pathways and describe the perspectives of regenerative medicine for kidney patients.

Hedgehog signalling in Foxd1+ embryonic kidney stromal progenitors controls nephron formation via Cxcl12 and Wnt5a

Congenital anomalies of the kidney and urinary tract (CAKUT) are characterised by a spectrum of structural and histologic abnormalities and are the major cause of childhood kidney failure. During kidney morphogenesis, the formation of a critical number of nephrons is an embryonic process supported, in part, by signalling between nephrogenic precursors and Foxd1-positive stromal progenitor cells. Low nephron number and abnormal patterning of the stroma are signature pathological features among CAKUT phenotypes with decreased kidney function. Despite their critical contribution to CAKUT pathogenesis, the mechanisms that underlie a low nephron number and the functional contribution of a disorganised renal stroma to nephron number are both poorly defined. Here, we identify a primary pathogenic role for increased Hedgehog signalling in embryonic renal stroma in the genesis of congenital low nephron number. Pharmacologic activation of Hedgehog (Hh) signalling in human kidney organoid tissue decreased the number of nephrons and generated excess stroma. The mechanisms underlying these pathogenic effects were delineated in genetic mouse models in which Hh signalling was constitutively activated in a cell lineage-specific manner. Cre-mediated excision of Ptch1 in Foxd1+ stromal progenitor cells, but not in Six2+ nephrogenic precursor cells, generated kidney malformation, identifying the stroma as a driver of low nephron number. Single-cell RNA sequencing analysis identified Cxcl12 and Wnt5a as downstream targets of increased stromal Hh signalling, findings supported by analysis in human kidney organoids. In vivo deficiency of Cxcl12 or Wnt5a in mice with increased stromal Hh signalling improved nephron endowment. These results demonstrate that dysregulated Hh signalling in embryonic renal stromal cells inhibits nephron formation in a manner dependent on Cxcl12 and Wnt5a. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Hedgehog-GLI mediated control of renal formation and malformation

CAKUT is the leading cause of end-stage kidney disease in children and comprises a broad spectrum of phenotypic abnormalities in kidney and ureter development. Molecular mechanisms underlying the pathogenesis of CAKUT have been elucidated in genetic models, predominantly in the mouse, a paradigm for human renal development. Hedgehog (Hh) signaling is critical to normal embryogenesis, including kidney development. Hh signaling mediates the physiological development of the ureter and stroma and has adverse pathophysiological effects on the metanephric mesenchyme, ureteric, and nephrogenic lineages. Further, disruption of Hh signaling is causative of numerous human developmental disorders associated with renal malformation; Pallister-Hall Syndrome (PHS) is characterized by a diverse spectrum of malformations including CAKUT and caused by truncating variants in the middle-third of the Hh signaling effector GLI3. Here, we outline the roles of Hh signaling in regulating murine kidney development, and review human variants in Hh signaling genes in patients with renal malformation.

Generation of mesenchymal stromal cells from urine-derived iPSCs of pediatric brain tumor patients

Human induced pluripotent stem cells (iPSCs) provide a virtually inexhaustible source of starting material for next generation cell therapies, offering new opportunities for regenerative medicine. Among different cell sources for the generation of iPSCs, urine cells are clinically relevant since these cells can be repeatedly obtained by non-invasive methods from patients of any age and health condition. These attributes encourage patients to participate in preclinical and clinical research. In particular, the use of urine-derived iPSC products is a convenient strategy for children with brain tumors, which are medically fragile patients. Here, we investigate the feasibility of using urine samples as a source of somatic cells to generate iPSC lines from pediatric patients with brain tumors (BT-iPSC). Urinary epithelial cells were isolated and reprogrammed using non-integrative Sendai virus vectors harboring the Yamanaka factors KLF4, OCT3/4, SOX2 and C-MYC. After reprogramming, BT-iPSC lines were subject to quality assessment and were compared to iPSCs obtained from urine samples of non-tumor pediatric patients (nonT-iPSC). We demonstrated that iPSCs can be successfully derived from a small volume of urine obtained from pediatric patients. Importantly, we showed that BT-iPSCs are equivalent to nonT-iPSCs in terms of morphology, pluripotency, and differentiation capacity into the three germ layers. In addition, both BT-iPSCs and nonT-iPSCs efficiently differentiated into functional mesenchymal stem/stromal cells (iMSC) with immunomodulatory properties. Therefore, this study provides an attractive approach to non-invasively generate personalized iMSC products intended for the treatment of children with brain tumors.

Reprogramming stem cells in regenerative medicine

Induced pluripotent stem cells (iPSCs) that are generated from adult somatic cells are induced to express genes that make them pluripotent through reprogramming techniques. With their unlimited proliferative capacity and multifaceted differentiation potential and circumventing the ethical problems encountered in the application of embryonic stem cells (ESC), iPSCs have a broad application in the fields of cell therapy, drug screening, and disease models and may open up new possibilities for regenerative medicine to treat diseases in the future. In this review, we begin with different reprogramming cell technologies to obtain iPSCs, including biotechnological, chemical, and physical modulation techniques, and present their respective strengths, and limitations, as well as the recent progress of research. Secondly, we review recent research advances in iPSC reprogramming-based regenerative therapies. iPSCs are now widely used to study various clinical diseases of hair follicle defects, myocardial infarction, neurological disorders, liver diseases, and spinal cord injuries. This review focuses on the translational clinical research around iPSCs as well as their potential for growth in the medical field. Finally, we summarize the overall review and look at the potential future of iPSCs in the field of cell therapy as well as tissue regeneration engineering and possible problems. We believe that the advancing iPSC research will help drive long-awaited breakthroughs in cellular therapy.

Determining epigenetic memory in kidney proximal tubule cell derived induced pluripotent stem cells using a quadruple transgenic reprogrammable mouse

The majority of nucleated somatic cells can be reprogrammed to induced pluripotent stem cells (iPSCs). The process of reprogramming involves epigenetic remodelling to turn on pluripotency-associated genes and turn off lineage-specific genes. Some evidence shows that iPSCs retain epigenetic marks of their cell of origin and this "epigenetic memory" influences their differentiation potential, with a preference towards their cell of origin. Here, we reprogrammed proximal tubule cells (PTC) and tail tip fibroblasts (TTF), from a reprogrammable mouse to iPSCs and differentiated the iPSCs to renal progenitors to understand if epigenetic memory plays a role in renal differentiation. This model allowed us to eliminate experimental variability due to donor genetic differences and transfection of the reprogramming factors such as copy number and integration site. In this study we demonstrated that early passage PTC iPSCs and TTF iPSCs expressed low levels of renal progenitor genes and high levels of pluripotency-associated genes, and the transcriptional levels of these genes were not significantly different between PTC iPSCs and TTF iPSCs. We used ChIP-seq of H3K4me3, H3K27me3, H3K36me3 and global DNA methylation profiles of PTC iPSCs and TTF iPSCs to demonstrate that global epigenetic marks were not different between the cells from the two different sets of tissue samples. There were also no epigenetic differences observed when kidney developmental genes and pluripotency-associated genes were closely examined. We did observe that during differentiation to renal progenitor cells the PTC iPSC-derived renal cells expressed higher levels of three renal progenitor genes compared to progenitors derived from TTF iPSCs but the underlying DNA methylation and histone methylation patterns did not suggest an epigenetic memory basis for this.

Mechanisms of ion transport regulation by HNF1β in the kidney: beyond transcriptional regulation of channels and transporters

Hepatocyte nuclear factor 1β (HNF1β) is a transcription factor essential for the development and function of the kidney. Mutations in and deletions of HNF1β cause autosomal dominant tubule interstitial kidney disease (ADTKD) subtype HNF1β, which is characterized by renal cysts, diabetes, genital tract malformations, and neurodevelopmental disorders. Electrolyte disturbances including hypomagnesemia, hyperuricemia, and hypocalciuria are common in patients with ADTKD-HNF1β. Traditionally, these electrolyte disturbances have been attributed to HNF1β-mediated transcriptional regulation of gene networks involved in ion transport in the distal part of the nephron including FXYD2, CASR, KCNJ16, and FXR. In this review, we propose additional mechanisms that may contribute to the electrolyte disturbances observed in ADTKD-HNF1β patients. Firstly, kidney development is severely affected in Hnf1b-deficient mice. HNF1β is required for nephron segmentation, and the absence of the transcription factor results in rudimentary nephrons lacking mature proximal tubule, loop of Henle, and distal convoluted tubule cluster. In addition, HNF1β is proposed to be important for apical-basolateral polarity and tight junction integrity in the kidney. Interestingly, cilia formation is unaffected by Hnf1b defects in several models, despite the HNF1β-mediated transcriptional regulation of many ciliary genes. To what extent impaired nephron segmentation, apical-basolateral polarity, and cilia function contribute to electrolyte disturbances in HNF1β patients remains elusive. Systematic phenotyping of Hnf1b mouse models and the development of patient-specific kidney organoid models will be essential to advance future HNF1β research.

Decellularization of porcine kidney with submicellar concentrations of SDS results in the retention of ECM proteins required for the adhesion and maintenance of human adult renal epithelial cells

When decellularizing kidneys, it is important to maintain the integrity of the acellular extracellular matrix (ECM), including associated adhesion proteins and growth factors that allow recellularized cells to adhere and migrate according to ECM specificity. Kidney decellularization requires the ionic detergent sodium dodecyl sulfate (SDS); however, this results in a loss of ECM proteins important for cell adherence, migration, and growth, particularly glycosaminoglycan (GAG)-associated proteins. Here, we demonstrate that using submicellar concentrations of SDS results in a greater retention of structural proteins, GAGs, growth factors, and cytokines. When porcine kidney ECM scaffolds were recellularized using human adult primary renal epithelial cells (RECs), the ECM promoted cell survival and the uniform distribution of cells throughout the ECM. Cells maintained the expression of mature renal epithelial markers but did not organize on the ECM, indicating that mature cells are unable to migrate to specific locations on ECM scaffolds.

DGAT2 Inhibition Potentiates Lipid Droplet Formation To Reduce Cytotoxicity in APOL1 Kidney Risk Variants

BACKGROUND

Two variants in the gene encoding apolipoprotein L1 (APOL1) that are highly associated with African ancestry are major contributors to the large racial disparity in rates of human kidney disease. We previously demonstrated that recruitment of APOL1 risk variants G1 and G2 from the endoplasmic reticulum to lipid droplets leads to reduced APOL1-mediated cytotoxicity in human podocytes.

METHODS

We used CRISPR-Cas9 gene editing of induced pluripotent stem cells to develop human-derived APOL1G0/G0 and APOL1G2/G2 kidney organoids on an isogenic background, and performed bulk RNA sequencing of organoids before and after treatment with IFN-γ. We examined the number and distribution of lipid droplets in response to treatment with inhibitors of diacylglycerol O-acyltransferases 1 and 2 (DGAT1 and DGAT2) in kidney cells and organoids.

RESULTS

APOL1 was highly upregulated in response to IFN-γ in human kidney organoids, with greater increases in organoids of high-risk G1 and G2 genotypes compared with wild-type (G0) organoids. RNA sequencing of organoids revealed that high-risk APOL1G2/G2 organoids exhibited downregulation of a number of genes involved in lipogenesis and lipid droplet biogenesis, as well as upregulation of genes involved in fatty acid oxidation. There were fewer lipid droplets in unstimulated high-risk APOL1G2/G2 kidney organoids than in wild-type APOL1G0/G0 organoids. Whereas DGAT1 inhibition reduced kidney organoid lipid droplet number, DGAT2 inhibition unexpectedly increased organoid lipid droplet number. DGAT2 inhibition promoted the recruitment of APOL1 to lipid droplets, with associated reduction in cytotoxicity.

CONCLUSIONS

Lipogenesis and lipid droplet formation are important modulators of APOL1-associated cytotoxicity. Inhibition of DGAT2 may offer a potential therapeutic strategy to attenuate cytotoxic effects of APOL1 risk variants.

Multidisciplinary approaches for elucidating genetics and molecular pathogenesis of urinary tract malformations

Advances in clinical diagnostics and molecular tools have improved our understanding of the genetically heterogeneous causes underlying congenital anomalies of kidney and urinary tract (CAKUT). However, despite a sharp incline of CAKUT reports in the literature within the past 2 decades, there remains a plateau in the genetic diagnostic yield that is disproportionate to the accelerated ability to generate robust genome-wide data. Explanations for this observation include (i) diverse inheritance patterns with incomplete penetrance and variable expressivity, (ii) rarity of single-gene drivers such that large sample sizes are required to meet the burden of proof, and (iii) multigene interactions that might produce either intra- (e.g., copy number variants) or inter- (e.g., effects in trans) locus effects. These challenges present an opportunity for the community to implement innovative genetic and molecular avenues to explain the missing heritability and to better elucidate the mechanisms that underscore CAKUT. Here, we review recent multidisciplinary approaches at the intersection of genetics, genomics, in vivo modeling, and in vitro systems toward refining a blueprint for overcoming the diagnostic hurdles that are pervasive in urinary tract malformation cohorts. These approaches will not only benefit clinical management by reducing age at molecular diagnosis and prompting early evaluation for comorbid features but will also serve as a springboard for therapeutic development.

From NAFLD to MAFLD: Aligning Translational In Vitro Research to Clinical Insights

Although most same-stage non-alcoholic fatty liver disease (NAFLD) patients exhibit similar histologic sequelae, the underlying mechanisms appear to be highly heterogeneous. Therefore, it was recently proposed to redefine NAFLD to metabolic dysfunction-associated fatty liver disease (MAFLD) in which other known causes of liver disease such as alcohol consumption or viral hepatitis do not need to be excluded. Revised nomenclature envisions speeding up and facilitating anti-MAFLD drug development by means of patient stratification whereby each subgroup would benefit from distinct pharmacological interventions. As human-based in vitro research fulfils an irrefutable step in drug development, action should be taken as well in this stadium of the translational path. Indeed, most established in vitro NAFLD models rely on short-term exposure to fatty acids and use lipid accumulation as a phenotypic benchmark. This general approach to a seemingly ambiguous disease such as NAFLD therefore no longer seems applicable. Human-based in vitro models that accurately reflect distinct disease subgroups of MAFLD should thus be adopted in early preclinical disease modeling and drug testing. In this review article, we outline considerations for setting up translational in vitro experiments in the MAFLD era and allude to potential strategies to implement MAFLD heterogeneity into an in vitro setting so as to better align early drug development with future clinical trial designs.

Organs-on-chip technology: a tool to tackle genetic kidney diseases

Chronic kidney disease (CKD) is a major healthcare burden that takes a toll on the quality of life of many patients. Emerging evidence indicates that a substantial proportion of these patients carry a genetic defect that contributes to their disease. Any effort to reduce the percentage of patients with a diagnosis of nephropathy heading towards kidney replacement therapies should therefore be encouraged. Besides early genetic screenings and registries, in vitro systems that mimic the complexity and pathophysiological aspects of the disease could advance the screening for targeted and personalized therapies. In this regard, the use of patient-derived cell lines, as well as the generation of disease-specific cell lines via gene editing and stem cell technologies, have significantly improved our understanding of the molecular mechanisms underlying inherited kidney diseases. Furthermore, organs-on-chip technology holds great potential as it can emulate tissue and organ functions that are not found in other, more simple, in vitro models. The personalized nature of the chips, together with physiologically relevant read-outs, provide new opportunities for patient-specific assessment, as well as personalized strategies for treatment. In this review, we summarize the major kidney-on-chip (KOC) configurations and present the most recent studies on the in vitro representation of genetic kidney diseases using KOC-driven strategies.

An episomal DNA vector platform for the persistent genetic modification of pluripotent stem cells and their differentiated progeny

The genetic modification of stem cells (SCs) is typically achieved using integrating vectors, whose potential integrative genotoxicity and propensity for epigenetic silencing during differentiation limit their application. The genetic modification of cells should provide sustainable levels of transgene expression, without compromising the viability of a cell or its progeny. We developed nonviral, nonintegrating, and autonomously replicating minimally sized DNA nanovectors to persistently genetically modify SCs and their differentiated progeny without causing any molecular or genetic damage. These DNA vectors are capable of efficiently modifying murine and human pluripotent SCs with minimal impact and without differentiation-mediated transgene silencing or vector loss. We demonstrate that these vectors remain episomal and provide robust and sustained transgene expression during self-renewal and targeted differentiation of SCs both in vitro and in vivo through embryogenesis and differentiation into adult tissues, without damaging their phenotypic characteristics.

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Nanovectors are used to engineer SCs efficiently, safely, and persistently

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Isogenic SC lines retain their capacity for self-renewal and pluripotency

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Nanovectors survive reprogramming and differentiation without loss or silencing

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Nanovectors are a universal genetic tool for the modification of any cell

Induced pluripotent stem cells derived cardiomyocytes from Duchenne Muscular Dystrophy patients in vitro

OBJECTIVE

This study aimed at the in vitro generation of DMD-cardiomyocytes from patient-specific induced pluripotent stem cells derived from a Pakistani patient for future work on DMD in vitro disease modeling and drug testing for efficacy and toxicity.

METHODS

This in vitro experimental study was carried out from December 2018 to January 2019 at Stem Cells and Regenerative Medicine Lab (SCRML) at Dow Research Institute of Biotechnology and Biomedical Sciences (DRIBBS), Dow University of Health Sciences (DUHS) Urine derived DMD-iPSCs were used which had been generated previously from a Pakistani DMD patient who had been selected through non-random purposive sampling. These were differentiated towards cardiomyocytes using Cardiomyocytes Differentiation media having specified growth factors and then the molecular characterization of the differentiated cells was done using immunofluorescence.

RESULTS

Pakistani patient's DMD-Cardiomyocytes were generated and their identity was confirmed by positive immunofluorescence for the expression of cardiac markers NKX2-5 and TNNT-2.

CONCLUSION

This study aimed for in vitro generation of DMD cardiomyocytes for future application in disease modeling, new drug testing for efficacy and toxicity, as well as for drug-testing for tailored personalized therapy. To the best of our knowledge, this was the first time DMD-Cardiomyocytes were generated from Pakistani DMD patients using their own induced pluripotent stem cells.

Identification of New Transcription Factors that Can Promote Pluripotent Reprogramming

BACKGROUND

Four transcription factors, Oct4, Sox2, Klf4, and c-Myc (the Yamanka factors), can reprogram somatic cells to induced pluripotent stem cells (iPSCs). Many studies have provided a number of alternative combinations to the non-Yamanaka factors. However, it is clear that many additional transcription factors that can generate iPSCs remain to be discovered.

METHODS

The chromatin accessibility and transcriptional level of human embryonic stem cells and human urine cells were compared by Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) and RNA sequencing (RNA-seq) to identify potential reprogramming factors. Selected transcription factors were employed to reprogram urine cells, and the reprogramming efficiency was measured. Urine-derived iPSCs were detected for pluripotency by Immunofluorescence, quantitative polymerase chain reaction, RNA sequencing and teratoma formation test. Finally, we assessed the differentiation potential of the new iPSCs to cardiomyocytes in vitro.

RESULTS

ATAC-seq and RNA-seq datasets predicted TEAD2, TEAD4 and ZIC3 as potential factors involved in urine cell reprogramming. Transfection of TEAD2, TEAD4 and ZIC3 (in the presence of Yamanaka factors) significantly improved the reprogramming efficiency of urine cells. We confirmed that the newly generated iPSCs possessed pluripotency characteristics similar to normal H1 embryonic stem cells. We also confirmed that the new iPSCs could differentiate to functional cardiomyocytes.

CONCLUSIONS

In conclusion, TEAD2, TEAD4 and ZIC3 can increase the efficiency of reprogramming human urine cells into iPSCs, and provides a new stem cell sources for the clinical application and modeling of cardiovascular disease.

An Overview on Promising Somatic Cell Sources Utilized for the Efficient Generation of Induced Pluripotent Stem Cells

Human induced Pluripotent Stem Cells (iPSCs) have enormous potential in understanding developmental biology, disease modeling, drug discovery, and regenerative medicine. The initial human iPSC studies used fibroblasts as a starting cell source to reprogram them; however, it has been identified to be a less appealing somatic cell source by numerous studies due to various reasons. One of the important criteria to achieve efficient reprogramming is determining an appropriate starting somatic cell type to induce pluripotency since the cellular source has a major influence on the reprogramming efficiency, kinetics, and quality of iPSCs. Therefore, numerous groups have explored various somatic cell sources to identify the promising sources for reprogramming into iPSCs with different reprogramming factor combinations. This review provides an overview of promising easily accessible somatic cell sources isolated in non-invasive or minimally invasive manner such as keratinocytes, urine cells, and peripheral blood mononuclear cells used for the generation of human iPSCs derived from healthy and diseased subjects. Notably, iPSCs generated from one of these cell types derived from the patient will offer ethical and clinical advantages. In addition, these promising somatic cell sources have the potential to efficiently generate bona fide iPSCs with improved reprogramming efficiency and faster kinetics. This knowledge will help in establishing strategies for safe and efficient reprogramming and the generation of patient-specific iPSCs from these cell types.

Function and Regulation of the Epithelial Na+ Channel ENaC

The Epithelial Na⁺ Channel, ENaC, comprised of 3 subunits (αβγ, or sometimes δβγENaC), plays a critical role in regulating salt and fluid homeostasis in the body. It regulates fluid reabsorption into the blood stream from the kidney to control blood volume and pressure, fluid absorption in the lung to control alveolar fluid clearance at birth and maintenance of normal airway surface liquid throughout life, and fluid absorption in the distal colon and other epithelial tissues. Moreover, recent studies have also revealed a role for sodium movement via ENaC in nonepithelial cells/tissues, such as endothelial cells in blood vessels and neurons. Over the past 25 years, major advances have been made in our understanding of ENaC structure, function, regulation, and role in human disease. These include the recently solved three-dimensional structure of ENaC, ENaC function in various tissues, and mutations in ENaC that cause a hereditary form of hypertension (Liddle syndrome), salt-wasting hypotension (PHA1), or polymorphism in ENaC that contributes to other diseases (such as cystic fibrosis). Moreover, great strides have been made in deciphering the regulation of ENaC by hormones (e.g., the mineralocorticoid aldosterone, glucocorticoids, vasopressin), ions (e.g., Na⁺ ), proteins (e.g., the ubiquitin-protein ligase NEDD4-2, the kinases SGK1, AKT, AMPK, WNKs & mTORC2, and proteases), and posttranslational modifications [e.g., (de)ubiquitylation, glycosylation, phosphorylation, acetylation, palmitoylation]. Characterization of ENaC structure, function, regulation, and role in human disease, including using animal models, are described in this article, with a special emphasis on recent advances in the field. © 2021 American Physiological Society. Compr Physiol 11:1-29, 2021.

A Concise Review on Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Personalized Regenerative Medicine

The induced pluripotent stem cells (iPSCs) are derived from somatic cells by using reprogramming factors such as Oct4, Sox2, Klf4, and c-Myc (OSKM) or Oct4, Sox2, Nanog and Lin28 (OSNL). They resemble embryonic stem cells (ESCs) and have the ability to differentiate into cell lineage of all three germ-layer, including cardiomyocytes (CMs). The CMs can be generated from iPSCs by inducing embryoid bodies (EBs) formation and treatment with activin A, bone morphogenic protein 4 (BMP4), and inhibitors of Wnt signaling. However, these iPSC-derived CMs are a heterogeneous population of cells and require purification and maturation to mimic the in vivo CMs. The matured CMs can be used for various therapeutic purposes in regenerative medicine by cardiomyoplasty or through the development of tissue-engineered cardiac patches. In recent years, significant advancements have been made in the isolation of iPSC and their differentiation, purification, and maturation into clinically usable CMs. Newer small molecules have also been identified to substitute the reprogramming factors for iPSC generation as well as for direct differentiation of somatic cells into CMs without an intermediary pluripotent state. This review provides a concise update on the generation of iPSC-derived CMs and their application in personalized cardiac regenerative medicine. It also discusses the current limitations and challenges in the application of iPSC-derived CMs. Graphical abstract.

Exosomal MATN3 of Urine-Derived Stem Cells Ameliorates Intervertebral Disc Degeneration by Antisenescence Effects and Promotes NPC Proliferation and ECM Synthesis by Activating TGF-β

Objective

Low back pain (LBP) is one of the top three causes of disability in developed countries, and intervertebral disc degeneration (IDD) is a major contributor to LBP. In the process of IDD, there is a gradual decrease in nucleus pulposus cells (NPCs) and extracellular matrix (ECM). Exosomes are important exocrine mediators of stem cells that can act directly on cells for tissue repair and regeneration. In this study, we determined the antisenescence, cell proliferation promotion, and ECM modulation effects of human urine-derived stem cell (USC) exosomes (USC-exos) on degenerated intervertebral discs and explored the underlying mechanism.

Methods and Materials

USCs were identified by multipotent differentiation and flow cytometry for mesenchymal stem cell- (MSC-) specific surface protein markers. USC-exos were isolated from the conditioned medium of USCs by ultracentrifugation and then analyzed by transmission electron microscopy (TEM), particle size analysis, and western blotting (WB) for exosome marker proteins. The effects of USC-exos on NPC proliferation and ECM synthesis were assessed by Cell Counting Kit-8 (CCK-8), WB, and immunofluorescence (IF) analyses. The protein differences between normal and degenerative intervertebral discs were mined, and the temporal and spatial variations in matrilin-3 (MATN3) content were determined by WB and IF in the intervertebral disc tissues. The candidate molecules that mediated the function of USC-exos were screened out and confirmed by multiple assays. Meanwhile, the mechanism underlying the candidate protein in USC-exos-induced cell proliferation and regulation of ECM synthesis promoting the activities of NPCs was explored. In addition, the effects of USC-exos on ameliorating intervertebral disc degeneration (IVD) in mice were examined by assessing computed tomography (CT), magnetic resonance imaging (MRI), and histological analyses.

Results

The flow cytometry results showed that USCs were positive for CD29, CD44, and CD73, which are USC surface-specific markers, but negative for CD34 and CD45. In addition, USCs showed osteogenic, adipogenic, and chondrogenic differentiation potential. USC-exos exhibited a cup-shaped morphology, with a mean diameter of 49.7 ± 7.3 nm, and were positive for CD63 and TSG101 and negative for calnexin. USC-exos could promote NPC proliferation and ECM synthesis. The protein content of the matrilin family was significantly reduced in degenerative intervertebral discs, and the decrease in MATN3 was the most significant. USC-exos were found to be rich in MATN3 protein, and exosomal MATN3 was required for USC-exos-induced promotion of NPC proliferation and ECM synthesis, as well as alleviation of intervertebral disc degeneration in IVD rats. In addition, the effects of MATN3 in USC-exos were demonstrated to be achieved by activating TGF-β, which elevated the phosphorylation level of SMAD and AKT.

Conclusions

Our study suggests that reduced MATN3 can be considered a characteristic of intervertebral disc degeneration. USC-exos may represent a potentially effective agent for alleviating intervertebral disc degeneration by promoting NPC proliferation and ECM synthesis by transferring the MATN3 protein.

Bioengineered Kidney Models: Methods and Functional Assessments

Investigations into bioengineering kidneys have been extensively conducted owing to their potential for preclinical assays and regenerative medicine. Various approaches and methods have been developed to improve the structure and function of bioengineered kidneys. Assessments of functional properties confirm the adequacy of bioengineered kidneys for multipurpose translational applications. This review is to summarize the studies performed in kidney bioengineering in the past decade. We identified 84 original articles from PubMed and Mendeley with keywords of kidney organoid or kidney tissue engineering. Those were categorized into 5 groups based on their approach: de-/recellularization of kidney, reaggregation of kidney cells, kidney organoids, kidney in scaffolds, and kidney-on-a-chip. These models were physiologically assessed by filtration, tubular reabsorption/secretion, hormone production, and nephrotoxicity. We found that bioengineered kidney models have been developed from simple cell cultures to multicellular systems to recapitulate kidney function and diseases. Meanwhile, only about 50% of these studies conducted functional assessments on their kidney models. Factors including cell composition and organization are likely to alter the applicability of physiological assessments in bioengineered kidneys. Combined with recent technologies, physiological assessments importantly contribute to the improvement of the bioengineered kidney model toward repairing and refunctioning the damaged kidney.

Mixing Cells for Vascularized Kidney Regeneration

The worldwide rise in prevalence of chronic kidney disease (CKD) demands innovative bio-medical solutions for millions of kidney patients. Kidney regenerative medicine aims to replenish tissue which is lost due to a common pathological pathway of fibrosis/inflammation and rejuvenate remaining tissue to maintain sufficient kidney function. To this end, cellular therapy strategies devised so far utilize kidney tissue-forming cells (KTFCs) from various cell sources, fetal, adult, and pluripotent stem-cells (PSCs). However, to increase engraftment and potency of the transplanted cells in a harsh hypoxic diseased environment, it is of importance to co-transplant KTFCs with vessel forming cells (VFCs). VFCs, consisting of endothelial cells (ECs) and mesenchymal stem-cells (MSCs), synergize to generate stable blood vessels, facilitating the vascularization of self-organizing KTFCs into renovascular units. In this paper, we review the different sources of KTFCs and VFCs which can be mixed, and report recent advances made in the field of kidney regeneration with emphasis on generation of vascularized kidney tissue by cell transplantation.

Clinical Integration of Genome Diagnostics for Congenital Anomalies of the Kidney and Urinary Tract

Revolutions in genetics, epigenetics, and bioinformatics are currently changing the outline of diagnostics and clinical medicine. From a nephrologist's perspective, individuals with congenital anomalies of the kidney and urinary tract (CAKUT) are an important patient category: not only is CAKUT the predominant cause of kidney failure in children and young adults, but the strong phenotypic and genotypic heterogeneity of kidney and urinary tract malformations has hampered standardization of clinical decision making until now. However, patients with CAKUT may benefit from precision medicine, including an integrated diagnostics trajectory, genetic counseling, and personalized management to improve clinical outcomes of developmental kidney and urinary tract defects. In this review, we discuss the present understanding of the molecular etiology of CAKUT and the currently available genome diagnostic modalities in the clinical care of patients with CAKUT. Finally, we discuss how clinical integration of findings from large-scale genetic, epigenetic, and gene-environment interaction studies may improve the prognosis of all individuals with CAKUT.

Urine-derived stem/progenitor cells: A focus on their characterization and potential

Cell therapy, i.e., the use of cells to repair an affected tissue or organ, is at the forefront of regenerative and personalized medicine. Among the multiple cell types that have been used for this purpose [including adult stem cells such as mesenchymal stem cells or pluripotent stem cells], urine-derived stem cells (USCs) have aroused interest in the past years. USCs display classical features of mesenchymal stem cells such as differentiation capacity and immunomodulation. Importantly, they have the main advantage of being isolable from one sample of voided urine with a cheap and unpainful procedure, which is broadly applicable, whereas most adult stem cell types require invasive procedure. Moreover, USCs can be differentiated into renal cell types. This is of high interest for renal cell therapy-based regenerative approaches. This review will firstly describe the isolation and characterization of USCs. We will specifically present USC phenotype, which is not an object of consensus in the literature, as well as detail their differentiation capacity. In the second part of this review, we will present and discuss the main applications of USCs. These include use as a substrate to generate human induced pluripotent stem cells, but we will deeply focus on the use of USCs for cell therapy approaches with a detailed analysis depending on the targeted organ or system. Importantly, we will also focus on the applications that rely on the use of USC-derived products such as microvesicles including exosomes, which is a strategy being increasingly employed. In the last section, we will discuss the remaining barriers and challenges in the field of USC-based regenerative medicine.

The FGF, TGFβ and WNT axis Modulate Self-renewal of Human SIX2+ Urine Derived Renal Progenitor Cells

Human urine is a non-invasive source of renal stem cells with regeneration potential. Urine-derived renal progenitor cells were isolated from 10 individuals of both genders and distinct ages. These renal progenitors express pluripotency-associated proteins- TRA-1-60, TRA-1-81, SSEA4, C-KIT and CD133, as well as the renal stem cell markers -SIX2, CITED1, WT1, CD24 and CD106. The transcriptomes of all SIX2⁺ renal progenitors clustered together, and distinct from the human kidney biopsy-derived epithelial proximal cells (hREPCs). Stimulation of the urine-derived renal progenitor cells (UdRPCs) with the GSK3β-inhibitor (CHIR99021) induced differentiation. Transcriptome and KEGG pathway analysis revealed upregulation of WNT-associated genes- AXIN2, JUN and NKD1. Protein interaction network identified JUN- a downstream target of the WNT pathway in association with STAT3, ATF2 and MAPK1 as a putative negative regulator of self-renewal. Furthermore, like pluripotent stem cells, self-renewal is maintained by FGF2-driven TGFβ-SMAD2/3 pathway. The urine-derived renal progenitor cells and the data presented should lay the foundation for studying nephrogenesis in human.