Preclinical and Clinical Studies on the Use of Extracellular Vesicles Derived from Mesenchymal Stem Cells in the Treatment of Chronic Wounds.

To date, the widespread implementation of therapeutic strategies for the treatment of chronic wounds, including debridement, infection control, and the use of grafts and various dressings, has been time-consuming and accompanied by many challenges, with definite success not yet achieved. Extensive studies on mesenchymal stem cells (MSCs) have led to suggestions for their use in treating various diseases. Given the existing barriers to utilizing such cells and numerous pieces of evidence indicating the crucial role of the paracrine signaling system in treatments involving MSCs, extracellular vesicles (EVs) derived from these cells have garnered significant attention in treating chronic wounds in recent years. This review begins with a general overview of current methods for chronic wound treatment, followed by an exploration of EV structure, biogenesis, extraction methods, and characterization. Subsequently, utilizing databases such as Google Scholar, PubMed, and ScienceDirect, we have explored the latest findings regarding the role of EVs in the healing of chronic wounds, particularly diabetic and burn wounds. In this context, the role and mode of action of these nanoparticles in healing chronic wounds through mechanisms such as oxygen level elevation, oxidative stress damage reduction, angiogenesis promotion, macrophage polarization assistance, etc., as well as the use of EVs as carriers for engineered nucleic acids, have been investigated. The upcoming challenges in translating EV-based treatments for healing chronic wounds, along with possible approaches to address these challenges, are discussed. Additionally, clinical trial studies in this field are also covered.

Enriched human embryonic stem cells-derived CD133+, CD24+ renal progenitors engraft and restore function in a gentamicin-induced kidney injury in mice.

Introduction: Acute kidney injury (AKI) is a common health problem that leads to high morbidity and potential mortality. The failure of conventional treatments to improve forms of this condition highlights the need for innovative and effective treatment approaches. Regenerative therapies with Renal Progenitor Cells (RPCs) have been proposed as a promising new strategy. A growing body of evidence suggests that progenitor cells differentiated from different sources, including human embryonic stem cells (hESCs), can effectively treat AKI. Methods: Here, we describe a method for generating RPCs and directed human Embryoid Bodies (EBs) towards CD133+CD24+ renal progenitor cells and evaluate their functional activity in alleviating AKI. Results: The obtained results show that hESCs-derived CD133+CD24+ RPCs can engraft into damaged renal tubules and restore renal function and structure in mice with gentamicin-induced kidney injury, and significantly decrease blood urea nitrogen levels, suppress oxidative stress and inflammation, and attenuate histopathological disturbances, including tubular necrosis, tubular dilation, urinary casts, and interstitial fibrosis. Conclusion: The results suggest that RPCs have a promising regenerative potential in improving renal disease and can lay the foundation for future cell therapy and disease modeling.

Great potential of renal progenitor cells in kidney: From the development to clinic.

The mammalian renal organ represents a pinnacle of complexity, housing functional filtering units known as nephrons. During embryogenesis, the depletion of niches containing renal progenitor cells (RPCs) and the subsequent incapacity of adult kidneys to generate new nephrons have prompted the formulation of protocols aimed at isolating residual RPCs from mature kidneys and inducing their generation from diverse cell sources, notably pluripotent stem cells. Recent strides in the realm of regenerative medicine and the repair of tissues using stem cells have unveiled critical signaling pathways essential for the maintenance and generation of human RPCs in vitro. These findings have ushered in a new era for exploring novel strategies for renal protection. The present investigation delves into potential transcription factors and signaling cascades implicated in the realm of renal progenitor cells, focusing on their protection and differentiation. The discourse herein elucidates contemporary research endeavors dedicated to the acquisition of progenitor cells, offering crucial insights into the developmental mechanisms of these cells within the renal milieu and paving the way for the formulation of innovative treatment modalities.

Autophagy-induced mesenchymal stem cell-derived extracellular vesicles ameliorated renal fibrosis in an in vitro model.

Introduction: Chronic and progressive damage to the kidney by inflammatory processes, may lead to an increase in the extracellular matrix production, a condition known as renal fibrosis. The current study aims to evaluate if the extracellular vesicles (EVs) derived from autophagic adipose-derived mesenchymal stem cells (ADMSCs) can reduce the inflammation and extracellular matrix accumulation in damaged kidney tissue. Methods: Autophagy was induced in ADMSCs using 2µM concentration curcumin and was confirmed by evaluating LC3B, ATG7, and Beclin1 using real-time polymerase chain reaction (PCR) and Western blot. An in vitro renal fibrotic model was established in HEK-293 cells exposed to H2O2 (0.8mM) for 24 and 72 hours. The fibrotic model was confirmed through evaluation of collagen I, transforming growth factor-beta 1 (TGF-ß1), E-cadherin, and vimentin genes expression using real-time PCR, collagen I protein by ELISA. After induction of fibrosis for 24 and 72 hours, the HEK cells were treated with NEVs (non-autophagy EVs) (50µM) or AEVs (autophagy EVs) (50µM) at 48, 96, and 124 hours, and then the samples were collected at 72 and 148 hours. Expression of collagen I, TGF-ß1, E-cadherin, and vimentin Genes was evaluated via RT-PCR, and protein levels of IL1, TNF-α, IL4, IL10 using ELISA. Results: Induction of autophagy using curcumin (2µM) for 24 hours significantly increased LC3B, Beclin1, and ATG7 in the ADMSCs. Upregulation in anti-fibrotic (E-cadherin) and anti-inflammatory (IL4, IL10) gene expression was significantly different in the fibrotic model treated by AEVs compared to NEVs. Also, the downregulation of fibrotic (TGF-ß1, vimentin, collagen I) and pro-inflammatory (IL1, TNFα) gene expression was significantly different in AEVs compared with those treated by NEVs. Conclusion: Our findings suggest that AEVs can be considered as a therapeutic modality for renal fibrosis in the future.

Potential of Autologous Adipose-Derived Mesenchymal Stem Cells in Peritoneal Fibrosis: A Pilot Study.

BACKGROUND: We aimed to determine the effects of systemic therapy with autologous adipose tissue derived mesenchymal stem cells (AD-MSCs) on different parameters of peritoneal function and inflammation in peritoneal dialysis (PD) patients. METHODS: We enrolled nine PD patients with ultrafiltration failure (UFF). Patients received 1.2±0.1×106 cell/kg of AD-MSCs via cubital vein and were then followed for six months at time points of baseline, 3, 6, 12, 16 and 24 weeks after infusion. UNI-PET was performed for assessment of peritoneal characteristics at baseline and weeks 12 and 24. Systemic and peritoneal levels of tumor necrosis factor α (TNF-α), interleukin-6(IL-6), IL-2 and CA125 (by ELISA) and gene expression levels of transforming growth factor beta (TGF-ß), smooth muscle actin (𝛼-SMA) and fibroblast-specific protein-1 (FSP-1) in PD effluent derived cells (by quantitative real-time PCR) were measured at baseline and weeks 3, 6, 12, 16 and 24. RESULTS: Slight improvement was observed in the following UF capacity indices: free water transport (FWT, 32%), ultrafiltration - small pore (UFSP, 18%), ultrafiltration total (UFT, 25%), osmotic conductance to glucose (OCG, 25%), D/P creatinine (0.75 to 0.70), and Dt/D0 glucose (0.23 to 0.26). There was a slight increase in systemic and peritoneal levels of CA125 and a slight decrease in gene expression levels of TGF-ß, α-SMA and FSP-1 that was more prominent at week 12 and vanished by the end of the study. CONCLUSION: Our results for the first time showed the potential of MSCs for treatment of peritoneal damage in a clinical trial. Our results could be regarded as hypothesis suggestion and will need confirmation in future studies.

A biological and a mathematical model of SLE treated by mesenchymal stem cells covering all the stages of the disease.

In this study, we proposed a biological model explaining the progress of autoimmune activation along different stages of systemic lupus erythematosus (SLE). For any upcoming stage of SLE, any new component is introduced, when it is added to the model. Particularly, the interaction of mesenchymal stem cells, with the components of the model, is specified in a way that both the inflammatory and anti-inflammatory functions of these cells would be covered. The biological model is then recapitulated to a model with less complexity that explains the main features of the problem. Later, a 7th-order mathematical model for SLE is proposed, based on this simplified model. Finally, the range of validity of the proposed mathematical model was assessed. For this purpose, we simulated the model and analyzed the simulation results in case of some known behaviors of the disease, such as tolerance breach, the appearance of systemic inflammation, development of clinical signs, and occurrence of flares and improvements. The model was able to reproduce these events, qualitatively.

The expression of fibrosis-related genes is elevated in doxorubicin-induced senescent human dermal fibroblasts, but their secretome does not trigger a paracrine fibrotic response in non-senescent cells.

Tissue fibrosis is associated with the aging process of most of our organs, and organ aging correlates with the chronic accumulation of senescent cells. Fibrosis occurs when fibroblasts proliferate and deposit pathological amounts of extracellular matrix (ECM), leading to progressive tissue scarring and organ dysfunction. Fibroblasts play a key role in fibrosis, especially in the skin where fibroblasts are the most abundant cell type in the dermis and are mainly responsible for the synthesis of ECM. This study aims to investigate how senescent fibroblasts and their secretome influence dermal fibrosis. Here we used human dermal fibroblasts (HDFs) treated with doxorubicin (doxo) to induce senescence. The senescent phenotype of these stress-induced premature senescent (SIPS) cells was confirmed with several markers. The expression of pro-fibrotic genes was quantified and finally, the impact of their secretome on the fibrotic response of non-senescent fibroblasts was assessed. Doxorubicin treatment, induced senescence in fibroblasts which has been confirmed with elevated senescence-associated ß- galactosidase (SA-ß-gal) activity, absence of BrdU incorporation, upregulation of p21, and loss of Lamin b1. Expression levels of the pro-fibrotic genes ACTA2 and FN1 increased in SIPS cells, but in contrast to studies using lung fibroblasts the secretome of these cells failed to induce a paracrine fibrotic response in non-senescent cells. In general, these results suggest that these senescent cells are potentially profibrotic, and their accumulation can trigger fibrosis in organs.

Human umbilical cord serum as an alternative to fetal bovine serum for in vitro expansion of umbilical cord mesenchymal stromal cells.

In the use of bovine fetal serum (FBS) there is concern about the possibility of disease transmission from animal to human. Therefore, it seems necessary to create culture conditions free of animal serum, especially in cell therapy. The aim of this study was to evaluate the feasibility of replacing human umbilical cord serum (hUCS) with FBS for in vitro expansion of umbilical cord mesenchymal stromal/stem cells (UC-MSCs). Here, UC-MSCs were cultured for five days in media supplemented either by hUCS or commercial FBS (Gibco and HyClone) to compare their viability, proliferation, morphology, Immunophenotype and differentiation potential. Our data shows that use of 5% and/or 10% hUCS, resulted in a tenfold increase in the number of MSCs; While in the presence of commercial FBS, this figure reached a maximum of five times. Notably, the rate of cell proliferation in the group containing 2% hUCS was the same as the groups containing 10% commercial FBS. Furthermore, there was no significant difference between groups in terms of viability, surface markers, and multilineage differentiation potential. These results demonstrated that hUCS can efficiently replace FBS for the routine culture of MSCs and can be used ideally in manufacturing process of UC-MSCs in cell therapy industry.

Reduced inflammation following human endometrial stromal/stem cell injection into male Wistar rats with cisplatin-induced acute kidney injury.

Introduction: Inflammation is one of the most important mechanisms involved in cisplatin-induced acute kidney injury (AKI). Mesenchymal stromal/stem cells (MSCs) exhibit anti-inflammatory and immunomodulatory abilities. Human endometrial stromal/stem cells (hEnSCs) exhibit similar properties to MSCs. These cells secrete immunoregulators, so we investigated the inflammatory aspect of hEnSCs in the treatment of cisplatin-induced AKI in Wistar rats. Methods: Each group consisted of 6 male Wistar rats. Groups were as follows: sham, model (5 mg/kg cisplatin, IP), and treatment (1 million hEnSCs, IV, 3 hours after cisplatin). Renal function, histopathology, proliferation rate, infiltration of CD3+ T cell, and expression of Il-10 and cystatin c (Cst3) were assessed on day 5. DiI-labeled cells were tracked in kidney and liver on days 4 and 14. Results: HEnSC transplantation improved cisplatin-induced injuries such as renal dysfunction and tissue damage. The highest levels of pathologic scores and hyaline cast formation were observed in the model group while hEnSCs transplantation resulted in their reduction (154.00 ± 14.95, 8.00 ± 1.41 vs. 119.40 ± 5.43, 2.50 ± 1.05). The percentage of Ki-67 positive cells in the treatment group increased while cisplatin decreased proliferation (39.91 ± 5.33 vs. 23.91 ± 3.57 in glomeruli and 39.07 ± 2.95 vs. 16.61 ± 3.25 in tubules). The expression of Cst3 and Il-10 was higher in the model and treatment groups, respectively. DiI-labeled cells were observed in the renal tubules and liver lobes on days 4 and 14. Conclusion: HEnSCs may ameliorate cisplatin-induced AKI through anti-inflammatory and immunomodulatory effects and/or through paracrine effects.

Kidney development and function: ECM cannot be ignored.

The extracellular matrix (ECM) is an essential network entity surrounding and supporting cells to guarantee their physiological function and homeostasis. It is important to choose the most appropriate ECM for in vitro experiments of mammalian cells for tissue engineering and functional analyses. Although most studies have examined optimization of the correct ECM that can be used to assess mammalian cells, a comprehensive study has not been conducted. In this review, we present the factors to be taken into consideration when designing or optimizing an appropriate ECM for development and maintenance of kidney tissues and compare the previously reported ECMs.

Kidney organoids: current knowledge and future directions.

The kidney is a highly complex organ in the human body. Although creating an in vitro model of the human kidney is challenging, tremendous advances have been made in recent years. Kidney organoids are in vitro kidney models that are generated from stem cells in three-dimensional (3D) cultures. They exhibit remarkable degree of similarities with the native tissue in terms of cell type, morphology, and function. The establishment of 3D kidney organoids facilitates a mechanistic study of cell communications, and these organoids can be used for drug screening, disease modeling, and regenerative medicine applications. This review discusses the cellular complexity during in vitro kidney generation. We intend to highlight recent progress in kidney organoids and the applications of these relatively new technologies.

Treatment with human umbilical cord blood serum in a gentamicin-induced nephrotoxicity model in rats.

Sold under the brand name of Garamycin, gentamicin (GM) is an antibiotic in the category of aminoglycoside, that although does have many antibacterial properties, owing to several side effects, its consumption is confined. The current study is aimed at gauging the protective influences of human umbilical cord blood serum (hUCBS) on nephrotoxicity which is induced by GM. In this regard, in the present experimental design, twenty-eight male Wistar rats with the weights of 220 ± 20 g were categorized randomly into 4 groups of seven. The groups included GM (100 mg/kg), control as well as hUCBS at doses of one and two percent together with GM (100 mg/kg) for ten days in an intraperitoneal manner. Blood sampling was collected from the heart directly 24 h after the final injection for obtaining blood serum; the parameters of C-reactive protein (CRP), total oxidant status (TOS), interleukin (IL)-6, lactate dehydrogenase (LDH), total antioxidant capacity (TAC), creatinine (Cr), blood urea nitrogen (BUN), blood serum glutathione (GSH) were gauged in blood serum samples to evaluate renal function. Moreover, for histology, an examination of kidney tissue was performed. In comparison to those of the GM group, in the treatment group, hUCBS significantly decreased the levels of BUN, Cr, LDH, TOS, IL-6, and the CRP levels, and significantly increased the TAC and GSH levels. It was revealed that the treatment of the animals with hUCBS culminates in the reduction of GM' toxic impacts on the kidney.

Human Endometrial Stromal/Stem Cells Inhibit Apoptosis in Cisplatin-Induced Acute Kidney Injury in Male Wistar Rats.

OBJECTIVE: Acute kidney injury (AKI) is referred to as sudden decline in the function of kidney. Human endometrial stromal/stem cells (hEnSCs) are mesenchymal stem cell (MSC)-like cells, which are suitable candidates for regenerative medicine purposes, yet the effect of hEnSCs on cisplatin-induced AKI has not been studied; therefore, the present study was conducted to investigate this gap in the literature. MATERIALS AND METHODS: In this experimental study, hEnSCs were obtained from endometrial biopsy using collagenase I and were then cultured in DMEM/F12 medium. A total of 48 male Wistar rats (150-200 g) were classified into four groups: intact -receiving no treatment, model -receiving 5 mg/kg of body weight cisplatin, as well as phosphate-buffered saline (PBS) and cell -receiving either PBS or hEnSCs for three hours after cisplatin injection, respectively. Biochemical parameters, pathologic scores, apoptosis assay, Bcl-2 and Tnf-α expression were evaluated on day 5. RESULTS: On day 5 post-transplantation we observed that HEnSCs injection has led to a decrease in both blood urea nitrogen (BUN) and serum creatinine (SCr), compared to the model and PBS groups (0.82 ± 0.03 vs. 1.42 ± 0.06, 1.09 ± 0.05 mg/dl and 61.53 ± 3.07 vs. 116.60 ± 2.12, 112.00 ± 1.35 mg/dl, respectively). The highest levels of pathologic scores were observed in model and PBS groups, while hEnSCs transplantation resulted in a decrease in pathologic scores (149.10 ± 7.03, 141.50 ± 4.68 vs. 118 ± 2.16). HEnSCs significantly decreased the percentage of TUNELpositive cells in the cell group compared with model and PBS groups (20.37 ±. 3.37 vs. 33.67 ± 1.79, 31.53 ± 1.05 in glomeruli and 15.10 ± 1.47 vs. 42.33 ± 1.72, 39.23 ± 1.61 in tubules). In addition, HEnSCs resulted in upregulation of Bcl-2 and downregulation of Tnf-α in the cisplatin-induced AKI. CONCLUSION: Our results showed that injection of hEnSCs may improve AKI through lowering the amount of apoptosis in renal cells.

Immunomodulatory Activity of Human Bone Marrow and Adipose-Derived Mesenchymal Stem Cells Prolongs Allogenic Skin Graft Survival in Nonhuman Primates.

OBJECTIVE: In the present study, we examined the tolerance-inducing effects of human adipose-derived mesenchymal stem cells (hAD-MSCs) and bone marrow-derived MSCs (hBM-MSCs) on a nonhuman primate model of skin transplantation. MATERIALS AND METHODS: In this experimental study, allogenic and xenogeneic of immunomodulatory properties of human AD-MSCs and BM-MSCs were evaluated by mixed lymphocyte reaction (MLR) assays. Human MSCs were obtained from BM or AD tissues (from individuals of either sex with an age range of 35 to 65 years) and intravenously injected (2×106 MSCs/kg) after allogeneic skin grafting in a nonhuman primate model. The skin sections were evaluated by H and E staining for histopathological evaluations, particularly inflammation and rejection reaction of grafts after 96 hours of cell injection. At the mRNA and protein levels, cellular mediators of inflammation, such as CD4+IL-17+ (T helper 17; Th17) and CD4+INF-γ+ (T helper 1, Th1) cells, along with CD4+FoxP3+ cells (Treg), as the mediators of immunomodulation, were measured by RT-PCR and flow cytometry analyses. RESULTS: A significant Treg cells expansion was observed in MSCs-treated animals which reached the zenith at 24 hours and remained at a high concentration for 96 hours; however, Th1 and Th17 cells were significantly decreased. Our results showed that human MSCs significantly decrease Th1 and Th17 cell proliferation by decreasing interleukin-17 (IL-17) and interferon-γ (INF-γ) production and significantly increase Treg cell proliferation by increasing FoxP3 production. They also extend the allogenic skin graft survival in nonhuman primates. Histological evaluations showed no obvious presence of inflammatory cells or skin redness or even bulging after MSCs injection up to 96 hours, compared to the group without MSCs. There were no significant differences between hBM-MSCs and hAD-MSCs in terms of histopathological scores and inflammatory responses (P<0.05). CONCLUSION: It seems that MSCs could be regarded as a valuable immunomodulatory tool to reduce the use of immunosuppressive agents.

Promoting Maturation of Human Pluripotent Stem Cell-Derived Renal Microtissue by Incorporation of Endothelial and Mesenchymal Cells.

Directed differentiation of human pluripotent stem cells (hPSCs) uses a growing number of small molecules and growth factors required for in vitro generation of renal lineage cells. Although current protocols are relatively inefficient or expensive. The first objective of the present work was to establish a new differentiation protocol for generating renal precursors. We sought to determine if inducer of definitive endoderm 1 (IDE1), a cost-effective small molecule, can be used to replace activin A. Gene expression data showed significantly increased expressions of nephrogenic markers in cells differentiated with 20 nM IDE1 compared with cells differentiated with activin A. Thus, renal lineage cells could be generated by this alternative approach. Afterward, we determined whether coculture of endothelial and mesenchymal cells could increase the maturation of three-dimensional (3D) renal structures. For this purpose, we employed a 3D coculture system in which hPSC-derived kidney precursors were cocultured with endothelial cells (ECs) and mesenchymal stem cells (MSCs), hereafter named RMEM (renal microtissue derived from coculture of renal precursors with endothelial and mesenchymal stem cells). hPSC-derived kidney precursors were cultured either alone [renal microtissue (RM)] or in coculture with human umbilical vein endothelial cells and human bone marrow-derived mesenchymal stem cells at an approximate ratio of 10:7:2, respectively. Immunofluorescent staining showed expressions of kidney-specific markers synaptopodin, LTL, and E-cadherin, as well as CD31+ ECs that were distributed throughout the RMEMs. Quantitative real-time polymerase chain reaction analysis confirmed a significant increase in gene expressions of the renal-specific markers in RMEMs compared with RMs. These findings demonstrated that renal precursors cocultured with endothelial and MSCs showed greater maturity compared with RMs. Moreover, ex ovo transplantation induced further maturation in the RMEM constructs. Our novel approach enabled the generation of RMEM that could potentially be used in high-throughput drug screening and nephrotoxicology studies.

Human umbilical cord blood serum attenuates gentamicin-induced liver toxicity by restoring peripheral oxidative damage and inflammation in rats.

Gentamicin (GM) is an aminoglycoside antibiotic that despite its antibacterial effects, its use is restricted due to numerous side effects. The umbilical cord serum contains various biomolecules that have protective impacts on the damaged tissues. The aim of this study was to gauge the protective effect of human umbilical cord blood serum (hUCBS) on GM-induced hepatotoxicity. In this experimental study, 28 male Wistar rats, weighing 220 ± 20 g, were randomly categorized into 4 groups including control, GM (100 mg/kg), hUCBS at doses of 1 and 2% along with GM (100 mg/kg) for 10 days, intraperitoneally. Twenty-four hours after the last injection, direct blood sampling was taken from the heart to obtain blood serum and liver enzymes, inflammatory cytokines and liver tissue were examined for histology. GM causes necrosis and inflammation in liver tissue. Liver enzyme and inflammatory cytokine levels were significantly increased in the GM group. Human umbilical cord blood serum significantly decreased liver enzyme and inflammatory cytokines levels in the experimental groups compared to the GM group. GM causes liver damage such as the inflammation and necrosis in liver tissue. Treating the animals with hUCBS reduced the toxic effects of GM in the liver.

The Effect of Low-Power Laser Therapy on the TGF/ß Signaling Pathway in Chronic Kidney Disease: A Review.

Objective: The purpose of this study is to investigate the effects of low-power lasers on kidney disease by investigating several studies. Methods: A number of articles from 1998 to 2019 were chosen from the sources of PubMed, Scopus, and only the articles studying the effect of low-power lasers on kidney disease were investigated. Results: After reviewing the literature, 21 articles examining only the effects of low-power lasers on kidney disease were found. The results of these studies showed that the parameter of the lowpower laser would result in different outcomes. So, a low-power laser with various parameters can be effective in the treatment of kidney diseases such as acute kidney disease, diabetes, glomerulonephritis, nephrectomy, metabolic syndrome, and kidney fibrosis. Most studies have shown that low-power lasers can affect TGFß1 signaling which is the most important signaling in the treatment of renal fibrosis. Conclusion: Lasers can be effective in reducing or enhancing inflammatory responses, reducing fibrosis factors, and decreasing reactive oxygen species (ROS) levels in kidney disease and glomerular cell proliferation.

Cellular and Molecular Mechanisms of Kidney Development: From the Embryo to the Kidney Organoid.

Development of the metanephric kidney is strongly dependent on complex signaling pathways and cell-cell communication between at least four major progenitor cell populations (ureteric bud, nephron, stromal, and endothelial progenitors) in the nephrogenic zone. In recent years, the improvement of human-PSC-derived kidney organoids has opened new avenues of research on kidney development, physiology, and diseases. Moreover, the kidney organoids provide a three-dimensional (3D) in vitro model for the study of cell-cell and cell-matrix interactions in the developing kidney. In vitro re-creation of a higher-order and vascularized kidney with all of its complexity is a challenging issue; however, some progress has been made in the past decade. This review focuses on major signaling pathways and transcription factors that have been identified which coordinate cell fate determination required for kidney development. We discuss how an extensive knowledge of these complex biological mechanisms translated into the dish, thus allowed the establishment of 3D human-PSC-derived kidney organoids.