Protective actions of administered mesenchymal stem cells in acute kidney injury: relevance to clinical trials. Kidney Int Suppl (2011). 2011;1:103-106. [PMID: 25018910 PMCID: PMC4089688 DOI: 10.1038/kisup.2011.24]

Mesenchymal stromal cells with chimaeric antigen receptors for enhanced immunosuppression

Allogeneic mesenchymal stromal cells (MSCs) are a safe treatment option for many disorders of the immune system. However, clinical trials using MSCs have shown inconsistent therapeutic efficacy, mostly owing to MSCs providing insufficient immunosuppression in target tissues. Here we show that antigen-specific immunosuppression can be enhanced by genetically modifying MSCs with chimaeric antigen receptors (CARs), as we show for E-cadherin-targeted CAR-MSCs for the treatment of graft-versus-host disease in mice. CAR-MSCs led to superior T-cell suppression and localization to E-cadherin+ colonic cells, ameliorating the animals' symptoms and survival rates. On antigen-specific stimulation, CAR-MSCs upregulated the expression of immunosuppressive genes and receptors for T-cell inhibition as well as the production of immunosuppressive cytokines while maintaining their stem cell phenotype and safety profile in the animal models. CAR-MSCs may represent a widely applicable therapeutic technology for enhancing immunosuppression.

Adipose-derived Mesenchymal Stem Cells Therapy as a new Treatment Option for Diabetes Mellitus

The worldwide increase in the prevalence of diabetes mellitus has raised the demand for new therapeutic strategies targeting diabetic symptoms and its chronic complications. Among different treatment options for diabetes, adipose-derived mesenchymal stem cells (ADMSCs) therapy attract the most attention. The therapeutic effects of ADMSCs are based primarily on their paracrine release of immunomodulatory, anti-inflammatory, and trophic factors. Animal models of diabetes as well as human clinical trials have shown that ADMSCs can effectively facilitate endogenous β cell regeneration, preserve residual β cell mass, reduce islet graft rejection, regulate the immune system, and ultimately improve insulin sensitivity or ameliorate insulin resistance in peripheral tissues. Nevertheless, transplantation of mesenchymal stem cells is associated with certain risks; therefore recently much attention has been devoted to ADMSCs derivatives, such as exosomes or conditioned media, as therapeutic agents for the treatment of diabetes. Compared to ADMSCs, cell-free therapy has even better therapeutic potential. This narrative review summarizes recent outcomes and molecular mechanisms of ADMSCs action in the treatment for both type 1 DM and type 2 DM, as well as shows their feasibility, benefits, and current limitations.

Clinical Prospect of Mesenchymal Stromal/Stem Cell-Derived Extracellular Vesicles in Kidney Disease: Challenges and the Way Forward

Kidney disease is a growing public health problem worldwide, including both acute and chronic forms. Existing therapies for kidney disease target various pathogenic mechanisms; however, these therapies only slow down the progression of the disease rather than offering a cure. One of the potential and emerging approaches for the treatment of kidney disease is mesenchymal stromal/stem cell (MSC) therapy, shown to have beneficial effects in preclinical studies. In addition, extracellular vesicles (EVs) released by MSCs became a potent cell-free therapy option in various preclinical models of kidney disease due to their regenerative, anti-inflammatory, and immunomodulatory properties. However, there are scarce clinical data available regarding the use of MSC-EVs in kidney pathologies. This review article provides an outline of the renoprotective effects of MSC-EVs in different preclinical models of kidney disease. It offers a comprehensive analysis of possible mechanisms of action of MSC-EVs with an emphasis on kidney disease. Finally, on the journey toward the implementation of MSC-EVs into clinical practice, we highlight the need to establish standardized methods for the characterization of an EV-based product and investigate the adequate dosing, safety, and efficacy of MSC-EVs application, as well as the development of suitable potency assays.

Using adipose-derived mesenchymal stem cells to fight the metabolic complications of obesity: Where do we stand?

Obesity is a critical risk factor for the development of metabolic diseases, and its prevalence is increasing worldwide. Stem cell-based therapies have become a promising tool for therapeutic intervention. Among them are adipose-derived mesenchymal stem cells (ADMSCs), secreting numerous bioactive molecules, like growth factors, cytokines, and chemokines. Their unique features, including immunosuppressive and immunomodulatory properties, make them an ideal candidates for clinical applications. Numerous experimental studies have shown that ADMSCs can improve pancreatic islet cell viability and function, ameliorate hyperglycemia, improve insulin sensitivity, restore liver function, counteract dyslipidemia, lower pro-inflammatory cytokines, and reduce oxidative stress in the animal models. These results prompted scientists to use ADMSCs clinically. However, up to date, there have been few clinical studies or ongoing trails using ADMSCs to treat metabolic disorders such as type 2 diabetes mellitus (T2DM) or liver cirrhosis. Most human studies have implemented autologous ADMSCs with minimal risk of cellular rejection. Because the functionality of ADMSCs is significantly reduced in subjects with obesity and/or metabolic syndrome, their efficacy is questioned. ADMSCs transplantation may offer a potential therapeutic approach for the treatment of metabolic complications of obesity, but randomized controlled trials are required to establish their safety and efficacy in humans prior to routine clinical use.

Efficacy of umbilical cord mesenchymal stem cell transfusion for the treatment of severe AKI: a protocol for a randomised controlled trial

INTRODUCTION

Acute kidney injury (AKI) is a common and severe clinical problem that is associated with high mortality, a long hospital stays and high healthcare resource consumption. Approximately a quarter of AKI survivors will develop chronic kidney disease. Mesenchymal stem cells (MSCs) are multipotent stem cells with antiapoptotic, immunomodulatory, antioxidative and proangiogenic properties. Therefore, MSCs have been considered as a potential new therapy for the treatment of AKI. Several clinical trials have been performed, but the results have been inconsistent. This trial investigated whether MSCs can improve renal recovery and mortality in patients with severe AKI.

METHODS AND ANALYSIS

One hundred subjects suffering from severe AKI will participate in this patient-blinded, randomised, placebo-controlled, parallel design clinical trial. Participants will be randomly assigned to receive two doses of MSCs or placebo (saline) on days 0 and 7. Urinary biomarkers of renal injury and repair will be measured using commercially available ELISA kits. The main outcome measures are changes in renal function levels within the first 28 days following MSC infusion.

ETHICS AND DISSEMINATION

The study was approved by the Ethics Committee of the Chinese PLA General Hospital. The findings of the study will be disseminated through public and scientific channels.

TRIAL REGISTRATION NUMBER

NCT04194671.

When Origin Matters: Properties of Mesenchymal Stromal Cells From Different Sources for Clinical Translation in Kidney Disease

Advanced therapy medicinal products (ATMPs) offer new prospects to improve the treatment of conditions with unmet medical needs. Kidney diseases are a current major health concern with an increasing global prevalence. Chronic renal failure appears after many years of impairment, which opens a temporary window to apply novel therapeutic approaches to delay or halt disease progression. The immunomodulatory, anti-inflammatory, and pro-regenerative properties of mesenchymal stromal cells (MSCs) have sparked interest for their use in cell-based regenerative therapies. Currently, several early-phase clinical trials have been completed and many are ongoing to explore MSC safety and efficacy in a wide range of nephropathies. However, one of the current roadblocks to the clinical translation of MSC therapies relates to the lack of standardization and harmonization of MSC manufacturing protocols, which currently hinders inter-study comparability. Studies have shown that cell culture processing variables can have significant effects on MSC phenotype and functionality, and these are highly variable across laboratories. In addition, heterogeneity within MSC populations is another obstacle. Furthermore, MSCs may be isolated from several sources which adds another variable to the comparative assessment of outcomes. There is now a growing body of literature highlighting unique and distinctive properties of MSCs according to the tissue origin, and that characteristics such as donor, age, sex and underlying medical conditions may alter the therapeutic effect of MSCs. These variables must be taken into consideration when developing a cell therapy product. Having an optimal scale-up strategy for MSC manufacturing is critical for ensuring product quality while minimizing costs and time of production, as well as avoiding potential risks. Ideally, optimal scale-up strategies must be carefully considered and identified during the early stages of development, as making changes later in the bioprocess workflow will require re-optimization and validation, which may have a significant long-term impact on the cost of the therapy. This article provides a summary of important cell culture processing variables to consider in the scale-up of MSC manufacturing as well as giving a comprehensive review of tissue of origin-specific biological characteristics of MSCs and their use in current clinical trials in a range of renal pathologies.

Current advances of stem cell-based therapy for kidney diseases

Kidney diseases are a prevalent health problem around the world. Multidrug therapy used in the current routine treatment for kidney diseases can only delay disease progression. None of these drugs or treatments can reverse the progression to an end-stage of the disease. Therefore, it is crucial to explore novel therapeutics to improve patients’ quality of life and possibly cure, reverse, or alleviate the kidney disease. Stem cells have promising potentials as a form of regenerative medicine for kidney diseases due to their unlimited replication and their ability to differentiate into kidney cells in vitro. Mounting evidences from the administration of stem cells in an experimental kidney disease model suggested that stem cell-based therapy has therapeutic or renoprotective effects to attenuate kidney damage while improving the function and structure of both glomerular and tubular compartments. This review summarises the current stem cell-based therapeutic approaches to treat kidney diseases, including the various cell sources, animal models or in vitro studies. The challenges of progressing from proof-of-principle in the laboratory to widespread clinical application and the human clinical trial outcomes reported to date are also highlighted. The success of cell-based therapy could widen the scope of regenerative medicine in the future.

Administration of Donor-Derived Nonexpanded Adipose Stromal Vascular Fraction Attenuates Ischemia-Reperfusion Injury in Donation After Cardiac Death Rat Renal Transplantation

Donation after cardiac death (DCD) has become a potential source for transplantation organs. However, ischemia/reperfusion injury (IRI) induced by cardiac arrest has limited the use of DCD organs. Stromal vascular fraction (SVF) without the culturing step has been proposed as a safer and easier source for stem cell therapy, which has emerged as an attractive technology that could facilitate the recovery of renal function and structure from acute kidney injury induced by IRI after DCD renal transplantation. In this study, freshly isolated donor-derived SVF was identified and then delivered intra-arterially into the grafts in DCD rat renal transplantation. Administration of freshly isolated donor-derived SVF could significantly alleviate the IRI of renal grafts and enhance graft reparation by promoting graft cell proliferation and microvascularization in DCD renal transplantation. Moreover, results revealed that the oxidative stress in grafts was significantly alleviated with SVF treatment, and this might be attributed to the overexpression of antioxidative molecules including nuclear factor erythroid-related factor 2, superoxide dismutase-1, and heme oxygenase-1. In conclusion, our study demonstrated that the administration of freshly isolated donor-derived nonexpanded adipose SVF could attenuate IRI and protect the grafts after DCD rat renal transplantation.

Stem Cell Therapy for Microvascular Injury Associated with Ischemic Nephropathy

Ischemic nephropathy reflects progressive loss of kidney function due to large vessel atherosclerotic occlusive disease. Recent studies indicate that this process is characterized by microvascular rarefaction, increased tissue hypoxia and activation of inflammatory processes of tissue injury. This review summarizes the rationale and application of functional MR imaging to evaluate tissue oxygenation in human subjects that defines the limits of renal adaptation to reduction in blood flow, development of increasingly severe tissue hypoxia and recruitment of inflammatory injury pathways in ischemic nephropathy. Human mesenchymal stromal/stem cells (MSC) are capable of modifying angiogenic pathways and immune responses, but the potency of these effects vary between individuals and various clinical characteristics including age and chronic kidney disease and levels of hypoxia. We summarize recently completed first-in-human studies applying intrarenal infusion of autologous adipose-derived MSC in human subjects with ischemic nephropathy that demonstrate a rise in blood flow and reduction in tissue hypoxia consistent with partial repair of microvascular injury, even without restoring main renal arterial blood flow. Inflammatory biomarkers in the renal vein of post-stenotic kidneys fell after MSC infusion. These changes were associated with modest but significant dose-related increments in kidney function. These data provide support a role for autologous MSC in repair of microvascular injury associated with tissue hypoxia.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: A Potential Therapeutic Strategy for Acute Kidney Injury

Acute kidney injury (AKI) is a common and potential life-threatening disease in patients admitted to hospital, affecting 10%-15% of all hospitalizations and around 50% of patients in the intensive care unit. Severe, recurrent, and uncontrolled AKI may progress to chronic kidney disease or end-stage renal disease. AKI thus requires more efficient, specific therapies, rather than just supportive therapy. Mesenchymal stem cells (MSCs) are considered to be promising cells for cellular therapy because of their ease of harvesting, low immunogenicity, and ability to expand in vitro. Recent research indicated that the main therapeutic effects of MSCs were mediated by MSC-derived extracellular vesicles (MSC-EVs). Furthermore, compared with MSCs, MSC-EVs have lower immunogenicity, easier storage, no tumorigenesis, and the potential to be artificially modified. We reviewed the therapeutic mechanism of MSCs and MSC-EVs in AKI, and considered recent research on how to improve the efficacy of MSC-EVs in AKI. We also summarized and analyzed the potential and limitations of EVs for the treatment of AKI to provide ideas for future clinical trials and the clinical application of MSC-EVs in AKI.

Mesenchymal stromal cells to fight SARS-CoV-2: Taking advantage of a pleiotropic therapy

The devastating global impact of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has prompted scientists to develop novel strategies to fight Coronavirus Disease of 2019 (COVID-19), including the examination of pre-existing treatments for other viral infections in COVID-19 patients. This review provides a reasoned discussion of the possible use of Mesenchymal Stromal Cells (MSC) or their products as a treatment in SARS-CoV-2-infected patients. The main benefits and concerns of using this cellular therapy, guided by preclinical and clinical data obtained from similar pathologies will be reviewed. MSC represent a highly immunomodulatory cell population and their use may be safe according to clinical studies developed in other pathologies. Notably, four clinical trials and four case reports that have already been performed in COVID-19 patients obtained promising results. The clinical application of MSC in COVID-19 is very preliminary and further investigational studies are required to determine the efficacy of the MSC therapy. Nevertheless, these preliminary studies were important to understand the therapeutic potential of MSC in COVID-19. Based on these encouraging results, the United States Food and Drug Administration (FDA) authorized the compassionate use of MSC, but only in patients with Acute Respiratory Distress Syndrome (ARDS) and a poor prognosis. In fact, patients with severe SARS-CoV-2 can present infection and tissue damage in different organs, such as lung, heart, liver, kidney, gut and brain, affecting their function. MSC may have pleiotropic activities in COVID-19, with the capacity to fight inflammation and repair lesions in several organs.

Mesenchymal Stromal Cells in Solid Organ Transplantation

Over the past decade, the clinical application of mesenchymal stromal cells (MSCs) has generated growing enthusiasm as an innovative cell-based approach in solid organ transplantation (SOT). These expectations arise from a significant number of both transplant- and non-transplant-related experimental studies investigating the complex anti-inflammatory, immunomodulatory, and tissue-repair properties of MSCs. Promising preclinical results have prompted clinical trials using MSC-based therapy in SOT. In the present review, the general properties of MSCs are summarized, with a particular emphasis on MSC-mediated impact on the immune system and in the ischemic conditioning strategy. Next, we chronologically detail all clinical trials using MSCs in the field of SOT. Finally, we envision the challenges and perspectives of MSC-based cell therapy in SOT.

Human umbilical cord mesenchymal stem cell attenuates renal fibrosis via TGF-β/Smad signaling pathways in vivo and in vitro

Renal fibrosis is a progressive pathological process that eventually leads to end-stage renal failure with limited therapeutic options. The aim of this study was to investigate the nephron-protective effect of human umbilical cord mesenchymal stem cells (ucMSCs) on renal fibrosis. UcMSCs were intravenously injected into renal fibrosis mice induced by aristolochic acid (AA) and co-cultured with HK-2 cells induced by TGF-β1, respectively. The kidney functions including serum creatinine (Scr) and blood urea nitrogen (BUN) levels, and histopathology were examined after treated with stem cells and normal saline as control. Immunohistochemical staining, immunofluorescent staining, and Western blot analysis were used to assessed the expression of proteins associated with epithelial to mesenchymal transition (EMT) and TGF-β/Smad signaling pathway. The results showed that ucMSCs effectively improved the kidney function and pathological structure, reduced AA-induced fibrosis and extracellular matrix deposition. Besides, UcMSCs significantly inhibited the EMT process and TGF-β1/Smad signaling pathway in AA-induced mice and TGF-β1-induced HK-2 cells compared to the control (p < 0.05). Our data suggested that ucMSCs play as a nephron-protective role in anti-fibrosis through inhibiting the activation of TGF-β1/Smad signaling pathway.

Renal Injury Repair: How About the Role of Stem Cells

Renal failure is one of the most important causes of mortality and morbidity all over the world. Acute kidney injury (AKI) is a major clinical problem that affects up to 5% of all hospitalized patients. Although the kidney has a remarkable capacity for regeneration after acute injury, the mortality among patients with severe AKI remains dismally high, and in clinical practice, most patients cannot be cured completely and suffer from chronic kidney disease (CKD). Recently, the incidence and prevalence of CKD have increased, largely as a result of the enhanced prevalence of diabetes and obesity. The progressive nature of CKD and the ensuing end-stage renal disease (ESRD) place a substantial burden on global healthcare resources. Currently, dialysis and transplantation remain the only treatment options. Finding new therapeutic methods to fight AKI and CKD remains an ongoing quest. Although the human renal histological structure is complex, stem cell therapies have been applied to repair injured kidneys. The curative effects of mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), induced pluripotent stem cells (iPSCs), and nephron progenitor cells (NPCs) on renal repair have also been reported by researchers. This review focuses on stem cell therapy and mechanisms for renal injury repair.

IL-17A-induced mesenchymal stem cells have promising therapeutic value for clinical translation

Interferon (IFN) gamma is the prototypic proinflammatory cytokine used to preactivate the immunomodulatory properties of mesenchymal stem cells (MSC). IFN-gamma, however, converts MSC into a cell therapy that can be immunogenic, detrimental, and hence nonfeasible for clinical application. The article by Bai et al. is an in vivo proof-of-concept study that interleukin-17A (IL-17A) enhances the immunosuppressive, tolerance-promoting, and renoprotective properties of MSC. IL-17A is an alternative cytokine to preactivate MSC. IL-17A enhances the therapeutic efficacy of MSC for renal diseases.

Novel preconditioning strategies for enhancing the migratory ability of mesenchymal stem cells in acute kidney injury

Acute kidney injury (AKI) remains a worldwide public health issue due to its increasing incidence, significant mortality, and lack of specific target-orientated therapy. Developments in mesenchymal stem cell (MSC) research make MSCs a promising candidate for AKI management but relevant clinical trials show confusing results (NCT00733876, NCT01602328). One primary cause of the limited therapeutic effect may result from poor engraftment of transplanted cells. To solve this problem, investigators have developed a series of preconditioning strategies to improve MSC engraftment in animal AKI models. In this review, we summarize these previous studies, providing an integrated and updated view of different preconditioning strategies aimed at promoting the therapeutic effect of MSCs in AKI patients.

Concise Review: Using Fat to Fight Disease: A Systematic Review of Nonhomologous Adipose-Derived Stromal/Stem Cell Therapies

The objective of this Review is to describe the safety and efficacy of adipose stem/stromal cells (ASC) and stromal vascular fraction (SVF) in treating common diseases and the next steps in research that must occur prior to clinical use. Pubmed, Ovid Medline, Embase, Web of Science, and the Cochrane Library were searched for articles about use of SVF or ASC for disease therapy published between 2012 and 2017. One meta-analysis, 2 randomized controlled trials, and 16 case series were included, representing 844 human patients. Sixty-nine studies were performed in preclinical models of disease. ASCs improved symptoms, fistula healing, remission, and recurrence rates in severe cases of inflammatory bowel disease. In osteoarthritis, ASC and SVF improved symptom-related, functional, radiographic, and histological scores. ASC and SVF were also shown to improve clinical outcomes in ischemic stroke, multiple sclerosis, myocardial ischemia, chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, chronic liver failure, glioblastoma, acute kidney injury, and chronic skin wounds. These effects were primarily paracrine in nature and mediated through reduction of inflammation and promotion of tissue repair. In the majority of human studies, autologous ASC and SVF from liposuction procedures were used, minimizing the risk to recipients. Very few serious, treatment-related adverse events were reported. The main adverse event was postprocedural pain. SVF and ASC are promising therapies for a variety of human diseases, particularly for patients with severe cases refractory to current medical treatments. Further randomized controlled trials must be performed to elaborate potential safety and efficacy prior to clinical use. Stem Cells 2018;36:1311-1328.

Acute Kidney Injury as a Condition of Renal Senescence

Acute kidney injury (AKI), characterized by a sharp drop in glomerular filtration, continues to be a significant health burden because it is associated with high initial mortality, morbidity, and substantial health-care costs. There is a strong connection between AKI and mechanisms of senescence activation. After ischemic or nephrotoxic insults, a wide range of pathophysiological events occur. Renal tubular cell injury is characterized by cell membrane damage, cytoskeleton disruption, and DNA degradation, leading to tubular cell death by necrosis and apoptosis. The senescence mechanism involves interstitial fibrosis, tubular atrophy, and capillary rarefaction, all of which impede the morphological and functional recovery of the kidneys, suggesting a strong link between AKI and the progression of chronic kidney disease. During abnormal kidney repair, tubular epithelial cells can assume a senescence-like phenotype. Cellular senescence can occur as a result of cell cycle arrest due to increased expression of cyclin kinase inhibitors (mainly p21), downregulation of Klotho expression, and telomere shortening. In AKI, cellular senescence is aggravated by other factors including oxidative stress and autophagy. Given this scenario, the main question is whether AKI can be repaired and how to avoid the senescence process. Stem cells might constitute a new therapeutic approach. Mesenchymal stem cells (MSCs) can ameliorate kidney injury through angiogenesis, immunomodulation, and fibrosis pathway blockade, as well as through antiapoptotic and promitotic processes. Young umbilical cord–derived MSCs are better at increasing Klotho levels, and thus protecting tissues from senescence, than are adipose-derived MSCs. Umbilical cord–derived MSCs improve glomerular filtration and tubular function to a greater degree than do those obtained from adult tissue. Although senescence-related proteins and microRNA are upregulated in AKI, they can be downregulated by treatment with umbilical cord–derived MSCs. In summary, stem cells derived from young tissues, such as umbilical cord–derived MSCs, could slow the post-AKI senescence process.

Cellular therapies and stem cell applications in trauma

BACKGROUND

As the leading cause of mortality in the United States, trauma management have improved drastically over the past few decades with improved resuscitation and hemorrhage control. Stem cells are being used in an attempt to augment healing from trauma.

DATA SOURCES

PubMed and ClinicalTrials.gov were searched for published and registered pre-clinical and clinical trials for the application of stem cells to AKI, ARDS, shock, infection, TBI, wound healing, and bone healing.

CONCLUSIONS

Stem cell therapy for augmentation of healing traumatic injuries appears safe, as demonstrated by completed phase I/II trials. Further large scale studies are needed to assess the clinical efficacy.

Application of Muse Cell Therapy for Kidney Diseases

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

Mesenchymal stem cell-derived extracellular vesicles for kidney repair: current status and looming challenges

Novel therapies are urgently needed to address the rising incidence and prevalence of acute kidney injury (AKI) and chronic kidney disease (CKD). Mesenchymal stem/stromal cells (MSCs) have shown promising results in experimental AKI and CKD, and have been used in the clinic for more than a decade with an excellent safety profile. The regenerative effects of MSCs do not rely on their differentiation and ability to replace damaged tissues, but are primarily mediated by the paracrine release of factors, including extracellular vesicles (EVs), composed of microvesicles and exosomes. MSC-derived EVs contain genetic and protein material that upon transferring to recipient cells can activate several repair mechanisms to ameliorate renal injury. Recent studies have shown that MSC-derived EV therapy improved renal outcomes in several animal models of AKI and CKD, including ischemia-reperfusion injury, drug/toxin-induced nephropathy, renovascular disease, ureteral obstruction, and subtotal nephrectomy. However, data about the renoprotective effects of EV therapy in patients with renal failure are scarce. This review summarizes current knowledge of MSC-derived EV therapy in experimental AKI and CKD, and discusses the challenges that need to be addressed in order to consider MSC-derived EVs as a realistic clinical tool to treat patients with these conditions.

Cellular therapies in trauma and critical care medicine: Looking towards the future

Shibani Pati and Todd Rasmussen summarize progress in preclinical research on cellular therapeutics for traumatic injury and its sequelae and discuss prospects for clinical translation.

Human adipose stromal cell therapy improves survival and reduces renal inflammation and capillary rarefaction in acute kidney injury

Damage to endothelial cells contributes to acute kidney injury (AKI) by causing impaired perfusion, while the permanent loss of the capillary network following AKI has been suggested to promote chronic kidney disease. Therefore, strategies to protect renal vasculature may impact both short‐term recovery and long‐term functional preservation post‐AKI. Human adipose stromal cells (hASCs) possess pro‐angiogenic and anti‐inflammatory properties and therefore have been tested as a therapeutic agent to treat ischaemic conditions. This study evaluated hASC potential to facilitate recovery from AKI with specific attention to capillary preservation and inflammation. Male Sprague Dawley rats were subjected to bilateral ischaemia/reperfusion and allowed to recover for either two or seven days. At the time of reperfusion, hASCs or vehicle was injected into the suprarenal abdominal aorta. hASC‐treated rats had significantly greater survival compared to vehicle‐treated rats (88.7% versus 69.3%). hASC treatment showed hastened recovery as demonstrated by lower creatinine levels at 48 hrs, while tubular damage was significantly reduced at 48 hrs. hASC treatment resulted in a significant decrease in total T cell and Th17 cell infiltration into injured kidneys at 2 days post‐AKI, but an increase in accumulation of regulatory T cells. By day 7, hASC‐treated rats showed significantly attenuated capillary rarefaction in the cortex (15% versus 5%) and outer medulla (36% versus 18%) compared to vehicle‐treated rats as well as reduced accumulation of interstitial alpha‐smooth muscle actin‐positive myofibroblasts. These results suggest for the first time that hASCs improve recovery from I/R‐induced injury by mechanisms that contribute to decrease in inflammation and preservation of peritubular capillaries.

Endothelial colony-forming cells ameliorate endothelial dysfunction via secreted factors following ischemia-reperfusion injury

Damage to endothelial cells contributes to acute kidney injury (AKI) by leading to impaired perfusion. Endothelial colony-forming cells (ECFC) are endothelial precursor cells with high proliferative capacity, pro-angiogenic activity, and in vivo vessel forming potential. We hypothesized that ECFC may ameliorate the degree of AKI and/or promote repair of the renal vasculature following ischemia-reperfusion (I/R). Rat pulmonary microvascular endothelial cells (PMVEC) with high proliferative potential were compared with pulmonary artery endothelial cells (PAEC) with low proliferative potential in rats subjected to renal I/R. PMVEC administration reduced renal injury and hastened recovery as indicated by serum creatinine and tubular injury scores, while PAEC did not. Vehicle-treated control animals showed consistent reductions in renal medullary blood flow (MBF) within 2 h of reperfusion, while PMVEC protected against loss in MBF as measured by laser Doppler. Interestingly, PMVEC mediated protection occurred in the absence of homing to the kidney. Conditioned medium (CM) from human cultured cord blood ECFC also conveyed beneficial effects against I/R injury and loss of MBF. Moreover, ECFC-CM significantly reduced the expression of ICAM-1 and decreased the number of differentiated lymphocytes typically recruited into the kidney following renal ischemia. Taken together, these data suggest that ECFC secrete factors that preserve renal function post ischemia, in part, by preserving microvascular function.

Endothelial Colony Forming Cells (ECFCs) in murine AKI - implications for future cell-based therapies

Background

In recent years, early Endothelial Progenitor Cells (eEPCs) have been proven as effective tool in murine ischemic AKI and in diabetic nephropathy. The mechanisms of eEPC-mediated vasoprotection have been elucidated in detail. Besides producing a diverse range of humoral factors, the cells also act by secreting vasomodulatory microvesicles. Only few data in contrast have been published about the role of so-called Endothelial Colony Forming Cells (ECFCs - late EPCs) in ischemic AKI. We thus aimed to investigate ECFC effects on postischemic kidney function over several weeks. Our special interest focused on endothelial-to-mesenchymal transition (EndoMT), peritubular capillary density (PTCD), endothelial alpha-Tubulin (aT - cytoskeletal integrity), and endothelial p62 (marker of autophagocytic flux).

Methods

Eight to twelve weeks old male C57Bl/6 N mice were subjected to bilateral renal pedicle clamping for 35 or 45 min, respectively. Donor-derived syngeneic ECFCs (0.5 × 10⁶) were i.v. injected at the end of ischemia. Animals were analyzed 1, 4 and 6 weeks later.

Results

Cell therapy improved kidney function exclusively at week 1 (35 and 45 min). Ischemia-induced fibrosis was diminished in all experimental groups by ECFCs, while PTCD loss remained unaffected. Significant EndoMT was detected in only two of 6 groups (35 min, week 4 and 45 min, week 6), ECFCs reduced EndoMT only in the latter. Endothelial aT declined under almost all experimental conditions and these effects were further aggravated by ECFCs. p62 was elevated in endothelial cells, more so after 45 than after 35 min of ischemia. Cell therapy did not modulate p62 abundances at any time point.

Conclusion

A single dose of ECFCs administered shortly post-ischemia is capable to reduce interstitial fibrosis in the mid- to long-term whereas excretory dysfunction is improved only in a transient manner. There are certain differences in renal outcome parameters between eEPCs and ECFC. The latter do not prevent animals from peritubular capillary loss and they also do not further elevate endothelial p62. We conclude that differences between eEPCs and ECFCs result from certain mechanisms by which the cells act around and within vessels. Overall, ECFC treatment was not as efficient as eEPC therapy in preventing mice from ischemia-induced mid- to long-term damage.

Healing the damaged mesangium in nodular glomerulosclerosis using mesenchymal stem cells (MSCs): Expectations and challenges

It has been shown experimentally that mesenchymal stem cells (MSCs) can be delivered to the mesangium in some conditions such as amyloidosis to clear debris and foreign material, and eventually transform into functional mesangial cells (MCs) and change the altered mesangial areas into normal collagen IV-rich matrix. A more challenging situation is when the matrix is rich in abnormal extracellular matrix proteins, especially those difficult to destroy such as tenascin, and, as a result, assumes a nodular appearance - what is known in pathology jargon as nodular glomerulosclerosis. MSCs find it difficult to dispose of the altered mesangial constituents, an initial step required for mesangial repair to occur successfully. The ability of MSCs to repair damaged mesangium represents a novel therapeutic intervention to reverse mesangial injury and is potentially a powerful and unique approach to prevent progression ending in end-stage renal disease (ESRD). This review will highlight progress that has been made in glomerular, and more specifically mesangial, repair, and will address future expectations and challenges to be confronted as the use of MSCs continues to be explored as a potential application for clinical practice.

Mesenchymal stem cells protect against obstruction-induced renal fibrosis by decreasing STAT3 activation and STAT3-dependent MMP-9 production

STAT3 is a transcription factor implicated in renal fibrotic injury, but the role of STAT3 in mesenchymal stem cell (MSC)-induced renoprotection during renal fibrosis remains unknown. We hypothesized that MSCs protect against obstruction-induced renal fibrosis by downregulating STAT3 activation and STAT3-induced matrix metalloproteinase-9 (MMP-9) expression. Male Sprague-Dawley rats underwent renal arterial injection of vehicle or MSCs (1 × 10⁶/rat) immediately before sham operation or induction of unilateral ureteral obstruction (UUO). The kidneys were harvested after 4 wk and analyzed for collagen I and III gene expression, collagen deposition (Masson's trichrome), fibronectin, α-smooth muscle actin, active STAT3 (p-STAT3), MMP-9, and tissue inhibitor of matrix metalloproteinases 1 (TIMP-1) expression. In a separate arm, the STAT3 inhibitor S3I-201 (10 mg/kg) vs. vehicle was administered to rats intraperitoneally just after induction of UUO and daily for 14 days thereafter. The kidneys were harvested after 2 wk and analyzed for p-STAT3 and MMP-9 expression, and collagen and fibronectin deposition. Renal obstruction induced a significant increase in collagen, fibronectin, α-SMA, p-STAT3, MMP-9, and TIMP-1 expression while exogenously administered MSCs significantly reduced these indicators of obstruction-induced renal fibrosis. STAT3 inhibition with S3I-201 significantly reduced obstruction-induced MMP-9 expression and tubulointerstitial fibrosis. These results demonstrate that MSCs protect against obstruction-induced renal fibrosis, in part, by decreasing STAT3 activation and STAT3-dependent MMP-9 production.

Cellular Therapies in Trauma and Critical Care Medicine: Forging New Frontiers

Trauma is a leading cause of death in both military and civilian populations worldwide. Although medical advances have improved the overall morbidity and mortality often associated with trauma, additional research and innovative advancements in therapeutic interventions are needed to optimize patient outcomes. Cell-based therapies present a novel opportunity to improve trauma and critical care at both the acute and chronic phases that often follow injury. Although this field is still in its infancy, animal and human studies suggest that stem cells may hold great promise for the treatment of brain and spinal cord injuries, organ injuries, and extremity injuries such as those caused by orthopedic trauma, burns, and critical limb ischemia. However, barriers in the translation of cell therapies that include regulatory obstacles, challenges in manufacturing and clinical trial design, and a lack of funding are critical areas in need of development. In 2015, the Department of Defense Combat Casualty Care Research Program held a joint military–civilian meeting as part of its effort to inform the research community about this field and allow for effective planning and programmatic decisions regarding research and development. The objective of this article is to provide a “state of the science” review regarding cellular therapies in trauma and critical care, and to provide a foundation from which the potential of this emerging field can be harnessed to mitigate outcomes in critically ill trauma patients.

Comparison of stem cell therapies for acute kidney injury

Acute kidney injury (AKI) is the rapid onset of decreased kidney function that ultimately increases mortality and morbidity. Stem cell research is a promising avenue for curative and preventative therapies of kidney injury, however, there are many types of stem cells under investigation. Currently there is no research to compare the value of one stem cell method over another. Induced pluripotent stem cells (iPSCs) and spermatogonial stem cells (SSCs) have been shown to differentiate into renal cells, though further clinical research is needed to fully explore potential therapeutic strategies. Mesenchymal stem cells (MSCs) have long been investigated in the preclinical setting and have recently been successful in Phase I clinical trials. MSCs may represent a promising new therapeutic approach to treat AKI as they demonstrate renoprotective effects post-injury via the secretion of promitotic, anti-apoptotic, anti-inflammatory, and immunomodulatory factors. Given the most current research, MSCs appear to offer a promising course of treatment for AKI.

The endothelial-to-mesenchymal transition and endothelial cilia in EPC-mediated postischemic kidney protection

Renal ischemia induces peritubular capillary rarefication and fibrosis, with the latter partly resulting from the endothelial-to-mesenchymal transition (EndoMT). Endothelial cilia transmit blood flow-associated forces into the cell. Early endothelial progenitor cells (eEPCs) have been shown to protect mice from acute kidney injury in the short term. The aim of the present study was to analyze midterm consequences of eEPC treatment in the context of endothelial cilia and the EndoMT. Male C57/Bl6N mice were subjected to unilateral renal ischemia postuninephrectomy. Syngeneic murine eEPCs were systemically injected at the time of reperfusion. Animals were investigated 1, 4, and 6 wk later. Cultured mature endothelial cells were exposed to a variable flow with versus without eEPC supernatant incubation. Systemically injected eEPCs reduced serum creatinine levels at week 1 (35 and 45 min) and week 4 (45 min). Interstitial fibrosis was significantly diminished by cell treatment at all time points as well. The EndoMT was less pronounced at week 4 (35 min) and week 6 (45 min). eEPC supernatant reduced α-smooth muscle actin expression and α-tubulin abundance in flow-treated cultured mature endothelial cells, and percentages of cilium-positive cells increased. The loss of peritubular capillaries was prevented by eEPCs. Intrarenal endothelial α-tubulin decreased postischemia and was further reduced by eEPC administration. We conclude that eEPCs are capable of reorganizing the endothelial cytoskeleton in an indirect manner, ultimately resulting in stabilization of the endothelial ciliome. The investigation indicates an antimesenchymal role of endothelial cilia in the process of postischemic tissue fibrosis/EndoMT.

Nuclear factor erythroid-2 related factor 2 overexpressed mesenchymal stem cells transplantation, improves renal function, decreases injuries markers and increases repair markers in glycerol-induced Acute kidney injury rats

OBJECTIVES

Recently cell therapy is a promising therapeutic modality for many types of disease including acute kidney injury (AKI). Due to the unique biological properties, mesenchymal stem cells (MSCs) are attractive cells in this regard. This study aims to transplant MSCs equipped with nuclear factor E2-related factor 2 (Nrf2) in rat experimental models of acute kidney and evaluate regeneration potential of injured kidney especially expression of injury and repaired biomarkers.

MATERIALS AND METHODS

Nrf2 was overexpressed in bone marrow-derived MSCs by pcDNA.3.1 plasmid. AKI was induced using glycerol in rat models. The regenerative potential of Nrf2-overexpressed MSCs was evaluated in AKI-Induced animal models using biochemical and histological methods after transplantation. Expression of repaired genes, AQP1 and CK-18, as well as injury markers, Kim-1 and Cystatin C, was also assayed in engrafted kidney sections.

RESULTS

Our results revealed that transplantation of Nrf2-overexpressed MSCs into AKI-induced rats decreased blood urea nitrogen and creatinine and ameliorated kidney regeneration throughout 14 days. Upregulation of repaired markers and downregulation of injury markers were considerable 14 days after transplantation.

CONCLUSIONS

Overexpression of Nrf2 in MSCs suggests a new strategy to increase efficiency of MSC-based cell therapy in AKI.

Challenges and opportunities for stem cell therapy in patients with chronic kidney disease

Chronic kidney disease (CKD) is a global health care burden affecting billions of individuals worldwide. The kidney has limited regenerative capacity from chronic insults, and for the most common causes of CKD, no effective treatment exists to prevent progression to end-stage kidney failure. Therefore, novel interventions, such as regenerative cell-based therapies, need to be developed for CKD. Given the risk of allosensitization, autologous transplantation of cells to boost regenerative potential is preferred. Therefore, verification of cell function and vitality in CKD patients is imperative. Two cell types have been most commonly applied in regenerative medicine. Endothelial progenitor cells contribute to neovasculogenesis primarily through paracrine angiogenic activity and partly by differentiation into mature endothelial cells in situ. Mesenchymal stem cells also exert paracrine effects, including proangiogenic, anti-inflammatory, and antifibrotic activity. However, in CKD, multiple factors may contribute to reduced cell function, including older age, coexisting cardiovascular disease, diabetes, chronic inflammatory states, and uremia, which may limit the effectiveness of an autologous cell-based therapy approach. This Review highlights current knowledge on stem and progenitor cell function and vitality, aspects of the uremic milieu that may serve as a barrier to therapy, and novel methods to improve stem cell function for potential transplantation.

Selected renal cells modulate disease progression in rodent models of chronic kidney disease via NF-κB and TGF-β1 pathways

AIM

Identification of mechanistic pathways for selected renal cell (SRC) therapeutic bioactivity in rodent models of chronic kidney disease.

MATERIALS & METHODS

In vivo and in vitro functional bioassays applied to investigate regenerative outcomes associated with delivery of SRC to diseased rodent kidney.

RESULTS

In vivo, SRC reduces chronic infiltration by monocytes/macrophages. SRC attenuates NF-κB and PAI-1 responses while simultaneously promoting host tubular cell expansion through trophic cues. In vitro, SRC-derived conditioned media attenuates TNF-α-induced NF-κB response, TGF-β-mediated PAI-1 response and increases expression of transcripts associated with cell cycle regulation. Observed bioactive responses were from vesicle and nonvesicle-associated factors, including specific miRNAs.

CONCLUSION

We identify a paracrine mechanism for SRC immunomodulatory and trophic cues on host renal tissues, catalyzing long-term functional benefits in vivo.

Intra-arterial catheter system to repeatedly deliver mesenchymal stem cells in a rat renal failure model

BACKGROUND

Mesenchymal stem cell therapy in renal failure is rarely used because of low rates of cell engraftment after systemic delivery. Repeated intra-arterial cell administration may improve results; however, no current delivery method permits repeated intra-arterial infusions in a rat model. In this study, we developed an intra-arterial delivery system for repeated stem cell infusion via the aorta, catheterizing the left femoral artery to the suprarenal aorta under fluoroscopic guidance in rats with adenosine-induced renal failure.

METHODS

First, we compared our intra-arterial catheter system (C group, n = 3) with tail vein injection (V group, n = 3) for engraftment efficacy, using mesenchymal stem cells from luciferase transgenic rats. Rats were infused with the cells and euthanized the following day; we performed cell-tracking experiments using a bioluminescence imaging system to assess the distribution of the infused cells. Second, we assessed the safety of the system over a 30-day period in a second group of six rats receiving infusions every 7 days.

RESULTS

Cells infused through our delivery system efficiently engrafted into the kidney, compared with peripheral venous infusion. In five of the six rats in the safety study, the delivery system remained patent for at least 9 days (range, 9-24 days). Complications became evident only after 10 days.

CONCLUSION

Our intra-arterial catheter system was effective in delivering cells to the kidney and permitted repeated injection of cells.

Mesenchymal stem/stromal cells as a delivery platform in cell and gene therapies

Regenerative medicine relying on cell and gene therapies is one of the most promising approaches to repair tissues. Multipotent mesenchymal stem/stromal cells (MSC), a population of progenitors committing into mesoderm lineages, are progressively demonstrating therapeutic capabilities far beyond their differentiation capacities. The mechanisms by which MSC exert these actions include the release of biomolecules with anti-inflammatory, immunomodulating, anti-fibrogenic, and trophic functions. While we expect the spectra of these molecules with a therapeutic profile to progressively expand, several human pathological conditions have begun to benefit from these biomolecule-delivering properties. In addition, MSC have also been proposed to vehicle genes capable of further empowering these functions. This review deals with the therapeutic properties of MSC, focusing on their ability to secrete naturally produced or gene-induced factors that can be used in the treatment of kidney, lung, heart, liver, pancreas, nervous system, and skeletal diseases. We specifically focus on the different modalities by which MSC can exert these functions. We aim to provide an updated understanding of these paracrine mechanisms as a prerequisite to broadening the therapeutic potential and clinical impact of MSC.

Designing drugs that combat kidney damage

INTRODUCTION

Kidney disease remains one of the last worldwide frontiers in the field of non-communicable human disease. From 1990 to 2013, chronic kidney disease (CKD) was the top non-communicable cause of death with a greatest increase in global years of life lost while mortality of acute kidney injury (AKI) still hovers around 50%. This reflects the paucity (for CKD) or lack of (for AKI) therapeutic approaches beyond replacing renal function. Understanding what the barriers are and what potential pathways may facilitate the design of new drugs to combat kidney disease is a key public health priority.

AREAS COVERED

The authors discuss the hurdles and opportunities for future drug development for kidney disease in light of experience accumulated with drugs that made it to clinical trials.

EXPERT OPINION

Inflammation, cell death and fibrosis are key therapeutic targets to combat kidney damage. While the specific targeting of drugs to kidney cells would be desirable, the technology is only working at the preclinical stage and with mixed success. Nanomedicines hold promise in this respect. Most drugs undergoing clinical trials for kidney disease have been repurposed from other indications. Currently, the chemokine receptor inhibitor CCX140 holds promise for CKD and the p53 inhibitor QPI-1002 for AKI.

Nestin(+) kidney resident mesenchymal stem cells for the treatment of acute kidney ischemia injury

Renal resident mesenchymal stem cells (MSCs) are important regulators of kidney homeostasis, repair or regeneration. However, natural distribution and the starting population properties of these cells remain elusive because of the lack of specific markers. Here, we identified post-natal kidney derived Nestin(+) cells that fulfilled all of the criteria as a mesenchymal stem cell. These isolated Nestin(+) cells expressed the typical cell-surface marker of MSC, including Sca-1, CD44, CD106, NG2 and PDGFR-α. They were capable of self-renewal, possessed high clonogenic potential and extensive proliferation for more than 30 passages. Under appropriate differentiation conditions, these cells could differentiate into adipocytes, osteocytes, chondrocytes and podocytes. After intravenous injection into acute kidney injury mice, Nestin(+) cells contributed to functional improvement by significantly decreasing the peak level of serum creatinine and BUN, and reducing the damaged cell apoptosis. Furthermore, conditioned medium from Nestin(+) cells could protect against ischemic acute renal failure partially through paracrine factor VEGF. Taken together, our findings indicate that renal resident Nestin(+) MSCs can be derived, propagated, differentiated, and repair the acute kidney injury, which may shed new light on understanding MSCs biology and developing cell replacement therapies for kidney disease.

Concise review: mesenchymal stem cell treatment for ischemic kidney disease

Ischemic kidney diseases are common clinical entities that bear high mortality and morbidity and may lead to irreversible loss of kidney function. Their pathophysiology is multifaceted, involves complex hormonal-immunological-cellular interactions, and leads to damage in multiple cell types, which is often resistant to conventional therapy. Thus, novel strategies are needed to repair the renal parenchyma and preserve kidney function. Mesenchymal stem cells (MSC) confer renal protection through paracrine/endocrine effects and to some degree possibly by direct engraftment. Their anti-inflammatory and immune-modulatory properties target multiple cascades in the mechanisms of ischemic kidney disease. This review focuses on recent progress on the use of MSC to prevent kidney injury in ischemic kidney injury, with a focus on the chronic form.

Umbilical Cord Mesenchymal Stem Cell Transplantation Ameliorates Burn-Induced Acute Kidney Injury in Rats

Excessive systemic inflammation following burns could lead to acute kidney injury (AKI). Mesenchymal stromal cells (MSCs) suppress immune cell responses and have beneficial effects in various inflammatory-related immune disorders. However, autologous MSCs are not vital enough for the treatment because of the severely burned patients’ deleterious condition. Umbilical cord–derived mesenchymal stem cells (UC-MSCs) could be a suitable substitute cell candidate but no data are available on the therapeutic effectiveness of UC-MSCs transplantation for burn injury and its consequences. In this study, UC-MSCs or ulinastatin was administered intravenously in the rats with burn trauma, and the therapeutic effects of UC-MSCs on the survival of severe burn-induced AKI rats and functional protection of kidney were analyzed. Results showed that UC-MSCs promoted the survival and prevented commitment to apoptosis of resident kidney cells and reduced organ microscopic damage in kidneys after thermal trauma. Thus, our study demonstrates that intravenously delivered UC-MSCs protected the host from death caused by kidney injury subsequent to severe burn, identifying UC-MSCs transplantation may be an attractive candidate for cell-based treatments for burns and induced organ damage.

Stem cells and their role in renal ischaemia reperfusion injury

BACKGROUND

Ischaemia-reperfusion injury (IRI) remains one of the leading causes of acute kidney injury (AKI). IRI is an underlying multifactorial pathophysiological process which affects the outcome in both native and transplanted patients. The high morbidity and mortality associated with IRI/AKI and disappointing results from current available clinical therapeutic approaches prompt further research. Stem cells (SC) are undifferentiated cells that can undergo both renewal and differentiation into one or more cell types which can possibly ameliorate IRI.

AIM

To carry out a detailed literature analysis and construct a comprehensive literature review addressing the role of SC in AKI secondary to IRI.

METHODS

Evidence favouring the role of SC in renal IRI and evidence showing no benefits of SC in renal IRI are the two main aspects to be studied. The search strategy was based on an extensive search addressing MESH terms and free text terms.

RESULTS

The majority of studies in the field of renal IRI and stem cell therapy show substantial benefits.

CONCLUSIONS

Studies were mostly conducted in small animal models, thus underscoring the need for further pre-clinical studies in larger animal models, and results should be taken with caution. SC therapy may be promising though controversy exists in the exact mechanism. Thorough scientific exploration is required to assess mechanism, safety profile, reproducibility and methods to monitor administered SC.