Mesenchymal stem cells: Immunobiology and therapeutic potential in kidney disease (Review Article)

Role of hsa-miR-543-KIF5C/CALM3 pathway in neuron differentiation of embryonic mesenchymal stem cells

BACKGROUND

Human umbilical cord mesenchymal stem cells (hUC-MSCs) have the ability to differentiate into nerve cells, which offers promising options for treating neurodegenerative diseases.

AIM

To explore the important regulatory molecules of hUC-MSCs differentiation into neurons.

METHOD

In this research, the neural differentiation of hUC-MSCs was induced by a low-serum DMSO/BHA/DMEM medium. The GEO database was used to retrieve the relevant datasets. The starBase and miEAA databases were used for bioinformatics analysis. RT-qPCR was used to detect the hsa-miR-543 level and the mRNA levels of NSE, NeuN, NF-M, KIF5C, and CALM3. The protein levels of KIF5C and CALM3 were checked by western blotting.

RESULTS

The expression levels of NSE, NeuN, NF-M, KIF5C, and CALM3 were elevated, while hsa-miR-543 was under-expressed in neuro-induced hUC-MSCs. The increase in NSE, NeuN, and NF-M mRNA levels induced by DMSO/BHA/DMEM was partially reversed by the knockdown of KIF5C and CALM3 in hUC-MSCs. Moreover, the transfection of hsa-miR-543 mimic partially countered the DMSO/BHA/DMEM-induced elevation in NSE, NeuN, NF-M, KIF5C, and CALM3 mRNA levels.

CONCLUSION

KIF5C and CALM3 facilitated the neuronal differentiation of hUC-MSCs, whereas hsa-miR-543 exerted an opposing effect by negatively regulating KIF5C and CALM3.

The immunomodulatory effects of mesenchymal stromal cell-based therapy in human and animal models of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune inflammatory disease with no absolute cure. Although the exact etiopathogenesis of SLE is still enigmatic, it has been well demonstrated that a combination of genetic predisposition and environmental factors trigger a disturbance in immune responses and thereby participate in the development of this condition. Almost all available therapeutic strategies in SLE are primarily based on the administration of immunosuppressive drugs and are not curative. Mesenchymal stromal cells (MSCs) are a subset of non-hematopoietic adult stem cells that can be isolated from many adult tissues and are increasingly recognized as immune response modulating agents. MSC-mediated inhibition of immune responses is a complex mechanism that involves almost every aspect of the immune response. MSCs suppress the maturation of antigen-presenting cells (DC and MQ), proliferation of T cells (Th1, T17, and Th2), proliferation and immunoglobulin production of B cells, the cytotoxic activity of CTL and NK cells in addition to increasing regulatory cytokines (TGF-β and IL10), and decreasing inflammatory cytokines (IL17, INF-ϒ, TNF-α, and IL12) levels. MSCs have shown encouraging results in the treatment of several autoimmune diseases, in particular SLE. This report aims to review the beneficial and therapeutic properties of MSCs; it also focuses on the results of animal model studies, preclinical studies, and clinical trials of MSC therapy in SLE from the immunoregulatory aspect.

Placental Mesenchymal Stromal Cells (PMSCs) and PMSC-Derived Extracellular Vesicles (PMSC-EVs) Attenuated Renal Fibrosis in Rats with Unilateral Ureteral Obstruction (UUO) by Regulating CD4+ T Cell Polarization

Purpose

Recent evidence has shown that CD4⁺ T helper (Th) cells are involved in renal inflammation and fibrosis. However, whether renal fibrosis can be alleviated by intervening in the polarization of CD4⁺ T cells remains unknown. Our research investigated the effects of intravenously administered placenta mesenchymal stromal cells (PMSCs) or treatment with extracellular EVs (EVs) derived from PMSCs (PMSC-EVs) on the polarization of CD4⁺ T cells in rats with unilateral ureteral obstruction (UUO). We further verified how PMSCs affect inflammatory factor secretion and the levels of regulatory T (Treg) and Th17 CD4⁺ T cells in vitro.

Materials and Methods

We evaluated renal interstitial inflammation and fibrosis by pathological section staining, tested the polarization of CD4⁺ T cells (Th17 and Treg phenotypes) by flow cytometry (FCM) and immunohistochemistry, and detected the cytokines secreted by CD4⁺ T cells by enzyme-linked immunosorbent assay (ELISA).

Results

Compared with that of control rats, the renal tissue of PMSC-treated rats exhibited lower renal Masson scores and more Foxp3⁺ cell infiltration, with a significantly decreased IL17A⁺CD4⁺ T cell/CD4⁺ T cell ratio and a significantly elevated anti-inflammatory cytokine (IL-10) level. When CD4⁺ T cells were cocultured with PMSCs, CD4⁺IL17A⁺ cell percentages were decreased in a UUO model after 7 days of coculture with PMSCs. The secretion of TGF-β and IL-10 was significantly increased (P < 0.05), while the secretion of IFN-γ, IL-17, and IL-6 was significantly decreased (P < 0.05) in the PMSC coculture group. Moreover, after treatment with PMSC-EVs, tubulointerstitial fibrosis was alleviated, and Foxp3⁺/IL-17⁺ cell infiltration was increased in the kidneys of UUO model animals on day 7.

Conclusions

PMSCs can convert the inflammatory environment into an anti-inflammatory environment by affecting the polarization of CD4⁺ T cells and macrophages, inhibiting the inflammatory factors IFN-γ and IL-17, and upregulating the expression of the anti-inflammatory factors TGF-β and IL-10, ultimately leading to renal protection. Such functions may be mediated by the paracrine activity of PMSC-EVs.

Reproducible Derivation and Expansion of Corneal Mesenchymal Stromal Cells for Therapeutic Applications

Purpose

A reproducible protocol for the production of corneal mesenchymal stem/stromal cells (cMSCs) is necessary for potential clinical applications. We aimed to describe successful generation and expansion of cMSCs using an explant method.

Methods

Corneoscleral rims of human cadaveric eyes were divided into four pieces and used as explants to allow outgrowth of cMSCs (passage 0, or P0). The cells were subcultured at a 1:10 ratio until passage 5 (P5). The characteristics as well as therapeutic effects of expanded cMSCs were evaluated both in vitro, using a scratch assay, and in vivo using epithelial debridement and chemical injury mouse models.

Results

All explants demonstrated outgrowth of cells by 7 days. Although the initial outgrowth included mixed mesenchymal and epithelial cells, by P1 only cMSCs remained. By subculturing each flask at a ratio of 1:10, the potential yield from each cornea was approximately 12 to 16 × 10¹⁰ P5 cells. P5 cMSCs demonstrated the cell surface markers of MSCs. The secretome of P5 cMSCs induced faster closure of wounds in an in vitro scratch assay. Subconjunctival injection of P5 cMSCs in mouse models of mechanical corneal epithelial debridement or ethanol injury led to significantly faster wound healing and decreased inflammation, relative to control.

Conclusions

cMSCs can be reproducibly derived from human cadaveric corneas using an explant method and expanded with preservation of characteristics and corneal wound healing effects.

Translational Relevance

The results of our study showed that cMSCs produced using this scheme can be potentially used for clinical applications.

Mesenchymal stem cells in allergic diseases: Current status

Allergic diseases, which include asthma, allergic skin diseases, allergic rhinitis and allergic conjunctivitis, have already garnered worldwide public health attention over recent decades. Mesenchymal stem cells (MSCs) have gradually emerged as a potential method for treating allergic diseases due to their immunosuppressive characteristics, tissue repair ability and secretion of various biological factors. This potential of MSC-based therapy has been confirmed in clinical and preclinical studies, which report the therapeutic benefits of MSCs for various allergic diseases and explore the antiallergic mechanisms. In this review, we focus on the discoveries and biological mechanisms of MSCs as a therapeutic tool in allergic diseases. We discuss the challenges of conducting MSC studies as well as future directions.

The Anti-Inflammatory, Anti-Oxidative, and Anti-Apoptotic Benefits of Stem Cells in Acute Ischemic Kidney Injury

Ischemia-reperfusion injury (IRI) plays a significant role in the pathogenesis of acute kidney injury (AKI). The complicated interaction between injured tubular cells, activated endothelial cells, and the immune system leads to oxidative stress and systemic inflammation, thereby exacerbating the apoptosis of renal tubular cells and impeding the process of tissue repair. Stem cell therapy is an innovative approach to ameliorate IRI due to its antioxidative, immunomodulatory, and anti-apoptotic properties. Therefore, it is crucial to understand the biological effects and mechanisms of action of stem cell therapy in the context of acute ischemic AKI to improve its therapeutic benefits. The recent finding that treatment with conditioned medium (CM) derived from stem cells is likely an effective alternative to conventional stem cell transplantation increases the potential for future therapeutic uses of stem cell therapy. In this review, we discuss the recent findings regarding stem cell-mediated cytoprotection, with a focus on the anti-inflammatory effects via suppression of oxidative stress and uncompromised immune responses following AKI. Stem cell-derived CM represents a favorable approach to stem cell-based therapy and may serve as a potential therapeutic strategy against acute ischemic AKI.

Intra-arterial renal infusion of autologous mesenchymal stem cells for treatment of chronic kidney disease in cats: Phase I clinical trial

Background

There are no known treatments that halt or reverse chronic kidney disease (CKD) in cats. In rodent models, stem cell treatment has been associated with improvement in renal function parameters, especially when stem cells were delivered intra‐arterially to the kidney. To date, only IV and intrarenal stem cell infusions have been studied in cats with CKD with no clinically relevant improvement noted.

Objective

To assess the safety and feasibility of intra‐arterial delivery of autologous mesenchymal stem cells (MSC) in stromal vascular fraction (SVF) to the kidney in cats with CKD.

Animals

Five client‐owned domestic cats with International Renal Interest Society stage III CKD.

Methods

Prospective cohort study (phase I clinical trial). Adipose tissue was harvested from study animals on day 0. On days 2 and 14, an infusion of MSC in SVF was administered into the renal artery via the femoral or carotid artery using fluoroscopic guidance. Serum creatinine and blood urea nitrogen concentration, plasma iohexol clearance, and quality of life assessments were monitored between days 0 and 90.

Results

The procedure was performed successfully in all cats. No severe adverse events were observed in any cat during the study period.

Conclusions and Clinical Importance

Intra‐arterial infusion of MSC into the renal artery in CKD cats was feasible and safe within a 3‐month postoperative period. Efficacy and long‐term safety have yet to be established. This procedure requires careful technique and training.

Stem Cell Therapy

Stem cell therapy has tremendous potential for clinical application in the treatment of a variety of diseases in veterinary medicine. Based on the known desirable immunomodulatory properties of mesenchymal stem cells, this therapy has potential for treatment of a variety of renal diseases. This review details our current understanding of stem cell biology and proposed mechanism of action as applicable to renal disease. Studies performed in chronic kidney disease clinical trials and models of acute kidney injury are summarized with the goal of providing an overview of the current status of this treatment modality and its potential for the future.

Comparison of proliferative and immunomodulatory potential of adipose-derived mesenchymal stem cells from young and geriatric cats

Objectives The objective of this study was to compare the ability of adipose-derived mesenchymal stem cells (aMSCs) generated from young vs geriatric cats to proliferate in culture, suppress lymphocyte proliferation and undergo senescence. Methods Adipose tissues from five young (<5 years) and six geriatric (>10 years) cats were harvested and cryopreserved for subsequent aMSC isolation and culture. aMSC proliferation in culture was compared via determination of time until passage two and by 3-(4,5-demethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The immunomodulatory capacity of aMSCs was assessed using lymphocyte proliferation assays, and senescence was evaluated using senescence-associated B-galactosidase (SABG) expression. All assays were performed on aMSCs between passage two and passage three. Results aMSCs from geriatric cats took significantly longer ( P = 0.008) to reach passage two (median 11 days, range 9-22 days) compared with aMSCs from young healthy cats (median 7 days, range 6-8 days). No significant difference was detected between young and geriatric cats in terms of their ability to suppress lymphocyte proliferation. SABG expression was not significantly different between young and geriatric aMSCs. Conclusions and relevance Compared with young feline aMSCs, geriatric aMSCs are significantly impaired in their ability to rapidly proliferate to passage two following initial culture, presenting a concern for autologous therapy. Nonetheless, once the cells are expanded, young and geriatric cat aMSCs appear to be equivalent in terms of their ability to functionally suppress T-cell activation and proliferation.

Assessment of intravenous adipose-derived allogeneic mesenchymal stem cells for the treatment of feline chronic kidney disease: a randomized, placebo-controlled clinical trial in eight cats

OBJECTIVES

Feline chronic kidney disease (CKD) is characterized by chronic tubulointerstitial nephritis, and inflammation contributes to the progression of renal fibrosis. Mesenchymal stem cells (MSCs) have demonstrated anti-inflammatory and antifibrotic effects in rodent CKD models. However, few randomized trials evaluating the effectiveness of MSC therapy for diseases in companion animals have been reported. The purpose of this study was to evaluate the effectiveness of allogeneic MSCs for the treatment of feline CKD using a randomized, placebo-controlled trial.

METHODS

MSCs were isolated from the cryopreserved adipose tissues of specific pathogen-free research cats and culture expanded. CKD cats were enrolled in a randomized, placebo-controlled, blinded one-way crossover clinical study. Four CKD cats were randomized to receive 2 × 10(6) MSCs/kg intravenously at 2, 4 and 6 weeks. Four CKD cats were randomized to receive placebo, with two cats crossing over to the MSC treatment group and one cat failing to complete the trial. Complete blood counts, chemistry and urinalysis were performed at weeks 0, 2, 4, 6 and 8. Glomerular filtration rate (GFR) via nuclear scintigraphy and urine protein:creatinine ratio (UPC) were determined at weeks 0 and 8.

RESULTS

Six cats received three doses of allogeneic MSC culture expanded from cryopreserved adipose without adverse effects. No significant change in serum creatinine, blood urea nitrogen, potassium, phosphorus, GFR by nuclear scintigraphy, UPC or packed cell volume was seen in cats treated with MSCs. Individual changes in GFR were 12%, 8%, 8%, 2%, -13% and -67% in treated cats compared with 16%, 36% and 0% in placebo-treated cats.

CONCLUSIONS AND RELEVANCE

While administration of MSC culture expanded from cryopreserved adipose was not associated with adverse effects, significant improvement in renal function was not observed immediately after administration. Long-term follow-up is necessary to determine whether MSC administration affects disease progression in cats with CKD.

Implications of mesenchymal stem cells in regenerative medicine

Mesenchymal stem cells (MSCs) are a population of multipotent progenitors which reside in bone marrow, fat, and some other tissues and can be isolated from various adult and fetal tissues. Self-renewal potential and multipotency are MSC's hallmarks. They have the capacity of proliferation and differentiation into a variety of cell lineages like osteoblasts, condrocytes, adipocytes, fibroblasts, cardiomyocytes. MSCs can be identified by expression of some surface molecules like CD73, CD90, CD105, and lack of hematopoietic specific markers including CD34, CD45, and HLA-DR. They are hopeful tools for regenerative medicine for repairing injured tissues. Many studies have focused on two significant features of MSC therapy: (I) systemically administered MSCs home to sites of ischemia or injury, and (II) MSCs can modulate T-cell-mediated immunological responses. MSCs express chemokine receptors and ligands involved in cells migration and homing process. MSCs induce immunomedulatory effects on the innate (dendritic cells, monocyte, natural killer cells, and neutrophils) and the adaptive immune system cells (T helper-1, cytotoxic T lymphocyte, and B lymphocyte) by secreting soluble factors like TGF-β, IL-10, IDO, PGE-2, sHLA-G5, or by cell-cell interaction. In this review, we discuss the main applications of mesenchymal stem in Regenerative Medicine and known mechanisms of homing and Immunomodulation of MSCs.

Effects of mesenchymal stromal cells on human myeloid dendritic cell differentiation and maturation in a humanized mouse model

Mesenchymal stromal cells (MSCs) have shown promise as cellular therapy in allogeneic transplantation, although the precise mechanisms underlying their benefit in clinical trials are difficult to study. We previously demonstrated that MSCs exert immunoregulatory effects in mouse bone marrow-derived dendritic cell (DC) culture. Since mouse studies do not reliably reproduce human events, we used a humanized mouse model to study the immunomodulatory effects of human MSCs on human DC immunobiology. Humanized mice were established by injection of cord blood CD34(+) cells into NOD.Cg-Prkdc(scid) Il2rg(tm1Wjl/SzJ) (NOD scid gamma, NSG) mice. Human cells were detected in the mouse bone marrow, blood, and spleen 12weeks after transplantation. Human DCs were differentiated from humanized mouse bone marrow cells during human MSC co-culture. MSCs inhibited DC differentiation and kept DCs in an immature state as demonstrated by phenotype and function. In conclusion, humanized mouse models represent a useful method to study the function of human MSCs on human DC immunobiology.

Randomized, double-blind, phase I/II study of intravenous allogeneic mesenchymal stromal cells in acute myocardial infarction

BACKGROUND AIMS

Cell therapy is promising as an exploratory cardiovascular therapy. We have recently developed an investigational new drug named Stempeucel (bone marrow-derived allogeneic mesenchymal stromal cells) for patients with acute myocardial infarction (AMI) with ST-segment elevation. A phase I/II randomized, double-blind, single-dose study was conducted to assess the safety and efficacy of intravenous administration of Stempeucel versus placebo (multiple electrolytes injection).

METHODS

Twenty patients who had undergone percutaneous coronary intervention for AMI were randomly assigned (1:1) to receive intravenous Stempeucel or placebo and were followed for 2 years.

RESULTS

The number of treatment-emergent adverse events observed were 18 and 21 in the Stempeucel and placebo groups, respectively. None of the adverse events were related to Stempeucel according to the investigators and independent data safety monitoring board. There was no serious adverse event in the Stempeucel group and there were three serious adverse events in the placebo group, of which one had a fatal outcome. Ejection fraction determined by use of echocardiography showed improvement in both Stempeucel (43.06% to 47.80%) and placebo (43.44% to 45.33%) groups at 6 months (P = 0.26). Perfusion scores measured by use of single-photon emission tomography and infarct volume measured by use of magnetic resonance imaging showed no significant differences between the two groups at 6 months.

CONCLUSIONS

This study showed that Stempeucel was safe and well tolerated when administered intravenously in AMI patients 2 days after percutaneous coronary intervention. The optimal dose and route of administration needs further evaluation in larger clinical trials (http://clinicaltrials.gov/show/NCT00883727).

Biotechnological and biomedical applications of mesenchymal stem cells as a therapeutic system

Mesenchymal stem cells (MSCs) are non-hematopoietic, multipotent progenitor cells which reside in bone marrow (BM), support homing of hematopoietic stem cells (HSCs) and self-renewal in the BM. These cells have the potential to differentiate into tissues of mesenchymal origin, such as fibroblasts, adipocytes, cardiomyocytes, and stromal cells. MSCs can express surface molecules like CD13, CD29, CD44, CD73, CD90, CD166, CXCL12 and toll-like receptors (TLRs). Different factors, such as TGF-β, IL-10, IDO, PGE-2, sHLA-G5, HO, and Galectin-3, secreted by MSCs, induce interaction in cell to cell immunomodulatory effects on innate and adaptive cells of the immune system. Furthermore, these cells can stimulate and increase the TH2 and regulatory T-cells through inhibitory effects on the immune system. MSCs originate from the BM and other tissues including the brain, adipose tissue, peripheral blood, cornea, thymus, spleen, fallopian tube, placenta, Wharton's jelly and umbilical cord blood. Many studies have focused on two significant features of MSC therapy: (I) MSCs can modulate T-cell-mediated immunological responses, and (II) systemically administered MSCs home in to sites of ischemia or injury. In this review, we describe the known mechanisms of immunomodulation and homing of MSCs. As a result, this review emphasizes the functional role of MSCs in modulating immune responses, their capability in homing to injured tissue, and their clinical therapeutic potential.

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

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

Compare the effects of intravenous and intraperitoneal mesenchymal stem cell transplantation on ultrafiltration failure in a rat model of chronic peritoneal dialysis

AIM

The purpose of this study was to compare the possible healing effects of intraperitoneal (IP) and intravenous (IV) mesenchymal stem cell (MSC) transplantation on ultrafiltration failure (UFF) in a chronic rat model of peritoneal dialysis (PD).

METHODS

Rats were initially divided into two groups. The UFF-group received once-daily IP injections of 20 mL of 3.86% glucose PD solution for six weeks to stimulate the development of UFF, and a control group received no injections. The UFF group was sub-divided into four groups: an UFF-C group, a MSC-IP group, a MSC-IV group and a placebo (P) group. Peritoneal equilibration tests (PETs) and peritoneal biopsies were performed in the control and UFF-C groups. MSCs were administered by IP injection in the MSC-IP group and by IV injection in the MSC-IV group. The P group received IP injection of placebo. PETs and peritoneal biopsies were performed in the MSC-IP, MSC-IV and P groups at the three weeks after receiving MSCs or placebo.

RESULTS

When compared with the control group, ultrafiltration capacity significantly decreased, and the submesothelial thickness increased in the UFF-C and P group, but there were no differences between the control and MSC-IP and MSC-IV groups. The rate of glucose transport was high in the UFF-C and P group compared with the control group, and D/PCr rates in the UFF-C and P group were lower than in the control group. However, D/D0glucose was higher and D/PCr was lower in the MSC-IP group than in the UFF-C and P groups, but D/D0glucose rate of MSC-IV group similar to UFF-C and P groups and there was no difference between MSC-IV group and the other groups in terms of D/PCr rates. The MSC-IP, MSC-IV and P groups had significantly decreased tumor necrosis factor α concentrations compared with the UFF-C group. MSC-IP group had lower levels of TGF-β1 compared with the P group; MSC-IP group had also lower levels of interleukin-6 compared with UFF-C group.

CONCLUSION

The UFF group had a high permeability UFF. These results showed that IV and IP MSC transplantation exerted positive effects on UFF in a chronic rat model of PD. However, healing effect of small solute transport in MSC-IP group was better than MSC-IV group. IP MSC transplantation may be more effective than IV MSC transplantation for the renewal of the peritoneum in chronic PD patients with UFF.

Composite tissue allotransplantation and dysregulation in tissue repair and regeneration: a role for mesenchymal stem cells

Vascularized composite tissue allotransplantation is a rapidly evolving area that has brought technological advances to the forefront of plastic surgery, hand surgery, and transplant biology. Composite tissue allografts (CTAs) may have profound functional, esthetic, and psychological benefits, but carry with them the risks of life-long immunosuppression and the inadequate abilities to monitor and prevent rejection. Allografts may suffer from additional insults further weakening their overall benefits. Changes in local blood flow, lack of fully restored neurologic function, infection, inflammation with subsequent dysregulated regenerative activity, and paucity of appropriate growth factors may all be involved in reducing the potential of CTAs and therefore serve as new therapeutic targets to improve outcomes. Strategies involving minimized immunosuppression and pro-regenerative therapy may provide a greater path to optimizing long-term CTA function. One such strategy may include mesenchymal stem cells (MSCs), which can provide unique anti-inflammatory and pro-regenerative effects. Insights gained from new studies with MSCs on composite allografts, advances in tissue regeneration reported in other MSC-based clinical studies, as well as consideration of newly described capacities of MSCs, may provide new regenerative based strategies for the care of CTAs.

Safety and efficacy of intravenous infusion of allogeneic cryopreserved mesenchymal stem cells for treatment of chronic kidney disease in cats: results of three sequential pilot studies

Introduction

Administration of mesenchymal stem cells (MSCs) has been shown to improve renal function in rodent models of chronic kidney disease (CKD), in part by reducing intrarenal inflammation and suppressing fibrosis. CKD in cats is characterized by tubulointerstitial inflammation and fibrosis, and thus treatment with MSCs might improve renal function and urinary markers of inflammation in this disease. Therefore, a series of pilot studies was conducted to assess the safety and efficacy of intravenous administration of allogeneic adipose-derived MSCs (aMSCs) in cats with naturally occurring CKD.

Methods

Cats enrolled in these studies received an intravenous infusion of allogeneic aMSCs every 2 weeks collected from healthy, young, specific pathogen-free cats. Cats in pilot study 1 (six cats) received 2 × 10⁶ cryopreserved aMSCs per infusion, cats in pilot study 2 (five cats) received 4 × 10⁶ cryopreserved aMSCs per infusion, and cats in pilot study 3 (five cats) received 4 × 10⁶ aMSCs cultured from cryopreserved adipose. Serum biochemistry, complete blood count, urinalysis, urine protein, glomerular filtration rate, and urinary cytokine concentrations were monitored during the treatment period. Changes in clinical parameters were compared statistically by means of repeated measures analysis of variance (ANOVA) followed by Bonferroni’s correction.

Results

Cats in pilot study 1 had few adverse effects from the aMSC infusions and there was a statistically significant decrease in serum creatinine concentrations during the study period, however the degree of decrease seems unlikely to be clinically relevant. Adverse effects of the aMSC infusion in cats in pilot study 2 included vomiting (2/5 cats) during infusion and increased respiratory rate and effort (4/5 cats). Cats in pilot study 3 did not experience any adverse side effects. Serum creatinine concentrations and glomerular filtration rates did not change significantly in cats in pilot studies 2 and 3.

Conclusions

Administration of cryopreserved aMSCs was associated with significant adverse effects and no discernible clinically relevant improvement in renal functional parameters. Administration of aMSCs cultured from cryopreserved adipose was not associated with adverse effects, but was also not associated with improvement in renal functional parameters.

Potential role of mesenchymal stromal cells in pancreatic islet transplantation

Pancreatic islet transplantation is an attractive option for treatment of type 1 diabetes mellitus but maintaining long term islet function remains challenging. Mesenchymal stromal cells (MSCs), derived from bone marrow or other sources, are being extensively investigated in the clinical setting for their immunomodulatory and tissue regenerative properties. Indeed, MSCs have been already tested in some feasibility studies in the context of islet transplantation. MSCs could be utilized to improve engraftment of pancreatic islets by suppressing inflammatory damage and immune mediated rejection. In addition to their immunomodulatory effects, MSCs are known to provide a supportive microenvironmental niche by secreting paracrine factors and depositing extracellular matrix. These properties could be used for in vivo co-transplantation to improve islet engraftment, or for in vitro co-culture to prime freshly isolated islets prior to implantation. Further, tissue specific pancreatic islet derived MSCs may open new opportunities for its use in islet transplantation as those cells might be more physiological to pancreatic islets.

The allogeneic umbilical cord mesenchymal stem cells regulate the function of T helper 17 cells from patients with rheumatoid arthritis in an in vitro co-culture system

Background

Previous in vivo studies have shown that mesenchymal stem cell (MSC) transplantation significantly improves the condition of a number of autoimmune diseases including autoimmune cerebrospinal meningitis, multiple sclerosis, glomerulonephritis and systemic lupus erythematosus.

Methods

To investigate the immunoregulatory effect of stem cell transplantation, human umbilical cord MSCs were co-cultured with peripheral blood mononuclear cells (PBMCs) from patients with rheumatoid arthritis (RA). Orphan nuclear receptor gamma (ROR-γ) mRNA and protein expression was detected with real-time PCR and Western blotting. Interleukin (IL)-17, IL-6 and tumor necrosis factor (TNF-α) in the cell culture supernatant were measured using a flow cytometric bead capture method.

Results

After 72 hours of co-culture, the mRNA and protein expression levels of ROR-γ in co-cultured PBMCs were decreased compared with that in PBMC of RA patients cultured alone (p < 0.05). Moreover, the decrement was positively related to the disease activity of RA (p < 0.05). Decreased secretion of IL-17, TNF-α and IL-6 were also found in co-culture supernatants of PBMCs from patients with severe and moderate disease activity, but not in supernatant from PBMCs cultured alone. The decreased cytokine expression levels were positively correlated to the concentrations of MSCs. In contrast, PBMCs from healthy controls or patients with mild RA did not show significant differences in ROR-γ expression or cytokine secretion following co-culture with MSCs as compared with those cultured alone.

Conclusions

In vitro co-culture with MSCs down-regulated the inflammatory response of PBMCs from RA patients with severe disease activity, but had no significant effect on PBMCs from healthy controls or patients with mild disease activity, suggesting that the immunoregulatory role of MSCs may associate with the occurrence of inflammatory mediators.

[The role of adult bone marrow derived mesenchymal stem cells in the repair of tissue injuries]

Mesenchymal stem cells, which reside in adult bone marrow are multipotent, have an excellent regeneration potential for tissue repair. These cells are able to differentiate in cell culture not only into mesodermal lineages but also into other lineages of ectodermal and endodermal cells. This regenerative process is assisted by application of bioactive molecules, specific growth factors and biomaterials (scaffolds). The cell therapy is successfully used in the treatment of bone defects, nonunions, osteoblasts formed from the mesenchymal stem cells. At present, there are encouraging data in the clinical practice. The mesenchymal stem cell seems to be successful in the regeneration of articular cartilage. There are further promising data for the application of mesenchymal stem cells in the treatment of myocardial infarction, neurologic diseases, liver and kidney diseases and injuries and diabetes mellitus. The aim of this review is to survey the molecular characteristics of mesenchymal stem cells and specific growth factors using the data of preclinical investigations and to call attention to their possible clinical application.

Mesenchymal stem cells ameliorate postpyelonephritic renal scarring in rats

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Can gap junctions deliver?

In vivo delivery of small interfering RNAs (siRNAs) to target cells via the extracellular space has been hampered by dilution effects and immune responses. Gap junction-mediated transfer between cells avoids the extracellular space and its associated limitations. Because of these advantages cell based delivery via gap junctions has emerged as a viable alternative for siRNA or miRNA delivery. Here we discuss the advantages and disadvantages of extracellular delivery and cell to cell delivery via gap junction channels composed of connexins. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.

Adipose tissue-derived mesenchymal stem cells improve revascularization outcomes to restore renal function in swine atherosclerotic renal artery stenosis

Reno-protective strategies are needed to improve renal outcomes in patients with atherosclerotic renal artery stenosis (ARAS). Adipose tissue-derived mesenchymal stem cells (MSCs) can promote renal regeneration, but their potential for attenuating cellular injury and restoring kidney repair in ARAS has not been explored. We hypothesized that replenishment of MSC as an adjunct to percutaneous transluminal renal angioplasty (PTRA) would restore renal cellular integrity and improve renal function in ARAS pigs. Four groups of pigs (n = 7 each) were studied after 16 weeks of ARAS, ARAS 4 weeks after PTRA and stenting with or without adjunct intrarenal delivery of MSC (10 × 10(6) cells), and controls. Stenotic kidney blood flow (renal blood flow [RBF]) and glomerular filtration rate (GFR) were measured using multidetector computer tomography (CT). Renal microvascular architecture (micro-CT), fibrosis, inflammation, and oxidative stress were evaluated ex vivo. Four weeks after successful PTRA, mean arterial pressure fell to a similar level in all revascularized groups. Stenotic kidney GFR and RBF remained decreased in ARAS (p = .01 and p = .02) and ARAS + PTRA (p = .02 and p = .03) compared with normal but rose to normal levels in ARAS + PTRA + MSC (p = .34 and p = .46 vs. normal). Interstitial fibrosis, inflammation, microvascular rarefaction, and oxidative stress were attenuated only in PTRA + MSC-treated pigs. A single intrarenal delivery of MSC in conjunction with renal revascularization restored renal hemodynamics and function and decreased inflammation, apoptosis, oxidative stress, microvascular loss, and fibrosis. This study suggests a unique and novel therapeutic potential for MSC in restoring renal function when combined with PTRA in chronic experimental renovascular disease.

Autologous bone marrow cell infusions suppress tumor initiation in hepatocarcinogenic mice with liver cirrhosis

We have previously reported the efficacy and safety of autologous bone marrow cell infusion (ABMi) therapy for liver cirrhosis patients without hepatocellular carcinoma in a multicenter clinical trial. However, since liver cirrhosis is highly oncogenic, evaluation of the effects of ABMi on the mechanisms of hepatocarcinogenesis is of great importance. Therefore, frequent ABMi was performed in hepatocarcinogenic mice, and its effects on hepatocarcinogenesis were analyzed. The N-nitrosodiethylamine (DEN)/green fluorescent protein (GFP)-carbon tetrachloride (CCl(4) ) model was developed by administering DEN once, followed by repeated administration of CCl(4) intraperitoneally as for the control group. In the administration (ABMi) group, GFP-positive bone marrow cells were infused through a tail vein. The kinetics of hepatocarcinogenesis were evaluated histologically 4.5 months after DEN treatment. At 4.5 months, there was significantly lower incidence of foci and tumors in the ABMi group, and they were smaller in number, while their size was almost equal. No GFP-positive tumors were found in ABMi livers. Moreover, ABMi livers showed significantly reduced liver fibrosis, consistent with significantly lower 8-hydroxy-2'-deoxyguanosine levels, higher superoxide dismutase activity, and increased nuclear translocation of nuclear factor-erythroid 2 p45-related factor 2. These results demonstrate that frequent ABMi might contribute to suppressed tumor initiation during stages of hepatocarcinogenesis, consistent with improvements in liver fibrosis and stabilization of redox homeostasis.

Stem cells in liver failure

Orthotopic liver transplantation (OLT) represents the only reliable therapeutic approach for acute liver failure (ALF), liver failure associated to end-stage chronic liver diseases (CLD) and non-metastatic liver cancer. The clinical impact of liver failure is relevant because of the still high ALF mortality and the increasing worldwide prevalence of cirrhosis that, in turn, is the main predisposing cause for hepatocellular carcinoma (HCC). Moreover, in the next decade because an increased number of patients reaching end-stage disease and requiring OLT may face a shortage of donor livers. This clinical scenario led several laboratories to explore the feasibility and efficiency of alternative approaches, involving cellular therapy, to counteract liver failure. The present chapter overviews results and concepts emerged from recent experimental and clinical studies in which adult or embryonic hepatocytes, hepatic stem/progenitor cells, induced pluripotent stem (iPS) cells as well as extrahepatic stem cells have been used as putative transplantable cell sources.

Original article anti-oxidant pathways are stimulated by mesenchymal stromal cells in renal repair after ischemic injury

BACKGROUND AIMS

Ischemia-reperfusion (IR) injury is a common cause of acute renal failure. Bone marrow (BM)-derived mesenchymal stromal cells (MSC) delivered after renal IR are renoprotective, but knowledge of the protective mechanism is still in development. This investigation analyzed the protective molecular mechanisms of MSC, in particular relating to modulated oxidative stress.

METHODS

In vivo and in vitro models of renal IR were analyzed with and without MSC. In vivo, adult male Sprague-Dawley rats were subjected to 40-min unilateral renal IR. Rat BM-derived MSC were administered at 24 h post-IR (IR + MSC). Other groups had IR but no MSC, or MSC but no ischemia (all groups n = 4). Apoptosis, inflammation, oxidative stress and reparative signal transduction molecules or growth factors were studied 4 days post-IR. In vitro, protection by MSC against oxidative stress (0.4 mm hydrogen peroxide) was investigated using rat renal tubular epithelial cells (NRK52E) with or without MSC in co-culture (tissue culture trans-well inserts), followed by similar analyses to the in vivo investigation.

RESULTS

In vivo, kidneys of IR + MSC animals had significantly increased cell proliferation/regeneration (cells positive for proliferating cell nuclear antigen, expression of epidermal growth factor), increased heme-oxygenase-1 (improved cell survival, anti-oxidant) and decreased 8-OHdG (decreased oxidative stress). In vitro, MSC delivered with oxidative stress significantly decreased apoptosis and Bax (pro-apoptotic protein), and increased mitosis and phospho-ERK1/2, thereby minimizing the damaging outcome and maximizing the regenerative effect after oxidative stress.

CONCLUSIONS

The benefits of MSC, in IR, were primarily pro-regenerative, sometimes anti-apoptotic, and novel anti-oxidant mechanisms were identified.

Mesenchymal stem cells: from experiment to clinic

There is currently much interest in adult mesenchymal stem cells (MSCs) and their ability to differentiate into other cell types, and to partake in the anatomy and physiology of remote organs. It is now clear these cells may be purified from several organs in the body besides bone marrow. MSCs take part in wound healing by contributing to myofibroblast and possibly fibroblast populations, and may be involved in epithelial tissue regeneration in certain organs, although this remains more controversial. In this review, we examine the ability of MSCs to modulate liver, kidney, heart and intestinal repair, and we update their opposing qualities of being less immunogenic and therefore tolerated in a transplant situation, yet being able to contribute to xenograft models of human tumour formation in other contexts. However, such observations have not been replicated in the clinic. Recent studies showing the clinical safety of MSC in several pathologies are discussed. The possible opposing powers of MSC need careful understanding and control if their clinical potential is to be realised with long-term safety for patients.

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

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

In vivo effect of bone marrow-derived mesenchymal stem cells in a rat kidney transplantation model with prolonged cold ischemia

Brain death and prolonged cold ischemia are major contributors to the poorer long-term outcome of transplants from deceased donor kidney transplants, with an even higher impact if expanded criteria donors ('marginal organs') are used. Targeting ischemia-reperfusion injury-related intragraft inflammation is an attractive concept to improve the outcome of those grafts. As mesenchymal stem cells (MSCs) express both immunomodulatory and tissue repair properties, we evaluated their therapeutic efficacy in a rat kidney transplant model of prolonged cold ischemia. The in vitro immunomodulatory capacity of bone marrow-derived rat MSCs was tested in co-cultures with rat lymph node cells. For in vivo studies, Dark Agouti rat kidneys were cold preserved and transplanted into Lewis rats. Syngeneic Lewis MSCs were administered intravenously. Transplants were harvested on day 3, and inflammation was examined by quantitative RT-PCR and histology. Similarly to MSCs from other species, rat MSCs in vitro also showed a dose-dependent immunomodulatory capacity. Most importantly, in vivo administration of MSCs reduced the intragraft gene expression of different pro-inflammatory cytokines, chemokines, and intercellular adhesion molecule-1. In addition, fewer antigen-presenting cells were recruited into the renal allograft. In conclusion, rat MSCs ameliorate inflammation induced by prolonged cold ischemia in kidney transplantation.

Evaluation of intrarenal mesenchymal stem cell injection for treatment of chronic kidney disease in cats: a pilot study

The feasibility of autologous intrarenal mesenchymal stem cell (MSC) therapy in cats with chronic kidney disease (CKD) was investigated. Six cats (two healthy, four with CKD) received a single unilateral intrarenal injection of autologous bone marrow-derived or adipose tissue-derived MSC (bmMSC or aMSC) via ultrasound guidance. Minimum database and glomerular filtration rate (GFR) via nuclear scintigraphy were determined pre-injection, at 7 days and at 30 days post-injection. Intrarenal injection did not induce immediate or long-term adverse effects. Two cats with CKD that received aMSC experienced modest improvement in GFR and a mild decrease in serum creatinine concentration. Despite the possible benefits of intrarenal MSC injections for CKD cats, the number of sedations and interventions required to implement this approach would likely preclude widespread clinical application. We concluded that MSC could be transferred safely by ultrasound-guided intrarenal injection in cats, but that alternative sources and routes of MSC therapy should be investigated.

Approaches to avoid immune responses induced by repeated subcutaneous injections of allogeneic umbilical cord tissue-derived cells

BACKGROUND

Cellular treatments for repairing diseased tissues represent a promising clinical strategy. Umbilical cord tissue-derived cells (UTC) are a unique source of cells with a low immunogenic profile and potential for tissue repair. By using UTC from miniature swine, we previously demonstrated that despite their low immunogenic phenotype, UTC could induce an immune response under certain inflammatory conditions and after multiple subcutaneous (SC) injections. Given that repeat dosing of cells may be necessary to achieve a lasting therapeutic benefit, in this study, we examined approaches to avoid an immune response to multiple SC injections of UTC.

METHODS

By using in vitro and in vivo measures of sensitization to SC cellular injections, we assessed the effects of varying the location of administration site, prolongation of timing between injections, and use of immunosuppressive treatments on repeated cellular injections in Massachusetts General Hospital major histocompatibility complex-defined miniature swine.

RESULTS

Although under normal conditions, a single SC injection of major histocompatibility complex-mismatched UTC did not induce a detectable immune response, multiple SC injections of UTC demonstrated rapid humoral and cell-mediated immune responses. Avoidance of an immune response to repeat SC injection was achieved by concurrent immunosuppression with each dose of UTC.

CONCLUSIONS

UTC and other similar cell types believed to be nonimmunogenic have the potential to induce immune responses under certain conditions. These studies provide important considerations and guidelines for preclinical studies investigating allogeneic cellular therapies.

Immunosuppressive mechanisms of embryonic stem cells and mesenchymal stem cells in alloimmune response

Although both embryonic stem cells (ESCs) and mesenchymal stem cells (MSCs) are known to have immunosuppressive effects, the mechanisms of immunosuppression are still controversial. Both types of stem cells suppressed not only the proliferation but also survival of CD4(+) T cells in vitro. They suppressed secretion of various cytokines (IL-2, IL-12, IFN-γ, TNF-α, IL-4, IL-5, IL-1β, and IL-10), whereas there was no change in the levels of TGF-β or IDO. Classic and modified transwell experiments demonstrated that immunosuppressive activities were mainly mediated by cell-to-cell contact. Granzyme B in the ESCs played a significant role in their immunosuppression, whereas PDL-1, Fas ligand, CD30 or perforin was not involved in the contact-dependent immunosuppression. However, none of the above molecules played a significant role in the immunosuppression by the MSCs. Interestingly, both stem cells increased the proportion of Foxp3(+) regulatory T cells. Our results showed that both ESCs and MSCs suppressed the survival as well as the proliferation of T cells by mainly contact-dependent mechanisms and increased the proportion of regulatory T cells. Granzyme B was involved in immunosuppression by the ESCs in a perforin-independent manner.

The regenerative potential of the kidney: what can we learn from developmental biology?

Cell turnover in the healthy adult kidney is very slow but the kidney has a strong capacity for regeneration after acute injury. Although many molecular aspects of this process have been clarified, the source of the newly-formed renal epithelial cells is still being debated. Several studies have shown, moreover, that the repair of injured renal epithelium starts from mature tubular cells, which enter into an activated proliferative state characterized by the reappearance of mesenchymal markers detectable during nephrogenesis, thus pointing to a marked plasticity of renal epithelial cells. The regenerative potential of mature epithelial cells might stem from their almost unique morphogenetic process. Unlike other tubular organs, all epithelial and mesenchymal cells in the kidney derive from the same germ layer, the mesoderm. In a fascinating view of vertebrate embryogenesis, the mesoderm might be seen as a cell layer capable of oscillating between epithelial and mesenchymal states, thus acquiring a remarkable plasticity that lends it an extended potential for innovation and a better control of three-dimensional body organization. The renal papilla contains a population of cells with the characteristic of adult stem cells. Mesenchymal stromal stem cells (MSC) have been found to reside in the connective tissue of most organs, including the kidney. Recent studies indicate that the MSC compartment extends throughout the body postnatally as a result of its perivascular location. Developmental biology suggests that this might be particularly true of the kidney and that the papilla might represent the perivascular renal stem cell niche. The perivascular niche hypothesis fits well with the evolving concept of the stem cell niche as an entity of action. It is its dynamic capability that makes the niche concept so important and essential to the feasibility of regenerative medicine.

Mesenchymal stem cell therapy for chronic renal failure

IMPORTANCE OF THE FIELD

Chronic kidney disease (CKD) has become a worldwide public health problem. Renal transplantation is the treatment of choice for end-stage renal disease, but is limited by a small number of organ donors and the immune barrier. To overcome these problems, new therapeutic strategies for tissue repair have recently emerged.

AREAS COVERED IN THIS REVIEW

We discuss the therapeutic potential of mesenchymal stem cells (MSCs) in kidney injury and examine the latest reports providing evidence supporting MSC efficacy in the treatment of chronic renal failure (CRF).

WHAT THE READER WILL GAIN

MSCs improve histological and functional outcomes in various CRF model systems. Paracrine effects rather than transdifferentiation might result in the prevention of progressive renal failure. In addition, MSCs can reprogram kidney cell differentiation, and modulate neo-kidney transplantation in CRF.

TAKE HOME MESSAGE

Although many practical problems remain to be addressed, treatment with MSCs will enter the mainstream of CRF treatment.

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

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

Bone marrow mesenchymal stem cells

Following the identification of bone marrow multipotent cells that could adhere to plastic and differentiate along numerous mesenchymal lineages in vitro, a considerable effort has been invested in characterizing and expanding these cells, which are now called "mesenchymal stem cells" (MSCs), in vitro. Over the years, numerous lines of evidence have been provided in support of their plasticity, their extraordinary immunomodulatory properties, their potential use for tissue engineering purposes, as well as their ability to be recruited to sites of injury, where they might contribute a "natural in vivo system for tissue repair." Moreover, some studies have attempted the characterization of their cell-surface specific antigens and of their anatomical location in vivo. Lastly, it has been shown that similar cells could be also isolated from organs other than the bone marrow. Despite this impressive body of investigations, numerous questions related to the developmental origin of these cells, their proposed pluripotency, and their role in bone modeling and remodeling and tissue repair in vivo are still largely unanswered. In addition, both a systematic phenotypic in vivo characterization of the MSC population and the development of a reproducible and faithful in vivo assay that would test the ability of MSCs to self-renew, proliferate, and differentiate in vivo are just beginning. This brief review summarizes the current knowledge in the field of study of MSCs and the outstanding questions.

Deficiency of either P-glycoprotein or breast cancer resistance protein protect against acute kidney injury

The kidney has a high capacity to regenerate after ischemic injury via several mechanisms, one of which involves bone marrow-derived (stem) cells. The ATP binding cassette transporters, P-glycoprotein and breast cancer resistance protein, are determinants for the enriched stem and progenitor cell fraction in bone marrow. Because they are upregulated after acute kidney injury, we hypothesized that both efflux pumps may play a role in protecting against renal injury. Surprisingly, transporter-deficient mice were protected against ischemia-induced renal injury. To further study this, bone marrow from irradiated wild-type mice was reconstituted by bone marrow from wild-type, P-glycoprotein- or breast cancer resistance protein-deficient mice. Four weeks later, kidney injury was induced and its function evaluated. Significantly more bone marrow-derived cells were detected in kidneys grafted with transporter-deficient bone marrow. A gender mismatch study suggested that cell fusion of resident tubular cells with bone marrow cells was unlikely. Renal function analyses indicated an absence of renal damage following ischemia-reperfusion in animals transplanted with transporter-deficient bone marrow. When wild-type bone marrow was transplanted in breast cancer resistance protein-deficient mice this protection is lost. Furthermore, we demonstrate that transporter-deficient bone marrow contained significantly more monocytes, granulocytes, and early outgrowth endothelial progenitor cells.

Endovenous administration of bone-marrow-derived multipotent mesenchymal stromal cells prevents renal failure in diabetic mice

Twenty-five to 40% of diabetic patients develop diabetic nephropathy, a clinical syndrome that comprises renal failure and increased risk of cardiovascular disease. It represents the major cause of chronic kidney disease and is associated with premature morbimortality of diabetic patients. Multipotent mesenchymal stromal cells (MSC) contribute to the regeneration of several organs, including acutely injured kidney. We sought to evaluate if MSC protect kidney function and structure when endovenously administered to mice with severe diabetes. A month after nonimmunologic diabetes induction by streptozotocin injection, C57BL/6 mice presented hyperglycemia, glycosuria, hypoinsulinemia, massive beta-pancreatic islet destruction, low albuminuria, but not renal histopathologic changes (DM mice). At this stage, one group of animals received the vehicle (untreated) and other group received 2 doses of 0.5 x 10(6) MSC/each (MSC-treated). Untreated DM mice gradually increased urinary albumin excretion and 4 months after diabetes onset, they reached values 15 times higher than normal animals. In contrast, MSC-treated DM mice maintained basal levels of albuminuria. Untreated DM mice had marked glomerular and tubular histopathologic changes (sclerosis, mesangial expansion, tubular dilatation, proteins cylinders, podocytes lost). However, MSC-treated mice showed only slight tubular dilatation. Observed renoprotection was not associated with an improvement in endocrine pancreas function in this animal model, because MSC-treated DM mice remained hyperglycemic and hypoinsulinemic, and maintained few remnant beta-pancreatic islets throughout the study period. To study MSC biodistribution, cells were isolated from isogenic mice that constitutively express GFP (MSC(GFP)) and endovenously administered to DM mice. Although at very low levels, donor cells were found in kidney of DM mice 3 month after transplantation. Presented preclinical results support MSC administration as a cell therapy strategy to prevent chronic renal diseases secondary to diabetes.

Autologous and allogeneic marrow stromal cells are safe and effective for the treatment of acute kidney injury

Acute kidney injury (AKI) is a major clinical problem associated with high morbidity and mortality. Likely due to its complex pathophysiology, therapies with a single pharmacological agent have generally failed to improve outcomes. In contrast, stem cell-based interventions utilize these cells' ability to simultaneously target multiple pathophysiological components of AKI and thus represent a promising new tool for the treatment of AKI. The aims of the this study were to investigate the long-term outcome and safety of treatment with autologous and allogeneic mesenchymal stem cells (MSCs) after AKI and the role of vascular endothelial growth factor (VEGF) as one of the principal paracrine mediators of renoprotection of MSCs. MSC administration after AKI was not associated with adverse events and proved to be renoprotective in animals with severe renal failure. Identical doses of autologous MSC were more effective than allogeneic. At 3 months, MSCs were not engrafted in any tissues except in the bone marrow in 50% of animals given the highest allogeneic cell dose. There was no long-term fibrotic response in the kidneys attributable to MSC therapy, and animals with severe AKI were protected from development of fibrotic lesions after AKI. Furthermore, this study establishes VEGF as a critical factor mediating renal recovery. VEGF knockdown by small-interfering RNA reduced effectiveness of MSCs significantly and decreased survival. In summary, our results show that both autologous and allogeneic MSC are safe and effective in AKI, and importantly, reduce late renal fibrosis and loss of renal function in surviving animals and that VEGF is a critical factor in renoprotection by MSCs. Together, we posit that these data provide further justification for the conduct of clinical trails in which AKI is treated with MSC.

Ultrastructural insights in the interface between generated renal tubules and a polyester interstitium

In regenerative medicine, stem/progenitor cells are emerging as potential candidates for the treatment of renal failure. However, the mechanism of regeneration of renal tubules from stem/progenitor cells is not well-elucidated. In this study, a new method was developed for the generation of tubules replacing coating by extracellular matrix proteins. Renal stem/progenitor cells are mounted between layers of polyester fleece. This artificial interstitium supports spatial development of tubules within 13 days of perfusion culture in chemically defined Iscove's modified Dulbecco's medium (IMDM) containing aldosterone as the tubulogenic factor. Whole mount label by soybean agglutinin (SBA) showed that generated tubules exhibited a lumen and a continuously developed basal lamina. Immuno-labeling for cytokeratin Endo-A demonstrated the presence of isoprismatic epithelial cells, and laminin gamma1, occludin, and Na/K-ATPase alpha5 labeling revealed typical features of a polarized epithelium. To get first insight in the interface between tubules and polyester interstitium, transmission electron microscopy (TEM) was performed. The results showed that the generated tubules exhibited polar differentiation with a continuously developed basal lamina consisting of a lamina rara interna, lamina densa, and lamina rara externa. Collagen type III was found to be the linking molecule between the basal lamina and the surrounding polyester fibers by immuno labeling studies. Thus, the findings demonstrate that the spatial development involves the interface between the tubular basal lamina and the polyester interstitium of tubules and is not restricted to the epithelial portion.

Kidney-derived stromal cells modulate dendritic and T cell responses

Multipotent mesenchymal stromal cells from the bone marrow ameliorate acute kidney injury through a mechanism other than transdifferentiation into renal tissue. Stromal cells exert immunoregulatory effects on dendritic and T cells, both of which are important in the pathophysiology of immune-mediated kidney injury. We hypothesized that similar cells with immunoregulatory function exist within the adult kidney. We isolated murine kidney-derived cells with morphologic features, growth properties, and an immunophenotype characteristic of mesenchymal stromal cells. These cells lacked lineage markers and could be differentiated into mesodermal cell lineages, including osteocytes and adipocytes. Furthermore, these kidney-derived cells induced the generation of bone marrow-derived dendritic cells with significantly reduced MHC II expression, increased CD80 expression, increased IL-10 production and the inability to stimulate CD4+ T cell proliferation in allogeneic and nominal antigen-specific cultures. Experiments in mixed and transwell cultures demonstrated that the production of soluble immune modulators, such as IL-6, was responsible for these effects on dendritic cell differentiation and maturation. Contact-dependent mechanisms, however, inhibited mitogenic T cell proliferation. In summary, kidney-derived cells may suppress inflammation in the kidney in vivo; a better understanding of their biology could have therapeutic implications in a wide variety of immune-mediated kidney diseases.

Bone marrow progenitors from animals with chronic renal failure lack capacity of in vitro proliferation

BACKGROUND

An interesting way to regenerate a kidney is an autologous bone marrow transplantation. The aim of this study was to examine whether chronic kidney disease influenced bone marrow progenitors.

METHODS

Wistar male rats included group I (n = 4, chronic kidney disease 1/2, CKD 1/2) that underwent right nephrectomy. In group II (n = 3, chronic kidney disease 5/6, CKD 5/6) underwent removal of the right kidney and approximately one-third of the cortex of the left kidney. Animals in the control group (n = 4) were intact. Bone marrow cells obtained from femurs were separated using a CD34 Micro-Beads magnetic isolation kit. Isolated cells were counted using a trypan blue exclusion test. Numbers of isolated cells were presented as mean values with standard deviation with P < .05 considered significant. CD34(-) cells were cultivated and observed to the passage 6.

RESULTS

The CKD rat model was used for in vitro experiments. There were no differences in cell numbers isolated from control rats versus both CKD rats. No differences were observed in CD34(-) cells after separation when compared to controls. Cell morphology was similar in primary CD34(-) cultures during the first days of primary culture. CD34(-) primary cultures established from chronic renal failure rats collapsed within 2 weeks. No differences were found in CD34(+) cell number after isolation when compared with controls. These cells did not form a monolayer. Cells in cultures established from control animals resembled normal fibroblast-like morphology of mesenchymal stem cells during 3 months.

CONCLUSIONS

Bone marrow cells from chronic renal failure rats showed no capacity for in vitro proliferation. We speculated that bone marrow cells obtained from renal chronic failure patients may not be useful for autologous cell transplantation.

Fgf9 signaling regulates small intestinal elongation and mesenchymal development

Short bowel syndrome is an acquired condition in which the length of the small intestine is insufficient to perform its normal absorptive function. Current therapies are limited as the developmental mechanisms that normally regulate elongation of the small intestine are poorly understood. Here, we identify Fgf9 as an important epithelial-to-mesenchymal signal required for proper small intestinal morphogenesis. Mouse embryos that lack either Fgf9 or the mesenchymal receptors for Fgf9 contained a disproportionately shortened small intestine, decreased mesenchymal proliferation, premature differentiation of fibroblasts into myofibroblasts and significantly elevated Tgfbeta signaling. These findings suggest that Fgf9 normally functions to repress Tgfbeta signaling in these cells. In vivo, a small subset of mesenchymal cells expressed phospho-Erk and the secreted Tgfbeta inhibitors Fst and Fstl1 in an Fgf9-dependent fashion. The p-Erk/Fst/Fstl1-expressing cells were most consistent with intestinal mesenchymal stem cells (iMSCs). We found that isolated iMSCs expressed p-Erk, Fst and Fstl1, and could repress the differentiation of intestinal myofibroblasts in co-culture. These data suggest a model in which epithelial-derived Fgf9 stimulates iMSCs that in turn regulate underlying mesenchymal fibroblast proliferation and differentiation at least in part through inhibition of Tgfbeta signaling in the mesenchyme. Taken together, the interaction of FGF and TGFbeta signaling pathways in the intestinal mesenchyme could represent novel targets for future short bowel syndrome therapies.

Immune system in renal injury and repair: burning the candle from both ends?

This brief overview is focused on the inherent duality of immune responses: on the one hand they may induce inflammation and precipitate injury, on the other, a number of examples of participation in organ and tissue repair are growing. These processes will be reviewed from the nephrological stand-point. Specifically, the role of different leukocyte subsets, innate immunity, nitric oxide production, and stem cells, among others, are presented.