Mesenchymal stem cells delivered at the subcapsule of the kidney ameliorate renal disease in the rat remnant kidney model

Does the route matter? A preclinical review of mesenchymal stromal cell delivery to the kidney

Mesenchymal stromal/stem cell (MSC) therapy has been thoroughly tested in preclinical animal models and holds great promise for the treatment of kidney diseases. It is becoming increasingly evident that the efficacy of MSC therapy is dependent on several factors including dosage, the tissue source of MSCs, the route of delivery and timing of administration. In a time where MSC therapy is moving from preclinical research to clinically therapeutic use, the importance of choice of delivery method, modality, and administration route increases. In this review, we provide an overview of the different MSC delivery routes used in preclinical kidney disease models, highlight the recent advances in the field, and summarize studies comparing delivery routes of MSCs to the kidney.

Enhancing the Therapeutic Potential of Mesenchymal Stromal Cell-Based Therapies with an Anti-Fibrotic Agent for the Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) affects 1 in 10 members of the general population, placing these patients at an increasingly high risk of kidney failure. Despite the significant burden of CKD on various healthcare systems, there are no effective cures that reverse or even halt its progression. In recent years, human bone-marrow-derived mesenchymal stromal cells (BM-MSCs) have been recognised as a novel therapy for CKDs, owing to their well-established immunomodulatory and tissue-reparative properties in preclinical settings, and their promising safety profile that has been demonstrated in patients with CKDs from several clinical trials. However, renal fibrosis (scarring), a hallmark of CKD, has been shown to impair the viability and functionality of BM-MSCs post-transplantation. This has suggested that BM-MSCs might require a pre-treatment or adjunct therapy that can enhance the viability and therapeutic efficacy of these stromal cells in chronic disease settings. To address this, recent studies that have combined BM-MSCs with the anti-fibrotic drug serelaxin (RLX), have demonstrated the enhanced therapeutic potential of this combination therapy in normotensive and hypertensive preclinical models of CKD. In this review, a critical appraisal of the preclinical data available on the anti-fibrotic and renoprotective actions of BM-MSCs or RLX alone and when combined, as a treatment option for normotensive vs. hypertensive CKD, is discussed.

Synergic Renoprotective Effects of Combined ASC Therapy with RAAS Blockade in Experimental Advanced CKD

Global prevalence of chronic kidney disease (CKD) has increased considerably in the recent decades. Overactivity of the renin-angiotensin-aldosterone system (RAAS), associated to renal inflammation and fibrosis, contributes to its evolution. The treatments currently employed to control CKD progression are limited and mainly based on the pharmacological inhibition of RAAS, associated with diuretics and immunosuppressive drugs. However, this conservative management promotes only partial deceleration of CKD evolution and does not completely avoid the progression of the disease and the loss of renal function, which motivates the medical and scientific community to investigate new therapeutic approaches to detain renal inflammation/fibrosis and CKD progression. Recent studies have shown the application of mesenchymal stem cells (mSC) to exert beneficial effects on the renal tissue of animals submitted to experimental models of CKD. In this context, the aim of the present study was to evaluate the effects of subcapsular application of adipose tissue-derived mSC (ASC) in rats submitted to the 5/6 renal ablation model, 15 days after the establishment of CKD, when the nephropathy was already severe. We also verify whether ASC associated to Losartan would promote greater renoprotection when compared to the respective monotherapies. Animals were followed until 30 days of CKD, when body weight, systolic blood pressure, biochemical, histological, immunohistochemical, and gene expression analysis were performed. The combination of ASC and Losartan was more effective than Losartan monotherapy in reducing systolic blood pressure and glomerulosclerosis and also promoted the complete normalization of proteinuria and albuminuria, a significant reduction in renal interstitial macrophage infiltration and downregulation of renal IL-6 gene expression. The beneficial effects of ACS are possibly due to the immunomodulatory and anti-inflammatory role of factors secreted by these cells, modulating the local immune response. Although studies are still required, our results demonstrated that a subcapsular inoculation of ASC, associated with the administration of Losartan, exerted additional renoprotective effect in rats submitted to a severe model of established CKD, when compared to Losartan monotherapy, thus suggesting ASC may be a potential adjuvant to RAAS-blockade therapy currently employed in the conservative management of CKD.

Comparing the renoprotective effects of BM-MSCs versus BM-MSC-exosomes, when combined with an anti-fibrotic drug, in hypertensive mice

Fibrosis, a hallmark of chronic kidney disease (CKD), impairs the viability of human bone marrow derived-mesenchymal stromal cells (BM-MSCs) post-transplantation. To address this, we demonstrated that combining BM-MSCs with the anti-fibrotic drug, serelaxin (RLX), enhanced BM-MSC-induced renoprotection in preclinical CKD models. Given the increased interest and manufacturing advantages to using stem cell-derived exosomes (EXO) as therapeutics, this study determined whether RLX could enhance the therapeutic efficacy of BM-MSC-EXO, and compared the renoprotective effects of RLX and BM-MSC-EXO versus RLX and BM-MSCs in mice with hypertensive CKD. Adult male C57BL/6 mice were uninephrectomised, received deoxycorticosterone acetate and given saline to drink (1K/DOCA/salt) for 21 days. Control mice were uninephrectomised and given normal drinking water for the same time-period. Subgroups of 1K/DOCA/salt-hypertensive mice were then treated with either RLX (0.5 mg/kg/day) or BM-MSC-EXO (25 μg/mouse; equivalent to 1-2 × 106 BM-MSCs/mouse) alone; combinations of RLX and BM-MSC-EXO or BM-MSCs (1 × 106/mouse); or the mineralocorticoid receptor antagonist, spironolactone (20 mg/kg/day), from days 14-21. 1K/DOCA/salt-hypertensive mice developed kidney tubular damage, inflammation and fibrosis, and impaired kidney function 21 days post-injury. Whilst RLX alone attenuated the 1K/DOCA/salt-induced fibrosis, BM-MSC-EXO alone only diminished measures of tissue inflammation post-treatment. Comparatively, the combined effects of RLX and BM-MSC-EXO or BM-MSCs demonstrated similar anti-fibrotic efficacy, but RLX and BM-MSCs offered broader renoprotection over RLX and/or BM-MSC-EXO, and comparable effects to spironolactone. Only RLX and BM-MSCs, but not RLX and/or BM-MSC-EXO, also attenuated the 1K/DOCA/salt-induced hypertension. Hence, although RLX improved the renoprotective effects of BM-MSC-EXO, combining RLX with BM-MSCs provided a better therapeutic option for hypertensive CKD.

Impact of allogeneic feline uterine-derived mesenchymal stromal cell intravenous treatment on renal function of nephrectomized cats with chronic kidney disease

Chronic kidney disease (CKD) is a common condition and leading cause of mortality in cats. Mesenchymal stromal cells (MSCs) may have a therapeutic effect on CKD. The aim of this pilot study was to determine efficacy of systemically-administered allogeneic uterine tissue-derived MSCs (UMSCs) in cats with CKD. Eighteen renal-compromised, unilaterally nephrectomized cats received two doses of 3 × 10⁷ allogeneic UMSCs given intravenously (IV) with a 2-week dose interval. The primary endpoint was renal function, with treatment success defined by a 20% increase in glomerular filtration rate (GFR; iohexol clearance) and/or a 20% decrease in plasma creatinine in 50% of the cats. Secondary endpoints included diet and water consumption, body weight, urine characteristics, and adverse events. Treatment was well tolerated and associated with a statistically meaningful increase in GFR on Days 13, 28, 57, 99, 121 and 182, compared with baseline (P < 0.0001 for Days 13 to 99 inclusive; P = 0.0029 and P = 0.0225 for Days 121 and 182, respectively). Greater than 50% of the cats demonstrated a 20% increase in GFR on all days except Day 150, at which point GFR measurements were consistently above baseline. Statistically meaningful increases in diet and water consumption were observed. Substantial improvements in GFR were observed throughout the six-month evaluation period (excluding Day 150) in more than 50% of cats, thereby meeting the primary endpoint. Therefore, this IV-administered, allogeneic cellular therapy may support both renal function and clinical status of cats with CKD.

Bone marrow-derived mesenchymal stem cells transplantation ameliorates renal injury through anti-fibrotic and anti-inflammatory effects in chronic experimental renovascular disease

Background

Progressive renal fibrosis is an underlying pathological process of chronic kidney disease (CKD) evolution. This study aimed to evaluate the roles of bone-marrow-derived mesenchymal stem cells (MSC) in the remodeling of fibrotic kidney parenchyma in the two kidneys-one clip (2K1C) CKD animal model.

Methods

Wistar rats were allocated into three groups: Sham, 2K1C, and 2K1C þ MSC. MSCs (106) were transplanted into the renal subcapsular region two weeks after clipping the left renal artery. Six weeks after clipping, left kidney samples were analyzed using histological and western blotting techniques. ANOVA tests were performed and differences between groups were considered statistically significant if p < 0.05.

Results

Clipped kidneys of 2K1C rats displayed renal fibrosis, with excessive collagen deposition, glomerulosclerosis and renal basement membrane disruption. Clipped kidneys of 2K1C þ MSC rats showed preserved Bowman's capsule and tubular basement membranes, medullary tubules morphological reconstitution and reduced collagen deposits. Expression levels of matrix metalloproteinase (MMP)-2 and MMP-9 were elevated, whereas tissue inhibitor of MMPs (TIMP)-1 and TIMP-2 levels were decreased in clipped kidneys of 2K1C rats. MSCs transplantation restored these expression levels. Moreover, MSCs suppressed macrophages and myofibroblasts accumulation, as well as TNF-a expression in clipped kidneys of 2K1C animals. MSCs transplantation significantly increased IL-10 expression.

Conclusions

Transplanted MSCs orchestrate anti-fibrotic and anti-inflammatory events, which reverse renal fibrosis and promote renal morphological restoration. This study supports the notion that only one MSCs delivery into the renal subcapsular region represents a possible therapeutic strategy against renal fibrosis for CKD treatment.

Combining mesenchymal stem cells with serelaxin provides enhanced renoprotection against 1K/DOCA/salt-induced hypertension

BACKGROUND AND PURPOSE

Fibrosis is a hallmark of chronic kidney disease (CKD) that significantly contributes to renal dysfunction, and impairs the efficacy of stem cell-based therapies. This study determined whether combining bone marrow-derived mesenchymal stem cells (BM-MSCs) with the renoprotective effects of recombinant human relaxin (serelaxin) could therapeutically reduce renal fibrosis in mice with one kidney/deoxycorticosterone acetate/salt (1K/DOCA/salt)-induced hypertension, compared with the effects of the ACE inhibitor, perindopril.

EXPERIMENTAL APPROACH

Adult male C57BL/6 mice were uni-nephrectomised and received deoxycorticosterone acetate and saline to drink (1K/DOCA/salt) for 21 days. Control mice were uni-nephrectomised but received water over the same time period. Sub-groups of 1K/DOCA/salt-injured mice (n = 5-8 per group) were treated with either serelaxin (0.5 mg·kg^-1 ·day^-1 ) or BM-MSCs (1 × 10⁶ per mouse) alone; both treatments combined (with 0.5 × 10⁶ or 1 × 10⁶ BM-MSCs per mouse); or perindopril (2 mg·kg^-1 ·day^-1 ) from days 14-21.

KEY RESULTS

1K/DOCA/salt-injured mice developed elevated BP and hypertension-induced renal damage, inflammation and fibrosis. BM-MSCs alone reduced the injury-induced fibrosis and attenuated BP to a similar extent as perindopril. Serelaxin alone modestly reduced renal fibrosis and effectively reduced tubular injury. Strikingly, the combined effects of BM-MSCs (at both doses) with serelaxin significantly inhibited renal fibrosis and proximal tubular epithelial injury while restoring renal architecture, to a greater extent than either therapy alone, and over the effects of perindopril.

CONCLUSION AND IMPLICATIONS

Combining BM-MSCs and serelaxin provided broader renoprotection over either therapy alone or perindopril and might represent a novel treatment for hypertensive CKD.

Effects of amnion derived mesenchymal stem cells on fibrosis in a 5/6 nephrectomy model in rats

Chronic kidney disease (CKD) is characterized by disruption of the glomerulus, tubule and vascular structures by renal fibrosis. Mesenchymal stem cells (MSC) ameliorate CKD. We investigated the effects of human amnion derived MSC (hAMSC) on fibrosis using expression of transforming growth factor beta (TGF-β), collagen type I (COL-1) and bone morphogenetic protein (BMP-7). We also investigated levels of urinary creatinine and nitrogen in CKD. We used a 5/6 nephrectomy (5/6 Nx) induced CKD model. We used 36 rats in six groups of six animals: sham group, 5/6 Nx group, 15 days after 5/6 Nx (5/6 Nx + 15) group, 30 days after 5/6 Nx (5/6 Nx + 30) group, transfer of hAMSC 15 days after 5/6 Nx (5/6 Nx + hAMSC + 15) group and transfer of hAMSC 30 days after 5/6 Nx (5/6 Nx + hAMSC + 30) group. We isolated 10⁶ hAMSC from the amnion and transplanted them via the rat tail vein into the 5/6 Nx + hAMSC + 15 and 5/6 Nx + hAMSC + 30 groups. We measured the expression of BMP-7, COL-1 and TGF-β using western blot and immunohistochemistry, and their gene expressions were analyzed by quantitative real time PCR. TGF-β and COL-1 protein, and gene expressions were increased in the 5/6 Nx +30 group compared to the 5/6 Nx + hAMSC + 30 group. Conversely, both protein and gene expression of BMP-7 was increased in 5/6 Nx + hAMSC + 30 group compared to the 5/6 Nx groups. Increased TGF-β together with decreased BMP-7 expression may cause fibrosis by epithelial-mesenchymal transition due to chronic renal injury. Increased COL-1 levels cause accumulation of extracellular matrix in CKD. Levels of urea, creatinine and nitrogen were increased significantly in 5/6 Nx + 15 and 5/6 Nx + 30 groups compared to the hAMSC groups. We found that hAMSC ameliorate CKD.

Adipose-Derived Mesenchymal Stem Cells Modulate Fibrosis and Inflammation in the Peritoneal Fibrosis Model Developed in Uremic Rats

Peritoneal fibrosis (PF) represents a long-term complication of peritoneal dialysis (PD), affecting the peritoneal membrane (PM) function. Adipose tissue-derived mesenchymal stem cells (ASC) display immunomodulatory effects and may represent a strategy to block PF. The aim of this study was to analyze the effect of ASC in an experimental PF model developed in uremic rats. To mimic the clinical situation of patients on long-term PD, a combo model, characterized by the combination of PF and chronic kidney disease (CKD), was developed in Wistar rats. Rats were fed with a 0.75% adenine-containing diet, for 30 days, to induce CKD with uremia. PF was induced with intraperitoneal injections of chlorhexidine gluconate (CG) from day 15 to 30. 1 × 10⁶ ASC were intravenously injected at days 15 and 21. Rats were divided into 5 groups: control, normal rats; CKD, rats receiving adenine diet; PF, rats receiving CG; CKD+PF, CKD rats with PF; CKD+PF+ASC, uremic rats with PF treated with ASC. PF was assessed by Masson trichrome staining. Inflammation- and fibrosis-associated factors were assessed by immunohistochemistry, multiplex analysis, and qPCR. When compared with the control and CKD groups, GC administration induced a striking increase in PM thickness and inflammation in the PF and CKD+PF groups. The development of PF was blocked by ASC treatment. Further, the upregulation of profibrotic factors (TGF-β, fibronectin, and collagen) and the increased myofibroblast expression observed in the CKD+PF group were significantly ameliorated by ASC. Beyond the antifibrotic effect, ASC showed an anti-inflammatory effect avoiding leucocyte infiltration and the overexpression of inflammatory cytokines (IL-1β, TNF-α, and IL-6) in the PM induced by GC. ASC were effective in preventing the development of PF in the experimental model of CKD+PF, probably due to their immunomodulatory properties. These results suggest that ASC may represent a potential strategy for treating long-term PD-associated fibrosis.

Prophylaxis against renal ischemia-reperfusion injury in canine model: Stem cell approach

Introduction

Stem cell therapy at the time of ischemia/reperfusion (I/R) injury has been hypothesized to attenuate the severity of acute kidney injury and to accelerate the regeneration process in lower animal models. Data in higher animal models is limited and discordant. We aimed to explore the reno-protective effects of stem cells on I/R related renal injury in a canine model.

Materials and Methods

Twenty-seven dogs that were treated with bone marrow-derived mesenchymal stem cells (BM-MSCs) were compared with another 27 dogs treated with adipose tissue-derived MSCs (AT-MSCs) following 90 min of warm ischemia to assess IR injury. Each group was divided into three subgroups (nine dogs each), according to the stem cell dose (5, 10, 15 × 10⁶ in 500 μl volume) injected directly into the renal cortex after reperfusion. All dogs were re-evaluated by renogram, histopathology, and pro-inflammatory markers at 2 weeks, 2, and 3 months.

Results

In Group I, there was a mean reduction of creatinine clearance by 78%, 64%, and 74% at the three used doses, respectively, at 2 weeks. At 3 months, these kidneys regained a mean of 84%, 92%, and 72%, respectively, of its basal function. In Group II, the reduction of clearance was much more modest with mean of 14%, 6%, and 24% respectively at 2 weeks with more intense recovery of renal function by mean of 90%, 100%, and 76%, respectively, at 3 months. Group I had significantly more tubular necrosis and delayed regeneration compared with the Group II. Expressions of pro-inflammatory markers were upregulated in both the groups with a higher and more sustained expression in Group I.

Conclusion

Stem cells protected against ischemic reperfusion injury in a canine model. AT-MSCs provided better protection than BM-MSCs.

Protective Effects of Human Nonrenal and Renal Stromal Cells and Their Conditioned Media in a Rat Model of Chronic Kidney Disease

Mesenchymal stromal cells (MSCs) are emerging as a novel therapeutic option for limiting chronic kidney disease progression. Conditioned medium (CM) containing bioactive compounds could convey similar benefits, avoiding the potential risks of cell therapy. This study compared the efficacy of nonrenal and renal cell-based therapy with the corresponding CM in rats with renal mass reduction (RMR). Infusions of human kidney stromal cells (kPSCs) and CM-kPSCs, but not umbilical cord (uc) MSCs or CM-ucMSCs, reduced proteinuria and preserved podocyte number and nephrin expression in RMR rats. Glomerular fibrosis, microvascular rarefaction, and apoptosis were reduced by all treatments, while the peritubular microvascular loss was reduced by kPSCs and CM-kPSCs treatment only. Importantly, kPSCs and CM-kPSCs reduced NG2-positive pericytes, and all therapies reduced α-smooth muscle actin expression, indicating reduced myofibroblast expansion. Treatment with kPSCs also significantly inhibited the accumulation of ED1-positive macrophages in the renal interstitium of RMR rats. These findings demonstrate that the CM of ucMSCs and kPSCs confers similar renoprotection as the cells. kPSCs and CM-kPSCs may be superior in attenuating chronic renal injury as a cell source.

Mesenchymal Stromal Cells Induce Podocyte Protection in the Puromycin Injury Model

Podocytes are specialized cells with a limited capacity for cell division that do not regenerate in response to injury and loss. Insults that compromise the integrity of podocytes promote proteinuria and progressive renal disease. The aim of this study was to evaluate the potential renoprotective and regenerative effects of mesenchymal stromal cells (mSC) in a severe form of the podocyte injury model induced by intraperitoneal administration of puromycin, aggravated by unilateral nephrectomy. Bone derived mSC were isolated and characterized according to flow cytometry analyses and to their capacity to differentiate into mesenchymal lineages. Wistar rats were divided into three groups: Control, PAN, and PAN+ mSC, consisting of PAN rats treated with 2 × 10⁵ mSC. PAN rats developed heavy proteinuria, hypertension, glomerulosclerosis and significant effacement of the foot process. After 60 days, PAN rats treated with mSC presented a significant amelioration of all these abnormalities. In addition, mSC treatment recovered WT1 expression, improved nephrin, podocin, synaptopodin, podocalyxin, and VEGF expression, and downregulated proinflammatory Th1 cytokines in the kidney with a shift towards regulatory Th2 cytokines. In conclusion, mSC administration induced protection of podocytes in this experimental PAN model, providing new perspectives for the treatment of renal diseases associated with podocyte damage.

Effects of Human Placental Amnion Derived Mesenchymal Stem Cells on Proliferation and Apoptosis Mechanisms in Chronic Kidney Disease in the Rat

Background and Objectives

The feature of chronic kidney failure (CKF) is loss of kidney functions due to erosion of healthy tissue and fibrosis. Recent studies showed that Mesenchymal stem cells (MSCs) differentiated into tubular epithelial cells thus renal function and structures renewed. Furthermore, MSCs protect renal function in CKF. Therefore, we aimed to investigate whether human amnion-derived mesenchymal stem cells (hAMSCs) can repair fibrosis and determine the effects on proliferation and apoptosis mechanisms in chronic kidney failure.

Methods and Results

In this study, rat model of CKF was constituted by applying Aristolochic acid (AA). hAMSCs were isolated from term placenta amnion membrane and transplanted into tail vein of rats. At the end of 30 days and 60 days of recovery period, we examined expressions of PCNA, p57 and Parp-1 by western blotting. Immunoreactivity of PCNA, Ki67, IL-6 and Collagen type I were detected by immunohistochemistry. Besides, apoptosis was detected by TUNEL. Serum creatinine and urea were measured. Expressions of PCNA and Ki67 increased in hAMSC groups compared with AA group. Furthermore, expressions of PARP-1 apoptosis marker and p57 cell cycle inhibitory protein increased in AA group significantly according to control, hAMSC groups and sham groups. IL-6 proinflammatory cytokine increased in AA group significantly according to control, hAMSCs groups and sham groups. Expressions of Collagen type I protein reduced in hAMSCs groups compared to AA group. After hAMSC treatment, serum creatinine and urea levels significantly decreased compared to AA group. After injection of hAMSC to rats, Masson’s Trichrome and Sirius Red staining showed fibrosis reduction in kidney.

Conclusions

According to our results hAMSCs can be ameliorate renal failure.

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.

Melatonin protects chronic kidney disease mesenchymal stem cells against senescence via PrPC -dependent enhancement of the mitochondrial function

Although mesenchymal stem cell (MSC)-based therapy is a treatment strategy for ischemic diseases associated with chronic kidney disease (CKD), MSCs of CKD patients undergo accelerated senescence, with decreased viability and proliferation upon uremic toxin exposure, inhibiting their utility as a potent stem cell source for transplantation therapy. We investigated the effects of melatonin administration in protecting against cell senescence and decreased viability induced by pathophysiological conditions near the engraftment site. MSCs harvested from CKD mouse models were treated with H₂ O₂ to induce oxidative stress. CKD-derived MSCs exhibited greater oxidative stress-induced senescence than normal-mMSCs, while melatonin protected CKD-mMSCs from H₂ O₂ and associated excessive senescence. The latter was mediated by PrP^C -dependent mitochondrial functional enhancement; melatonin upregulated PrP^C , which bound PINK1, thus promoting mitochondrial dynamics and metabolism. In vivo, melatonin-treated CKD-mMSCs survived longer, with increased secretion of angiogenic cytokines in ischemic disease engraftment sites. CKD-mMSCs are more susceptible to H₂ O₂ -induced senescence than normal-mMSCs, and melatonin administration protects CKD-mMSCs from excessive senescence by upregulating PrP^C and enhancing mitochondrial function. Melatonin showed favorable therapeutic effects by successfully protecting CKD-mMSCs from related ischemic conditions, thereby enhancing angiogenesis and survival. These results elucidate the mechanism underlying senescence inhibition by melatonin in stem cell-based therapies using mouse-derived CKD-mMSCs.

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.

Bone marrow mesenchymal stem cells attenuate the progression of focal segmental glomerulosclerosis in rat models

Background

Focal segmental glomerulosclerosis (FSGS) is the most common glomerular etiology of end-stage kidney disease (ESKD). Increasing evidence has indicated the reparative potential of mesenchymal stem cells (MSCs) in damaged diseased kidneys. However, the effect of bone marrow mesenchymal stem cells (BMSCs) on the FSGS progression remains unclear. This study aimed to investigate the protective effects of BMSCs on FSGS progression.

Methods

A rat model of FSGS was generated via unilateral nephrectomy plus adriamycin injection. Rat BMSCs were isolated and characterized on the basis of their differentiative potential towards adipocytes and osteoblasts and via flow cytometry analysis. Thereafter, rat BMSCs were transplanted into FSGS recipients through the caudal vein. After 8 weeks, 24-h proteinuria, serum creatinine, and urea nitrogen levels were determined. Renal morphology was assessed using a light and transmission electron microscope. MMP9 and TIMP-1 positive cells were detected via immunohistochemical analysis. Expression levels of proinflammatory cytokines IL-6 and TNF-α were examined via RT-PCR.

Results

The isolated adherent cells from the bone marrow of rats were phenotypically and functionally equivalent to typical MSCs. Clinical examination revealed that BMSC transplantation reduced the 24-h urinary protein excretion, and serum creatinine and urea nitrogen levels. Renal morphology was ameliorated in BMSCs-transplanted rats. Mechanistically, BMSC transplantation significantly downregulated TIMP-1 and upregulated MMP9, thereby increasing the renal MMP9/TIMP-1 ratio. Moreover, BMSC transplantation also downregulated IL-6 and TNF-α.

Conclusions

BMSC transplantation can attenuate FSGS progression in a rat model of FSGS, thereby providing a theoretical foundation for the application of autologous BMSCs in clinical FSGS therapy.

Kidney-derived c-kit+ progenitor/stem cells contribute to podocyte recovery in a model of acute proteinuria

Kidney-derived c-kit⁺ cells exhibit progenitor/stem cell properties and can regenerate epithelial tubular cells following ischemia-reperfusion injury in rats. We therefore investigated whether c-kit⁺ progenitor/stem cells contribute to podocyte repair in a rat model of acute proteinuria induced by puromycin aminonucleoside (PAN), the experimental prototype of human minimal change disease and early stages of focal and segmental glomerulosclerosis. We found that c-kit⁺ progenitor/stem cells accelerated kidney recovery by improving foot process effacement (foot process width was lower in c-kit group vs saline treated animals, P = 0.03). In particular, these cells engrafted in small quantity into tubules, vessels, and glomeruli, where they occasionally differentiated into podocyte-like cells. This effect was related to an up regulation of α-Actinin-4 and mTORC2-Rictor pathway. Activation of autophagy by c-kit⁺ progenitor/stem cells also contributed to kidney regeneration and intracellular homeostasis (autophagosomes and autophagolysosomes number and LC3A/B-I and LC3A/B-II expression were higher in the c-kit group vs saline treated animals, P = 0.0031 and P = 0.0009, respectively). Taken together, our findings suggest that kidney-derived c-kit⁺ progenitor/stem cells exert reparative effects on glomerular disease processes through paracrine effects, to a lesser extent differentiation into podocyte-like cells and contribution to maintenance of podocyte cytoskeleton after injury. These findings have clinical implications for cell therapy of glomerular pathobiology.

Mesenchymal stem cell therapy in cats: Current knowledge and future potential

Practical relevance: Stem cell therapy is an innovative field of scientific investigation with tremendous potential for clinical application in veterinary medicine. Based on the known desirable immunomodulatory properties of mesenchymal stem cells, this therapy holds promise for the treatment of a variety of inflammatory diseases in cats.

AIMS

This review details our current understanding of feline stem cell biology and proposed mechanism of action. Studies performed in feline clinical trials for diseases including gingivostomatitis, chronic enteropathy, asthma and kidney disease are summarized, with the goal of providing an overview of the current status of this treatment modality and its potential for the future.

Mesenchymal Stem Cells in Kidney Repair

Every year 13.3 million people suffer acute kidney injury (AKI), which is associated with a high risk of death or development of long-term chronic kidney disease (CKD) in a substantial percentage of patients besides other organ dysfunctions. To date, the mortality rate per year for AKI exceeds 50 % at least in patients requiring early renal replacement therapy and is higher than the mortality for breast and prostate cancer, heart failure and diabetes combined.Until now, no effective treatments able to accelerate renal recovery and improve survival post AKI have been developed. In search of innovative and effective strategies to foster the limited regeneration capacity of the kidney, several studies have evaluated the ability of mesenchymal stem cells (MSCs) of different origin as an attractive therapeutic tool. The results obtained in several models of AKI and CKD document that MSCs have therapeutic potential in repair of renal injury, preserving renal function and structure thus prolonging animal survival through differentiation-independent pathways. In this chapter, we have summarized the mechanisms underlying the regenerative processes triggered by MSC treatment, essentially due to their paracrine activity. The capacity of MSC to migrate to the site of injury and to secrete a pool of growth factors and cytokines with anti-inflammatory, mitogenic, and immunomodulatory effects is described. New modalities of cell-to-cell communication via the release of microvesicles and exosomes by MSCs to injured renal cells will also be discussed. The translation of basic experimental data on MSC biology into effective care is still limited to preliminary phase I clinical trials and further studies are needed to definitively assess the efficacy of MSC-based therapy in humans.

Renal disease pathophysiology and treatment: contributions from the rat

The rat has classically been the species of choice for pharmacological studies and disease modeling, providing a source of high-quality physiological data on cardiovascular and renal pathophysiology over many decades. Recent developments in genome engineering now allow us to capitalize on the wealth of knowledge acquired over the last century. Here, we review rat models of hypertension, diabetic nephropathy, and acute and chronic kidney disease. These models have made important contributions to our understanding of renal diseases and have revealed key genes, such as Ace and P2rx7, involved in renal pathogenic processes. By targeting these genes of interest, researchers are gaining a better understanding of the etiology of renal pathologies, with the promised potential of slowing disease progression or even reversing the damage caused. Some, but not all, of these target genes have proved to be of clinical relevance. However, it is now possible to generate more sophisticated and appropriate disease models in the rat, which can recapitulate key aspects of human renal pathology. These advances will ultimately be used to identify new treatments and therapeutic targets of much greater clinical relevance.

Summary: This Review highlights the key role that the rat continues to play in improving our understanding of the etiologies of renal pathologies, and how these insights have opened up new therapeutic avenues.

Micro-vesicles derived from human Wharton's Jelly mesenchymal stromal cells mitigate renal ischemia-reperfusion injury in rats after cardiac death renal transplantation

The purpose of the present study was to investigate the possible therapeutic effects of the human Wharton-Jelly mesenchymal stromal cells derived micro-vesicles (hWJMSCs-MVs) on renal ischemia-reperfusion injury (IRI) after cardiac death (CD) renal transplantation in rats. MVs were injected intravenously in rats immediately after renal transplantation. The animals were sacrificed at 24 h, 48 h, 1 and 2 weeks post-transplantation. ELISA was used to determine the von Willebrand Factor (vWF), tumor necrosis factor (TNF)-α, and interleukin (IL)-10 levels in the serum. Tubular cell proliferation and apoptosis were identified by Ki67 immunostaining and TUNEL assay. Renal fibrosis was assessed by Masson's tri-chrome straining and alpha-smooth muscle actin (α-SMA) staining. The infiltration of inflammatory cells was detected by CD68⁺ staining. The transforming growth factor (TGF)-β, hepatocyte growth factor (HGF), and α-SMA expression in the kidney was measured by Western blot. After renal transplantation, the rats treated with hWJMSCs-MVs improved survival rate and renal function. Moreover, MVs mitigated renal cell apoptosis, enhanced proliferation, and alleviated inflammation at the first 48 h. In the late period, abrogation of renal fibrosis was observed in the MVs group. MVs also could decrease the number of CD68⁺ macrophages in the kidney. Furthermore, MVs decreased the protein expression levels of α-SMA and TGF-β1 and increased the protein expression level of HGF at any point (24 h, 48 h, 1 or 2 weeks). The administration of MVs immediately after renal transplantation could ameliorate IRI in both the acute and chronic stage.

Induced Pluripotent Stem Cells Reduce Progression of Experimental Chronic Kidney Disease but Develop Wilms' Tumors

The therapeutic effect of induced pluripotent stem cells (iPSs) on the progression of chronic kidney disease (CKD) has not yet been demonstrated. In this study, we sought to assess whether treatment with iPSs retards progression of CKD when compared with bone marrow mesenchymal stem cells (BMSCs). Untreated 5/6 nephrectomized rats were compared with CKD animals receiving BMSCs or iPSs. Renal function, histology, immunohistochemistry, and gene expression were studied. Implanted iPSs were tracked by the SRY gene expression analysis. Both treatments minimized elevation in serum creatinine, significantly improved clearance, and slowed down progression of disease. The proteinuria was reduced only in the iPS group. Both treatments reduced glomerulosclerosis, iPSs decreased macrophage infiltration, and TGF-β was reduced in kidneys from the BMSC group. Both types of treatments increased VEGF gene expression, TGF-β was upregulated only in the iPS group, and IL-10 had low expression in both groups. The SRY gene was found in 5/8 rats treated with iPSs. These 5 animals presented tumors with histology and cells highly staining positive for PCNA and Wilms' tumor protein antibody characteristics of Wilms' tumor. These results suggest that iPSs may be efficient to retard progression of CKD but carry the risk of Wilms' tumor development.

Umbilical cord mesenchymal stem cells derived extracellular vesicles can safely ameliorate the progression of chronic kidney diseases

Background

Bio-products from stem/progenitor cells, such as extracellular vesicles, are likely a new promising approach for reprogramming resident cells in both acute and chronic kidney disease. Forty CKD patients stage III and IV (eGFR 15–60 mg/ml) have been divided into two groups; twenty patients as treatment group “A” and twenty patients as a matching placebo group “B”. Two doses of MSC-derived extracellular vesicles had been administered to patients of group “A”. Blood urea, serum creatinine, urinary albumin creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) have been used to assess kidney functions and TNF-α, TGF-β1 and IL-10 have been used to assess the amelioration of the inflammatory immune activity.

Results

Participants in group A exhibited significant improvement of eGFR, serum creatinine level, blood urea and UACR. Patients of the treatment group “A” also exhibited significant increase in plasma levels of TGF-β1, and IL-10 and significant decrease in plasma levels of TNF-α. Participants of the control group B did not show significant improvement in any of the previously mentioned parameters at any time point of the study period.

Conclusion

Administration of cell-free cord-blood mesenchymal stem cells derived extracellular vesicles (CF-CB-MSCs-EVs) is safe and can ameliorate the inflammatory immune reaction and improve the overall kidney function in grade III-IV CKD patients.

Influence of erythropoietin on microvesicles derived from mesenchymal stem cells protecting renal function of chronic kidney disease

Introduction

Mesenchymal stem cells (MSCs) play a central role in the remediation of cell and tissue damage. Erythropoietin (EPO) may enhance the beneficial influence of MSCs during recovery from tissue and organ injuries. Microvesicles (MVs) released from MSCs contribute to the restoration of kidney damage. We studied the influence of EPO on MVs derived from MSCs, and the protective effects of these factors in subjects with chronic kidney disease (CKD).

Methods

The MVs derived from untreated MSCs (MSC-MVs) or from MSCs incubated in different concentrations of EPO (1, 10, 100, and 500 IU/ml EPO-MVs) were used to treat renal injury of unilateral ureteral obstruction (UUO) in vivo, and transforming growth factor-β1 (TGF-β1)-induced fibrosis in a human renal proximal tubular epithelial (HK2) cell line in vitro. Western blot and reverse transcription polymerase chain reaction (RT-PCR) analyses were used to evaluate the expression of epithelial and mesenchymal markers in the renal tissue and HK2 cells. Flow cytometry was used to assess apoptosis within the HK2 cells, and microRNA (miRNA) microarray assays were used to determine the expression profiles of miRNA in the MSC-MVs and EPO-MVs.

Results

Compared to MSC-MVs (untreated), there was a significant increase in the number of EPO-MVs derived from MSCs treated with 1–100 IU/ml EPO, and these EPO-MVs had a greater benefit in UUO mice on days 7 and 14. Moreover, the EPO-MVs had a better restorative effect following TGF-β1-induced fibrosis in HK2 cells at 24 h and 48 h. The flow cytometry results revealed that both types of MVs, especially EPO-MVs, play an important anti-apoptotic role in HK2 cells treated with TGF-β1. The miRNA profiles of the MVs revealed that EPO-MVs changed 212 miRNAs (fold-change ≥ 1.5), including miR-299, miR-499, miR-302, and miRNA-200, and that 70.28 % of these changes involved upregulation. The changed miRNA in EPO-MVs may have contributed to their enhanced protective effects following renal injury compared to MSC-MVs.

Conclusions

There was a dose-dependent increase in the level of EPO-MVs within the range of 1–100 IU/ml EPO. Although both MSC-MVs and EPO-MVs protect the kidney from fibrosis-related damage, there is a superior effect of EPO-MVs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0095-0) contains supplementary material, which is available to authorized users.

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 × 106 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.

Bone Marrow-Derived Mesenchymal Stem Cells and Their Conditioned Medium Attenuate Fibrosis in an Irreversible Model of Unilateral Ureteral Obstruction

The therapeutic potential of mesenchymal stem cells (MSCs) and their conditioned medium (MSC-CM) has been extensively studied. MSCs can repair tissue, reduce local inflammation, and modulate the immune response. Persistent renal tubular interstitial inflammation results in fibrosis and leads to chronic kidney disease (CKD). Unilateral ureteral obstruction (UUO) is a very well-accepted renal fibrosis model. In this study, we evaluated factors influenced by the administration of MSCs or MSC-CM in the UUO model. MSCs extracted from rat bone marrow were cultivated in vitro and characterized by flow cytometry and cellular differentiation. Eight groups of female rats were used in experiments (n = 7, each), including Sham, UUO, UUO + MSC (obstruction + MSC), and UUO + CM (obstruction + MSC-CM) for 7 days of obstruction and Sham, UUO, UUO + MSC, and UUO + CM for 14 days of obstruction. The MSCs or MSC-CM was administered via the abdominal vena cava after total ligation of the left ureter. After 7 or 14 days, rats were euthanized, and serum and obstructed kidney samples were collected. MSCs or MSC-CM decreased the expression of molecules, such as Col1a1, α-SMA, and TNF-α. We also observed reductions in the levels of caspase 3, α-SMA, and PCNA in treated animals by immunohistochemistry. Our results suggest that the intravenous administration of MSCs or MSC-CM improves fibrosis progression and factors involved in apoptosis, inflammation, cell proliferation, and epithelial-mesenchymal transition in Wistar rats subjected to UUO, indicating a potential tool for preventing CKD.

Cell-based therapies for experimental chronic kidney disease: a systematic review and meta-analysis

Cell-based therapy is a promising strategy for treating chronic kidney disease (CKD) and is currently the focus of preclinical studies. We performed a systematic review and meta-analysis to evaluate the efficacy of cell-based therapy in preclinical (animal) studies of CKD, and determined factors affecting cell-based therapy efficacy in order to guide future clinical trials. In total, 71 articles met the inclusion criteria. Standardised mean differences (SMD) and 95% confidence intervals (CI) were calculated for outcome parameters including plasma urea, plasma creatinine, urinary protein, blood pressure, glomerular filtration rate, glomerulosclerosis and interstitial fibrosis. Sub-analysis for each outcome measure was performed for model-related factors (species, gender, model and timing of therapy) and cell-related factors (cell type, condition and origin, administration route and regime of therapy). Overall, meta-analysis showed that cell-based therapy reduced the development and progression of CKD. This was most prominent for urinary protein (SMD, 1.34; 95% CI, 1.00–1.68) and urea (1.09; 0.66–1.51), both P<0.001. Changes in plasma urea were associated with changes in both glomerulosclerosis and interstitial fibrosis. Sub-analysis showed that cell type (bone-marrow-derived progenitors and mesenchymal stromal cells being most effective) and administration route (intravenous or renal artery injection) were significant predictors of therapeutic efficacy. The timing of therapy in relation to clinical manifestation of disease, and cell origin and dose, were not associated with efficacy. Our meta-analysis confirms that cell-based therapies improve impaired renal function and morphology in preclinical models of CKD. Our analyses can be used to optimise experimental interventions and thus support both improved preclinical research and development of cell-based therapeutic interventions in a clinical setting.

Recent advances in renal interstitial fibrosis and tubular atrophy after kidney transplantation

Although kidney transplantation has been an important means for the treatment of patients with end stage of renal disease, the long-term survival rate of the renal allograft remains a challenge. The cause of late renal allograft loss, once known as chronic allograft nephropathy, has been renamed “interstitial fibrosis and tubular atrophy” (IF/TA) to reflect the histologic pattern seen on biopsy. The mechanisms leading to IF/TA in the transplanted kidney include inflammation, activation of renal fibroblasts, and deposition of extracellular matrix proteins. Identifying the mediators and factors that trigger IF/TA may be useful in early diagnosis and development of novel therapeutic strategies for improving long-term renal allograft survival and patient outcomes. In this review, we highlight the recent advances in our understanding of IF/TA from three aspects: pathogenesis, diagnosis, and treatment.

Mesenchymal stem cell treatment for chronic renal failure

Chronic renal failure is an important clinical problem with significant socioeconomic impact worldwide. Despite advances in renal replacement therapies and organ transplantation, poor quality of life for dialysis patients and long transplant waiting lists remain major concerns for nephrologists treating this condition. There is therefore a pressing need for novel therapies to promote renal cellular repair and tissue remodeling. Over the past decade, advances in the field of regenerative medicine allowed development of cell therapies suitable for kidney repair. Mesenchymal stem cells (MSCs) are undifferentiated cells that possess immunomodulatory and tissue trophic properties and the ability to differentiate into multiple cell types. Studies in animal models of chronic renal failure have uncovered a unique potential of these cells for improving function and regenerating the damaged kidney. Nevertheless, several limitations pertaining to inadequate engraftment, difficulty to monitor, and untoward effects of MSCs remain to be addressed. Adverse effects observed following intravascular administration of MSCs include immune rejection, adipogenic differentiation, malignant transformation, and prothrombotic events. Nonetheless, most studies indicate a remarkable capability of MSCs to achieve kidney repair. This review summarizes the regenerative potential of MSCs to provide functional recovery from renal failure, focusing on their application and the current challenges facing clinical translation.

Mesenchymal stem cells from rats with chronic kidney disease exhibit premature senescence and loss of regenerative potential

Mesenchymal stem cell (MSC) transplantation has the potential for organ repair. Nevertheless, some factors might lessen the regenerative potential of MSCs, e.g. donor age or systemic disease. It is thus important to carefully assess the patient's suitability for autologous MSC transplantation. Here we investigated the effects of chronic kidney disease (CKD) on MSC function. We isolated bone marrow MSCs from remnant kidney rats (RK) with CKD (CKD-RK-MSC) and found signs of premature senescence: spontaneous adipogenesis, reduced proliferation capacity, active senescence-associated-β-galactosidase, accumulation of actin and a modulated secretion profile. The functionality of CKD-RK-MSCs in vivo was tested in rats with acute anti-Thy1.1-nephritis, where healthy MSCs have been shown to be beneficial. Rats received healthy MSCs, CKD-RK-MSC or medium by injection into the left renal artery. Kidneys receiving healthy MSCs exhibited accelerated healing of glomerular lesions, whereas CKD-RK-MSC or medium exerted no benefit. The negative influence of advanced CKD/uremia on MSCs was confirmed in a second model of CKD, adenine nephropathy (AD). MSCs from rats with adenine nephropathy (CKD-AD-MSC) also exhibited cellular modifications and functional deficits in vivo. We conclude that CKD leads to a sustained loss of in vitro and in vivo functionality in MSCs, possibly due to premature cellular senescence. Considering autologous MSC therapy in human renal disease, studies identifying uremia-associated mechanisms that account for altered MSC function are urgently needed.

Human umbilical mesenchymal stem cells attenuate the progression of focal segmental glomerulosclerosis

Previous studies have suggested the potential of mesenchymal stem cells (MSCs) to repair damaged kidney diseases. However, the effect of human umbilical cord MSCs (HuMSCs) on the progression of focal segmental glomerulosclerosis (FSGS) remains poorly understood. Adriamycin-induced nephropathy is a rodent model of chronic kidney disease that has been studied extensively and has enabled a greater understanding of the processes underlying the progression of FSGS. This study aimed to investigate the role of HuMSCs on the progression of kidney disease using a model of adriamycin-induced nephropathy. Human MSCs were labeled with 5-bromo-2'-deoxyuridine to track their localization to the kidneys after infusion. Clinical parameters and histology suggested amelioration of FSGS in MSC-treated animals at 12 weeks, especially in those that received repeated doses. These results were associated with reduced serum interleukin (IL)-6 and tumor necrosis factor-α, transforming growth factor-β levels, connective tissue growth factor messenger RNA expression and upregulated serum IL-10 levels. In short, this experiment found that HuMSCs improved kidney fibrosis and modulated the inflammatory response, suggesting that xenogenic transplantation of HuMSCs is a novel approach for improving the progression of FSGS and may be a promising therapeutic intervention in the future.

Concise review: stem/progenitor cells for renal tissue repair: current knowledge and perspectives

The kidney is a specialized low-regenerative organ with several different types of cellular lineages; however, the identity of renal stem/progenitor cells with nephrogenic potential and their preferred niche(s) are largely unknown and debated. Most of the therapeutic approaches to kidney regeneration are based on administration of cells proven to enhance intrinsic reparative capabilities of the kidney. Endogenous or exogenous cells of different sources were tested in rodent models of ischemia-reperfusion, acute kidney injury, or chronic disease. The translation to clinics is at the moment focused on the role of mesenchymal stem cells. In addition, bioproducts from stem/progenitor cells, such as extracellular vesicles, are likely a new promising approach for reprogramming resident cells. This concise review reports the current knowledge about resident or exogenous stem/progenitor populations and their derived bioproducts demonstrating therapeutic effects in kidney regeneration upon injury. In addition, possible approaches to nephrogenesis and organ generation using organoids, decellularized kidneys, and blastocyst complementation are surveyed.

Healthy bone marrow cells reduce progression of kidney failure better than CKD bone marrow cells in rats with established chronic kidney disease

Chronic kidney disease (CKD) is a major health care problem. New interventions to slow or prevent disease progression are urgently needed. We studied functional and structural effects of infusion of healthy and CKD bone marrow cells (BMCs) in a rat model of established CKD. CKD was induced by 5/6 nephrectomy (SNX) in Lewis rats, and disease progression was accelerated with L-NNA and 6% NaCl diet. Six weeks after SNX, CKD rats received healthy eGFP(+) BMCs, CKD eGFP(+) BMCs, or vehicle by single renal artery injection. Healthy BMCs were functionally effective 6 weeks after administration: glomerular filtration rate (GFR; inulin clearance) (0.48±0.16 vs. 0.26±0.14 ml/min/100 g) and effective renal plasma flow (RPF; PAH clearance) (1.6±0.40 vs. 1.0±0.62 ml/min/100 g) were higher in healthy BMC- versus vehicle-treated rats (both p < 0.05). Systolic blood pressure (SBP) and proteinuria were lower 5 weeks after treatment with healthy BMCs versus vehicle (SBP, 151±13 vs. 186±25 mmHg; proteinuria, 33±20 vs. 59±39 mg/day, both p < 0.05). Glomerular capillary density was increased, and less sclerosis was detected after healthy BMCs (both p < 0.05). Tubulointerstitial inflammation was also decreased after healthy BMCs. eGFP(+) cells were present in the glomeruli and peritubular capillaries of the remnant kidney in all BMC-treated rats. CKD BMCs also reduced SBP, proteinuria, glomerulosclerosis, and tubular atrophy versus vehicle in CKD rats. However, CKD BMC therapy was not functionally effective versus vehicle [GFR: 0.28±0.09 vs. 0.26±0.16 ml/min/100 g (NS), RPF: 1.15±0.36 vs. 0.78±0.44 ml/min/100 g (NS)], and failed to decrease tubulointerstitial inflammation and fibrosis. Single intrarenal injection of healthy BMCs in rats with established CKD slowed progression of the disease, associated with increased glomerular capillary density and less sclerosis, whereas injection of CKD BMCs was less effective.

Human mesenchymal stem cells derived from adipose tissue reduce functional and tissue damage in a rat model of chronic renal failure

Therapeutic approaches for CKD (chronic kidney disease) have been able to reduce proteinuria, but not diminish the disease progression. We have demonstrated beneficial effects by injection of BM (bone marrow)-derived MSCs (mesenchymal stem cells) from healthy donors in a rat model with CKD. However, it has recently been reported that BM-MSCs derived from uraemic patients failed to confer functional protection in a similar model. This suggests that autologous BM-MSCs are not suitable for the treatment of CKD. In the present study, we have explored the potential of MSCs derived from adipose tissue (AD-MSCs) as an alternative source of MSCs for the treatment of CKD. We have isolated AD-MSCs and evaluated their effect on the progression of CKD. Adult male SD (Sprague-Dawley) rats subjected to 5/6 NPX (nephrectomy) received a single intravenous infusion of 0.5×10(6) AD-MSCs or MSC culture medium alone. The therapeutic effect was evaluated by plasma creatinine measurement, structural analysis and angiogenic/epitheliogenic protein expression. AD-MSCs were detected in kidney tissues from NPX animals. This group had a significant reduction in plasma creatinine levels and a lower expression of damage markers ED-1 and α-SMA (α-smooth muscle actin) (P<0.05). In addition, treated rats exhibited a higher level of epitheliogenic [Pax-2 and BMP-7 (bone morphogenetic protein 7)] and angiogenic [VEGF (vascular endothelial growth factor)] proteins. The expression of these biomarkers of regeneration was significantly related to the improvement in renal function. Although many aspects of the cell therapy for CKD remain to be investigated, we provide evidence that AD-MSCs, a less invasive and highly available source of MSCs, exert an important therapeutic effect in this pathology.

Cell projections and extracellular matrix cross the interstitial interface within the renal stem/progenitor cell niche: accidental, structural or functional cues?

BACKGROUND

During nephron induction, morphogenetic molecules are reciprocally exchanged between epithelial and mesenchymal stem/progenitor cells within the renal stem/progenitor cell niche. That these molecules remain concentrated, it is assumed that both cell populations stand in close contact to each other. However, recently published data illustrate that epithelial and mesenchymal cells are separated by an astonishingly wide interstitial interface.

METHODS

To gain deeper morphological insights into the spatial distribution of mesenchymal and epithelial stem/progenitor cells, the embryonic zone of neonatal rabbit kidney was fixed either with glutaraldehyde (GA) or in a combination with cupromeronic blue, ruthenium red or tannic acid. Transmission electron microscopy was then performed on exactly orientated sections.

RESULTS

Conventional fixation with GA illustrates that epithelial and mesenchymal stem/progenitor cells are separated by a bright but inconspicuously looking interstitial interface. In contrast, fixation of specimens in GA containing cupromeronic blue, ruthenium red or tannic acid elucidates that part of the interstitial interface exhibits a special extracellular matrix extending like woven strands between mesenchymal and epithelial stem/progenitor cells. In parallel, filigree projections from mesenchymal stem/progenitor cells cross the interstitial interface to penetrate the basal lamina of epithelial cells. Fusion of the plasma membranes cannot be observed. Instead, touching mesenchymal cell projections form a cone at the contact site with tunneling nanotubes.

CONCLUSIONS

The results demonstrate that the contact between mesenchymal and epithelial stem/progenitor cells does not form accidentally but physiologically and appears to belong to a suspected system involved in the exchange of morphogenetic information.

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.

The impact of stem cells on electron fluxes, proton translocation, and ATP synthesis in kidney mitochondria after ischemia/reperfusion

Tissue damage by ischemia/reperfusion (I/R) results from a temporary cessation of blood flow followed by the restoration of circulation. The injury depresses mitochondrial respiration, increases the production of reactive oxygen species (ROS), decreases the mitochondrial transmembrane potential, and stimulates invasion by inflammatory cells. The primary objective of this work was to address the potential use of bone marrow stem cells (BMSCs) to preserve and restore mitochondrial function in the kidney after I/R. Mitochondria from renal proximal tubule cells were isolated by differential centrifugation from rat kidneys subjected to I/R (clamping of renal arteries followed by release of circulation after 30 min), without or with subcapsular administration of BMSCs. Respiration starting from mitochondrial complex II was strongly affected following I/R. However, when BMSCs were injected before ischemia or together with reperfusion, normal electron fluxes, electrochemical gradient for protons, and ATP synthesis were almost completely preserved, and mitochondrial ROS formation occurred at a low rate. In homogenates from cultured renal cells transiently treated with antimycin A, the coculture with BMSCs induced a remarkable increase in protein S-nitrosylation that was similar to that found in mitochondria isolated from I/R rats, evidence that BMSCs protected against both superoxide anion and peroxynitrite. Labeled BMSCs migrated to damaged tubules, suggesting that the injury functions as a signal to attract and host the injected BMSCs. Structural correlates of BMSC injection in kidney tissue included stimulus of tubule cell proliferation, inhibition of apoptosis, and decreased inflammatory response. Histopathological analysis demonstrated a score of complete preservation of tubular structures by BMSCs, associated with normal plasma creatinine and urinary osmolality. These key findings shed light on the mechanisms that explain, at the mitochondrial level, how stem cells prevent damage by I/R. The action of BMSCs on mitochondrial functions raises the possibility that autologous BMSCs may help prevent I/R injuries associated with transplantation and acute renal diseases.

Mesenchymal stem cell therapy promotes renal repair by limiting glomerular podocyte and progenitor cell dysfunction in adriamycin-induced nephropathy

We previously reported that in a model of spontaneously progressive glomerular injury with early podocyte loss, abnormal migration, and proliferation of glomerular parietal epithelial progenitor cells contributed to the formation of synechiae and crescentic lesions. Here we first investigated whether a similar sequence of events could be extended to rats with adriamycin (ADR)-induced nephropathy. As a second aim, the regenerative potential of therapy with bone marrow-derived mesenchymal stem cells (MSCs) on glomerular resident cells was evaluated. In ADR-treated rats, decrease of WT1(+) podocyte number due to apoptosis was associated with reduced glomerular expression of nephrin and CD2AP. As a consequence of podocyte injury, glomerular adhesions of the capillary tuft to the Bowman's capsule were observed, followed by crescent-like lesions and glomerulosclerosis. Cellular components of synechiae were either NCAM(+) parietal progenitor cells or nestin(+) podocytes. In ADR rats, repeated injections of MSCs limited podocyte loss and apoptosis and partially preserved nephrin and CD2AP. MSCs attenuated the formation of glomerular podocyte-parietal epithelial cell bridges and normalized the distribution of NCAM(+) progenitor cells along the Bowman's capsule, thereby reducing glomerulosclerosis. Finding that MSCs increased glomerular VEGF expression and limited microvascular rarefaction may explain the prosurvival effect by stem cell therapy. MSCs also displayed anti-inflammatory activity. Coculture of MSCs with ADR-damaged podocytes showed a functional role of stem cell-derived VEGF on prosurvival pathways. These data suggest that MSCs by virtue of their tropism for damaged kidney and ability to provide a local prosurvival environment may represent a useful strategy to preserve podocyte viability and reduce glomerular inflammation and sclerosis.

A population of selected renal cells augments renal function and extends survival in the ZSF1 model of progressive diabetic nephropathy

New treatment paradigms that slow or reverse progression of chronic kidney disease (CKD) are needed to relieve significant patient and healthcare burdens. We have shown that a population of selected renal cells (SRCs) stabilized disease progression in a mass reduction model of CKD. Here, we further define the cellular composition of SRCs and apply this novel therapeutic approach to the ZSF1 rat, a model of severe progressive nephropathy secondary to diabetes, obesity, dyslipidemia, and hypertension. Injection of syngeneic SRCs into the ZSF1 renal cortex elicited a regenerative response that significantly improved survival and stabilized disease progression to renal structure and function beyond 1 year posttreatment. Functional improvements included normalization of multiple nephron structures and functions including glomerular filtration, tubular protein handling, electrolyte balance, and the ability to concentrate urine. Improvements to blood pressure, including reduced levels of circulating renin, were also observed. These functional improvements following SRC treatment were accompanied by significant reductions in glomerular sclerosis, tubular degeneration, and interstitial inflammation and fibrosis. Collectively, these data support the utility of a novel renal cell-based approach for slowing renal disease progression associated with diabetic nephropathy in the setting of metabolic syndrome, one of the most common causes of end-stage renal disease.

Human embryonic mesenchymal stem cell-derived conditioned medium rescues kidney function in rats with established chronic kidney disease

Chronic kidney disease (CKD) is a major health care problem, affecting more than 35% of the elderly population worldwide. New interventions to slow or prevent disease progression are urgently needed. Beneficial effects of mesenchymal stem cells (MSC) have been described, however it is unclear whether the MSCs themselves or their secretome is required. We hypothesized that MSC-derived conditioned medium (CM) reduces progression of CKD and studied functional and structural effects in a rat model of established CKD.

CKD was induced by 5/6 nephrectomy (SNX) combined with L-NNA and 6% NaCl diet in Lewis rats. Six weeks after SNX, CKD rats received either 50 µg CM or 50 µg non-CM (NCM) twice daily intravenously for four consecutive days. Six weeks after treatment CM administration was functionally effective: glomerular filtration rate (inulin clearance) and effective renal plasma flow (PAH clearance) were significantly higher in CM vs. NCM-treatment. Systolic blood pressure was lower in CM compared to NCM. Proteinuria tended to be lower after CM. Tubular and glomerular damage were reduced and more glomerular endothelial cells were found after CM. DNA damage repair was increased after CM. MSC-CM derived exosomes, tested in the same experimental setting, showed no protective effect on the kidney. In a rat model of established CKD, we demonstrated that administration of MSC-CM has a long-lasting therapeutic rescue function shown by decreased progression of CKD and reduced hypertension and glomerular injury.

Mesenchymal stem cell therapy prevents interstitial fibrosis and tubular atrophy in a rat kidney allograft model

In solid organ transplantation, mesenchymal stem cell (MSC) therapy is strongly emerging among other cell therapies due to the positive results obtained in vitro and in vivo as an immunomodulatory agent and their potential regenerative role. We aimed at testing whether a single dose of MSCs, injected at 11 weeks after kidney transplantation for the prevention of chronic mechanisms, enhanced regeneration and provided protection against the inflammatory and fibrotic processes that finally lead to the characteristic features of chronic allograft nephropathy (CAN). Either bone marrow mononuclear cells (BMCs) injection or no-therapy (NT) were used as control treatments. A rat kidney transplantation model of CAN with 2.5 h of cold ischemia was used, and functional, histological, and molecular parameters were assessed at 12 and 24 weeks after transplantation. MSC and BMC cell therapy preserves renal function at 24 weeks and abrogates proteinuria, which is typical of this model (NT24w: 68.9 ± 26.5 mg/24 h, MSC24w: 16.6 ± 2.3 mg/24 h, BMC24w: 24.1 ± 5.3 mg/24 h, P<0.03). Only MSC-treated animals showed a reduction in interstitial fibrosis and tubular atrophy (NT24w: 2.3 ± 0.29, MSC24w: 0.4 ± 0.2, P<0.03), less T cells (NT: 39.6 ± 9.5, MSC: 8.1 ± 0.9, P<0.03) and macrophages (NT: 20.9 ± 4.7, MSC: 5.9 ± 1.7, P<0.05) infiltrating the parenchyma and lowered expression of inflammatory cytokines while increasing the expression of anti-inflammatory factors. MSCs appear to serve as a protection from injury development rather than regenerate the damaged tissue, as no differences were observed in Ki67 expression, and kidney injury molecule-1, Clusterin, NGAL, and hepatocyte growth factor expression were only up-regulated in nontreated animals. Considering the results, a single delayed MSC injection is effective for the long-term protection of kidney allografts.

Repairing the chronic damaged kidney: the role of regenerative medicine

The increasing number of patients who suffer from chronic kidney diseases combined with the organ shortage have directed the attention of researchers to new alternatives in the fields of regenerative medicine including cell-based therapies and tissue bioengineering. This review of renal regenerative medicine addresses the mechanisms of action by stem cells to regenerate or repair chronically damaged renal tissue, alternative routes for their delivery, the role of biomaterials in tissue engineering, and the potential therapeutic effects of combining cell therapy with biomaterials. Despite the promise of ongoing work for therapy of chronic renal failure, caution is required as a large gap still exists between scientific knowledge and clinical translation for safe, effective stem cell-based therapies.