Intrarenal Injection of Bone Marrow-Derived Angiogenic Cells Reduces Endothelial Injury and Mesangial Cell Activation in Experimental Glomerulonephritis

Repetitive administration of cultured human CD34+ cells improve adenine-induced kidney injury in mice

BACKGROUND

There is no established treatment to impede the progression or restore kidney function in human chronic kidney disease (CKD).

AIM

To examine the efficacy of cultured human CD34+ cells with enhanced proliferating potential in kidney injury in mice.

METHODS

Human umbilical cord blood (UCB)-derived CD34+ cells were incubated for one week in vasculogenic conditioning medium. Vasculogenic culture significantly increased the number of CD34+ cells and their ability to form endothelial progenitor cell colony-forming units. Adenine-induced tubulointerstitial injury of the kidney was induced in immunodeficient non-obese diabetic/severe combined immunodeficiency mice, and cultured human UCB-CD34+ cells were administered at a dose of 1 × 10⁶/mouse on days 7, 14, and 21 after the start of adenine diet.

RESULTS

Repetitive administration of cultured UCB-CD34+ cells significantly improved the time-course of kidney dysfunction in the cell therapy group compared with that in the control group. Both interstitial fibrosis and tubular damage were significantly reduced in the cell therapy group compared with those in the control group (P < 0.01). Microvasculature integrity was significantly preserved (P < 0.01) and macrophage infiltration into kidney tissue was dramatically decreased in the cell therapy group compared with those in the control group (P < 0.001).

CONCLUSION

Early intervention using human cultured CD34+ cells significantly improved the progression of tubulointerstitial kidney injury. Repetitive administration of cultured human UCB-CD34+ cells significantly improved tubulointerstitial damage in adenine-induced kidney injury in mice via vasculoprotective and anti-inflammatory effects.

Extracellular Vesicles Released from Stem Cells as a New Therapeutic Strategy for Primary and Secondary Glomerulonephritis

Current treatment of primary and secondary glomerulopathies is hampered by many limits and a significant proportion of these disorders still evolves towards end-stage renal disease. A possible answer to this unmet challenge could be represented by therapies with stem cells, which include a variety of progenitor cell types derived from embryonic or adult tissues. Stem cell self-renewal and multi-lineage differentiation ability explain their potential to protect and regenerate injured cells, including kidney tubular cells, podocytes and endothelial cells. In addition, a broad spectrum of anti-inflammatory and immunomodulatory actions appears to interfere with the pathogenic mechanisms of glomerulonephritis. Of note, mesenchymal stromal cells have been particularly investigated as therapy for Lupus Nephritis and Diabetic Nephropathy, whereas initial evidence suggest their beneficial effects in primary glomerulopathies such as IgA nephritis. Extracellular vesicles mediate a complex intercellular communication network, shuttling proteins, nucleic acids and other bioactive molecules from origin to target cells to modulate their functions. Stem cell-derived extracellular vesicles recapitulate beneficial cytoprotective, reparative and immunomodulatory properties of parental cells and are increasingly recognized as a cell-free alternative to stem cell-based therapies for different diseases including glomerulonephritis, also considering the low risk for potential adverse effects such as maldifferentiation and tumorigenesis. We herein summarize the renoprotective potential of therapies with stem cells and extracellular vesicles derived from progenitor cells in glomerulonephritis, with a focus on their different mechanisms of actions. Technological progress and growing knowledge are paving the way for wider clinical application of regenerative medicine to primary and secondary glomerulonephritis: this multi-level, pleiotropic therapy may open new scenarios overcoming the limits and side effects of traditional treatments, although the promising results of experimental models need to be confirmed in the clinical setting.

Extracellular Vesicles Derived from Endothelial Progenitor Cells Protect Human Glomerular Endothelial Cells and Podocytes from Complement- and Cytokine-Mediated Injury

Glomerulonephritis are renal inflammatory processes characterized by increased permeability of the Glomerular Filtration Barrier (GFB) with consequent hematuria and proteinuria. Glomerular endothelial cells (GEC) and podocytes are part of the GFB and contribute to the maintenance of its structural and functional integrity through the release of paracrine mediators. Activation of the complement cascade and pro-inflammatory cytokines (CK) such as Tumor Necrosis Factor α (TNF-α) and Interleukin-6 (IL-6) can alter GFB function, causing acute glomerular injury and progression toward chronic kidney disease. Endothelial Progenitor Cells (EPC) are bone-marrow-derived hematopoietic stem cells circulating in peripheral blood and able to induce angiogenesis and to repair injured endothelium by releasing paracrine mediators including Extracellular Vesicles (EVs), microparticles involved in intercellular communication by transferring proteins, lipids, and genetic material (mRNA, microRNA, lncRNA) to target cells. We have previously demonstrated that EPC-derived EVs activate an angiogenic program in quiescent endothelial cells and renoprotection in different experimental models. The aim of the present study was to evaluate in vitro the protective effect of EPC-derived EVs on GECs and podocytes cultured in detrimental conditions with CKs (TNF-α/IL-6) and the complement protein C5a. EVs were internalized in both GECs and podocytes mainly through a L-selectin-based mechanism. In GECs, EVs enhanced the formation of capillary-like structures and cell migration by modulating gene expression and inducing the release of growth factors such as VEGF-A and HGF. In the presence of CKs, and C5a, EPC-derived EVs protected GECs from apoptosis by decreasing oxidative stress and prevented leukocyte adhesion by inhibiting the expression of adhesion molecules (ICAM-1, VCAM-1, E-selectin). On podocytes, EVs inhibited apoptosis and prevented nephrin shedding induced by CKs and C5a. In a co-culture model of GECs/podocytes that mimicked GFB, EPC-derived EVs protected cell function and permeselectivity from inflammatory-mediated damage. Moreover, RNase pre-treatment of EVs abrogated their protective effects, suggesting the crucial role of RNA transfer from EVs to damaged glomerular cells. In conclusion, EPC-derived EVs preserved GFB integrity from complement- and cytokine-induced damage, suggesting their potential role as therapeutic agents for drug-resistant glomerulonephritis.

Concise review: current trends on applications of stem cells in diabetic nephropathy

Diabetic nephropathy, with high prevalence, is the main cause of renal failure in diabetic patients. The strategies for treating DN are limited with not only high cost but an unsatisfied effect. Therefore, the effective treatment of DN needs to be explored urgently. In recent years, due to their self-renewal ability and multi-directional differentiation potential, stem cells have exerted therapeutic effects in many diseases, such as graft-versus-host disease, autoimmune diseases, pancreatic diseases, and even acute kidney injury. With the development of stem cell technology, stem cell-based regenerative medicine has been tried to be applied to the treatment of DN. Related stem cells include embryonic stem cells, induced pluripotent stem cells, mesenchymal cells, and endothelial progenitor cells. Undoubtedly, stem cell transplantation has achieved certain results in the treatment of DN animal models. However, stem cell therapy still remains certain thorny issues during treatment. For instance, poor engraftment and limited differentiation of stem cells caused by the diabetic microenvironment, differentiation into unwanted cell lineages, and malignant transformation or genetic aberrations of stem cells. At present, various researches on the therapeutic effects of stem cells in DN with different opinions are reported and the specific mechanism of stem cells is still unclear. We review here the potential mechanism of stem cells as new therapeutic agents in the treatment of DN. Also, we review recent findings and updated information about not only the utilization of stem cells on DN in both preclinical and clinical trials but limitations and future expectations of stem cell-based therapy for DN.

Intrarenal Transplantation of Hypoxic Preconditioned Mesenchymal Stem Cells Improves Glomerulonephritis through Anti-Oxidation, Anti-ER Stress, Anti-Inflammation, Anti-Apoptosis, and Anti-Autophagy

To confer further therapeutic potential and prevent some adverse effects by the mesenchymal stem cells (MSCs) transplantation, we explored the effects of locally intrarenal arterial administration of hypoxic preconditioned MSCs in the anti-Thy1.1 induced rat glomerulonephritis. Proteinuria, histochemical staining, and western blotting were used to explore the therapeutic effects and mechanisms. Locally intrarenal arterial MSCs transplantation successfully implanted the fluorescent or CD44 labeled MSCs in the nephritic glomeruli, ameliorated proteinuria, and glomerulosclerosis in nephritic rats. Hypoxic preconditioning significantly upregulated hypoxic inducible factor-1α/VEGF (HIF-1α/VEGF) in the MSCs and was more efficient than normoxic MSCs in reducing the degree of urinary protein, glomerulosclerosis, fibrosis, macrophage/monocyte infiltration, GRP78 mediated endoplasmic reticulum stress, Beclin-1/LC3-II mediated autophagy, and Bax/Bcl-2/caspase 3 mediated apoptosis. Hypoxic MSCs could further promote intranuclear nuclear factor (erythroid-derived 2, Nrf2) and reduce nuclear factor kappa B expression in nephritic kidneys. As compared to normoxic MSCs, hypoxic MSCs transplantation significantly upregulated the renal expression of anti-oxidative response elements/enzymes including glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, glutathione peroxidase, catalase, Mn, and Cu/Zn superoxide dismutase. In summary, intrarenal hypoxic preconditioning MSCs transplantation was more effective to activate hypoxic inducible factor-1α/VEGF/Nrf2 (HIF-1α/VEGF/Nrf2) signaling, preserve anti-oxidant proteins and anti-oxidative responsive element proteins, and subsequently reduce glomerular apoptosis, autophagy, and inflammation.

Maternal peripheral blood CD34+ cells for prediction of fetal kidney malformations: results from a case-control analysis

PURPOSE

To evaluate the relation between CD34⁺ cells count in maternal blood and potential development of fetal congenital renal abnormalities.

MATERIALS AND METHODS

We enrolled 16 women that gave birth to newborns carrying congenital renal malformations over a 3-year period and 48 women with uncomplicated pregnancies (controls) in a 1:3 ratio (three controls per case).

RESULTS

CD34⁺ cells in the maternal peripheral blood were significantly lower in the group of women who gave birth to newborns carrying congenital renal malformations compared to the controls (p < .0001).

CONCLUSIONS

CD34⁺ cells in maternal blood could be validated as a potential marker to predict the development of possible kidney malformations.

The use of hydrogels for cell-based treatment of chronic kidney disease

Chronic kidney disease (CKD) is a major and growing public health concern with increasing incidence and prevalence worldwide. The therapeutic potential of stem cell therapy, including mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) holds great promise for treatment of CKD. However, there are significant bottlenecks in the clinical translation due to the reduced number of transplanted cells and the duration of their presence at the site of tissue damage. Bioengineered hydrogels may provide a route of cell delivery to enhance treatment efficacy and optimise the targeting effectiveness while minimising any loss of cell function. In this review, we highlight the advances in stem cell therapy targeting kidney disease and discuss the emerging role of hydrogel delivery systems to fully realise the potential of adult stem cells as a regenerative therapy for CKD in humans. MSCs and EPCs mediate kidney repair through distinct paracrine effects. As a delivery system, hydrogels can prolong these paracrine effects by improving retention at the site of injury and protecting the transplanted cells from the harsh inflammatory microenvironment. We also discuss the features of a hydrogel, which may be tuned to optimise the therapeutic potential of encapsulated stem cells, including cell-adhesive epitopes, material stiffness, nanotopography, modes of gelation and degradation and the inclusion of bioactive molecules. This review concludes with a discussion of the challenges to be met for the widespread clinical use of hydrogel delivery system of stem cell therapy for CKD.

Endothelial Progenitor Cells and Kidney Diseases

Endothelial progenitor cells (EPC) are bone marrow derived or tissue-resident cells that play major roles in the maintenance of vascular integrity and repair of endothelial damage. Although EPCs may be capable of directly engrafting and regenerating the endothelium, the most important effects of EPCs seem to be depended on paracrine effects. In recent studies, specific microvesicles and mRNAs have been found to mediate the pro-angiogenic and regenerative effects of EPCs on endothelium. EPC counts have important prognostic implications in cardiovascular diseases (CVD). Uremia and inflammation are associated with lower EPC counts which probably contribute to increased CVD risks in patients with chronic kidney disease. Beneficial effects of the EPC therapies have been shown in studies performed on different models of CVD and kidney diseases such as acute and chronic kidney diseases and glomerulonephritis. However, lack of a clear definition and specific marker of EPCs is the most important problem causing difficulties in interpretation of the results of the studies investigating EPCs.

The role of nonautologous and autologous adipose-derived mesenchymal stem cell in acute pyelonephritis

We compared the therapeutic effects of autologous and nonautologous adipose-derived mesenchymal stem cell (ADMSC), in ameliorating the renal function in a rabbit model of acute pyelonephritis. The difference of perirenal and neck subcutaneous ADMSCs were also evaluated. Twenty female rabbits were apportioned to 5 groups. In group I (n = 4), the rabbits were injected direct inoculation of Escherichia coli (E. coli) into the right kidney. In group II (n = 4), autologous ADMSCs obtained from nape adipose tissue were injected into the subcapsular space 1 week after E. coli injection, while nonautologous ADMSCs of the same origin (from male rabbits) were applied in group III (n = 4). In group IV (n = 4), autologous perirenal ADMSCs were applied with the same method, while perirenal nonautologous ADMSCs from male rabbits were used in group V (n = 4). Technetium-99m-DMSA renal scan was performed 1, 2 and 4 months post-injection in all groups. Kidneys were excised for the evaluation of histopathological changes in the same time points. PCR examination for detection of Y-chromosome (in group III and V) and fluorescent evaluation (in group II and IV) were also performed to determine the fate of injected cells. Injection of autologous ADMSCs resulted in more satisfactory outcomes in reduction of interstitial fibrosis, tubular, and glomerular atrophy as compared to nonautologous groups. However, histopathological ameliorations were significantly better in group IV in which autologous perirenal ADMSC was applied. Remarkably, two months after the injection, Technetium-99m-DMSA renal scan showed that right kidney reached to near normal cortical function (48 and 45%) in group IV and V, respectively as compared to groups II (41%) and III (37%). Autologous ADMSCs may have better results in cell therapy as compared to nonautologous cells. However, more satisfactory outcomes may be obtained when the cell source is selected from the surrounding adipose tissue.

Stem cell therapy: An emerging modality in glomerular diseases

The kidney has been considered a highly terminally differentiated organ with low proliferative potential and thus unlikely to undergo regeneration. Glomerular disease progresses to end-stage renal disease (ESRD), which requires dialysis or renal transplantation for better quality of life for patients with ESRD. Because of the shortage of implantable kidneys and complications such as immune rejection, septicemia and toxicity of immunosuppression, kidney transplantation remains a challenge. Therapeutic options available for glomerular disease include symptomatic treatment and strategies to delay progression. In an attempt to develop innovative treatments by promoting the limited capability of regeneration and repair after kidney injury and overcome the progressive pathological process that is uncontrolled with conventional treatment modalities, stem cell-based therapy has emerged as novel intervention due to its ability to inhibit inflammation and promote regeneration. Recent developments in cell therapy have demonstrated promising therapeutic outcomes in terms of restoration of renal structure and function. This review focuses on stem cell therapy approaches for the treatment of glomerular disease, including the various cell sources used and recent advances in preclinical and clinical studies.

Characterization of a Fetal Liver Cell Population Endowed with Long-Term Multiorgan Endothelial Reconstitution Potential

Stable reconstitution of vascular endothelial beds upon transplantation of progenitor cells represents an important challenge due to the paucity and generally limited integration/expansion potential of most identified vascular related cell subsets. We previously showed that mouse fetal liver (FL) hemato/vascular cells from day 12 of gestation (E12), expressing the Stem Cell Leukaemia (SCL) gene enhancer transgene (SCL‐PLAP⁺ cells), had robust endothelial engraftment potential when transferred to the blood stream of newborns or adult conditioned recipients, compared to the scarce vascular contribution of adult bone marrow cells. However, the specific SCL‐PLAP⁺ hematopoietic or endothelial cell subset responsible for the long‐term reconstituting endothelial cell (LTR‐EC) activity and its confinement to FL developmental stages remained unknown. Using a busulfan‐treated newborn transplantation model, we show that LTR‐EC activity is restricted to the SCL‐PLAP⁺VE‐cadherin⁺CD45⁻ cell population, devoid of hematopoietic reconstitution activity and largely composed by Lyve1⁺ endothelial‐committed cells. SCL‐PLAP⁺ Ve‐cadherin⁺CD45⁻ cells contributed to the liver sinusoidal endothelium and also to the heart, kidney and lung microvasculature. LTR‐EC activity was detected at different stages of FL development, yet marginal activity was identified in the adult liver, revealing unknown functional differences between fetal and adult liver endothelial/endothelial progenitors. Importantly, the observations that expanding donor‐derived vascular grafts colocalize with proliferating hepatocyte‐like cells and participate in the systemic circulation, support their functional integration into young livers. These findings offer new insights into the engraftment, phonotypical, and developmental characterization of a novel endothelial/endothelial progenitor cell subtype with multiorgan LTR‐EC activity, potentially instrumental for the treatment/genetic correction of vascular diseases. Stem Cells2017;35:507–521

Specific endothelial heparin-binding EGF-like growth factor deletion ameliorates renal injury induced by chronic angiotensin II infusion

Transactivation of EGF receptor (EGFR) by angiotensin II (Ang II) plays important roles in the initiation and progression of chronic kidney diseases. Studies suggest that heparin-binding EGF-like factor (HB-EGF) may be a critical mediator in this process, but its role in vivo has not been investigated. In the current study, we found that in response to Ang II infusion, kidneys from endothelial HB-EGF deletion mice had significantly reduced EGFR activation compared with controls. Meanwhile, deletion of endothelial HB-EGF expression decreased Ang II infusion related renal injury, as demonstrated by 1) less albuminuria; 2) less glomerulosclerosis; 3) preserved endothelial integrity and decreased podocyte injury, as shown by greater glomerular tuft area and WT1-positive cells, and fewer apoptotic cells measured by cleaved caspase 3 staining; 4) reduced inflammation in the perivascular area and interstitium measured by F4/80 and CD3 immunostaining; and 5) reduced renal fibrosis. In conclusion, our results suggest that shedding of HB-EGF from endothelium plays an important role in Ang II-induced renal injury by linking Ang II-AT1R with EGFR transactivation. Inhibition of HB-EGF shedding could be a potential therapeutic strategy for chronic kidney disease.

Extrarenal Progenitor Cells Do Not Contribute to Renal Endothelial Repair

Endothelial progenitor cells (EPCs) may be relevant contributors to endothelial cell (EC) repair in various organ systems. In this study, we investigated the potential role of EPCs in renal EC repair. We analyzed the major EPC subtypes in murine kidneys, blood, and spleens after induction of selective EC injury using the concanavalin A/anti-concanavalin A model and after ischemia/reperfusion (I/R) injury as well as the potential of extrarenal cells to substitute for injured local EC. Bone marrow transplantation (BMTx), kidney transplantation, or a combination of both were performed before EC injury to allow distinction of extrarenal or BM-derived cells from intrinsic renal cells. During endothelial regeneration, cells expressing markers of endothelial colony-forming cells (ECFCs) were the most abundant EPC subtype in kidneys, but were not detected in blood or spleen. Few cells expressing markers of EC colony-forming units (EC-CFUs) were detected. In BM chimeric mice (C57BL/6 with tandem dimer Tomato-positive [tdT+] BM cells), circulating and splenic EC-CFUs were BM-derived (tdT+), whereas cells positive for ECFC markers in kidneys were not. Indeed, most BM-derived tdT+ cells in injured kidneys were inflammatory cells. Kidneys from C57BL/6 donors transplanted into tdT+ recipients with or without prior BMTx from C57BL/6 mice were negative for BM-derived or extrarenal ECFCs. Overall, extrarenal cells did not substitute for any intrinsic ECs. These results demonstrate that endothelial repair in mouse kidneys with acute endothelial lesions depends exclusively on local mechanisms.

The real face of endothelial progenitor cells - Circulating angiogenic cells as endothelial prognostic marker?

Endothelial progenitor cells (EPCs) have been extensively studied for almost 19 years now and were considered as a potential marker for endothelial regeneration ability. On the other hand, circulating endothelial cells (CEC) were studied as biomarker for endothelial injury. Yet, in the literature, there is also huge incoherency in regards to terminology and protocols used. This results in misleading conclusions on the role of so called "EPCs", especially in the clinical field. The discrepancies are mainly due to strong phenotypic overlap between EPCs and circulating angiogenic cells (CAC), therefore changes in "EPC" terminology have been suggested. Other factors leading to inconsistent results are varied definitions of the studied populations and the lack of universal data reporting, which could strongly affect data interpretation. The current review is focused on controversies concerning the use of "EPCs"/CAC and CEC as putative endothelial diagnostic markers.

Effect of mesenchymal stem cells on anti-Thy1,1 induced kidney injury in albino rats

OBJECTIVE

To evaluate the effect of mesenchymal stem cells (MSCs) in rats with anti-Thy1,1 nephritis.

METHODS

Female albino rats were divided into three groups, control group, anti-Thy1,1 group and treatment with i.v. MSCs group. MSCs were derived from bone marrow of male albino rats, Y-chromosome gene was detected by polymerase chain reaction in the kidney. Serum urea and creatinine were estimated for all groups. Kidney of all studied groups was examined histologically and histochemically (total carbohydrates and total proteins). DNA fragmentation and expression of α-SMA were detected.

RESULTS

Kidney of animals injected with anti-Thy1,1 showed inflammatory leucocytic infiltration, hypertrophied glomeruli, tubular necrosis and congestion in the renal blood vessels. The kidney tissue also showed reduction of carbohydrates and total proteins together with increase in apoptosis and in expression of α-SMA. Moreover, the levels of urea and creatinine were elevated. Treating animals with MSCs revealed that kidney tissue displayed an improvement in the histological and histochemical changes. Apoptosis and α-SMA expression were decreased, and the levels of urea and creatinine decreased.

CONCLUSIONS

The obtained results demonstrated the potential of MSCs to ameliorate the structure and function of the kidney in rats with anti-Thy1,1 nephritis possibly through the release of paracrine growth factor(s).

Endothelial progenitor cell-derived extracellular vesicles protect from complement-mediated mesangial injury in experimental anti-Thy1.1 glomerulonephritis

BACKGROUND

Endothelial progenitor cells (EPCs) are known to induce tissue repair by paracrine mechanisms including the release of growth factors and extracellular vesicles (EVs), nanoparticles able to carry proteins and genetic information to target cells. The aim of this study was to evaluate whether EVs derived from EPCs may protect from complement-mediated mesangial injury in experimental anti-Thy1.1 glomerulonephritis.

METHODS

EVs were isolated by serial ultracentrifugation from supernatants of cultured human EPCs and characterized for their protein and RNA content. In vivo, EVs were injected i.v. in the experimental rat model of mesangiolytic anti-Thy1.1 glomerulonephritis evaluating renal function, proteinuria, complement activity and histological lesions. In vitro, the biological effects of EPC-derived EVs were studied in cultured rat mesangial cells incubated with anti-Thy1.1 antibody and rat or human serum as complement source.

RESULTS

After i.v. injection in Thy1.1-treated rats, EVs localized within injured glomeruli and inhibited mesangial cell activation, leucocyte infiltration and apoptosis, decreased proteinuria, increased serum complement haemolytic activity (CH50) and ameliorated renal function. EV treatment decreased intraglomerular deposition of the membrane attack complex (MAC or C5b-9) and expression of smooth muscle cell actin and preserved the endothelial antigen RECA-1 and the podocyte marker synaptopodin. The protective effect of EVs was significantly reduced by pre-treatment with a high dose of RNase (1 U/mL), suggesting a key role for EV-carried RNAs in these mechanisms. Indeed, EPC-derived EVs contained different mRNAs coding for several anti-apoptotic molecules and for the complement inhibitors Factor H, CD55 and CD59 and the related proteins. The in vitro experiments aimed to investigate the mechanisms of EV protection indicated that EVs transferred to mesangial cell mRNAs coding for Factor H, CD55 and CD59 and inhibited anti-Thy1.1 antibody/complement-induced apoptosis and C5b-9/C3 mesangial cell deposition.

CONCLUSIONS

EVs derived from EPCs exert a protective effect in Thy1.1 glomerulonephritis by inhibition of antibody- and complement-mediated injury of mesangial cells.

Mesenchymal Stromal Cells Improve Renovascular Function in Polycystic Kidney Disease

Polycystic kidney disease (PKD) is a common cause of end-stage renal failure, for which there is no accepted treatment. Progenitor and stem cells have been shown to restore renal function in a model of renovascular disease, a disease that shares many features with PKD. The objective of this study was to examine the potential of adult stem cells to restore renal structure and function in PKD. Bone marrow-derived mesenchymal stromal cells (MSCs, 2.5 × 10(5)) were intrarenally infused in 6-week-old PCK rats. At 10 weeks of age, PCK rats had an increase in systolic blood pressure (SBP) versus controls (126.22 ± 2.74 vs. 116.45 ± 3.53 mmHg, p < 0.05) and decreased creatinine clearance (3.76 ± 0.31 vs. 6.10 ± 0.48 µl/min/g, p < 0.01), which were improved in PKD animals that received MSCs (SBP: 114.67 ± 1.34 mmHg, and creatinine clearance: 4.82 ± 0.24 µl/min/g, p = 0.001 and p = 0.003 vs. PKD, respectively). MSCs preserved vascular density and glomeruli diameter, measured using microcomputed tomography. PCK animals had increased urine osmolality (843.9 ± 54.95 vs. 605.6 ± 45.34 mOsm, p < 0.01 vs. control), which was improved after MSC infusion and not different from control (723.75 ± 56.6 mOsm, p = 0.13 vs. control). Furthermore, MSCs reduced fibrosis and preserved the expression of proangiogenic molecules, while cyst size and number were unaltered by MSCs. Delivery of exogenous MSCs improved vascular density and renal function in PCK animals, and the benefit was observed up to 4 weeks after a single infusion. Cell-based therapy constitutes a novel approach in PKD.

Stem cell-based cell therapy for glomerulonephritis

Glomerulonephritis (GN), characterized by immune-mediated inflammatory changes in the glomerular, is a common cause of end stage renal disease. Therapeutic options for glomerulonephritis applicable to all cases mainly include symptomatic treatment and strategies to delay progression. In the attempt to yield innovative interventions fostering the limited capability of regeneration of renal tissue after injury and the uncontrolled pathological process by current treatments, stem cell-based therapy has emerged as novel therapy for its ability to inhibit inflammation and promote regeneration. Many basic and clinical studies have been performed that support the ability of various stem cell populations to ameliorate glomerular injury and improve renal function. However, there is a long way before putting stem cell-based therapy into clinical practice. In the present article, we aim to review works performed with respect to the use of stem cell of different origins in GN, and to discuss the potential mechanism of therapeutic effect and the challenges for clinical application of stem cells.

Regenerative medicine for the kidney: renotropic factors, renal stem/progenitor cells, and stem cell therapy

The kidney has the capacity for regeneration and repair after a variety of insults. Over the past few decades, factors that promote repair of the injured kidney have been extensively investigated. By using kidney injury animal models, the role of intrinsic and extrinsic growth factors, transcription factors, and extracellular matrix in this process has been examined. The identification of renal stem cells in the adult kidney as well as in the embryonic kidney is an active area of research. Cell populations expressing putative stem cell markers or possessing stem cell properties have been found in the tubules, interstitium, and glomeruli of the normal kidney. Cell therapies with bone marrow-derived hematopoietic stem cells, mesenchymal stem cells, endothelial progenitor cells, and amniotic fluid-derived stem cells have been highly effective for the treatment of acute or chronic renal failure in animals. Embryonic stem cells and induced pluripotent stem cells are also utilized for the construction of artificial kidneys or renal components. In this review, we highlight the advances in regenerative medicine for the kidney from the perspective of renotropic factors, renal stem/progenitor cells, and stem cell therapies and discuss the issues to be solved to realize regenerative therapy for kidney diseases in humans.

Induced autologous stem cell transplantation for treatment of rabbit renal interstitial fibrosis

Introduction

Renal interstitial fibrosis (RIF) is a significant cause of end-stage renal failure. The goal of this study was to characterize the distribution of transplanted induced autologous stem cells in a rabbit model of renal interstitial fibrosis and evaluate its therapeutic efficacy for treatment of renal interstitial fibrosis.

Methods

A rabbit model of renal interstitial fibrosis was established. Autologous fibroblasts were cultured, induced and labeled with green fluorescent protein (GFP). These labeled stem cells were transplanted into the renal artery of model animals at 8 weeks.

Results

Eight weeks following transplantation of induced autologous stem cells, significant reductions (P < 0.05) were observed in serum creatinine (SCr) (14.8 ± 1.9 mmol/L to 10.1 ± 2.1 mmol/L) and blood urea nitrogen (BUN) (119 ± 22 µmol/L to 97 ± 13 µmol/L), indicating improvement in renal function.

Conclusions

We successfully established a rabbit model of renal interstitial fibrosis and demonstrated that transplantation of induced autologous stem cells can repair kidney damage within 8 weeks. The repair occurred by both inhibition of further development of renal interstitial fibrosis and partial reversal of pre-existing renal interstitial fibrosis. These beneficial effects lead to the development of normal tissue structure and improved renal function.

Circulating and tissue resident endothelial progenitor cells

Progenitor cells for the endothelial lineage have been widely investigated for more than a decade, but continue to be controversial since no unique identifying marker has yet been identified. This review will begin with a discussion of the basic tenets originally proposed for proof that a cell displays properties of an endothelial progenitor cell. We then provide an overview of the methods for putative endothelial progenitor cell derivation, expansion, and enumeration. This discussion includes consideration of cells that are present in the circulation as well as cells resident in the vascular endothelial intima. Finally, we provide some suggested changes in nomenclature that would greatly clarify and demystify the cellular elements involved in vascular repair.

Effect of stem cell therapy on adriamycin induced tubulointerstitial injury

BACKGROUND AND OBJECTIVES

It was postulated that adriamycin (ADR) induce renal tubulointerstitial injury. Clinicians are faced with a challenge in producing response in renal patients and slowing or halting the evolution towards kidney failure. The present study aimed at investigating the relation between the possible therapeutic effect of human mesenchymal stem cells (HMSCs), isolated from cord blood on tubular renal damage and their distribution by using ADR induced nephrotoxicity as a model in albino rat.

METHODS AND RESULTS

Thirty three male albino rats were divided into control group, ADR group where rats were given single intraperitoneal (IP) injection of 5 mg/kg adriamycin. The rats were sacrificed 10, 20 and 30 days following confirmation of tubular injury. In stem cell therapy group, rats were injected with HMSCs following confirmation of renal injury and sacrificed 10, 20 and 30 days after HMSCs therapy. Kidney sections were exposed to histological, histochemical, immunohistochemical, morphometric and serological studies. In response to SC therapy, vacuolated cytoplasm, dark nuclei, detached epithelial lining and desquamated nuclei were noticed in few collecting tubules (CT). 10, 20 and 30 days following therapy. The mean count of CT showing desquamated nuclei and mean value of serum creatinine revealed significant difference in ADR group. The mean area% of Prussian blue+ve cells and that of CD105 +ve cells measured in subgroup S1 denoted a significant increase compared to subgroups S2 and S3.

CONCLUSIONS

ADR induced tubulointerstitial damage that regressed in response to cord blood HMSC therapy.

Stem cells: potential and challenges for kidney repair

Renal damage resulting from acute and chronic kidney injury poses an important problem to public health. Currently, patients with end-stage renal disease rely solely on kidney transplantation or dialysis for survival. Emerging therapies aiming to prevent and reverse kidney damage are thus in urgent need. Although the kidney was initially thought to lack the capacity for self-repair, several studies have indicated that this might not be the case; progenitor and stem cells appear to play important roles in kidney repair under various pathological conditions. In this review, we summarize recent findings on the role of progenitor/stem cells on kidney repair as well as discuss their potential as a therapeutic approach for kidney diseases.

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.

Kallikrein transduced mesenchymal stem cells protect against anti-GBM disease and lupus nephritis by ameliorating inflammation and oxidative stress

Previously we have shown that kallikreins (klks) play a renoprotective role in nephrotoxic serum induced nephritis. In this study, we have used mesenchymal stem cells (MSCs) as vehicles to deliver klks into the injured kidneys and have measured their therapeutic effect on experimental antibody induced nephritis and lupus nephritis. Human KLK-1 (hKLK1) gene was transduced into murine MSCs using a retroviral vector to generate a stable cell line, hKLK1-MSC, expressing high levels of hKLK1. 129/svj mice subjected to anti-GBM induced nephritis were transplanted with 10⁶ hKLK1-MSCs and hKLK1 expression was confirmed in the kidneys. Compared with vector-MSCs injected mice, the hKLK1-MSCs treated mice showed significantly reduced proteinuria, blood urea nitrogen (BUN) and ameliorated renal pathology. Using the same strategy, we treated lupus-prone B6.Sle1.Sle3 bicongenic mice with hKLK1-MSCs and demonstrated that hKLK1-MSCs delivery also attenuated lupus nephritis. Mechanistically, hKLK1-MSCs reduced macrophage and T-lymphocyte infiltration into the kidney by suppressing the expression of inflammation cytokines. Moreover, hKLK1 transduced MSCs were more resistant to oxidative stress-induced apoptosis. These findings advance genetically modified MSCs as potential gene delivery tools for targeting therapeutic agents to the kidneys in order to modulate inflammation and oxidative stress in lupus nephritis.

Bone marrow cell therapies for endothelial repair and their relevance to kidney disease

Endothelial injury is a characteristic finding in chronic kidney disease and is associated with both markedly increased cardiovascular risk and chronic kidney disease progression. The past decade has seen a remarkable surge of interest in the role of bone marrow-derived cells for the protection, repair, and regeneration of injured endothelium. In particular, despite controversies regarding their mechanisms of action, endothelial progenitor cells have garnered considerable attention, with multiple reports suggesting that these cells exhibit remarkable pro-angiogenic effects. Recent advances in our understanding of how the bone marrow responds to endothelial injury now suggest that multiple bone marrow cell populations, including both endothelial progenitor cells and a novel group of cells called early outgrowth cells, promote endothelial repair and regeneration through different, yet complementary, mechanisms. Moreover, certain subsets of bone marrow-derived cells also appear to have novel, potent, angiogenesis-independent tissue-protective properties. The bone marrow should thus now be viewed not only as a hematopoiesis organ, but also as a rich reservoir of cells capable of protecting and even regenerating nonhematopoietic tissues such as the kidney. To harness the prognostic and therapeutic potential of the bone marrow, the renal community must be aware of recent advances in our understanding of the nature and therapeutic potential of these cells.

A novel, dual role of CCN3 in experimental glomerulonephritis: pro-angiogenic and antimesangioproliferative effects

In contrast to factors that promote mesangial cell proliferation, little is known about their endogenous inhibitors. During experimental mesangioproliferative nephritis, expression of the glomerular CCN3 (nephroblastoma overexpressed gene [NOV]) gene is reduced before the proliferative phase and increased in glomeruli and serum when mesangial cell proliferation subsides. To further elucidate its role in mesangioproliferative glomerulonephritis, CCN3 systemically was overexpressed by muscle electroporation in healthy or nephritic rats. This increased CCN3 serum concentrations more than threefold for up to 56 days. At day 5 after disease induction, CCN3-transfected rats showed an increase in glomerular endothelial area and in mRNA levels of the pro-angiogenic factors vascular endothelial growth factor and PDGF-C. At day 7, CCN3 overexpression decreased mesangial cell proliferation, including expression of α-smooth muscle actin and matrix accumulation of fibronectin and type IV collagen. In progressive nephritis (day 56), overexpression of CCN3 resulted in decreased albuminuria, glomerulosclerosis, and reduced cortical collagen type I accumulation. In healthy rat kidneys, overexpression of CCN3 induced no morphologic changes but regulated glomerular gene transcripts (reduced transcription of PDGF-B, PDGF-D, PDGF-receptor-β, and fibronectin, and increased PDGF-receptor-α and PDGF-C mRNA). These data identify a dual role for CCN3 in experimental glomerulonephritis with pro-angiogenic and antimesangioproliferative effects. Manipulation of CCN3 may represent a novel approach to help repair glomerular endothelial damage and mesangioproliferative changes.

Microvesicles derived from endothelial progenitor cells protect the kidney from ischemia-reperfusion injury by microRNA-dependent reprogramming of resident renal cells

Endothelial progenitor cells are known to reverse acute kidney injury by paracrine mechanisms. We previously found that microvesicles released from these progenitor cells activate an angiogenic program in endothelial cells by horizontal mRNA transfer. Here, we tested whether these microvesicles prevent acute kidney injury in a rat model of ischemia-reperfusion injury. The RNA content of microvesicles was enriched in microRNAs (miRNAs) that modulate proliferation, angiogenesis, and apoptosis. After intravenous injection following ischemia-reperfusion, the microvesicles were localized within peritubular capillaries and tubular cells. This conferred functional and morphologic protection from acute kidney injury by enhanced tubular cell proliferation, reduced apoptosis, and leukocyte infiltration. Microvesicles also protected against progression of chronic kidney damage by inhibiting capillary rarefaction, glomerulosclerosis, and tubulointerstitial fibrosis. The renoprotective effect of microvesicles was lost after treatment with RNase, nonspecific miRNA depletion of microvesicles by Dicer knock-down in the progenitor cells, or depletion of pro-angiogenic miR-126 and miR-296 by transfection with specific miR-antagomirs. Thus, microvesicles derived from endothelial progenitor cells protect the kidney from ischemic acute injury by delivering their RNA content, the miRNA cargo of which contributes to reprogramming hypoxic resident renal cells to a regenerative program.

VEGF: Potential therapy for renal regeneration

Vascular endothelial growth factor (VEGF) plays a central role in angiogenesis. A number of studies have focused on its role in health and disease and discussed the possibility of VEGF as both a therapeutic tool and target based on its specific actions on vascular proliferation and cell survival. On one side, anti-VEGF therapies are at the fore-front of treatment of many solid tumors, but blockade of VEGF carries collateral effects such as hypertension and renal damage largely due to abnormalities in the microvasculature. On the other hand, recent clinical and experimental evidence has shown the feasibility of using VEGF administration to protect ischemic tissues such as the myocardium or the kidney via stimulation of microvascular proliferation and repair. In this commentary, we discuss the possibility and potential mechanisms of using intra-renal administration of VEGF to preserve the renal microcirculation and, consequently, decrease progressive renal injury in chronic renovascular disease. Targeted administration of VEGF may constitute a novel stand-alone or co-adjuvant intervention with the potential to become a part of a comprehensive plan to protect renal function.

Eicosapentaenoic acid regulates IκBα and prevents tubulointerstitial injury in kidney

Fish oil containing n-3 polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is well known to prevent the progression of IgA nephropathy. However, the mechanism through which fish oil prevents the progression of renal injury remains uncertain. We tried to clarify the effects of EPA on tubulointerstitial injury in the kidney both in vivo and in vitro. We examined the effects of EPA, especially to focus on nuclear factor kappa B (NF-κB), using Thy-1 nephritis models. Also the mechanism of EPA was investigated using small-interfering RNA (siRNA) in lipopolysaccharide (LPS)-stimulated proximal tubular epithelial cells (PTECs). In Thy-1 nephritis models, EPA significantly inhibited tubulointerstitial injury and the infiltration of macrophages into tubulointerstitial lesions except severe glomerular injury at early stage. Compared with control animals, NF-κB activation was significantly augmented in the Thy-1 nephritic kidney. However, treatment with EPA significantly reduced NF-κB activation, down-regulated the expressions of NF-κB-dependent molecules. Also in LPS-stimulated PTECs, LPS augmented NF-κB activation and the expression of NF-κB-dependent molecules. As in the case with the Thy-1 nephritis models, treatment with EPA inhibited them, prevented the degradation of IκBα in LPS-stimulated PTECs. Pre-treatment with siRNA for IκBα abolished the inhibitory effect of EPA on LPS-induced NF-κB activation, suggesting that EPA inhibited NF-κB activation by regulating IκBα. Our results indicate that EPA prevents the early progression of tubulointerstitial injury in Thy-1 nephritis models, and the inhibitory effect of EPA on the expression of inflammatory molecules via the regulation of IκBα in cultured cells may explain this mechanism.

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.

Endothelial progenitor cells homing and renal repair in experimental renovascular disease

Tissue injury triggers reparative processes that often involve endothelial progenitor cells (EPCs) recruitment. We hypothesized that atherosclerotic renal artery stenosis (ARAS) activates homing signals that would be detectable in both the kidney and EPCs, and attenuated on renal repair using selective cell-based therapy. Pigs were treated with intrarenal autologous EPC after 6 weeks of ARAS. Four weeks later, expression of homing-related signals in EPC and kidney, single kidney function, microvascular (MV) density, and morphology were compared with untreated ARAS and normal control pigs (n = 7 each). Compared with normal EPC, EPC from ARAS pigs showed increased stromal cell-derived factor (SDF)-1, angiopoietin-1, Tie-2, and c-kit expression, but downregulation of erythropoietin (EPO) and its receptor. The ARAS kidney released the c-kit-ligand stem cell factor, uric acid, and EPO, and upregulated integrin beta2, suggesting activation of corresponding homing signaling. However, angiopoietin-1 and SDF-1/CXCR4 were not elevated. Administration of EPC into the stenotic kidney restored angiogenic activity, improved MV density, renal hemodynamics and function, decreased fibrosis and oxidative stress, and attenuated endogenous injury signals. The ARAS kidney releases specific homing signals corresponding to cognate receptors expressed by EPC. EPC show plasticity for organ-specific recruitment strategies, which are upregulated in early atherosclerosis. EPC are renoprotective as they attenuated renal dysfunction and damage in chronic ARAS, and consequently decreased the injury signals. Importantly, manipulation of homing signals may potentially allow therapeutic opportunities to increase endogenous EPC recruitment.

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.

Optimization of culture conditions for endothelial progenitor cells from porcine bone marrow in vitro

OBJECTIVES

The aim of this study was to determine an optimal culture method for porcine bone marrow-derived endothelial progenitor cells (EPCs).

MATERIALS AND METHODS

Mononuclear cells (MNCs) were isolated by density centrifugation and differentiated into EPCs in in vitro. At first-passage, EPCs were cultured at different cell densities (5 x 10(3), 1 x 10(4), 2 x 10(4) or 5 x 10(4)/cm(2)) and in basic medium (EGM, medium 199, DMEM or 1640) supplemented with FBS (2%, 5%, 10% or 20%) and different combinations of cytokines (VEGF, VEGF + bFGF, VEGF + bFGF + EGF, or VEGF + bFGF + EGF + IGF), the experiment being based on L(64) (4(21)) orthogonal design.

RESULTS AND CONCLUSIONS

This demonstrated that the optimal culture method for our EPCs displayed higher expansion and migration rates as compared to other groups, by analysis of variance; that is, cultured at 1 x 10(4)/cm(2) in M199 supplemented with 10% FBS and VEGF + bFGF + IGF + EGF. Furthermore, percentage of positive cells stained by Dil-ac-LDL and FITC-UEA-1 was more than 65%, and as shown by immunohistochemistry, these cells also stained positively for CD133, CD34 and KDR. The present study indicates that the number and function of porcine EPCs significantly increased when using our optimized culture parameters.

Enhanced progenitor cell recruitment and endothelial repair after selective endothelial injury of the mouse kidney

Primary and/or secondary injury of the renal microvascular endothelium is a common finding in various renal diseases. Besides well-known endothelial repair mechanisms, including endothelial cell (EC) proliferation and migration, homing of extrinsic cells such as endothelial progenitor cells (EPC) and hematopoietic stem cells (HSC) has been shown in various organs and may contribute to microvascular repair. However, these mechanisms have so far not been studied after selective microvascular injury in the kidney. The present study investigated the time course of EPC and HSC stimulation and homing following induction of selective EC injury in the mouse kidney along with various angiogenic factors potentially involved in EC repair and progenitor cell stimulation. Erythropoietin was used to stimulate progenitor cells in a therapeutic approach. We found that selective EC injury leads to a marked stimulation of EPCs, HSCs, and various angiogenic factors to orchestrate microvascular repair. Angiogenic factors started to increase as early as 30 min after disease induction. Progenitor cells could be first detected in the circulation and the spleen before they selectively homed to the diseased kidney. Injection of a high dose of erythropoietin 2 h after disease induction markedly attenuated vascular injury through nonhemodynamic mechanisms, possibly involving vascular endothelial growth factor release.

Bone marrow-derived endothelial progenitor cells confer renal protection in a murine chronic renal failure model

Endothelial cell damage and impaired angiogenesis substantially contribute to the progression of chronic renal failure (CRF). The effect of endothelial progenitor cell (EPC) treatment on the progression of CRF is yet to be determined. We performed 5/6 nephrectomy to induce CRF in C57BL/6 mice. EPCs were isolated from bone marrow, grown in conditioned medium, and characterized with surface marker analysis. The serial changes in kidney function and histological features were scrutinized in CRF mice and EPC-treated CRF (EPC-CRF) mice. Adoptively transferred EPCs were present at the glomeruli and the tubulointerstitial area until week 8 after transfer. In CRF mice, renal function deteriorated steadily over time, whereas the EPC-CRF group showed less deterioration of renal function as well as reduced proteinuria along with a relatively preserved kidney structure. Renal expression of proinflammatory cytokines and adhesion molecules was already decreased in the EPC-CRF group at the early stage of disease, at which point the renal function and histology of CRF and EPC-CRF mice were not different. Angiogenic molecules including VEGF, KDR, and thrombospondin-1, which were decreased in the CRF group, were restored by EPC treatment. In conclusion, EPCs trafficked into the injured kidney protected the kidney from the inflammatory condition and consequently resulted in functional and structural renal preservation. Our study suggests EPCs as a potential candidate for a novel therapeutic approach in CRF.

Histone deacetylase modulates the proinflammatory and -fibrotic changes in tubulointerstitial injury

Histone deacetylase (HDAC) regulates gene expression by modifying chromatin structure. Although changes in the expression and activities of HDAC may affect the course of kidney disease, the role of HDAC in tubulointerstitial injury has not been explored. We therefore investigated the alterations in HDAC expression and determined the effects of HDAC inhibition on the tubulointerstitial injury induced by unilateral ureteral obstruction. The induction of HDAC1 and HDAC2, accompanied by a decrease in histone acetylation was observed in kidneys injured by ureteral obstruction. Immunohistochemical analysis revealed that HDAC1 and HDAC2 were induced in renal tubular cells. Treatment with an HDAC inhibitor, trichostatin A (TSA), attenuated macrophage infiltration and fibrotic changes in tubulointerstitial injury induced by ureteral obstruction. The induction of colony-stimulating factor-1 (CSF-1), a chemokine known to be involved in macrophage infiltration in tubulointerstitial injury, was reduced in injured kidneys from mice treated with TSA. TSA, valproate, and the knockdown of HDAC1 or HDAC2 significantly reduced CSF-1 induced by TNF-alpha in renal tubular cells. These results suggest that tubular HDAC1 and HDAC2, induced in response to injury, may contribute to the induction of CSF-1 and the initiation of macrophage infiltration and profibrotic responses. These findings suggest a potential of HDAC inhibition therapy aimed at reducing inflammation and fibrosis in tubulointerstitial injury.

The role of angiopoietin-1 and thrombospondin-1 in the kidney of rats subject to 5/6 nephrectomy

The expression of angiopoietin-1 (Ang-1) and thrombospondin-1 (TSP-1) in 5/6 subtotal nephrectomy (STN) rats model, and its correlation to the renal microvasculature injury were investigated. Rat 5/6 STN model was established in adult male SD rats, and the sham-operated group and 5/6 STN group were set up. The renal function and histopathological changes were examined at the 1st, 2nd, 4th, 8th and 12th week after operation. The expression of Ang-1, TSP-1 and CD31 in renal tissues was detected by using immunohistochemistry. From 2nd to 8th week after operation, Ang-1 was significantly expressed in glomeruli of rats with STN. Ang-1 staining in glomeruli of STN group was increased significantly as compared with that in sham-operated group at 4th and 8th week after operation, and subsequently decreased after the 12th week. The expression of TSP-1 was increased significantly in STN group. As compared with sham-operated group, the CD31 expression was significantly down-regulated from the 2nd week. The expression of Ang-1 mRNA was detected by using RT-PCR at the same time points. The expression of Ang-1 mRNA in renal tissue of rats with STN was significantly up-regulated at the 2nd, 4th and 8th week after operation as compared with that in STN group at other time points or in sham-operated group at the same time points, while decreased evidently at the 12th week as compared with that in sham-operated group. It is concluded that there are changes in the mRNA expression of Ang-1, and the significant up-regulation of the expression of TSP-1 in renal tissue of rats with STN, which may be involved in the remnant renal microvasculature injury.

Synergistic effects of asymmetrical dimethyl-L-arginine accumulation and endothelial progenitor cell deficiency on renal function decline during a 2-year follow-up in stable angina

BACKGROUND

Renal insufficiency predisposes to coronary artery disease (CAD), but also CAD and traditional risk factors accelerate renal function loss. Endothelial progenitor cell (EPC) deficiency and elevated asymmetrical dimethyl-L-arginine (ADMA), an endogenous nitric oxide (NO) formation inhibitor, predict adverse CAD outcome. Our aim was to assess changes in estimated glomerular filtration rate over time (DeltaeGFR) in relation to baseline EPC blood counts and ADMA levels in stable angina.

METHODS

Eighty non-diabetic men with stable angina were followed up for 2 years after elective coronary angioplasty. Exclusion criteria included heart failure, left ventricular systolic dysfunction, eGFR <30 ml/min/1.73 m(2) and coexistent diseases. Those with cardiovascular events or ejection fraction <55% during the follow-up were also excluded. A baseline blood count of CD34+/kinase-insert domain receptor (KDR)+ cells, a leukocyte subpopulation enriched for EPC, was quantified by flow cytometry (percentage of lymphocytes).

RESULTS

A synergistic interaction (P = 0.015) between decreased CD34+/KDR+ cell counts and increased plasma ADMA, but not symmetrical dimethyl-L-arginine, was the sole significant multivariate DeltaeGFR predictor irrespective of baseline eGFR. DeltaeGFR was depressed in the simultaneous presence of high ADMA (>0.45 micromol/l, median) and low CD34+/KDR+ cell counts (<0.035%, median) compared to either of the other subgroups (P = 0.001-0.01). DeltaeGFR did not correlate with traditional risk factors, angiographic CAD extent, levels of C-reactive protein and soluble vascular cell adhesion molecule-1.

CONCLUSIONS

Elevated ADMA and EPC deficiency may synergistically contribute to accelerated renal function decline in stable angina. This could result from the impairment of the EPC-dependent endothelial renewal in the kidney, an NO-dependent process.

Angiogenesis in the kidney: a new therapeutic target?

PURPOSE OF REVIEW

The prevalence of chronic kidney disease has been growing consistently for the past decades. Renal failure is often associated with defective angiogenesis, and recognition of the contribution of the renal microcirculation to the progression of chronic renal disease may aid in the development of therapeutic interventions.

RECENT FINDINGS

Intra-renal proliferation, remodeling, and/or rarefaction of microvessels in response to injury can all aggravate nephron damage, and experimental evidence suggests that they may constitute the early steps in the complex pathways involved in progressive renal injury. Recent studies showed the benefits of targeted interventions deemed to promote neovascularization (e.g. progenitor cells, growth factors) on the ischemic myocardium and brain and in a few models of renal disease.

SUMMARY

Evidence of aberrant renal microvascular architecture in various forms of renal disease provides the impetus to attempt modulating the renal microcirculation to interfere with the disease process. Targeted interventions to preserve the renal microcirculation may not only decrease the evolving injury in renal vascular disease but also potentially constitute a coadjuvant intervention to become part of a comprehensive management plan to improve the success of parallel strategies to preserve renal function, such as revascularization.

Review article: endothelial progenitor cells in renal disease

This brief overview is intended to provide basic information about endothelial progenitors, their definition and consensus markers used for their detection, describe the pathways of their mobilization and homing and highlight the mechanisms and manifestations of their incompetence that occurs in some chronic kidney diseases. Discussion is geared towards the potential role of endothelial progenitor cells in organ regeneration, in particular, in kidney regeneration. The concept we attempted to promote attributes to the incompetence of endothelial progenitor cells in failed regeneration and ensuing progression of chronic kidney disease. This field of inquiry remains insufficiently explored, especially in renal diseases. Promising areas for future exploration are emphasized.

Decreased circulating CD34+ cells are associated with progression of diabetic nephropathy

AIMS

Circulating progenitor cells such as CD34+ cells play a key role in maintenance of vascular endothelial function and neovascularization, and a decrease in the number of CD34+ cells is associated with cardiovascular disease. However, the contribution of circulating progenitor cells to microvascular disease, such as diabetic nephropathy, is unclear. This study was therefore designed to clarify the association between diabetic nephropathy and circulating CD34+ cells.

METHODS

We measured circulating CD34+ cell numbers in 85 Type 2 diabetic patients aged 40-70 years with normo- and microalbuminuria and determined the association with urinary albumin excretion rate (UAER).

RESULTS

The number of circulating CD34+ cells significantly correlated with log UAER (r = -0.289, P = 0.008). Furthermore, in patients with low numbers of CD34+ cells (0.68 > cells/microl, lowest quartile of CD34+ cell number) UAER increased significantly after 12 months compared with baseline [from 34.3 +/- 7.0 to 53.6 +/- 10.8 mg/g creatinine (gCr), P < 0.05], whereas in patients with a high number of CD34+ cells (1.0 < cells/microl, highest quartile of CD34+ cell number) UAER did not change (from 16.7 +/- 4.8 to 20.1 +/- 3.0 mg/gCr).

CONCLUSIONS

These results suggest that a decreased number of circulating CD34+ cells is involved in the progression of diabetic nephropathy and may be a predictor of the disease.

Endothelial progenitor cells restore renal function in chronic experimental renovascular disease

BACKGROUND

Endothelial progenitor cells (EPCs) promote neovascularization and endothelial repair. Renal artery stenosis (RAS) may impair renal function by inducing intrarenal microvascular injury and remodeling. We investigated whether replenishment with EPCs would protect the renal microcirculation in chronic experimental renovascular disease.

METHODS AND RESULTS

Single-kidney hemodynamics and function were assessed with the use of multidetector computed tomography in vivo in pigs with RAS, pigs with RAS 4 weeks after intrarenal infusion of autologous EPCs, and controls. Renal microvascular remodeling and angiogenic pathways were investigated ex vivo with the use of micro-computed tomography, histology, and Western blotting. EPCs increased renal expression of angiogenic factors, stimulated proliferation and maturation of new vessels, and attenuated renal microvascular remodeling and fibrosis in RAS. Furthermore, EPCs normalized the blunted renal microvascular and filtration function.

CONCLUSIONS

The present study shows that a single intrarenal infusion of autologous EPCs preserved microvascular architecture and function and decreased microvascular remodeling in experimental chronic RAS. It is likely that restoration of the angiogenic cascade by autologous EPCs involved not only generation of new vessels but also acceleration of their maturation and stabilization. This contributed to preserving the blood supply, hemodynamics, and function of the RAS kidney, supporting EPCs as a promising therapeutic intervention for preserving the kidney in renovascular disease.