Differentiation of human mesenchymal stem cells into mesangial cells in post-glomerular injury murine model

Muscle-Derived Stem/Progenitor Cells Ameliorate Acute Kidney Injury in Rats through the Anti-Apoptotic Pathway and Demonstrate Comparable Effects to Bone Marrow Mesenchymal Stem Cells

Background and Objectives: To date, the therapeutic potential of skeletal muscle-derived stem/progenitor cells (MDSPCs) for acute kidney injury (AKI) has only been evaluated by our research group. We aimed to compare MDSPCs with bone marrow mesenchymal stem cells (BM-MSCs) and evaluate their feasibility for the treatment of AKI. Materials and Methods: Rats were randomly assigned to four study groups: control, GM (gentamicin) group, GM+MDSPCs, and GM+BM-MSCs. AKI was induced by gentamicin (80 mg/kg/day; i.p.) for 7 consecutive days. MDSPCs and BM-MSCs were injected 24 h after the last gentamicin injection. Kidney parameters were determined on days 0, 8, 14, 21, and 35. Results: MDSPCs and BM-MSCs accelerated functional kidney recovery, as reflected by significantly lower serum creatinine levels and renal injury score, higher urinary creatinine and creatinine clearance levels (p < 0.05), lower TUNEL-positive cell number, and decreased KIM-1 and NGAL secretion in comparison to the non-treated AKI group. There was no significant difference in any parameters between the MDSPCs and BM-MSCs groups (p > 0.05). Conclusions: MDSPCs and BM-MSCs can migrate and incorporate into injured renal tissue, resulting in a beneficial impact on functional and morphological kidney recovery, which is likely mediated by the secretion of paracrine factors and an anti-apoptotic effect. MDSPCs were found to be non-inferior to BM-MSCs and therefore can be considered as a potential candidate strategy for the treatment of AKI.

Secretome profile of TNF-α-induced human umbilical cord mesenchymal stem cells unveils biological processes relevant to skin wound healing

Aim: To profile and study the proteins responsible for the beneficial effect of the TNF-α-induced human umbilical cord mesenchymal stem cells (hUCMSCs) secretome in wound healing. Methods: The hUCMSCs secretome was generated with (induced) or without (uninduced) TNF-α and was subsequently analyzed by liquid chromatography-mass spectrometry, immunoassay and in vitro scratch assay. Results: Proteomic analysis revealed approximately 260 proteins, including 51 and 55 unique proteins in the induced and uninduced secretomes, respectively. Gene ontology analysis disclosed that differential proteins in the induced secretome mainly involved inflammation-related terms. The induced secretome, consisting of higher levels of FGFb, VEGF, PDGF and IL-6, significantly accelerated wound closure and enhanced MMP-13 secretion in HaCaT keratinocytes. Conclusion: The secretome from induced hUCMSCs includes factors that promote wound closure.

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.

Current advances of stem cell-based therapy for kidney diseases

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

The effects of intravenous infusion of autologous mesenchymal stromal cells in patients with subacute middle cerebral artery infarct: a phase 2 randomized controlled trial on safety, tolerability and efficacy

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are characterized by paracrine and immunomodulatory functions capable of changing the microenvironment of damaged brain tissue toward a more regenerative and less inflammatory milieu. The authors conducted a phase 2, single-center, assessor-blinded randomized controlled trial to investigate the safety and efficacy of intravenous autologous bone marrow-derived MSCs (BMMSCs) in patients with subacute middle cerebral artery (MCA) infarct.

METHODS

Patients aged 30-75 years who had severe ischemic stroke (National Institutes of Health Stroke Scale [NIHSS] score of 10-35) involving the MCA territory were recruited within 2 months of stroke onset. Using permuted block randomization, patients were assigned to receive 2 million BMMSCs per kilogram of body weight (treatment group) or standard medical care (control group). The primary outcomes were the NIHSS, modified Rankin Scale (mRS), Barthel Index (BI) and total infarct volume on brain magnetic resonance imaging (MRI) at 12 months. All outcome assessments were performed by blinded assessors. Per protocol, analyses were performed for between-group comparisons.

RESULTS

Seventeen patients were recruited. Nine were assigned to the treatment group, and eight were controls. All patients were severely disabled following their MCA infarct (median mRS = 4.0 [4.0-5.0], BI = 5.0 [5.0-25.0], NIHSS = 16.0 [11.5-21.0]). The baseline infarct volume on the MRI was larger in the treatment group (median, 71.7 [30.5-101.7] mL versus 26.7 [12.9-75.3] mL, P = 0.10). There were no between-group differences in median NIHSS score (7.0 versus 6.0, P = 0.96), mRS (2.0 versus 3.0, P = 0.38) or BI (95.0 versus 67.5, P = 0.33) at 12 months. At 12 months, there was significant improvement in absolute change in median infarct volume, but not in total infarct volume, from baseline in the treatment group (P = 0.027). No treatment-related adverse effects occurred in the BMMSC group.

CONCLUSIONS

Intravenous infusion of BMMSCs in patients with subacute MCA infarct was safe and well tolerated. Although there was no neurological recovery or functional outcome improvement at 12 months, there was improvement in absolute change in median infarct volume in the treatment group. Larger, well-designed studies are warranted to confirm this and the efficacy of BMMSCs in ischemic stroke.

Ultrasound enhances the therapeutic potential of mesenchymal stem cells wrapped in greater omentum for aristolochic acid nephropathy

Background

Mesenchymal stem cells (MSCs) have been reported to promote regeneration in both subjects with acute kidney injury (AKI) and chronic kidney disease (CKD), but their efficacy remains limited, probably because most of the cells accumulate in the lungs, liver, and spleen after an intravenous infusion. Therefore, ultrasound-guided administration of MSCs represents a possible approach to solve this problem. The greater omentum is used to promote cell survival due to its rich vasculature. We hypothesized that ultrasound-guided administration of MSCs combined with greater omentum might be more curative than currently available approaches.

Methods

In this study, we established an aristolochic acid nephropathy (AAN) model by intraperitoneally administering aristolochic acid I sodium salt (AA-I) at a dose of 5 mg/kg body weight on alternate days for 4 weeks. Subsequently, a laparotomy was performed, and the left kidney from which the capsule had been removed was wrapped with the greater omentum. A dose of 2 × 10⁷ MSCs was injected into the space between the greater omentum and the left kidney. Equal amounts of MSCs were administered under ultrasound guidance every second week for a total of 4 treatments. Mice were sacrificed 4 weeks after surgery. Serum creatinine and blood urea levels were measured to assess renal function. qPCR, Western blot, and histological analyses were conducted to further investigate the therapeutic mechanism of MSCs.

Results

Ultrasound-guided injection of MSCs into the greater omentum that surrounds the kidney enriched cells in the kidney region for up to 5 days. Renal function tests indicated that MSCs improved renal function to a great extent, as reflected by decreased blood urea nitrogen and serum creatinine levels. In addition, histological analyses showed that MSCs noticeably attenuated kidney injury, as evidenced by the amelioration of tubular necrosis and peritubular interstitial fibrosis. Mitigation of renal interstitial fibrosis was further confirmed by immunohistochemistry, qPCR, and western blotting after MSC treatment. Moreover, immunofluorescence staining revealed that MSCs alleviated inflammatory responses by increasing the counts of CD206+ cells and decreasing the counts of CD68+ cells. MSC migration was initiated in response to AA-I-treated renal epithelial cells in an in vitro migration assay.

Conclusions

These findings suggested that administration of MSCs into the cavity formed by the injured kidney and the greater omentum under ultrasound guidance improved renal function, attenuated kidney injury, and mitigated renal interstitial fibrosis and inflammatory responses. Thus, this approach might be a safe and effective therapy for CKD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02243-7.

CDK9 inhibition improves diabetic nephropathy by reducing inflammation in the kidneys

Diabetic nephropathy (DN) is a chronic inflammatory renal disease induced by hyperglycemia. Recent studies have implicated cyclin-dependent kinase 9 (CDK9) in inflammatory responses and renal fibrosis. In this study, we explored a potential role of CDK9 in DN by using cultured mouse mesangial cell line SV40 MES-13 and streptozotocin-induced type 1 mouse model of diabetes. We inhibited CDK9 in mice and in cultured cells by a highly selective CDK9 inhibitor, LDC000067 (LDC), and evaluated inflammatory and fibrogenic outcome by mRNA and protein analyses. Our studies show that treatment of diabetic mice with LDC significantly inhibits the levels of inflammatory cytokines and fibrogenic genes in kidney specimens. These reductions were associated with improved renal function. We also found that LDC treatment suppressed MAPK-AP1 activation. We then confirmed the involvement of CDK9 in cultured SV40 MES-13 cells and showed that deficiency in CDK9 prevents glucose-induced inflammatory and fibrogenic proteins. This protection was also afforded by suppression of MAPK-AP1. Taken together, our results how that hyperglycemia activates CDK9-MAPK-AP1 axis in kidneys to induce inflammation and fibrosis, leading to renal dysfunction. Our findings also suggest that CDK9 may serve as a potential therapeutic target for DN.

Synergistic effects of intracoronary infusion of autologous bone marrow-derived mesenchymal stem cells and revascularization procedure on improvement of cardiac function in patients with severe ischemic cardiomyopathy

Background

Ischemic cardiomyopathy (ICM) is a leading cause of cardiovascular mortality worldwide. It is defined as abnormal enlargement of the left ventricular (LV) cavity with poor LV function due to coronary artery disease. Currently available established treatments are palliative whereby blood supply is recovered to ischemic regions but fails to regenerate heart tissues. Mesenchymal stem cells (MSCs) offer a promising treatment for ICM given their regenerative and multipotent characteristics. This study aims to investigate the effect of MSCs infusion with concurrent revascularization in patients with severe ICM compared to receiving only revascularization procedure or MSCs infusion.

Methods

Twenty-seven patients with history of anterior myocardial infarction (MI) and baseline left ventricular ejection fraction (LVEF) of less than 35% were recruited into this study. Patients who are eligible for revascularization were grouped into group A (MSCs infusion with concurrent revascularization) or group B (revascularization only) while patients who were not eligible for revascularization were allocated in group C to receive intracoronary MSCs infusion. LV function was measured using echocardiography.

Results

Patients who received MSCs infusion (either with or without revascularization) demonstrated significant LVEF improvements at 3, 6 and 12 months post-infusion when compared to baseline LVEF within its own group. When comparing the groups, the magnitude of change in LVEF from baseline for third visits i.e., 12 months post-infusion was significant for patients who received MSCs infusion plus concurrent revascularization in comparison to patients who only had the revascularization procedure.

Conclusions

MSCs infusion significantly improves LV function in ICM patients. MSCs infusion plus concurrent revascularization procedure worked synergistically to improve cardiac function in patients with severe ICM.

Understanding Mesangial Pathobiology in AL-Amyloidosis and Monoclonal Ig Light Chain Deposition Disease

Patients with plasma cell dyscrasias produce free abnormal monoclonal Ig light chains that circulate in the blood stream. Some of them, termed glomerulopathic light chains, interact with the mesangial cells and trigger, in a manner dependent of their structural and physicochemical properties, a sequence of pathological events that results in either light chain–derived (AL) amyloidosis (AL-Am) or light chain deposition disease (LCDD). The mesangial cells play a key role in the pathogenesis of both diseases. The interaction with the pathogenic light chain elicits specific cellular processes, which include apoptosis, phenotype transformation, and secretion of extracellular matrix components and metalloproteinases. Monoclonal light chains associated with AL-Am but not those producing LCDD are avidly endocytosed by mesangial cells and delivered to the mature lysosomal compartment where amyloid fibrils are formed. Light chains from patients with LCDD exert their pathogenic signaling effect at the cell surface of mesangial cells. These events are generic mesangial responses to a variety of adverse stimuli, and they are similar to those characterizing other more frequent glomerulopathies responsible for many cases of end-stage renal disease. The pathophysiologic events that have been elucidated allow to propose future therapeutic approaches aimed at preventing, stopping, ameliorating, or reversing the adverse effects resulting from the interactions between glomerulopathic light chains and mesangium.

Decoding the differentiation of mesenchymal stem cells into mesangial cells at the transcriptomic level

Background

Mesangial cells play an important role in the glomerulus to provide mechanical support and maintaine efficient ultrafiltration of renal plasma. Loss of mesangial cells due to pathologic conditions may lead to impaired renal function. Mesenchymal stem cells (MSC) can differentiate into many cell types, including mesangial cells. However transcriptomic profiling during MSC differentiation into mesangial cells had not been studied yet. The aim of this study is to examine the pattern of transcriptomic changes during MSC differentiation into mesangial cells, to understand the involvement of transcription factor (TF) along the differentiation process, and finally to elucidate the relationship among TF-TF and TF-key gene or biomarkers during the differentiation of MSC into mesangial cells.

Results

Several ascending and descending monotonic key genes were identified by Monotonic Feature Selector. The identified descending monotonic key genes are related to stemness or regulation of cell cycle while ascending monotonic key genes are associated with the functions of mesangial cells. The TFs were arranged in a co-expression network in order of time by Time-Ordered Gene Co-expression Network (TO-GCN) analysis. TO-GCN analysis can classify the differentiation process into three stages: differentiation preparation, differentiation initiation and maturation. Furthermore, it can also explore TF-TF-key genes regulatory relationships in the muscle contraction process.

Conclusions

A systematic analysis for transcriptomic profiling of MSC differentiation into mesangial cells has been established. Key genes or biomarkers, TFs and pathways involved in differentiation of MSC-mesangial cells have been identified and the related biological implications have been discussed. Finally, we further elucidated for the first time the three main stages of mesangial cell differentiation, and the regulatory relationships between TF-TF-key genes involved in the muscle contraction process. Through this study, we have increased fundamental understanding of the gene transcripts during the differentiation of MSC into mesangial cells.

Role of mesenchymal stem cells and their culture medium in alleviating kidney injury in rats diabetic nephropathy

Background

Diabetic nephropathy (DN) is considered as one of the most serious complications resulting from diabetes mellitus and end-stage of renal failure globally. Up to 40% of diabetic patients will develop DN. The involvement of mesenchymal stem cells (MSCs) in diabetic renal lesions management has been established in many animal models of DN. The aim is to evaluate the capability of MSCs and their culture medium (CM) to alleviate DN in streptozotocin (STZ)-induced diabetic rat model. Female albino rats were made diabetic and were further categorized into 4 subgroups of 15 each: DN group, DN group received fibroblasts, MSCs group received one dose of 1 × 106 cells of MSCs, and CM group received one dose of 500 μl of CM. In all groups, the treatment was delivered by intravenous injection (IV) into the tail vein.

Results

MSCs insinuated themselves into the injured kidney as detected by CD44 expression. Biochemical and histological results showed that MSCs and/or CM effectively attenuated DN manifestations in rat model through their possible anti-inflammatory (tumor necrosis factor-α and transforming growth factor-β1 were decreased), anti-apoptotic (Bcl2 was increased while Bax and caspases were decreased), and anti-oxidant role (malondialdehyde was decreased while glutathione and catalase were increased).

Conclusion

These results provide a potential therapeutic tool for DN management through the administration of the CM from MSCs that ameliorates the effects of diabetes. It is also possible to treat DN using CM alone thus avoiding cell transplantation.

Phenotypic plasticity of mesenchymal stem cells is crucial for mesangial repair in a model of immunoglobulin light chain-associated mesangial damage

Mesangiopathies produced by glomerulopathic monoclonal immunoglobulin light chains (GLCs) acting on the glomerular mesangium produce two characteristic lesions: AL-amyloidosis (AL-Am) and light chain deposition disease (LCDD). In both cases, the pathology is centered in the mesangium, where initial and progressive damage occurs. In AL-Am the mesangial matrix is destroyed and replaced by amyloid fibrils and in LCDD, the mesangial matrix is increased and remodeled. The collagen IV rich matrix is replaced by tenascin. In both conditions, mesangial cells (MCs) become apoptotic as a direct effect of the GLCs. MCs were incubated in-vitro with GLCs and animal kidneys were perfused ex-vivo via the renal artery with GLCs, producing expected lesions, and then mesenchymal stem cells (MSCs) were added to both platforms. Each of the two platforms provided unique information that when put together created a comprehensive evaluation of the processes involved. A "cocktail" with growth and differentiating factors was used to study its effect on mesangial repair. MSCs displayed remarkable phenotypic plasticity during the repair process. The first role of the MSCs after migrating to the affected areas was to dispose of the amyloid fibrils (in AL-Am), the altered mesangial matrix (in LCDD) and apoptotic MCs/debris. To accomplish this task, MSCs transformed into facultative macrophages acquiring an abundance of lysosomes and endocytotic capabilities required to engage in phagocytic functions. Once the mesangial cleaning was completed, MSCs transformed into functional MCs restoring the mesangium to normal. "Cocktail" made the repair process more efficient.

Renal lineage cells as a source for renal regeneration

The mammalian kidney is a highly complex organ, composed of various cell types within a unique structural framework. Nonetheless, in recent years, giant leaps in our understanding of nephrogenesis and the origin of new cells in the adult kidney have resulted in novel routes to regenerate damaged nephrons. While several strategies can be envisioned to achieve this aim, one common theme is the reliance on renal lineage cells, as extrarenal cells, such as bone marrow-derived cells, have been shown to be devoid of renal differentiation capacity. Herein, we will present the main motivation for the pursuit for cell-based therapies, which is the ever growing problem of chronic kidney disease (CKD), and discuss different strategies toward replenishing the damaged renal parenchyma. These include transplantation of fetal kidney grafts or fetal kidney stem cells, directed differentiation of pluripotent stem cells into kidney epithelia, establishment of renal progenitors from the adult kidney, and genetic reprogramming of mature kidney cells into a progenitor state. Taken together with novel techniques recapitulating the three-dimensional developmental environment, these advances are expected to take the field into a new era, bringing us closer than ever to the day when kidney stem cell-based therapy becomes a viable therapeutic option.

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

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

Exosomes secreted from bone marrow-derived mesenchymal stem cells protect the intestines from experimental necrotizing enterocolitis

PURPOSE

Treatment options for necrotizing enterocolitis (NEC) remain inadequate. Bone marrow-derived mesenchymal stem cells (BM-MSCs) can protect the intestines from NEC. Exosomes are nanoparticle-sized vesicles with important cell signaling capabilities. The objective of this study was to determine whether BM-MSC-derived exosomes can prevent NEC.

METHODS

Rat pups were either breast fed (Group 1) or subjected to experimental NEC and randomized to receive either no treatment (Group 2) or an intraperitoneal (IP) injection of PBS (Group 3), BM-MSC (Group 4), or BM-MSC-derived exosomes (Group 5). Histologic injury grade and intestinal permeability were determined. The effect of BM-MSC-derived exosomes on IEC-6 intestinal epithelial cells in an in vitro scrape model of wound healing was also determined.

RESULTS

Animals exposed to NEC that were either untreated or received PBS alone had an NEC incidence of 46% and 41%, respectively (p=0.61). Compared to untreated pups, the incidence of NEC was significantly lower in pups treated with either BM-MSC (9%, p=0.0003) or MB-MSC-derived exosomes (13%, p=0.0008). Similar results were found for intestinal permeability. Wound healing in IEC-6 cells was significantly increased by BM-MSC-derived exosomes.

CONCLUSION

BM-MSC-derived exosomes protect the intestines from NEC and may represent a novel, cell-free, preventative therapy for NEC in the future.

Adult stem cells as a tool for kidney regeneration

Kidney regeneration is a challenging but promising strategy aimed at reducing the progression to end-stage renal disease (ESRD) and improving the quality of life of patients with ESRD. Adult stem cells are multipotent stem cells that reside in various tissues, such as bone marrow and adipose tissue. Although intensive studies to isolate kidney stem/progenitor cells from the adult kidney have been performed, it remains controversial whether stem/progenitor cells actually exist in the mammalian adult kidney. The efficacy of mesenchymal stem cells (MSCs) in the recovery of kidney function has been demonstrated in animal nephropathy models, such as acute tubular injury, glomerulonephritis, renal artery stenosis, and remnant kidney. However, their beneficial effects seem to be mediated largely via their paracrine effects rather than their direct differentiation into renal parenchymal cells. MSCs not only secrete bioactive molecules directly into the circulation, but they also release various molecules, such as proteins, mRNA, and microRNA, in membrane-covered vesicles. A detailed analysis of these molecules and an exploration of the optimal combination of these molecules will enable the treatment of patients with kidney disease without using stem cells. Another option for the treatment of patients with kidney disease using adult somatic cells is a direct/indirect reprogramming of adult somatic cells into kidney stem/progenitor cells. Although many hurdles still need to be overcome, this strategy will enable bona fide kidney regeneration rather than kidney repair using remnant renal parenchymal cells.

Inducible glomerular erythropoietin production in the adult kidney

Hypoxia-inducible factor (HIF)-2-triggered erythropoietin production in renal interstitial fibroblast-like cells is the physiologically relevant source of erythropoietin for regulating erythropoiesis. During renal fibrosis, these cells transform into myofibroblasts and lose their ability to produce sufficient erythropoietin leading to anemia. To find if other cells for erythropoietin production might exist in the kidney we tested for the capability of nonepithelial glomerular cells to elaborate erythropoietin. Therefore, HIF transcription factors were stabilized by cell-specific deletion of the von Hippel-Lindau (VHL) gene. Inducible deletion of VHL in glomerular connexin40-expressing cells (endothelial, renin-expressing, and mesangial cells) markedly increased glomerular erythropoietin mRNA expression levels, plasma erythropoietin concentrations, and hematocrit values. These changes were mimicked by inducible cell-specific VHL deletion in renin-expressing and in mesangial cells but not in endothelial cells. The increases of erythropoietin production were absent, when VHL was co-deleted with HIF-2. The induction of glomerular erythropoietin expression was associated with the downregulation of juxtaglomerular renin expression, again in a HIF-2-dependent manner. Thus, VHL deletion in renin-expressing and in mesangial cells induces the capability to produce relevant amounts of erythropoietin and to suppress renin expression in the adult kidney if HIF-2 is stabilized.

The role of the microenvironment on the fate of adult stem cells

Adult stem cells (SCs) exist in all tissues that promote tissue growth, regeneration, and healing throughout life. The SC niche in which they reside provides signals that direct them to proliferate, differentiate, or remain dormant; these factors include neighboring cells, the extracellular matrix, soluble molecules, and physical stimuli. In disease and aging states, stable or transitory changes in the microenvironment can directly cause SC activation or inhibition in tissue healing as well as functional regulation. Here, we discuss the microenvironmental regulation of the behavior of SC and focus on plasticity approaches by which various environmental factors can enhance the function of SCs and more effectively direct the fate of SCs.

BAFF promotes proliferation of human mesangial cells through interaction with BAFF-R

Background

B cell activating factor belonging to the TNF family (BAFF) is vital for B cell survival, proliferation and activation. Evidence indicates that BAFF is systemically or locally increased in glomerulonephritis (e.g. lupus nephritis, IgA nephropathy). However, the effect of BAFF on human mesangial cells is not known.

Methods

The impact of BAFF on the proliferation of a human mesangial cell line in vitro was investigated. The expression of BAFF receptor (BAFF-R) and downstream signal transduction were explored. The influence of BAFF on the expression of related genes was also studied.

Results

Our data indicated that BAFF had a proliferative effect on human mesangial cells, as supported by the results of cell proliferation assays and the inhibited expression of the pro-apoptotic gene Bim. BAFF-R was expressed on the cell membrane of human mesangial cells and blockade of BAFF/BAFF-R binding abrogated the proliferative effect of BAFF on human mesangial cells. BAFF stimulation led to rapid phosphorylation of NF-κBp65, Akt and MAPK p38 kinase in human mesangial cells, whereas it had no effect on the expression of NF-κB p100 and phosphorylation of Erk. The phosphorylation of Akt was very sensitive to blockade of BAFF/BAFF-R ligation, although activation of MAPK p38 and NF-κBp65 was not. BAFF treatment resulted in decreased expression of BAFF-R, which implied negative feedback regulation after its binding.

Conclusions

BAFF promoted proliferation of human mesangial cells, which was mediated via BAFF-R. The BAFF/BAFF-R interaction triggered Akt, p65 and p38 activation, with Akt phosphorylation being tightly dependent on BAFF/BAFF-R interaction.

Matrix metalloproteinase-9 expression is enhanced in renal parietal epithelial cells of zucker diabetic Fatty rats and is induced by albumin in in vitro primary parietal cell culture

As a subfamily of matrix metalloproteinases (MMPs), gelatinases including MMP-2 and MMP-9 play an important role in remodeling and homeostasis of the extracellular matrix. However, conflicting results have been reported regarding their expression level and activity in the diabetic kidney. This study investigated whether and how MMP-9 expression and activity were changed in glomerular epithelial cells upon albumin overload. In situ zymography, immunostaining and Western blot for renal MMP gelatinolytic activity and MMP-9 protein expression were performed in Zucker lean and Zucker diabetic rats. Confocal microscopy revealed a focal increase in gelatinase activity and MMP-9 protein in the glomeruli of diabetic rats. Increased glomerular MMP-9 staining was mainly observed in hyperplastic parietal epithelial cells (PECs) expressing claudin-1 in the diabetic kidneys. Interestingly, increased parietal MMP-9 was often accompanied by decreased staining for podocyte markers (nephrin and podocalyxin) in the sclerotic area of affected glomeruli in diabetic rats. Additionally, urinary excretion of podocyte marker proteins was significantly increased in association with the levels of MMP-9 and albumin in the urine of diabetic animals. To evaluate the direct effect of albumin on expression and activity of MMP-9, primary cultured rat glomerular PECs were incubated with rat serum albumin (0.25 - 1 mg/ml) for 24 - 48 hrs. MMP-9 mRNA levels were significantly increased following albumin treatment. Meanwhile, albumin administration resulted in a dose-dependent increase in MMP-9 protein and activity in culture supernatants of PECs. Moreover, albumin activated p44/42 mitogen-activated protein kinase (MAPK) in PECs. Inhibition of p44/42 MAPK suppressed albumin-induced MMP-9 secretion from glomerular PECs. Taken together, we have demonstrated that an up-regulation of MMP-9 in activated parietal epithelium is associated with a loss of adjacent podocytes in progressive diabetic nephropathy. Albumin overload may induce MMP-9 expression and secretion by PECs via the activation of p44/42 MAPK pathway.

Role of Mesenchymal Stem Cells Transfected With Vascular Endothelial Growth Factor in Maintaining Renal Structure and Function in Rats with Unilateral Ureteral Obstruction

OBJECTIVES

Mesenchymal stem cells hold promise for renal disease treatment. Vascular endothelial growth factor may heal tubule-interstitial fibrosis in unilateral ureteral obstruction by inhibiting epithelial-mesenchymal transition. We investigated the protective effect of vascular endothelial growth factor in transfected mesenchymal stem cells in unilateral ureteral obstruction-induced renal injury in rats.

MATERIALS AND METHODS

Male Wistar Albino rats (32 rats; weight, 250-300 g) were divided into 4 equal groups: group 1, control; group 2, unilateral ureteral obstruction; group 3, unilateral ureteral obstruction and mesenchymal stem cells; and group 4, unilateral ureteral obstruction and vascular endothelial growth factor-transfected mesenchymal stem cells. Vascular endothelial growth factor-transfected mesenchymal stem cells were administered intravenously before onset of unilateral ureteral obstruction. On day 14, the rats were killed and kidneys were retrieved. Tubular necrosis, mononuclear cell infiltration, and interstitial fibrosis were evaluated in paraffin blocks. We evaluated green fluorescent protein-positive and vascular endothelial growth factor-positive cells; anti-inflammatory (Prostaglandin E2 receptor) and interleukin 1 receptor antagonist), proinflammatory/anti-inflammatory (interleukin 6), and proinflammatory (MPO) cytokine expression levels; and levels of nitric oxide; transforming growth factor β1, E-cadherin, and hydroxyproline.

RESULTS

Green fluorescent protein-positive cells were negative in the renal parenchyma in groups 1 and 2 and positive in groups 3 and 4. Vascular endothelial growth factor levels were significantly higher in group 4. Transforming growth factor β1, nitric oxide, and E-cadherin levels were significantly higher in the unilateral ureteral obstruction than control group; however, in the study groups, these values were not significantly different from the unilateral ureteral obstruction group. In stem cell-transplanted tissue samples, EP3, interleukin 1 receptor antagonist, and interleukin 6 levels were elevated, but MPO expression levels were low. Although there were significant differences for tubular necrosis and fibrosis in group 2, there were significant reductions in tubular injury and fibrosis in groups 3 and 4.

CONCLUSIONS

Systemic stem cells transplanted into the kidney protected against unilateral ureteral obstruction-induced renal epithelial-mesenchymal transition and renal fibrosis.

Kidney stem cells in development, regeneration and cancer

The generation of nephrons during development depends on differentiation via a mesenchymal to epithelial transition (MET) of self-renewing, tissue-specific stem cells confined to a specific anatomic niche of the nephrogenic cortex. These cells may transform to generate oncogenic stem cells and drive pediatric renal cancer. Once nephron epithelia are formed the view of post-MET tissue renal growth and maintenance by adult tissue-specific epithelial stem cells becomes controversial. Recently, genetic lineage tracing that followed clonal evolution of single kidney cells showed that the need for new cells is constantly driven by fate-restricted unipotent clonal expansions in varying kidney segments arguing against a multipotent adult stem cell model. Lineage-restriction was similarly maintained in kidney organoids grown in culture. Importantly, kidney cells in which Wnt was activated were traced to give significant clonal progeny indicating a clonogenic hierarchy. In vivo nephron epithelia may be endowed with the capacity akin to that of unipotent epithelial stem/progenitor such that under specific stimuli can clonally expand/self renew by local proliferation of mature differentiated cells. Finding ways to ex vivo preserve and expand the observed in vivo kidney-forming capacity inherent to both the fetal and adult kidneys is crucial for taking renal regenerative medicine forward. Some of the strategies used to achieve this are sorting human fetal nephron stem/progenitor cells, growing adult nephrospheres or reprogramming differentiated kidney cells toward expandable renal progenitors.

HB-EGF augments the ability of mesenchymal stem cells to attenuate intestinal injury

BACKGROUND

We have previously demonstrated that heparin-binding EGF-like growth factor (HB-EGF) and mesenchymal stem cell (MSC) administration protect the intestines from ischemia/reperfusion (I/R) injury in vivo, with amniotic fluid-derived MSC (AF-MSC) being more efficacious than bone marrow-derived MSC (BM-MSC). The goal of the current study was to determine whether the protective effects of HB-EGF were from direct effects on MSC or via alternative mechanisms.

METHODS

Murine MSC were transfected with an HB-EGF plasmid or control plasmid by electroporation. Mice were subjected to segmental intestinal I/R injury and received either BM-MSC or AF-MSC either with or without exogenous HB-EGF, or BM-MSC or AF-MSC that endogenously over-expressed HB-EGF. MSC engraftment, intestinal histologic injury, and intestinal permeability were quantified.

RESULTS

There was increased MSC engraftment into injured compared to uninjured intestine. HB-EGF increased AF-MSC engraftment into injured intestine. Administration of HB-EGF and MSC improved intestinal histology and intestinal permeability after I/R injury, with AF-MSC being most efficacious. The effect of HB-EGF on MSC was similar when the growth factor was administered exogenously, or when it was overexpressed endogenously.

CONCLUSIONS

The effect of HB-EGF on AF-MSC was similar with both exogenous administration and endogenous overexpression of the growth factor, implying that HB-EGF has a direct effect on AF-MSC. This information may assist in guiding potential future AF-MSC-based therapies for patients at risk of intestinal ischemic injuries.

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.

Effect of stem cells on renal recovery in rat model of partial unilateral upper ureteric obstruction

BACKGROUND

Untreated obstructive uropathy produces irreversible renal damage and is an important cause of pediatric renal insufficiency. This study was designed to evaluate the effects of stem cell injection on morphological and pathological changes in the rat kidneys with partial unilateral upper ureteric obstruction (PUUUO).

METHODS

Wistar rats (n = 30) were operated upon to create a PUUUO by the psoas hitch method and were randomized into Group I (control, n = 15) and Group II (stem cell, n = 15); at day 5, 10 and 15, a subgroup of rats (n = 5) from each group was killed and the kidneys harvested. Pathological and morphological changes in the harvested kidneys were studied and compared between the two groups.

RESULTS

Morphologically, at day 15, Group II had significantly (p = 0.04) greater cortical thickness (0.48 ± 0.17 vs. 0.38 ± 0.09 mm). Histologically, at day 5, Group II had significantly (p = 0.032) lower peri-pelvic fibrosis. Group II group showed greater peri-pelvic inflammation as compared to Group I (p = 0.05). At day 10, lower grades of peri-pelvic fibrosis (p = 0.08), interstitial fibrosis (p = 0.037) and tubular atrophy (p = 0.05) were seen in the Group II. At day 15, Group II demonstrated significantly lower parenchymal loss (p = 0.037), glomerulosclerosis (p = 0.08), interstitial fibrosis (p = 0.08), tubular atrophy (p = 0.08) and peri-pelvic fibrosis (p = 0.08).

CONCLUSIONS

In a rat model of PUUUO, stem cell injection prevented detrimental changes in renal pathology and preserved renal parenchymal mass.

In vitro differentiation of mesenchymal stem cells into mesangial cells when co-cultured with injured mesangial cells

Mesangial cells are one of the three major cell types of the kidney glomerulus that provide physical support for the glomerular capillary lumen of the kidney. Loss of mesangial cells due to pathologic conditions, such as glomerulonephritis and diabetic nephropathy, can impair renal function. Mesenchymal stem cells (MSC) are attractive candidates for kidney repair therapy since they can enhance recovery and protect against kidney failure. MSC can differentiate into mesangial cells in vivo. We have investigated the ability of MSC to differentiate into mesangial cells in vitro; they were co-cultured with oxidant-injured mesangial cells before being analysed by flow cytometry and for contractility. MSC co-cultured with injured mesangial cells had a mesangial cell-like morphology and contracted in response to angiotensin II. They expressed CD54(-) CD62E(+) in direct contrast to the CD54(+) CD62E(-) of pure MSC. In conclusion, MSC can differentiate into mesangial cells in vitro when co-cultured with injured mesangial cells.

Synergistic effects of HB-EGF and mesenchymal stem cells in a murine model of intestinal ischemia/reperfusion injury

BACKGROUND

We have previously demonstrated that heparin-binding EGF-like growth factor (HB-EGF) administration protects the intestines from ischemia/reperfusion (I/R) injury in vivo. We have also shown that HB-EGF promotes mesenchymal stem cell (MSC) proliferation and migration in vitro. The goals of the current study were to examine the effects of HB-EGF and both bone marrow (BM)- and amniotic fluid (AF)-derived MSC on intestinal I/R injury in vivo.

MATERIALS AND METHODS

MSC were isolated from pan-EGFP mice, expanded, and purified. Pluripotency was confirmed by induced differentiation. Mice were subjected to terminal ileum I/R and received either: (1) no therapy; (2) HB-EGF; (3) BM-MSC; (4) HB-EGF+BM-MSC; (5) AF-MSC; or (6) HB-EGF+AF-MSC. MSC engraftment, histologic injury, and intestinal permeability were quantified.

RESULTS

There was increased MSC engraftment into injured compared to uninjured intestine for all experimental groups, with significantly increased engraftment for AF-MSC+HB-EGF compared to AF-MSC alone. Administration of HB-EGF and MSC improved intestinal histology and intestinal permeability after I/R injury. The greatest improvement was with combined administration of HB-EGF+AF-MSC.

CONCLUSIONS

Both HB-EGF alone and MSC alone can protect the intestines from I/R injury, with synergistic efficacy occurring when HB-EGF and AF-MSC are administered together.

Stem cell recruitment after injury: lessons for regenerative medicine

Tissue repair and regeneration are thought to involve resident cell proliferation as well as the selective recruitment of circulating stem and progenitor cell populations through complex signaling cascades. Many of these recruited cells originate from the bone marrow, and specific subpopulations of bone marrow cells have been isolated and used to augment adult tissue regeneration in preclinical models. Clinical studies of cell-based therapies have reported mixed results, however, and a variety of approaches to enhance the regenerative capacity of stem cell therapies are being developed based on emerging insights into the mechanisms of progenitor cell biology and recruitment following injury. This article discusses the function and mechanisms of recruitment of important bone marrow-derived stem and progenitor cell populations following injury, as well as the emerging therapeutic applications targeting these cells.

Do mesenchymal stem cells function across species barriers? Relevance for xenotransplantation

BACKGROUND

Allogeneic mesenchymal stem (stromal) cells (MSC) are a promising therapy for various pathological conditions. Genetically modified pig MSC have been demonstrated to downregulate the human T-cell response to pig antigens in vitro. Before genetically modified pig MSC can be used clinically, however, evidence needs to be provided to indicate whether they will survive in a human (xenogeneic) host.

LITERATURE SEARCH AND RESULTS

A literature search through the end of 2011 identified 94 reports of the in vivo cross-species administration of MSC in a variety of experimental models. The majority (n = 89) involved the use of human MSC in various other species, with an occasional study using pig, rat, or guinea-pig MSC. When human MSC were used, they were largely derived from the bone marrow, adipose tissue, or umbilical cord blood. The routes of administration were varied, although almost half of the studies utilized the intravenous route. In 88 experiments (93.6%), there was evidence that the MSC engrafted and functioned across the species barrier, and in only six cases (6.4%) was there evidence of failure to function. Importantly, MSC function was confirmed in several different cross-species models. For example, human MSC functioned in no fewer than seven different recipient species.

CONCLUSIONS

The data provided by this literature search strengthen the hypothesis that pig MSC will function satisfactorily in a different species, for example, humans. The data also suggest that our own in vitro observations on the efficacy of pig MSC in downregulating the strength of the human T-cell response to pig antigens will likely be reproduced in vivo in pre-clinical large animal models and in clinical trials.

Stem cell transplantation increases antioxidant effects in diabetic mice

Intra bone marrow-bone marrow transplantation (IBM- BMT) + thymus transplantation (TT) has been shown to reduce the incidence of graft versus host disease (GVHD) and restore donor-derived T cell function. In addition, an increase in insulin sensitivity occurred in db/db mice after IBM-BMT+TT treatment. Heme oxygenase (HO)-1 is a stress inducible enzyme which exert antioxidant, antiapoptotic, and immune-modulating properties. We examined whether IBM-BMT+TT could modulate the expression of HO-1 in the kidneys of db/db mice. Six-week-old db/db mice with blood glucose levels higher than 250 mg/dl were treated with IBM-BMT+TT. Six weeks later, the db/db mice showed decreased body weight, blood glucose levels and insulin, and increased plasma adiponectin levels. The upregulation of HO-1 was associated with significantly (p<0.05) increased levels of peNOS and pAKT, but decreased levels of iNOS in the kidneys of db/db mice. Plasma creatinine levels also decreased (p<0.05), and the expression of type IV collagen was improved. Thus IBM-BMT+TT unregulated the expression of HO-1, peNOS and pAKT, while decreasing iNOS levels in the kidney of db/db mice. This was associated with an improvement in renal function.

Heparin-binding epidermal growth factor-like growth factor and mesenchymal stem cells act synergistically to prevent experimental necrotizing enterocolitis

BACKGROUND

We have shown that administration of heparin-binding EGF (epidermal growth factor)-like growth factor (HB-EGF) protects the intestines from experimental necrotizing enterocolitis (NEC). We have also demonstrated that systemically administered mesenchymal stem cells (MSC) can engraft into injured intestines. This study investigated the effects of HB-EGF on MSC in vitro, and whether MSC and HB-EGF can act synergistically to prevent NEC in vivo.

STUDY DESIGN

In vitro, the effect of HB-EGF on MSC proliferation, migration, and apoptosis was determined. In vivo, rat pups received MSC either intraperitoneally (IP) or intravenously (IV). Pups were assigned to 1 of 7 groups: Group 1, breast-fed; Group 2, experimental NEC; Group 3, NEC+HB-EGF; Group 4, NEC+MSC IP; Group 5, NEC+HB-EGF+MSC IP; Group 6, NEC+MSC IV; or Group 7, NEC+HB-EGF+MSC IV. Mesechymal stem cell engraftment, histologic injury, intestinal permeability, and mortality were determined.

RESULTS

Heparin-binding EGF-like growth factor promoted MSC proliferation and migration, and decreased MSC apoptosis in vitro. In vivo, MSC administered IV had increased engraftment into NEC-injured intestine compared with MSC administered IP (p < 0.05). Heparin binding EGF-like growth factor increased engraftment of IP-administered MSC (p < 0.01) and IV-administered MSC (p < 0.05). Pups in Groups 3 to 7 had a decreased incidence of NEC compared with nontreated pups (Group 2), with the lowest incidence in pups treated with HB-EGF+MSC IV (p < 0.01). Pups in Group 7 had a significantly decreased incidence of intestinal dilation and perforation, and had the lowest intestinal permeability, compared with other treatment groups (p < 0.01). Pups in all experimental groups had significantly improved survival compared with pups exposed to NEC, with the best survival in Group 7 (p < 0.05).

CONCLUSIONS

Heparin-binding EGF-like growth factor and MSC act synergistically to reduce injury and improve survival in experimental NEC.

Mesenchymal stromal cells in renal ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury is an inevitable consequence of organ transplantation and a major determinant of patient and graft survival in kidney transplantation. Renal I/R injury can lead to fibrosis and graft failure. Although the exact sequence of events in the pathophysiology of I/R injury remains unknown, the role of inflammation has become increasingly clear. In this perspective, mesenchymal stromal cells (MSCs) are under extensive investigation as potential therapy for I/R injury, since MSCs are able to exert immune regulatory and reparative effects. Various preclinical studies indicate the beneficial effects of MSCs in ameliorating renal injury and accelerating tissue repair. These versatile cells have been shown to migrate to sites of injury and to enhance repair by paracrine mechanisms instead of by differentiating and replacing the injured cells. The first phase I studies of MSCs in human renal I/R injury and kidney transplantation have been started, and results are awaited soon. In this review, preliminary results and opportunities of MSCs in human renal I/R injury are summarized. We might be heading towards a cell-based paradigm shift in the treatment of renal I/R injury.

Human mesenchymal stromal cells could deliver erythropoietin and migrate to the basal layer of hair shaft when subcutaneously implanted in a murine model

Mesenchymal stromal cells (MSC) are an attractive cell-targeting vehicle for gene delivery. MIDGE (an acronym for Minimalistic, Immunologically Defined Gene Expression) construct is relatively safer than the viral or plasmid expression system as the detrimental eukaryotic and prokaryotic gene and sequences have been eliminated. The objective of this study was to test the ability of the human MSC (hMSC) to deliver the erythropoietin (EPO) gene in a nude mice model following nucleofection using a MIDGE construct. hMSC nucleofected with MIDGE encoding the EPO gene was injected subcutaneously in Matrigel at the dorsal flank of nude mice. Subcutaneous implantation of nucleofected hMSC resulted in increased hemoglobin level with presence of human EPO in the peripheral blood of the injected nude mice in the first two weeks post-implantation compared with the control groups. The basal layer of the hair shaft in the dermal layer was found to be significantly positive for immunohistochemical staining of a human EPO antibody. However, only a few basal layers of the hair shaft were found to be positively stained for CD105. In conclusion, hMSC harboring MIDGE-EPO could deliver and transiently express the EPO gene in the nude mice model. These cells could be localized to the hair follicle and secreted EPO protein might have possible role in hair regeneration.

Extended and stable gene expression via nucleofection of MIDGE construct into adult human marrow mesenchymal stromal cells

Human mesenchymal stromal cell (hMSC) is a potential target for cell and gene therapy-based approaches against a variety of different diseases. Whilst cationic lipofection has been widely experimented, the Nucleofector technology is a relatively new non-viral transfection method designed for primary cells and hard-to-transfect cell lines. Herein, we compared the efficiency and viability of nucleofection with cationic lipofection, and used the more efficient transfection method, nucleofection, to deliver a construct of minimalistic, immunologically defined gene expression encoding the erythropoietin (MIDGE-EPO) into hMSC. MIDGE construct is relatively safer than the viral and plasmid expression systems as the detrimental eukaryotic and prokaryotic gene and sequences have been eliminated. Using a plasmid encoding the luciferase gene, we demonstrated a high transfection efficiency using the U-23 (21.79 ± 1.09%) and C-17 (5.62 ± 1.09%) pulsing program in nucleofection. The cell viabilities were (44.93 ± 10.10)% and (21.93 ± 5.72)%, respectively 24 h post-nucleofection. On the other hand, lipofection treatment only yielded less than 0.6% efficiencies despite showing higher viabilities. Nucleofection did not affect hMSC renewability, immunophenotype and differentiation potentials. Subsequently, we nucleofected MIDGE-EPO using the U-23 pulsing program into hMSC. The results showed that, despite a low nucleofection efficiency with this construct, the EPO protein was stably expressed in the nucleofected cells up to 55 days when determined by ELISA or immunocytochemical staining. In conclusion, nucleofection is an efficient non-viral transfection approach for hMSC, which when used in conjunction with a MIDGE construct, could result in extended and stable transgene expression in hMSC.

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

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

Regenerative medicine of the kidney

End stage renal disease is a major health problem in this country and worldwide. Although dialysis and kidney transplantation are currently used to treat this condition, kidney regeneration resulting in complete healing would be a desirable alternative. In this review we focus our attention on current therapeutic approaches used clinically to delay the onset of kidney failure. In addition we describe novel approaches, like Tissue Engineering, Stem cell Applications, Gene Therapy, and Renal Replacement Therapy that may one day be possible alternative therapies for patients with the hope of delaying kidney failure or even stopping the progression of renal disease.

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

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

Mesenchymal stem cells in renal function recovery after acute kidney injury: use of a differentiating agent in a rat model

Acute kidney injury (AKI) is a major health care condition with limited current treatment options. Within this context, stem cells may provide a clinical approach for AKI. Moreover, a synthetic compound previously developed, hyaluronan monoesters with butyric acid (HB), able to induce metanephric differentiation, formation of capillary-like structures, and secretion of angiogenic cytokines, was tested in vitro. Thereafter, we investigated the effects of human mesenchymal stem cells from fetal membranes (FMhMSCs), both treated and untreated with HB, after induction of ischemic AKI in a rat model. At reperfusion following 45-min clamping of renal pedicles, each rat was randomly assigned to one of four groups: CTR, PBS, MSC, and MSC-HB. Renal function at 1, 3, 5, and 7 days was assessed. Histological samples were analyzed by light and electron microscopy and renal injury was graded. Cytokine analysis on serum samples was performed. FMhMSCs induced an accelerated renal functional recovery, demonstrated by biochemical parameters and confirmed by histology showing that histopathological alterations associated with ischemic injury were less severe in cell-treated kidneys. HB-treated rats showed a minor degree of inflammation, both at cytokine and TEM analyses. Better functional and morphological recovery were not associated to stem cells' regenerative processes, but possibly suggest paracrine effects on microenvironment that induce retrieval of renal damaged tissues. These results suggest that FMhMSCs could be useful in the treatment of AKI and the utilization of synthetic compounds could enhance the recovery induction ability of cells.

Arterially delivered mesenchymal stem cells prevent obstruction-induced renal fibrosis

BACKGROUND

Mesenchymal stem cells (MSCs) hold promise for the treatment of renal disease. While MSCs have been shown to accelerate recovery and prevent acute renal failure in multiple disease models, the effect of MSC therapy on chronic obstruction-induced renal fibrosis has not previously been evaluated.

MATERIALS AND METHODS

Male Sprague-Dawley rats underwent renal artery injection of vehicle or fluorescent-labeled human bone marrow-derived MSCs immediately prior to sham operation or induction of left ureteral obstruction (UUO). One or 4 wk later, the kidneys were harvested and the renal cortex analyzed for evidence of stem cell infiltration, epithelial-mesenchymal transition (EMT) as evidenced by E-cadherin/α-smooth muscle actin (α-SMA) expression and fibroblast specific protein (FSP+) staining, renal fibrosis (collagen content, Masson's trichrome staining), and cytokine and growth factor activity (ELISA and real time RT-PCR).

RESULTS

Fluorescent-labeled MSCs were detected in the interstitium of the kidney up to 4 wk post-obstruction. Arterially delivered MSCs significantly reduced obstruction-induced α-SMA expression, FSP+ cell accumulation, total collagen content, and tubulointerstitial fibrosis, while simultaneously preserving E-cadherin expression, suggesting that MSCs prevent obstruction-induced EMT and renal fibrosis. Exogenous MSCs reduced obstruction-induced tumor necrosis factor-α (TNF-α) levels, but did not alter transforming growth factor-β1 (TGF-β1), vascular endothelial growth factor (VEGF), interleukin-10 (IL-10), fibroblast growth factor (FGF), or hepatocyte growth factor (HGF) expression.

CONCLUSIONS

Human bone marrow-derived MSCs remain viable several weeks after delivery into the kidney and provide protection against obstruction-induced EMT and chronic renal fibrosis. While the mechanism of MSCs-induced renal protection during obstruction remains unclear, our results demonstrate that alterations in TNF-α production may be involved.

Cellular maintenance and repair of the kidney

The mammalian kidney is a highly complex organ that requires the precise structural arrangement of multiple cell types for effective function. The need to filter large volumes of plasma at the glomerulus followed by active reabsorption of nearly 99% of that filtrate by the tubules creates vulnerability in both compartments for cell injury. Thus maintenance of cell viability and replacement of those cells that are lost are essential for functional stability of the kidney. This review addresses our current understanding of how cells from the glomerular, tubular, and interstitial compartments arise during development and the manner in which they may be regenerated in the adult organ. In addition, we discuss the data regarding the role of organ-specific and bone marrow-derived stem and progenitor cells in the replacement/repair process, as well as the potential for ex vivo programming of stem cells toward a renal lineage.

Paracrine/endocrine mechanism of stem cells on kidney repair: role of microvesicle-mediated transfer of genetic information

PURPOSE OF REVIEW

The mechanism of stem cell-induced kidney repair remains controversial. Engraftment of bone marrow-derived stem cells is considered a rare event and several studies point to paracrine/endocrine processes. This review focuses on microvesicle-mediated transfer of genetic information between stem cells and injured tissue as a paracrine/endocrine mechanism.

RECENT FINDINGS

The following findings support a bidirectional exchange of genetic information between stem and injured cells: microvesicles shuttle defined patterns of mRNA and microRNA, are actively released from embryonic and adult stem cells and are internalized by a receptor-mediated mechanism in target cells; transcripts delivered by microvesicles from injured cells may reprogram the phenotype of stem cells to acquire specific features of the tissue; transcripts delivered by microvesicles from stem cells may induce dedifferentiation of cells surviving injury with cell cycle reentry and tissue self-repair.

SUMMARY

Transfer of genetic information from injured cells may explain stem cell functional and phenotypic changes without the need for transdifferentiation into tissue cells. On the contrary, transfer of genetic information from stem cells may redirect altered functions in target cells suggesting that stem cells may repair damaged tissues without directly replacing parenchymal cells.

Mesenchymal stem cells derived from human umbilical cord ameliorate ischemia/reperfusion-induced acute renal failure in rats

Mesenchymal stem cells (MSCs) are candidates for cell therapy of kidney diseases. However, the application of MSC derived from human umbilical cord (UC-MSC) in treating acute renal failure (ARF) has not been reported. UC-MSCs, 10(6), were transplantated via the left carotid artery into ARF rats which was established by clamping bilateral pedicles for 60 min and reperfusing. Serum creatinine and urea nitrogen decreased 4.8 times and 3.6 times as well as caspase-3 and IL-1beta decreased 5.8 times and 9 times compared to control groups, respectively. The percent of proliferative cell nuclear antigen (PCNA)-positive cells (53% +/- 7.5%) was higher than that in the control groups (17% +/- 4.5%). In addition, the transplanted UC-MSCs could reside in local injury sites, leading to the relief of hyperemia and inflammation, but no obvious transdifferentiation into renal-like cells. The results lay the foundation for further study on the potential application of UC-MSC in human disease.