Erythropoietin delivery by genetically engineered bone marrow stromal cells for correction of anemia in mice with chronic renal failure

Kidney Mesenchymal Stem Cell-derived Extracellular Vesicles Engineered to Express Erythropoietin Improve Renal Anemia in Mice with Chronic Kidney Disease

Extracellular vesicles (EVs) shed from kidney mesenchymal stem cells (KMSCs) show protective effects against acute kidney injury and progressive kidney fibrosis via mRNA transfer. Previous studies report improvement of renal anemia following administration of genetically modified MSCs or peritoneal mesothelial cells that secrete erythropoietin (EPO). Here, we determined whether EPO-secreting KMSC-derived EVs (EPO⁽⁺⁾-EVs) can improve renal anemia in mouse models of chronic kidney disease (CKD). The mouse CKD and renal anemia model was induced by electrocoagulation of the right renal cortex and sequential left nephrectomy. At six weeks post-nephrectomy, we observed significantly lower hemoglobin (10.4 ± 0.2 vs. 13.2 ± 0.2 g/dL) and significantly higher blood urea nitrogen and serum creatinine levels in CKD mice relative to controls (60.5 ± 0.5 and 0.37 ± 0.09 mg/dL vs. 19.9 ± 0.5 and 0.12 ± 0.02 mg/dL, respectively). Genetically engineered EPO⁽⁺⁾-KMSCs secreted 71 IU/mL EPO/10⁶ cells/24 h in vitro, and EPO⁽⁺⁾-EVs isolated by differential ultracentrifugation expressed EPO mRNA and horizontally transferred EPO mRNA into target cells in vitro and in vivo. Furthermore, at two weeks post-injection of EPO⁽⁺⁾-KMSCs or EPO⁽⁺⁾-EVs into CKD mice with renal anemia, we observed significant increases in hemoglobin levels (11.7 ± 0.2 and 11.5 ± 0.2 vs. 10.1 ± 0.2 g/dL, respectively) and significantly lower serum creatinine levels at eight weeks in comparison to mice receiving vehicle control (0.30 ± 0.00 and 0.23 ± 0.03 vs. 0.43 ± 0.06 mg/dL, respectively). These results demonstrate that intraperitoneal administration of EPO⁽⁺⁾-EVs significantly increased hemoglobin levels and renal function in CKD mice, suggesting the efficacy of these genetically engineered EVs as a promising novel strategy for the treatment of renal anemia.

Microparticles derived from human erythropoietin mRNA-transfected mesenchymal stem cells inhibit epithelial-to-mesenchymal transition and ameliorate renal interstitial fibrosis

Background

Renal tubulointerstitial fibrosis (TIF) plays an important role in the progression of chronic kidney disease (CKD) and its pathogenesis involves epithelial-to-mesenchymal transition (EMT) upon renal injury. Recombinant human erythropoietin (rhEPO) has been shown to display novel cytoprotective effects, in part by inhibiting transforming growth factor (TGF)-β1-induced EMT. Here, we evaluated the inhibitory effects of microparticles (MPs) derived from human EPO gene-transfected kidney mesenchymal stem cells (hEPO-KMSCs) against TGF-β1-induced EMT in Madin-Darby canine kidney (MDCK) cells and against TIF in mouse kidneys with unilateral ureteral obstruction (UUO).

Methods

EMT was induced in MDCK cells by treatment with TGF-β1 (5 ng/mL) for 48 h and then inhibited by co-treatment with rhEPO (100 IU/mL), mock gene-transfected KMSC-derived MPs (MOCK-MPs), or hEPO-KMSC-derived MPs (hEPO-MPs) for a further 48 h. UUO was induced in FVB/N mice, which were then treated with rhEPO (1000 IU/kg, intraperitoneally, every other day for 1 week), MOCK-MPs, or hEPO-MPs (80 μg, intravenously). Alpha-smooth muscle actin (α-SMA), fibronectin, and E-cadherin expression were evaluated in MDCK cells and kidney tissues, and the extent of TIF in UUO kidneys was assessed by immunohistochemical staining.

Results

TGF-β1 treatment significantly increased α-SMA and fibronectin expression in MDCK cells and decreased that of E-cadherin, while co-treatment with rhEPO, MOCK-MPs, or hEPO-MPs markedly attenuated these changes. In addition, rhEPO and hEPO-MP treatment effectively decreased phosphorylated Smad2 and Smad3, as well as phosphorylated p38 mitogen-activated protein kinase (MAPK) expression, suggesting that rhEPO and rhEPO-MPs can inhibit TGF-β1-induced EMT via both Smad and non-Smad pathways. rhEPO and hEPO-MP treatment also significantly attenuated the extent of renal TIF after 1 week of UUO compared to MOCK-MPs, with hEPO-MPs significantly reducing myofibroblast and F4/80+ macrophage infiltration as well as EMT marker expression in UUO renal tissues in a similar manner to rhEPO.

Conclusions

Our results demonstrate that hEPO-MPs modulate TGF-β1-induced EMT in MDCK cells via the Smad2, Smad3, and p38 MAPK pathways and significantly attenuated renal TIF in UUO kidneys.

Mesenchymal stem cells as carrier of the therapeutic agent in the gene therapy of blood disorders

Nonhematopoietic stem cells as a delivery platform of therapeutic useful genes have attracted widespread attention in recent years, owing to gained a long lifespan, easy separation, high proliferation, and high transfection capacity. Mesenchymal stem/stromal cells (MSCs) are the choice of the cells for gene and cell therapy due to high self-renewal capacity, high migration rate to the site of the tumor, and with immune suppressive and anti-inflammatory properties. Hence, it has a high potential of safety genetic modification of MSCs for antitumor gene expression and has paved the way for the clinical application of these cells to target the therapy of cancers and other diseases. The aim of gene therapy is targeted treatment of cancers and diseases through recovery, change, or enhancement cell performance to the sustained secretion of useful therapeutic proteins and induction expression of the functional gene in intended tissue. Recent developments in the vectors designing leading to the increase and durability of expression and improvement of the safety of the vectors that overcome a lot of problems, such as durability of expression and the host immune response. Nowadays, gene therapy approach is used by MSCs as a delivery vehicle in the preclinical and the clinical trials for the secretion of erythropoietin, recombinant antibodies, coagulation factors, cytokines, as well as angiogenic inhibitors in many blood disorders like anemia, hemophilia, and malignancies. In this study, we critically discuss the status of gene therapy by MSCs as a delivery vehicle for the treatment of blood disorders. Finally, the results of clinical trial studies are assessed, highlighting promising advantages of this emerging technology in the clinical setting.

Treatment of renal anemia: Erythropoiesis stimulating agents and beyond

Anemia, complicating the course of chronic kidney disease, is a significant parameter, whether interpreted as subjective impairment or an objective prognostic marker. Renal anemia is predominantly due to relative erythropoietin (EPO) deficiency. EPO inhibits apoptosis of erythrocyte precursors. Studies using EPO substitution have shown that increasing hemoglobin (Hb) levels up to 10–11 g/dL is associated with clinical improvement. However, it has not been unequivocally proven that further intensification of erythropoiesis stimulating agent (ESA) therapy actually leads to a comprehensive benefit for the patient, especially as ESAs are potentially associated with increased cerebro-cardiovascular events. Recently, new developments offer interesting options not only via stimulating erythropoeisis but also by employing additional mechanisms. The inhibition of activin, a member of the transforming growth factor superfamily, has the potential to correct anemia by stimulating liberation of mature erythrocyte forms and also to mitigate disturbed mineral and bone metabolism as well. Hypoxia-inducible factor prolyl hydroxylase inhibitors also show pleiotropic effects, which are at the focus of present research and have the potential of reducing mortality. However, conventional ESAs offer an extensive body of safety evidence, against which the newer substances should be measured. Carbamylated EPO is devoid of Hb augmenting effects whilst exerting promising tissue protective properties. Additionally, the role of hepcidin antagonists is discussed. An innovative new hemodialysis blood tube system, reducing blood contact with air, conveys a totally different and innocuous option to improve renal anemia by reducing mechanical hemolysis.

EPO modified MSCs can inhibit asthmatic airway remodeling in an animal model

There was no effective measures can be obtained at present to reverse or prevent airway remodeling. We investigated the therapeutic effect of Erythropoietin (EPO) gene modified mesenchymal stem cells (MSCs) on asthmatic airway remodeling and the possible underlied molecular mechanisms. EPO gene was transfected into MSCs via lentivirus vector. The transfected cells (EPO-MSCs) were identified by flow cytometry and the EPO secreting function was detected by PCR and Western blot. MSCs or EPO-MSCs were administrated to albumin (OVA)-induced chronic asthmatic mouse model via tail veins. The asthmatic phenotype was analyzed. Number of cells in bronchoalveolar lavage fluid (BALF) was counted using a hemocytometer. Histological findings of airways were evaluated by microscopic examination. The concentrations of interleukin 4(IL-4), interleukin 5(IL-5), and interleukin 13(IL-13) in lung homogenate were determined by ELISA. The activation state of transforming growth factor-β 1 (TGF-β1), Transforming growth factor beta-activated kinase 1 (TAK1), and p38 Mitogen Activated Protein Kinase (p38MAPK) signaling was detected by Real-Time PCR and Western blotting. EPO-MSCs were successfully constructed. EPO-MSCs showed a more potently suppressive effect on local asthmatic airway inflammation and the level of IL-4, IL-5, and IL-13 in lung tissue than MSCs. Moreover, the numbers of goblet cells, the thicknesses of smooth muscle layer, collagen density, percentage of proliferating cell nuclear antigen positive (PCNA⁺ ) mesenchymal cells, and von Willebrand factor positive(vWF⁺ ) vessels were also significantly inhibited by EPO-MSCs. Furthermore, EPO-MSCs could downregulate the expression of TGF-β1, TAK1, and p38MAPK in lung tissue both in mRNA level and in protein level. EPO gene modified MSCs may more efficiently attenuate asthmatic airway remodeling, which maybe related with the downregulation of TGF-β1-TAK1-p38MAPK pathway activity.

Human CD133+ Renal Progenitor Cells Induce Erythropoietin Production and Limit Fibrosis After Acute Tubular Injury

Persistent alterations of the renal tissue due to maladaptive repair characterize the outcome of acute kidney injury (AKI), despite a clinical recovery. Acute damage may also limit the renal production of erythropoietin, with impairment of the hemopoietic response to ischemia and possible lack of its reno-protective action. We aimed to evaluate the effect of a cell therapy using human CD133⁺ renal progenitor cells on maladaptive repair and fibrosis following AKI in a model of glycerol-induced rhabdomyolysis. In parallel, we evaluated the effect of CD133⁺ cells on erythropoietin production. Administration of CD133⁺ cells promoted the restoration of the renal tissue, limiting the presence of markers of injury and pro-inflammatory molecules. In addition, it promoted angiogenesis and protected against fibrosis up to day 60. No effect of dermal fibroblasts was observed. Treatment with CD133⁺ cells, but not with PBS or fibroblasts, limited anemia and increased erythropoietin levels both in renal tissue and in circulation. Finally, CD133⁺ cells contributed to the local production of erythropoietin, as observed by detection of circulating human erythropoietin. CD133⁺ cells appear therefore an effective source for cell repair, able to restore renal functions, including erythropoietin release, and to limit long term maldifferentiation and fibrosis.

Uremic toxin p-cresol induces Akt-pathway-selective insulin resistance in bone marrow-derived mesenchymal stem cells

We reported a functional incompetence in mesenchymal stem cells (MSCs) under uremia, but the mechanisms have not been explored. To study the mechanisms of dysfunctional MSCs induced by uremia, we characterized insulin signaling in MSCs and investigated the effect of uremic toxin, p-cresol, on the proangiogenic actions of insulin. In MSCs, insulin induced hypoxia-inducible factor (HIF)-1α, vascular endothelial growth factor, and stromal cell-derived factor 1α expressions via PI3K/Akt-dependent pathway. MSCs treated with p-cresol exhibited altered insulin signaling in a selective manner for insulin receptor substrate-1/PI3K/Akt pathway, whereas ERK pathway remained active. The insulin-induced increase of HIF-1α was blunted by p-cresol treatment. This Akt-selective insulin resistance was also observed in MSCs isolated from chronic kidney disease (CKD) mice. In mice model of hindlimb ischemia, blood flow recovery, capillary density, and local production of angiogenic factors in the ischemic limb treated with CKD MSCs were significantly inferior to those promoted by control MSCs. However, modifying CKD MSCs by overexpression of HIF-1α restored all of these changes. Taken together, these data suggest that p-cresol contributes to insulin resistance in a selective manner for Akt pathway. This might be a biological explanation for the functional incompetence of MSCs under uremia through defects in the insulin-induced elevation of HIF-1α protein expression.

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

Introduction

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

Methods

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

Results

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

Conclusions

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

Electronic supplementary material

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

Mechanisms governing the health and performance benefits of exercise

Humans are considered among the greatest if not the greatest endurance land animals. Over the last 50 years, as the population has become more sedentary, rates of cardiovascular disease and its associated risk factors such as obesity, type 2 diabetes and hypertension have all increased. Aerobic fitness is considered protective for all-cause mortality, cardiovascular disease, a variety of cancers, joint disease and depression. Here, I will review the emerging mechanisms that underlie the response to exercise, focusing on the major target organ the skeletal muscle system. Understanding the mechanisms of action of exercise will allow us to develop new therapies that mimic the protective actions of exercise.

Immunotherapeutic organoids: a new approach to cancer treatment

Therapeutic monoclonal antibodies have revolutionized the treatment of cancer and other diseases. However, several limitations of antibody-based treatments, such as the cost of therapy and the achievement of sustained plasma levels, should be still addressed for their widespread use as therapeutics. The use of cell and gene transfer methods offers additional benefits by producing a continuous release of the antibody with syngenic glycosylation patterns, which makes the antibody potentially less immunogenic. In vivo secretion of therapeutic antibodies by viral vector delivery or ex vivo gene modified long-lived autologous or allogeneic human mesenchymal stem cells may advantageously replace repeated injection of clinical-grade antibodies. Gene-modified autologous mesenchymal stem cells can be delivered subcutaneously embedded in a non-immunogenic synthetic extracellular matrix-based scaffold that guarantees the survival of the cell inoculum. The scaffold would keep cells at the implantation site, with the therapeutic protein acting at distance (immunotherapeutic organoid), and could be retrieved once the therapeutic effect is fulfilled. In the present review we highlight the practical importance of living cell factories for in vivo secretion of recombinant antibodies.

Controlled regulation of erythropoietin by primary cultured renal cells for renal failure induced anemia

PURPOSE

Renal failure induced anemia develops as a result of inadequate production of erythropoietin, which is the primary regulator of red blood cell production. We previously noted that culture expanded primary renal cells stably express erythropoietin and suggested that these cells may be used as a potential treatment for renal failure induced anemia. We investigated whether these cells are able to regulate erythropoietin expression in a controlled manner under different oxygen and environmental conditions.

MATERIALS AND METHODS

Primary rat renal cells were exposed to different hypoxic (0.1% to 1% O(2)) and normoxic environments. Erythropoietin expression was assessed using reverse transcriptase-polymerase chain reaction. Erythropoietin production was measured in culture medium using Meso Scale Discovery® assays. Results were plotted to compare different levels of production to the control.

RESULTS

Cultured renal cells expressed high levels of erythropoietin under hypoxia for up to 24 hours with a gradual decrease thereafter. However, erythropoietin expression was decreased when cells were switched from a hypoxic to a normoxic environment within the initial 24 hours. This indicated that cultured renal cells have the capacity to sense environmental oxygen tension and regulate erythropoietin expression accordingly. In addition, erythropoietin release in medium followed a pattern similar to that of gene expression under normoxic and hypoxic conditions.

CONCLUSIONS

These findings indicate that primary renal cells have the ability to regulate erythropoietin gene expression and release through environment dependent mechanisms. This also suggests that with further study the possibility exists of developing these cells as a potential method to treat renal failure induced anemia.

Treating patients with schizophrenia deficit with erythropoietin?

This systematic review summarizes and critically appraises the literature on the effect of erythropoietin (EPO) in schizophrenia patients and the pathophysiological mechanisms that may explain the potential of its use in this disease. EPO is mainly known for its regulatory activity in the synthesis of erythrocytes and is frequently used in treatment of chronic anemia. This cytokine, however, has many other properties, some of which may improve the symptoms of psychiatric illness. The review follows the preferred reporting items for systematic reviews and meta-analysis (PRISMA) statement guidelines. Three databases (Medline, Web of Science, and Cochrane) were searched combining the search terms 'erythropoietin AND (psychotic disorders OR schizophrenia)'. Seventy-eight studies were included in qualitative synthesis, a meta-analytic approach being prohibited. The findings suggest that several EPO cerebral potential properties may be relevant for schizophrenia treatment, such as neurotransmission regulation, neuroprotection, modulation of inflammation, effects on blood-brain barrier permeability, effects on oxidative stress and neurogenesis. Several potentially detrimental side-effects of EPO therapy, such as increased risk of thrombosis, cancer, increased metabolic rate and mean arterial blood pressure leading to cerebral ischemia could severely limit or halt the use of EPO. Overall, because the available data are inconclusive, further efforts in this field are warranted.

Skeletal muscle alterations and exercise performance decrease in erythropoietin-deficient mice: a comparative study

BACKGROUND

Erythropoietin (EPO) is known to improve exercise performance by increasing oxygen blood transport and thus inducing a higher maximum oxygen uptake (VO2max). Furthermore, treatment with (or overexpression of) EPO induces protective effects in several tissues, including the myocardium. However, it is not known whether EPO exerts this protective effect when present at physiological levels. Given that EPO receptors have been identified in skeletal muscle, we hypothesized that EPO may have a direct, protective effect on this tissue. Thus, the objectives of the present study were to confirm a decrease in exercise performance and highlight muscle transcriptome alterations in a murine EPO functional knock-out model (the EPO-d mouse).

METHODS

We determined VO2max peak velocity and critical speed in exhaustive runs in 17 mice (9 EPO-d animals and 8 inbred controls), using treadmill enclosed in a metabolic chamber. Mice were sacrificed 24h after a last exhaustive treadmill exercise at critical speed. The tibialis anterior and soleus muscles were removed and total RNA was extracted for microarray gene expression analysis.

RESULTS

The EPO-d mice's hematocrit was about 50% lower than that of controls (p<0.05) and their performance level was about 25% lower (p<0.001). A total of 1583 genes exhibited significant changes in their expression levels. However, 68 genes were strongly up-regulated (normalized ratio>1.4) and 115 were strongly down-regulated (normalized ratio<0.80). The transcriptome data mining analysis showed that the exercise in the EPO-d mice induced muscle hypoxia, oxidative stress and proteolysis associated with energy pathway disruptions in glycolysis and mitochondrial oxidative phosphorylation.

CONCLUSIONS

Our results showed that the lack of functional EPO induced a decrease in the aerobic exercise capacity. This decrease was correlated with the hematocrit and reflecting poor oxygen supply to the muscles. The observed alterations in the muscle transcriptome suggest that physiological concentrations of EPO exert both direct and indirect muscle-protecting effects during exercise. However, the signaling pathway involved in these protective effects remains to be described in detail.

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.

A MCP1 fusokine with CCR2-specific tumoricidal activity

Background

The CCL2 chemokine is involved in promoting cancer angiogenesis, proliferation and metastasis by malignancies that express CCR2 receptor. Thus the CCL2/CCR2 axis is an attractive molecular target for anticancer drug development.

Methods

We have generated a novel fusion protein using GMCSF and an N-terminal truncated version of MCP1/CCL2 (6-76) [hereafter GMME1] and investigated its utility as a CCR2-specific tumoricidal agent.

Results

We found that distinct to full length CCL2 or its N-truncated derivative (CCL2 5-76), GMME1 bound to CCR2 on mouse lymphoma EG7, human multiple myeloma cell line U266, or murine and human medulloblastoma cell lines, and led to their death by apoptosis. We demonstrated that GMME1 specifically blocked CCR2-associated STAT3 phosphorylation and up-regulated pro-apoptotic BAX. Furthermore, GMME1 significantly inhibited EG7 tumor growth in C57BL/6 mice, and induced apoptosis of primary myeloma cells from patients.

Conclusion

Our data demonstrate that GMME1 is a fusokine with a potent, CCR2 receptor-mediated pro-apoptotic effect on tumor cells and could be exploited as a novel biological therapy for CCR2⁺ malignancies including lymphoid and central nervous system malignancies.

Erythropoietin gene-enhanced marrow mesenchymal stromal cells decrease cisplatin-induced kidney injury and improve survival of allogeneic mice

Bone marrow-derived mesenchymal stromal cells (MSCs) are promising for regenerative medicine applications, such as for renoprotection and repair in acute kidney injury (AKI). Erythropoietin (Epo) can also exert cytoprotective effects on various tissues including the kidney. We hypothesized that MSCs gene-enhanced to secrete Epo may produce a significant beneficial effect in AKI. Mouse Epo-secreting MSCs were generated, tested in vitro, and then implanted by intraperitoneal injection in allogeneic mice previously administered cisplatin to induce AKI. Epo-MSCs significantly improved survival of implanted mice as compared to controls (67% survival versus 33% with Vehicle only). Also, Epo-MSCs led to significantly better kidney function as shown by lower levels of blood urea nitrogen (72 ± 9.5 mg/dl versus 131 ± 9.20 mg/dl) and creatinine (74 ± 17 µmol/l versus 148±19.4 µmol/l). Recipient mice also showed significantly decreased amylase and alanine aminotransferase blood concentrations. Kidney sections revealed significantly less apoptotic cells and more proliferating cells. Furthermore, PCR revealed the presence of implanted cells in recipient kidneys, with Epo-MSCs leading to significantly increased expression of Epo and of phosphorylated-Akt (Ser473) (P-Akt) in these kidneys. In conclusion, our study demonstrates that Epo gene-enhanced MSCs exert significant tissue protective effects in allogeneic mice with AKI, and supports the potential use of gene-enhanced cells as universal donors in acute injury.

Uremia induces functional incompetence of bone marrow-derived stromal cells

BACKGROUND

Chronic kidney disease (CKD) is associated with increased risk for cardiovascular diseases (CVD). We hypothesized that inadequate angiogenic response in uremic patients could result from dysfunction of bone marrow-derived stromal cells [mesenchymal stem cells (MSCs)].

METHODS

We investigated whether MSCs are functionally competent in uremia induced by partial kidney ablation in C57Bl/6J mice.

RESULTS

Uremic MSCs showed decreased expression of vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR)1 and stromal cell-derived factor (SDF)-1α, increased cellular senescence, decreased proliferation, defects in migration in response to VEGF and SDF-1α and in vitro tube formation. Interestingly, the expression of fibroblast-specific protein-1 was higher in uremic MSCs. Uremia decreased hypoxia-inducible factor-1α, VEGF and VEGFR1 expression under hypoxia and Akt phosphorylation in both basal and VEGF-stimulated states. A diminished mitogenic effect on endothelial proliferation was observed in conditioned media from uremic MSCs. In addition, intravital microscopic analysis showed decreased angiogenesis in uremic MSCs.

CONCLUSION

These results clearly demonstrate the functional incompetence in MSCs under uremic conditions and may significantly contribute to the disproportionately high risk for CVD in patients with CKD.

Non-hematopoietic stem cells as factories for in vivo therapeutic protein production

As an alternative to recombinant protein administration, ex vivo gene-modified cells may provide a novel strategy for systemic delivery of therapeutic proteins. This approach has been used in preclinical and clinical studies of a plethora of pathological conditions, including anemia, hemophilia and cancer for the production of erythropoietin, coagulation factors, immunostimulatory cytokines, recombinant antibodies and angiogenesis inhibitors. Cell delivery vehicles may also be varied: autologous or allogeneic, precursor or terminally differentiated cells, with targeting properties or immobilized in immunoprotective devices. This field did not meet the expectation raised initially, mainly because of difficulties with obtaining therapeutic plasma levels and the short lifespan of producer cells that hampered clinical application. Different non-hematopoietic stem/progenitor cells have emerged as potential delivery vehicles, since they are easy to obtain, expand and transduce, and they exhibit prolonged lifespans (with mesenchymal stem cells probably being the most popular cell type, but not the only one). Special emphasis is placed on the different routes used to deliver these cellular vehicles and the controversies about their targeting abilities.

The role of multipotent marrow stromal cells (MSCs) in tissue regeneration

An extensive body of preclinical and clinical data has shown that administration of adult multipotent marrow stromal cells (MSCs) effectively ameliorates experimental and clinical conditions of many different organ systems. Differentiation into organ parenchymal cells, however, is very rare, and the main mechanism for organ protection and regeneration from different types of injury is the exertion of paracrine effects and stimulation of tissue repair. A large number of clinical trials have been conducted and are ongoing to investigate the safety and efficacy of MSCs in different organs after various types of organ injury. This article intends to give a brief overview about current applications of MSCs and mechanisms involved in organ protection and regeneration.

Human marrow-derived mesenchymal stromal cells decrease cisplatin renotoxicity in vitro and in vivo and enhance survival of mice post-intraperitoneal injection

Acute kidney injury (AKI) can occur from the toxic side-effects of chemotherapeutic agents such as cisplatin. Bone marrow-derived mesenchymal stromal cells (MSCs) have demonstrated wide therapeutic potential often due to beneficial factors they secrete. The goal of this investigation was to evaluate in vitro the effect of human MSCs (hMSCs) secretome on cisplatin-treated human kidney cells, and in vivo the consequence of hMSCs intraperitoneal (ip) implantation in mice with AKI. Our results revealed that hMSCs-conditioned media improved survival of HK-2 human proximal tubular cells exposed to cisplatin in vitro. This enhanced survival was linked to increased expression of phosphorylated Akt (Ser473) and was reduced by a VEGF-neutralizing antibody. In vivo testing of these hMSCs established that ip administration in NOD-SCID mice decreased cisplatin-induced kidney function impairment, as demonstrated by lower blood urea nitrogen levels and higher survival. In addition, blood phosphorous and amylase levels were also significantly decreased. Moreover, hMSCs reduced the plasma levels of several inflammatory cytokines/chemokines. Immunohistochemical examination of kidneys showed less apoptotic and more proliferating cells. Furthermore, PCR indicated the presence of hMSCs in mouse kidneys, which also showed enhanced expression of phosphorylated Akt. In conclusion, our study reveals that hMSCs can exert prosurvival effects on renal cells in vitro and in vivo, suggests a paracrine contribution for kidney protective abilities of hMSCs delivered ip, and supports their clinical potential in AKI.

Genetic engineering of mesenchymal stem cells and its application in human disease therapy

The use of stem cells for tissue regeneration and repair is advancing both at the bench and bedside. Stem cells isolated from bone marrow are currently being tested for their therapeutic potential in a variety of clinical conditions including cardiovascular injury, kidney failure, cancer, and neurological and bone disorders. Despite the advantages, stem cell therapy is still limited by low survival, engraftment, and homing to damage area as well as inefficiencies in differentiating into fully functional tissues. Genetic engineering of mesenchymal stem cells is being explored as a means to circumvent some of these problems. This review presents the current understanding of the use of genetically engineered mesenchymal stem cells in human disease therapy with emphasis on genetic modifications aimed to improve survival, homing, angiogenesis, and heart function after myocardial infarction. Advancements in other disease areas are also discussed.

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.

Mesenchymal stem cells for the sustained in vivo delivery of bioactive factors

Mesenchymal stem cells (MSC) are a promising tool for cell therapy, either through direct contribution to the repair of bone, tendon and cartilage or as an adjunct therapy through protein production and immune mediation. They are an attractive vehicle for cellular therapies due to a variety of cell intrinsic and environmentally responsive properties. Following transplantation, MSC are capable of systemic migration, are not prone to tumor formation, and appear to tolerize the immune response across donor mismatch. These attributes combine to allow MSC to reside in many different tissue types without disrupting the local microenvironment and, in some cases, responding to the local environment with appropriate protein secretion. We describe work done by our group and others in using human MSC for the sustained in vivo production of supraphysiological levels of cytokines for the support of cotransplanted hematopoietic stem cells and enzymes that are deficient in animal models of lysosomal storage disorders such as MPSVII. In addition, the use of MSC engineered to secrete protein products has been reviewed in several fields of tissue injury repair, including but not limited to revascularization after myocardial infarction, regeneration of intervertebral disc defects and spine therapy, repair of stroke, therapy for epilepsy, skeletal tissue repair, chondrogenesis/knee and joint repair, and neurodegenerative diseases. Genetically engineered MSC have thus proven safe and efficacious in numerous animal models of disease modification and tissue repair and are poised to be tested in human clinical trials. The potential for these interesting cells to secrete endogenous or transgene products in a sustained and long-term manner is highly promising and is discussed in the current review.

Tubular cell-enriched subpopulation of primary renal cells improves survival and augments kidney function in rodent model of chronic kidney disease

Established chronic kidney disease (CKD) may be identified by severely impaired renal filtration that ultimately leads to the need for dialysis or kidney transplant. Dialysis addresses only some of the sequelae of CKD, and a significant gap persists between patients needing transplant and available organs, providing impetus for development of new CKD treatment modalities. Some postulate that CKD develops from a progressive imbalance between tissue damage and the kidney's intrinsic repair and regeneration processes. In this study we evaluated the effect of kidney cells, delivered orthotopically by intraparenchymal injection to rodents 4-7 wk after CKD was established by two-step 5/6 renal mass reduction (NX), on the regeneration of kidney function and architecture as assessed by physiological, tissue, and molecular markers. A proof of concept for the model, cell delivery, and systemic effect was demonstrated with a heterogeneous population of renal cells (UNFX) that contained cells from all major compartments of the kidney. Tubular cells are known contributors to kidney regeneration in situ following acute injury. Initially tested as a control, a tubular cell-enriched subpopulation of UNFX (B2) surprisingly outperformed UNFX. Two independent studies (3 and 6 mo in duration) with B2 confirmed that B2 significantly extended survival and improved renal filtration (serum creatinine and blood urea nitrogen). The specificity of B2 effects was verified by direct comparison to cell-free vehicle controls and an equivalent dose of non-B2 cells. Quantitative histological evaluation of kidneys at 6 mo after treatment confirmed that B2 treatment reduced severity of kidney tissue pathology. Treatment-associated reduction of transforming growth factor (TGF)-β1, plasminogen activator inhibitor (PAI)-1, and fibronectin (FN) provided evidence that B2 cells attenuated canonical pathways of profibrotic extracellular matrix production.

Oxidative stress: Biomarkers and novel therapeutic pathways

Oxidative stress significantly impacts multiple cellular pathways that can lead to the initiation and progression of varied disorders throughout the body. It therefore becomes imperative to elucidate the components and function of novel therapeutic strategies against oxidative stress to further clinical diagnosis and care. In particular, both the growth factor and cytokine erythropoietin (EPO) and members of the mammalian forkhead transcription factors of the O class (FoxOs) may offer the greatest promise for new treatment regimens since these agents and the cellular pathways they oversee cover a range of critical functions that directly influence progenitor cell development, cell survival and degeneration, metabolism, immune function, and cancer cell invasion. Furthermore, both EPO and FoxOs function not only as therapeutic targets, but also as biomarkers of disease onset and progression, since their cellular pathways are closely linked and overlap with several unique signal transduction pathways. However, biological outcome with EPO and FoxOs may sometimes be both unexpected and undesirable that can raise caution for these agents and warrant further investigations. Here we present the exciting as well as complicated role EPO and FoxOs possess to uncover the benefits as well as the risks of these agents for cell biology and clinical care in processes that range from stem cell development to uncontrolled cellular proliferation.

New strategies for Alzheimer's disease and cognitive impairment

Approximately five million people suffer with Alzheimer's disease (AD) and more than twenty-four million people are diagnosed with AD, pre-senile dementia, and other disorders of cognitive loss worldwide. Furthermore, the annual cost per patient with AD can approach $200,000 with an annual population aggregate cost of $100 billion. Yet, complete therapeutic prevention or reversal of neurovascular injury during AD and cognitive loss is not achievable despite the current understanding of the cellular pathways that modulate nervous system injury during these disorders. As a result, identification of novel therapeutic targets for the treatment of neurovascular injury would be extremely beneficial to reduce or eliminate disability from diseases that lead to cognitive loss or impairment. Here we describe the capacity of intrinsic cellular mechanisms for the novel pathways of erythropoietin and forkhead transcription factors that may offer not only new strategies for disorders such as AD and cognitive loss, but also function as biomarkers for disease onset and progression.

Characterization of Gaucher disease bone marrow mesenchymal stromal cells reveals an altered inflammatory secretome

Gaucher disease causes pathologic skeletal changes that are not fully explained. Considering the important role of mesenchymal stromal cells (MSCs) in bone structural development and maintenance, we analyzed the cellular biochemistry of MSCs from an adult patient with Gaucher disease type 1 (N370S/L444P mutations). Gaucher MSCs possessed a low glucocerebrosidase activity and consequently had a 3-fold increase in cellular glucosylceramide. Gaucher MSCs have a typical MSC marker phenotype, normal osteocytic and adipocytic differentiation, growth, exogenous lactosylceramide trafficking, cholesterol content, lysosomal morphology, and total lysosomal content, and a marked increase in COX-2, prostaglandin E2, interleukin-8, and CCL2 production compared with normal controls. Transcriptome analysis on normal MSCs treated with the glucocerebrosidase inhibitor conduritol B epoxide showed an up-regulation of an array of inflammatory mediators, including CCL2, and other differentially regulated pathways. These cells also showed a decrease in sphingosine-1-phosphate. In conclusion, Gaucher disease MSCs display an altered secretome that could contribute to skeletal disease and immune disease manifestations in a manner distinct and additive to Gaucher macrophages themselves.

Erythropoietin, forkhead proteins, and oxidative injury: biomarkers and biology

Oxidative stress significantly impacts multiple cellular pathways that can lead to the initiation and progression of varied disorders throughout the body. It therefore becomes imperative to elucidate the components and function of novel therapeutic strategies against oxidative stress to further clinical diagnosis and care. In particular, both the growth factor and cytokine erythropoietin (EPO), and members of the mammalian forkhead transcription factors of the O class (FoxOs), may offer the greatest promise for new treatment regimens, since these agents and the cellular pathways they oversee cover a range of critical functions that directly influence progenitor cell development, cell survival and degeneration, metabolism, immune function, and cancer cell invasion. Furthermore, both EPO and FoxOs function not only as therapeutic targets, but also as biomarkers of disease onset and progression, since their cellular pathways are closely linked and overlap with several unique signal transduction pathways. Yet, EPO and FoxOs may sometimes have unexpected and undesirable effects that can raise caution for these agents and warrant further investigations. Here we present the exciting as well as the complex role that EPO and FoxOs possess to uncover the benefits as well as the risks of these agents for cell biology and clinical care in processes that range from stem cell development to uncontrolled cellular proliferation.

Mesenchymal stem cell-based therapy: a new paradigm in regenerative medicine

Mesenchymal stem cells (MSCs), adherent fibroblastoid cells, present in bone marrow and many other tissues can be easily isolated and expanded in vitro. They are capable of differentiating into different cell types such as osteoblasts, chondrocytes, adipocytes, cardiomyocytes, hepatocytes, endothelial cells and neuronal cells. Such immense plasticity coupled with their ability to modulate the activity of immune cells makes them attractive for stem cell-based therapy aimed at treating previously incurable disorders. Preclinical studies have reported successful use of MSCs for delivering therapeutic proteins and repairing defects in a variety of disease models. These studies highlighted the in vivo potential of MSCs and their ability to home to injury sites and modify the microenvironment by secreting paracrine factors to augment tissue repair. Their therapeutic applicability has been widened by genetic modification to enhance differentiation and tissue targeting, and use in tissue engineering. Clinical trials for diseases such as osteogenesis imperfecta, graft-versus-host disease and myocardial infarction have shown some promise, demonstrating the safe use of both allogeneic and autologous cells. However, lack of knowledge of MSC behaviour and responses in vitro and in vivo force the need for basic and animal studies before heading to the clinic. Contrasting reports on immunomodulatory functions and tumorigenicity along with issues such as mode of cell delivery, lack of specific marker, low survival and engraftment require urgent attention to harness the potential of MSC-based therapy in the near future.

The role of mesenchymal stem cells in the functional improvement of chronic renal failure

The most commonly used therapeutic targets in nephrology are the reduction of injury, the delay of progression, or renal replacement therapy. Many animal and human studies demonstrated the role of stem cells in repair and regenerations of kidney. Mesenchymal stem cells (MSCs) have shown to improve outcome of acute renal injury models. It is controversial whether MSCs can reduce injury following a toxic/ischemic event and delay renal failure in chronic kidney disease. We evaluated the hypothesis that the treatment with MSCs could improve renal function and attenuate injury in chronic renal failure (CRF). Sprague-Dawley female rats (8 weeks old, 182.2 +/- 7.2 g) underwent modified 5/6 nephrectomy. Rats in the MSC group received an injection of MSCs (1 x 10(6) cells) via tail vein 1 day after nephrectomy. Blood and urine samples were collected after 7 days and every month thereafter. The kidneys of rats were removed for histologic evaluation after 24-h urine collection and blood sampling. The Y-chromosome stain using fluorescent in situ hybridization was performed to verify the presence of male MSCs in the kidney of female recipients. No significant differences in blood urea nitrogen and creatinine concentration were observed between the MSC group and the untreated CRF group. However, the weight gain in the MSC group was greater than those in the CRF group after 4 months. Proteinuria in the MSC group was less than that in the CRF group over time. Y chromosome was detected in the kidney of MSC group. Although no significances were observed between these two groups, the histologic analysis suggests that MSCs have positive effect against glomerulosclerosis. These results suggest that MSCs help preserve renal function and attenuate renal injury in CRF.

Mesenchymal stromal cells ameliorate experimental autoimmune encephalomyelitis by inhibiting CD4 Th17 T cells in a CC chemokine ligand 2-dependent manner

The administration of ex vivo culture-expanded mesenchymal stromal cells (MSCs) has been shown to reverse symptomatic neuroinflammation observed in experimental autoimmune encephalomyelitis (EAE). The mechanism by which this therapeutic effect occurs remains unknown. In an effort to decipher MSC mode of action, we found that MSC conditioned medium inhibits EAE-derived CD4 T cell activation by suppressing STAT3 phosphorylation via MSC-derived CCL2. Further analysis demonstrates that the effect is dependent on MSC-driven matrix metalloproteinase proteolytic processing of CCL2 to an antagonistic derivative. We also show that antagonistic CCL2 suppresses phosphorylation of AKT and leads to a reciprocal increased phosphorylation of ERK associated with an up-regulation of B7.H1 in CD4 T cells derived from EAE mice. CD4 T cell infiltration of the spinal cord of MSC-treated group was robustly decreased along with reduced plasma levels of IL-17 and TNF-alpha levels and in vitro from restimulated splenocytes. The key role of MSC-derived CCL2 was confirmed by the observed loss of function of CCL2(-/-) MSCs in EAE mice. In summary, this is the first report of MSCs modulating EAE biology via the paracrine conversion of CCL2 from agonist to antagonist of CD4 Th17 cell function.

Design and fabrication of 3D porous scaffolds to facilitate cell-based gene therapy

Biomaterials capable of efficient gene delivery by embedded cells provide a fundamental tool for the treatment of acquired or hereditary diseases. A major obstacle is maintaining adequate nutrient and oxygen diffusion to cells within the biomaterial. In this study, we combined the solid free-form fabrication and porogen leaching techniques to fabricate three-dimensional scaffolds, with bimodal pore size distribution, for cell-based gene delivery. The objective of this study was to design micro-/macroporous scaffolds to improve cell viability and drug delivery. Murine bone marrow-derived mesenchymal stromal cells (MSCs) genetically engineered to secrete erythropoietin (EPO) were seeded onto poly-L-lactide (PLLA) scaffolds with different microporosities. Over a period of 2 weeks in culture, an increase in cell proliferation and metabolic activity was observed with increasing scaffold microporosity. The concentration of EPO detected in supernatants also increased with increasing microporosity level. Our study shows that these constructs can promote cell viability and release of therapeutic proteins, and clearly demonstrates their capacity for a dual role as scaffolds for tissue regeneration and as delivery systems for soluble gene products.

Optimizing the management of renal anemia: challenges and new opportunities

Erythropoiesis stimulating agents (ESAs) are the main tool to achieve anemia correction in CKD patients. At present six different ESAs are available: epoetin alpha, epoetin beta, epoetin omega, epoetin delta, darbepoetin alpha, and very recently CERA. From one side the patent of older ESAs have expired, and biosimilars (for the moment only of epoetin alpha) have been approved for use in Europe by the European Medicines Agency. However, a number of issues about bioequivalence and how to test it are still to be solved completely. In the mean time pharmaceutical research has kept on working, developing new ESAs and alternative strategies for stimulating erythropoiesis. In this review we present and discuss these points.

Mesenchymal stromal cells engineered to express erythropoietin induce anti-erythropoietin antibodies and anemia in allorecipients

Autologous bone marrow mesenchymal stromal cells (MSCs) have been successfully used for the delivery of erythropoietin (EPO) in murine models of anemia and myocardial infarction. For clinical applications where a transient effect would be adequate, such as myocardial infarction, the use of EPO-engineered universal donor allogeneic MSCs would be a substantial convenience. We thus investigated whether MSCs from C57BL/6 mice would permit robust transient EPO delivery in normal BALB/c allorecipients. Implantation of MSCs overexpressing murine EPO led to increases in hematocrit in syngeneic and allogeneic mice, but the latter eventually developed severe anemia due to acquired neutralizing anti-EPO antibodies. As MSCs constitutively produce the CCL2 chemokine which may behave as an adjuvant to the anti-EPO immune response, experiments were performed using EPO-engineered MSCs derived from CCL2(-/-) mice and similar results were obtained. In conclusion, MHC-mismatched MSCs can break the tolerance to autoantigens and lead to the development of pathogenic autoantibodies.

Mesenchymal stromal cells genetically engineered to overexpress IGF-I enhance cell-based gene therapy of renal failure-induced anemia

We previously demonstrated that erythropoietin (EPO)-secreting mesenchymal stromal cells (MSC) can be used for the long-term correction of renal failure-induced anemia. The present study provides evidence that coimplantation of insulin-like growth factor I (IGF-I)-overexpressing MSC (MSC-IGF) improves MSC-based gene therapy of anemia by providing paracrine support to EPO-secreting MSC (MSC-EPO) within a subcutaneous implant. IGF-I receptor RNA expression in murine MSC was demonstrated by RT-PCR. Functional protein expression was confirmed by immunoblots and MSC responsiveness to IGF-I stimulation in vitro. IGF-I was also shown to improve MSC survival following staurosporin-induced apoptosis in vitro. A cohort of C57Bl/6 mice was rendered anemic by right kidney electrocoagulation and left nephrectomy. MSC-EPO were subsequently admixed in a bovine collagen matrix and implanted, in combination with MSC-IGF or MSC null, by subcutaneous injection in renal failure mice. In mice receiving MSC-EPO coimplanted with MSC-IGF, hematocrit elevation was greater and enhanced compared with control mice; heart function was also improved. MSC-IGF coimplantation, therefore, represents a promising new strategy for enhancing MSC survival within implanted matrices and for improving cell-based gene therapy of renal anemia.

Erythropoietin: elucidating new cellular targets that broaden therapeutic strategies

Given that erythropoietin (EPO) is no longer believed to have exclusive biological activity in the hematopoietic system, EPO is now considered to have applicability in a variety of nervous system disorders that can overlap with vascular disease, metabolic impairments, and immune system function. As a result, EPO may offer efficacy for a broad number of disorders that involve Alzheimer's disease, cardiac insufficiency, stroke, trauma, and diabetic complications. During a number of clinical conditions, EPO is robust and can prevent metabolic compromise, neuronal and vascular degeneration, and inflammatory cell activation. Yet, use of EPO is not without its considerations especially in light of frequent concerns that may compromise clinical care. Recent work has elucidated a number of novel cellular pathways governed by EPO that can open new avenues to avert deleterious effects of this agent and offer previously unrecognized perspectives for therapeutic strategies. Obtaining greater insight into the role of EPO in the nervous system and elucidating its unique cellular pathways may provide greater cellular viability not only in the nervous system but also throughout the body.

Erythropoietin and oxidative stress

Unmitigated oxidative stress can lead to diminished cellular longevity, accelerated aging, and accumulated toxic effects for an organism. Current investigations further suggest the significant disadvantages that can occur with cellular oxidative stress that can lead to clinical disability in a number of disorders, such as myocardial infarction, dementia, stroke, and diabetes. New therapeutic strategies are therefore sought that can be directed toward ameliorating the toxic effects of oxidative stress. Here we discuss the exciting potential of the growth factor and cytokine erythropoietin for the treatment of diseases such as cardiac ischemia, vascular injury, neurodegeneration, and diabetes through the modulation of cellular oxidative stress. Erythropoietin controls a variety of signal transduction pathways during oxidative stress that can involve Janus-tyrosine kinase 2, protein kinase B, signal transducer and activator of transcription pathways, Wnt proteins, mammalian forkhead transcription factors, caspases, and nuclear factor kappaB. Yet, the biological effects of erythropoietin may not always be beneficial and may be poor tolerated in a number of clinical scenarios, necessitating further basic and clinical investigations that emphasize the elucidation of the signal transduction pathways controlled by erythropoietin to direct both successful and safe clinical care.

Raves and risks for erythropoietin

Global use of erythropoietin (EPO) continues to increase as a proven agent for the treatment of anemia. Yet, EPO is no longer believed to have exclusive biological activity in the hematopoietic system and is now considered applicable for a variety of disorders such as diabetes, Alzheimer's disease, and cardiovascular disease. Treatment with EPO is considered to be robust and can prevent metabolic compromise, neuronal and vascular degeneration, and inflammatory cell activation. On the converse side, observations that EPO administration is not without risk have fueled controversy. Here we present recent advances that have elucidated a number of novel cellular pathways governed by EPO to open new therapeutic avenues for this agent and avert its potential deleterious effects.

Retroviral modification of mesenchymal stem cells for gene therapy of hemophilia

Mesenchymal stem cells (MSCs) are a promising target for the delivery of secreted proteins due to their ease of isolation, expansion, and genetic modification. The bleeding disorder hemophilia A results from the deficiency of a secreted blood clotting factor termed factor VIII (fVIII). Hemophilia A could be cured by gene-transfer-based procedures targeting virtually any cell type, including MSCs. Here, we describe methods for retroviral modification of MSCs incorporating a high-expression porcine (HEP)-fVIII transgene and a murine model of hemophilia A. MSCs were isolated from bone marrow of hemophilia A mice, expanded, and transduced ex vivo. Genetically modified MSCs secreted high levels of HEP-fVIII into the conditioned medium. HEP-fVIII was purified from the conditioned medium and demonstrated to have a specific activity, relative electrophoretic mobility, and proteolytic activation pattern similar to HEP-fVIII produced by other commercial cell lines. Collectively, these data support the concept that MSCs can be utilized as a cellular vehicle for successful gene-transfer-based therapy of hemophilia A and other disorders resulting from the deficiency of a secreted protein.

New alternatives for erythropoietin therapy in chronic renal failure

Erythropoietin (EPO) is one of the main cytokines involved in the regulation of erythropoiesis. The main site of EPO production are the kidneys. An altered EPO production leads to pathological conditions such as anemia and polycythaemia. Due to the progressive loss of renal peritubular cells, patients with chronic kidney disease (CKD) have low EPO plasma levels. This decreases erythron stimulation with the direct consequence of developing anemia. Before the introduction in the clinical practice of rHuEpo, in the late 1980s, the only solution for treating this type of anemia were blood transfusions and anabolic steroids. Even rHuEpo has proven to be safe and effective for treatment of anemias, there are some concerns about its cost, the need for frequent parenteral administration, and development of anti-EPO antibodies. These inconveniences prompted the search for novel erythropoiesis stimulating agents. Different strategies lead to isolation or chemical synthesis of such agents as darbepoetin alfa and EPO mimetics. In this review, we present some general aspects of EPO biology, with emphasis on chronic renal failure, and expose some of the alternatives to EPO used for anemia correction.