Bone marrow-derived mesenchymal stem cells for treatment of heart failure: is it all paracrine actions and immunomodulation?

Bone marrow mesenchymal stem cells-derived exosomal lncRNA GAS5 mitigates heart failure by inhibiting UL3/Hippo pathway-mediated ferroptosis

BACKGROUND

Exosomes (Exos) are involved in the therapeutic effects of bone marrow mesenchymal stem cells (BMSCs) on heart failure (HF). We investigated the molecular mechanisms underlying the involvement of BMSC-Exos in ferroptosis on HF.

METHODS

A rat model of HF and cellular model of hypoxia were established. BMSC-Exos were injected into model rats or co-cultured with model cells. In model rats, the cardiac function (echocardiography), oxidative stress (commercial kits), pathological damage (HE staining), fibrosis (MASSON staining), iron deposition (Prussian blue staining), and cell apoptosis (TUNEL staining) were examined. Viability (cell counting kit-8; CCK-8), cell cycle (flow cytometry), oxidative stress, and Fe2+ levels were detected in the model cells. GAS5, UL3, YAP, and TAZ expression were detected using qRT-PCR, western blotting, and immunohistochemistry analyses.

RESULTS

BMSC-Exos restored cardiac function and inhibited oxidative stress, apoptosis, pathological damage, fibrosis, and iron deposition in myocardial tissues of HF rats. In hypoxic cells, BMSC-Exos increased cell viability, decreased the number of G1 phase cells, decreased Fe2+ levels, and inhibited oxidative stress. Ferrostatin-1 (a ferroptosis inhibitor) exhibited a synergistic effect with BMSC-Exos. Additionally, GAS5 was upregulated in BMSC-Exos, further upregulating its target UL3 and Hippo pathway effectors (YAP and TAZ). The relieving effects of BMSC-Exos on HF or hypoxia-induced injury were enhanced by GAS5 overexpression, but weakened by UL3 silencing or verteporfin (a YAP inhibitor).

CONCLUSIONS

GAS5-harbouring BMSC-Exos inhibited ferroptosis by regulating the UL3/Hippo pathway, contributing to HF remission in vivo and in vitro.

The Myocardial Microenvironment Modulates the Biology of Transplanted Mesenchymal Stem Cells

PURPOSE

The maximal efficacy of cell therapy depends on the survival of stem cells, as well as on the phenotypic and biologic changes that may occur on these cells after transplantation. It has been hypothesized that the post-ischemic myocardial microenvironment can play a critical role in these changes, potentially affecting the survival and reparative potential of mesenchymal stem cells (MSCs). Here, we use a dual reporter gene sensor for the in vivo monitoring of the phenotype of MSCs and study their therapeutic effect on cardiac function.

PROCEDURES

The mitochondrial sensor was tested in cell culture in response to different mitochondrial stressors. For in vivo testing, MSCs (3 × 10⁵) were delivered in a murine ischemia-reperfusion (IR) model. Bioluminescence imaging was used to assess the mitochondrial biology and the viability of transplanted MSCs, while high-resolution ultrasound provided a non-invasive analysis of cardiac contractility and dyssynchrony.

RESULTS

The mitochondrial sensor showed increased activity in response to mitochondrial stressors. Furthermore, when tested in the living subject, it showed a significant increase in mitochondrial dysfunction in MSCs delivered in IR, compared with those delivered under sham conditions. Importantly, MSCs delivered to ischemic hearts, despite their mitochondrial stress and poor survival, were able to induce a significant improvement in cardiac function, through decreased collagen deposition and resynchronization/contractility of left ventricular wall motion.

CONCLUSIONS

The ischemic myocardium induces changes in the phenotype of transplanted MSCs. Despite their limited survival, MSCs still elicit a certain therapeutic response, as evidenced by improvement in myocardial remodeling and cardiac function. Maximization of the survival and reparative efficacy of stem cells remains a key for the success of stem cell therapies.

Therapeutic effects of mesenchymal stem cells on cutaneous leishmaniasis lesions caused by Leishmania major

OBJECTIVES

Leishmania major (L. major) is a cutaneous leishmaniasis causative agent. Current chemotherapeutic methods are not totally effective in treatment of this disease. The immunomodulation and tissue repairing capability of mesenchymal stem cells (MSCs), ease of isolation, detection and in vitro culture, have encouraged biologists to use MSCs for cell therapy in different infections such as cutaneous leishmaniasis.

METHODS

BALB/c mice (6-8 weeks old) were infected with L. major then divided into four groups and treated with MSCs, Glucantime, Glucantime + MSCs, or PBS. Regression of lesions, potency of macrophages for phagocytosis, proliferation of immune cells against Leishmania soluble antigen, reduction of spleen parasite burden and healing of the lesions were evaluated on days 10, 20 and 30 of treatment.

RESULTS

The results indicated that the mice intralesionally injected with MSCs showed significant regression in the lesions produced by L. major by day 30. Proliferation of splenocytes stimulated with SLA (soluble leishmania antigen) in vitro in MSC-treated mice on day 20 was significantly higher than in the other groups. The potency of phagocytosis in macrophages of mice treated with MSCs was significantly higher by day 30 and healing of the lesions in this group of mice showed more progress on histopathological examinations. Spleen parasite burden showed significant reduction in the mice treated with Glucantime + MSCs by day 30.

CONCLUSIONS

The results showed that including MSCs in treatment of cutaneous leishmaniasis caused by L. major is a promising approach.

Acute aerobic exercise increases exogenously infused bone marrow cell retention in the heart

Stem cell therapy for myocardial infarction (MI) has been shown to improve cardiac function and reduce infarct size. Exercise training, in the form of cardiac rehabilitation, is an essential part of patient care post-MI. Hence, we tested the effects of acute and chronic aerobic exercise on stem cell retention and cardiac remodeling post-MI. Small epicardial MI's were induced in 12-month-old C57BL/6 mice via cryoinjury. Two weeks post-MI, vehicle infusion (N = 4) or GFP(+) bone marrow-derived cells (BMC) were injected (tail vein I.V.) immediately after acute exercise (N = 14) or sedentary conditions (N = 14). A subset of mice continued a 5-week intervention of chronic treadmill exercise (10-13 m/min; 45 min/day; 4 days/week; N = 7) or remained sedentary (N = 6). Exercise tolerance was assessed using a graded exercise test, and cardiac function was assessed with echocardiography. Acute exercise increased GFP(+) BMC retention in the infarcted zone of the heart by 30% versus sedentary (P < 0.05). This was not associated with alterations in myocardial function or gene expression of key cell adhesion molecules. Animals treated with chronic exercise increased exercise capacity (P < 0.05) and cardiac mass (P < 0.05) without change in left ventricular ejection fraction (LVEF), infarct size, or regional wall thickness (P = NS) compared with sedentary. While BMC's alone did not affect exercise capacity, they increased LVEF (P < 0.05) and Ki67(+) nuclei number in the border zone of the heart (P < 0.05), which was potentiated with chronic exercise training (P < 0.05). We conclude that acute exercise increases BMC retention in infarcted hearts and chronic training increases exogenous BMC-mediated effects on stimulating the cardiomyocyte cell cycle. These preclinical results suggest that exercise may help to optimize stem cell therapeutics following MI.

Functional properties of bone marrow derived multipotent mesenchymal stromal cells are altered in heart failure patients, and could be corrected by adjustment of expansion strategies

BACKGROUND

Bone marrow multipotent mesenchymal stromal cells (BM-MMSC) considered as a prospective substrate for cell therapy applications, however adult stem cells could be affected by donor-specific factors: age, gender, medical history. Our aim was to investigate how HF affects the functional properties of BM-MMSC.

MATERIALS AND METHODS

BM-MMSC from 10 healthy donors (HD), and 16 donors with chronic HF were evaluated for proliferative activity, ability to differentiate, replicative senescence, expression of genes that affect regeneration and fibrosis. The effect of culturing conditions on efficiency of BM-MMSC expansion was determined.

RESULTS

HF-derived BM-MMSC demonstrated early decrease of proliferative activity and upregulation of genes that control both, regeneration and fibrosis: Tgf-β pathway, synthesis of ECM, remodeling enzymes, adhesion molecules. We assume that these effects were related to increase of frequency of myofibroblast-like CD146+/SMAα+ CFU-F in HF samples; (ii) low seeding density and hypoxia resulted in predominant purification and expansion of CD146+/SMAα- CFU-Fs. (iii) the activity of NPs system was downregulated in HF BM-MMSC;

CONCLUSIONS

downregulation of NP signaling in combination with upregulation of Tgf-β pathway in BM-MMSC would result in pro-fibrotic phenotype and make these cells non-effective for therapeutic applications; the corrections in culturing strategy resulted in 2(3)-2(7) increase of expansion efficiency.

Concise Review: Mesenchymal Stem Cells Ameliorate Tissue Injury via Secretion of Tumor Necrosis Factor-α Stimulated Protein/Gene 6

Numerous reports have described therapeutic benefits in various disease models after administration of the adult stem/progenitor cells from bone marrow or other tissues referred to as mesenchymal stem cells/multipotent mesenchymal stromal cells (MSCs). They all showed that one of the important effects of MSCs is to act against excessive inflammatory responses and repair the damaged tissues. The therapeutic benefits of MSCs were initially interpreted by their migration, engraftment, and differentiation into target tissues. However, remarkable anatomical structural repairs and functional improvements were increasingly observed with a small number of or even no MSCs in the injured tissues. This suggests that most beneficial effects are largely due to paracrine secretions or cell-to-cell contacts that have multiple effects involving modulation of inflammatory and immune responses. Currently, the therapeutic benefits of MSCs are in part explained by the cells being activated by signals from injured tissues to express an anti-inflammatory protein, tumor-necrosis-factor-α-induced protein 6. This important mechanism of action has attracted increasing attention, and therefore we conducted this review to summarize the latest research.

Oxytocin improves the expression of cardiac specific markers in porcine bone marrow stem cells differentiation

Bone marrow stem cells (BMSCs) treated with 5-azacytidine possess myogenic differentiation potential. Oxytocin (OT) induces cardiomyogenesis in murine embryonic and cardiac stem cells. We attempted to isolate, characterize, and induce OT-mediated cardiomyogenic differentiation of porcine pBMSCs. Cells were treated as: control, OT, and 5-azacytidine groups. During early passages, transcripts of Oct4, GATA4, OT receptor, and phospholamban were expressed. RT-PCR showed upregulation of GATA4 in OT and 5-azacytidine-induced groups. Immunocytochemistry revealed higher expressions of cardiac troponin T and myosin heavy chain in OT than in 5-azacytidine-induced groups (p < 0.01). Western blot analysis showed upregulation of cardiac troponin I in OT-induced pBMSCs (p < 0.01). We infer pBMSCs should be induced during early passages, when expressing transcription factors related to pluripotency and cardiomyogenesis, as well as OT receptor. The more abundant expression of cardiac specific proteins in OT-treated pBMSCs suggests OT could be a more potent cardiomyogenic inducer of pBMSC.

Bone marrow mesenchymal stem cells enhance bone formation in orthodontically expanded maxillae in rats

OBJECTIVE

To transplant bone marrow-derived mesenchymal stem cells (MSCs) into the interpremaxillary suture after rapid maxillary expansion with the aim of increasing new bone formation in the suture.

MATERIALS AND METHODS

Nineteen male Wistar rats were divided into two groups (control, n  =  9; experimental, n  =  10). Both groups were subjected to expansion for 5 days, and 50 cN of force was applied to the maxillary incisors with a helical spring. Pkh67(+) (green fluorescent dye)-labeled MSCs were applied to the interpremaxillary suture after force application into the interpremaxillary suture of rats. Bone formation in the sutural area was histomorphometrically evaluated, including the amount of new bone formation (µm(2)), number of osteoblasts, number of osteoclasts, and number of vessels. Mann-Whitney U-test was used for statistical evaluation at the P < .05 level.

RESULTS

After 10 days of retention, Pkh67(+) can be detected in suture mostly in the injection site under fluorescence microscope. Histomorphometric analysis revealed that a single local injection of MSCs into the midpalatal suture increased the new bone formation in the suture by increasing the number of osteoblasts and new vessel formation, compared with controls injected with phosphate-buffered saline.

CONCLUSIONS

This preclinical study might provide foundations for the underlying potential clinical use of MSCs after maxillary expansion. Given the fact that MSCs are currently in use in clinical trials, this approach might be a feasible treatment strategy to accelerate new bone tissue formation in midpalatal suture and to shorten the treatment period for patients undergoing maxillary expansion reinforcement.

Renin inhibition improves the survival of mesenchymal stromal cells in a mouse model of myocardial infarction

The aim of this study was to determine if renin inhibition is able to improve the survival of transplanted stem cells in a mouse model of myocardial infarction. Myocardial infarction was induced in FVB/NJ inbred mice (n = 23). Bone marrow-derived mouse mesenchymal stromal cells (mMSCs, 3 × 10(5)) expressing the reporter gene firefly luciferase were delivered intramyocardially (n = 12) and monitored non-invasively by bioluminescence imaging. A group of these mice (n = 6) received aliskiren (15 mg/kg/day) via an osmotic pump implanted subcutaneously. The survival of mMSCs was significantly increased in those animals that received aliskiren leading to a significant improvement in systolic function after myocardial infarction. Histological analysis revealed a significant reduction in inflammation and collagen deposition in those mice that received aliskiren compared to controls. Renin inhibition of the ischemic myocardium is able to modulate the microenvironment improving the survival and efficacy of transplanted mMSCs in a mouse model of myocardial infarction.

Cell replacement strategies aimed at reconstitution of the β-cell compartment in type 1 diabetes

Emerging technologies in regenerative medicine have the potential to restore the β-cell compartment in diabetic patients, thereby overcoming the inadequacies of current treatment strategies and organ supply. Novel approaches include: 1) Encapsulation technology that protects islet transplants from host immune surveillance; 2) stem cell therapies and cellular reprogramming, which seek to regenerate the depleted β-cell compartment; and 3) whole-organ bioengineering, which capitalizes on the innate properties of the pancreas extracellular matrix to drive cellular repopulation. Collaborative efforts across these subfields of regenerative medicine seek to ultimately produce a bioengineered pancreas capable of restoring endocrine function in patients with insulin-dependent diabetes.

P53 regulates the migration of mesenchymal stromal cells in response to the tumor microenvironment through both CXCL12-dependent and -independent mechanisms

Mesenchymal stromal cells (MSCs) are multipotent fibroblast-like cells located in the bone marrow that localize to areas of tissue damage including wounds and solid tumors. Within the tumor microenvironment, MSCs adopt the phenotype of carcinoma-associated fibroblasts (CAFs) and stimulate tumor growth. Production of the chemokine CXCL12, also known as stromal cell-derived factor 1 (SDF-1), by MSCs is required for their in vitro migration in response to tumor cells and has also been implicated in stimulation of tumor growth. The tumor suppressor p53 regulates cellular migration, CXCL12 production and the promotion of tumor growth by carcinoma-associated fibroblasts (CAFs). We investigated the role of p53 in MSC migration to tumors. P53 inhibits the migration of MSCs in response to tumor cells in conjunction with a decrease in CXCL12 transcription. Conversely, decreased p53 activity leads to enhanced MSC migration. Interestingly, increased p53 activity inhibits MSC migration even in the context of high concentrations of exogenous CXCL12. These data show that stromal p53 status impacts the recruitment of MSCs to solid tumors through both regulation of CXCL12 production as well as other mechanisms. Stromal p53 may influence other important aspects of tumor biology such as tumor growth and metastasis through mechanisms distinct from CXCL12.

Autologous bone-marrow-derived-mononuclear-cells-enriched fat transplantation in breast augmentation: evaluation of clinical outcomes and aesthetic results in a 30-year-old female

Autologous fat transfer (lipofilling) is becoming an invaluable tool for breast augmentation as well as for breast reconstruction. Autologous lipofilling has several advantages, including biocompatibility, versatility, natural appearance, and low donor site morbidity. The main limitation is unpredictable fat graft resorption, which ranges from 25% to 80%, probably as a result of ischaemia and lack of neoangiogenesis. To obviate these disadvantages, several studies have searched for new ways of increasing the viability of the transplanted fat tissue. One promising approach is to enrich the fat graft with autologous bone-marrow-derived mononuclear cells (BMMNCs) before transplantation. BMMNCs produce many angiogenic and antiapoptotic growth factors, and their secretion is significantly enhanced by hypoxia. All of these mechanisms of actions could be beneficial for the stimulation of angiogenesis in ischemic tissues by BMMNCs administration. In our aesthetic surgery practice, we use fat transplantation enriched with BMMNCs, which caused a significant improvement in survival of fat grafts, compared with that of traditional lipofilling. Our experience with freshly isolated autologous fat enriched with BMMNCs for breast augmentation procedures is presented. The concept of this surgical and tissue handling technique is based on ability of BMMNCs to stimulate blood vessel growth.

From cellular therapies to tissue reprogramming and regenerative strategies in the treatment of diabetes

Diabetes mellitus represents a global epidemic affecting over 350 million patients worldwide and projected by the WHO to surpass the 500 million patient mark within the next two decades. Besides Type 1 and Type 2 diabetes mellitus, the study of the endocrine compartment of the pancreas is of great translational interest, as strategies aimed at restoring its mass could become therapies for glycemic dysregulation, drug-related diabetes following diabetogenic therapies, or hyperglycemic disturbances following the treatment of cancer and nesidioblastosis. Such strategies generally fall under one of the ‘three Rs’: replacement (islet transplantation and stem cell differentiation); reprogramming (e.g., from the exocrine compartment of the pancreas); and regeneration (replication and induction of endogenous stem cells). As the latter has been extensively reviewed in recent months by us and others, this article focuses on emerging reprogramming and replacement approaches.

Phorbol myristate acetate differentiates human adipose-derived mesenchymal stem cells into functional cardiogenic cells

To achieve effective regeneration of injured myocardium, it is important to find physiological way of improving the cardiogenic differentiation of stem cells. Previous studies demonstrated that cardiomyocytes from bone marrow-derived mesenchymal stem cells (BMSCs) activated with phorbolmyristate acetate (PMA), a protein kinase C (PKC) activator, restore electromechanical function in infarcted rat hearts. In this study, we investigated the effect of PMA on cardiogenic differentiation of adipose-derived MSCs (ASCs) for clinical applications. To confirm the effect of PMA, ASCs treated with 1μM PMA were grown for nine days. The expression of cardiac-specific markers (cardiac troponin T, myosin light chain, myosin heavy chain) in PMA-treated MSCs was demonstrated by immunocytochemistry. Alhough few α(1A) receptors exist in ASCs, α(1)-adrenergic receptor subtypes were preferentially expressed in PMA-treated ASCs. Moreover, expression of the β-adrenergic and muscarinic receptors increased in PMA-treated ASCs compared to normal cells. The mRNA levels of Ca(2+)-related factors (SERCA 2a; sarcoplasmic reticulum Ca(2+)-ATPase, LTCC; L-type Ca(2+) channel) in treated ASCs were similar to the levels in cardiomyocytes. Following the transplantation of chemically activated cardiogenic ASCs into infarcted myocardium, histological analysis showed that infarct size, interstitial fibrosis, and apoptotic index were markedly decreased and cardiac function was restored. In conclusion, PMA might induce the cardiogenic differentiation of human ASCs as well as BMSCs. This result suggests successful use of human ASCs in cardiac regeneration therapy.

Bone marrow-derived mesenchymal stem cells enhance cryopreserved trachea allograft epithelium regeneration and vascular endothelial growth factor expression

BACKGROUND

Epithelium regeneration and revascularization of tracheal implants are challenging issues to be solved in tracheal transplantation research. Bone marrow-derived mesenchymal stem cells (BMSCs) can migrate to the damaged tissue and promote functional restoration. Here, we applied intravenous transplantation of BMSCs combined with a cryopreserved allograft to investigate the role of BMSCs in enhancing implant survival, tracheal epithelium regeneration and revascularization.

METHODS

After transplantation with cryopreserved allografts, PKH-26 labeled 3 to 5 passage BMSCs were injected into recipient rats through the tail vein. Rats in the control groups were injected with a comparable amount of phosphate-buffered saline. We observed the histology of the tracheal allograft and measured vascular endothelial growth factor (VEGF) protein levels in the epithelium to evaluate the effect of BMSCs on epithelium regeneration and revascularization.

RESULTS

Histologic observation of the rats from the BMSCs injection groups showed that the tracheal lumen was covered by pseudostriated ciliated columnar epithelium. The cartilage structure was intact. There were no signs of denaturation or necrosis. PKH-26 labeled BMSCs migrated to the implant site and exhibited red fluorescence, with the brightest red fluorescence at the anastomotic site. VEGF protein levels in the allograft epithelium of the BMSCs injection group were higher than the levels in the phosphate-buffered saline injection group.

CONCLUSIONS

Our results indicate that given systemic administration, BMSCs may enhance epithelium regeneration and revascularization by upregulating VEGF expression.

Immunomodulative effects of mesenchymal stem cells derived from human embryonic stem cells in vivo and in vitro

OBJECTIVE

Human embryonic stem cells (hESCs) have recently been reported as an unlimited source of mesenchymal stem cells (MSCs). The present study not only provides an identical and clinically compliant MSC source derived from hESCs (hESC-MSCs), but also describes the immunomodulative effects of hESC-MSCs in vitro and in vivo for a carbon tetrachloride (CCl(4))-induced liver inflammation model.

METHODS

Undifferentiated hESCs were treated with Rho-associated kinase (ROCK) inhibitor and induced to fibroblast-looking cells. These cells were tested for their surface markers and multilineage differentiation capability. Further more, we analyzed their immune characteristics by mixed lymphocyte reactions (MLRs) and animal experiments.

RESULTS

hESC-MSCs show a homogenous fibroblastic morphology that resembles bone marrow-derived MSCs (BM-MSCs). The cell markers and differentiation potential of hESC-MSCs are also similar to those of BM-MSCs. Unlike their original cells, hESC-MSCs possess poor immunogenicity and can survive and be engrafted into a xenogenic immunocompetent environment.

CONCLUSIONS

The hESC-MSCs demonstrate strong inhibitory effects on lymphocyte proliferation in vitro and anti-inflammatory infiltration properties in vivo. This study offers information essential to the applications of hESC-MSC-based therapies and evidence for the therapeutic mechanisms of action.

Stem cell-derived islet cells for transplantation

PURPOSE OF REVIEW

The promise of islet transplantation for type 1 diabetes has been hampered by the lack of a renewable source of insulin-producing cells. However, steadfast advances in the field have set the stage for stem cell-based approaches to take over in the near future. This review focuses on the most intriguing findings reported in recent years, which include not only progress in adult and embryonic stem cell differentiation, but also the direct reprogramming of nonendocrine tissues into insulin-producing beta cells.

RECENT FINDINGS

In spite of their potential for tumorigenesis, human embryonic stem (hES) cells are poised to be in clinical trials within the next decade. This situation is mainly due to the preclinical success of a differentiation method that recapitulates beta cell development. In contrast, adult stem cells still need one such gold standard of differentiation, and progress is somewhat impeded by the lack of consensus on the best source. A concerted effort is necessary to bring their potential to clinical fruition. In the meantime, reported success in reprogramming might offer a 'third way' towards the rescue of pancreatic endocrine function.

SUMMARY

Here we discuss the important strategic decisions that need to be made in order to maximize the therapeutic chances of each of the presented approaches.

Paracrine effects of mesenchymal stem cells in cisplatin-induced renal injury require heme oxygenase-1

Multipotent mesenchymal stem cells (MSC) have become a popular and promising therapeutic approach in many clinical conditions. MSC are beneficial in animal models of acute kidney injury (AKI), by mediating differentiation-independent paracrine properties, and have prompted ongoing clinical trials to evaluate the safety and efficacy of MSC. Heme oxygenase-1 (HO-1) is induced in response to stress including AKI and has important anti-apoptotic, anti-inflammatory, and proangiogenic properties in these settings. We therefore examined whether HO-1 plays a role in the beneficial effects of MSC in AKI. We isolated MSC from bone marrow of age-matched HO-1+/+ and HO-1-/- mice. Our studies indicate that while differentiation of MSC into osteo- and adipocytic lineages did not differ between cells isolated from HO-1+/+ and HO-1-/- mice, MSC from HO-1-/- mice had significantly lower angiogenic potential. Moreover, HO-1-/- MSC demonstrated reduced expression and secretion of several important growth and proangiogenic factors (stromal cell-derived factor-1, vascular endothelial growth factor-A, and hepatocyte growth factor) compared with MSC derived from HO-1+/+ mice. In addition, conditioned medium of HO-1+/+ MSC rescued functional and morphological changes associated with cisplatin-induced AKI, while the HO-1-/--conditioned medium was ineffectual. Our studies indicate that HO-1 plays an important role in MSC-mediated protection. The results expand understanding of the renoprotective effects of MSC and may provide novel strategies to better utilize MSC in various disease models.

New insights into paracrine mechanisms of human cardiac progenitor cells

AIMS

Cardiac progenitor cells (CPCs) have been shown to promote cardiac regeneration in vivo. Understanding the function of CPCs is essential for further implementation of these cells in the treatment of cardiac diseases. The present study tested the hypothesis that adult CPC exert paracrine effects that lead to an improvement in the functional characteristics of cardiomyocytes. This study also investigated whether aging (we included patients aged between 4 months and 81 years) has any effect on the paracrine mechanisms of CPC.

METHODS AND RESULTS

The supernatant of CPC generated both from human and rat hearts-so called 'conditioned cardiosphere medium' improved the contractile behaviour of isolated adult cardiomyocytes in a concentration-dependent manner after incubation for 24 h and increased the SERCA/NCX ratio. The observed positive effects on contractile behaviour were independent of the CPC donors' age. Conditioned cardiosphere media also normalized angiotensin II-induced contractile dysfunction. Cytokines released by CPC into the media were detected by cytokine arrays.

CONCLUSION

The observed diversity of cytokines released by CPC needs to be further elucidated in detail. Nevertheless, CPC are a promising therapeutic approach in the field of cardiac disease. The methods described allow investigation of the underlying paracrine mechanisms in a standardized in vitro situation.

Mesenchymal stem cells promote matrix metalloproteinase secretion by cardiac fibroblasts and reduce cardiac ventricular fibrosis after myocardial infarction

Recent studies showed that mesenchymal stem cells (MSCs) transplantation significantly decreased cardiac fibrosis; however, the mechanisms involved in these effects are still poorly understood. In this work, we investigated whether the antifibrotic properties of MSCs involve the regulation of matrix metalloproteinases (MMPs) and matrix metalloproteinase endogenous inhibitor (TIMP) production by cardiac fibroblasts. In vitro experiments showed that conditioned medium from MSCs decreased viability, alpha-smooth muscle actin expression, and collagen secretion of cardiac fibroblasts. These effects were concomitant with the stimulation of MMP-2/MMP-9 activities and membrane type 1 MMP expression. Experiments performed with fibroblasts from MMP2-knockout mice demonstrated that MMP-2 plays a preponderant role in preventing collagen accumulation upon incubation with conditioned medium from MSCs. We found that MSC-conditioned medium also decreased the expression of TIMP2 in cardiac fibroblasts. In vivo studies showed that intracardiac injection of MSCs in a rat model of postischemic heart failure induced a significant decrease in ventricular fibrosis. This effect was associated with the improvement of morphological and functional cardiac parameters. In conclusion, we showed that MSCs modulate the phenotype of cardiac fibroblasts and their ability to degrade extracellular matrix. These properties of MSCs open new perspectives for understanding the mechanisms of action of MSCs and anticipate their potential therapeutic or side effects.

Cell therapy with bone marrow cells for myocardial regeneration

Cell therapy has tremendous potential for the damaged heart, which has limited self-renewing capability. Bone marrow (BM) cells are attractive for cell therapy, as they contain diverse stem and progenitor cell populations that can give rise to various cell types, including cardiomyocytes, endothelial cells, and smooth muscle cells. Studies have shown BM cells to be safe and efficacious in the treatment of myocardial infarction. Possible therapeutic mechanisms mediated by both host and transplanted cells include cardiomyogenesis, neovascularization, and attenuation of adverse remodeling. In this review, different stem and progenitor cells in the bone marrow and their application in cell therapy are reviewed, and evidence for their therapeutic mechanisms is discussed.

The immune boundaries for stem cell based therapies: problems and prospective solutions

Stem cells have fascinated the scientific and clinical communities for over a century. Despite the controversy that surrounds this field, it is clear that stem cells have the potential to revolutionize medicine. However, a number of significant hurdles still stand in the way of the realization of this potential. Chiefly among these are safety concerns, differentiation efficiency and overcoming immune rejection. Here we review current progress made in this field to optimize the safe use of stem cells with particular emphasis on prospective interventions to deal with challenges generated by immune rejection.

Non-expanded adipose stromal vascular fraction cell therapy for multiple sclerosis

The stromal vascular fraction (SVF) of adipose tissue is known to contain mesenchymal stem cells (MSC), T regulatory cells, endothelial precursor cells, preadipocytes, as well as anti-inflammatory M2 macrophages. Safety of autologous adipose tissue implantation is supported by extensive use of this procedure in cosmetic surgery, as well as by ongoing studies using in vitro expanded adipose derived MSC. Equine and canine studies demonstrating anti-inflammatory and regenerative effects of non-expanded SVF cells have yielded promising results. Although non-expanded SVF cells have been used successfully in accelerating healing of Crohn's fistulas, to our knowledge clinical use of these cells for systemic immune modulation has not been reported. In this communication we discuss the rationale for use of autologous SVF in treatment of multiple sclerosis and describe our experiences with three patients. Based on this rationale and initial experiences, we propose controlled trials of autologous SVF in various inflammatory conditions.

Epigenetic reprogramming of IGF1 and leptin genes by serum deprivation in multipotential mesenchymal stromal cells

Recent studies on the therapeutic effect of multipotential mesenchymal stem cells (MSCs) in various models of injury have shown that paracrine factors secreted by MSCs are responsible for tissue repair with very little engraftment. In this study we tested the hypothesis that MSCs under stress undergo epigenetic modifications that direct secretion of paracrine factors responsible for tissue repair. Microarray assays of MSCs that had been deprived of serum (SD-MSCs), to induce stress, demonstrated an increase in the expression of several angiogenic, prosurvival, and antiapoptotic factors, including insulin-like growth factor 1 (IGF1) and leptin. Real-time polymerase chain reaction assays demonstrated a >200-fold increase in the expression of IGF1 and leptin in SD-MSCs. Chromatin immunoprecipitation of SD-MSCs revealed histone tail modifications consistent with transcriptional activation of IGF1 and leptin promoters in a reversible manner. To identify the functional significance of the epigenetic changes in stressed MSCs, we tested the prosurvival properties of SD-MSCs and the ability of conditioned medium from SD-MSCs to enhance survival of apoptotic cancer cells. First, we showed that SD-MSCs are more resistant to oxidative damage than MSCs using alkaline comet assays. Next, we demonstrated that conditioned medium from SD-MSCs decreased staurosporin-induced cell death in the KHOS osteosarcoma cell line, and that this effect was partially reversed by immunodepletion of IGF1 or leptin from the conditioned medium. In conclusion, we demonstrate that serum deprivation induces epigenetic changes in MSCs to upregulate the expression of the proangiogenic and antiapoptotic factors IGF1 and leptin.

VEGF is a mediator of the renoprotective effects of multipotent marrow stromal cells in acute kidney injury

Adult stem cell treatment of complex disorders is a promising therapeutic approach and multipotent marrow stromal cells (MSCs) have been shown to be effective in various animal models of diseases. Acute kidney injury (AKI) is a common and serious problem in hospitalized patients and bone marrow derived multipotent MSCs have been shown to be effective in different models of AKI. The mechanism of action of MSCs is complex but involves paracrine actions including growth factor secretion. Knockdown of vascular enthothelial growth factor (VEGF) by siRNA reduced effectiveness of MSCs in the treatment of ischemic AKI in a rat model. Animals treated with MSCs had increased renal microvessel density compared to VEGF knockdown MSC-treated and vehicle-treated animals. These results show that VEGF is an important mediator of the early and late phase of renoprotective action after AKI in the context of stem cell treatment.