Mesenchymal stromal cells for cardiovascular disease

Extracellular vesicles from dental pulp mesenchymal stem cells modulate macrophage phenotype during acute and chronic cardiac inflammation in athymic nude rats with myocardial infarction

BACKGROUND/AIMS

Extracellular vesicles (EVs) derived from dental pulp mesenchymal stem cells (DP-MSCs) are a promising therapeutic option for the treatment of myocardial ischemia. The aim of this study is to determine whether MSC-EVs could promote a pro-resolving environment in the heart by modulating macrophage populations.

METHODS

EVs derived from three independent biopsies of DP-MSCs (MSC-EVs) were isolated by tangential flow-filtration and size exclusion chromatography and were characterized by omics analyses. Biological processes associated with these molecules were analyzed using String and GeneCodis platforms. The immunomodulatory capacity of MSC-EVs to polarize macrophages towards a pro-resolving or M2-like phenotype was assessed by evaluating surface markers, cytokine production, and efferocytosis. The therapeutic potential of MSC-EVs was evaluated in an acute myocardial infarction (AMI) model in nude rats. Infarct size and the distribution of macrophage populations in the infarct area were evaluated 7 and 21 days after intramyocardial injection of MSC-EVs.

RESULTS

Lipidomic, proteomic, and miRNA-seq analysis of MSC-EVs revealed their association with biological processes involved in tissue regeneration and regulation of the immune system, among others. MSC-EVs promoted the differentiation of pro-inflammatory macrophages towards a pro-resolving phenotype, as evidenced by increased expression of M2 markers and decreased secretion of pro-inflammatory cytokines. Administration of MSC-EVs in rats with AMI limited the extent of the infarcted area at 7 and 21 days post-infarction. MSC-EV treatment also reduced the number of pro-inflammatory macrophages within the infarct area, promoting the resolution of inflammation.

CONCLUSION

EVs derived from DP-MSCs exhibited similar characteristics at the omics level irrespective of the biopsy from which they were derived. All MSC-EVs exerted effective pro-resolving responses in a rat model of AMI, indicating their potential as therapeutic agents for the treatment of inflammation associated with AMI.

Intravascular Application of Labelled Cell Spheroids: An Approach for Ischemic Peripheral Artery Disease

Mesenchymal stem cells (MSC) are known for their vascular regeneration capacity by neoangiogenesis. Even though, several delivery approaches exist, particularly in the case of intravascular delivery, only limited number of cells reach the targeted tissue and are not able to remain on site. Applicated cells exhibit poor survival accompanied with a loss of functionality. Moreover, cell application techniques lead to cell death and impede the overall MSC function and survival. 3D cell spheroids mimic the physiological microenvironment, thus, overcoming these limitations. Therefore, in this study we aimed to evaluate and assess the feasibility of 3D MSCs spheroids for endovascular application, for treatment of ischemic peripheral vascular pathologies. Multicellular 3D MSC spheroids were generated at different cell seeding densities, labelled with ultra-small particles of iron oxide (USPIO) and investigated in vitro in terms of morphology, size distribution, mechanical stability as well as ex vivo with magnetic resonance imaging (MRI) to assess their trackability and distribution. Generated 3D spheroids were stable, viable, maintained stem cell phenotype and were easily trackable and visualized via MRI. MSC 3D spheroids are suitable candidates for endovascular delivery approaches in the context of ischemic peripheral vascular pathologies.

Photo-Polymerization Damage Protection by Hydrogen Sulfide Donors for 3D-Cell Culture Systems Optimization

Photo-polymerized hydrogels are ideally suited for stem-cell based tissue regeneration and three dimensional (3D) bioprinting because they can be highly biocompatible, injectable, easy to use, and their mechanical and physical properties can be controlled. However, photo-polymerization involves the use of potentially toxic photo-initiators, exposure to ultraviolet light radiation, formation of free radicals that trigger the cross-linking reaction, and other events whose effects on cells are not yet fully understood. The purpose of this study was to examine the effects of hydrogen sulfide (H₂S) in mitigating cellular toxicity of photo-polymerization caused to resident cells during the process of hydrogel formation. H₂S, which is the latest discovered member of the gasotransmitter family of gaseous signalling molecules, has a number of established beneficial properties, including cell protection from oxidative damage both directly (by acting as a scavenger molecule) and indirectly (by inducing the expression of anti-oxidant proteins in the cell). Cells were exposed to slow release H₂S treatment using pre-conditioning with glutathione-conjugated-garlic extract in order to mitigate toxicity during the photo-polymerization process of hydrogel formation. The protective effects of the H₂S treatment were evaluated in both an enzymatic model and a 3D cell culture system using cell viability as a quantitative indicator. The protective effect of H₂S treatment of cells is a promising approach to enhance cell survival in tissue engineering applications requiring photo-polymerized hydrogel scaffolds.

α-Tocopherol Acetate Attenuates Mitochondrial Oxygen Consumption and Maintains Primitive Cells within Mesenchymal Stromal Cell Population

We present here the data showing, in standard cultures exposed to atmospheric O₂ concentration, that alpha-tocopherol acetate (α-TOA) has a positive impact on primitive cells inside mesenchymal stromal cell (MstroC) population, by maintaining their proliferative capacity. α-TOA decreases the O₂ consumption rate of MStroC probably by impacting respiratory chain complex II activity. This action, however, is not associated with a compensatory increase in glycolysis activity, in spite of the fact that the degradation of HIF-1α was decreased in presence of α-TOA. This is in line with a moderate enhancement of mtROS upon α-TOA treatment. However, the absence of glycolysis stimulation implies the inactivity of HIF-1α which might - if it were active - be related to the maintenance of stemness. It should be stressed that α-TOA might act directly on the gene expression as well as the mtROS themselves, which remains to be elucidated. Alpha-tocopherol acetate (α-TOA), a synthetic vitamin E ester, attenuates electron flow through electron transport chain (ETC) which is probably associated with a moderate increase in mtROS in Mesenchymal Stromal Cells. α-TOA action results in enhancement of the proliferative capacity and maintenance of the differentiation potential of the mesenchymal stem and progenitor cells.

Cardiac fibroblast derived matrix-educated macrophages express VEGF and IL-6, and recruit mesenchymal stromal cells

The polarization of monocytes into macrophages that possess anti-inflammatory and pro-angiogenic properties could provide a novel therapeutic strategy for patients who are at a high risk for developing heart failure following myocardial infarction (MI). Here in, we describe a novel method of "educating" monocytes into a distinct population of macrophages that exhibit anti-inflammatory and pro-angiogenic features through a 3-day culture on fibronectin-rich cardiac matrix (CX) manufactured using cultured human cardiac fibroblasts. Our data suggest that CX can educate monocytes into a unique macrophage population termed CX educated macrophages (CXMq) that secrete high levels of VEGF and IL-6. In vitro, CXMq also demonstrate the ability to recruit mesenchymal stromal cells (MSC) with known anti-inflammatory properties. Selective inhibition of fibronectin binding to αVβ3 surface integrins on CXMq prevented MSC recruitment. This suggests that insoluble fibronectin within CX is, at least in part, responsible for CXMq conversion.

Stem Cells for Treatment of Musculoskeletal Conditions - Orthopaedic/Sports Medicine Applications

A myriad of musculoskeletal conditions afflicts a vast number of the world's population from birth to death. Countless pathological diseases and traumatic injuries (acute and chronic) contribute to different human disabilities, causing a tremendous financial toll on the economy of healthcare. The medical field is continually searching for novel ways to combat orthopedically related conditions. The immediate goal is the restoration of anatomy then ultimately return of function in hopes of enhancing quality if not the quantity of life. Traditional methods involve surgical correction/reconstruction of skeletal deformities from fractures/soft tissue damage/ruptures or replacement/resection of degenerated joints. Modern research is currently concentrating on innovative procedures to replenish/restore the human body close to its original/natural state [1, 2].

Non-thermal atmospheric pressure plasma is an excellent tool to activate proliferation in various mesoderm-derived human adult stem cells

Adult stem cells are capable of self-renewal and differentiation into specific cell types in tissues and have high potential for stem cell therapy. Mesenchymal and hematopoietic stem cells are easily attainable from the human body and have become applicable tools for adult stem cell therapy. However, there are still technical barriers for the application of mesenchymal and hematopoietic stem cells for therapy, such as the small number of cell populations, high risk of contamination, and loss of their stemness properties in vitro. In our previous study, we showed that non-thermal atmospheric pressure plasma (NTAPP) promoted the proliferation of adipose tissue-derived stem cells (ASCs) by 1.6-fold on average, while maintaining their stemness. Here, we examined the feasibility of NTAPP as a tool to activate the proliferation of mesenchymal and hematopoietic stem cells in vitro without affecting their stem cell characteristics. NTAPP increased the proliferation of bone marrow-derived stem cells (BM-MSCs) and hematopoietic stem cells (HSCs) by 1.8- and 2-fold, respectively, when compared to that of untreated cells. As observed in ASCs, NTAPP exposure also activated the expression of stem cell-specific surface markers, CD44 and CD105, by 5-fold in BM-MSCs, when compared to that in unexposed control cells in a low glucose medium with a low concentration of basic fibroblast growth factor (b-FGF). In addition, NTAPP exposure highly augmented the mRNA expression of well-known pluripotent genes for stemness, such as Oct4, Sox2, and Nanog in ASCs and BM-MSCs when compared to that in unexposed control cells. When cell cycle progression was examined, the G1-S shift was accelerated, and expression of PCNA was increased in NTAPP-exposed ASCs when compared to that in untreated control cells, suggesting that NTAPP activated G1-S transition. Taken together, these results demonstrated that NTAPP activated the proliferation of various mesodermal-derived human adult stem cells by accelerating the G1-S transition while maintaining their pluripotency and stemness, strongly suggesting that NTAPP can be an efficient tool for expanding the population of various adult stem cells in vitro for medical applications.

Immunosuppression Agent Cyclosporine Reduces Self-Renewal and Vessel Regeneration Potentiation of Human Endothelial Colony Forming Cells

Endothelial colony forming cells (ECFC) and mesenchymal stem cells (MSC) combined have great potential to be used for cell therapy of ischemic vascular diseases. However, to improve allogeneic stem cell engraftment the use of immunosuppression, such as cyclosporine has been suggested. Our aim was to assess the impact of cyclosporine on hind limb revascularisation upon MSC and ECFC combination therapy. Balb/c immunocompetent mice subjected to hind limb ischemia (right femoral artery ligation) were given both human ECFC and MSC (weekly intramuscular injections) with or without cyclosporine (daily injection). Surprisingly, mice receiving cyclosporine had a significant decrease in reperfusion based on laser Doppler imaging compared to vehicle controls and had poorer limb survival. In vitro, the downstream calcineurin target NFATC4 was highly expressed in the self‐renewing fraction of ECFCs. ECFCs cultured with cyclosporine had reduced colony formation capacity and tube formation in Matrigel. Lastly, ECFC displayed increased proliferation and loss of capacity for long term culture when in the presence of cyclosporine clearly showing a loss of quiescence and progenitor function. Our findings demonstrate the deleterious impact of cyclosporine on ECFC function, with significant impact on ECFC‐based allogeneic cellular therapy. stem cells translational medicine2019;8:162&7

Current Strategies to Generate Human Mesenchymal Stem Cells In Vitro

Mesenchymal stem cells (MSCs) are heterogeneous multipotent stem cells that are involved in the development of mesenchyme-derived evolving structures and organs during ontogeny. In the adult organism, reservoirs of MSCs can be found in almost all tissues where MSCs contribute to the maintenance of organ integrity. The use of these different MSCs for cell-based therapies has been extensively studied over the past years, which highlights the use of MSCs as a promising option for the treatment of various diseases including autoimmune and cardiovascular disorders. However, the proportion of MSCs contained in primary isolates of adult tissue biopsies is rather low and, thus, vigorous ex vivo expansion is needed especially for therapies that may require extensive and repetitive cell substitution. Therefore, more easily and accessible sources of MSCs are needed. This review summarizes the current knowledge of the different strategies to generate human MSCs in vitro as an alternative method for their applications in regenerative therapy.

[Stem cells: searching predisposition to cardiac commitment by surface markers expression]

It is well-known that cardiovascular diseases are the leading cause of death worldwide, and represent an important economic burden to health systems. In an attempt to solve this problem, stem cell therapy has emerged as a therapeutic option. Within the last 20 years, a great variety of stem cells have been used in different myocardial infarction models. Up until now, the use of cardiac stem cells (CSCs) has seemed to be the best option, but the inaccessibility and scarcity of these cells make their use unreliable. Additionally, there is a high risk as they have to be obtained directly from the heart of the patient. Unlike CSCs, adult stem cells originating from bone marrow or adipose tissue, among others, appear to be an attractive option due to their easier accessibility and abundance, but particularly due to the probable existence of cardiac progenitors among their different sub-populations. In this review an analysis is made of the surface markers present in CSCs compared with other adult stem cells. This suggested the pre-existence of cells sharing specific surface markers with CSCs, a predictable immunophenotype present in some cells, although in low proportions, and with a potential of cardiac differentiation that could be similar to CSCs, thus increasing their therapeutic value. This study highlights new perspectives regarding MSCs that would enable some of these sub-populations to be differentiated at cardiac tissue level.

Therapeutic assessment of mesenchymal stem cells delivered within a PEGylated fibrin gel following an ischemic injury

The intent of the current study was to investigate the therapeutic contribution of MSCs to vascular regeneration and functional recovery of ischemic tissue. We used a rodent hind limb ischemia model and intramuscularly delivered MSCs within a PEGylated fibrin gel matrix. Within this model, we demonstrated that MSC therapy, when delivered in PEGylated fibrin, results in significantly higher mature blood vessel formation, which allows for greater functional recovery of skeletal muscle tissue as assessed using force production measurements. We observed initial signs of vascular repair at early time points when MSCs were delivered without PEGylated fibrin, but this did not persist or lead to recovery of the tissue in the long-term. Furthermore, animals which were treated with PEGylated fibrin alone exhibited a greater number of mature blood vessels, but they did not arterialize and did not show improvements in force production. These results demonstrate that revascularization of ischemic tissue may be a necessary but not sufficient step to complete functional repair of the injured tissue. This work has implications on stem cell therapies for ischemic diseases and also potentially on how such therapies are evaluated.

RNA-Seq Reveals the Angiogenesis Diversity between the Fetal and Adults Bone Mesenchyme Stem Cell

In this research, we used RNA sequencing (RNA-seq) to analyze 23 single cell samples and 2 bulk cells sample from human adult bone mesenchyme stem cell line and human fetal bone mesenchyme stem cell line. The results from the research demonstrated that there were big differences between two cell lines. Adult bone mesenchyme stem cell lines showed a strong trend on the blood vessel differentiation and cell motion, 48/49 vascular related differential expressed genes showed higher expression in adult bone mesenchyme stem cell lines (Abmsc) than fetal bone mesenchyme stem cell lines (Fbmsc). 96/106 cell motion related genes showed the same tendency. Further analysis showed that genes like ANGPT1, VEGFA, FGF2, PDGFB and PDGFRA showed higher expression in Abmsc. This work showed cell heterogeneity between human adult bone mesenchyme stem cell line and human fetal bone mesenchyme stem cell line. Also the work may give an indication that Abmsc had a better potency than Fbmsc in the future vascular related application.

Vascular Wall-Resident Multipotent Stem Cells of Mesenchymal Nature within the Process of Vascular Remodeling: Cellular Basis, Clinical Relevance, and Implications for Stem Cell Therapy

Until some years ago, the bone marrow and the endothelial cell compartment lining the vessel lumen (subendothelial space) were thought to be the only sources providing vascular progenitor cells. Now, the vessel wall, in particular, the vascular adventitia, has been established as a niche for different types of stem and progenitor cells with the capacity to differentiate into both vascular and nonvascular cells. Herein, vascular wall-resident multipotent stem cells of mesenchymal nature (VW-MPSCs) have gained importance because of their large range of differentiation in combination with their distribution throughout the postnatal organism which is related to their existence in the adventitial niche, respectively. In general, mesenchymal stem cells, also designated as mesenchymal stromal cells (MSCs), contribute to the maintenance of organ integrity by their ability to replace defunct cells or secrete cytokines locally and thus support repair and healing processes of the affected tissues. This review will focus on the central role of VW-MPSCs within vascular reconstructing processes (vascular remodeling) which are absolute prerequisite to preserve the sensitive relationship between resilience and stability of the vessel wall. Further, a particular advantage for the therapeutic application of VW-MPSCs for improving vascular function or preventing vascular damage will be discussed.

Therapy with Multipotent Mesenchymal Stromal Cells Protects Lungs from Radiation-Induced Injury and Reduces the Risk of Lung Metastasis

AIMS

Previous thorax irradiation promotes metastatic spread of tumor cells to the lung. We hypothesized that vascular damage facilitates lung metastasis after thorax irradiation and that therapeutically applied multipotent mesenchymal stromal cells (MSCs) with reported repair activity may prevent these adverse effects of ionizing radiation by protecting lung endothelia from radiation-induced damage.

RESULTS

Previous whole-thorax irradiation (WTI) with 15 Gy significantly enhanced seeding and metastatic growth of tumor cells in the lung. WTI was further associated with endothelial cell damage, senescence of lung epithelial cells, and upregulation of invasion- and inflammation-promoting soluble factors, for example, endothelial matrix metalloproteinase 2 (Mmp2), its activator Mmp14, the cofactor tissue inhibitor of metalloproteinases 2 (Timp2), chemokine (C-C motif) ligand 2 (Ccl2), and urokinase-type plasminogen activator (Plau/uPA), and recruitment of CD11b+CD11c- myelomonocytic cells. Inhibition of Mmp2 counteracted radiation-induced vascular dysfunction without preventing increased metastasis. In contrast, therapy with bone marrow or aorta-derived MSCs within 2 weeks postirradiation antagonized radiation-induced damage to resident cells as well as the resulting secretome changes and abrogated the metastasis-promoting effects of WTI.

INNOVATION

Therapy with MSCs protects lungs from radiation-induced injury and reduces the risk of lung metastasis. MSC-mediated inhibition of Mmp2 mediates their protective effects at the vasculature. Furthermore, local and systemic effects such as inhibition of radiation-induced senescence of bronchial epithelial cells and associated secretion of immunomodulatory factors may participate in the inhibitory effect of MSCs on lung metastasis.

CONCLUSION

MSC therapy is a promising strategy to prevent radiation-induced lung injury and the resulting increased risk of metastasis.

Bone marrow-derived mesenchymal stem cells for the treatment of heart failure

Heart failure remains a major cause of death and disability, requiring rapid development of new therapies. Bone marrow-derived mesenchymal stem cell (MSC)-based therapy is an emerging approach for the treatment of both acute and chronic heart failure. Following successful experimental studies in a range of models, more than 40 clinical trials of MSC-based therapy for heart failure have now been registered, and the results of completed clinical trials so far have shown feasibility and safety of this approach with therapeutic potential suggested (though preliminarily). However, there appear to be several critical issues to be solved before this treatment could become a widespread standard therapy for heart failure. In this review, we comprehensively and systemically summarize a total of 73 preclinical studies and 11 clinical trial reports published to date. By analyzing the data in these reports, (1) improvement in the cell delivery method to the heart in order to enhance donor cell engraftment, (2) elucidation of mechanisms underpinning the therapeutic effects of the treatment differentiation and/or treatment secretion, and (3) validation of the utility of allogeneic MSCs which could enhance the efficacy and expand the application/indication of this therapeutic approach are highlighted as future perspectives. These important respects are further discussed in this review article with referencing latest scientific and clinical information.

Secreted trophic factors of Human umbilical cord stromal cells induce differentiation and neurite extension through PI3K and independent of cAMP pathway

Background

Trophic factors (TFs) play important role during development and adult tissue maintenance. In neurodegenerative diseases (ND) TF supplementation provides protection. Stromal cells (HUMS) derived from the human umbilical cord matrix provide neuroprotection in the ND models of mice.

Purpose

Though TF mediated protection is known, the exact mechanism of protection is not clear. So, here the essential TFs (secreted by HUMS cells) and the pathway of induction of neurite extension, differentiation and networking is addressed.

Methods

The HUMS cells from the human umbilical cord matrix were derived and the mouse spinal cord motor neuron cell line, NSC-34 was extensively used. Flow cytometry, immunohistochemistry, RT- PCR, western blot, ELISA and antibody/inhibitor treatment were carried out to figure out the TF pathway.

Results

The HUMS cells secrete six neurotrophic factors (sTFs), namely, NT-3, NGF, BDNF, VEGF, IGF-1 and GDNF (TFs). These TFs are sufficient to induce differentiation, neurite extension and neural networking in a motor neuron cell line, NSC34. All the 5 TFs need to be neutralized simultaneously with their antibodies to abrogate neurite extension. These motor neurons express the concomitant receptors, which are either receptor tyrosine kinase (TrK) coupled or to the receptor followed by the TrKs, for the above trophic factors (except for BDNF). The tyrosine kinase inhibitor, K252a, drastically reduces neurite extension. In NSC34, the TFs are coupled to the PI3K–Akt–pathway and the RAS-MAP kinase signaling through phosphorylation of ERK1 and ERK2. PI3K inhibitor, Ly 294002, abolishes neural differentiation and neurite extension. Thus, differentiation, neurite extension and networking could be achieved through the PI3K pathway. Intriguingly, the cAMP second messenger system coupling was not required. H89, PKA-inhibitor caused extensive cell death. But, had no effect in the presence of HUMS-secreted-TFs(HSTFs) suggesting a pathway switch for cell survival itself.

Conclusion

HUMS cells and their secreted factors could be of great use in regenerative medicine (RM). The activators of PI3K pathway, the major route of these HUMS-TFs action could be explored in RM and in the neurobiology of neural differentiation and extension.

CXCL14 and MCP1 are potent trophic factors associated with cell migration and angiogenesis leading to higher regenerative potential of dental pulp side population cells

Introduction

The release of trophic factors from mesenchymal stem cells (MSCs) is critical for tissue regeneration. A systematic investigation of the regenerative potential of trophic factors from different MSCs, however, has not been performed. Thus, in the present study, the regenerative potential of conditioned medium (CM) from dental pulp, bone marrow, and adipose tissue-derived CD31⁻ side population (SP) cells from an individual source was compared in an ectopic tooth transplantation model.

Methods

The tooth root transplantation in an ectopic site model was used for investigation of the regenerative potential and trophic effects in vivo. Either pulp CD31⁻ SP cell populations (1×10⁶ cells) at the third to fourth passage or 5 μg/ml of CM from dental pulp, bone marrow, and adipose stem cells from four different individuals were injected into the root with collagen TE. Each root was transplanted subcutaneously in 5-week-old severe combined immunodeficiency mice. Each root with surrounding tissue was harvested for histology on days 7, 21, and 28 and for Western blot analysis and real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis on day 28. Furthermore, the trophic factors responsible for the regenerative potential were identified as the upregulated genes present in pulp CD31⁻ SP cells when compared with the genes in both bone marrow and adipose CD31⁻ SP cells by using microarray analysis, real-time RT-PCR, and Western blot analysis.

Results

Transplantation of pulp CM yielded increased volume of pulp regeneration, more bromodeoxyuridine (BrdU)-positive migrated cells, and fewer caspase 3-positive cells in the regenerated pulp compared with the others. Pulp CM also demonstrated significantly increased cell migration, anti-apoptosis, and angiogenesis in C2C12 cells. Higher expression of CXCL14 and MCP1 in pulp SP cells suggested candidate trophic factors. The stimulatory effects on both migration and angiogenesis of CXCL14 and MCP1 were demonstrated in vitro. In the regenerated tissue, BrdU-positive migrated cells expressed CXCR4 and CCR2, receptors for CXCL14 and MCP1, respectively.

Conclusions

The higher regenerative potential of pulp SP cells may be due to potent trophic factors, including CXCL14 and MCP1, which promote migration and angiogenesis.

MicroRNA-377 regulates mesenchymal stem cell-induced angiogenesis in ischemic hearts by targeting VEGF

MicroRNAs have been appreciated in various cellular functions, including the regulation of angiogenesis. Mesenchymal-stem-cells (MSCs) transplanted to the MI heart improve cardiac function through paracrine-mediated angiogenesis. However, whether microRNAs regulate MSC induced angiogenesis remains to be clarified. Using microRNA microarray analysis, we identified a microRNA expression profile in hypoxia-treated MSCs and observed that among all dysregulated microRNAs, microRNA-377 was decreased the most significantly. We also validated that vascular endothelial growth factor (VEGF) is a target of microRNA-377 using dual-luciferase reporter assay and Western-blotting. Knockdown of endogenous microRNA-377 promoted tube formation in human umbilical vein endothelial cells. We then engineered rat MSCs with lentiviral vectors to either overexpress microRNA-377 (MSC miR-377) or knockdown microRNA-377 (MSC Anti-377) to investigate whether microRNA-377 regulated MSC-induced myocardial angiogenesis, using MSCs infected with lentiviral empty vector to serve as controls (MSC Null). Four weeks after implantation of the microRNA-engineered MSCs into the infarcted rat hearts, the vessel density was significantly increased in MSC Anti-377-hearts, and this was accompanied by reduced fibrosis and improved myocardial function as compared to controls. Adverse effects were observed in MSC miR-377-treated hearts, including reduced vessel density, impaired myocardial function, and increased fibrosis in comparison with MSC Null-group. These findings indicate that hypoxia-responsive microRNA-377 directly targets VEGF in MSCs, and knockdown of endogenous microRNA-377 promotes MSC-induced angiogenesis in the infarcted myocardium. Thus, microRNA-377 may serve as a novel therapeutic target for stem cell-based treatment of ischemic heart disease.

A Dual Gold Nanoparticle System for Mesenchymal Stem Cell Tracking

Stem cell-based therapies have demonstrated improved outcomes in preclinical and clinical trials for treating cardiovascular ischemic diseases. However, the contribution of stem cells to vascular repair is poorly understood. To elucidate these mechanisms, many have attempted to monitor stem cells following their delivery in vivo, but these studies have been limited by the fact that many contrast agents, including nanoparticles, are commonly passed on to non-stem cells in vivo. Specifically, cells of the reticuloendothelial system, such as macrophages, frequently endocytose free contrast agents, resulting in the monitoring of macrophages instead of the stem cell therapy. Here we demonstrate a dual gold nanoparticle system which is capable of monitoring both delivered stem cells and infiltrating macrophages using photoacoustic imaging. In vitro analysis confirmed preferential labeling of the two cell types with their respective nanoparticles and the maintenance of cell function following nanoparticle labeling. In addition, delivery of the system within a rat hind limb ischemia model demonstrated the ability to monitor stem cells and distinguish and quantify macrophage infiltration. These findings were confirmed by histology and mass spectrometry analysis. This work has important implications for cell tracking and monitoring cell-based therapies.

Targeted delivery of vascular endothelial growth factor improves stem cell therapy in a rat myocardial infarction model

Rebuilding of infarcted myocardium by mesenchymal stem cells (MSCs) has not been successful because of poor cell survival due in part to insufficient blood supply after myocardial infarction (MI). We hypothesize that targeted delivery of vascular endothelial growth factor (VEGF) to MI can help regenerate vasculature in support of MSC therapy in a rat model of MI. VEGF-encapsulated immunoliposomes targeting overexpressed P-selectin in MI tissue were infused by tail vein immediately after MI. One week later, MSCs were injected intramyocardially. The cardiac function loss was moderated slightly by targeted delivery of VEGF or MSC treatment. Targeted VEGF+MSC combination treatment showed highest attenuation in cardiac function loss. The combination treatment also increased blood vessel density (80%) and decreased collagen content in post-MI tissue (33%). Engraftment of MSCs in the combination treatment group was significantly increased and the engrafted cells contributed to the restoration of blood vessels.

FROM THE CLINICAL EDITOR

VEGF immunoliposomes targeting myocardial infarction tissue resulted in significantly higher attenuation of cardiac function loss when used in combination with mesenchymal stem cells. MSCs were previously found to have poor ability to restore cardiac tissue, likely as a result of poor blood supply in the affected areas. This new method counterbalances that weakness by the known effects of VEGF, as demonstrated in a rat model.

Priming mesenchymal stem cells boosts stem cell therapy to treat myocardial infarction

Cardiovascular diseases are the number one cause of death globally and are projected to remain the single leading cause of death. Treatment options abounds, although efficacy is limited. Recent studies attribute discrete and ephemeral benefits to adult stem cell therapies, indicating the urge to improve stem cell based-therapy. In this study, we show that priming mesenchymal stem cells (MSC) towards cardiomyogenic lineage enhances their beneficial effects in vivo as treatment option for acute phase myocardial infarction. MSC were primed using cardiomyogenic media for 4 days, after which peak expression of key cardiomyogenic genes are reached and protein expression of Cx-43 and sarcomeric α-actinin are observed. MSC and primed MSC (pMSC) were characterized in vitro and used to treat infarcted rats immediately after left anterior descending (LAD) occlusion. Echocardiography analysis indicated that MSC-treated myocardium presented discrete improvement in function, but it also showed that pMSC treatment lead to superior beneficial results, compared with undifferentiated MSC. Seven days after cell injection, MSC and pMSC could still be detected in the myocardium. Connexin-43 expression was quantified through immunoblotting, and was superior in pMSC, indicating that this could be a possible explanation for the superior performance of pMSC therapy.

Current stem cell delivery methods for myocardial repair

Heart failure commonly results from an irreparable damage due to cardiovascular diseases (CVDs), the leading cause of morbidity and mortality in the United States. In recent years, the rapid advancements in stem cell research have garnered much praise for paving the way to novel therapies in reversing myocardial injuries. Cell types currently investigated for cellular delivery include embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and adult stem cell lineages such as skeletal myoblasts, bone-marrow-derived stem cells (BMSCs), mesenchymal stem cells (MSCs), and cardiac stem cells (CSCs). To engraft these cells into patients' damaged myocardium, a variety of approaches (intramyocardial, transendocardial, transcoronary, venous, intravenous, intracoronary artery and retrograde venous administrations and bioengineered tissue transplantation) have been developed and explored. In this paper, we will discuss the pros and cons of these delivery modalities, the current state of their therapeutic potentials, and a multifaceted evaluation of their reported clinical feasibility, safety, and efficacy. While the issues of optimal delivery approach, the best progenitor stem cell type, the most effective dose, and timing of administration remain to be addressed, we are highly optimistic that stem cell therapy will provide a clinically viable option for myocardial regeneration.

Stimulation of angiogenesis, neurogenesis and regeneration by side population cells from dental pulp

Mesenchymal stem cells (MSCs) have been used for cell therapy in various experimental disease models. However, the regenerative potential of MSCs from different tissue sources and the influence of the tissue niche have not been investigated. In this study, we compared the regenerative potential of dental pulp, bone marrow and adipose tissue-derived CD31(-) side population (SP) cells isolated from an individual porcine source. Pulp CD31(-) SP cells expressed the highest levels of angiogenic/neurotrophic factors and had the highest migration activity. Conditioned medium from pulp CD31(-) SP cells produced potent anti-apoptotic activity and neurite outgrowth, compared to those from bone marrow and adipose CD31(-) SP cells. Transplantation of pulp CD31(-) SP cells in a mouse hindlimb ischemia model produced higher blood flow and capillary density than transplantation of bone marrow and adipose CD31(-) SP cells. Motor function recovery and infarct size reduction were greater with pulp CD31(-) SP cells. Pulp CD31(-) SP cells induced maximal angiogenesis, neurogenesis and pulp regeneration in ectopic transplantation models compared to other tissue sources. These results demonstrate that pulp stem cells have higher angiogenic, neurogenic and regenerative potential and may therefore be superior to bone marrow and adipose stem cells for cell therapy.

Optimized hyaluronic acid-hydrogel design and culture conditions for preservation of mesenchymal stem cell properties

A novel approach that preserved most mesenchymal stem cell (MSC) characteristics was developed using MSC encapsulation in a hydrogel based on hyaluronic acid (HA). An optimized HA-hydrogel composition, whose characteristics were assessed by scanning electron microscopy and viscoelastic property analyses, as well as the more favorable MSC seeding density, was established. These optimal three-dimensional MSC culture conditions allowed morphological cell remodeling, maintained the expression of stem cell markers over 28 days of culture, and preserved MSC differentiation plasticity. In addition, MSCs in HA-hydrogel submitted for 7 days to mechanical constraint that aimed at mimicking in vivo cardiac beat displayed enhanced cell survival by more than 40% compared to static culture conditions. Thus, the optimized HA-based hydrogel provides a niche for MSCs, which preserves their properties and opens ways for cell therapy, in particular in aortic repair medicine.

Challenges for heart disease stem cell therapy

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. The use of stem cells to improve recovery of the injured heart after myocardial infarction (MI) is an important emerging therapeutic strategy. However, recent reviews of clinical trials of stem cell therapy for MI and ischemic heart disease recovery report that less than half of the trials found only small improvements in cardiac function. In clinical trials, bone marrow, peripheral blood, or umbilical cord blood cells were used as the source of stem cells delivered by intracoronary infusion. Some trials administered only a stem cell mobilizing agent that recruits endogenous sources of stem cells. Important challenges to improve the effectiveness of stem cell therapy for CVD include: (1) improved identification, recruitment, and expansion of autologous stem cells; (2) identification of mobilizing and homing agents that increase recruitment; and (3) development of strategies to improve stem cell survival and engraftment of both endogenous and exogenous sources of stem cells. This review is an overview of stem cell therapy for CVD and discusses the challenges these three areas present for maximum optimization of the efficacy of stem cell therapy for heart disease, and new strategies in progress.