Mesenchymal lineage precursor cells induce vascular network formation in ischemic myocardium

Mesenchymal precursor cells reduce mortality and major morbidity in ischaemic heart failure with inflammation: DREAM-HF

AIMS

Progressive heart failure with reduced ejection fraction (HFrEF) is adversely affected by alterations in the myocardial balance between bone marrow-derived pro-inflammatory cardiac macrophages and embryo-derived reparative cardiac resident macrophages. Mesenchymal precursor cells (MPCs) may restore this balance and improve clinical outcomes when inflammation is present. The purpose was to (i) identify risk factors for cardiovascular death (CVD) in control patients with HFrEF in the DREAM-HF trial, and (ii) determine if MPCs improve major clinical outcomes (CVD, myocardial infarction [MI], stroke) in high-risk patients with ischaemic HFrEF and inflammation.

METHODS AND RESULTS

Cause-specific regression analyses were used to identify CVD risk factors in DREAM-HF control patients. Aalen-Johansen cumulative incidence curves were used to examine CVD, 2-point major adverse cardiovascular events (MACE) (MI or stroke), and 3-point MACE (CVD or MI or stroke) by treatment group in ischaemic vs non-ischaemic HFrEF and in patients with or without baseline inflammation. In control DREAM-HF patients, factors portending the greatest risk for CVD were inflammation (baseline plasma high-sensitivity C-reactive protein ≥2 mg/L; p = 0.003) and ischaemic HFrEF aetiology (p = 0.097), with increased CVD risk of 61% and 38%, respectively. Over 30-month mean follow-up, MPCs reduced 2-point and 3-point MACE by 88% (p = 0.005) and 52% (p = 0.018), respectively, in patients with ischaemic HFrEF and inflammation compared to controls.

CONCLUSION

Ischaemic aetiology and inflammation were identified as major risk factors for MACE in control DREAM-HF patients. A single intramyocardial MPC administration produced the most significant, sustained reduction in 2-point and 3-point MACE in patients with ischaemic HFrEF and inflammation.

Extracellular Vesicles: A Novel Diagnostic Tool and Potential Therapeutic Approach for Equine Osteoarthritis

Osteoarthritis (OA) is a chronic progressive degenerative joint disease that affects a significant portion of the equine population and humans worldwide. Current treatment options for equine OA are limited and incompletely curative. Horses provide an excellent large-animal model for studying human OA. Recent advances in the field of regenerative medicine have led to the exploration of extracellular vesicles (EVs)-cargoes of microRNA, proteins, lipids, and nucleic acids-to evaluate their diagnostic value in terms of disease progression and severity, as well as a potential cell-free therapeutic approach for equine OA. EVs transmit molecular signals that influence various biological processes, including the inflammatory response, apoptosis, proliferation, and cell communication. In the present review, we summarize recent advances in the isolation and identification of EVs, the use of their biologically active components as biomarkers, and the distribution of the gap junction protein connexin 43. Moreover, we highlight the role of mesenchymal stem cell-derived EVs as a potential therapeutic tool for equine musculoskeletal disorders. This review aims to provide a comprehensive overview of the current understanding of the pathogenesis, diagnosis, and treatment strategies for OA. In particular, the roles of EVs as biomarkers in synovial fluid, chondrocytes, and plasma for the early detection of equine OA are discussed.

Hypoxia and Hypoxia Mimetic Agents As Potential Priming Approaches to Empower Mesenchymal Stem Cells

Mesenchymal stem cells (MSC) exhibit self-renewal capacity and multilineage differentiation potential, making them attractive for research and clinical application. The properties of MSC can vary depending on specific micro-environmental factors. MSC resides in specific niches with low oxygen concentrations, where oxygen functions as a metabolic substrate and a signaling molecule. Conventional physical incubators or chemically hypoxia mimetic agents are applied in cultures to mimic the original low oxygen tension settings where MSC originated. This review aims to focus on the current knowledge of the effects of various physical hypoxic conditions and widely used hypoxia-mimetic agents-PHD inhibitors on mesenchymal stem cells at a cellular and molecular level, including proliferation, stemness, differentiation, viability, apoptosis, senescence, migration, immunomodulation behaviors, as well as epigenetic changes.

Randomized Trial of Targeted Transendocardial Mesenchymal Precursor Cell Therapy in Patients With Heart Failure

BACKGROUND

Mesenchymal precursor cells (MPCs) are allogeneic, immunoselected cells with anti-inflammatory properties that could improve outcomes in heart failure with reduced ejection fraction (HFrEF).

OBJECTIVES

This study assessed the efficacy and safety of MPCs in patients with high-risk HFrEF.

METHODS

This randomized, double-blind, multicenter study evaluated a single transendocardial administration procedure of MPCs or sham-control in 565 intention-to-treat patients with HFrEF on guideline-directed therapies. The primary endpoint was time-to-recurrent events caused by decompensated HFrEF or successfully resuscitated symptomatic ventricular arrhythmias. Hierarchical secondary endpoints included components of the primary endpoint, time-to-first terminal cardiac events, and all-cause death. Separate and composite major adverse cardiovascular events analyses were performed for myocardial infarction or stroke or cardiovascular death. Baseline and 12-month echocardiography was performed. Baseline plasma high-sensitivity C-reactive protein levels were evaluated for disease severity.

RESULTS

The primary endpoint was similar between treatment groups (HR: 1.17; 95% CI: 0.81-1.69; P = 0.41) as were terminal cardiac events and secondary endpoints. Compared with control subjects, MPCs increased left ventricular ejection fraction from baseline to 12 months, especially in patients with inflammation. MPCs decreased the risk of myocardial infarction or stroke by 58% (HR: 0.42; 95% CI: 0.23-0.76) and the risk of 3-point major adverse cardiovascular events by 28% (HR: 0.72; 95% CI: 0.51-1.03) in the analysis population (n = 537), and by 75% (HR: 0.25; 95% CI: 0.09-0.66) and 38% (HR: 0.62; 95% CI: 0.39-1.00), respectively, in patients with inflammation (baseline high-sensitivity C-reactive protein ≥2 mg/L).

CONCLUSIONS

The primary and secondary endpoints of the trial were negative. Positive signals in prespecified, and post hoc exploratory analyses suggest MPCs may improve outcomes, especially in patients with inflammation.

Stem Cell-based Therapies in Cardiovascular Diseases: From Pathophysiology to Clinical Outcomes

Over 20 years of intensified research in the field of stem cells brought about unprecedented possibilities in treating heart diseases. The investigators were initially fascinated by the idea of regenerating the lost myocardium and replacing it with new functional cardiomyocytes, but this was extremely challenging. However, the multifactorial effects of stem cell-based therapies beyond mere cardiomyocyte generation, caused by paracrine signaling, would open up new possibilities in treating cardiovascular diseases. To date, there is a strong body of evidence that the anti-inflammatory, anti-apoptotic, and immunomodulatory effects of stem cell therapy may alleviate atherosclerosis progression. In the present review, our objective is to provide a brief overview of the stem cell-based therapeutic options. We aim to delineate the pathophysiological mechanisms of their beneficial effects in cardiovascular diseases especially in coronary artery disease and to highlight some conclusions from important clinical studies in the field of regenerative medicine in cardiovascular diseases and how we could further move onwards.

Novel Targets for a Combination of Mechanical Unloading with Pharmacotherapy in Advanced Heart Failure

LVAD therapy is an effective rescue in acute and especially chronic cardiac failure. In several scenarios, it provides a platform for regeneration and sustained myocardial recovery. While unloading seems to be a key element, pharmacotherapy may provide powerful tools to enhance effective cardiac regeneration. The synergy between LVAD support and medical agents may ensure satisfying outcomes on cardiomyocyte recovery followed by improved quality and quantity of patient life. This review summarizes the previous and contemporary strategies for combining LVAD with pharmacotherapy and proposes new therapeutic targets. Regulation of metabolic pathways, enhancing mitochondrial biogenesis and function, immunomodulating treatment, and stem-cell therapies represent therapeutic areas that require further experimental and clinical studies on their effectiveness in combination with mechanical unloading.

Cellular Heterogeneity Facilitates the Functional Differences Between Hair Follicle Dermal Sheath Cells and Dermal Papilla Cells: A New Classification System for Mesenchymal Cells within the Hair Follicle Niche

Mesenchymal stem cells (MSCs) are known for their self-renewal and multi-lineage differentiation potential, with these cells often being evaluated in the regulation and maintenance of specific cellular niches including those of the hair follicle. Most mesenchymal stem cells in the hair follicles are housed in the dermal papilla (DP) and dermal sheath (DS), with both niches characterized by a broad variety of cellular subsets. However, while most previous studies describing the hair follicle mesenchymal niche treated all DP and DS cells as Hair Follicle Mesenchymal Stem Cells (HF-MSCs), the high number of cellular subsets would suggest that these cells are actually too heterogenous for such a broad definition. Given this we designed this study to evaluate the differentiation processes in these cells and used this data to create a new set of classifications for DP and DS cells, dividing them into "hair follicle mesenchymal stem cells (HF-MSCs)", "hair follicle mesenchymal progenitor cells (HF-MPCs)", and "hair follicle mesenchymal functional cells (HF-MFCs)". In addition, those cells that possess self-renewal and differentiation were re-named hair follicle derived mesenchymal multipotent cells (HF-MMCs). This new classification may help to further our understanding of the heterogeneity of hair follicle dermal cells and provide new insights into their evaluation.

Injectable Nanocomposite Implants Reduce ROS Accumulation and Improve Heart Function after Infarction

In a myocardial infarction, blood supply to the left ventricle is abrogated due to blockage of one of the coronary arteries, leading to ischemia, which further triggers the generation of reactive oxygen species (ROS). These sequential processes eventually lead to the death of contractile cells and affect the integrity of blood vessels, resulting in the formation of scar tissue. A new heart therapy comprised of cardiac implants encapsulated within an injectable extracellular matrix-gold nanoparticle composite hydrogel is reported. The particles on the collagenous fibers within the hydrogel promote fast transfer of electrical signal between cardiac cells, leading to the functional assembly of the cardiac implants. The composite hydrogel is shown to absorb reactive oxygen species in vitro and in vivo in mice ischemia reperfusion model. The reduction in ROS levels preserve cardiac tissue morphology and blood vessel integrity, reduce the scar size and the inflammatory response, and significantly prevent the deterioration of heart function.

Reviewing the role of cardiac exosomes in myocardial repair at a glance

Exosome-based therapy is an emerging novel approach for myocardial infarction (MI) treatment. Exosomes are identified as extracellular vesicles that are produced within multivesicular bodies in the cells' cytosols and then are secreted from the cells. Exosomes are 30-100 nm in diameter that are released from viable cells and are different from other secreted vesicles such as apoptotic bodies and microvesicles in their origin and contents such as RNAs, proteins, and nucleic acid. The recent advances in exosome research have demonstrated the role of these bionanovesicles in the physiological, pathological, and molecular aspects of the heart. The results of in vitro and preclinical models have shown that exosomes from different cardiac cells can improve cardiac function following MI. For example, mesenchymal stem cells (MSCs) and cardiac progenitor cells (CPCs) containing exosomes can affect the proliferation, survival, and differentiation of cardiac fibroblasts and cardiomyocytes. Moreover, MSCs- and CPCs-derived exosomes can enhance the migration of endothelial cells. Exosome-based therapy approaches augment the cardiac function by multiple means, such as reducing fibrosis, stimulation of vascular angiogenesis, and proliferation of cardiomyocytes that result in replacing damaged heart tissue with newly generated functional myocytes. This review article aims to briefly discuss the recent advancements in the role of secreted exosomes in myocardial repair by focusing on cardiac cells-derived exosomes.

Safety and clinical efficacy of the secretome of stressed peripheral blood mononuclear cells in patients with diabetic foot ulcer-study protocol of the randomized, placebo-controlled, double-blind, multicenter, international phase II clinical trial MARSYAS II

Background

Diabetes and its sequelae such as diabetic foot ulcer are rising health hazards not only in western countries but all over the world. Effective, yet safe treatments are desperately sought for by physicians, healthcare providers, and of course patients.

Methods/design

APOSEC, a novel, innovative drug, is tested in the phase I/II study MARSYAS II, where its efficacy to promote healing of diabetic foot ulcers will be determined. To this end, the cell-free secretome of peripheral blood mononuclear cells (APOSEC) blended with a hydrogel will be applied topically three times weekly for 4 weeks. APOSEC is predominantly effective in hypoxia-induced tissue damages by modulating the immune system and enhancing angiogenesis, whereby its anti-microbial ability and neuro-regenerative capacity will exert further positive effects. In total, 132 patients will be enrolled in the multicenter, randomized, double-blind, placebo-controlled, parallel group, dose-ranging phase I/II study and treated with APOSEC at three dose levels or placebo for 4 weeks, followed by an 8-week follow-up period to evaluate safety and efficacy of the drug. Wound area reduction after 4 weeks of treatment will serve as the primary endpoint.

Conclusion

We consider our study protocol to be suitable to test topically administered APOSEC in patients suffering from diabetic foot ulcers in a clinical phase I/II trial.

Trial registration

EudraCT 2018-001653-27. Registered on 30 July 2019. ClinicalTrials.gov NCT04277598. Registered on 20 February 2020. Title: “A randomized, placebo-controlled, double-blind study to evaluate safety and dose-dependent clinical efficacy of APO-2 at three different doses in patients with diabetic foot ulcer (MARSYAS II)”

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-020-04948-1.

Human umbilical cord mesenchymal stem cells ameliorate skin fibrosis development in a mouse model of bleomycin-induced systemic sclerosis

Mesenchymal stem cell (MSC) infusion has become a novel therapeutic strategy for complex autoimmune diseases; however, few detailed studies have been performed to investigate the benefit and mechanism of MSC treatment on systemic sclerosis (SSc). The present study aimed to evaluate the therapeutic effect of human umbilical cord derived-MSCs (UC-MSCs) on bleomycin-induced SSc in mice and explore the potential underlying mechanism. The murine SSc model was established by daily subcutaneous injection of bleomycin for 4 weeks, followed with two UC-MSC infusions every 7 days. Skin fibrosis was assessed by H&E and Masson staining. Flow cytometry was used to determine IL-17A, IFN-γ, tumor necrosis factor-β, IL-10 and IL-12 levels in serum samples and T cell subsets in murine spleen. Additionally, gene expression levels of cytokines and fibrosis markers in skin samples were measured by reverse transcription-quantitative PCR. Immunofluorescence staining was performed to track UC-MSC localization and lymphocyte cell infiltration in vivo. UC-MSC treatment exerted an anti-fibrotic role in bleomycin-induced SSc mice, as confirmed by histological improvement, decreased collagen synthesis, and reduced collagen-1α1, collagen-1α2, fibronectin-1 and α-smooth muscle actin gene expression levels. The results indicated that UC-MSC treatment only had a limited systematic effect on cytokine production in serum samples and T cell activation in the spleen. By contrast, T helper (Th)17 cell infiltration and activation in skin were efficiently inhibited after UC-MSC infusion, as evidenced by the decreased IL-17A and retinoic acid-related orphan receptor γt gene expression as well as IL-17A production. UC-MSC administration significantly ameliorated bleomycin-induced skin fibrosis and collagen formation primarily by eliminating local inflammation and Th17 cell activation in the skin; however, the systemic inhibitory effect of UM-MSCs on cytokines was less profound.

Hurdles to uptake of mesenchymal stem cells and their progenitors in therapeutic products

Twenty-five years have passed since the first clinical trial utilising mesenchymal stomal/stem cells (MSCs) in 1995. In this time academic research has grown our understanding of MSC biochemistry and our ability to manipulate these cells in vitro using chemical, biomaterial, and mechanical methods. Research has been emboldened by the promise that MSCs can treat illness and repair damaged tissues through their capacity for immunomodulation and differentiation. Since 1995, 31 therapeutic products containing MSCs and/or progenitors have reached the market with the level of in vitro manipulation varying significantly. In this review, we summarise existing therapeutic products containing MSCs or mesenchymal progenitor cells and examine the challenges faced when developing new therapeutic products. Successful progression to clinical trial, and ultimately market, requires a thorough understanding of these hurdles at the earliest stages of in vitro pre-clinical development. It is beneficial to understand the health economic benefit for a new product and the reimbursement potential within various healthcare systems. Pre-clinical studies should be selected to demonstrate efficacy and safety for the specific clinical indication in humans, to avoid duplication of effort and minimise animal usage. Early consideration should also be given to manufacturing: how cell manipulation methods will integrate into highly controlled workflows and how they will be scaled up to produce clinically relevant quantities of cells. Finally, we summarise the main regulatory pathways for these clinical products, which can help shape early therapeutic design and testing.

Targeting Purinergic Signaling and Cell Therapy in Cardiovascular and Neurodegenerative Diseases

Extracellular purines exert several functions in physiological and pathophysiological mechanisms. ATP acts through P2 receptors as a neurotransmitter and neuromodulator and modulates heart contractility, while adenosine participates in neurotransmission, blood pressure, and many other mechanisms. Because of their capability to differentiate into mature cell types, they provide a unique therapeutic strategy for regenerating damaged tissue, such as in cardiovascular and neurodegenerative diseases. Purinergic signaling is pivotal for controlling stem cell differentiation and phenotype determination. Proliferation, differentiation, and apoptosis of stem cells of various origins are regulated by purinergic receptors. In this chapter, we selected neurodegenerative and cardiovascular diseases with clinical trials using cell therapy and purinergic receptor targeting. We discuss these approaches as therapeutic alternatives to neurodegenerative and cardiovascular diseases. For instance, promising results were demonstrated in the utilization of mesenchymal stem cells and bone marrow mononuclear cells in vascular regeneration. Regarding neurodegenerative diseases, in general, P2X7 and A_2A receptors mostly worsen the degenerative state. Stem cell-based therapy, mainly through mesenchymal and hematopoietic stem cells, showed promising results in improving symptoms caused by neurodegeneration. We propose that purinergic receptor activity regulation combined with stem cells could enhance proliferative and differentiation rates as well as cell engraftment.

Therapeutic Mesenchymal Stromal Cells for Immunotherapy and for Gene and Drug Delivery

Mesenchymal stromal cells (MSCs) possess several fairly unique properties that, when combined, make them ideally suited for cellular-based immunotherapy and as vehicles for gene and drug delivery for a wide range of diseases and disorders. Key among these are: (1) their relative ease of isolation from a variety of tissues; (2) the ability to be expanded in culture without a loss of functionality, a property that varies to some degree with tissue source; (3) they are relatively immune-inert, perhaps obviating the need for precise donor/recipient matching; (4) they possess potent immunomodulatory functions that can be tailored by so-called licensing in vitro and in vivo; (5) the efficiency with which they can be modified with viral-based vectors; and (6) their almost uncanny ability to selectively home to damaged tissues, tumors, and metastases following systemic administration. In this review, we summarize the latest research in the immunological properties of MSCs, their use as immunomodulatory/anti-inflammatory agents, methods for licensing MSCs to customize their immunological profile, and their use as vehicles for transferring both therapeutic genes in genetic disease and drugs and genes designed to destroy tumor cells.

Phase 3 DREAM-HF Trial of Mesenchymal Precursor Cells in Chronic Heart Failure

Advanced heart failure (HF) is a progressive disease characterized by recurrent hospitalizations and high risk of mortality. Indeed, outcomes in late stages of HF approximate those seen in patients with various aggressive malignancies. Clinical trials assessing beneficial outcomes of new treatments in patients with cancer have used innovative approaches to measure impact on total disease burden or surrogates to assess treatment efficacy. Although most cardiovascular outcomes trials continue to use time-to-first event analyses to assess the primary efficacy end point, such analyses do not adequately reflect the impact of new treatments on the totality of the chronic disease burden. Consequently, patient enrichment and other strategies for ongoing clinical trial design, as well as new statistical methodologies, are important considerations, particularly when studying a population with advanced chronic HF. The DREAM-HF trial (Double-Blind Randomized Assessment of Clinical Events With Allogeneic Mesenchymal Precursor Cells in Advanced Heart Failure) is an ongoing, randomized, sham-controlled phase 3 study of the efficacy and safety of mesenchymal precursor cells as immunotherapy in patients with advanced chronic HF with reduced ejection fraction. Mesenchymal precursor cells have a unique multimodal mechanism of action that is believed to result in polarization of proinflammatory type 1 macrophages in the heart to an anti-inflammatory type 2 macrophage state, inhibition of maladaptive adverse left ventricular remodeling, reversal of cardiac and peripheral endothelial dysfunction, and recovery of deranged vasculature. The objective of DREAM-HF is to confirm earlier phase 2 results and evaluate whether mesenchymal precursor cells will reduce the rate of nonfatal recurrent HF-related major adverse cardiac events while delaying or preventing progression of HF to terminal cardiac events. DREAM-HF is an example of an ongoing contemporary events-driven cardiovascular cell-based immunotherapy study that has utilized the concepts of baseline disease enrichment, prognostic enrichment, and predictive enrichment to improve its efficiency by using accumulating data from within as well as external to the trial. Adaptive enrichment designs and strategies are important components of a rational approach to achieve clinical research objectives in shorter clinical trial timelines and with increased cost-effectiveness without compromising ethical standards or the overall statistical integrity of the study. The DREAM-HF trial also presents an alternative approach to traditional composite time-to-first event primary efficacy end points. Statistical methodologies such as the joint frailty model provide opportunities to expand the scope of events-driven HF with reduced ejection fraction clinical trials to utilize time to recurrent nonfatal HF-related major adverse cardiac events as the primary efficacy end point without compromising the integrity of the statistical analyses for terminal cardiac events. In advanced chronic HF with reduced ejection fraction studies, the joint frailty model is utilized to reflect characteristics of the high-risk patient population with important unmet therapeutic needs. In some cases, use of the joint frailty model may substantially reduce sample size requirements. In addition, using an end point that is acceptable to the Food and Drug Administration and the European Medicines Agency, such as recurrent nonfatal HF-related major adverse cardiac events, enables generation of clinically relevant pharmacoeconomic data while providing comprehensive views of the patient's overall cardiovascular disease burden. The major goal of this review is to provide lessons learned from the ongoing DREAM-HF trial that relate to biologic plausibility and flexible clinical trial design and are potentially applicable to other development programs of innovative therapies for patients with advanced cardiovascular disease. Clinical Trial Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02032004.

Endothelial Progenitor and Mesenchymal Stromal Cells in Newborns With Congenital Diaphragmatic Hernia Undergoing Extracorporeal Membrane Oxygenation

Background: Endothelial progenitor (EPC) and mesenchymal stromal cells (MSC) can regenerate damaged endothelium and thereby improve pulmonary endothelial dysfunction. We do not know, how extracorporeal membrane oxygenation (ECMO) might affect EPC- and MSC-mediated regenerative pathways in patients with congenital diaphragmatic hernia (CDH). Therefore, we investigated, if ECMO support impacts EPC and MSC numbers in CDH patients. Methods: Peripheral blood mononuclear cells from newborns with ECMO-dependent (n = 18) and ECMO-independent CDH (n = 12) and from healthy controls (n = 12) were isolated. The numbers of EPC and MSC were identified by flowcytometry. Serum levels of vascular endothelial growth factor (VEGF) and angiopoietin (Ang)-2 were determined. Results: EPC and MSC were elevated in newborns with CDH. ECMO-dependent infants had higher EPC subpopulation counts (2,1-7,6-fold) before treatment compared to ECMO-independent infants. In the disease course, EPC and MSC subpopulation counts in ECMO-dependent infants were lower than before ECMO initiation. During ECMO, VEGF serum levels were significantly reduced (by 90.5%) and Ang2 levels significantly increased (by 74.8%). Conclusions: Our data suggest that ECMO might be associated with a rather impaired mobilization of EPC and MSC and with a depression of VEGF serum levels in newborns with CDH.

The Optimal Timing for Pancreatic Islet Transplantation into Subcutaneous Scaffolds Assessed by Multimodal Imaging

Subcutaneously implanted polymeric scaffolds represent an alternative transplantation site for pancreatic islets (PIs) with the option of vascularisation enhancement by mesenchymal stem cells (MSC). Nevertheless, a proper timing of the transplantation steps is crucial. In this study, scaffolds supplemented with plastic rods were implanted into diabetic rats and two timing schemes for subsequent transplantation of bioluminescent PIs (4 or 7 days after rod removal) were examined by multimodal imaging. The cavities were left to heal spontaneously or with 10 million injected MSCs. Morphological and vascularisation changes were examined by MRI, while the localisation and viability of transplanted islets were monitored by bioluminescence imaging. The results show that PIs transplanted 4 days after rod removal showed the higher optical signal and vascularisation compared to transplantation after 7 days. MSCs slightly improved vascularisation of the graft but hindered therapeutic efficiency of PIs. Long-term glycaemia normalisation (4 months) was attained in 80% of animals. In summary, multimodal imaging confirmed the long-term survival and function of transplanted PIs in the devices. The best outcome was reached with PIs transplanted on day 4 after rod removal and therefore the suggested protocol holds a potential for further applications.

Mesenchymal Stem Cells in Cardiology

Cardiovascular disease (CVD) accounts for more deaths globally than any other single disease. There are on average 1.5 million episodes of myocardial infarction (heart attack) each year in the United States alone with roughly one-third resulting in death. There is therefore a major need for developing new and effective strategies to promote cardiac repair. Intramyocardial transplantation of mesenchymal stem cells (MSCs) has emerged as a leading contender in the pursuit of clinical intervention and therapy. MSCs are potent mediators of cardiac repair and are therefore an attractive tool in the development of preclinical and clinical trials. MSCs are capable of secreting a large array of soluble factors, which have had demonstrated effects on pathogenic cardiac remolding, fibrosis, immune activation, and cardiac stem cell proliferation within the damaged heart. MSCs are also capable of differentiation into cardiomyocytes, endothelial cells, and vascular smooth muscle cells, although the relative contribution of trilineage differentiation and paracrine effectors on cardiac repair remains the subject of active investigation.

Multimodal Imaging Reveals Improvement of Blood Supply to an Artificial Cell Transplant Site Induced by Bioluminescent Mesenchymal Stem Cells

PURPOSE

An artificial site for cell or pancreatic islet transplantation can be created using a polymeric scaffold, even though it suffers subcutaneously from improper vascularisation. A sufficient blood supply is crucial for graft survival and function and can be enhanced by transplantation of mesenchymal stem cells (MSCs). The purpose of this study was to assess the effect of syngeneic MSCs on neoangiogenesis and cell engraftment in an artificial site by multimodal imaging.

PROCEDURES

MSCs expressing a gene for luciferase were injected into the artificial subcutaneous site 7 days after scaffold implantation. MRI experiments (anatomical and dynamic contrast-enhanced images) were performed on a 4.7-T scanner using gradient echo sequences. Bioluminescent images were acquired on an IVIS Lumina optical imager. Longitudinal examination was performed for 2 months, and one animal was monitored for 16 months.

RESULTS

We confirmed the long-term presence (lasting more than 16 months) of viable donor cells inside the scaffolds using bioluminescence imaging with an optical signal peak appearing on day 3 after MSC implantation. When compared to controls, the tissue perfusion and vessel permeability in the scaffolds were significantly improved at the site with MSCs with a maximal peak on day 9 after MSC transplantation.

CONCLUSIONS

Our data suggest that the maximal signal obtained by bioluminescence and magnetic resonance imaging from an artificially created site between 3 and 9 days after MSC transplantation can predict the optimal time range for subsequent cellular or tissue transplantation, including pancreatic islets.

Effect of low oxygen tension on the biological characteristics of human bone marrow mesenchymal stem cells

Culture of mesenchymal stem cells (MSCs) under ambient conditions does not replicate the low oxygen environment of normal physiological or pathological states and can result in cellular impairment during culture. To overcome these limitations, we explored the effect of hypoxia (1 % O2) on the biological characteristics of MSCs over the course of different culture periods. The following biological characteristics were examined in human bone marrow-derived MSCs cultured under hypoxia for 8 weeks: proliferation rate, morphology, cell size, senescence, immunophenotypic characteristics, and the expression levels of stemness-associated factors and cytokine and chemokine genes. MSCs cultured under hypoxia for approximately 2 weeks showed increased proliferation and viability. During long-term culture, hypoxia delayed phenotypic changes in MSCs, such as increased cell volume, altered morphology, and the expression of senescence-associated-β-gal, without altering their characteristic immunophenotypic characteristics. Furthermore, hypoxia increased the expression of stemness and chemokine-related genes, including OCT4 and CXCR7, and did not decrease the expression of KLF4, C-MYC, CCL2, CXCL9, CXCL10, and CXCR4 compared with levels in cells cultured under normoxia. In conclusion, low oxygen tension improved the biological characteristics of MSCs during ex vivo expansion. These data suggest that hypoxic culture could be a useful method for increasing the efficacy of MSC cell therapies.

The effects of hypoxia on the stemness properties of human dental pulp stem cells (DPSCs)

Recent studies have demonstrated that culture under hypoxia has beneficial effects on mesenchymal stem cells (MSCs). However, there are limitations to achieving a stable condition in conventional hypoxic CO₂ incubators. DPSCs are a unique type of MSCs which are promising in many regenerative therapies. In this study, we investigated the ideal hypoxic culture environment for DPSCs using a new system that can provide controlled O₂ environment. The effects of hypoxia (3%, 5%) on the stemness properties of DPSCs. Their morphology, proliferation rate, expression of stem cell markers, migration ability, mRNA expression of angiogenic/neurotrophic factors and immunomodulatory genes were evaluated and compared. Additionally, the effect of the discrete secretome on proliferation, migration, and neurogenic induction was assessed. Hypoxic DPSCs were found to be smaller in size and exhibited larger nuclei. 5% O₂ significantly increased the proliferation rate, migration ability, expression of stem cell markers (CXCR4 and G-CSFR), and expression of SOX2, VEGF, NGF, and BDNF genes of DPSCs. Moreover, secretome collected from 5%O₂ cultures displayed higher stimulatory effects on proliferation and migration of NIH3T3 cells and on neuronal differentiation of SH-SY5Y cells. These results demonstrate that 5%O₂ may be ideal for enhancing DPSCs growth, stem cell properties, and secretome trophic effect.

Mesenchymal stem cell subpopulations: phenotype, property and therapeutic potential

Mesenchymal stem cells (MSC) are capable of differentiating into cells of multiple cell lineages and have potent paracrine effects. Due to their easy preparation and low immunogenicity, MSC have emerged as an extremely promising therapeutic agent in regenerative medicine for diverse diseases. However, MSC are heterogeneous with respect to phenotype and function in current isolation and cultivation regimes, which often lead to incomparable experimental results. In addition, there may be specific stem cell subpopulations with definite differentiation capacity toward certain lineages in addition to stem cells with multi-differentiation potential. Recent studies have identified several subsets of MSC which exhibit distinct features and biological activities, and enhanced therapeutic potentials for certain diseases. In this review, we give an overview of these subsets for their phenotypic, biological and functional properties.

Fucoidan improves bioactivity and vasculogenic potential of mesenchymal stem cells in murine hind limb ischemia associated with chronic kidney disease

Chronic kidney disease (CKD) is a significant risk factor for cardiovascular and peripheral vascular disease. Although mesenchymal stem cell (MSC)-based therapy is a promising strategy for treatment of ischemic diseases associated with CKD, the associated pathophysiological conditions lead to low survival and proliferation of transplanted MSCs. To address these limitations, we investigated the effects of fucoidan, a sulfated polysaccharide, on the bioactivity of adipose tissue-derived MSCs and the potential of fucoidan-treated MSCs to improve neovascularization in ischemic tissues of CKD mice. Treatment of MSCs with fucoidan increased their proliferative potential and the expression of cell cycle-associated proteins, such as cyclin E, cyclin dependent kinase (CDK) 2, cyclin D1, and CDK4, via focal adhesion kinase and the phosphatidylinositol-4,5-bisphosphate 3-kinase-Akt axis. Moreover, fucoidan enhanced the immunomodulatory activity of MSCs through the ERK-IDO-1 signal cascade. Fucoidan was found to augment the proliferation, incorporation, and endothelial differentiation of transplanted MSCs at ischemic sites in CKD mice hind limbs. In addition, transplantation of fucoidan-treated MSCs enhanced the ratio of blood flow and limb salvage in CKD mice with hind limb ischemia. To our knowledge, our findings are the first to reveal that fucoidan enhances the bioactivity of MSCs and improves their neovascularization in ischemic injured tissues of CKD. In conclusion, fucoidan-treated MSCs may provide an important pathway toward therapeutic neovascularization in patients with CKD.

Allogeneic mesenchymal precursor cells (MPCs) combined with an osteoconductive scaffold to promote lumbar interbody spine fusion in an ovine model

BACKGROUND

Advances in immunomagnetic cell sorting have enabled isolation and purification of pleuripotent stem cells from marrow aspirates and have expanded stem cell therapies to include allogeneic sources.

PURPOSE

This study aimed to determine the safety and efficacy of allogeneic mesenchymal precursor cells (MPCs) combined with an osteoconductive scaffold in lumbar interbody spinal fusion using an ovine model.

STUDY DESIGN

Thirty-two skeletally mature ewes underwent a single-level interbody fusion procedure using a Polyetheretherketone fusion cage supplemented with either iliac crest autograft (AG) or an osteconductive scaffold (Mastergraft Matrix, Medtronic, Memphis, TN, USA) with 2.5×10(6) MPCs, 6.25×10(6) MPCs, or 12.5×10(6) MPCs.

METHODS

Plain radiographs and computed tomography scans were scored for bridging bone at multiple points during healing and at necropsy. The biomechanical competency of fusion was scored by manual palpation and quantified using functional radiographs at necropsy. Postnecropsy histopathology and histomorphometric analysis assessed the local response to MPC treatment and quantified the volume and connectivity of newly formed bridging bone. Safety was assessed by serum biochemistry, hematology, and organ histopathology.

RESULTS

Mesenchymal precursor cell treatment caused no adverse systemic or local tissue responses. All analyses indicated MPCs combined with an osteoconductive scaffold achieved similar or better fusion success as AG treatment after 16 weeks, and increasing the MPC dose did not enhance fusion. Manual palpation of the fusion site indicated more than 75% of MPC-treated and 65% of AG-treated animals achieved rigid fusion, which was corroborated with functional radiography. Computed tomography fusion scores indicated all animals in the MPC- and AG-treatment groups were fused at 16 weeks, yet X-ray scores indicated only 67% of the AG-treated animals were fused. Histomorphometry analyses showed equivalent outcomes for fusion connectivity and bony fusion area for MPC- and AG-treated groups. Approximately 6% residual graft material remained in the MPC-treated fusion sites at 16 weeks.

CONCLUSIONS

Adult allogeneic MPCs delivered using an osteoconductive scaffold were both safe and efficacious in this ovine spine interbody fusion model. These results support the use ofallogeneic MPCs as an alternative to AG for lumbar interbody spinal fusion procedures.

A Detailed Assessment of Varying Ejection Rate on Delivery Efficiency of Mesenchymal Stem Cells Using Narrow-Bore Needles

As the number of clinical trials exploring cell therapy rises, a thorough understanding of the limits of cell delivery is essential. We used an extensive toolset comprising various standard and multiplex assays for the assessment of cell delivery postejection. Primary human mesenchymal stem cell (hMSC) suspensions were drawn up into 100-µl Hamilton syringes with 30- and 34-gauge needles attached, before being ejected at rates ranging from 10 to 300 µl/minute. Effects of ejection rate, including changes in viability, apoptosis, senescence, and other key aspects of cellular health, were evaluated. Ejections at slower flow rates resulted in a lower percentage of the cell dose being delivered, and apoptosis measurements of samples ejected at 10 µl/minute were significantly higher than control samples. Immunophenotyping also revealed significant downregulation of CD105 expression in samples ejected at 10 µl/minute (p < .05). Differentiation of ejected hMSCs was investigated using qualitative markers of adipogenesis, osteogenesis, and chondrogenesis, which revealed that slower ejection rates exerted a considerable effect upon the differentiation capacity of ejected cells, thereby possibly influencing the success of cell-based therapies. The findings of this study demonstrate that ejection rate has substantial impact on the percentage of cell dose delivered and cellular health postejection.

Remote transplantation of mesenchymal stem cells protects the heart against ischemia-reperfusion injury

Cardioprotection can be evoked through extracardiac approaches. This prompted us to investigate whether remote transplantation of stem cells confers protection of the heart against ischemic injury. The cardioprotective effect of subcutaneous transplantation of naïve versus heme oxygenase-1 (HMOX-1)-overexpressing mouse mesenchymal stem cells (MSC) to mice was investigated in hearts subjected to ischemia-reperfusion in a Langendorff perfusion system. Mice were transplanted into the interscapular region with naïve or HMOX-1 transfected MSC isolated from transgenic luciferase reporter mice and compared to sham-treated animals. The fate of transplanted cells was followed by in vivo bioluminescence imaging, revealing that MSC proliferated, but did not migrate detectably from the injection site. Ex vivo analysis of the hearts showed that remote transplantation of mouse adipose-derived MSC (mASC) resulted in smaller infarcts and improved cardiac function after ischemia-reperfusion compared to sham-treated mice. Although HMOX-1 overexpression conferred cytoprotective effects on mASC against oxidative stress in vitro, no additive beneficial effect of HMOX-1 transfection was noted on the ischemic heart. Subcutaneous transplantation of MSC also improved left ventricular function when transplanted in vivo after myocardial infarction. Plasma analysis and gene expression profile of naïve- and HMOX-1-mASC after transplantation pointed toward pentraxin 3 as a possible factor involved in the remote cardioprotective effect of mASC. These results have significant implications for understanding the behavior of stem cells after transplantation and development of safe and noninvasive cellular therapies with clinical applications. Remote transplantation of MSC can be considered as an alternative procedure to induce cardioprotection.

Mesenchymal stromal cells overexpressing vascular endothelial growth factor in ovine myocardial infarction

Mesenchymal stromal cells (MSCs) are cardioprotective in acute myocardial infarction (AMI). Besides, we have shown that intramyocardial injection of plasmid-VEGF(165) (pVEGF) in ovine AMI reduces infarct size and improves left ventricular (LV) function. We thus hypothesized that MSCs overexpressing VEGF(165) (MSCs-pVEGF) would afford greater cardioprotection than non-modified MSCs or pVEGF alone. Sheep underwent an anteroapical AMI and, 1 week later, received intramyocardial MSCs-pVEGF in the infarct border. One month post treatment, infarct size (magnetic resonance) decreased by 31% vs pre-treatment. Of note, myocardial salvage occurred predominantly at the subendocardium, the myocardial region displaying the largest contribution to systolic performance. Consistently, LV ejection fraction recovered to almost its baseline value because of marked decrease in end-systolic volume. None of these effects were observed in sheep receiving non-transfected MSCs or pVEGF. Although myocardial retention of MSCs decreased steeply over time, the treatment induced significant capillary and arteriolar proliferation, which reduced subendocardial fibrosis. We conclude that in ovine AMI, allogeneic VEGF-overexpressing MSCs induce subendocardial myocardium salvage through microvascular proliferation, reducing infarct size and improving LV function more than non-transfected MSCs or the naked plasmid. Importantly, the use of a plasmid rather than a virus allows for repeated treatments, likely needed in ischemic heart disease.

Concise review: the surface markers and identity of human mesenchymal stem cells

The concept of mesenchymal stem cells (MSCs) is becoming increasingly obscure due to the recent findings of heterogeneous populations with different levels of stemness within MSCs isolated by traditional plastic adherence. MSCs were originally identified in bone marrow and later detected in many other tissues. Currently, no cloning based on single surface marker is capable of isolating cells that satisfy the minimal criteria of MSCs from various tissue environments. Markers that associate with the stemness of MSCs await to be elucidated. A number of candidate MSC surface markers or markers possibly related to their stemness have been brought forward so far, including Stro-1, SSEA-4, CD271, and CD146, yet there is a large difference in their expression in various sources of MSCs. The exact identity of MSCs in vivo is not yet clear, although reports have suggested they may have a fibroblastic or pericytic origin. In this review, we revisit the reported expression of surface molecules in MSCs from various sources, aiming to assess their potential as MSC markers and define the critical panel for future investigation. We also discuss the relationship of MSCs to fibroblasts and pericytes in an attempt to shed light on their identity in vivo.

Mesenchymal stem cell insights: prospects in cardiovascular therapy

Ischemic heart damage usually triggers cardiomyopathological remodeling and fibrosis, thus promoting the development of heart functional failure. Mesenchymal stem cells (MSCs) are a heterogeneous group of cells in culture, with multipotent and hypoimmunogenic characters to aid tissue repair and avoid immune responses, respectively. Numerous experimental findings have proven the feasibility, safety, and efficiency of MSC therapy for cardiac regeneration. Despite that the exact mechanism remains unclear, the therapeutic ability of MSCs to treat ischemia heart diseases has been tested in phase I/II clinical trials. Based on encouraging preliminary findings, MSCs might become a potentially efficacious tool in the therapeutic options available to treat ischemic and nonischemic cardiovascular disorders. The molecular mechanism behind the efficacy of MSCs on promoting engraftment and accelerating the speed of heart functional recovery is still waiting for clarification. It is hypothesized that cardiomyocyte regeneration, paracrine mechanisms for cardiac repair, optimization of the niche for cell survival, and cardiac remodeling by inflammatory control are involved in the interaction between MSCs and the damaged myocardial environment. This review focuses on recent experimental and clinical findings related to cellular cardiomyoplasticity. We focus on MSCs, highlighting their roles in cardiac tissue repair, transdifferentiation, the MSC niche in myocardial tissues, discuss their therapeutic efficacy that has been tested for cardiac therapy, and the current bottleneck of MSC-based cardiac therapies.

The non-coding road towards cardiac regeneration

Our understanding of cardiovascular disease has evolved rapidly, leading to a number of treatments that have improved patient quality of life and mortality rates. However, there is still no cure for heart failure. This has led to the pursuit of cardiac regeneration to prevent, and ultimately cure, this debilitating condition. To this end, several approaches have been proposed, including activation of cardiomyocyte proliferation, activation of endogenous or exogenous stem/progenitor cells, delivery of de novo cardiomyocytes, and in situ direct reprogramming of cardiac fibroblasts. While these different methodologies are currently being intensely investigated, there are still a number of caveats limiting their application in the clinic. Given the emerging regulatory potential of non-coding RNAs for controlling diverse cellular processes, these molecules may offer potential solutions in this pursuit of cardiac regeneration. In this concise review, we discuss the potential role of non-coding RNAs in a variety of different cardiac regenerative approaches.

Mesenchymal precursor cells as adjunctive therapy in recipients of contemporary left ventricular assist devices

BACKGROUND

Allogeneic mesenchymal precursor cells (MPCs) injected during left ventricular assist device (LVAD) implantation may contribute to myocardial recovery. This trial explores the safety and efficacy of this strategy.

METHODS AND RESULTS

In this multicenter, double-blind, sham-procedure controlled trial, 30 patients were randomized (2:1) to intramyocardial injection of 25 million MPCs or medium during LVAD implantation. The primary safety end point was incidence of infectious myocarditis, myocardial rupture, neoplasm, hypersensitivity reaction, and immune sensitization (90 days after randomization). Key efficacy end points were functional status and ventricular function while temporarily weaned from LVAD support (90 days after randomization). Patients were followed up until transplant or 12 months after randomization, whichever came first. Mean age was 57.4 (±13.6) years, mean left ventricular ejection fraction was 18.1%, and 66.7% were destination therapy LVADs. No safety events were observed. Successful temporary LVAD weaning was achieved in 50% of MPC and 20% of control patients at 90 days (P=0.24); the posterior probability that MPCs increased the likelihood of successful weaning was 93%. At 90 days, 3 deaths (30%) occurred in control patients, and none occurred in MPC patients. Mean left ventricular ejection fraction after successful wean was 24.0% (MPC=10) and 22.5% (control=2; P=0.56). At 12 months, 30% of MPC patients and 40% of control patients were successfully temporarily weaned from LVAD support (P=0.69), and 6 deaths (30%) occurred in MPC patients. Donor-specific HLA sensitization developed in 2 MPC and 3 control patients and resolved by 12 months.

CONCLUSIONS

In this preliminary trial, administration of MPCs appeared to be safe, and there was a potential signal of efficacy. Future studies will evaluate the potential for higher or additional doses to enhance the ability to wean LVAD recipients off support.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT01442129.

The therapeutic potential of bone marrow-derived mesenchymal stromal cells on hepatocellular carcinoma

Mesenchymal stromal cells (MSCs) are more often obtained from adult and extraembryonic tissues, with the latter sources being likely better from a therapeutic perspective. MSCs show tropism towards inflamed or tumourigenic sites. Mechanisms involved in MSC recruitment into tumours are comprehensively analysed, including chemoattractant signalling axes, endothelial adhesion and transmigration. In addition, signals derived from hepatocellular carcinoma (HCC) tumour microenvironment and their influence in MSC tropism and tumour recruitment are dissected, as well as the present controversy regarding their influence on tumour growth and/or metastasis. Finally, evidences available on the use of MSCs and other selected progenitor/stem cells as vehicles of antitumourigenic genes are discussed. A better knowledge of the mechanisms involved in progenitor/stem cell recruitment to HCC tumours is proposed in order to enhance their tumour targeting which may result in improvements in cell-based gene therapy strategies.

Allogeneic mesenchymal progenitor cells for posterolateral lumbar spine fusion in sheep

BACKGROUND CONTEXT

Osteoconductive porous ceramic bone graft materials supplemented with mesenchymal precursor cells (MPC) derived from autologous bone marrow aspirates have been shown to stimulate successful interbody and posterolateral spine fusion in preclinical models. Recent advances in immunomagnetic cell sorting have enabled purification and isolation of pluripotent stem cells from marrow aspirates and have expanded stem cell technology to allogeneic cell sources. Allogeneic MPC technology combined with appropriate synthetic biomaterial carriers could provide both the osteogenic and osteoconductive components needed for successful posterolateral spine fusion without the need for autologous bone harvest or expensive recombinant protein technology.

PURPOSE

To determine the safety and efficacy of a hydroxyapatite:tricalcium phosphate graft material supplemented with allogeneic mesenchymal precursor cells in posterolateral lumbar spine fusion using an ovine model.

STUDY DESIGN

Skeletally mature ewes underwent single-level instrumented posterolateral lumbar spine fusion using either autograft (AG), hydroxyapatite:tricalcium phosphate carrier (CP), or CP supplemented with allogeneic mesenchymal progenitor cells (MPCs). Three doses of MPCs were evaluated: 25 × 10⁶ cells (low dose, LD), 75 × 10⁶ cells (mid dose, MD), and 225 × 10⁶ cell (high dose, HD). Animals survived for either 4 or 9 months.

METHODS

Plain radiographs were acquired and scored for bridging bone at regular intervals during healing to monitor fusion development. Hematology, coagulation, and serum chemistry were monitored at regular intervals throughout the study to monitor animal health. After necropsy, computed tomography, high-resolution radiography, biomechanical testing, organ pathology, bone histopathology, and bone histomorphometry were conducted to monitor the safety and ascertain the efficacy of MPC treatment.

RESULTS

MPC treatment in this spine fusion model resulted in no observed adverse systemic or local tissue responses. Radiographically, fusion scores for MPC-treated animals were uniformly higher compared with those treated with carrier alone (CP) after 3 months and continued the same trend throughout 9 month of healing. Quantitative computed tomography confirmed better connectivity of the fusion for MPC treatment groups compared with CP. Biomechanical analyses were not able to differentiate between treatment groups. Histomorphometry results confirmed radiographic and quantitative computed tomography results; cell-supplemented treatment groups and autograft had equivalent amounts of bone within the fusion mass and less bony fusion tissue was found within the fusion mass in specimens from the CP treatment group. No conclusive effects of cell dose of fusion efficacy were noted.

CONCLUSIONS

Adult allogeneic mesenchymal precursor cells delivered via a hydroxyapatite:tricalcium phosphate carrier were both safe and efficacious in this ovine spine fusion model. Results from this preclinical study support that allogeneic mesenchymal precursor cells produced fusion efficacy similar to that achieved using iliac crest autograft, thereby providing a safe and viable option to achieve successful posterolateral spine fusion.

Optimization of the cardiovascular therapeutic properties of mesenchymal stromal/stem cells-taking the next step

Despite current treatment options, cardiac failure is associated with significant morbidity and mortality highlighting a compelling clinical need for novel therapeutic approaches. Based on promising pre-clinical data, stem cell therapy has been suggested as a possible therapeutic strategy. Of the candidate cell types evaluated, mesenchymal stromal/stem cells (MSCs) have been widely evaluated due to their ease of isolation and ex vivo expansion, potential allogeneic utility and capacity to promote neo-angiogenesis and endogenous cardiac repair. However, the clinical application of MSCs for mainstream cardiovascular use is currently hindered by several important limitations, including suboptimal retention and engraftment and restricted capacity for bona fide cardiomyocyte regeneration. Consequently, this has prompted intense efforts to advance the therapeutic properties of MSCs for cardiovascular disease. In this review, we consider the scope of benefit from traditional plastic adherence-isolated MSCs and the lessons learned from their conventional use in preclinical and clinical studies. Focus is then given to the evolving strategies aimed at optimizing MSC therapy, including discussion of cell-targeted techniques that encompass the preparation, pre-conditioning and manipulation of these cells ex vivo, methods to improve their delivery to the heart and innovative substrate-directed strategies to support their interaction with the host myocardium.

Catheter-Based Endomyocardial Delivery of Mesenchymal Precursor Cells Using 3D Echo Guidance Improves Cardiac Function in a Chronic Myocardial Injury Ovine Model

The administration of bone marrow-derived stem cells may provide a new treatment option for patients with heart failure. Transcatheter cell injection may require multi-imaging modalities to optimize delivery. This study sought to evaluate whether endomyocardial injection of mesenchymal precursor cells (MPCs) could be guided by real-time 3D echocardiography (RT3DE) in treating chronic, postinfarction (MI) left ventricular (LV) dysfunction in sheep. Four weeks after induction of an anterior wall myocardial infarction in 39 sheep, allogeneic MPCs in doses of either 25 × 106 ( n = 10), 75 × 106 ( n = 9), or 225 × 106 ( n = 10) cells or nonconditioned control media ( n = 10) were administered intramyocardially into infarct and border zone areas using a catheter designed for combined fluoroscopic and RT3DE-guided injections. LV function was assessed before and after injection. Infarct dimension and vascular density were evaluated histologically. RT3DE-guided injection procedures were safe. Compared to controls, the highest dose MPC treatment led to increments in ejection fraction (3±3% in 225M MPCs vs. −5±4% in the control group, p < 0.01) and wall thickening in both infarct (4±4% in 225M MPCs vs. −3±6% in the control group, p = 0.02) and border zones (4±6% in 225M MPCs vs. −8±9% in the control group, p = 0.01). Histology analysis demonstrated significantly higher arteriole density in the infarct and border zones in the highest dose MPC-treated animals compared to the lower dose or control groups. Endomyocardial implantation of MPCs under RT3DE guidance was safe and without observed logistical obstacles. Significant increases in LV performance (ejection fraction and wall thickening) and neovascularization resulted from this technique, and so this technique has important implications for treating patients with postischemic LV dysfunction.

Recent advances in mesenchymal stem cell immunomodulation: the role of microvesicles

Mesenchymal stem cells are the most widely used cell phenotype for therapeutic applications, the main reasons being their well-established abilities to promote regeneration of injured tissues and to modulate immune responses. Efficacy was reported in the treatment of several animal models of inflammatory and autoimmune diseases and, in clinical settings, for the management of disorders such as GVHD, systemic lupus erythematosus, multiple sclerosis, and inflammatory bowel disease. The effects of mesenchymal stem cells are believed to be largely mediated by paracrine signals, and several secreted molecules have been identified as contributors to the net biological effect. Recently, it has been recognized that bioactive molecules can be shuttled from cell to cell packed in microvesicles, tiny portions of cytoplasm surrounded by a membrane. Coding and noncoding RNAs are also carried in such microvesicles, transferring relevant biological activity to target cells. Several reports indicate that the regenerative effect of mesenchymal stem cells can be reproduced by microvesicles isolated from their culture medium. More recent evidence suggests that the immunomodulatory effects of mesenchymal stem cells are also at least partially mediated by secreted microvesicles. These findings allow better understanding of the mechanisms involved in cell-to-cell interaction and may have interesting implications for the development of novel therapeutic tools in place of the parent cells.

Impact of timing and dose of mesenchymal stromal cell therapy in a preclinical model of acute myocardial infarction

BACKGROUND

Although mesenchymal stem/stromal cells (MSC) have shown therapeutic promise after myocardial infarction (MI), the impact of cell dose and timing of intervention remains uncertain. We compared immediate and deferred administration of 2 doses of MSC in a rat model of MI.

METHODS AND RESULTS

Sprague-Dawley rats were used. Allogeneic prospectively isolated MSC ("low" dose 1 × 10(6) or "high" dose 2 × 10(6) cells) were delivered by transepicardial injection immediately after MI ("early-low," "early-high"), or 1 week later ("late-low," "late-high"). Control subjects received cryopreservant solution alone. Left ventricular dimensions and ejection fraction (EF) were assessed by cardiac magnetic resonance. All 4 MSC-treatment cohorts demonstrated higher EF than control animals 4 weeks after MI (P values <.01 to <.0001), with function most preserved in the early-high group (absolute reduction in EF from baseline: control 39.1 ± 1.7%, early-low 26.5 ± 3.2%, early-high 7.9 ± 2.6%, late-low 19.6 ± 3.5%, late-high 17.9 ± 4.0%). Cell treatment also attenuated left ventricular dilatation and fibrosis and augmented left ventricular mass, systolic wall thickening (SWT), and microvascular density. Although early intervention selectively increased SWT and vascular density in the infarct territory, delayed treatment caused greater benefit in remote (noninfarct) myocardium. All outcomes demonstrated dose dependence for early MSC treatment, but not for later cell administration.

CONCLUSIONS

The nature and magnitude of benefit from MSC after acute MI is strongly influenced by timing of cell delivery, with dose dependence most evident for early intervention. These novel insights have potential implications for cell therapy after MI in human patients.

Hypoxic culture conditions as a solution for mesenchymal stem cell based regenerative therapy

Cell-based regenerative therapies, based on in vitro propagation of stem cells, offer tremendous hope to many individuals suffering from degenerative diseases that were previously deemed untreatable. Due to the self-renewal capacity, multilineage potential, and immunosuppressive property, mesenchymal stem cells (MSCs) are considered as an attractive source of stem cells for regenerative therapies. However, poor growth kinetics, early senescence, and genetic instability during in vitro expansion and poor engraftment after transplantation are considered to be among the major disadvantages of MSC-based regenerative therapies. A number of complex inter- and intracellular interactive signaling systems control growth, multiplication, and differentiation of MSCs in their niche. Common laboratory conditions for stem cell culture involve ambient O₂ concentration (20%) in contrast to their niche where they usually reside in 2–9% O₂. Notably, O₂ plays an important role in maintaining stem cell fate in terms of proliferation and differentiation, by regulating hypoxia-inducible factor-1 (HIF-1) mediated expression of different genes. This paper aims to describe and compare the role of normoxia (20% O₂) and hypoxia (2–9% O₂) on the biology of MSCs. Finally it is concluded that a hypoxic environment can greatly improve growth kinetics, genetic stability, and expression of chemokine receptors during in vitro expansion and eventually can increase efficiency of MSC-based regenerative therapies.

A transgenic tri-modality reporter mouse

Transgenic mouse with a stably integrated reporter gene(s) can be a valuable resource for obtaining uniformly labeled stem cells, tissues, and organs for various applications. We have generated a transgenic mouse model that ubiquitously expresses a tri-fusion reporter gene (fluc2-tdTomato-ttk) driven by a constitutive chicken β-actin promoter. This “Tri-Modality Reporter Mouse” system allows one to isolate most cells from this donor mouse and image them for bioluminescent (fluc2), fluorescent (tdTomato), and positron emission tomography (PET) (ttk) modalities. Transgenic colonies with different levels of tri-fusion reporter gene expression showed a linear correlation between all three-reporter proteins (R²=0.89 for TdTomato vs Fluc, R²=0.94 for Fluc vs TTK, R²=0.89 for TdTomato vs TTK) in vitro from tissue lysates and in vivo by optical and PET imaging. Mesenchymal stem cells (MSCs) isolated from this transgenics showed high level of reporter gene expression, which linearly correlated with the cell numbers (R²=0.99 for bioluminescence imaging (BLI)). Both BLI (R²=0.93) and micro-PET (R²=0.94) imaging of the subcutaneous implants of Tri-Modality Reporter Mouse derived MSCs in nude mice showed linear correlation with the cell numbers and across different imaging modalities (R²=0.97). Serial imaging of MSCs transplanted to mice with acute myocardial infarction (MI) by intramyocardial injection exhibited significantly higher signals in MI heart at days 2, 3, 4, and 7 (p<0.01). MSCs transplanted to the ischemic hindlimb of nude mice showed significantly higher BLI and PET signals in the first 2 weeks that dropped by 4^th week due to poor cell survival. However, laser Doppler perfusion imaging revealed that blood circulation in the ischemic limb was significantly improved in the MSCs transplantation group compared with the control group. In summary, this mouse can be used as a source of donor cells and organs in various research areas such as stem cell research, tissue engineering research, and organ transplantation.

Comparative study of three types of polymer materials co-cultured with bone marrow mesenchymal stem cells for use as a myocardial patch in cardiomyocyte regeneration

The purpose of this study was to investigate the most suitable polymer material for supporting stem cell growth as a myocardial patch. After cell isolation and expansion of mouse bone marrow mesenchymal stem cells (BMSC), the cells were induced to differentiate into cardiomyocytes with 5-azacytidine to determine their differentiation potential. BMSCs were also seeded onto three types of polymer material film, including polyurethane (PU), 3-hydroxybutyrate-co-4-hydroxybutyrate [P(3HB-co-4HB)], and polypropylene carbonate (PPC). The results revealed that cell numbers were more abundant on both the PU and P(3HB-co-4HB) material surfaces. Conversely, the surface of PPC was smooth with only cell lysate debris observed. The average cell counts were as follows: 143.78 ± 38.38 (PU group), 159.50 ± 33.07 [P(3HB-co-4HB) group], and 1.40 ± 0.70 (PPC group). There was no statistically significant difference in cell numbers between the PU and P(3HB-co-4HB) groups. A statistically significant difference was identified between the PPC group and both the PU (P1) and P(3HB-co-4HB) groups (P2). Polymer biomaterial patches composed of PU and P(3HB-co-4HB) permit good stem cell growth. P(3HB-co-4HB) has the potential for development as a clinical alternative to current treatment methods for the regeneration of cardiomyocytes in patients with myocardial infarction.

Intracoronary infusion of allogeneic mesenchymal precursor cells directly after experimental acute myocardial infarction reduces infarct size, abrogates adverse remodeling, and improves cardiac function

RATIONALE

Mesenchymal precursor cells (MPCs) are a specific Stro-3+ subpopulation of mesenchymal stem cells isolated from bone marrow. MPCs exert extensive cardioprotective effects, and are considered to be immune privileged.

OBJECTIVE

This study assessed the safety, feasibility, and efficacy of intracoronary delivery of allogeneic MPCs directly after acute myocardial infarction in sheep.

METHODS AND RESULTS

Initially, intracoronary delivery conditions were optimized in 20 sheep. These conditions were applied in a randomized study of 68 sheep with an anterior acute myocardial infarction. Coronary flow was monitored during MPC infusion, and cardiac function was assessed using invasive hemodynamics and echocardiography at baseline and during 8 weeks follow-up. Coronary flow remained within thrombolysis in myocardial infarction III definitions in all sheep during MPC infusion. Global left ventricular ejection fraction as measured by pressure-volume loop analysis deteriorated in controls to 40.7±2.6% after 8 weeks. In contrast, MPC treatment improved cardiac function to 52.8±0.7%. Echocardiography revealed significant improvement of both global and regional cardiac functions. Infarct size decreased by 40% in treated sheep, whereas infarct and border zone thickness were enhanced. Left ventricular adverse remodeling was abrogated by MPC therapy, resulting in a marked reduction of left ventricular volumes. Blood vessel density increased by >50% in the infarct and border areas. Compensatory cardiomyocyte hypertrophy was reduced in border and remote segments, accompanied by reduced collagen deposition and apoptosis. No microinfarctions in remote myocardial segments or histological abnormalities in unrelated organs were found.

CONCLUSIONS

Intracoronary infusion of allogeneic MPCs is safe, feasible, and markedly effective in a large animal model of acute myocardial infarction.

Factors secreted by mesenchymal stem cells and endothelial progenitor cells have complementary effects on angiogenesis in vitro

Stem cell-based therapy for myocardial regeneration has reported several functional improvements that are attributed mostly to the paracrine effects stimulating angiogenesis and cell survival. This study was conducted to comparatively evaluate the potential of factors secreted by mesenchymal stem cells (MSCs) in normoxic and hypoxic conditions to promote tissue repair by sustaining endothelial cell (EC) adhesion and proliferation and conferring protection against apoptosis. To this aim, a conditioned medium (CM) was generated from MSCs after 24-h incubation in a serum-free normal or hypoxic environment. MSCs exhibited resistance to hypoxia, which induced increased secretion of vascular endothelial growth factor (VEGF) and decreased levels of other cytokines, including stromal-derived factor-1 (SDF). The CM derived from normal (nMSC-CM) and hypoxic cells (hypMSC-CM) induced similar protective effects on H9c2 cells in hypoxia. Minor differences were noticed in the potential of normal versus hypoxic CM to promote angiogenesis, which were likely connected to SDFα and VEGF levels: the nMSC-CM was more effective in stimulating EC migration, whereas the hypMSC-CM had an enhanced effect on EC adhesion. However, the factors secreted by MSCs in normoxic or hypoxic conditions supported adhesion, but not proliferation, of ECs in vitro, as revealed by impedance-based dynamic assessments. Surprisingly, factors secreted by other stem/progenitor cells, such as endothelial progenitor cells (EPCs), had complementary effects to the MSC-CM. Thus, the EPC-CM, in either a normal or hypoxic environment, supported EC proliferation, but did not sustain EC adhesion. Combined use of the MSC-CM and EPC-CM promoted both EC adhesion and proliferation, suggesting that the local angiogenesis at the site of ischemic injury might be better stimulated by simultaneous releasing of factors secreted by multiple stem/progenitor cell populations.

Interaction between marrow-derived human mesenchymal stem cells and peripheral blood mononuclear cells in endothelial cell differentiation

BACKGROUND AND AIMS

In adult connective tissues, mesenchymal stem cells (MSCs) play a key role in normal tissue turnover and repair. MSCs can participate in these processes not only through proliferation and differentiation but also through paracrine/autocrine functions. These characteristics make MSCs the optimal target in the development of cell-based therapies. This study describes a novel interaction between human MSC and blood mononuclear cells (MNCs), resulting in formation of blood vessel-like structures.

MATERIALS AND METHODS

Human marrow-derived MSCs and peripheral blood MNCs were co-cultured in monolayer cultures as well as in bovine collagen sponge up to 20 days. No exogenously supplied growth factors were applied. Morphological changes and formations of three dimensional structures were detected by light microscopy. The process was further stu-died for the expression of different endothelial cell markers. The expression of PECAM-1 and endoglin was studied by immunohistochemistry and the expression of vascular endothelial growth factor receptors 1 and 2 using quantitative real time PCR.

RESULTS

In co-cultures of human MSCs and MNCs, the previously nonadherent cells attached and started to elongate and formed tube-like structures within one week. At day 10, elongated PECAM-1 and endoglin expressing cells were detected in co-cultures. At day 20, PECAM-1 and endoglin-positive vessel-like structures were observed. VEGFR1 was up-regulated in co-cultures after 10 days, and expression levels increased with time. No PECAM-1, endoglin or VEGFR1 expressing cells were discovered in MSC-cultures without MNCs at any time point.

CONCLUSIONS

This study demonstrates induction of endothelial differentiation in co-cultures of human MSCs and MNCs, indicating a mechanism by which local application of MSCs could induce angiogenesis in vivo.