Pretreating mesenchymal stem cells with interleukin-1β and transforming growth factor-β synergistically increases vascular endothelial growth factor production and improves mesenchymal stem cell-mediated myocardial protection after acute ischemia

Unlocking the Mysteries, Bridging the Gap, and Unveiling the Multifaceted Potential of Stem Cell Therapy for Cardiac Tissue Regeneration: A Narrative Review of Current Literature, Ethical Challenges, and Future Perspectives

Revolutionary advancements in regenerative medicine have brought stem cell therapy to the forefront, offering promising prospects for the regeneration of ischemic cardiac tissue. Yet, its full efficacy, safety, and role in treating ischemic heart disease (IHD) remain limited. This literature review explores the intricate mechanisms underlying stem cell therapy. Furthermore, we unravel the innovative approaches employed to bolster stem cell survival, enhance differentiation, and seamlessly integrate them within the ischemic cardiac tissue microenvironment. Our comprehensive analysis uncovers how stem cells enhance cell survival, promote angiogenesis, and modulate the immune response. Stem cell therapy harnesses a multifaceted mode of action, encompassing paracrine effects and direct cell replacement. As our review progresses, we underscore the imperative for standardized protocols, comprehensive preclinical and clinical studies, and careful regulatory considerations. Lastly, we explore the integration of tissue engineering and genetic modifications, envisioning a future where stem cell therapy reigns supreme in regenerative medicine.

Canine bone marrow peri-adipocyte cells could therapeutically benefit acute spinal cord injury through migration and secretion of hepatocyte growth factor to inflammatory milieu

Spinal cord injury (SCI) is a common neurological disorder in dogs. A secondary injury that occurs in the acute phase causes expansion of inflammation, resulting in lesion extension and further loss of function. Mesenchymal stem cells (MSCs) have trophic effects and the ability to migrate toward injured tissues; therefore, MSC-based therapy is considered promising for the treatment of canine SCI. We recently reported that bone marrow peri-adipocyte cells (BM-PACs) can be obtained from canine bone marrow and have stem cell potential superior to that of conventional bone marrow MSCs (BMMSCs). However, their therapeutic potential for SCI have been still unknow. Here, we first evaluated the ability of BM-PACs to secrete hepatocyte growth factor (HGF) and their migration ability toward inflammatory milieu in vitro. BM-PACs can secrete HGF in response to pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α and IL-1β, and exhibit migration ability toward these cytokines. Next, BM-PACs were intravenously administered into nude mice with acute SCI to analyze the homing ability and therapeutic effects of HGF secreted by BM-PACs. BM-PACs homed to the injured spinal cord, where the HGF expression level increased 7 days after administration. Intravenous administration of BM-PACs induced functional recovery and pathological improvement, indicated by less demyelinating area, more preserved axons, and less glial scar formation compared with the mice only received vehicle. These findings suggest that the intravenous administration of BM-PACs can be a novel therapeutic intervention for acute canine SCI.

Peripheral blood monocytes as a therapeutic target for marrow stromal cells in stroke patients

Background

Systemic administration of marrow stromal cells (MSCs) leads to the release of a broad range of factors mediating recovery in rodent stroke models. The release of these factors could depend on the various cell types within the peripheral blood as they contact systemically administered MSCs. In this study, we assessed the immunomodulatory interactions of MSCs with peripheral blood derived monocytes (Mϕ) collected from acute stroke patients.

Methods

Peripheral blood from stroke patients was collected at 5–7 days (N = 5) after symptom onset and from age-matched healthy controls (N = 5) using mononuclear cell preparation (CPT) tubes. After processing, plasma and other cellular fractions were removed, and Mϕ were isolated from the mononuclear fraction using CD14 microbeads. Mϕ were then either cultured alone or co-cultured with MSCs in a trans-well cell-culture system. Secretomes were analyzed after 24 h of co-cultures using a MAGPIX reader.

Results

Our results show that there is a higher release of IFN-γ and IL-10 from monocytes isolated from peripheral blood at day 5–7 after stroke compared with monocytes from healthy controls. In trans-well co-cultures of MSCs and monocytes isolated from stroke patients, we found statistically significant increased levels of IL-4 and MCP-1, and decreased levels of IL-6, IL-1β, and TNF-α. Addition of MSCs to monocytes increased the secretions of Fractalkine, IL-6, and MCP-1, while the secretions of TNF-α decreased, as compared to the secretions from monocytes alone. When MSCs were added to monocytes from stroke patients, they decreased the levels of IL-1β, and increased the levels of IL-10 significantly more as compared to when they were added to monocytes from control patients.

Conclusion

The systemic circulation of stroke patients may differentially interact with MSCs to release soluble factors integral to their paracrine mechanisms of benefit. Our study finds that the effect of MSCs on Mϕ is different on those derived from stroke patients blood as compared to healthy controls. These findings suggest immunomodulation of peripheral immune cells as a therapeutic target for MSCs in patients with acute stroke.

Paracrine Factors Released by Stem Cells of Mesenchymal Origin and their Effects in Cardiovascular Disease: A Systematic Review of Pre-clinical Studies

Mesenchymal stem cell (MSC) therapy has gained significant traction in the context of cardiovascular repair, and have been proposed to exert their regenerative effects via the secretion of paracrine factors. In this systematic review, we examined the literature and consolidated available evidence for the “paracrine hypothesis”. Two Ovid SP databases were searched using a strategy encompassing paracrine mediated MSC therapy in the context of ischemic heart disease. This yielded 86 articles which met the selection criteria for inclusion in this study. We found that the MSCs utilized in these articles were primarily derived from bone marrow, cardiac tissue, and adipose tissue. We identified 234 individual protective factors across these studies, including VEGF, HGF, and FGF2; which are proposed to exert their effects in a paracrine manner. The data collated in this systematic review identifies secreted paracrine factors that could decrease apoptosis, and increase angiogenesis, cell proliferation, and cell viability. These included studies have also demonstrated that the administration of MSCs and indirectly, their secreted factors can reduce infarct size, and improve left ventricular ejection fraction, contractility, compliance, and vessel density. Furthering our understanding of the way these factors mediate repair could lead to the identification of therapeutic targets for cardiac regeneration.

New Approaches for Enhancement of the Efficacy of Mesenchymal Stem Cell-Derived Exosomes in Cardiovascular Diseases

Cardiovascular diseases (CVDs) remain a major health concern worldwide, where mesenchymal stem cells (MSCs) therapy gives great promise in their management through their regenerative and paracrine actions. In recent years, many studies have shifted from the use of transplanted stem cells to their secreted exosomes for the management of various CVDs and cardiovascular-related diseases including atherosclerosis, stroke, myocardial infarction, heart failure, peripheral arterial diseases, and pulmonary hypertension. In different models, MSC-derived exosomes have shown beneficial outcomes similar to cell therapy concerning regenerative and neovascular actions in addition to their anti-apoptotic, anti-remodeling, and anti-inflammatory actions. Compared with their parent cells, exosomes have also demonstrated several advantages, including lower immunogenicity and no risk of tumor formation. However, the maintenance of stability and efficacy of exosomes after in vivo transplantation is still a major concern in their clinical application. Recently, new approaches have been developed to enhance their efficacy and stability including their preconditioning before transplantation, use of genetically modified MSC-derived exosomes, or their utilization as a targeted drug delivery system. Herein, we summarized the use of MSC-derived exosomes as therapies in different CVDs in addition to recent advances for the enhancement of their efficacy in these conditions.

Biocompatible reduced graphene oxide stimulated BMSCs induce acceleration of bone remodeling and orthodontic tooth movement through promotion on osteoclastogenesis and angiogenesis

We has synthesized the biocompatible gelatin reduced graphene oxide (GOG) in previous research, and in this study we would further evaluate its effects on bone remodeling in the aspects of osteoclastogenesis and angiogenesis so as to verify its impact on accelerating orthodontic tooth movement. The mouse orthodontic tooth movement (OTM) model tests in vivo showed that the tooth movement was accelerated in the GOG local injection group with more osteoclastic bone resorption and neovascularization compared with the PBS injection group. The analysis on the degradation of GOG in bone marrow stromal stem cells (BMSCs) illustrated its good biocompatibility in vitro and the accumulation of GOG in spleen after local injection of GOG around the teeth in OTM model in vivo also didn't influence the survival and life of animals. The co-culture of BMSCs with hematopoietic stem cells (HSCs) or human umbilical vein endothelial cells (HUVECs) in transwell chamber systems were constructed to test the effects of GOG stimulated BMSCs on osteoclastogenesis and angiogenesis in vitro. With the GOG stimulated BMSCs co-culture in upper chamber of transwell, the HSCs in lower chamber manifested the enhanced osteoclastogenesis. Meanwhile, the co-culture of GOG stimulated BMSCs with HUVECs showed a promotive effect on the angiogenic ability of HUVECs. The mechanism analysis on the biofunctions of the GOG stimulated BMSCs illustrated the important regulatory effects of PERK pathway on osteoclastogenesis and angiogenesis. All the results showed the biosecurity of GOG and the biological functions of GOG stimulated BMSCs in accelerating bone remodeling and tooth movement.

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Here we observed the phenomenon of tooth movement acceleration induced by GOG in vivo.

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We hypothesized the pivotal role of BMSCs in the tooth movement acceleration induced by GOG.

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The effects of the GOG stimulated BMSCs on the osteoclastogenesis and angiogenesis were investigated in vitro.

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The potential mechanism of the GOG stimulated BMSCs were also analyzed in vitro and in vivo.

The Vital Roles of Mesenchymal Stem Cells and the Derived Extracellular Vesicles in Promoting Angiogenesis After Acute Myocardial Infarction

Acute myocardial infarction (AMI) is an event of ischemic myocardial necrosis caused by acute coronary artery occlusion, which ultimately leads to a large loss of cardiomyocytes. The prerequisite of salvaging ischemic myocardium and improving cardiac function of patients is to provide adequate blood perfusion in the infarcted area. Apart from reperfusion therapy, it is also urgent and imperative to promote angiogenesis. Recently, growing evidence based on promising preclinical data indicates that mesenchymal stem cells (MSCs) can provide therapeutic effects on AMI by promoting angiogenesis. Extracellular vesicles (EVs), membrane-encapsulated vesicles with complex cargoes, including proteins, nucleic acids, and lipids, can be derived from MSCs and represent part of their functions, so EVs also possess the ability to promote angiogenesis. However, poor control of the survival and localization of MSCs hindered clinical transformation and made scientists start looking for new approaches based on MSCs. Identifying the role of MSCs and their derived EVs in promoting angiogenesis can provide a theoretical basis for improved MSC-based methods, and ultimately promote the clinical treatment of AMI. This review highlights potential proangiogenic mechanisms of transplanted MSCs and the derived EVs after AMI and summarizes the latest literature concerning the novel methods based on MSCs to maximize the angiogenesis capability.

The evaluation of the safety and efficacy of intravenously administered allogeneic multilineage-differentiating stress-enduring cells in a swine hepatectomy model

INTRODUCTION

Multilineage-differentiating stress-enduring (Muse) cells are non-tumorigenic endogenous pluripotent-like cells residing in the bone marrow that exert a tissue reparative effect by replacing damaged/apoptotic cells through spontaneous differentiation into tissue-constituent cells. Post-hepatectomy liver failure (PHLF) is a potentially fatal complication. The main purpose of this study was to evaluate the safety and efficiency of allogeneic Muse cell administration via the portal vein in a swine model of PHLF.

METHODS

Swine Muse cells, collected from swine bone marrow-mesenchymal stem cells (MSCs) as SSEA-3(+) cells, were examined for their characteristics. Then, 1 × 10⁷ allogeneic-Muse cells and allogeneic-MSCs and vehicle were injected via the portal vein in a 70% hepatectomy swine model.

RESULTS

Swine Muse cells exhibited characteristics comparable to previously reported human Muse cells. Compared to the MSC and vehicle groups, the Muse group showed specific homing of the administered cells into the liver, resulting in improvements in the control of hyperbilirubinemia (P = 0.04), prothrombin international normalized ratio (P = 0.05), and suppression of focal necrosis (P = 0.04). Integrated Muse cells differentiated spontaneously into hepatocyte marker-positive cells.

CONCLUSIONS

Allogeneic Muse cell administration may provide a reparative effect and functional recovery in a 70% hepatectomy swine model and thus may contribute to the treatment of PHLF.

Shortening of Overall Orthodontic Treatment Duration with Low-Intensity Pulsed Ultrasound (LIPUS)

The aim of this retrospective clinical study was to determine if there is a reduction in the overall treatment duration in orthodontic patients using low-intensity pulsed ultrasound (LIPUS) and Invisalign SmartTrack® clear aligners. Data were collected from the first thirty-four patients (9 males, 25 females; average age 41.37 ± 15.02) who finished their orthodontic treatment using an intraoral LIPUS device and Invisalign clear aligners in a private clinic. The LIPUS parameters used by patients at home for 20 min/day were: ultrasonic frequency 1.5 MHz, pulse duration 200µs, pulse repetition rate 1 kHz, and spatial average-temporal average intensity 30mW/cm². A control group (11 males, 23 females; average age 31.36 ± 14.41) matching for the same malocclusions was randomly selected from finished treatment cases of the same clinician. The date of first Invisalign attachment placement and first use of LIPUS application was recorded as T0, and the date of retainer delivery was recorded as T1. The treatment duration (T1–T0) and treatment reduction percentage with LIPUS device were collected and analyzed using two-sample t-test in Microsoft Excel. Treatment duration was significantly reduced in the LIPUS group (541.44 ± 192.23 days) compared to control group (1061.05 ± 455.64 days) (p < 0.05). The LIPUS group showed on average 49% reduction in the overall treatment time as compared to the control group. The average compliance of the patients using LIPUS was 66.02%. Patients who used LIPUS showed a clinically significant reduction in the overall orthodontic treatment duration compared to the control group who used Invisalign clear aligners only.

Enhanced Effect of IL-1β-Activated Adipose-Derived MSCs (ADMSCs) on Repair of Intestinal Ischemia-Reperfusion Injury via COX-2-PGE2 Signaling

Adipose-derived mesenchymal stem cells (ADMSCs) have been used for treating tissue injury, and preactivation enhances their therapeutic effect. This study is aimed at investigating the therapeutic effect of activated ADMSCs by IL-1β on the intestinal ischaemia-reperfusion (IR) injury and exploring potential mechanisms. ADMSCs were pretreated with IL-1β in vitro, and activation of ADMSCs was assessed by α-SMA and COX-2 expressions and secretary function. Activated ADMSCs was transplanted into IR-injured intestine in a mouse model, and therapeutic effect was evaluated. In addition, to explore underlying mechanisms, COX-2 expression was silenced to investigate its role in activated ADMSCs for treatment of intestinal IR injury. When ADMSCs were pretreated with 50 ng/ml IL-1β for 24 hr, expressions of α-SMA and COX-2 were significantly upregulated, and secretions of PGE₂, SDF-1, and VEGF were increased. When COX-2 was silenced, the effect of IL-1β treatment was abolished. Activated ADMSCs with IL-1β significantly suppressed inflammation and apoptosis and enhanced healing of intestinal IR injury in mice, and these effects were impaired by COX-2 silencing. The results of RNA sequencing suggested that compared with the IR injury group activated ADMSCs induced alterations in mRNA expression and suppressed the activation of the NF-κB-P65, MAPK-ERK1/2, and PI3K-AKT pathways induced by intestinal IR injury, whereas silencing COX-2 impaired the suppressive effect of activated ADMSCs on these pathway activations induced by IR injury. These data suggested that IL-1β pretreatment enhanced the therapeutic effect of ADMSCs on intestinal IR injury repairing via activating ADMSC COX-2-PGE₂ signaling axis and via suppressing the NF-κB-P65, MAPK-ERK1/2, and PI3K-AKT pathways in the intestinal IR-injured tissue.

State of the art of stem cell therapy for ischaemic cardiomyopathy. Part 2

Ischemic cardiomyopathy is becoming a leading cause of morbidity and mortality in the whole world. Stem cell-based therapy is emerging as a promising option for treatment of ischemic cardiomyopathy. Several stem cell types, including cardiac-derived stem cells, bone marrow-derived stem cells, mesenchymal stem cells, skeletal myoblasts, CD34+ and CD133+ stem cells have been used in clinical trials. Clinical effects mostly depend on transdifferentiation and paracrine factors. One important issue is that a low survival and residential rate of transferred stem cells blocks the effective advances in cardiac improvement. Many other factors associated with the efficacy of cell replacement therapy for ischemic cardiomyopathy mainly including the route of delivery, the type and number of stem cell infusion, the timing of injection, patient's physical conditions, the particular microenvironment onto which the cells are delivered, and clinical conditions remain to be addressed. Here we provide an overview of modern methods of stem cell delivery, types of stem cells and discuss the current state of their therapeutic potential.

Specific, Non-Invasive, and Magnetically Directed Targeting of Magnetic Erythrocytes in Blood Vessels of Mice

OBJECTIVE

Targeting in vivo has been a spotlight for precise medicine. Multiple strategies have been proposed for this issue. However, the efficiency of solely biochemical strategies currently remains to be improved. It has been thought that external field-guided targeting will be a beneficial supplement for the passive and the active targeting.

METHODS

Here, we focused on the magnetic field-guided targeting of magnetized erythrocytes, discovering that a focused magnetic field can direct aggregation of magnetic erythrocytes into a specific region in vivo.

RESULTS

The systematic investigation about the aggregates in cerebral vessels showed that the aggregates were isotropic and able to stably exist for six hours. The formation of cellular aggregates can alter echoing characteristic of the blood vessels meaning the vascular wall became more rigid. If the erythrocytes were repeatedly directed into aggregation in an identical region, a stable plaque of erythrocytes can form, which can mimic the process of thrombosis.

SIGNIFICANCE

We believe these results will be beneficial to the development of novel engineered strategy for targeted delivery of drugs and modeling of vascular diseases.

Enhanced Therapeutic Potential of the Secretome Released from Adipose-Derived Stem Cells by PGC-1α-Driven Upregulation of Mitochondrial Proliferation

Peroxisome proliferator activated receptor λ coactivator 1α (PGC-1α) is a potent regulator of mitochondrial biogenesis and energy metabolism. In this study, we investigated the therapeutic potential of the secretome released from the adipose-derived stem cells (ASCs) transfected with PGC-1α (PGC-secretome). We first generated PGC-1α-overexpressing ASCs by transfecting ASCs with the plasmids harboring the gene encoding PGC-1α. Secretory materials released from PGC-1α-overexpressing ASCs were collected and their therapeutic potential was determined using in vitro (thioacetamide (TAA)-treated AML12 cells) and in vivo (70% partial hepatectomized mice) models of liver injury. In the TAA-treated AML12 cells, the PGC-secretome significantly increased cell viability, promoted expression of proliferation-related markers, such as PCNA and p-STAT, and significantly reduced the levels of reactive oxygen species (ROS). In the mice, PGC-secretome injections significantly increased liver tissue expression of proliferation-related markers more than normal secretome injections did (p < 0.05). We demonstrated that the PGC-secretome does not only have higher antioxidant and anti-inflammatory properties, but also has the potential of significantly enhancing liver regeneration in both in vivo and in vitro models of liver injury. Thus, reinforcing the mitochondrial antioxidant potential by transfecting ASCs with PGC-1α could be one of the effective strategies to enhance the therapeutic potential of ASCs.

Immunoregulatory mechanisms of mesenchymal stem and stromal cells in inflammatory diseases

Mesenchymal stem cells (MSCs; also referred to as mesenchymal stromal cells) have attracted much attention for their ability to regulate inflammatory processes. Their therapeutic potential is currently being investigated in various degenerative and inflammatory disorders such as Crohn's disease, graft-versus-host disease, diabetic nephropathy and organ fibrosis. The mechanisms by which MSCs exert their therapeutic effects are multifaceted, but in general, these cells are thought to enable damaged tissues to form a balanced inflammatory and regenerative microenvironment in the presence of vigorous inflammation. Studies over the past few years have demonstrated that when exposed to an inflammatory environment, MSCs can orchestrate local and systemic innate and adaptive immune responses through the release of various mediators, including immunosuppressive molecules, growth factors, exosomes, chemokines, complement components and various metabolites. Interestingly, even nonviable MSCs can exert beneficial effects, with apoptotic MSCs showing immunosuppressive functions in vivo. Because the immunomodulatory capabilities of MSCs are not constitutive but rather are licensed by inflammatory cytokines, the net outcomes of MSC activation might vary depending on the levels and the types of inflammation within the residing tissues. Here, we review current understanding of the immunomodulatory mechanisms of MSCs and the issues related to their therapeutic applications.

TNF-α-induced exosomal miR-146a mediates mesenchymal stem cell-dependent suppression of urethral stricture

The effective treatment of urethral stricture remains a medical problem. The use of proinflammatory cytokines as stimuli to improve the reparative efficacy of mesenchymal stem cells (MSCs) towards damaged tissues represents an evolving field of investigation. However, the therapeutic benefits of this strategy in the treatment of urethral stricture remain unknown. Here, we enriched exosomes derived from human umbilical cord-derived MSCs pretreated with or without tumor necrosis factor alpha (TNF-α) to evaluate their therapeutic effects in an in vivo model of TGFβ1-induced urethral stricture. Male Sprague-Dawley rats received sham (saline) or TGFβ1 injections to urethral tissues followed by incisions in the urethra. Animals in the TGFβ1 injection (urethral fibrosis) cohort were subsequently injected with vehicle control, or with exosomes derived from MSCs cultured with or without TNF-α. After 4 weeks, rats underwent ultrasound evaluation and, following euthanasia, urethral tissues were harvested for histological and molecular analysis. In vitro, the effects of MSC-derived exosomes on fibroblast secretion of collagen and cytokines were studied by enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (qRT-PCR), and western blot analysis. Exosomes derived from MSCs pretreated with TNF-α were more effective in suppressing urethral fibrosis and stricture than exosomes from untreated MSCs. We found that miR-146a, an anti-inflammatory miRNA, was strongly upregulated in TNF-α-stimulated MSCs and was selectively packaged into exosomes. Moreover, miR-146a-containing exosomes were taken up by fibroblasts and inhibited fibroblast activation and associated inflammatory responses, a finding that may underlie the therapeutic mechanism for suppression of urethral stricture. Inhibition of miR-146a in TNF-α-treated MSCs partially reduced antifibrotic effects and increased the release of proinflammatory factors of exosomes derived from these cells. Together these findings demonstrate that exosomes derived from TNF-α-treated MSCs are of therapeutic benefit in urethral fibrosis, suggesting that this strategy may have utility as an adjuvant therapy in the treatment of urethral stricture diseases.

IL-1β-Mediated Activation of Adipose-Derived Mesenchymal Stromal Cells Results in PMN Reallocation and Enhanced Phagocytosis: A Possible Mechanism for the Reduction of Osteoarthritis Pathology

Background: Injection of adipose-derived mesenchymal stromal cells (ASCs) into murine knee joints after induction of inflammatory collagenase-induced osteoarthritis (CiOA) reduces development of joint pathology. This protection is only achieved when ASCs are applied in early CiOA, which is characterized by synovitis and high S100A8/A9 and IL-1β levels, suggesting that inflammation is a prerequisite for the protective effect of ASCs. Our objective was to gain more insight into the interplay between synovitis and ASC-mediated amelioration of CiOA pathology.

Methods: CiOA was induced by intra-articular collagenase injection. Knee joint sections were stained with hematoxylin/eosin and immunolocalization of polymorphonuclear cells (PMNs) and ASCs was performed using antibodies for NIMP-R14 and CD271, respectively. Chemokine expression induced by IL-1β or S100A8/A9 was assessed with qPCR and Luminex. ASC-PMN co-cultures were analyzed microscopically and with Luminex for inflammatory mediators. Migration of PMNs through transwell membranes toward conditioned medium of non-stimulated ASCs (ASC_NS-CM) or IL-1β-stimulated ASCs (ASC_IL-1β-CM) was examined using flow cytometry. Phagocytic capacity of PMNs was measured with labeled zymosan particles.

Results: Intra-articular saline injection on day 7 of CiOA increased synovitis after 6 h, characterized by PMNs scattered throughout the joint cavity and the synovium. ASC injection resulted in comparable numbers of PMNs which clustered around ASCs in close interaction with the synovial lining. IL-1β-stimulation of ASCs in vitro strongly increased expression of PMN-attracting chemokines CXCL5, CXCL7, and KC, whereas S100A8/A9-stimulation did not. In agreement, the number of clustered PMNs per ASC was significantly increased after 6 h of co-culturing with IL-1β-stimulated ASCs. Also migration of PMNs toward ASC_IL-1β-CM was significantly enhanced (287%) when compared to ASC_NS-CM. Interestingly, association of PMNs with ASCs significantly diminished KC protein release by ASCs (69% lower after 24 h), accompanied by reduced release of S100A8/A9 protein by the PMNs. Moreover, phagocytic capacity of PMNs was strongly enhanced after priming with ASC_IL-1β-CM.

Conclusions: Local application of ASCs in inflamed CiOA knee joints results in clustering of attracted PMNs with ASCs in the synovium, which is likely mediated by IL-1β-induced up-regulation of chemokine release by ASCs. This results in enhanced phagocytic capacity of PMNs, enabling the clearance of debris to attenuate synovitis.

Single cell transcriptomic analysis of human mesenchymal stem cells reveals limited heterogeneity

Mesenchymal stem cells (MSCs) are a population of multipotent cells with a superior ability to promote tissue repair by regulating regeneration and inflammation. Effective application of MSCs in disease treatment relies on the production of relatively homogeneous cell population. However, the cellular heterogeneity and the differentiation trajectories of in vitro expanded MSCs remain largely unclear. We profiled the transcriptomes of 361 single MSCs derived from two umbilical cords (UC-MSCs). These UC-MSCs were harvested at different passages and stimulated with or without inflammatory cytokines. Weighted gene correlation network analysis revealed that UC-MSCs surprisingly possess only limited heterogeneity, regardless of donors, and passages. We also found that upon pretreatment with inflammatory cytokines (IFNγ and TNFα), a classical strategy that can improve the efficiency of MSC-based therapy, MSCs exhibited uniformed changes in gene expression. Cell cycle-based principal component analysis showed that the limited heterogeneity identified in these UC-MSCs was strongly associated with their entrance into the G2/M phase. This was further proven by the observation that one featured gene, CD168, was expressed in a cell cycle-dependent manner. When CD168^high UC-MSCs were sorted and cultured in vitro, they again showed similar CD168 expression patterns. Our results demonstrated that in vitro expanded UC-MSCs are a well-organized population with limited heterogeneity dominated by cell cycle status. Thus, our studies provided information for standardization of MSCs for disease treatment.

Exosomal miR-146a Contributes to the Enhanced Therapeutic Efficacy of Interleukin-1β-Primed Mesenchymal Stem Cells Against Sepsis

Improving the immunomodulatory efficacy of mesenchymal stem cells (MSCs) through pretreatment with pro-inflammatory cytokines is an evolving field of investigation. However, the underlying mechanisms have not been fully clarified. Here, we pretreated human umbilical cord-derived MSCs with interleukin-1β (IL-1β) and evaluated their therapeutic effects in a cecal ligation and puncture-induced sepsis model. We found that systemic administration of IL-1β-pretreated MSCs (βMSCs) ameliorated the symptoms of murine sepsis more effectively and increased the survival rate compared with naïve MSCs. Furthermore, βMSCs could more effectively induce macrophage polarization toward an anti-inflammatory M2 phenotype through the paracrine activity. Mechanistically, we demonstrated that βMSC-derived exosomes contributed to the enhanced immunomodulatory properties of βMSCs both in vitro and in vivo. Importantly, we found that miR-146a, a well-known anti-inflammatory microRNA, was strongly upregulated by IL-1β stimulation and selectively packaged into exosomes. This exosomal miR-146a was transferred to macrophages, resulted in M2 polarization, and finally led to increased survival in septic mice. In contrast, inhibition of miR-146a through transfection with miR-146a inhibitors partially negated the immunomodulatory properties of βMSC-derived exosomes. Taken together, IL-1β pretreatment effectively enhanced the immunomodulatory properties of MSCs partially through exosome-mediated transfer of miR-146a. Therefore, we believe that IL-1β pretreatment may provide a new modality for better therapeutic application of MSCs in inflammatory disorders. Stem Cells 2017;35:1208-1221.

Pretreatment with IL-1β enhances proliferation and chondrogenic potential of synovium-derived mesenchymal stem cells

BACKGROUND AIMS

Synovial mesenchymal stem cells (MSCs) are an attractive cell source for cartilage regeneration because of their high proliferative ability and chondrogenic potential. We have performed clinical trials using synovial MSCs to regenerate articular cartilage. To achieve good clinical outcomes for cell transplantation therapy, it is important to control both quantity (cell number) and quality (pluripotency or chondrogenic potential) of the cells for transplantation. Interleukin (IL)-1β is a pro-inflammatory cytokine with significant pro-proliferative potential for mesenchymal cells. However, the effects of IL-1β on synovial MSCs remain unknown. We investigated the effects of pretreatment with IL-1β on synovial MSCs.

METHODS

Human synovial tissue was harvested during total knee arthroplasty. Nucleated cells were plated and cultured in the absence or presence of IL-1β at 10^-13, 10^-12, 10^-11, 10^-10, 10^-9 or 10^-8 g/mL for 14 days.

RESULTS

The number of synovial MSCs increased in a concentration-dependent manner. When cultured for 21 days in chondrogenic medium after pretreatment with 10^-8  g/mL IL-1β, pellet aggregation was observed, whereas pretreatment with 10^-12, 10^-11 or 10^-10 g/mL IL-1β significantly increased the weight of cartilage pellets (P <0.01). Surface markers for adhesion ability and pluripotency were reduced with high concentrations of IL-1β. IL-6 and IL-8 expression increased, but no changes in the expression level of growth factors were indicated by cytokine array.

CONCLUSIONS

We have demonstrated that pretreatment of IL-1β increased the proliferation and chondrogenic potential of synovial MSCs, which may promote the regenerative potential of synovial MSCs.

Donor variability among anti-inflammatory pre-activated mesenchymal stromal cells

Therapeutic mesenchymal stromal cells (MSCs) are attractive in part due to their immunomodulatory properties, achieved by their paracrine secretion of factors including prostaglandin E2 (PGE2). Despite promising pre-clinical data, demonstrating clinical efficacy has proven difficult. The current studies were designed to develop approaches to pre-induce desired functions from naïve MSCs and examine MSC donor variability, two factors contributing to this disconnect. MSCs from six human donors were pre-activated with interleukin 1 beta (IL-1β) at a concentration and duration identified as optimal or interferon gamma (IFN-γ) as a comparator. Their secretion of PGE2 after pre-activation and secondary exposure to pro-inflammatory molecules was measured. Modulation of tumor necrosis factor alpha (TNF-α) secretion from M1 pro-inflammatory macrophages by co-cultured pre-activated MSCs was also measured. Our results indicated that pre-activation of MSCs with IL-1β resulted in upregulated PGE2 secretion post exposure. Pre-activation with IL-1β or IFN-γ resulted in higher sensitivity to induction by secondary stimuli compared to no pre-activation. While IL-1β pre-activation led to enhanced MSC-mediated attenuation of macrophage TNF-α secretion, IFN-γ pre-activation resulted in enhanced TNF-α secretion. Donor variability was noted in PGE2 secretion and upregulation and the level of improved or impaired macrophage modulation.

Mesenchymal stem cells in cardiac regeneration: a detailed progress report of the last 6 years (2010-2015)

Mesenchymal stem cells have been used for cardiovascular regenerative therapy for decades. These cells have been established as one of the potential therapeutic agents, following several tests in animal models and clinical trials. In the process, various sources of mesenchymal stem cells have been identified which help in cardiac regeneration by either revitalizing the cardiac stem cells or revascularizing the arteries and veins of the heart. Although mesenchymal cell therapy has achieved considerable admiration, some challenges still remain that need to be overcome in order to establish it as a successful technique. This in-depth review is an attempt to summarize the major sources of mesenchymal stem cells involved in myocardial regeneration, the significant mechanisms involved in the process with a focus on studies (human and animal) conducted in the last 6 years and the challenges that remain to be addressed.

Human umbilical cord blood-derived mesenchymal stem cells improve functional recovery through thrombospondin1, pantraxin3, and vascular endothelial growth factor in the ischemic rat brain

Cell therapy is a potential therapeutic method for cerebral ischemia, which remains a serious problem. In the search for more effective therapeutic methods, many kinds of stem cells from various tissues have been developed and tested as candidate therapeutic agents. Among them, human umbilical cord blood (hUCB)-derived mesenchymal stem cells (MSCs) are widely used for cell therapy because of their genetic flexibility. To confirm that they are effective and understand how they affect ischemic neural cells, hUCB-MSCs were directly administered ipsilaterally into an ischemic zone induced by middle cerebral artery occlusion (MCAO). We found that the neurobehavioral performance of the hUCB-MSC group was significantly improved compared with that of the vehicle-injected control group. The infarct was also remarkably smaller in the hUCB-MSC group. Additionally, hUCB-MSC transplantation resulted in a greater number of newly generated cells and angiogenic and tissue repair factors and a lower number of inflammatory events in the penumbra zone. To determine why these events occurred, hUCB-MSCs were assayed under hypoxic and normoxic conditions in vitro. The results showed that hUCB-MSCs exhibit higher expression levels of thrombospondin1, pantraxin3, and vascular endothelial growth factor under hypoxic conditions than under normoxic conditions. These results were found to be correlated with our in vivo immunofluorescent staining results. On the basis of these findings, we suggest that hUCB-MSCs may have a beneficial effect on cerebral ischemia, especially through angiogenesis, neurogenesis, and anti-inflammatory effects, and thus could be used as a therapeutic agent to treat neurological disorders such as cerebral ischemia.

Identification of IL-1β and LPS as optimal activators of monolayer and alginate-encapsulated mesenchymal stromal cell immunomodulation using design of experiments and statistical methods

Induction of therapeutic mesenchymal stromal cell (MSC) function is dependent upon activating factors present in diseased or injured tissue microenvironments. These functions include modulation of macrophage phenotype via secreted molecules including prostaglandin E2 (PGE2). Many approaches aim to optimize MSC-based therapies, including preconditioning using soluble factors and cell immobilization in biomaterials. However, optimization of MSC function is usually inefficient as only a few factors are manipulated in parallel. We utilized fractional factorial design of experiments to screen a panel of 6 molecules (lipopolysaccharide [LPS], polyinosinic-polycytidylic acid [poly(I:C)], interleukin [IL]-6, IL-1β, interferon [IFN]-β, and IFN-γ), individually and in combinations, for the upregulation of MSC PGE2 secretion and attenuation of macrophage secretion of tumor necrosis factor (TNF)-α, a pro-inflammatory molecule, by activated-MSC conditioned medium (CM). We used multivariable linear regression (MLR) and analysis of covariance to determine differences in functions of optimal factors on monolayer MSCs and alginate-encapsulated MSCs (eMSCs). The screen revealed that LPS and IL-1β potently activated monolayer MSCs to enhance PGE2 production and attenuate macrophage TNF-α. Activation by LPS and IL-1β together synergistically increased MSC PGE2, but did not synergistically reduce macrophage TNF-α. MLR and covariate analysis revealed that macrophage TNF-α was strongly dependent on the MSC activation factor, PGE2 level, and macrophage donor but not MSC culture format (monolayer versus encapsulated). The results demonstrate the feasibility and utility of using statistical approaches for higher throughput cell analysis. This approach can be extended to develop activation schemes to maximize MSC and MSC-biomaterial functions prior to transplantation to improve MSC therapies.

The Clinical Status of Stem Cell Therapy for Ischemic Cardiomyopathy

Ischemic cardiomyopathy (ICM) is becoming a leading cause of morbidity and mortality in the whole world. Stem cell-based therapy is emerging as a promising option for treatment of ICM. Several stem cell types including cardiac-derived stem cells (CSCs), bone marrow-derived stem cells, mesenchymal stem cells (MSCs), skeletal myoblasts (SMs), and CD34(+) and CD 133(+) stem cells have been applied in clinical researches. The clinical effect produced by stem cell administration in ICM mainly depends on the transdifferentiation and paracrine effect. One important issue is that low survival and residential rate of transferred stem cells in the infracted myocardium blocks the effective advances in cardiac improvement. Many other factors associated with the efficacy of cell replacement therapy for ICM mainly including the route of delivery, the type and number of stem cell infusion, the timing of injection, patient's physical condition, the particular microenvironment onto which the cells are delivered, and clinical condition remain to be addressed. Here we provide an overview of the pros and cons of these transferred cells and discuss the current state of their therapeutic potential. We believe that stem cell translation will be an ideal option for patients following ischemic heart disease in the future.

Paracrine mechanisms of mesenchymal stem cell-based therapy: current status and perspectives

Mesenchymal stem cells (MSCs) are one of a few stem cell types to be applied in clinical practice as therapeutic agents for immunomodulation and ischemic tissue repair. In addition to their multipotent differentiation potential, a strong paracrine capacity has been proposed as the principal mechanism that contributes to tissue repair. Apart from cytokine/chemokine secretion, MSCs also display a strong capacity for mitochondrial transfer and microvesicle (exosomes) secretion in response to injury with subsequent promotion of tissue regeneration. These unique properties of MSCs make them an invaluable cell type to repair damaged tissues/organs. Although MSCs offer great promise in the treatment of degenerative diseases and inflammatory disorders, there are still many challenges to overcome prior to their widespread clinical application. Particularly, their in-depth paracrine mechanisms remain a matter for debate and exploration. This review will highlight the discovery of the paracrine mechanism of MSCs, regulation of the paracrine biology of MSCs, important paracrine factors of MSCs in modulation of tissue repair, exosome and mitochondrial transfer for tissue repair, and the future perspective for MSC-based therapy.

A role of microRNA-370 in hepatic ischaemia-reperfusion injury by targeting transforming growth factor-β receptor II

BACKGROUND & AIMS

MicroRNAs (miRNAs) are a group of small non-coding RNAs with modulator activity of gene expression. The role of miRNAs in hepatic ischaemia-reperfusion (IR) injury is currently largely unknown. The aim of this study was to investigate the potential role of miR-370 in hepatic IR injury.

METHODS

The expression levels of hepatic miR-370 in male C57BL/6 mice subjected to hepatic IR injury or ischaemia preconditioning were assessed by quantitative real-time PCR. The effect of miR-370 on hepatic IR injury was investigated by serum enzyme analysis and histological examination of liver following treatment of mice with antagomir-370 or control. The levels of proinflammatory cytokines and apoptosis- and proliferation-related genes were also determined by quantitative real-time PCR. Furthermore, the potential targets of miR-370 in this injury were studied by bioinformatics analysis, luciferase assays, quantitative real-time PCR and Western blot.

RESULTS

The results showed that miR-370 expression was significantly upregulated in the mice subjected to hepatic IR injury as compared with the sham-operated mice. Inhibition of miR-370 led to the downregulation of serum aminotransferase and proinflammatory cytokines, as well as the improvement of hepatic histological damage. Reporter assays confirmed that miR-370 directly targeted the 3' untranslated region of transforming growth factor-β receptor II (TβRII). Inhibition of miR-370 was sufficient to reinstate the expression of TβRII and its downstream target phosphorylated Smad3.

CONCLUSION

Our data suggest that miR-370 acting via TβRII might play a potential role in hepatic IR injury, and inhibition of miR-370 efficiently attenuated the damage to the liver.

Plasticity of mesenchymal stem cells in immunomodulation: pathological and therapeutic implications

Mesenchymal stem cells (MSCs) are multipotent stromal cells that exist in many tissues and are capable of differentiating into several different cell types. Exogenously administered MSCs migrate to damaged tissue sites, where they participate in tissue repair. Their communication with the inflammatory microenvironment is an essential part of this process. In recent years, much has been learned about the cellular and molecular mechanisms of the interaction between MSCs and various participants in inflammation. Depending on their type and intensity, inflammatory stimuli confer on MSCs the ability to suppress the immune response in some cases or to enhance it in others. Here we review the current findings on the immunoregulatory plasticity of MSCs in disease pathogenesis and therapy.

Mesenchymal stromal cells: sensors and switchers of inflammation

In addition to their stem/progenitor properties, mesenchymal stromal cells (MSCs) possess broad immunoregulatory properties that are being investigated for potential clinical application in treating immune-based disorders. An informed view of the scope of this clinical potential will require a clear understanding of the dynamic interplay between MSCs and the innate and adaptive immune systems. In this Review, we outline current insights into the ways in which MSCs sense and control inflammation, highlighting the central role of macrophage polarization. We also draw attention to functional differences seen between vivo and in vitro contexts and between species. Finally, we discuss progress toward clinical application of MSCs, focusing on GvHD as a case study.

The caspase-8 shRNA-modified mesenchymal stem cells improve the function of infarcted heart

The beneficial effects of mesenchymal stem cells (MSCs) in cardiac cell therapy are greatly limited due to poor survival after transplantation into ischemic hearts. Here, we investigated whether caspase 8 small hairpin RNA (shRNA) modification enhance human MSCs (hMSCs) survival and improve infarcted heart function. Recombinant adenovirus encoding pre-miRNA-155-designed caspase 8 shRNA was prepared to inhibit caspase 8 expression in hMSCs. The effect of caspase 8 shRNA modification on protecting hMSCs from apoptosis under the conditions of serum deprivation and hypoxia was tested by Annexin V/PI staining and caspase 8 activity assay. The caspase 8 shRNA-modified and superparamagnetic iron oxide (SPIO)-labeled hMSCs were injected into the border zone of the infarcted region of rat heart. Echocardiography and Masson trichrome staining were performed to assess heart function and cardiac fibrosis. Our results showed that adenovirus-mediated caspase 8 shRNA could efficiently inhibit caspase 8 expression in hMSCs. Knock-down of caspase 8 expression lead to inhibition of hMSCs apoptosis, reduction of caspase 8 activity and up-regulations of HGF, IGF-1 and Bcl-2. Transplantation of caspase 8 shRNA-modified hMSCs could significantly improve infracted heart function, attenuate cardiac fibrosis. Consistently, the rate of cardiomyocyte apoptosis and caspase 8 activity were significantly decreased, and the survival rate of transplanted hMSCs was markedly elevated in the myocardium receiving caspase 8 shRNA-modified hMSCs transplantation. Together, our findings implicated the therapeutic potential of caspase 8 shRNA-modified hMSCs in improving the infarcted heart function.

IL-8 enhances the angiogenic potential of human bone marrow mesenchymal stem cells by increasing vascular endothelial growth factor

The beneficial effects of mesenchymal stem cells (MSCs) are mediated partly by the paracrine production of cytoprotective and trophic factors. Vascular endothelial growth factor (VEGF) is released from MSCs as a paracrine trophic factor and contributes to the therapeutic effects of the stem cell by regulating angiogenesis and promoting revascularization in injured tissues. Interleukin-8 (IL-8), an inflammatory chemokine with potent proangiogenic properties, is upregulated in the ischemic brain and has been shown to promote homing of bone marrow-derived cells to injured sites. However, the effect of IL-8 on MSCs paracrine function remains unknown. We found that IL-8 induced VEGF production and phosphorylation of Akt and ERK. Both effects could be blocked by inhibitors (LY294002, PD098059) or siRNA-mediated silencing of Akt and ERK in human bone marrow MSCs (hBM-MSCs). IL-8-induced VEGF production in hBM-MSCs significantly increased tube formation on Matrigel compared with basal secreted VEGF. In a rat stroke model, administration of IL-8-treated hBM-MSCs decreased the infarction volume and increased angiogenesis in the ischemic boundary zone compared with hBM-MSC treatment alone. In conclusion, IL-8 stimulates VEGF production in hBM-MSCs in part via the PI3K/Akt and MAPK/ERK signal transduction pathways and that administration of IL-8-treated hBM-MSCs increases angiogenesis after stroke. This approach may be used to optimize MSC-based therapies for numerous diseases including stroke, myocardial ischemia, and spinal cord injury.

Co-treating mesenchymal stem cells with IL‑1β and TNF-α increases VCAM-1 expression and improves post-ischemic myocardial function

Inflammatory mediators are released by the myocardium following myocardial ischemia as a response to tissue injury, and contribute to cardiac repair and adaptive responses. Treating mesenchymal stem cells (MSCs) with various inflammatory factors activates a series of biological processes that enhance cell-mediated cardioprotection following myocardial infarction (MI). The present study was designed to examine the effect of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) treatment on vascular cell adhesion molecule-1 (VCAM-1) expression in MSCs, and to identify whether cytokine-treated MSCs improve post-ischemic myocardial function in a rat model. MSCs were stimulated with IL-1β and/or TNF-α for 24 h, the production of vascular cell adhesion molecule-1 (VCAM-1) and the adhesion ability of MSCs were assessed by flow cytometry, adhesion assays, quantitative polymerase chain reaction and western blot analysis. The cardiac function was examined by two-dimensional echocardiography. The results demonstrated that in treated MSCs, the secretion of VCAM-1 and the cell adhesion ability were significantly increased, thus markedly improving cardiac function compared with that of the control group (P<0.01). Of all the groups, the rats stimulated with a combination of IL-1β and TNF-α exhibited the greatest cardiac improvements. However, there was no significant difference between the 10 and 20 ng/ml groups which were stimulated with one of the cytokines alone (P>0.05). In conclusion, stimulating MSCs with IL-1β and TNF-α promoted the expression of VCAM-1 and improved post-ischemic cardiac function recovery. Treating MSCs with two cytokines in combination may be a useful method to maximize the potential of cell-based therapy for MI.

Epithelial-to-Mesenchymal Transition Enhances the Cardioprotective Capacity of Human Amniotic Epithelial Cells

The amniotic epithelium consists of cells exhibiting mature epithelial cell characteristics, but also varying degrees of stemness. We tested the hypothesis that induction of epithelial-to-mesenchymal transition (EMT) in amniotic epithelial cells (AECs) derived from human placenta enhances their capacity to support the ischemic myocardium. In response to incubation with transforming growth factor-β1 (TGF-β1) protein, AECs lost their cobblestone morphology and acquired a fibroblastoid shape, associated with downregulation of E-cadherin, upregulation of N-cadherin, Akt phosphorylation, and intracellular periostin translocation. EMT-AECs displayed greatly enhanced mobility and secreted gelatinase activity compared with naive AECs. The surface presentation of CD105 and CD73 decreased, and RNA microarray analysis mirrored the loss of epithelial characteristics and transcriptional profile. Unmodified AECs and EMT-AECs were then injected intramyocardially in fully immunocompetent mice after permanent LAD ligation, and heart function was followed by MRI as well as 2D speckle tracking echocardiography after 4 weeks. EMT-AEC-treated infarct hearts displayed better global systolic function and improved longitudinal strain rate in the area of interest. Although no signals of human cells were detectable by histology, infarct size was smaller in EMT-AEC-treated hearts, associated with fewer TUNEL-positive cells and upregulation of periostin, while blood vessel density was increased in both ACE- and EMT-AEC-treated hearts. We conclude that EMT enhances the cardioprotective effects of human AECs.

Ischemia/Reperfusion injury protection by mesenchymal stem cell derived antioxidant capacity

Mesenchymal stem cell (MSC) transplantation after ischemia/reperfusion (I/R) injury reduces infarct size and improves cardiac function. We used mouse ventricular myocytes (VMs) in an in vitro model of I/R to determine the mechanism by which MSCs prevent reperfusion injury by paracrine signaling. Exposure of mouse VMs to an ischemic challenge depolarized their mitochondrial membrane potential (Ψmito), increased their diastolic Ca(2+), and significantly attenuated cell shortening. Reperfusion of VMs with Ctrl tyrode or MSC-conditioned tyrode (ConT) resulted in a transient increase of the Ca(2+) transient amplitudes in all cells. ConT-reperfused cells exhibited a decreased number early after depolarization (EADs) (ConT: 6.3% vs. Ctrl: 28.4%) and prolonged survival (ConT: 58% vs. Ctrl: 33%). Ψmito rapidly recovered in Ctrl as well as ConT-treated VMs on reperfusion; however, in Ctrl solution, an exaggerated hyperpolarization of Ψmito was determined that preceded the collapse of Ψmito. The ability of ConT to attenuate the hyperpolarization of Ψmito was suppressed on inhibition of the PI3K/Akt signaling pathway or IK,ATP. However, protection of Ψmito was best mimicked by the reactive oxygen species (ROS) scavenger mitoTEMPO. Analysis of ConT revealed a significant antioxidant capacity that was linked to the presence of extracellular superoxide dismutase (SOD3) in ConT. In conclusion, MSC ConT protects VMs from simulated I/R injury by its SOD3-mediated antioxidant capacity and by delaying the recovery of Ψmito through Akt-mediated opening of IK,ATP. These changes attenuate reperfusion-induced ROS production and prevent the opening of the permeability transition pore and arrhythmic Ca(2+) release.

Adipose stromal cells primed with hypoxia and inflammation enhance cardiomyocyte proliferation rate in vitro through STAT3 and Erk1/2

Background

Experimental clinical stem cell therapy has been used for more than a decade to alleviate the adverse aftermath of acute myocardial infarction (aMI). The post-infarcted myocardial microenvironment is characterized by cardiomyocyte death, caused by ischemia and inflammation. These conditions may negatively affect administered stem cells. As postnatal cardiomyocytes have a poor proliferation rate, while induction of proliferation seems even more rare. Thus stimulation of their proliferation rate is essential after aMI. In metaplastic disease, the pro-inflammatory cytokine interleukin-6 (IL-6) has been identified as potent mediators of the proliferation rate. We hypothesized that IL-6 could augment the proliferation rate of (slow-)dividing cardiomyocytes.

Methods

To mimic the behavior of therapeutic cells in the post-infarct cardiac microenvironment, human Adipose Derived Stromal Cells (ADSC) were cultured under hypoxic (2% O₂) and pro-inflammatory conditions (IL-1β) for 24h. Serum-free conditioned medium from ADSC primed with hypoxia and/or IL-1β was added to rat neonatal cardiomyocytes and adult cardiomyocytes (HL-1) to assess paracrine-driven changes in cardiomyocyte proliferation rate and induction of myogenic signaling pathways.

Results

We demonstrate that ADSC enhance the proliferation rate of rat neonatal cardiomyocytes and adult HL-1 cardiomyocytes in a paracrine fashion. ADSC under hypoxia and inflammation in vitro had increased the interleukin-6 (IL-6) gene and protein expression. Similar to conditioned medium of ADSC, treatment of rat neonatal cardiomyocytes and HL-1 with recombinant IL-6 alone also stimulated their proliferation rate. This was corroborated by a strong decrease of cardiomyocyte proliferation after addition of IL-6 neutralizing antibody to conditioned medium of ADSC. The stimulatory effect of ADSC conditioned media or IL-6 was accomplished through activation of both Janus Kinase-Signal Transducer and Activator of Transcription (JAK/STAT) and Mitogen-Activated Protein (MAP) kinases (MAPK) mitogenic signaling pathways.

Conclusion

ADSC are promising therapeutic cells for cardiac stem cell therapy. The inflammatory and hypoxic host post-MI microenvironment enhances the regenerative potential of ADSC to promote the proliferation rate of cardiomyocytes. This was achieved in paracrine manner, which warrants the development of ADSC conditioned medium as an “of-the-shelf” product for treatment of post-myocardial infarction complications.

High density lipoprotein protects mesenchymal stem cells from oxidative stress-induced apoptosis via activation of the PI3K/Akt pathway and suppression of reactive oxygen species

The therapeutic effect of transplantation of mesenchymal stem cells (MSCs) in myocardial infarction (MI) appears to be limited by poor cell viability in the injured tissue, which is a consequence of oxidative stress and pro-apoptotic factors. High density lipoprotein (HDL) reverses cholesterol transport and has anti-oxidative and anti-apoptotic properties. We, therefore, investigated whether HDL could protect MSCs from oxidative stress-induced apoptosis. MSCs derived from the bone marrow of rats were pre-incubated with or without HDL, and then were exposed to hydrogen peroxide (H₂O₂) in vitro, or were transplanted into experimentally infarcted hearts of rats in vivo. Pre-incubation of MSCs with HDL increased cell viability, reduced apoptotic indices and resulted in parallel decreases in reactive oxygen species (ROS) in comparison with control MSCs. Each of the beneficial effects of HDL on MSCs was attenuated by inhibiting the PI3K/Akt pathway. Preconditioning with HDL resulted in higher MSC survival rates, improved cardiac remodeling and better myocardial function than in the MSC control group. Collectively, these results suggest that HDL may protect against H₂O₂-induced apoptosis in MSCs through activation of a PI3K/Akt pathway, and by suppressing the production of ROS.

miR-21 modulates tumor outgrowth induced by human adipose tissue-derived mesenchymal stem cells in vivo

Mesenchymal stem cells (MSCs) have generated a great deal of interest in clinical situations, due principally to their potential use in regenerative medicine and tissue engineering applications. However, the therapeutic application of MSCs remains limited, unless the favorable effects of MSCs on tumor growth in vivo, and the long-term safety of the clinical applications of MSCs, can be more thoroughly understood. In this study, we determined whether microRNAs can modulate MSC-induced tumor outgrowth in BALB/c nude mice. Overexpression of miR-21 in human adipose-derived stem cells (hADSCs) inhibited hADSC-induced tumor growth, and inhibition of miR-21 increased it. Downregulation of transforming growth factor beta receptor II (TGFBR2), but not of signal transducer and activator of transcription 3, in hADSCs showed effects similar to those of miR-21 overexpression. Downregulation of TGFBR2 and overexpression of miR21 decreased tumor vascularity. Inhibition of miR-21 and the addition of TGF-β increased the levels of vascular endothelial growth factor and interleukin-6 in hADSCs. Transplantation of miR-21 inhibitor-transfected hADSCs increased blood flow recovery in a hind limb ischemia model of nude mice, compared with transplantation of control oligo-transfected cells. These findings indicate that MSCs might favor tumor growth in vivo. Thus, it is necessary to study the long-term safety of this technique before MSCs can be used as therapeutic tools in regenerative medicine and tissue engineering.