Enhanced therapeutic effects of mesenchymal stem cells on myocardial infarction by ischemic postconditioning through paracrine mechanisms in rats

Emerging Trends in Mesenchymal Stem Cells Applications for Cardiac Regenerative Therapy: Current Status and Advances

Irreversible myocardium infarction is one of the leading causes of cardiovascular disease (CVD) related death and its quantum is expected to grow in coming years. Pharmacological intervention has been at the forefront to ameliorate injury-related morbidity and mortality. However, its outcomes are highly skewed. As an alternative, stem cell-based tissue engineering/regenerative medicine has been explored quite extensively to regenerate the damaged myocardium. The therapeutic modality that has been most widely studied both preclinically and clinically is based on adult multipotent mesenchymal stem cells (MSC) delivered to the injured heart. However, there is debate over the mechanistic therapeutic role of MSC in generating functional beating cardiomyocytes. This review intends to emphasize the role and use of MSC in cardiac regenerative therapy (CRT). We have elucidated in detail, the various aspects related to the history and progress of MSC use in cardiac tissue engineering and its multiple strategies to drive cardiomyogenesis. We have further discussed with a focus on the various therapeutic mechanism uncovered in recent times that has a significant role in ameliorating heart-related problems. We reviewed recent and advanced technologies using MSC to develop/create tissue construct for use in cardiac regenerative therapy. Finally, we have provided the latest update on the usage of MSC in clinical trials and discussed the outcome of such studies in realizing the full potential of MSC use in clinical management of cardiac injury as a cellular therapy module.

Adropin-based dual treatment enhances the therapeutic potential of mesenchymal stem cells in rat myocardial infarction

Both weak survival ability of stem cells and hostile microenvironment are dual dilemma for cell therapy. Adropin, a bioactive substance, has been demonstrated to be cytoprotective. We therefore hypothesized that adropin may produce dual protective effects on the therapeutic potential of stem cells in myocardial infarction by employing an adropin-based dual treatment of promoting stem cell survival in vitro and modifying microenvironment in vivo. In the current study, adropin (25 ng/ml) in vitro reduced hydrogen peroxide-induced apoptosis in rat bone marrow mesenchymal stem cells (MSCs) and improved MSCs survival with increased phosphorylation of Akt and extracellular regulated protein kinases (ERK) l/2. Adropin-induced cytoprotection was blocked by the inhibitors of Akt and ERK1/2. The left main coronary artery of rats was ligated for 3 or 28 days to induce myocardial infarction. Bromodeoxyuridine (BrdU)-labeled MSCs, which were in vitro pretreated with adropin, were in vivo intramyocardially injected after ischemia, following an intravenous injection of 0.2 mg/kg adropin (dual treatment). Compared with MSCs transplantation alone, the dual treatment with adropin reported a higher level of interleukin-10, a lower level of tumor necrosis factor-α and interleukin-1β in plasma at day 3, and higher left ventricular ejection fraction and expression of paracrine factors at day 28, with less myocardial fibrosis and higher capillary density, and produced more surviving BrdU-positive cells at day 3 and 28. In conclusion, our data evidence that adropin-based dual treatment may enhance the therapeutic potential of MSCs to repair myocardium through paracrine mechanism via the pro-survival pathways.

Dose-Independent Therapeutic Benefit of Bone Marrow Stem Cell Transplantation after MI in Mice

Several cell populations derived from bone marrow (BM) have been shown to possess cardiac regenerative potential. Among these are freshly isolated CD133⁺ hematopoietic as well as culture-expanded mesenchymal stem cells. Alternatively, by purifying CD271⁺ cells from BM, mesenchymal progenitors can be enriched without an ex vivo cultivation. With regard to the limited available number of freshly isolated BM-derived stem cells, the effect of the dosage on the therapeutic efficiency is of particular interest. Therefore, in the present pre-clinical study, we investigated human BM-derived CD133⁺ and CD271⁺ stem cells for their cardiac regenerative potential three weeks post-myocardial infarction (MI) in a dose-dependent manner. The improvement of the hemodynamic function as well as cardiac remodeling showed no therapeutic difference after the transplantation of both 100,000 and 500,000 stem cells. Therefore, beneficial stem cell transplantation post-MI is widely independent of the cell dose and detrimental stem cell amplification in vitro can likely be avoided.

JIP3 deficiency attenuates cardiac hypertrophy by suppression of JNK pathway

Pathological cardiac hypertrophy is a leading cause of morbidity and mortality worldwide; however, our understanding of the molecular mechanisms revealing the disease is still unclear. In the present study, we suggested that c-Jun N-terminal kinase (JNK)-interacting protein 3 (JIP3), involved in various cellular processes, played an essential role in regulating pathological cardiac hypertrophy through in vivo and in vitro studies. JIP3 was highly expressed in human hearts with hypertrophic cardiomyopathy (HCM), and in mouse hypertrophic hearts. Following, the wild type (WT) and JIP3-knockout (KO) mice subjected to aortic banding (AB) challenge were used as animal models with cardiac hypertrophy. The results showed that JIP3-KO mice after AB operation exhibited attenuated cardiac function, reduced fibrosis levels and decreased hypertrophic marker proteins, including atrial natriuretic peptides (Anp) and brain/B-type natriuretic peptides (Bnp) and β-myosin heavy chain (β-Mhc). Loss of JIP3 also ameliorated oxidative stress, inflammatory response, apoptosis and endoplasmic reticulum (ER) stress in hearts of mice after AB surgery. Consistently, the expressions of ER stress-related molecules, such as phosphorylated-α-subunit of the eukaryotic initiation factor-2 (eIF2α), glucose-regulated protein (GRP) 78 and C/-EBP homologous protein (CHOP), were markedly decreased by JIP3-deficiency in hearts of AB-operated mice. JNK and its down-streaming signal of p90rsk was highly activated by AB operation in WT mice, while being significantly reversed by JIP3-ablation. Intriguingly, the in vitro results showed that promoting JNK activation by using its activator of anisomycin enhanced AngII-stimulated ER stress, oxidative stress, apoptosis and inflammatory response in cardiomyocytes isolated from WT mice. However, JIP3-KO-attenuated these pathologies was rescued by anisomycin treatment in AngII-incubated cardiomyocytes. Together, the findings indicated that blockage of JIP3 could alleviate cardiac hypertrophy via inactivating JNK pathway, and thus might be a promising strategy to prevent pathological cardiac hypertrophy.

Does stem cell therapy induce myocardial neoangiogenesis? Histological evaluation in an ischemia/reperfusion animal model

BACKGROUND

In an experimental model in the rabbit, a myocardial ischemia-reperfusion injury was obtained. Subsequently, the effects of homologous bone marrow stem cell (BMSC) administration were studied.

METHODS

In 21 New Zealand adult rabbits, ischemia/reperfusion damage was induced by temporary occlusion of the anterior descending coronary artery. Homologous BMSCs were isolated, cultured and re-suspended for injection at the level of the ischemic zone. We evaluated the proangiogenetic effect of intramyocardial injections of BMSC at the peri-infarcted area. Histological evaluations were made after 20 days from the surgical procedure.

RESULTS

In rabbits treated with intramyocardial BMSC administration, we demonstrated histologically capillary neoangiogenesis, without signs of tissue immunological reaction or of generation of new myocardial cells. On the contrary, only minimal neovascular supply was detected in rabbits treated with intravenous administration of BMSC. Only typical signs of ischemic myocardium injury were observed in the control group.

CONCLUSION

These observations suggest that the effect of direct BMSC administration in ischemic myocardium could promote a capillary neoangiogenesis, which helps to prevent ischemic myocardial damage.

Delivery of Hydrogen Sulfide by Ultrasound Targeted Microbubble Destruction Attenuates Myocardial Ischemia-reperfusion Injury

Hydrogen sulfide (H₂S) is an attractive agent for myocardial ischemia-reperfusion injury, however, systemic delivery of H₂S may cause unwanted side effects. Ultrasound targeted microbubble destruction has become a promising tool for organ specific delivery of bioactive substance. We hypothesized that delivery of H₂S by ultrasound targeted microbubble destruction attenuates myocardial ischemia-reperfusion injury and could avoid unwanted side effects. We prepared microbubbles carrying hydrogen sulfide (hs-MB) with different H₂S/C₃F₈ ratios (4/0, 3/1, 2/2, 1/3, 0/4) and determined the optimal ratio. Release of H₂S triggered by ultrasound was investigated. The cardioprotective effect of ultrasound targeted hs-MB destruction was investigated in a rodent model of myocardial ischemia-reperfusion injury. The H₂S/C₃F₈ ratio of 2/2 was found to be an optimal ratio to prepare stable hs-MB with higher H₂S loading capability. Ultrasound targeted hs-MB destruction triggered H₂S release and increased the concentration of H₂S in the myocardium and lung. Ultrasound targeted hs-MB destruction limited myocardial infarct size, preserved left ventricular function and had no influence on haemodynamics and respiratory. This cardioprotective effect was associated with alleviation of apoptosis and oxidative stress. Delivery of H₂S to the myocardium by ultrasound targeted hs-MB destruction attenuates myocardial ischemia-reperfusion injury and may avoid unwanted side effects.

Potent Paracrine Effects of human induced Pluripotent Stem Cell-derived Mesenchymal Stem Cells Attenuate Doxorubicin-induced Cardiomyopathy

Transplantation of bone marrow mesenchymal stem cells (BM-MSCs) can protect cardiomyocytes against anthracycline-induced cardiomyopathy (AIC) through paracrine effects. Nonetheless the paracrine effects of human induced pluripotent stem cell-derived MSCs (iPSC-MSCs) on AIC are poorly understood. In vitro studies reveal that doxorubicin (Dox)-induced reactive oxidative stress (ROS) generation and cell apoptosis in neonatal rat cardiomyocytes (NRCMs) are significantly reduced when treated with conditioned medium harvested from BM-MSCs (BM-MSCs-CdM) or iPSC-MSCs (iPSC-MSCs-CdM). Compared with BM-MSCs-CdM, NRCMs treated with iPSC-MSCs-CdM exhibit significantly less ROS and cell apoptosis in a dose-dependent manner. Transplantation of BM-MSCs-CdM or iPSC-MSCs-CdM into mice with AIC remarkably attenuated left ventricular (LV) dysfunction and dilatation. Compared with BM-MSCs-CdM, iPSC-MSCs-CdM treatment showed better alleviation of heart failure, less cardiomyocyte apoptosis and fibrosis. Analysis of common and distinct cytokines revealed that macrophage migration inhibitory factor (MIF) and growth differentiation factor-15 (GDF-15) were uniquely overpresented in iPSC-MSC-CdM. Immunodepletion of MIF and GDF-15 in iPSC-MSCs-CdM dramatically decreased cardioprotection. Injection of GDF-15/MIF cytokines could partially reverse Dox-induced heart dysfunction. We suggest that the potent paracrine effects of iPSC-MSCs provide novel “cell-free” therapeutic cardioprotection against AIC, and that MIF and GDF-15 in iPSC-MSCs-CdM are critical for these enhanced cardioprotective effects.

Paracrine action of mesenchymal stem cells revealed by single cell gene profiling in infarcted murine hearts

Background

Mesenchymal stem cells (MSCs) have been recently demonstrated as a promising stem cell type to rescue damaged myocardium after acute infarction. One of the most important mechanisms underlying their therapeutic effects is the secretion of paracrine factors. However, the expression profile of paracrine factors of MSCs in infarcted hearts, especially at single cell level, is poorly defined.

Methods and Results

We aimed to depict the transcriptional profile of paracrine factors secreted by MSCs in vivo, with particular interest in the comparison between normal and infarcted hearts. Bone marrow mesenchymal stem cells were isolated and injected into mice hearts immediately after infarction surgery. Bioluminescence imaging (BLI) indicated a proportion of cells still alive even up to 10 days post surgery. Paralleled with survived cells, cardiac function was significantly improved after MSC injection compared to that in PBS-injected mice, indicated by MRI and histology. Despite increased number of vessels in MSC-injected hearts, endothelial cells and cardiomyocytes transdifferentiation were not observed in infarcted hearts 5 days after infarction. Furthermore, laser capture microdissection (LCM) followed by high through-put real time PCR was employed in our study, uncovering that the injected MSCs, compared to local cardiomyocytes, displayed elevated levels of secreted factors. To further investigate the regulation of those factors, we performed single cell analysis to dissect the gene expression profile of MSCs at single cell level in infarcted and normal hearts, respectively. Consistent with the in vivo observation, a similar regulation pattern of those factors was detected in cultured MSCs under hypoxia.

Conclusions

Our study, for the first time, elucidated gene expression profiles, as well as regulation of paracrine factors, of MSCs at single cell level in vivo, indicating that paracrine factors from MSCs account for the improvement of cardiac function after infarction.

New vessel formation in the context of cardiomyocyte regeneration--the role and importance of an adequate perfusing vasculature

The history of revascularization for cardiac ischemia dates back to the early 1960's when the first coronary artery bypass graft procedures were performed in humans. With this 50 year history of providing a new vasculature to ischemic and hibernating myocardium, a profound depth of experience has been amassed in clinical cardiovascular medicine as to what does, and does not work in the context of cardiac revascularization, alleviating ischemia and adequacy of myocardial perfusion. These issues are of central relevance to contemporary cell-based cardiac regenerative approaches. While the cardiovascular cell therapy field is surging forward on many exciting fronts, several well accepted clinical axioms related to the cardiac arterial supply appear to be almost overlooked by some of our current basic conceptual and experimental cell therapy paradigms. We present here information drawn from five decades of the clinical revascularization experience, review relevant new data on vascular formation via cell therapy, and put forward the case that for optimal cell-based cardiac regeneration due attention must be paid to providing an adequate vascular supply.

Induced pluripotent stem cells without c-Myc ameliorate retinal oxidative damage via paracrine effects and reduced oxidative stress in rats

PURPOSE

To investigate the efficacy and mechanisms of non-c-Myc induced pluripotent stem cell (iPSC) transplantation in a rat model of retinal oxidative damage.

METHODS

Paraquat was intravitreously injected into Sprague-Dawley rats. After non-c-Myc iPSC transplantation, retinal function was evaluated by electroretinograms (ERGs). The generation of reactive oxygen species (ROS) was determined by lucigenin- and luminol-enhanced chemiluminescence. The expression of brain-derived neurotrophic factor, ciliary neurotrophic factor, basic fibroblast growth factor (bFGF), stromal cell-derived factor (SDF)-1α, and CXCR4 was measured by immunohistochemistry and ELISA. An in vitro study using SH-SY5Y cells was performed to verify the protective effects of SDF-1α.

RESULTS

Transplantation of non-c-Myc iPSCs effectively promoted the recovery of the b-wave ratio in ERGs and significantly ameliorated retinal damage. Non-c-Myc iPSC transplantation decreased ROS production and increased the activities of superoxide dismutase and catalase, thereby reducing retinal oxidative damage and apoptotic cells. Moreover, non-c-Myc iPSC transplantation resulted in significant upregulation of SDF-1α, followed by bFGF, accompanied by a significant improvement in the ERG. In vitro studies confirmed that treatment with SDF-1α significantly reduced apoptosis in a dose-dependent manner in SH-SY5Y cells. Most transplanted cells remained in the subretinal space, with spare cells expressing neurofilament M markers at day 28. Six months after transplantation, no tumor formation was seen in animals with non-c-Myc iPSC grafts.

CONCLUSIONS

We demonstrated the potential benefits of non-c-Myc iPSC transplantation for treating oxidative-damage-induced retinal diseases. SDF-1α and bFGF play important roles in facilitating the amelioration of retinal oxidative damage after non-c-Myc iPSC transplantation.

Injection of mesenchymal stromal cells into a mechanically stimulated in vitro model of cardiac fibrosis has paracrine effects on resident fibroblasts

BACKGROUND AIMS

Myocardial infarction results in the formation of scar tissue populated by myofibroblasts, a phenotype characterized by increased contractility and matrix deposition. Mesenchymal stromal cells (MSC) delivered to the myocardium can attenuate scar growth and restore cardiac function, though the mechanism is unclear.

METHODS

This study describes a simple yet robust three-dimensional (3D) in vitro co-culture model to examine the paracrine effects of implanted MSC on resident myofibroblasts in a controlled biochemical and mechanical environment. The fibrosis model consisted of fibroblasts embedded in a 3D collagen gel cultured under defined oxygen tensions and exposed to either cyclic strain or interstitial fluid flow. MSC were injected into this model, and the effect on fibroblast phenotype was evaluated 48 h after cell injection.

RESULTS

Analysis of gene and protein expression of the fibroblasts indicated that injection of MSC attenuated the myofibroblast transition in response to reduced oxygen and mechanical stress. Assessment of vascular endothelial growth factor and insulin-like growth factor-1 levels demonstrated that their release by fibroblasts was markedly upregulated in hypoxic conditions but attenuated by strain or fluid flow. In fibroblast-MSC co-cultures, vascular endothelial growth factor levels were increased by hypoxia but not affected by mechanical stimuli, whereas insulin-like growth factor-1 levels were generally low and not affected by experimental conditions.

CONCLUSIONS

This study demonstrates how a 3D in vitro model of the cardiac scar can be used to examine paracrine effects of MSC on the phenotype of resident fibroblasts and therefore illuminates the role of injected progenitor cells on the progression of cardiac fibrosis.

Defining the role of mesenchymal stromal cells on the regulation of matrix metalloproteinases in skeletal muscle cells

Recent studies indicate that mesenchymal stromal cell (MSC) transplantation improves healing of injured and diseased skeletal muscle, although the mechanisms of benefit are poorly understood. In the present study, we investigated whether MSCs and/or their trophic factors were able to regulate matrix metalloproteinase (MMP) expression and activity in different cells of the muscle tissue. MSCs in co-culture with C2C12 cells or their conditioned medium (MSC-CM) up-regulated MMP-2 and MMP-9 expression and function in the myoblastic cells; these effects were concomitant with the down-regulation of the tissue inhibitor of metalloproteinases (TIMP)-1 and -2 and with increased cell motility. In the single muscle fiber experiments, MSC-CM administration increased MMP-2/9 expression in Pax-7(+) satellite cells and stimulated their mobilization, differentiation and fusion. The anti-fibrotic properties of MSC-CM involved also the regulation of MMPs by skeletal fibroblasts and the inhibition of their differentiation into myofibroblasts. The treatment with SB-3CT, a potent MMP inhibitor, prevented in these cells, the decrease of α-smooth actin and type-I collagen expression induced by MSC-CM, suggesting that MSC-CM could attenuate the fibrogenic response through mechanisms mediated by MMPs. Our results indicate that growth factors and cytokines released by these cells may modulate the fibrotic response and improve the endogenous mechanisms of muscle repair/regeneration.

Coronary effluent from postconditioned hearts promotes survival of mesenchymal stem cells under hypoxia

OBJECTIVES

Mesenchymal stem cells are sensitive to hypoxia under myocardial micro-environment of ischemia and reperfusion. Ischemic postconditioning, which is cardioprotective against ischemia-reperfusion injury, enhances in-vivo survival and therapeutic effects of transplanted stem cells. In this study, we investigated the effects of coronary effluent from postconditioned rat hearts on proliferation and survival of mesenchymal stem cells in vitro under hypoxia.

DESIGN

Isolated perfused rat hearts were divided into three groups (n = 6): the Sham group--receiving a 90 min perfusion; the Control group--receiving a 30 min global ischemia followed by a 60 min reperfusion; the ischemic postconditioning group--before sustained reperfusion, 3 cycles of 30 s reperfusion and 30 s ischemia were performed. Inflammation-related factors in coronary effluent were assessed by ELISA. Mesenchymal stem cells from bone marrow of Sprague-Dawley rats were cultured with coronary effluent under hypoxia (95% nitrogen, 5% carbon dioxide, and < 1% oxygen) for 6- or 18 h. Cell proliferation was determined by methyl thiazolyl tetrazolium. Survival rate was measured by Annexin V/PI.

RESULTS

Compared with ischemia-reperfusion treatment alone, postconditioning treatment increased the level of interleukin-10 and decreased the level of tumor necrosis factor-α and interleukin-1β in coronary effluent (P < 0.01). Stem cells cultured with postconditioned effluent, compared with those with ischemia-reperfusion effluent, had a higher proliferation (optical density value), more surviving cells, and less necrosis (P < 0.01).

CONCLUSIONS

Coronary effluent from postconditioned hearts may promote the proliferation and survival of mesenchymal stem cells under hypoxia, and the suppression of inflammation may be involved in this process.

Ischemic preconditioning for cell-based therapy and tissue engineering

Cell- and tissue-based therapies are innovative strategies to repair and regenerate injured hearts. Despite major advances achieved in optimizing these strategies in terms of cell source and delivery method, the clinical outcome of cell-based therapy remains unsatisfactory. The non-genetic approach of ischemic/hypoxic preconditioning to enhance cell- and tissue-based therapies has received much attention in recent years due to its non-invasive drug-free application. Here we discuss the current development of hypoxic/ischemic preconditioning to enhance stem cell-based cardiac repair and regeneration.

Transplantation of bone marrow-derived mesenchymal stem cells after regional hepatic irradiation ameliorates thioacetamide-induced liver fibrosis in rats

BACKGROUND

Recent studies have demonstrated that bone marrow-derived mesenchymal stem cells (BM-MSCs) can potentially revert liver fibrosis, but it is not known if preparative hepatic irradiation (HIR) contributes to the therapeutic effect of transplanted BM-MSCs. In this study, we investigate the effects of HIR on transplanted BM-MSCs in cirrhotic rats and the underlying mechanism by which mesenchymal stem cells (MSCs) relieve liver fibrosis.

MATERIALS AND METHODS

The BM-MSCs from male rats were labeled with CM-Dil and injected via portal vein into two groups of thioacetamide-induced cirrhotic rats, and the controls were injected with the same volume of saline. The right hemiliver of one cirrhotic rat group was irradiated (15 Gy) 4 d before transplantation. Liver function tests and histologic experiments were performed, and the liver population of BM-MSCs was estimated.

RESULTS

The transplantation of MSCs alleviated liver fibrosis and reduced expression of transforming growth factor-β1, Smad2, collagen type I, and α-SMA. HIR preconditioning promoted homing and repopulation of MSCs and resulted in better treatment outcomes.

CONCLUSIONS

HIR preconditioning enhances the effect of BM-MSCs in improving thioacetamide-induced liver fibrosis in rats by promoting their homing and repopulation. BM-MSCs may function by inhibiting transforming growth factor-β1-Smad signaling pathway in the liver.

Therapeutic potential of genes in cardiac repair

Cardiovascular diseases remain the primary reason of premature death and contribute to a major percentage of global patient morbidity. Recent knowledge in the molecular mechanisms of myocardial complications have identified novel therapeutic targets along with the availability of vectors that offer the chance for designing gene therapy technique for protection and revival of the diseased heart functions. Gene transfer procedure into the myocardium is demonstrated through direct injection of plasmid DNA or through the coronary vasculature using the direct or indirect delivery of viral vectors. Direct DNA injection to the myocardium is reported to be of immense value in research studies that aims at understanding the activities of various elements in myocardium. It is also deemed vital for investigating the effect of the myocardial pathophysiology on expression of the foreign genes that are transferred. Gene therapies have been reported to heal cardiac pathologies such as myocardial ischemia, heart failure and inherited myopathies in several animal models. The results obtained from these animal studies have also encouraged a flurry of early clinical trials. This translational research has been triggered by an enhanced understanding of the biological mechanisms involved in tissue repair after ischemic injury. While safety concerns take utmost priority in these trials, several combinational therapies, various routes and dose of delivery are being tested before concrete optimization and complete potential of gene therapy is convincingly understood.

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.

Ischemia-reperfusion injury: beneficial effects of mesenchymal stromal cells

PURPOSE OF REVIEW

Organ transplantation and other major surgeries are impacted by ischemia-reperfusion injury (IRI). Mesenchymal stromal cells (MSCs) recently became an attractive alternative therapeutic tool to combat IRI. The present review highlights the effects of MSCs in the preclinical animal models of IRI and clinical trials, and explains their potential modes of action based on the pathophysiological IRI cascade.

RECENT FINDINGS

The application of MSCs in animal models of IRI show anti-inflammatory and anti-apoptotic effects, particularly for damage to the kidneys, heart and lungs. The mechanism of MSC action remains unclear, but may involve paracrine factors which could include the transfer of microvesicles, RNA or mitochondria. Although few clinical trials have reached completion, adverse effects appear minimal.

SUMMARY

MSCs show promise in protecting against IRI-induced damage. They appear to help recovery mainly by affecting the levels of inflammation and apoptosis during the organ repair process. In addition, they may mediate immunomodulatory effects on the innate and adaptive immune processes triggered during reperfusion and reduce fibrosis. Success in preclinical animal models has led to the initiation of ongoing clinical trials.

Effective neuroprotection by ischemic postconditioning is associated with a decreased expression of RGMa and inflammation mediators in ischemic rats

Whether ischemic postconditioning (IPC) can significantly alleviate ischemic injury hinges on the appropriate measure. In this study, the expression RGMa and IL-1β, IL-6 are investigated to estimate the therapeutic benefits of various postconditioning strategies after cerebral ischemia/reperfusion. The study consists of the sham-operated group and five treatment groups: ischemia/reperfusion (I/R), two proximate ischemic postconditioning (IPC-S and IPC-M), remote postconditioning (RIPC) and delayed postconditioning (DIPC) groups. We find that rats in IPC and RIPC groups exhibit significantly less neural deficit and lower infarct volume than that in I/R and DIPC groups after ischemia/reperfusion. Moreover, in ischemic cortex and hippocampus, the mRNA level of RGMa is much lower in IPC and RIPC groups. Immunohistochemical analysis indicates that the expression of RGMa, IL-1β and IL-6 are reduced in IPC and RIPC groups (especially in IPC-S group). Furthermore, neurofilament staining reveals that the rats in IPC and RIPC groups have less axonal injury than that in I/R and DIPC groups. Our studies suggest that the optimal strategy to attenuate cerebral ischemia/reperfusion is achieved by early, short-term, and multiple cycles of proximal IPC. The cerebral protective effect of IPC may be associated with the decreased expression of RGMa and inflammation mediators.

Remote ischemic postconditioning enhances cell retention in the myocardium after intravenous administration of bone marrow mesenchymal stromal cells

Efficacy of intravenous administration of mesenchymal stromal cells (MSCs) for myocardial infarction (MI) is limited by low cell retention in the damaged myocardium. Previous studies indicated that remote ischemic conditioning could protect against ischemia-reperfusion-induced injury by release of various cytokines including stromal cell derived factor-1 alpha (SDF-1α). However, whether remote ischemic postconditioning (RIPostC) can also enhance the retention of infused cells in the myocardium by activating MSC homing is unclear. In this study, RIPostC was induced with 4cycles of 5min occlusion and reperfusion of the abdominal aorta in female Sprague-Dawley (SD) rats which underwent ligation of the coronary artery 1week previously. Cytokine levels in serum and myocardium were evaluated by enzyme-linked immunosorbent assay (ELISA) at 1, 6, 24 and 48h after RIPostC. Then, a total of 4×10(6) male MSCs were infused intravenously at 24h after RIPostC. The number of survived cells in the myocardium was evaluated by real-time polymerase chain reaction analysis for Y chromosome and the heart function was evaluated by echocardiography at 1month after cell infusion. Furthermore, 10μg/kg rabbit anti-rat CXCR4 polyclonal antibody was injected intraperitoneally to prove the role of SDF-1α for RIPostC. RIPostC induced an increase in SDF-1α in serum at 1h and enhanced SDF-1α transcription and protein synthesis in the myocardium at 24h after the procedure. 1month after cell transplantation, RIPostC significantly increased MSC myocardial retention by 79.1±12.3% and thereby contributed to enhanced cardiac function in comparison with cell transplantation without RIPostC. Furthermore, blockade with a CXCR4-specific antibody after RIPostC markedly attenuated the enhancement of therapeutic efficacy. We conclude that RIPostC activated SDF-1α expression and enhanced retention of the infused MSCs in the injured myocardium. Priming of the heart with RIPostC might be a novel adjunctive approach for intravenous cell delivery.

Repairing chronic myocardial infarction with autologous mesenchymal stem cells engineered tissue in rat promotes angiogenesis and limits ventricular remodeling

Background

Tissue engineering scaffold constitutes a new strategy of myocardial repair. Here, we studied the contribution of a patch using autologous mesenchymal stem cells (MSCs) seeded on collagen-1 scaffold on the cardiac reconstruction in rat model of chronic myocardial infarction (MI).

Methods

Patches were cultured with controlled MSCs (growth, phenotype and potentiality). Twenty coronary ligated rats with tomoscingraphy (SPECT)-authenticated transmural chronic MI were referred into a control group (n = 10) and a treated group (n = 10) which beneficiated an epicardial MSC-patch engraftment. Contribution of MSC-patch was tested 1-mo after using non-invasive SPECT cardiac imaging, invasive hemodynamic assessment and immunohistochemistry.

Results

3D-collagen environment affected the cell growth but not the cell phenotype and potentiality. MSC-patch integrates well the epicardial side of chronic MI scar. In treated rats, one-month SPECT data have documented an improvement of perfusion in MI segments compared to control (64 ± 4% vs 49 ± 3% p = 0.02) and a reduced infarction. Contractile parameter dp/dtmax and dp/dtmin were improved (p & 0.01). Histology showed an increase of ventricular wall thickness (1.75 ± 0.24 vs 1.35 ± 0.32 mm, p &0.05) and immunochemistry of the repaired tissue displayed enhanced angiogenesis and myofibroblast-like tissue.

Conclusion

3D-MSC-collagen epicardial patch engraftment contributes to reverse remodeling of chronic MI.

Ischemic preconditioning promotes intrinsic vascularization and enhances survival of implanted cells in an in vivo tissue engineering model

Ischemic preconditioning (IPC) is a potent and effective means of protecting cells against ischemic injury. The protection has been demonstrated to involve release of paracrine factors that promote cell survival and angiogenesis, factors important for successful tissue engineering. The aim of the present study was to determine whether IPC of a vascular bed in vivo is an effective strategy to prepare it for tissue engineering with implanted cells. To test this hypothesis, an in vivo vascularized tissue engineering approach was employed, whereby polyacrylic chambers were placed around the femoral vessels of adult Sprague-Dawley rats. IPC was induced by 3 cycles of 5 min femoral artery occlusion interspersed with 5-min periods of reperfusion. Rats subjected to IPC generated bigger tissue constructs at 7 and 28 days postimplantation of empty chambers (∼50% increase in weight and volume, p<0.05). Morphometric counting of Masson trichrome stained tissue sections revealed significantly greater tissue construct volumes in ischemic preconditioned vascular beds at 7 and 28 days, increasing both fibrin matrix and vascularized tissue. Furthermore, morphometry of lectin-labeled blood vessels indicated an increase in vascular volume in IPC tissue constructs (∼100% increase vs. control, p<0.05). To investigate the cytoprotective effect of IPC, we implanted DiI-labeled neonatal rat cardiomyocytes in the chambers for 3 days, and IPC significantly reduced apoptosis of implanted cells as determined by the TUNEL assay and cleaved caspase-3 immunostaining. Furthermore, IPC significantly increased the cardiac muscle volume and vascular volume at 28 days after implantation of cardiomyocytes. In conclusion, in vivo IPC promotes survival of implanted cardiomyocytes and is associated with enhanced angiogenesis. IPC may represent a new approach to optimize tissue engineering with implanted cells.