Mesenchymal stem cells from ischemic heart disease patients improve left ventricular function after acute myocardial infarction

Mesenchymal stem cells (MSCs) from healthy donors improve cardiac function in experimental acute myocardial infarction (AMI) models. However, little is known about the therapeutic capacity of human MSCs (hMSCs) from patients with ischemic heart disease (IHD). Therefore, the behavior of hMSCs from IHD patients in an immune-compromised mouse AMI model was studied. Enhanced green fluorescent protein-labeled hMSCs from IHD patients (hMSC group: 2 x 10(5) cells in 20 microl, n = 12) or vehicle only (medium group: n = 14) were injected into infarcted myocardium of NOD/scid mice. Sham-operated mice were used as the control (n = 10). Cardiac anatomy and function were serially assessed using 9.4-T magnetic resonance imaging (MRI); 2 wk after cell transplantation, immunohistological analysis was performed. At day 2, delayed-enhancement MRI showed no difference in myocardial infarction (MI) size between the hMSC and medium groups (33 +/- 2% vs. 36 +/- 2%; P = not significant). A comparable increase in left ventricular (LV) volume and decrease in ejection fraction (EF) was observed in both MI groups. However, at day 14, EF was higher in the hMSC than in the medium group (24 +/- 3% vs. 16 +/- 2%; P < 0.05). This was accompanied by increased vascularity and reduced thinning of the infarct scar. Engrafted hMSCs (4.1 +/- 0.3% of injected cells) expressed von Willebrand factor (16.9 +/- 2.7%) but no stringent cardiac or smooth muscle markers. hMSCs from patients with IHD engraft in infarcted mouse myocardium and preserve LV function 2 wk after AMI, potentially through an enhancement of scar vascularity and a reduction of wall thinning.     

Pretreatment of rat bone marrow mesenchymal stem cells with a combination of hypergravity and 5-azacytidine enhances therapeutic efficacy for myocardial infarction

Background and Purpose: The in vivo cardiac differentiation and functional effects of unmodified adult bone marrow mesenchymal stem cells (BMSCs) after myocardial infarction (MI) is controversial. Our previous results suggested that hypergravity promoted the cardiomyogenic differentiation of BMSCs, and thus we postulated that ex vivo pretreatment of BMSCs using hypergravity and 5‐azacytidine (5‐Aza) would lead to cardiomyogenic differentiation and result in superior biological and functional effects on cardiac regeneration of infarcted myocardium. Methods: We used a rat MI model generated by ligation of the coronary artery. Homogeneous rat BMSCs were isolated, culture expanded, and differentiated into a cardiac lineage by adding hypergravity (2G) for 3 days and 5‐Aza (50 lmol/L, 24 h). Rats underwent BMSCs (labeled with DAPI) injection after the infarction and were randomized into five groups. Group A rats received the control medium, Group B rats received unmodified BMSCs, Group C rats received BMSCs treated with hypergravity, Group D rats received BMSCs treated with 5‐Aza, and Group E rats received BMSCs treated with 5‐Aza and hypergravity (n = 6). Results: After hypergravity and 5‐Aza treatment, BMSCs showed positive for the early muscle and cardiac markers GATA‐4, MEF‐2, and Nkx2‐5 with RT‐PCR. We also found that hypergravity could enhance the activities of MEF‐2 via promoting the nuclear export of HDAC5. The frozen section showed that the implanted BMSCs labeled with DAPI survived and angiogenesis was identified at the implantation site. In Groups B, C, D, and E rats, pre‐treated BMSCs colocalized with α‐actinin, and Group E rats showed a significantly larger increase in left ventricular function. Conclusions: The biological ex vivo cardiomyogenic differentiation of adult BMSCs with hypergravity and 5‐Aza prior to their transplantation is feasible and appears to improve their in vivo cardiac differentiation as well as the functional recovery in a rat model of the infarcted myocardium. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011     

Intravenous administration of mesenchymal stem cells improves cardiac function in rats with acute myocardial infarction through angiogenesis and myogenesis

Mesenchymal stem cells (MSCs) are pluripotent cells that differentiate into a variety of cells, including cardiomyocytes and endothelial cells. However, little information is available regarding the therapeutic potency of systemically delivered MSCs for myocardial infarction. Accordingly, we investigated whether intravenously transplanted MSCs induce angiogenesis and myogenesis and improve cardiac function in rats with acute myocardial infarction. MSCs were isolated from bone marrow aspirates of isogenic adult rats and expanded ex vivo. At 3 h after coronary ligation, 5 x 10(6) MSCs (MSC group, n=12) or vehicle (control group, n=12) was intravenously administered to Lewis rats. Transplanted MSCs were preferentially attracted to the infarcted, but not the noninfarcted, myocardium. The engrafted MSCs were positive for cardiac markers: desmin, cardiac troponin T, and connexin43. On the other hand, some of the transplanted MSCs were positive for von Willebrand factor and formed vascular structures. Capillary density was markedly increased after MSC transplantation. Cardiac infarct size was significantly smaller in the MSC than in the control group (24 +/- 2 vs. 33 +/- 2%, P <0.05). MSC transplantation decreased left ventricular end-diastolic pressure and increased left ventricular maximum dP/dt (both P <0.05 vs. control). These results suggest that intravenous administration of MSCs improves cardiac function after acute myocardial infarction through enhancement of angiogenesis and myogenesis in the ischemic myocardium.     

Mineralocorticoid receptor deficiency improves the therapeutic effects of mesenchymal stem cells for myocardial infarction via enhanced cell survival

The poor survival of stem cells seriously limits their therapeutic efficacy for myocardial infarction (MI). Mineralocorticoid receptor (MR) activation plays an important role in the pathogenesis of multiple cardiovascular diseases. Here, we examined whether MR silencing in bone marrow derived mesenchymal stem cells (MSCs) could improve MSCs’ survival and enhance their cardioprotective effects in MI. MSCs from male Sprague‐Dawley rats were transfected with adenoviral small interfering RNA to silence MR (siRNA‐MR). MR silencing decreased hypoxia‐induced MSCs’ apoptosis, as demonstrated by Annexin V/7‐AAD staining. The mechanisms contributing to the beneficial effects of MR depletion were associated with inhibiting intracellular reactive oxygen species production and increased Bcl‐2/Bax ratio. In vivo study, 1 × 10⁶ of MSCs with or without siRNA‐MR were injected into rat hearts immediately after MI. Depletion of MR could improve the MSCs’ survival significantly in infarcted myocardium, associated with more cardiac function improvement and smaller infarct size. Capillary density were also significantly higher in siRNA group with increased expression of vascular endothelial growth factor. Our study demonstrated that silencing MR promoted MSCs’ survival and repair efficacy in ischaemic hearts. MR might be a potential target for enhancing the efficacy of cell therapy in ischaemic heart disease.     

Implanted bone marrow-derived mesenchymal stem cells fail to metabolically stabilize or recover electromechanical function in infarcted hearts

Mesenchymal stem cells (MSCs) have been used with success in several clinical applications for clinical treatment of ischemic hearts. However, the reported effects of MSC-based therapy on myocardial infarction (MI) are inconsistent. In particular, the preventive effects of MSC-based therapy on arrhythmic sudden death and metabolic disorders after infarction remain controversial. Here, we investigated the effects of MSCs on reverse remodeling in an infarcted myocardium, and found that MSC-therapy failed to achieve the complete regeneration of infarcted myocardium. Histological analyses showed that although infarct size and interstitial fibrosis induced by MI recovered significantly after MSC treatment, these improvements were marginal, indicating that a significant amount of damaged tissue was still present. Furthermore, transplanted MSCs had slight anti-apoptotic and anti-inflammatory effects in MSC-implanted regions and no significant improvements in cardiac function were observed, suggesting that naïve MSCs might not be the right cell type to treat myocardial infarction. Furthermore, small ion profiling using ToF-SIMS revealed that the metabolic stabilization provided by the MSCs implantation was not significant compared to the sham group. Together, these results indicate that pretreatment of MSCs is needed to enhance the benefits of MSCs, particularly when MSCs are used to treat arrhythmogenicity and metabolically stabilize infarcted myocardium.     

Effects of Peroxisome Proliferator-Activated Receptor-δ Agonist on Cardiac Healing after Myocardial Infarction

Peroxisome proliferator-activated receptor-delta (PPAR-δ)-dependent signaling is associated with rapid wound healing in the skin. Here, we investigated the therapeutic effects of PPAR-δ-agonist treatment on cardiac healing in post-myocardial infarction (MI) rats. Animals were assigned to the following groups: sham-operated control group, left anterior descending coronary artery ligation (MI) group, or MI with administration of the PPAR-δ agonist GW610742 group. GW610742 (1 mg/kg) was administrated intraperitoneally after the operation and repeated every 3 days. Echocardiographic data showed no differences between the two groups in terms of cardiac function and remodeling until 4 weeks. However, the degrees of angiogenesis and fibrosis after MI were significantly higher in the GW610742-treated rats than in the untreated MI rats at 1 week following MI, which changes were not different at 2 weeks after MI. Naturally, PPAR-δ expression in infarcted myocardium was highest increased in 3 day after MI and then disappeared in 14 day after MI. GW610742 increased myofibroblast differentiation and transforming growth factor-beta 2 expression in the infarct zone at 7 days after MI. GW610742 also increased bone marrow-derived mesenchymal stem cell (MSC) recruitment in whole myocardium, and increased serum platelet-derived growth factor B, stromal-derived factor-1 alpha, and matrix metallopeptidase 9 levels at day 3 after MI. PPAR-δ agonists treatment have the temporal effect on early fibrosis of infarcted myocardium, which might not sustain the functional and structural beneficial effect.     

Mesenchymal stem cell transplantation for the infarcted heart: a role in minimizing abnormalities in cardiac-specific energy metabolism

Intense interest has been focused on cell-based therapy for the infarcted heart given that stem cells have exhibited the ability to reduce infarct size and mitigate cardiac dysfunction. Despite this, it is unknown whether mesenchymal stem cell (MSC) therapy can prevent metabolic remodeling following a myocardial infarction (MI). This study examines the ability of MSCs to rescue the infarcted heart from perturbed substrate uptake in vivo. C57BL/6 mice underwent chronic ligation of the left anterior descending coronary artery to induce a MI. Echocardiography was performed on conscious mice at baseline as well as 7 and 23 days post-MI. Twenty-eight days following the ligation procedure, hyperinsulinemic euglycemic clamps assessed in vivo insulin sensitivity. Isotopic tracer administration evaluated whole body, peripheral tissue, and cardiac-specific glucose and fatty acid utilization. To gain insight into the mechanisms by which MSCs modulate metabolism, mitochondrial function was assessed by high-resolution respirometry using permeabilized cardiac fibers. Data show that MSC transplantation preserves insulin-stimulated fatty acid uptake in the peri-infarct region (4.25 ± 0.64 vs. 2.57 ± 0.34 vs. 3.89 ± 0.54 μmol·100 g(-1)·min(-1), SHAM vs. MI + PBS vs. MI + MSC; P < 0.05) and prevents increases in glucose uptake in the remote left ventricle (3.11 ± 0.43 vs. 3.81 ± 0.79 vs. 6.36 ± 1.08 μmol·100 g(-1)·min(-1), SHAM vs. MI + PBS vs. MI + MSC; P < 0.05). This was associated with an enhanced efficiency of mitochondrial oxidative phosphorylation with a respiratory control ratio of 3.36 ± 0.18 in MSC-treated cardiac fibers vs. 2.57 ± 0.14 in the infarct-only fibers (P < 0.05). In conclusion, MSC therapy exhibits the potential to rescue the heart from metabolic aberrations following a MI. Restoration of metabolic flexibility is important given the metabolic demands of the heart and the role of energetics in the progression to heart failure.     

Effects of hepatocyte growth factor overexpressed bone marrow‐derived mesenchymal stem cells on prevention from left ventricular remodelling and functional improvement in infarcted rat hearts

Bone marrow‐derived mesenchymal stem cells (BM‐MSCs ) transplantation has been reported to be a promising therapy for myocardial infarction (MI). However, low survival rate of BM‐MSCs in infarcted heart is one of the major limitations for the perspective clinical application. In this study, we aimed to investigate the effect of hepatocyte growth factor (HGF) on left ventricular function improvement of HGF gene‐modified BM‐MSCs (HGF‐MSCs) after its delivery into the infarcted rat hearts. BM‐MSCs were isolated with fibroblast‐like morphology and expressed CD44+CD29+CD90+/CD34‐CD45‐CD31‐CD11a. After 5‐azacytidine induction in vitro, 20%–30% of the cells were positively stained for desmin, cardiac‐specific cardiac troponin I and connexin‐43. Histological staining revealed that 2 weeks after MI is an optimal time point with decreased neutrophil infiltration and increased vascular number. Minimal infarct size and best haemodynamic analysis were also observed after cell injection at 2 weeks compared with that of 1 h, 1 week or 4 weeks. Echocardiogram confirmed that transplantation with HGF‐MSCs significantly improved left ventricular function compared with other groups in rat MI models. MSCs and HGF‐MSCslabelled with DAPI were detected 4 weeks after MI in the infarcted area. Decreased infarcted scar area and increased angiogenesis formation could be found in HGF‐MSCs group than in other groups as demonstrated by hematoxylin and eosin (H&E) staining and factor VIII staining. These results indicate that HGF‐MSCs transplantation could enhance the contractile function and attenuate left ventricular remodelling efficiently in rats with MI. Copyright © 2012 John Wiley & Sons, Ltd.     

Use of human embryonic stem cell derived-mesenchymal cells for cardiac repair

Human mesenchymal stem cells (hMSC) have proven beneficial in the repair and preservation of infarcted myocardium. Unfortunately, MSCs represent a small portion of the bone marrow and require ex vivo expansion. To further advance the clinical usefulness of cellular cardiomyoplasty, derivation of "MSC-like" cells that can be made available "off-the-shelf" are desirable. Recently, human embryonic stem cell-derived mesenchymal cells (hESC-MC) were described. We investigated the efficacy of hESC-MC for cardiac repair after myocardial infarction (MI) compared to hMSC. Because of increased efficacy of cell delivery, cells were embedded into collagen patches and delivered to infarcted myocardium. Culture of hMSC and hESC-MCs in collagen patches did not induce differentiation or significant loss in viability. Transplantation of hMSC and hES-MC patches onto infarcted myocardium of athymic nude rats prevented adverse changes in infarct wall thickness and fractional area change compared to a non-viable patch control. Hemodynamic assessment showed that hMSCs and hES-MC patch application improved end diastolic pressure equivalently. There were no changes in systolic function. hES-MC and hMSC construct application enhanced neovessel formation compared to a non-viable control, and each cell type had similar efficacy in stimulating endothelial cell growth in vitro. In summary, the use of hES-MC provides similar efficacy for cellular cardiomyoplasty as compared to hMSC and may be considered a suitable alternative for cell therapy.     

DITPA stimulates arteriolar growth and modifies myocardial postinfarction remodeling

Myocardial infarction (MI) is characterized by ventricular remodeling, hypertrophy of the surviving myocardium, and an insufficient angiogenic response. Thyroxine is a powerful stimulus for myocardial angiogenesis. Male rats that underwent coronary artery ligation and subsequent MI were given 3,5-diiodothyropropionic acid (DITPA; MI+DITPA group) during a 3-wk period. We evaluated ventricular remodeling using echocardiography and histology and myocardial vessel growth using image analysis. Protein expression was assessed using Western blotting and immunohistochemistry. This study tested the hypothesis that the thyroxine analog DITPA facilitates angiogenesis and influences postinfarction remodeling in the surviving hypertrophic myocardium. The increase in the region of akinesis (infarct expansion) was blunted in the MI+DITPA rats compared with the MI group (3 vs. 21%); the treated rats had smaller percent increases in the left ventricular (LV) volume (64 +/- 14 vs. 95 +/- 12) and the LV volume-to-mass ratio (47 +/- 13 vs. 84 +/- 10) as well as a blunted decrease in ejection fraction (-9 +/- 8 vs. -30 +/- 7%). Arteriolar length density was higher after treatment in the largest (>50% of the free wall) infarcts (64 +/- 3 vs. 43 +/- 7). Angiogenic growth factors [vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF)] and the angiopoietin receptor tyrosine kinase with immunoglobulin and epidermal growth factor homology domains (Tie-2) values were elevated during the first week after infarction. DITPA did not cause additional increases in VEGF or Tie-2 values but did induce an increase in bFGF value after 3 days of treatment. This study provides the first evidence for an anatomical basis, i.e., attenuated ventricular remodeling and arteriolar growth, for improved function attributed to DITPA therapy of the infarcted heart. The favorable influences of DITPA on LV remodeling after large infarction are principally due to border zone preservation.     

Microvascular transport model predicts oxygenation changes in the infarcted heart after treatment

Chronic heart failure is most commonly due to ischemic cardiomyopathy after a previous myocardial infarction (MI). Rebuilding lost myocardium to prevent heart failure mandates a neovasculature able to nourish new cardiomyocytes. Previously we have used a series of novel techniques to directly measure the ability of the scar neovasculature to deliver and exchange oxygen at 1-4 wk after MI in rats following left coronary artery ligation. In this study, we have developed a morphologically realistic mathematical model of oxygen transport in cardiac tissue to help in deciding what angiogenic strategies should be used to rebuild the vasculature. The model utilizes microvascular morphology of cardiac tissue based on available morphometric images and is used to simulate experimentally measured oxygen levels after MI. Model simulations of relative oxygenation match experimental measurements closely and can be used to simulate distributions of oxygen concentration in normal and infarcted rat hearts. Our findings indicate that both vascular density and vascular spatial distribution play important roles in cardiac tissue oxygenation after MI. Furthermore, the model can simulate relative changes in tissue oxygen levels in infarcted tissue treated with proangiogenic compounds such as losartan. From the minimum oxygen concentration myocytes need to maintain their normal function, we estimate that 2 wk after MI 29% of the myocardium is severely hypoxic and that the vascular density of the infarcted tissue should reach 75% of normal tissue to ensure that no areas of the myocardium are critically hypoxic.     

Bone marrow mesenchymal stem cells for post-myocardial infarction cardiac repair: microRNAs as novel regulators

Transplantation of bone marrow-derived mesenchymal stem cells (MSCs) is safe and may improve cardiac function and structural remodelling in patients following myocardial infarction (MI). Cardiovascular cell differentiation and paracrine effects to promote endogenous cardiac regeneration, neovascularization, anti-inflammation, anti-apoptosis, anti-remodelling and cardiac contractility, may contribute to MSC-based cardiac repair following MI. However, current evidence indicates that the efficacy of MSC transplantation was unsatisfactory, due to the poor viability and massive death of the engrafted MSCs in the infarcted myocardium. MicroRNAs are short endogenous, conserved, non-coding RNAs and important regulators involved in numerous facets of cardiac pathophysiologic processes. There is an obvious involvement of microRNAs in almost every facet of putative repair mechanisms of MSC-based therapy in MI, such as stem cell differentiation, neovascularization, apoptosis, cardiac remodelling, cardiac contractility and arrhythmias, and others. It is proposed that therapeutic modulation of individual cardiovascular microRNA of MSCs, either mimicking or antagonizing microRNA actions, will hopefully enhance MSC therapeutic efficacy. In addition, MSCs may be manipulated to enhance functional microRNA expression or to inhibit aberrant microRNA levels in a paracrine manner. We hypothesize that microRNAs may be used as novel regulators in MSC-based therapy in MI and MSC transplantation by microRNA regulation may represent promising therapeutic strategy for MI patients in the future.     

Electrotonic remodeling following myocardial infarction in dogs susceptible and resistant to sudden cardiac death.

Passive electrical remodeling following myocardial infarction (MI) is well established. These changes can alter electrotonic loading and trigger the remodeling of repolarization currents, a potential mechanism for ventricular fibrillation (VF). However, little is known about the role of passive electrical markers as tools to identify VF susceptibility post-MI. This study investigated electrotonic remodeling in the post-MI ventricle, as measured by myocardial electrical impedance (MEI), in animals prone to and resistant to VF. MI was induced in dogs by a two-stage left anterior descending (LAD) coronary artery ligation. Before infarction, MEI electrodes were placed in remote (left circumflex, LCX) and infarcted (LAD) myocardium. MEI was measured in awake animals 1, 2, 7, and 21 days post-MI. Subsequently, VF susceptibility was tested by a 2-min LCX occlusion during exercise; 12 animals developed VF (susceptible, S) and 12 did not (resistant, R). The healing infarct had lower MEI than the normal myocardium. This difference was stable by day 2 post-MI (287 +/- 32 Omega vs. 425 +/- 62 Omega, P < 0.05). Significant differences were observed between resistant and susceptible animals 7 days post-MI; susceptible dogs had a wider electrotonic gradient between remote and infarcted myocardium (R: 89 +/- 60 Omega vs. S: 180 +/- 37 Omega). This difference increased over time in susceptible animals (252 +/- 53 Omega at 21 days) due to post-MI impedance changes on the remote myocardium. These data suggest that early electrotonic changes post-MI could be used to assess later arrhythmia susceptibility. In addition, passive-electrical changes could be a mechanism driving active-electrical remodeling post-MI, thereby facilitating the induction of arrhythmias.     

Transplantation of embryonic stem cells improves cardiac function in postinfarcted rats.

Massive loss of cardiac myocytes after myocardial infarction (MI) is a common cause of heart failure. The present study was designed to investigate the improvement of cardiac function in MI rats after embryonic stem (ES) cell transplantation. MI in rats was induced by ligation of the left anterior descending coronary artery. Cultured ES cells used for cell transplantation were transfected with the marker green fluorescent protein (GFP). Animals in the treated group received intramyocardial injection of ES cells in injured myocardium. Compared with the MI control group injected with an equivalent volume of the cell-free medium, cardiac function in ES cell-implanted MI animals was significantly improved 6 wk after cell transplantation. The characteristic phenotype of engrafted ES cells was identified in implanted myocardium by strong positive staining to sarcomeric alpha-actin, cardiac alpha-myosin heavy chain, and troponin I. GFP-positive cells in myocardium sectioned from MI hearts confirmed the survival and differentiation of engrafted cells. In addition, single cells isolated from cell-transplanted MI hearts showed rod-shaped GFP-positive myocytes with typical striations. The present data demonstrate that ES cell transplantation is a feasible and novel approach to improve ventricular function in infarcted failing hearts.     

In situ delivery of bone marrow cells and mesenchymal stem cells improves cardiovascular function in hypertensive rats submitted to myocardial infarction

This work aimed to evaluate cardiac morphology/function and histological changes induced by bone marrow cells (BMCs) and cultured mesenchymal stem cells (MSCs) injected at the myocardium of spontaneously hypertensive rats (SHR) submitted to surgical coronary occlusion. Female syngeneic adult SHR, submitted (MI) or not (C) to coronary occlusion, were treated 24 h later with in situ injections of normal medium (NM), or with MSCs (MSC) or BMCs (BM) from male rats. The animals were evaluated after 1 and 30 days by echocardiography, histology of heart sections and PCR for the Y chromosome. Improved ejection fraction and reduced left ventricle infarcted area were observed in MSC rats as compared to the other experimental groups. Treated groups had significantly reduced lesion tissue score, increased capillary density and normal (not-atrophied) myocytes, as compared to NM and C groups. The survival rate was higher in C, NM and MSC groups as compared to MI and BM groups. In situ injection of both MSCs and BMCs resulted in improved cardiac morphology, in a more physiological model of myocardial infarction represented by surgical coronary occlusion of spontaneously hypertensive rats. Only treatment with MSCs, however, ameliorated left ventricle dysfunction, suggesting a positive role of these cells in heart remodeling in infarcted hypertensive subjects.     

Preservation of coronary reserve by ivabradine-induced reduction in heart rate in infarcted rats is associated with decrease in perivascular collagen

We tested the hypothesis that chronically reducing the heart rate in infarcted middle-aged rats using ivabradine (IVA) would induce arteriolar growth and attenuate perivascular collagen and, thereby, improve maximal perfusion and coronary reserve in the surviving myocardium. Myocardial infarction (MI) was induced in 12-mo-old male Sprague-Dawley rats, which were then treated with either IVA (10.5 mg.kg(-1).day(-1); MI + IVA) or placebo (MI) via intraperitoneal osmotic pumps for 4 wk. Four weeks of IVA treatment limited the increase in left ventricular end-diastolic pressure and the decrease in ejection fraction but did not affect the size of the infarct, the magnitude of myocyte hypertrophy, or the degree of arteriolar and capillary growth. However, treatment reduced interstitial and periarteriolar collagen in the surviving myocardium of MI + IVA rats. The reduced periarteriolar collagen content was associated with improvement in maximal myocardial perfusion and coronary reserve. Although the rates of proliferation of periarteriolar fibroblasts were similar in the MI and MI + IVA groups, the expression levels of the AT(1) receptor and transforming growth factor (TGF)-beta(1) in the myocardium, as well as the plasma level of the ANG II peptide, were lower in treated rats 14 days after MI. Therefore, our data reveal that improved maximal myocardial perfusion and coronary reserve in MI + IVA rats are most likely the result of reduced periarteriolar collagen rather than enhanced arteriolar growth.     

VEGF enhances functional improvement of postinfarcted hearts by transplantation of ESC-differentiated cells.

Despite considerable advances in medicine, the incidence of heart failure remains high in patients after myocardial infarction (MI). This study investigated the effects of engrafted early-differentiated cells (EDCs) from mouse embryonic stem cells, with or without transfection of vascular endothelial growth factor (VEGF) cDNA (phVEGF(165)), on cardiac function in postinfarcted mice. EDCs were transfected with green fluorescent protein (GFP) cDNA and transplanted into infarcted myocardium. Compared with the MI mice receiving cell-free medium, cardiac function was significantly improved in the MI mice 6 wk after transplantation of EDCs. Moreover, improvement of heart function was significantly greater in the mice implanted with EDCs overexpressing VEGF (EDCs-VEGF) than with EDCs alone. Frozen sections of infarcted myocardium with EDCs or EDCs-VEGF transplantation showed GFP-positive tissue. The area with positive immunostaining for cardiac troponin I and alpha-myosin heavy chain was larger in injured myocardium with EDCs or EDCs-VEGF transplantation than with medium injection. Transplantation of EDCs or EDCs-VEGF significantly increased the number of blood vessels in the MI area. However, the density of capillaries was significantly higher in the EDCs-VEGF animals than in the EDC mice. Double staining for GFP and connexin-43 was positive in injured myocardium with EDC transplantation. Our data demonstrate that engrafted EDCs or EDCs-VEGF regenerated cardiac tissue and significantly improved cardiac function in postinfarcted hearts. The novel EDCs-VEGF synergistic approach may have an important impact on future cell therapy for patients experiencing MI or heart failure.     

恒磁场增强心肌梗死大鼠骨髓间充质干细胞移植后心脏功能改善

目的：研究恒磁场对心肌梗死大鼠骨髓间充质干细胞（bone marrow-derived mesenchymal stem cells,BMSCs）移植后心脏功能的影响。方法：取180g,9-12周龄雄性SD大鼠骨髓,以密度梯度离心分离出单个核细胞（MNCs）,于体外培养并传代培养出骨髓间充质干细胞（MSCs）。制作大鼠心肌梗死模型,将1.5×106BMSCs注射入梗死梗死区周围,分为磁场照射＋BMSCs植入组、BMSCs植入组及空白对照组。4周后处死动物,每组5只大鼠。磁场照射组用0.4 T恒磁场置于心前区30 min,每日1次,共7天。用颈动脉插管法测定心脏功能,Masson三色染色测定梗死面积,VWF VIII染色计算血管密度。结果：与对照组相比BMSCs组以及磁场组均可以显著提高左心室收缩压（LVSP）,dp/dtmax以及-dp/dtmax,减少LVEDP（P〈0.05）。但是,磁场组与BMSCs组相比LVSP,左心室内压最大上升速率（dp/dtmax）以及左心室内压最大下降速率（-dp/dtmax）增高,左心室舒张末压（LVEDP）减少（P〈0.05）。与对照组相比BMSCs组以及磁场组均可以显著提高减少心梗面积（P〈0.05）。磁场组与BMSCs组相比心梗面积减少（P〈0.05）。与对照组相比BMSCs组以及磁场组均可以显著提高增加血管密度（P〈0.05）。磁场组与BMSCs组相比血管密度增加（P〈0.05）。结论：恒磁场具有加强移植BMSCs改善心脏功能的作用。     

Cardiomyogenic differentiation-independent improvement of cardiac function by human cardiomyocyte progenitor cell injection in ischaemic mouse hearts

We previously showed that human cardiomyocyte progenitor cells (hCMPCs) injected after myocardial infarction (MI) had differentiated into cardiomyocytes in vivo 3 months after MI. Here, we investigated the short-term (2 weeks) effects of hCMPCs on the infarcted mouse myocardium. MI was induced in immunocompromised (NOD/scid) mice, immediately followed by intramyocardial injection of hCMPCs labelled with enhanced green fluorescent protein (hCMPC group) or vehicle only (control group). Sham-operated mice served as reference. Cardiac performance was measured 2 and 14 days after MI by magnetic resonance imaging at 9.4 T. Left ventricular (LV) pressure-volume measurements were performed at day 15 followed by extensive immunohistological analysis. Animals injected with hCMPCs demonstrated a higher LV ejection fraction, lower LV end-systolic volume and smaller relaxation time constant than control animals 14 days after MI. hCMPCs engrafted in the infarcted myocardium, did not differentiate into cardiomyocytes, but increased vascular density and proliferation rate in the infarcted and border zone area of the hCMPC group. Injected hCMPCs engraft into murine infarcted myocardium where they improve LV systolic function and attenuate the ventricular remodelling process 2 weeks after MI. Since no cardiac differentiation of hCMPCs was evident after 2 weeks, the observed beneficial effects were most likely mediated by paracrine factors, targeting amongst others vascular homeostasis. These results demonstrate that hCMPCs can be applied to repair infarcted myocardium without the need to undergo differentiation into cardiomyocytes.     

Mesenchymal stem cell‐loaded cardiac patch promotes epicardial activation and repair of the infarcted myocardium

Cardiac patch is considered a promising strategy for enhancing stem cell therapy of myocardial infarction (MI). However, the underlying mechanisms for cardiac patch repairing infarcted myocardium remain unclear. In this study, we investigated the mechanisms of PCL/gelatin patch loaded with MSCs on activating endogenous cardiac repair. PCL/gelatin patch was fabricated by electrospun. The patch enhanced the survival of the seeded MSCs and their HIF‐1α, Tβ4, VEGF and SDF‐1 expression and decreased CXCL14 expression in hypoxic and serum‐deprived conditions. In murine MI models, the survival and distribution of the engrafted MSCs and the activation of the epicardium were examined, respectively. At 4 weeks after transplantation of the cell patch, the cardiac functions were significantly improved. The engrafted MSCs migrated across the epicardium and into the myocardium. Tendency of HIF‐1α, Tβ4, VEGF, SDF‐1 and CXCL14 expression in the infarcted myocardium was similar with expression in vitro. The epicardium was activated and epicardial‐derived cells (EPDCs) migrated into deep tissue. The EPDCs differentiated into endothelial cells and smooth muscle cells, and some of EPDCs showed to have differentiated into cardiomyocytes. Density of blood and lymphatic capillaries increased significantly. More c‐kit⁺ cells were recruited into the infarcted myocardium after transplantation of the cell patch. The results suggest that epicardial transplantation of the cell patch promotes repair of the infarcted myocardium and improves cardiac functions by enhancing the survival of the transplanted cells, accelerating locality paracrine, and then activating the epicardium and recruiting endogenous c‐kit⁺ cells. Epicardial transplantation of the cell patch may be applied as a novel effective MI therapy.