Growth and differentiation of rat bone marrow stromal cells: does 5-azacytidine trigger their cardiomyogenic differentiation?

OBJECTIVE: The potential use of bone marrow stromal cells (MSCs) as a cellular therapy for chronic cardiac diseases relies on the ability of the cell to replicate extensively in vitro and to give rise to myogenic cells that can replace the damaged cardiomyocytes. For this reason the present study investigated the replication lifespan and chemical-induced cardiomyogenic differentiation of rat MSCs in vitro. METHODS: The primary and the successively passaged Wistar rat MSCs were exposed to different concentrations (3, 5 and 10 microM) of 5-azacytidine using different methods (single- or repeat-treatment). The growth properties and the fate of the cells were compared to their untreated counterparts by cell counting, immunocytochemistry and Western analysis. RESULTS: When seeded at a density of 2845 cells/cm(2) and cultured under common conditions, rat MSCs could be expanded up to 21.94 cell doublings in 30 days of successive subcultures. This was accompanied by a gradual loss of their replication ability with passages. When treated with 5-azacytidine for 24 h at day 3 of primary culture and the first subculture, the growth properties of the MSCs were not obviously affected. Neither the spontaneously beating cells nor the formation of myotubes were found in the primary and first passaged MSCs after a single treatment with 5-azacytidine and in cultures which underwent repeated 5-azacytidine-treatments during continuous subculturing to passage 2. The expressions of cardiac troponin I, cardiac myosin heavy chain and connexin 43 by the 5-azacytidine-treated MSCs were also undetectable at both immunocytochemistry and Western blot levels. The specificity and reliability of the detection methods were technically confirmed with cultured rat cardiomyocytes. CONCLUSIONS: Rat MSCs cannot be extensively expanded in vitro or be induced to differentiate in an expected cardiomyogenic way by 5-azacytidine-treatment, if the cells are not immortalized.     

兔骨髓间充质干细胞自体移植治疗扩张型心肌病的实验研究

目的 研究骨髓间充质干细胞(MSCs)自体移植于扩张型心肌病后的增殖分化情况和对心功能的保护作用。方法 日本大耳白兔随机分为4组:(1)扩张型心肌病(DCM)细胞移植组(n=12);(2)DCM对照组(n=12);(3)DCM假手术组(n=12);(4)正常对照组(n=10)。分离培养DCM细胞移植组MSCs后,前3组动物用盐酸阿霉素建立兔DCM模型,第4组注射等量生理盐水。模型建立成功后第3周,将5溴脱氧尿嘧啶(BrdU)标记的MSCs自体移植到细胞移植组心肌内,对照组注射培养基,假手术组只开胸,不做注射。4周后采用超声心动图和血流动力学参数评价各组动物的心脏结构和功能,并取移植区心肌组织行免疫荧光染色以观察移植细胞的增殖分化情况。另选部分心肌组织做HE染色查看心肌组织形态学改变。结果 与正常对照组相比,DCM各组心功能明显受损。细胞移植4周后,可以在移植组心肌内找到BrdU标记的阳性细胞,且一部分表现为心肌特异性肌钙蛋白T染色阳性,一部分Ⅷ因子相关抗原染色阳性并参与形成新生血管,其他组中没有发现。且细胞移植组心功能较对照组和假手术组有明显改善。组织学检查示前3组均有心肌细胞变性坏死。结论 MSCs自体移植到DCM后有可能增殖分化为心肌样细胞和血管内皮样细胞并改善心功能。     

Efficient cardiomyogenic differentiation of embryonic stem cell by fibroblast growth factor 2 and bone morphogenetic protein 2.

BACKGROUND: Despite the pluripotency of embryonic stem (ES) cells, the specific control of their cardiomyogenic differentiation remains difficult. The aim of the present study was to investigate whether growth factors may efficiently enhance the in vitro cardiac differentiation of ES cells. METHODS AND RESULTS: Recombinant growth factors at various concentrations or their inhibitors were added according to various schedules during the cardiomyogenic differentiation of ES cells. Cardiomyogenic differentiation was assessed by mRNA and protein expressions of several cardiomyocyte-specific genes. Basic fibroblast growth factor-2 (FGF-2) and/or bone morphogenetic protein-2 (BMP-2) efficiently enhanced the cardiomyogenic differentiation, but only when they were added at the optimal concentration (1.0 ng/ml in FGF-2 and 0.2 ng/ml in BMP-2; relatively lower than expected in both cases) for the first 3 days. Inhibition of FGF-2 and/or BMP-2 drastically suppressed the cardiomyogenic differentiation. CONCLUSION: FGF-2 and BMP-2 play a crucial role in early cardiomyogenesis. The achievement of efficient cardiac differentiation using both growth factors may facilitate ES cell-derived cell therapy for heart diseases as well as contribute to developmental studies of the heart.     

Improved graft mesenchymal stem cell survival in ischemic heart with a hypoxia-regulated heme oxygenase-1 vector.

OBJECTIVES: The goal of this study was to modify mesenchymal stem cells (MSCs) cells with a hypoxia-regulated heme oxygenase-1 (HO-1) plasmid to enhance the survival of MSCs in acute myocardial infarction (MI) heart. BACKGROUND: Although stem cells are being tested clinically for cardiac repair, graft cells die in the ischemic heart because of the effects of hypoxia/reoxygenation, inflammatory cytokines, and proapoptotic factors. Heme oxygenase-1 is a key component in inhibiting most of these factors. METHODS: Mesenchymal stem cells from bone marrow were transfected with either HO-1 or LacZ plasmids. Cell apoptosis was assayed in vitro after hypoxia-reoxygen treatment. In vivo, 1 x 10(6) of male MSC(HO-1), MSC(LacZ), MSCs, or medium was injected into mouse hearts 1 h after MI (n = 16/group). Cell survival was assessed in a gender-mismatched transplantation model. Apoptosis, left ventricular remodeling, and cardiac function were tested in a gender-matched model. RESULTS: In the ischemic myocardium, the MSC(HO-1) group had greater expression of HO-1 and a 2-fold reduction in the number of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate in situ nick end labeling-positive cells compared with the MSC(LacZ) group. At seven days after implantation, the survival MSC(HO-1) was five-fold greater than the MSC(LacZ) group; MSC(HO-1) also attenuated left ventricular remodeling and enhanced the functional recovery of infarcted hearts two weeks after MI. CONCLUSIONS: A hypoxia-regulated HO-1 vector modification of MSCs enhances the tolerance of engrafted MSCs to hypoxia-reoxygen injury in vitro and improves their viability in ischemic hearts. This demonstration is the first showing that a physiologically inducible vector expressing of HO-1 genes improves the survival of stem cells in myocardial ischemia.     

骨髓间充质干细胞同种移植治疗急性心肌梗死的实验研究

目的探讨骨髓间充质干细胞(MSCs)同种移植治疗急性心肌梗死的可行性。方法50只Wistar大鼠随机分为两组,对照组和移植组各25只。应用液氮冷冻法制作心肌梗死模型。移植组梗死部位注入经5-氮胞苷(5-aza)诱导和溴氮胞苷标记的大鼠MSCs,对照组梗死部位注入等容量DMEM液。分别于术前1天、术后1周和术后4周行超声心动图检查,以收缩期峰值速度(Vs)、左室舒张末容积(LVEDV)和左室射血分数(LVEF)为指标评价心功能。移植组于术后4周处死,移植心肌行溴氮胞苷免疫组化染色。结果对照组(n=13)和移植组(n=15)相比,术前及术后1周的心功能差异均无统计学意义(P>0.05),术后4周差异有统计学意义(P<0.05),术后4周移植组心功能明显优于对照组。移植部位免疫组化可见溴氮胞苷染色阳性细胞。结论经5-aza诱导的MSCs同种移植入大鼠急性心肌梗死模型的受损心肌后能存活并改善宿主的心功能。     

Mobilization of Mesenchymal Stem Cells by Granulocyte Colony-stimulating Factor in Rats with Acute Myocardial Infarction

PURPOSE: Intravenous delivery of mesenchymal stem cells (MSCs), a noninvasive strategy for myocardial repair after acute myocardial infarction (MI), is limited by the low percentage of MSCs migration to the heart. The purpose of this study was to test whether granulocyte colony-stimulating factor (G-CSF) would enhance the colonization of intravenously infused MSCs in damaged heart in a rat model of acute MI. METHODS: After induction of anterior MI, Sprague-Dawley rats were randomized to receive: (1) saline (n = 9); (2) MSCs (n = 15); and (3) MSCs plus G-CSF (50 mug/kg/day for 5 consecutive days, n = 13). RESULTS: Flow cytometry revealed that G-CSF slightly increased surface CXCR4 expression on MSCs in vitro. After completion of G-CSF administration, MSCs showed a significantly lower colonization in bone marrow and a trend toward higher localization in the infarcted myocardium. At 3 months, vessel density in the infarct region of heart was significantly increased in MSCs group and trended to increase in MSCs + G-CSF group. However, echocardiographic and hemodynamic parameters, including left ventricular (LV) end-diastolic diameters, ejection fraction, and +/-dP/dt (max), were not statistically different. Morphological analysis showed that infarct size and collagen content were similar in the three groups. Immunohistochemistry revealed that the combined therapy accelerated endothelial recovery of the blood vessels in the ischemic myocardium. However, myocardial regeneration resulting from MSCs differentiation was not observed. CONCLUSIONS: G-CSF enhanced the migration of systemically delivered MSCs from bone marrow to infarcted heart. However, the beneficial effect of this kind of migration is limited, as cardiac function did not improve.     

Preconditioning enhances cell survival and differentiation of stem cells during transplantation in infarcted myocardium

AIMS: We hypothesized that preconditioning (PC) with stromal-derived factor 1 alpha (SDF-1) significantly enhances cell survival, proliferation, and engraftment of bone marrow-derived mesenchymal stem cells (MSCs) via SDF-1/CXCR4 signaling. METHODS AND RESULTS: MSCs were cultured and then incubated in medium for 60 min without SDF-1 (control group) or with SDF-1 0.05 microg/mL (SDF-1 group) or CXCR4-selective antagonist, AMD 3100 (AMD) (5 microg/mL, AMD group) or SDF-1 and AMD (0.05 microg/mL, 5 microg/mL, respectively, SDF-1+AMD group). MSCs were treated for 60 min, washed in normal medium, and then exposed to H2O2 (100 micromol/L) for 60 min to determine the effects of various treatments on cell injury, viability, and proliferation. For in vivo studies, rats were grouped (n = 6) after left anterior descending coronary artery ligation to receive 20 microL Dulbecco's modified Eagle's medium without cells or with 5 x 10(5) non-preconditioned MSCs (control group), SDF-1 preconditioned MSCs (SDF-1 group), AMD (AMD group), or MSCs treated with SDF-1 plus AMD (SDF-1+AMD group). Heart function, infarct size, fibrosis, and MSC proliferation and differentiation in infarcted myocardium were determined after 4 weeks. In vitro data showed a marked increase in cell viability and proliferation following SDF-1 PC. In vivo data in preconditioned group showed a robust cell proliferation, reduction in infarct size and fibrosis, and significant improvement in cardiac function. Effects of SDF-1 PC were abrogated by CXCR4 antagonist. CONCLUSION: We conclude that PC with the chemokine SDF-1 suppresses MSCs apoptosis, enhances their survival, engraftment, and vascular density, and improves myocardial function via SDF/CXCR4 signaling. Chemokine PC is a novel approach for enhancing stem cell survival and regeneration of infarcted myocardium.     

同种异体移植骨髓间充质干细胞治疗大鼠心肌梗死

目的　探讨同种异体骨髓间充质干细胞 (MSCs)在梗死大鼠心脏局部存活、迁移、分化及对心功能的影响 ;明确同种异体细胞移植治疗心肌梗死 (MI)的可行性及效果。方法　雌性Wistar大鼠 3 5只 ,随机分为正常对照组、急性心肌梗死 (AMI)组及MI MSCs治疗组。分离纯化雄性Wistar大鼠骨髓MSCs ,于左冠状动脉前降支结扎后 1～ 3h植入到雌性大鼠心脏组织 ,移植后 10周检测心功能并取心脏检测各种相关指标。结果　异体大鼠MSCs经纯化后可在梗死心脏组织定居、生存 ,并与宿主心肌纤维排列方向一致 ,免疫组化检测胞质心肌特异蛋白染色阳性 ,与MI组比较 ,异体细胞移植组左室收缩压升高 (P <0 0 5) ,舒张末压明显降低 (P <0 0 1)、左心室内压最大上升和下降速率显著增快 (P <0 0 5) ,梗死边缘区心肌面毛细血管数目明显增加 (P <0 0 5) ,多功能真彩色病理图像分析系统显示MI面积缩小 (P <0 0 5)。结论　同种异体MSCs移植治疗MI可行、有效     

兔骨髓间充质干细胞移植后移植细胞凋亡的实验研究

目的利用TUNEL法检测5-氮胞苷体外诱导骨髓间充质干细胞（MSCs）移植后的凋亡情况。方法5-氮胞苷体外诱导骨髓间充质干细胞MSCs向肌源性心肌细胞分化,通过免疫组化,鉴定诱导后的MSCs是否向类心肌细胞转化。建立兔心肌梗死模型,将细胞移植于心梗区域。移值2周后,利用TUNEL法检测植入细胞的凋亡率。结果移植2周后,可见DAPI标记带蓝色荧光的供体细胞核,分布比较广泛,形态呈椭圆形类似心肌细胞核,并与心肌纤维排列方向一致,证明移植细胞已存活。移值细胞表达troponinT,证明移植的MSCs分化为类心肌细胞。移植细胞均出现不同程度细胞凋亡。结论移植的MSCs细胞可在缺血的心肌组织存活,并分化为类心肌细胞,但移植细胞均出现不同程度凋亡。     

Magnetic resonance imaging of targeted catheter-based implantation of myogenic precursor cells into infarcted left ventricular myocardium

OBJECTIVES: This study was designed to test the hypothesis that myocardial implantation of myogenic precursor cells (MPC) loaded with iron oxide can be reliably detected in vivo by cardiac magnetic resonance imaging (MRI). BACKGROUND: In vivo imaging of targeted catheter-based implantation of MPC into infarcted left ventricular (LV) myocardium is unavailable. METHODS: The study was conducted in seven farm pigs (four with anterior myocardial infarction), in which autologous MPC were injected through a percutaneous catheter allowing for LV electromechanical mapping and guided micro-injections into normal and infarcted myocardium. Cardiac MRI was used to detect implanted MPC previously loaded with iron oxide nanoparticles. RESULTS: Magnetic resonance imaging data were compared with LV electromechanical mapping and cross-registered pathology. All 9 injections into normal and 12 injections into locally damaged myocardium were detected on T2-weighted spin echo and inversion-recovery true-fisp MRI (low signal areas) with good anatomical concordance with sites of implantation on electromechanical maps. All sites of injection were confirmed on pathology that showed in all infarct animals iron-loaded MPC at the center and periphery of the infarct as expected from MRI. CONCLUSIONS: Targeted catheter-based implantation of iron-loaded MPC into locally infarcted LV myocardium is accurate and can be reliably demonstrated in vivo by cardiac MRI. The ability to identify noninvasively intramyocardial cell implantation may be determinant for future experimental studies designed to analyze subsequent effects of such therapy on detailed segmental LV function.     

Endoventricular porcine autologous myoblast transplantation can be successfully achieved with minor mechanical cell damage

OBJECTIVE: Transplantation of skeletal myogenic precursor cells (mpc) into the myocardium using a non-surgical procedure. METHODS: Closed-chest mpc transplantation was assessed in pigs using the NOGA-Biosense device allowing both electromechanical mapping of the left ventricle (LV), and guided mpc injections through endocardium. RESULTS: We successively established that: (1) adequate preimplantation handling of mpc can be achieved when mpc are kept in 0.1% serum albumin-containing medium until implantation; (2) mpc are neither retained nor destroyed in the catheter or the needle and their passage does not affect their survival, growth and differentiation; (3) large numbers of autologous mpc can be actually transplanted in the LV myocardium by transendocardial route, as assessed by post-mortem examination of pigs injected with iron-loaded mpc; (4) cell injection into the myocardium does not induce conspicuous cell mortality since more than 80% of mpc recovered from LV tissue are alive 15 min after injection; (5) mpc injections can be guided into circumscribed LV targets such as infarcted areas, as assessed by comparison of map injection sites with location of iron-loaded mpc at post-mortem examination of LV myocardium. CONCLUSION: This new approach may pave the way for a large spectrum of cell therapies targeting myocardial diseases.     

心肌细胞裂解液对骨髓间充质干细胞向心肌细胞分化诱导作用的研究

目的通过向骨髓间充质干细胞(MSCs)培养体系中添加心肌细胞裂解液的方法,体外模拟心肌微环境,观察MSCs向心肌细胞分化的诱导作用,并与诱导分化剂5-氮杂胞苷(5-aza)比较。方法分离新生乳鼠的心肌细胞并制成心肌细胞裂解液,自成年大鼠骨髓中分离MSCs,用含有心肌细胞裂解液的培养基(A组)、含有5-aza的培养基(B组)、含有5-aza和心肌细胞裂解液的培养基(c组)以及普通培养基(对照组)培养。观察细胞形态的改变,并通过免疫组化分析分化后细胞表达α-肌动蛋白、心脏特异性肌钙蛋白T(cTnT)、连接蛋白43及CD31的情况。结果A、B组的MSCs在培养1周后均形成肌细胞形态,并且均表达α-肌动蛋白和cTnT;A组MSCs分化的肌样细胞所含的肌纤维较B组更丰实,细胞生长趋势也优于B组,并且可以表达CD31;B组MSCs分化的肌样细胞不表达CD31;对照组细胞仅表达α-肌动蛋白。结论心肌细胞裂解液是体外诱导MSCs分化为心肌样细胞的理想条件,优于传统的5-aza,在心肌细胞移植技术中可以用于体外模拟心肌细胞微环境。     

Acidic and basic fibroblast growth factors involved in cardiac angiogenesis following infarction

Acidic and basic fibroblast growth factors (FGF-1/FGF-2) promote angiogenesis in cancer. Angiogenesis is integral to cardiac repair following myocardial infarction (MI). The potential regulation of FGF-1/FGF-2 in cardiac angiogenesis postMI remains unexplored. Herein, we examined the temporal and spatial expression of FGF-1/FGF-2 and FGF receptors (FGFR) in the infarcted rat heart at days 1, 3, 7, and 14 postMI. FGF-1/-2 gene and protein expression, cells expressing FGF-1/-2 and FGFR expression were examined by quantitative in situ hybridization, RT-PCR; western blot, immunohistochemistry and quantitative in vitro autoradiography. Compared to the normal heart, we found that in the border zone and infarcted myocardium 1) FGF-1 gene expression was increased in the first week postMI and returned to control levels at week 2; FGF-1 protein levels were, however, largely reduced at day 1, then elevated at day 3 peaked at day 7 and declined at day 14; and cells expressing FGF-1 were primarily inflammatory cells; 2) FGF-2 gene expression was significantly elevated from day 1 to day 14; the increase in FGF-2 protein level was most evident at day 7 and cells expressing FGF-2 were primarily endothelial cells; 3) FGFR expression started to increase at day 3 and remained elevated thereafter; and 4) FGF-1/FGF-2 and FGFR expression remained unchanged in the noninfarcted myocardium. Thus, FGF-1/FGF-2 and FGFR expression are enhanced in the infarcted myocardium in the early stage after MI, which is spatially and temporally coincident with angiogenesis, suggesting that FGF-1/FGF-2 are involved in regulating cardiac angiogenesis and repair.     

Allogeneic mesenchymal stem cells restore cardiac function in chronic ischemic cardiomyopathy via trilineage differentiating capacity

The mechanism(s) underlying cardiac reparative effects of bone marrow-derived mesenchymal stem cells (MSC) remain highly controversial. Here we tested the hypothesis that MSCs regenerate chronically infarcted myocardium through mechanisms comprising long-term engraftment and trilineage differentiation. Twelve weeks after myocardial infarction, female swine received catheter-based transendocardial injections of either placebo (n = 4) or male allogeneic MSCs (200 million; n = 6). Animals underwent serial cardiac magnetic resonance imaging, and in vivo cell fate was determined by co-localization of Y-chromosome (Y^pos) cells with markers of cardiac, vascular muscle, and endothelial lineages. MSCs engrafted in infarct and border zones and differentiated into cardiomyocytes as ascertained by co-localization with GATA-4, Nkx2.5, and α-sarcomeric actin. In addition, Y^pos MSCs exhibited vascular smooth muscle and endothelial cell differentiation, contributing to large and small vessel formation. Infarct size was reduced from 19.3 ± 1.7% to 13.9 ± 2.0% (P < 0.001), and ejection fraction (EF) increased from 35.0 ± 1.7% to 41.3 ± 2.7% (P < 0.05) in MSC but not placebo pigs over 12 weeks. This was accompanied by increases in regional contractility and myocardial blood flow (MBF), particularly in the infarct border zone. Importantly, MSC engraftment correlated with functional recovery in contractility (R = 0.85, P < 0.05) and MBF (R = 0.76, P < 0.01). Together these findings demonstrate long-term MSC survival, engraftment, and trilineage differentiation following transplantation into chronically scarred myocardium. MSCs are an adult stem cell with the capacity for cardiomyogenesis and vasculogenesis which contribute, at least in part, to their ability to repair chronically scarred myocardium.     

FGF-1 enhanced cardiogenesis in differentiating embryonal carcinoma cell cultures,which was opposite to the effect of FGF-2

To investigate the effect of fibroblast growth factors (FGFs) on cellular differentiation, we employed a multipotent mouse embryonal carcinoma cell line, P19, which differentiates into cardiac muscle, skeletal muscle and neural cells in the presence of the appropriate concentrations of retinoic acid (RA). Under conditions appropriate for cardiac muscle differentiation, the expression of FGF-1 was significantly enhanced before any tissue-specific gene was induced. In contrast, up-regulation of the FGF-2 gene was observed with skeletal muscle-inducing concentrations of RA. Exogenous FGF-1, under skeletal muscle-inducing conditions, suppressed the expression of marker genes for skeletal muscle and induced cardiac alpha myosin heavy chain (alphaMHC) gene with up-regulation of bone morphogenetic protein-4 (BMP-4) and GATA-4. Unlike FGF-1, exogenous FGF-2 promoted skeletal muscle differentiation. These results indicate that FGF-1 and FGF-2 play different roles in P19 cell differentiation induced by RA.     

A strategy of retrograde injection of bone marrow mononuclear cells into the myocardium for the treatment of ischemic heart disease

OBJECTIVE: Bone marrow cells implantation (BMI) has been reported to efficiently improve ischemic heart disease. However, BMI strategies are generally invasive. To establish a BMI strategy for ischemic heart disease, we performed implantation of autologous cryopreserved mononuclear cells (MNCs) from bone marrow (BM) retrogradely into the myocardium via the coronary vein in pigs with acute myocardial infarction (AMI) and old myocardial infarction (OMI). METHODS: BM cells were harvested from the pigs' fumurs. MNCs were collected by centrifugation and were cryopreserved. Anterior myocardial infarction was induced by occlusion of the midportion of the left anterior descending coronary artery without surgical intervention. Frozen BM cells were quickly thawed and injected retrogradely via the coronary vein into the myocardium through a single balloon infusion catheter 6 h and 2 weeks after the induction of infarction. Four weeks after implantation, coronary arteriograms were obtained, cardiac function was analyzed with the use of a conductance catheter, and histopathologic analysis was performed with a confocal laser microscope. Plasma levels of natriuretic peptides and angiogenic growth factors were measured after BMI. RESULTS: Flow cytometric analysis revealed that 90% of cryopreserved BM cells were viable in vitro. Labeled BM cells were entirely distributed around in the infarcted area of maycardium in pigs. BMI increased collateral neovascuralization in infarcted hearts. BMI significantly improved cardiac function in AMI with BMI and OMI with BMI groups. BMI also increased the formation of microcapillary arteries in infarcted hearts. Levels of natriuretic peptides were significantly decreased, and levels of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF2) were significantly increased after BMI. Confocal laser microscopy revealed the presence of proliferative and activated myocardial cells in infarcted hearts after BMI. CONCLUSION: The retrograde infusion of cryopreserved BM cells into myocardium efficiently induced angiogenesis and improved cardiac function in pigs with AMI or OMI. These results suggest that the present strategy of BMI will be safe and feasible as an angiogenic cell therapy for ischemic heart disease.     

STAT3-dependent mouse embryonic stem cell differentiation into cardiomyocytes: analysis of molecular signaling and therapeutic efficacy of cardiomyocyte precommitted mES transplantation in a mouse model of myocardial infarction

Pluripotent embryonic stem (ES) cell therapy may be an attractive source for postinfarction myocardial repair and regeneration. However, the specific stimuli and signal pathways that may control ES cell-mediated cardiomyogenesis remains to be completely defined. The aim of the present study was to investigate (1) the effect and underlying signal transduction pathways of leukemia inhibitory factor (LIF) and bone-morphogenic protein-2 (BMP-2)-induced mouse ES cell (mES-D3 line) differentiation into cardiomyocytes (CMC) and (2) the efficacy of CMC precommitted mES cells for functional and anatomical cardiac repair in surgically-induced mouse acute myocardial infarction (AMI) model. Various doses of LIF and BMP-2 and their inhibitors or blocking antibodies were tested for mES differentiation to CMC in vitro. CMC differentiation was assessed by mRNA and protein expression of CMC-specific markers, Connexin-43, CTI, CTT, Mef2c, Tbx5, Nkx2.5, GATA-4, and alphaMHC. LIF and BMP-2 synergistically induced the expression of CMC markers as early as 2 to 4 days in culture. Signaling studies identified STAT3 and MAP kinase (ERK1/2) as specific signaling components of LIF+BMP-2-mediated CMC differentiation. Inhibition of either STAT3 or MAPK activation by specific inhibitors drastically suppressed LIF+BMP-2-mediated CMC differentiation. Moreover, in mouse AMI, transplantation of lentivirus-GFP-transduced, LIF+BMP-2 precommitted mES cells, improved post-MI left ventricular functions, and enhanced capillary density. Transplanted cells engrafted in myocardium and differentiated into CMC and endothelial cells. Our data suggest that LIF and BMP-2 may synergistically enhance CMC differentiation of transplanted stem cells. Thus augmentation of LIF/BMP-2 downstream signaling components or cell type specific precommitment may facilitate the effects of ES cell-based therapies for post-MI myocardial repair and regeneration.     

Magnetic resonance evaluation of transplanted mesenchymal stem cells after myocardial infarction in swine

Objectives To trace and evaluate intracoronary transplanted mesenchymal stem cells(MSCs) labeled with superparamagnetic iron oxide(SPIO) by using magnetic resonance imaging(MRI) in a swine model of myocardial infarction (MI).Methods MSCs were transfected with a lentiviral vector carrying the gene encoding green fluorescent protein (GFP) and labeled in vitro with SPIO.Two weeks after MI, swine were randomized to intracoronary transplantation of dual -labeled MSCs(n = 10),MSCs-GFP(n = 10) and saline(n = 5).MRI examination was performed with a 1.5T clinical scanner at 24 hours,3 weeks and 8 weeks after cells transplantation. Signal intensity(SI) changes,cardiac function and MI size were measured using MRI.Correlation between MR findings and histomorphologic findings was also investigated. Results The labeling efficiency at a combination of 25μg Fe/ml SPIO and 0.8 pi/ml Lipofectamine 2000 reached 100%.SPIO labeling did not affect GFP fluorescence and dual-labeling did not affect cell proliferation(P>0.05). Multipotentiality was not affected especially for cardiomyocyte-like cells differentiation.Cardiac cell marker of a-MHC and actinin were positively expressed by immunofluorescence staining after induction.SI on T2 * WI decreased substantial- ly in the interventricular septum 24 hours after injection of MSCs.The intensity of hypo-intense signals appeared to increase throughout the later time points.Changes in SI at 24 hours,3 weeks and 8 weeks were 52.98%±10.74%,21.53%±5.40%and 6.23%±2.01%,respectively(P<0.01).DE-MRI demonstrated both dual-labeled MSCSs and MSCs-GFP could dramatically reduce the size of MI and improve cardiac function. Histological data revealed that prussian blue stain-positive cells were found mainly in the border zone which also showed green fluorescence but negative for macrophage marker(CD68).Gross pathologic examination revealed that engrafted MSCs dramatically reduce the extent of necrotic myocardium and promote the regeneration of new,contractile myocardium along the subendocardia     

Repeated implantation is a more effective cell delivery method in skeletal myoblast transplantation for rat myocardial infarction.

BACKGROUND: Several clinical trials are underway to determine whether autologous skeletal myoblast transplantation is an effective and safe therapeutic strategy for severe heart failure due to myocardial infarction (MI). It remains unclear whether repeated skeletal myoblast implantation is a feasible and effective cell delivery method for the infarcted myocardium. METHODS AND RESULTS: Four weeks after a coronary ligation, male syngeneic Lewis rats were assigned to 3 treatment groups: 3 episodes of skeletal myoblasts (6x10(6)) transplantation (group I), a bolus transplantation of myoblasts (18x10(6)) (group II), or culture medium injection (group III). Eight weeks after the first treatment, echocardiography, cardiac catheterization and histological examination were performed to compare the therapeutic effects on left ventricular (LV) systolic and diastolic functions, and the engrafted myoblast volume. Repeated myoblast implantation significantly improved LV function and resulted in significantly larger engrafted volume and LV contractility compared with a bolus transplantation with the same number of myoblasts. CONCLUSIONS: Repeated skeletal myoblast transplantation is a safe and effective therapeutic strategy for the infarcted myocardium.     

自体骨髓间叶干细胞诱导分化移植治疗房室阻滞的初步观察

利用诱导分化的骨髓间叶干细胞自体移植治疗房室阻滞,探讨生物介入方法治疗缓慢型心律失常的新途径。11只实验犬随机分为实验组(n=6)和对照组 (n=5)。应用射频技术消融His束,制备永久Ⅲ度房室阻滞动物模型;每只犬抽取 10ml犬骨髓液,应用密度梯度离心法及贴壁培养法分离、培养和扩增骨髓间叶干细胞, 5 氮胞苷对骨髓间叶干细胞进行诱导分化;房室阻滞 4周后,开胸心脏直视下将BrdU标记的分化干细胞 (1ml, 1. 5×107细胞)多点注射至该犬消融的His束部位,而对照组仅将 1mlDMEM培养液替代干细胞悬液多点注射至相同部位。术后 1~12周,应用心电图观察两组活体动物房室功能恢复情况,应用组织病理、免疫组化等技术对移植干细胞的存活、增殖、分化与缝隙连接功能进行评价。结果:在动物房室阻滞模型中,实验组犬在自体骨髓干细胞移植后 12周, 2 /6只犬的房室传导功能得以改善;病理与免疫组化示诱导分化的骨髓干细胞在His束区存活、增殖和分化为心肌细胞、血管内皮细胞,并与宿主细胞建立缝隙连接;而对照组 5只犬未见上述变化。结论:自体移植诱导分化的骨髓间叶干细胞有可能改善His束传导功能。