PI3-K/Akt信号通路对骨髓源性心肌干细胞分化的调控作用

目的研究磷脂酰肌醇-3激酶/丝氨酸/苏氨酸蛋白激酶(PI3-K/Akt)信号通路在骨形态发生蛋白-2(BMP-2)诱导骨髓源性心肌干细胞(MCSCs)向心肌细胞分化中的调控作用,探讨MCSCs向心肌细胞分化的信号转导机制。方法利用单克隆培养技术从SD大鼠骨髓中筛选MCSCs,用BMP-2诱导其向心肌细胞定向分化,通过免疫细胞化学标记和Western blotting检测BMP-2诱导后细胞内p-Akt水平的变化,并通过RT-PCR检测心肌早期转录因子和心肌特异基因的表达。结果BMP-2诱导前MCSCs内p-Akt水平较低,诱导后渐增强,20~30min达高峰,1h后逐渐降低。用PI3-K抑制剂Ly294002预处理细胞后,p-Akt水平明显降低。RT-PCR检测显示,诱导前MCSCs的Nkx2.5和GATA-4呈低表达,诱导后2周表达增强,4周表达更加明显。cTnT和Cx-43 mRNA在诱导前未见表达,诱导后2周表达明显,4周表达增强。用Ly294002处理后,细胞的Nkx2.5、GATA-4和cTnT、Cx-43 mRNA的表达显著降低,细胞形态变化不明显。结论BMP-2能诱导MCSCs向心肌细胞分化,PI3-K/Akt信号通路在BMP-2诱导MCSCs向心肌细胞分化中发挥重要的调控作用。     

Smad信号通路在骨髓源性心肌干细胞向心肌分化中的作用

目的研究Smad信号通路在BMP-2诱导的骨髓源性心肌干细胞（MCSCs）向心肌分化中的作用,探讨MCSCs向心肌分化的信号转导机制。方法从SD大鼠骨髓中筛选MCSCs,用骨形态发生蛋白-2（BMP-2）诱导向心肌定向分化。Western blotting和免疫细胞化学法检测诱导后细胞内磷酸化的Smadl／5／8的表达及其随诱导时间在细胞内分布的变化。RT-PCR检测诱导前后细胞内GATA-4和心肌特异性肌钙蛋白T（cTnT）mRNA的表达。结果BMP-2诱导后15min,细胞内可检测到磷酸化的Smadl／5／8的表达,30min-1h表达明显增加,1h后开始降低,4h呈低表达。BMP-2诱导后15min,磷酸化的Smadl／5／8仅见于胞质中,30min胞质和胞核均见表达,1h主要在胞核内表达。BMP-2诱导后2周,细胞明显表达GATA-4和cTnT mRNA。诱导后4周细胞呈现成熟心肌细胞样形态。用SB203580抑制Smad信号后,GATA-4和cTnTmRNA的表达显著降低,细胞形态变化不明显。结论Smad信号通路在BMP-2诱导MCSCs向心肌分化中发挥重要的介导作用。     

骨形态发生蛋白-2在骨髓源性心肌干细胞向心肌分化中的作用

目的研究骨形态发生蛋白-2（BMP-2）对骨髓源性心肌干细胞（MCSC）向心肌分化的作用,探讨MCSC向心肌分化中的BMP-2信号转导机制.方法从SD大鼠骨髓中筛选MCSC,用BMP-2诱导向心肌定向分化.RT-PCR检测诱导前后BMP-2受体BMPRIA和BMPRII、心肌早期转录因子Nkx2.5和GATA-4以及cTnT mRNA的表达.免疫细胞化学标记诱导后细胞cTnT和Cx-43的表达.结果用BMP-2诱导后,MCSC的形态和排列发生变化.RT-PCR检测结果显示,诱导前BMPRIA和BMPRII以及Nkx2.5和GATA-4呈低表达,诱导后1周表达增加,3～4周表达明显.cTnT mRNA在诱导前不表达,诱导后1周开始表达,3～4周表达明显.免疫细胞化学染色显示,cTnT和Cx-43从诱导后2周开始表达.3～4周cTnT表达增强,呈现密集的横纹样结构.Cx-43在2周位于细胞膜下,3周分布于相邻细胞连接处,4周呈颗粒状密集分布于肌管的相邻细胞连接处. 结论BMP-2通过BMPRIA和BMPRII的介导作用诱导MCSC分化为心肌细胞.     

骨形态发生蛋白-2在小鼠胚胎心流出道发育中的作用

目的 探讨骨形态发生蛋白-2(BMP-2)在小鼠胚胎心流出道发育过程中的作用。 方法 对胚龄9d(E9) ～E15（各胚龄取3～7只）小鼠心连续石蜡切片,用抗α-横纹肌肌动蛋白(α-SCA)抗体、抗胰岛素增强子结合蛋白(ISL-1)抗体、抗增殖细胞核抗原(PCNA)抗体、抗BMP-2抗体进行免疫组织化学染色。结果 E9,流出道心胶质内无细胞,心肌增殖活性低,BMP-2弱表达于流出道心肌、心内膜及心包腔背侧壁。E9～11,流出道增长,心包腔背侧壁ISL-1阳性细胞至流出道远端分化为心肌细胞后增殖逐渐减弱。E10～11,流出道嵴内间充质细胞逐渐增加,可见BMP-2、PCNA阳性细胞;流出道BMP-2表达逐渐增强达高峰,向两端延伸逐渐减弱,动脉端可及心包反折处。E12,流出道缩短,BMP-2表达减弱。E13～15,流出道隔逐渐肌化,BMP-2在心脏近大血管部心肌呈较弱表达。E10～13,流出道远段心肌呈低增殖活性,近段及右心室心肌增殖成小梁致右心室形成及扩大。结论 BMP-2诱导第二生心区(SHF)细胞分化为心肌细胞添加至心动脉端,参与心流出道嵴的发育。BMP-2抑制流出道心肌增殖,流出道近段BMP 2表达减弱重启了心肌细胞增殖,致右心室形成及流出道缩短。低水平的BMP 2可能诱导流出道隔间充质细胞向心肌分化。     

骨形态蛋白2体外诱导大鼠骨髓间充质干细胞分化为心肌样细胞

目的 应用骨形态蛋白2(BMP-2)体外诱导骨髓间充质干细胞(MSCs)向心肌样细胞分化,探索MSCs向心肌细胞分化的诱导方法.方法 取SD大鼠四肢骨骨髓,分离培养MSCs,应用BMP-2定向诱导,相差显微镜观察细胞形态学变化,应用免疫细胞化学、激光扫描共焦显微镜技术检测结蛋白(desmin)、α-横纹肌肌动蛋白(α-sareomeric actin)、心肌特异性肌钙蛋白(C-TnT)的表达,透射电镜鉴定.在诱导后7d、21d和28d 3个时间点以半定量RT-PCR方法检测细胞心肌早期转录因子(GATA4)和心肌特异性α-肌凝蛋白重链(α-MHC)的表达.结果 BMP-2诱导后的MSCs细胞伸出伪足,排列方向渐趋一致.MSCs体外经BMP-2诱导后分化的细胞结蛋白、α-横纹肌肌动蛋白、C-TnT均表达阳性,结蛋白、α-横级肌肌动蛋白阳性率较高,分别为37.28%和63.94%,而C-TnT阳性率较低为34.66%.透射电镜下可见到平行排列的肌丝,大量的粗面内质网和线粒体,富含糖原和核糖体.RT-PCR结果显示,GATA4于诱导后7d弱表达,21d表达增强,28d表达减弱.α-MHC在诱导后7d不表达,21d弱表达,28d表达明显.结论骨髓间充质干细胞在BMP-2诱导下可定向分化为心肌样细胞,是自体心肌细胞的一种良好供体来源.     

BMP-4在视网膜与视神经中的分布及对少突胶质前体细胞分化的影响

目的:研究骨形态发生蛋白4(bone morphogenetic protein4,BMP-4)在视网膜与视神经上的表达情况及其对少突胶质前体细胞(oligodendrocyte precursor cells,OPCs)分化的影响,进一步探讨视神经乳头处无髓鞘形成的原因。方法:取生后7d SD大鼠视神经,用免疫组织化学方法研究BMP-4的表达情况。采用恒温振荡法和差速贴壁法分离纯化新生SD大鼠OPCs。用BMP-4诱导OPCs分化,通过免疫细胞化学方法研究OPCs的分化方向。通过Western Blot方法研究BMP-4浓度与OPCs细胞体系内Olig2蛋白表达水平之间的相互关系。结果:(1)在发育过程中,BMP-4仅选择性表达在视神经乳头处;(2)成功纯化的OPCs在PDGF和bFGF撤除后自发分化为少突胶质细胞;(3)OPCs经BMP-4诱导后向II型星形胶质细胞分化;(4)OPCs内Olig2蛋白的表达量随着BMP-4浓度的逐渐增高而逐渐降低。结论:在视神经乳头表达的BMP-4蛋白有可能作用于迁移至此处的OPCs,通过激活相关信号途径以下调OPCs内Olig2蛋白的表达水平,抑制OPCs向少突胶质细胞方向分化,从而抑制视神经乳头髓鞘形成。     

miR-25-3p下调ADAM10表达阻断Notch信号通路抑制P19细胞向心肌细胞分化

目的探讨miR-25-3p靶向解整合素金属蛋白酶10(ADAM10)调控Notch信号通路对P19细胞向心肌细胞分化的影响。方法采用二甲基亚砜(DMSO)诱导P19细胞向心肌细胞分化,分别收集诱导分化第0、 5、 10天的细胞,实时荧光定量PCR检测诱导分化过程中心肌分化标志物GATA结合蛋白4 (GATA4)、心肌肌钙蛋白T(cTnT)、心房利钠尿多肽(ANP)的mRNA以及miR-25-3p水平, Western blot法检测诱导分化过程中ADAM10蛋白水平。通过逆转录病毒感染P19细胞过表达miR-25-3p,采用实时荧光定量PCR检测感染后P19细胞中miR-25-3p水平, Western blot法检测感染后P19细胞ADAM10蛋白水平。生物信息学软件预测并通过荧光素酶报告实验验证miR-25-3p与ADAM10之间的靶向结合作用。感染后的P19细胞经DMSO诱导分化10 d后,免疫荧光实验检测细胞中心肌肌钙蛋白I(cTnI)蛋白的表达情况,并计算心肌细胞分化率; Western blot法检测GATA4、 cTnT、 ANP以及Notch信号通路相关蛋白Notch1、 Hes家族bHLH转录因子1(Hes1)、 Hairy相关转录因子1(Hey1)和Hey2蛋白水平。结果 P19细胞向心肌细胞诱导分化的第0、 5、 10天过程中, GATA4、 cTnT、 ANP的mRNA水平及ADAM10蛋白水平均逐渐增加,而miR-25-3p水平逐渐降低;逆转录病毒感染后, P19细胞中miR-25-3p水平显著增加,而ADAM10蛋白水平显著降低;生物信息学分析证实ADAM10为miR-25-3p的靶基因;诱导分化10 d后,过表达miR-25-3p可显著降低心肌细胞分化率,下调GATA4、 cTnT、 ANP及Notch信号通路相关分子Notch1、 Hes1、 Hey1和Hey2的蛋白水平。结论miR-25-3p可显著抑制P19细胞向心肌细胞分化,其机制可能与其靶向抑制ADAM10表达,进而抑制Notch信号通路的激活有关。     

淫羊藿素通过雌激素受体和骨形态发生蛋白信号诱导MC3T3-E1 subclone 14细胞分化

目的: 观察淫羊藿素(ICT)对MC3T3-E1 subclone 14前体成骨细胞株增殖、分化的影响,以及雌激素受体(ER)和骨形态发生蛋白(BMP)信号在分化中的作用。方法: WST-8、BrdU法检测ICT对MC3T3-E1 subclone 14细胞活力和增殖的影响;ICI182780阻断ER受体信号后,检测ICT和noggin对MC3T3-E1 subclone 14细胞碱性磷酸酶(ALP)活性、I型胶原(Col I)和骨钙素(BGP)的影响;实时荧光PCR检测ICT对BMP-2、4、7 mRNA表达的影响;Western blotting检测ER受体信号阻断后,ICT对Smad1/5/8蛋白磷酸化的影响。结果: ICT(0.1 μmol/L、1 μmol/L)可以提高MC3T3-E1 subclone 14细胞ALP、Col I、BGP和矿化结节数量(P<0.01或P<0.05),表明ICT有促分化的作用,但对细胞活力和增殖指数无明显影响;阻断ER受体信号后,ICT促分化作用明显下降(P<0.01);ICT可以提高BMP-2、4 mRNA的表达(P<0.01),但对BMP-7 mRNA无作用(P>0.01);阻断ER信号后,ICT 促Smad1/5/8磷酸化明显减弱(P<0.01)。进一步阻断BMP/Smad信号可以抑制ICT促分化的作用(P<0.01)。结论: ICT可以通过ER受体激活BMP/Smad信号通路,进而促进MC3T3-E1 subclone 14细胞的分化。     

PGE2和NF-кB信号途径在骨再生中的相互作用

目的 本研究旨在利用MC3T3-E1成骨细胞株与大鼠骨折模型来研究骨折愈合过程中PGE2和NF-кB信号途径的相互作用.方法 利用PGE2与NF-кB抑制剂BAY 11-7082处理MC3T3-E1成骨细胞和大鼠骨折模型,采用碱性磷酸酶活性测定、Western blot分析、EMSA分析以及ELISA测定等研究手段,研究PGE2、NF-кB、BMP-7、Id2以及SOD2在骨再生中的作用.结果 利用10 μmol/l PGE2处理MC3T3-E1细胞10 min,30 min和2h后,能够显著地促进成骨细胞增殖与分化,当细胞用5μmol/L BAY 11-7082处理后,PGE2诱导作用受到抑制,表明PGE2增加ALP的表达是通过NF-kB途径来介导.局部注射NF-kB抑制剂后PGE2的生物合成明显减少;此外,抑制骨折部位ALP的活性,在骨折的损伤修复过程中,NF-кB、BMP-7以及SOD2的表达均明显上升,而Id2的表达明显下降；加入NF-кB活性抑制剂后,BMP-7与Id2的表达恢复到正常水平,而SOD2的表达没有改变. 结论 PGE2能够同时通过抑制Id2细胞因子和激活NF-кB信号途径诱导成骨细胞分化.     

BMP-2和EGF对神经干细胞向神经元分化及Notch信号分子表达的影响

采用BMP-2(bonemorphogeneticprotein2)和EGF(epidemicgrowthfactor)诱导体外培养的神经干细胞分化,通过免疫荧光染色以及细胞计数方法,观察其分化为神经元的情况;用RTPCR和Westernblot检测Notch信号分子Notch1、PS1、RBPJk和HES1的表达水平。结果表明:BMP2组分化为神经元的比例明显高于对照(control,Ctrl)组和EGF组;EGF组分化为神经元的比例与Ctrl组相比无显著差别;与Ctrl组相比,BMP-2组和EGF组中Notch通路4种信号分子的mRNA表达量均无显著差异;PS1蛋白表达量也无明显差异。结果提示,BMP-2对神经干细胞分化为神经元的诱导作用强于EGF和自主分化,其分化为神经元的比例增加与Notch信号分子的表达水平无关。     

Involvement of p38MAPK/NF-κB Signaling Pathways in Osteoblasts Differentiation in Response to Mechanical Stretch

Bone morphogenetic proteins (BMPs) are known to be important in osteoblasts' response to mechanical stimuli. BMPs/Smad signaling pathway has been demonstrated to play a regulatory role in the mechanical signal transduction in osteoblasts. However, little is currently known about the Smad independent pathway in osteoblasts differentiation in mechanical loading. In this study, MC3T3-E1 cells were subjected to mechanical stretch of 2000?micro-stain (με) at 0.5?Hz, in order to investigate the involvement of p38MAPK and NF-κB signaling pathways in mechanical response in osteoblasts. We found BMP-2/BMP-4 were up-regulated by mechanical stretch via the earlier activation of p38MAPK and NF-κB signaling pathways, which enhanced osteogenic gene expressions including alkaline phosphatase (ALP), collagen type I (Col I) and osteocalcin (OCN), and the expressions of these osteogenic genes were remarkably decreased with Noggin (an inhibitor for BMPs signals) pretreatment. Furthermore, BMP-2/BMP-4 expressions were suppressed by PDTC, an inhibitor of NF-κB pathway and SB203580, an inhibitor of p38MAPK pathway, respectively, leading to the declined levels of ALP, Col I and OCN. Interestingly, blocking in p38MAPK pathway can also cause the inactivation of NF-κB pathway in mechanical stretch. Collectively, the results indicate during mechanical stretch p38MAPK and NF-κB signaling pathways are activated first, and then up-regulate BMP-2/BMP-4 to enhance osteogenic gene expressions. Moreover, p38MAPK and NF-κB signals have cross-talk in regulation of BMP-2/BMP-4 in mechanical response.     

BMP-9 induced osteogenic differentiation of mesenchymal stem cells: molecular mechanism and therapeutic potential

Promoting osteogenic differentiation and efficacious bone regeneration have the potential to revolutionize the treatment of orthopaedic and musculoskeletal disorders. Mesenchymal Stem Cells (MSCs) are bone marrow progenitor cells that have the capacity to differentiate along osteogenic, chondrogenic, myogenic, and adipogenic lineages. Differentiation along these lineages is a tightly controlled process that is in part regulated by the Bone Morphogenetic Proteins (BMPs). BMPs 2 and 7 have been approved for clinical use because their osteoinductive properties act as an adjunctive treatment to surgeries where bone healing is compromised. BMP-9 is one of the least studied BMPs, and recent in vitro and in vivo studies have identified BMP-9 as a potent inducer of osteogenic differentiation in MSCs. BMP-9 exhibits significant molecular cross-talk with the Wnt/ β-catenin and other signaling pathways, and adenoviral expression of BMP-9 in MSCs increases the expression of osteogenic markers and induces trabecular bone and osteiod matrix formation. Furthermore, BMP-9 has been shown to act synergistically in bone formation with other signaling pathways, including Wnt/ β-catenin, IGF, and retinoid signaling pathways. These results suggest that BMP-9 should be explored as an effective bone regeneration agent, especially in combination with adjuvant therapies, for clinical applications such as large segmental bony defects, non-union fractures, and/or spinal fusions.     

A comprehensive analysis of the dual roles of BMPs in regulating adipogenic and osteogenic differentiation of mesenchymal progenitor cells

Pluripotent mesenchymal stem cells (MSCs) are bone marrow stromal progenitor cells that can differentiate into osteogenic, chondrogenic, adipogenic, and myogenic lineages. Several signaling pathways have been shown to regulate the lineage commitment and terminal differentiation of MSCs. Here, we conducted a comprehensive analysis of the 14 types of bone morphogenetic protein (BMPs) for their abilities to regulate multilineage specific differentiation of MSCs. We found that most BMPs exhibited distinct abilities to regulate the expression of Runx2, Sox9, MyoD, and PPARgamma2. Further analysis indicated that BMP-2, BMP-4, BMP-6, BMP-7, and BMP-9 effectively induced both adipogenic and osteogenic differentiation in vitro and in vivo. BMP-induced commitment to osteogenic or adipogenic lineage was shown to be mutually exclusive. Overexpression of Runx2 enhanced BMP-induced osteogenic differentiation, whereas knockdown of Runx2 expression diminished BMP-induced bone formation with a decrease in adipocyte accumulation in vivo. Interestingly, overexpression of PPARgamma2 not only promoted adipogenic differentiation, but also enhanced osteogenic differentiation upon BMP-2, BMP-6, and BMP-9 stimulation. Conversely, MSCs with PPARgamma2 knockdown or mouse embryonic fibroblasts derived from PPARgamma2(-/-) mice exhibited a marked decrease in adipogenic differentiation, coupled with reduced osteogenic differentiation and diminished mineralization upon BMP-9 stimulation, suggesting that PPARgamma2 may play a role in BMP-induced osteogenic and adipogenic differentiation. Thus, it is important to understand the molecular mechanism behind BMP-regulated lineage divergence during MSC differentiation, as this knowledge could help us to understand the pathogenesis of skeletal diseases and may lead to the development of strategies for regenerative medicine.     

Osteogenic response of human adipose-derived stem cells to BMP-6, VEGF,and combined VEGF plus BMP-6 in vitro

Exogenous addition of three factors—mesenchymal stem cells (MSCs), vascular endothelial growth factor (VEGF), and bone morphogenetic proteins (BMPs)—has proven to be more beneficial than delivery of any single factor for fracture repair in animal models. We studied the osteogenic differentiation of human adipose-derived stem cells (hADSCs) in the presence of VEGF, BMP-6, or VEGF plus BMP-6 to better understand their enhancement of osteoblastic differentiation of MSCs. The VEGF plus BMP-6 group demonstrated an additive effect on the enhancement of mineralization and expression of ALP and Msx2 genes. Unlike VEGF or BMP-6 alone, the combination of VEGF and BMP-6 significantly enhanced the expression of COL1A1, osterix, and Dlx5 genes. The data indicate that a cross-talk between VEGF and BMP-6 signaling pathways enhances osteogenic differentiation of hADSCs.     

激活素A和骨形成蛋白-4诱导人羊膜上皮细胞转分化为心肌样细胞的实验研究

近年来羊膜上皮细胞(AECs)被认为是心肌细胞移植较好的种子细胞之一。研究表明,激活素A(ActivinA)和骨形成蛋白-4(BMP-4)能够诱导人胚胎干细胞向心肌细胞分化。本研究通过体外分离、培养并鉴定人AEC后,采用Activin A和BMP-4作为诱导剂,观察它们能否诱导AEC向心肌样细胞转分化。应用定量RT-PCR、Western blot、免疫细胞化学等方法来检测基因及蛋白表达变化。结果显示,人AEC能够表达上皮细胞特异性蛋白角蛋白19(CK19)。经Activin A和BMP-4共同诱导培养14d后,AEC心肌特异性转录因子Nkx2.5和特异性结构蛋白α-actinin的mRNA表达水平明显升高,同时α-actinin的蛋白表达水平亦明显增加。本实验提示,ActivinA和BMP-4在体外能够诱导人AEC向心肌样细胞转分化,同时该诱导方法可能成为诱导AEC向心肌样细胞转分化的一个新方法。     

Migration of Resident Cardiac Stem Cells in Myocardial Infarction

Ischemic heart disease is a major cause of morbidity and mortality worldwide. Stem cell‐based therapy, which aims to restore cardiac structure and function by regeneration of functional myocardium, has recently been proposed as a novel alternative treatment modality. Resident cardiac stem cells (CSCs) in adult hearts are a key cell type under investigation. CSCs have been shown to be able to repair damaged myocardium and improve myocardial function in both human and animal studies. This approach relies not only on the proliferation of the CSCs, but also upon their migration to the site of injury within the heart. Here, we briefly review reported CSC populations and discuss signaling factors and pathways required for the migration of CSCs. Anat Rec, 2013. © 2012 Wiley Periodicals, Inc.