Differentiation and Diversification of Vascular Cells from Embryonic Stem Cells

Experimental models that allow the evaluation of the full potential of stem cells under normal physiological conditions and in the absence of genetic or injury-induced dysfunction would serve as valuable tools for the study of the mechanisms underlying stem cell differentiation. Ideally, such a model would also permit the robust formation of donor-derived tissue-specific cells. Because studies have shown that the differentiation of stem cells into cells of a different germinal layer is highly inefficient in the absence of selective pressure, it is very unlikely that a healthy adult animal can fulfill these requirements. In this review, we describe the advantages of the permissive aspects of the developing preimmune fetus in the early gestational age that led us to develop the sheep as a large-animal model of human stem cell plasticity.     

Petrous Apex Cholesteatoma

Primary or secondary petrous apex cholesteatoma requires surgical management. We describe here five patients with cholesteatoma in the petrous apex on whom different surgical approaches to this region were used. Translabyrinthine-transcochlear (transotic) approach with VII-XII anastomosis was used in four patients. In one patient middle fossa approach with otic capsule and facial canal leaving intact was used. All patients are without recurrence of cholesteatoma with improving of the facial nerve function in one case. We discuss specific pathologies of the petrous apex, the surgical approach to this region indicated according to the size and type of pathology diagnosed, hearing loss and facial nerve function. Possible complications of this surgical procedure and their management are also discussed.     

乙型肝炎病毒X基因对肾小管上皮细胞间质转分化的影响

目的 探讨乙型肝炎病毒(HBV)X基因表达蛋白HBX对体外培养的人近端肾小管上皮细胞株(HK-2)细胞形态及转分化的影响.方法 用分子克隆的方法构建pcDNA3.1-myc-HBX质粒,采用脂质体转染法瞬时转染HK-2细胞,Q-PCR及Western印迹法验证HBX在HK-2细胞中的表达.以未转染质粒和转染空载质粒pcDNA3.1-myc作为对照.用显微镜观察转染pcDNA3.1-myc-HBX质粒后HK-2细胞形态,用Western印迹及Q-PCR法检测细胞转分化标志蛋白α平滑肌肌动蛋白(α-SMA)、E钙黏蛋白(E-cadherin)的表达;ELISA检测细胞上清液中白细胞介素(IL)-1、IL-6和肿瘤坏死因子α(TNF-α)的表达.结果 转染HBX后的HK-2细胞中存在HBX的高表达,证实转染成功.转染pcDNA3.1-myc-HBX质粒的HK-2细胞数量明显下降,细胞形态不规则,细胞状态受损;转染pcDNA3.1-myc-HBX质粒的HK-2细胞可上调E-cadherin及α-SMA表达;细胞上清液中高表达IL-1、IL-6和TNF-α(P＜ 0.01).结论 HBX质粒转染HK-2细胞后可引起细胞数目和形态的变化,并促进肾小管上皮细胞发生上皮间质转分化,肾小管上皮细胞周围炎性微环境的改变可能是其发生上皮间质转分化的原因之一.     

Insulin-producing cells derived from human pancreatic non-endocrine cell cultures reverse streptozotocin-induced hyperglycaemia in mice

Aims/hypothesis The aim of the study was to investigate the potential of human pancreatic non-endocrine cells to transdifferentiate into endocrine cells that would be capable of secreting insulin in response to glucose and ameliorating insulin-deficient diabetes after transplantation.Materials and methods Cell fractions enriched with exocrine cells after human islet isolation were treated with streptozotocin to remove residual beta cells, grown in monolayer culture to allow de-differentiation, transferred to cluster culture for redifferentiation in the presence of activin A, betacellulin, nicotinamide and glucose, supplemented with 10% FCS, and administered to streptozotocin-induced diabetic SCID mice. A subset of cells was transfected with the IPF1 gene (also known as PDX1) before transdifferentiation.Results No insulin was detectable in cell preparations after 5 days of treatment with streptozotocin. In monolayer culture, 90% of the streptozotocin-treated pancreatic cells co-expressed cytokeratin-19 and vimentin at 2 weeks and 60% expressed nestin at 4 weeks. Cell cultures with a high proportion of nestin-expressing cells had greater plasticity for transdifferentiation into cells with phenotypic and functional markers of beta cells, this property being significantly enhanced by transfection with IPF1 gene and leading to 15±6.7% insulin-positive cells after transplantation vs. 0.01% of cells transplanted after streptozotocin treatment alone. These cells improved glucose control in all of 42 diabetic mice after transplantation, restoring normoglycaemia in 40%.Conclusions/interpretation Human pancreatic cells are a potential source of new glucose-responsive insulin-producing cells that may be developed further for clinical use.     

Skeletal muscle stem cells do not transdifferentiate into cardiomyocytes after cardiac grafting

Skeletal muscle cell-derived grafts in the heart may benefit myocardial performance after infarction. Several studies have suggested that skeletal muscle stem cells (satellite cells) from adult muscle undergo transdifferentiation into cardiomyocytes after grafting into the heart, but expression of cardiac markers in graft cells has not been rigorously confirmed. To determine the fate of satellite cell-derived grafts in the heart, adult rat satellite cells were tagged in vitro with bromodeoxyuridine (BrdU) and grafted into normal hearts of syngeneic rats. At 4 and 12 weeks the graft cells formed multinucleated, cross-striated myofibers that expressed fast skeletal myosin heavy chain (MHC), thus indicating a mature skeletal muscle phenotype. Double staining for the BrdU tag and cardiac-specific markers was employed to identify transdifferentiation. Aside from four questionable cells, none of the 11 grafts examined expressed alpha-MHC, cardiac troponin I, or atrial natriuretic peptide. At 4 weeks, grafts expressed beta -MHC, a hallmark of slow twitch myofibers. By 12 weeks, however, the myofibers had atrophied and downregulated beta-MHC. Grafts never expressed the intercalated disk proteins N-cadherin or connexin43, hence electromechanical coupling did not occur. In conclusion, satellite cells differentiate into mature skeletal muscle and do not express cardiac-specific genes after grafting into the heart. Thus, transdifferentiation into cardiomyocytes did not occur.     

人脂肪干细胞分离培养鉴定及多向分化潜能的实验研究

目的探讨在不同诱导条件下人脂肪干细胞（ADSC）的体外多向分化情况。方法取人脂肪组织，用酶消化法分离、培养ADSC，用免疫细胞化学法鉴定ADSC。体外培养并测定第二、五、七代细胞增殖速率，绘制细胞生长曲线，计算群体倍增时间。流式细胞仪检测抗原CD44、CD49d、CD34，分析酶消化法获得的细胞分别向表皮细胞、成骨细胞、脂肪细胞定向诱导的能力，明确其分化能力。结果第二、五、七代细胞生长稳定，群体倍增时间约60h。10代以内的脂肪干细胞随着传代次数的增加其增殖能力未现明显降低的趋势。免疫细胞化学显示，干细胞相关抗原CD44、CD49d为阳性。但与造血系统相关抗原CD34阴性。成表皮诱导组示：免疫组织化学鉴定结构显示有CK19的表达。成骨诱导组示：细胞碱性磷酸酶染色阳性。成脂肪细胞诱导组示：油红0染色胞质内脂滴均被染成红色，证实为脂性液体。结论脂肪干细胞体外增殖能力强，来源充足，细胞获得方便，又避免了伦理问题且具有向其他多种细胞分化的潜能，可能成为理想的组织工程种子细胞。     

核因子κB反义寡核苷酸对转化生长因子β1诱导人肾小管上皮细胞转分化的影响

目的 探讨在转化生长因子β1（TGF-β1）诱导下，核因子κB（NF-κB）反义寡核苷酸对体外培养的人肾小管上皮细胞（HK-2）转分化的影响。 方法 采用脂质体介导的方法将NF-κB反义寡核苷酸（AS-ODN）导入细胞，以TGF-β1（10 μg/L）刺激HK-2细胞24 h后，用RT-PCR方法检测细胞中NF-κB mRNA及α平滑肌肌动蛋白（α-SMA）mRNA表达，用荧光光谱法分析α-SMA蛋白的表达，并以倒置相差显微镜观察细胞转分化过程的形态变化。 结果 TGF-β1诱导24 h后，HK-2细胞中NF-κB mRNA的表达显著上调，为空白对照组的8倍以上（P < 0.01）。NF-κB反义寡核苷酸导入细胞后，可显著抑制TGF-β1诱导的HK-2细胞的 NF-κB mRNA表达，比TGF-β1组减少75％（P < 0.05），同时，α-SMA mRNA和蛋白表达亦较TGF-β1组均明显下调（P < 0.05）。 结论 NF-κB反义寡核苷酸可抑制TGF-β1诱导肾小管上皮细胞NF-κB的表达，抑制肾小管上皮细胞转分化，可能有利于肾间质纤维化的防治。