大鼠视网膜干细胞与神经干细胞体外增殖、分化特点比较

目的 通过对大鼠视网膜干细胞和神经干细胞体外增殖、分化特点进行比较,进一步明确视网膜于细胞自我更新及向神经细胞方向分化的能力.方法 实验研究.分离出生10 d大鼠睫状体区组织及新生大鼠脑组织,分别应用酶消化法将两种组织制成单细胞悬液,放入含有20 μg/L碱性成纤维细胞生长因子、20μg/L表皮生长因子及1×B27添加剂的无血清DMEM/F12培养液中培养,观察并比较视网膜干细胞及神经干细胞体外增殖的特点.分别取第2代细胞,应用免疫细胞化学染色法检测干细胞特异性抗原神经巢蛋白（nestin）及细胞分裂增殖标志物5-溴脱氧尿核苷（BrdU）的表达.同时,应用含50 ml/L的胎牛血清及1×N2添加剂的培养基促进其分化,观察两种细胞向神经细胞方向分化的特点：分别应用免疫细胞化学染色法对分化后的细胞nestin、神经无标志物神经元特异性烯醇酶（NSE）、神经胶质细胞标志物神经胶质酸性蛋白（GFAP）进行检测,并应用卡方检验对两种干细胞分化后的NSE及GFAP阳性细胞数比例进行比较.结果 两种细胞原代培养48 h后均可见小的球状细胞团悬浮生长,折光性强.原代培养约7 d后传代,传代后细胞能重新形成球状细胞团,应用免疫细胞化学染色方法均可检测到细胞内nestin及BrdU的阳性表达,视网膜干细胞体外增殖的能力较神经干细胞弱.两种细胞均可在血清诱导条件下转变为贴壁生长,并分化出具有神经细胞形态的细胞.诱导第7天进行免疫细胞化学染色,检测出两种干细胞表达nestin阳性细胞数比例分别为（9.5±3.5）%及（9.1±0.7）%.视网膜干细胞分化后NSE及GFAP的阳性细胞数比例分别为（11.2±2.8）%及（18.9＋2.1）%,低于神经干细胞分化后两种标志物阳性细胞数比例[（34.1±63）%及（41.9±3.3）%],NSE、GFAP在两组表达的差异均有统计学意义（x2=103.23,P＜0.05;x2=74.36,P＜0.05）.结论 来源于睫状体区的大鼠视网膜干细胞形态、体外增殖及可分化特性与神经干细胞相似,但其增殖及分化为神经细胞的能力较神经干细胞弱.     

大鼠胚胎视网膜干细胞的分离培养

目的分离培养大鼠胚胎视网膜干细胞。方法从胎龄第16d的SD大鼠视网膜神经上皮分离视网膜细胞并进行悬浮培养,观察细胞增殖以及自发分化情况,采用免疫细胞化学方法检测Nestin、β-Tubulin、GFAP和Recoverin的表达。结果原代细胞可形成悬浮生长的神经球,传代后能形成新的细胞球。原代及传代细胞大部分表达神经干细胞标记物Nestin,分化后的细胞部分表达神经元标记物β-Tubulin或神经胶质细胞标记物GFAP,少数细胞表达光感受器细胞标记物Recoverin。结论分离培养的SD胚鼠视网膜神经干细胞可以在体外扩增并具有多分化潜能。     

人视网膜前体细胞的体外视网膜组织片下移植

目的研究人视网膜前体细胞移植到体外培养的人视网膜组织片下的细胞分化。方法取无眼部发育异常的4～5个月胚胎眼球，进行视网膜前体细胞分离培养。将传代的细胞移植到体外培养的视网膜神经上皮组织片下，通过光学显微镜和免疫组织化学观察细胞分化和组织整合情况。结果人视网膜前体细胞在体外培养时形成神经球样细胞团，传代后形成子代细胞团，表达神经干细胞标志Nestin。体外培养的视网膜组织片在5d、10d均能基本维持视网膜结构。移植到视网膜组织片下的视网膜前体细胞能够与其建立细胞连接。这些视网膜前体细胞分化后能够表达胶质纤维酸性蛋白、微管相关蛋白-2和视紫红质，分别为神经胶质细胞、神经元和光感受器细胞的特异蛋白。结论人视网膜前体细胞具有神经干细胞特征，在体外移植到培养的人视网膜组织片下，能够分化成相应的终末分化细胞。     

体外无血清培养新生SD大鼠视网膜神经细胞

目的 采用无血清培养建立新生SD大鼠视网膜神经细胞的体外培养方法,为视网膜神经细胞的体外实验研究奠定基础.方法 取出生后3～5d的SD大鼠视网膜,用胰蛋白酶消化分离获取细胞悬液,使用无血清神经原培养基(Neurobasal TM-A Medium)和添加剂B-27 Supplement Minus AO进行培养.倒置相差显微镜观察细胞形态及轴突生长情况.培养至第5天,用抗微管相关蛋白2抗体、抗视紫红质蛋白抗体及抗胶质纤维酸性蛋白抗体,行免疫细胞化学鉴定并计算视网膜视杆细胞的纯度.结果 采用无血清法培养的视网膜神经细胞生长良好,细胞伸出突起,部分神经元的突起交织呈网状.生长至第5天经免疫细胞化学证实其中神经元细胞占95.6％,而38.6％为视网膜视杆细胞,同时神经胶质细胞的生长得到了很好地抑制.结论 无血清培养法可以获取纯度较高的视网膜神经细胞,为研究视网膜光感受器细胞提供了理想的体外实验模型.     

大鼠骨髓间充质干细胞体外分化为视网膜神经节样细胞的实验研究

目的探讨大鼠骨髓间充质干细胞（BMSCs）体外向视网膜神经节细胞（RGCs）方向分化的可能性。方法取成年大鼠BMSCs原代培养，传代后获得高纯度BMSCs。采用碱性成纤维细胞生长因子（bFGF）诱导法，相差显微镜和荧光黄（LY）细胞内染色观察诱导后细胞形态的变化，并采用免疫细胞化学法检测微丝微管相关蛋白-2（MAP-2）、Thy1．1和胶质纤维酸性蛋白（GFAP）的表达。结果诱导后BMSCs呈现神经元样外观。LY染色可见细胞的多级突起，部分邻近细胞出现LY染色阳性。诱导后的神经元样细胞MAP-2和Thy1．1表达阳性，GFAP表达阴性。结论大鼠BMSCs经bFGF体外诱导可分化为具有RGCs表型的神经元样细胞，诱导后细胞间存在突触联系。     

全神经球贴壁培养法体外长期扩增视网膜前体细胞

目的:探寻一种既高效又能连续体外扩增视网膜前体细胞(RetinalProgenitorCell,RPC)的培养方法。方法:小鼠胚胎视网膜细胞采取神经球贴壁培养或直接贴壁培养法。神经球贴壁培养时,先经悬浮培养生成富含前体细胞的神经球,然后将低速离心分离出的神经球接种到Poly-D-Lysine包被的培养瓶,在前体细胞培养液中(含FGF-2、EGF和LIF)贴壁培养,头24h在培养液中添加10%的胎牛血清。直接贴壁培养法是将细胞悬液直接接种到预先包被Poly-D-Lysine的培养瓶。免疫组化和FACS分析神经球贴壁培养细胞的干细胞特性和分化能力,并与直接贴壁培养法得到的细胞进行比较。结果:神经球接种到预先包被Poly-D-Lysine的培养瓶后贴附到培养瓶底,逐渐形成贴壁生长的单层细胞。该法能够在体外长期扩增视网膜前体细胞,3个月内细胞能够传代10次以上。在RA诱导分化时,能够生成成熟视网膜细胞,表达视网膜细胞特异性标记。FACS分析和免疫组化染色显示神经球贴壁培养所得细胞在未分化时Nestin阳性率(92%)细胞率以及分化为成熟视网膜细胞的比率(53.7%),均高于直接贴壁培养法获得的细胞。结论:神经球贴壁培养法能够在体外长期大量扩增视网膜前体细胞,能较好地保持干细胞特性,并容易分化为成熟的视网膜细胞,较直接贴壁培养具有较大的优越性。     

胎儿视网膜前体细胞的分离培养

目的建立视网膜前体细胞的培养方法。方法分离8~12周流产胎儿的视网膜神经上皮细胞，采用悬浮和贴壁两种方法分别进行培养和传代，取传代细胞用含5%胎牛血清的、无碱性成纤维细胞生长因子（bFGF）的培养基诱导分化培养14 d，并采用免疫荧光法检测培养细胞诱导分化前后前体细胞和视网膜终末细胞标记物表达的改变。结果悬浮培养的细胞形成神经球并表达神经干细胞的标记物巢蛋白nestin，但无法成功传代扩增；贴壁培养的细胞可连续传代并表达nestin，传代细胞诱导分化后表达视网膜终末细胞的标记物胶质原纤维酸性蛋白(GFAP)、β微管蛋白(β-tubulin)和恢复蛋白recoverin。结论从8～12周的人胚胎视网膜神经上皮分离培养的视网膜前体细胞具有体外扩增和多分化潜能。（中华眼底病杂志，2007，23：98-100）     

视网膜细胞联合bFGF体外诱导大鼠骨髓间充质干细胞向神经样细胞的分化

目的 探讨大鼠骨髓间充质干细胞（BMSC）在体外分化为神经样细胞的有效途径,从而解决体外诱导分化效率低及存活状况不佳等问题.方法 采用密度梯度离心法和贴壁筛选法分离BMSC,免疫组化检测CD31、CD44、CD45、CD105表达并对细胞进行鉴定.按照诱导方式的不同分为3组：视网膜细胞＋碱性成纤维细胞生长因子（bFGF）组、bFGF组、不加诱导液组,分别诱导大鼠BMSC向神经样细胞分化.于诱导后第3、第7、第14天分别进行细胞形态学观察;并采用免疫细胞化学法检测神经微管蛋白-βⅢ（Tui1）、神经元特异性烯醇化酶（NSE）和胶质纤维酸性蛋白（GFAP）的表达,分析阳性细胞率：采用MTT法检测诱导后BMSC增殖状况,比较细胞存活率.相同时间组间比较用两独立样本t检验,组内不同时间比较用单因素方差分析.结果 形态学观察：视网膜细胞＋hFGF组诱导BMSC 12 h后出现形态变化,逐步形成典型的神经样细胞：bFGF阳性对照组也可见形成突起结构,但无典型的神经样细胞形态.免疫组化检测：处理组诱导3 d后即可检测到阳性细胞,随着诱导时间的延长.Tui1、NSE和GFAP阳性细胞率增加,与阳性对照组比较差异有统计学意义（P〈0.01）;阴性对照组未发现阳性细胞.存活率：各组BMSC存活率随着时间延长逐渐下降,但不同诱导方法对BMSC存活无显著影响.结论 模拟视网膜微环境配合bFCF能够诱导大鼠BMSC分化为神经样细胞并继续存活.     

体外诱导猪Müller细胞定向分化为光感受器细胞的研究

背景 大鼠、小鼠Müller细胞在体外能诱导分化为表达视网膜光感受器细胞特异标记的细胞,但目前有关成年猪Müller细胞分化为视网膜光感受器细胞的研究鲜有报道.目的 研究成年猪Müller细胞于体外定向诱导后分化成视网膜第一级传导神经元光感受器细胞.方法 消化成年猪眼视网膜组织,分离Müller细胞行体外继代单层贴壁培养.使用定向分化培养基对P2、P3和P4代Müller单层贴壁细胞及先形成细胞球悬浮培养2—3d,然后再对贴壁细胞进行诱导分化,最后结合细胞形态和免疫荧光染色结果鉴定Müller细胞以及诱导分化效果.结果 免疫荧光染色结果显示,P2,P3和P4 Müller细胞均能表达Müller细胞特异蛋白分子标记,即谷氨酸合成酶(GS),P3 Müller细胞还同时表达另一种Müller细胞特异蛋白分子标记,神经胶质纤维酸性蛋白(GFAP).免疫荧光染色分析并计算视网膜光感受器细胞特异标记视紫质Rhodopsin阳性率,P2 Müller单层贴壁分化细胞为(27.99±6.53)％,P2悬浮细胞球分化为(16.54±3.40)％.P2悬浮细胞球诱导分化后形态更趋向神经元,而P2代Müller单层贴壁细胞分化后形态仍趋向于成纤维细胞.随着培养代数的增加,细胞球定向分化Rhodopsin阳性表达程度逐渐减弱,P2、P3和P4 Rhodopsin阳性率分别为(56.23±7.32)％、(35.26±8.55)％和(12.68±3.18)％,差异无统计学意义(F=2.618,P=0.099).同代细胞随着诱导时间的延长,Rhodopsin阳性表达有所减弱,差异无统计学意义(P=0.099),但分化细胞形态更为细长.结论 成年猪Müller细胞离体培养后可定向分化为表达视网膜光感受器样细胞特异标记的细胞.细胞球悬浮培养2～3d,以及延长诱导分化时间都能使得分化细胞形态更为细长.     

视网膜发育中的神经干细胞

视网膜作为脑组织的延伸,存在大量神经干细胞,在内外源性因子机制及各基因调节机制作用下,增殖分化为视网膜各型神经元及神经胶质细胞。应用无血清培养及单细胞克隆技术可分离培养出特异性表达nestin的视网膜干细胞。由于视网膜于细胞具备自我更新能力及多分化潜能,有望用于退行性神经疾病如:视网膜色素变性、老年黄斑变性、晚期青光眼等的细胞替代治疗或药物、基因治疗的载体。     

Differences between the neurogenic and proliferative abilities of Müller glia with stem cell characteristics and the ciliary epithelium from the adult human eye

Much controversy has arisen on the nature and sources of stem cells in the adult human retina. Whilst ciliary epithelium has been thought to constitute a source of neural stem cells, a population of Müller glia in the neural retina has also been shown to exhibit neurogenic characteristics. This study aimed to compare the neurogenic and proliferative abilities between these two major cell populations. It also examined whether differences exist between the pigmented and non-pigmented ciliary epithelium (CE) from the adult human eye. On this basis, Müller glia with stem cell characteristics and pigmented and non-pigmented CE were isolated from human neural retina and ciliary epithelium respectively. Expression of glial, epithelial and neural progenitor markers was examined in these cells following culture under adherent and non-adherent conditions and treatments to induce neural differentiation. Unlike pigmented CE which did not proliferate, non-pigmented CE cells exhibited limited proliferation in vitro, unless epidermal growth factor (EGF) was present in the culture medium to prolong their survival. In contrast, Müller glial stem cells (MSC) cultured as adherent monolayers reached confluence within a few weeks and continued to proliferative indefinitely in the absence of EGF. Both MSC and non-pigmented CE expressed markers of neural progenitors, including SOX2, PAX6, CHX10 and NOTCH. Nestin, a neural stem cell marker, was only expressed by MSC. Non-pigmented CE displayed epithelial morphology, limited photoreceptor gene expression and stained strongly for pigmented epithelial markers upon culture with neural differentiation factors. In contrast, MSC adopted neural morphology and expressed markers of retinal ganglion cells and photoreceptors when cultured under similar conditions.This study provides the first demonstration that pigmented CE possess different proliferative abilities from non-pigmented CE. It also showed that although non-pigmented CE express genes of retinal progenitors, they do not differentiate into neurons in vitro, as that seen with Müller glia that proliferate indefinitely in vitro and that acquire markers of retinal neurons in culture under neural differentiation protocols. From these observations it is possible to suggest that Müller glia that express markers of neural progenitors and become spontaneously immortalized in vitro constitute a potential source of retinal neurons for transplantation studies and fulfil the characteristics of true stem cells due to their proliferative and neurogenic ability.     

体外诱导大鼠视网膜Müller细胞向神经节细胞定向分化的研究

目的 研究鼠视网膜Müller细胞经体外条件培养基诱导后去分化为神经干细胞及进一步定向分化成神经节样细胞的特性.方法 实验研究.体外培养出生后7-10 d的Sprague Dawley大鼠视网膜Müller细胞,应用逆转录聚合酶链反应(RT-PCR)法及免疫荧光染色法鉴定Müller细胞纯度.取培养的第3或4代Müller细胞,用含有N2、碱性成纤维细胞生长因子和表皮生长因子的Delbeccon's modified Eagle's medium(DMEM)-F12干细胞条件培养基培养3～5 d后,再用含5%胎牛血清、脑源性神经营养因子和视黄酸的DMEM培养基诱导分化7～10 d,采用免疫荧光染色法分别鉴定去分化及再诱导分化后的细胞.结果 RT-PCR及免疫荧光染色结果显示,分离培养的视网膜Müller细胞纯度可达(95.17±2.68)%以上.干细胞条件培养基培养3～5 d后,大部分Müller细胞汇集形成细胞球,经免疫荧光染色法鉴定,显示细胞球内(95.26 ±1.35)%以上的细胞Nestin表达阳性,(90.33±4.12)%以上细胞BrdU表达阳性.将这些细胞球进一步诱导分化后,可见细胞球内细胞可向外扩展、铺开,分化出形态各异的细胞,其中约(21.14±1.49)%细胞表达神经节细胞特异性标记物Thy1.1阳性.结论 成年啮齿动物视网膜Müller细胞经体外条件培养基诱导后,可以产生具有增殖能力和分化潜能的神经干细胞,并可进一步定向分化为神经节样细胞,这为干细胞研究和视神经再生治疗等提供了新的方法和手段.     

大鼠胚胎视网膜前体细胞的分离、体外培养及鉴定

目的探讨流式细胞分析技术、免疫荧光及^3H—Thymidine分析对大鼠胚胎视网膜前体细胞性质及其体外增殖进行鉴定的可行性。方法来源于19d胚胎大鼠视网膜的视网膜前体细胞,使用流式细胞分析及免疫荧光技术从数量及形态上对细胞性质进行鉴定。采用无血清培养基体外培养,通过^3H-Thymidine分析、形态学观察及统计学分析,研究细胞增殖情况。结果从胚胎大鼠全层视网膜分离出的原代视网膜前体细胞,流式细胞分析结果显示：培养0d时,22．23％的细胞神经上皮干细胞蛋白（Nestin）呈阳性表达,16．04％的细胞Sox-2呈阳性表达,19．66％的细胞钙结合蛋白呈阳性表达,其余终末视网膜细胞标记物（胶质纤维酸性蛋白、CD90、视紫红质、C反应蛋白、突触前膜列阵蛋白）均呈极微量阳性或阴性。免疫荧光结果显示大部分细胞及细胞球（〉90％）Nestin呈阳性表达。培养6d后,流式细胞分析显示43．36％的细胞Nestin阳性,免疫荧光显示Nestin及胶质纤维酸性蛋白呈阳性。连续4d^3H-Thymidine分析及形态学观察、统计学分析原代视网膜前体细胞初期增殖良好。结论流式细胞分析、免疫荧光及^3H—Thymidine等免疫学技术可很好的对视网膜前体细胞性质及其增殖情况进行鉴定。大鼠胚胎原代视网膜前体细胞表现出神经干细胞的特性,根据检测手段不同,阳性结果不同,其原代视网膜前体细胞体外培养初期增殖良好。     

Mesenchymal stem cells derived from human limbal niche cells

Purpose. We investigated whether human limbal niche cells generate mesenchymal stem cells. Methods. Limbal niche cells were isolated from the limbal stroma by collagenase alone or following dispase removal of the limbal epithelium (D/C), and cultured on plastic in Dulbecco's modified Eagle's medium (DMEM) with 10% fetal bovine serum (FBS), or coated or three-dimensional Matrigel in embryonic stem cell medium with leukemia inhibitory factor and basic fibroblast growth factor. Expression of cell markers, colony-forming units-fibroblast, tri-lineage differentiation, and ability of supporting limbal epithelial stem/progenitor cells were compared to limbal residual stromal cells. Results. Stromal cells expressing angiogenesis markers were found perivascularly, subjacent to limbal basal epithelial cells, and in D/C and limbal residual stromal cells. When seeded in three-dimensional Matrigel, D/C but not limbal residual stromal cells yielded spheres of angiogenesis progenitors that stabilized vascular networks. Similar to collagenase-isolated cells, D/C cells could be expanded on coated Matrigel for more than 12 passages, yielding spindle cells expressing angiogenesis and mesenchymal stem cells markers, and possessing significantly higher colony-forming units-fibroblast and more efficient tri-lineage differentiation than D/C and limbal residual stromal cells expanded on plastic in DMEM with 10% FBS, of which both lost the pericyte phenotype while limbal residual stromal cells turned into myofibroblasts. Upon reunion with limbal epithelial stem/progenitor cells to form spheres, D/C cells expanded on coated Matrigel maintained higher expression of p63α and lower expression of cytokeratin 12 than those expanded on plastic in DMEM with 10% FBS, while spheres formed with human corneal fibroblasts expressed cytokeratin 12 without p63α. Conclusions. In the limbal stroma, cells subjacent to limbal basal epithelial cells serve as niche cells, and generate progenitors with angiogenesis and mesenchymal stem cells potentials. They might partake in angiogenesis and regeneration during corneal wound healing.     

胚胎与成人视网膜神经细胞培养

目的 建立胚胎及成人视网膜神经细胞体外培养系统，为视网膜神经细胞的基础研究与药物开发提供实验模型。 方法 10～13周龄胎儿及20～40岁成人视网膜神经层用不同的酶进行消化，分散的细胞接种于预先经过包被的细胞培养盘内，加入或不加入表皮生长因子(epidermal growth factor, EGF)、成纤维细胞生长因子(fibroblast growth factor, FGF)、脑源性神经营养因子(brainderived neurotrophic factor, BDNF)、神经营养素 4(neurotrophic-4，NT-4)等培养。通过BrdU掺入、免疫组织化学及免疫荧光等方法检测培养细胞增殖并辨别细胞成分。 结果 胚胎及成人视网膜细胞可在体外连续培养100及180 d以上。加入EGF、FGF、BDNF或NT-4可明显促进胚胎与成人视网膜神经元存活，胎儿视网膜细胞增殖。与对照组相比，处理组神经元或神经节细胞的百分率较高。 结论 胚胎及成人视网膜神经细胞培养技术为视网膜神经细胞基础研究及药物开发提供了一种十分有价值的手段，加入外源性的生长因子可促进培养的视网膜神经细胞存活、增殖与分化。 (中华眼底病杂志, 2002, 18: 279-282)     

Stem cells in the teleost retina: persistent neurogenesis and injury-induced regeneration

The retina of the adult teleost fish is an important model for studying persistent and injury-induced neurogenesis in the vertebrate central nervous system. All neurons, with the exception of rod photoreceptors, are continually appended to the extant retina from an annulus of progenitors at the margin. Rod photoreceptors, in contrast, are added to differentiated retina only from a lineage of progenitors dedicated to making rods. Further, when the retina is lesioned, the lineage that produces only rods ceases this activity and regenerates retinal neurons of all types. The progenitors that supply neurons at the retinal margin and rod photoreceptors and regenerated neurons in the mature tissue originate from multipotent stem cells. Recent data suggest that the growth-associated neurogenic activity in the retina is regulated as part of the growth hormone/insulin-like growth factor-I axis. This paper reviews recent evidence for the presence of stem cells in the teleost retina and the molecular regulation of neurogenesis and presents a consensus cellular model that describes persistent and injury-induced neurogenesis in the retinas of teleost fish.     

体外培养及诱导胚兔视网膜及脑神经干细胞分化的研究

目的 比较体外不同培养条件对视网膜及脑神经干细胞(NSCs)视紫红质的纯化能力及不同诱导条件对NSCs的诱导分化能力.方法 取胚兔视网膜及大脑皮质制备单细胞悬液,分别在5种不同培养基中进行体外培养并纯化.选取无血清条件下传3代的NSCs,分别在2种培养基中诱导8～10 d.采用免疫荧光法及流式细胞仪检测所获得细胞的神经干细胞和视网膜神经上皮细胞抗原的表达.结果 免疫荧光法显示无血清培养条件下2种组织来源的NSCs均部分表达巢蛋白.流式细胞术显示2种诱导方式均部分细胞表达巢蛋白,较诱导前明显降低,而视紫红质及Thy1.1的表达均较诱导前明显增高.经5%胎牛血清(FBS)诱导的细胞表达视紫红质较联合应用全反式视黄酸(ATRA)时高,差异均有统计学意义(χ2=30.59,6.76;P<0.01).但Thy1.1表达低于后者,差异也有统计学意义(χ2=6.19,22.92;P=0.01).结论 无血清培养基添加N2、EGF、bFGF、LIF 4种因子可以获得最佳纯化效果.2种诱导培养基都能够诱导NSCs的分化,视网膜NSCs分化为视网膜神经上皮细胞的能力高于大脑皮质NSCs.     

Comparison of the proliferation and differentiation ability between adult rat retinal stem cells and cerebral cortex-derived neural stem cells

Recent studies have demonstrated that retinal stem cells (RSCs) and stem cells of the central nervous system both exhibited the abilities of self-renewal, proliferation and differentiation into multilineage. In the present study, we compared the proliferation and differentiation abilities between RSCs and cerebral corticex-derived neural stem cells (CNSCs) of adult rats. Stem cells isolated from pigmented ciliary margins of eyes and cerebral cortical tissues of adult rats were cultured in 96-well plates that contained serum-free medium with epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF). In contrast to RSCs, which stopped proliferating after the 8th week, the total cell count of neurospheres in CNSCs increased twofold at the 5th week and more than fourfold at the 10th week after in vitro culture. In contrast, RSCs stopped proliferating after 8 weeks of culture. After adding 2% fetal calf serum and withdrawing EGF and bFGF from the culture medium, the percentages of nestin-positive cells(20.6 +/- 2.7%), microtubule-associated-protein-2-positive neurons (33.2 +/- 3.9%) and glial-fibrillary-acidic-protein-positive glial cells(51.3 +/- 6.2%) in the differentiated CNSCs were significantly higher than those in the differentiated RSCs (10.2 +/- 1.9, 22.3 +/- 1.3 and 44.6 +/- 5.1%, respectively; p < 0.05). We also found that the combination of transforming growth factor beta type III with retinoic acid played an important role in the induction of CNSCs to differentiate into opsin-positive cells. Our data demonstrated that CNSCs displayed a higher ability of proliferation and retinal lineage. This report also offers an alternative protocol of cell reproduction for producing retinal cells.     

Epidermal growth factor receptor in cultured human retinal pigment epithelial cells

BACKGROUND: Migration and proliferation of retinal pigment epithelial (RPE) cells play an important role in proliferative vitreoretinopathy. Epidermal growth factor receptor (EGFR) is a cell surface receptor with intrinsic tyrosine kinase activity. The engagement of the receptor by its ligand can induce intracellular mitogenic signal transduction pathways and stimulate proliferation, migration and differentiation of cells. This experiment aimed to investigate the activation and role of EGFR signal transduction pathway in proliferation of human RPE cells. METHODS: Cultured human RPE cells of the 3rd to 6th passages were studied by colorimetric assay for cellular growth and survival (MTT assay) to test the effects of EGF (0.1, 1, 10, 50, and 100 ng/ml) and fetal bovine serum (FBS) on proliferation of human RPE cells. An in vitro wound healing model was also set up, and the number of cells that had entered the denuded area was counted. The human RPE cells were cultured for 3 days with 0.1% FBS, 10% FBS, 10 ng/ml EGF + 0.1% FBS and a combination of EGF and 10% FBS, respectively. Immunohistochemical staining and in situ hybridization were used to observe the expressions of EGFR protein and mRNA, respectively. Activation of mitogen-activated protein kinase (MAPK) was detected by immunohistochemical method with specific antiphosphorylated extracellular signal-regulated kinase (ERK)1/2 antibody. RESULTS: EGF stimulated proliferation and migration of cultured human RPE cells in a concentration-dependent manner. The maximum of the proliferation rate of RPE cells was 81.8% with EGF at a concentration of 10-100 ng/ml of EGF in serum-free Dulbecco's modified essential medium (DMEM) and 122.7% at a concentration of 1-10 ng/ml of EGF in 5% FBS DMEM (p < 0.001); there was a significant difference between serum-free DMEM groups and 5% FBS DMEM groups. The maximum of the migration rate of the cells was 438.9% at a concentration of 10-100 ng/ml of EGF in 10% FBS DMEM, 147% with 10% FBS, and only 36% with EGF in 0.1% FBS at the concentration of 10 ng/ml (p < 0.001). EGF promoted the expression of EGFR protein and mRNA in RPE cells. FBS cooperated with EGF in the stimulation of EGFR expression, and it had a stronger effect in the process than EGF alone. After 3 days of incubation with EGF, phosphorylated ERK1/2 was detectable in the nucleus of RPE cells, whereas cells presented immunostaining positive for phosphorylated ERK1/2 in the cytoplasm before stimulation, indicating that EGF could induce MAPK nuclear translocation. CONCLUSION: EGF could induce EGF-EGFR-MAPK signal transduction pathway in human RPE cells in a concentration-dependent manner in vitro, which may play a key role in the activation of human RPE cell proliferation and migration.