Nestin在高眼压大鼠视网膜神经胶质细胞中的表达

目的探讨第六类中间丝蛋白nestin在高眼压大鼠视网膜神经胶质细胞中的表达情况及意义。方法42只SD大鼠采用烧灼右眼涡静脉的方法制作高眼压模型为模型组,剪开左眼结膜作为假手术组。测量并记录眼压,计数术后不同时间点视网膜神经节细胞（RGCs）数。Westernblot半定量分析术后视网膜内nestin蛋白含量。免疫电镜检测nestin在高眼压大鼠视网膜Mailer细胞上的诱导表达。行nestin／谷氨酰胺合成酶（GS）或nestin／胶质纤维酸性蛋白（GFAP）免疫荧光双标,共焦显微镜观察nestin／GFAP在Mailer细胞上的表达情况。结果术后各时间点模型组与假手术组眼压的差异有统计学意义（P〈0．05）。术后1～3周模型组RGCs数量显著减少,与假手术组比较差异有统计学意义（P〈0．05）。免疫荧光结果显示术后2h～3周,模型组nestin在Maller细胞上表达的荧光强度逐渐增强,与假手术组比较差异有统计学意义。Westernblot半定量分析结果与免疫荧光染色结果一致。免疫电镜结果进一步证实眼压升高后Mailer细胞上出现nestin的诱导表达。结论Nestin在Maller细胞上的诱导表达是Mailer细胞对眼压升高产生的一种反应,nestin的表达量与病程进展相一致。眼压升高时,nestin在Mailer细胞上诱导表达,尤其在足板处的强烈表达,可能对RGCs具有保护作用。Nestin有望成为一种新的研究视网膜损伤的生物标记物。     

Growth kinetics and transplantation of human retinal progenitor cells

We studied the growth kinetics of human retinal progenitor cells (hRPCs) isolated from donor tissue of different gestational ages (G.A.), determined whether hRPCs can be differentiated into mature photoreceptors and assessed their ability to integrate with degenerating host retina upon transplantation. Eyes (12-18 weeks G.A.) were obtained with IRB approval and retinas were enzymatically dissociated. Cells were expanded in vitro, counted at isolation and at each passage, and characterized using immunocytochemistry and PCR. GFP positive hRPCs were co-cultured with retinal explants from rd1 and rhodopsin −/− mice, or transplanted into B6 mice with retinal photocoagulation and rhodopsin −/− mice. Eyes were harvested for histological evaluation following transplantation. Our results show that hRPCs from 16 to 18 weeks G.A. had the longest survival in vitro and yielded the maximum number of cells, proliferating over at least 6 passages. These cells expressed the retinal stem cell markers nestin, Ki-67, PAX6 and Lhx2, and stained positively for photoreceptor markers upon differentiation with serum. Some of the GFP positive cells used for transplantation studies showed evidence of migration into the degenerative host retina and expressed rhodopsin. In conclusion, we have determined the growth kinetics of hRPCs and have shown that cells from donor tissue of 16-18 weeks G.A. exhibit the best proliferative dynamics under the specified conditions, and that hRPCs can also be differentiated along the photoreceptor lineage. Further, we have also demonstrated that following transplantation, some of these cells integrate within the host retina and differentiate to express rhodopsin, thereby supporting the potential utility of hRPC transplantation in the setting of retinal degenerative disorders.     

胚胎千细胞诱导分化为视网膜祖细胞的体外研究

目的 探讨小鼠胚胎干细胞(mouse embryonic stem cell,mESC)诱导为视网膜祖细(retinal progenitor cells,RPC)的体外培养方法,为致盲性视网膜变性疾病的治疗提供种子细胞.方法 用细胞免疫荧光染色法和流式细胞术对mESC进行mESC标记物阶段特异性胚胎抗原1、细胞增殖核抗原Ki67、细胞周期和碱性磷酸酶进行鉴定后,在无血清条件下悬浮培养形成拟胚体(embryoid bodies,EB)并添加抑制因子1、左右决定因子A和γ-促分泌酶抑制剂等诱导分化为RPC,并对其分化的细胞进行标记物兔来源配对盒基因6(paired box6,Pax6)、兔来源性别决定区Y框蛋白(Sox2)和鼠来源转录因子同源异型框蛋白(orthodentical homeobox2,Otx2)的检测以及增殖能力和细胞周期的检测.结果 mESC标记物碱性磷酸酶阳性表达,特异性胚胎抗原1阳性率为(80.66±0.64)％,Ki67和细胞周期检测显示有较高增殖能力.定向诱导分化后,RPC标记物Pax6、Sox2和Otx2阳性率分别为(50.87±2.97)％、(49.10±2.60)％和(32.01±3.87)％,Ki67和细胞周期检测均显示诱导后的RPC具有一定的增殖能力.结论 在特定的细胞因子作用下,mESC可以诱导分化为RPC.     

胚胎和生后大鼠视网膜干细胞在体内和体外的分化差异

目的 研究胚胎和生后大鼠视网膜干细胞（RPCs）在体内和体外的分化.方法 取胚胎18 d和生后2周SD大鼠视网膜,分别用悬浮法及贴壁法培养.传至第1代后转入分别含10 ng/ml睫状神经营养因子（CNTF）、20 ng/ml表皮生长因子（EGF）、10 ng/ml碱性成纤维细胞生长因子（bFGF）、10%视黄酸、10%胎牛血清的DMEM：F12中进行诱导分化,贴壁后2、3、5、6 d的细胞及胚胎18 d,生后1、3、5、7、14 d的大鼠视网膜切片分别行nestin、vimentin、opsin及GFAP的二步法免疫组织化学染色.结果 大鼠的RPCs在悬浮时呈球状生长,nestin染色阳性,悬浮培养传至第1代,贴壁培养传至第5代.CNTF、bFGF、EGF及视黄酸组在培养至6 d时可呈神经元样细胞改变,有轴突,但持续出现nestin阳性.生后2周的RPCs无法诱导成opsin阳性细胞.结论 RPCs可在体外培养并传代,其在分化过程中形态学的改变先于功能学变化.光感受器细胞的体外诱导较困难.     

Influence of hypoxia on retinal progenitor and ganglion cells in human induced pluripotent stem cell-derived retinal organoids

AIM: To observe the effect of low oxygen concentration on the neural retina in human induced pluripotent stem cell (hiPSC)-derived retinal organoids (ROs). METHODS: The hiPSC and a three-dimensional culture method were used for the experiments. Generated embryoid bodies (EBs) were randomly and equally divided into hypoxic and normoxic groups. Photographs of the EBs were taken on days 38, 45, and 52, and the corresponding volume of EBs was calculated. Simultaneously, samples were collected at these three timepoints, followed by fixation, sectioning, and immunofluorescence. RESULTS: The proportion of Ki67-positive proliferating cells increased steadily on day 38; this proliferation-promoting effect tended to increase tissue density rather than tissue volume. On days 45 and 52, the two groups had relatively similar ratios of Ki67-positive cells. Further immunofluorescence analysis showed that the ratio of SOX2-positive cells significantly increased within the neural retina on day 52 (P<0.05). In contrast, the percentage of PAX6- and CHX10-positive cells significantly decreased following hypoxia treatment at all three timepoints (P<0.01), except for CHX10 at day 45 (P>0.05). Moreover, the proportion of PAX6-/TUJ1+ cells within the neural retinas increased considerably (P<0.01, <0.05, <0.05 respectively). CONCLUSION: Low oxygen promotes stemness and proliferation of neural retinas, suggesting that hypoxic conditions can enlarge the retinal progenitor cell pool in hiPSC-derived ROs.     

视网膜修复及再生过程中干细胞及其衍生细胞行为学特性的研究现状

近年来各种来源的干细胞、祖细胞和前体细胞在视网膜组织修复及再生研究中的应用倍受瞩目.研究发现,视网膜干细胞、视网膜祖细胞和前体细胞、骨髓干细胞、胚胎干细胞和脑源性神经干细胞都有增殖和分化成视网膜神经细胞的能力,并且在损伤条件下这类细胞能够参与视网膜的修复和再生过程.视网膜色素上皮细胞和Müller细胞具有的转分化能力也使之可能成为视网膜修复和再生的另一来源.     

Human neural progenitor cells promote photoreceptor survival in retinal explants

Different types of progenitor and stem cells have been shown to provide neuroprotection in animal models of photoreceptor degeneration. The present study was conducted to investigate whether human neural progenitor cells (HNPCs) have neuroprotective properties on retinal explants models with calpain- and caspase-3-dependent photoreceptor cell death. In the first experiments, HNPCs in a feeder layer were co-cultured for 6 days either with postnatal rd1 mouse or normal rat retinas. Retinal histological sections were used to determine outer nuclear layer (ONL) thickness, and to detect the number of photoreceptors with labeling for calpain activity, cleaved caspase-3 and TUNEL. The ONL thickness of co-cultured rat and rd1 retinas was found to be almost 10% and 40% thicker, respectively, compared to controls. Cell counts of calpain activity, cleaved caspase-3 and TUNEL labeled photoreceptors in both models revealed a 30-50% decrease when co-cultured with HNPCs. The results represent significant increases of photoreceptor survival in the co-cultured retinas. In the second experiments, for an identification of putative survival factors, or a combination of them, a growth factor profile was performed on conditioned medium. The relative levels of various growth factors were analyzed by densitometric measurements of growth factor array membranes. Following growth factors were identified as most potential survival factors; granulocyte colony stimulating factor (G-CSF), granulocyte-macrophage colony stimulating factor (GMCSF), insulin-like growth factor II (IGF-II), neurotrophic factor 3 (NT-3), placental growth factor (PIGF), transforming growth factors (TGF-β1 and TGF-β2) and vascular endothelial growth factor (VEGF-D). HNPCs protect both against calpain- and caspase-3-dependent photoreceptor cell death in the rd1 mouse and against caspase-3-dependent photoreceptor cell death in normal rat retinas in vitro. The protective effect is possibly achieved by a variety of growth factors secreted from the HNPCs.     

Loss of photoreceptor potential from retinal progenitor cell cultures, despite improvements in survival

Retinal degeneration (RD) results from photoreceptor apoptosis. Cell transplantation, one potential therapeutic approach, requires expandable stem cells that can form mature photoreceptors when differentiated. Freshly dissociated primary retinal cells from postnatal day 2-6 (PN2-6) mouse retina can give rise, post-transplantation, to photoreceptors in adult recipients. Unfortunately, incorporation rates are low; moreover, photoreceptor potential is lost if the same PN2-6 cells are cultured prior to transplantation. We investigated the identity of the cells forming photoreceptors post-transplantation, using FACS sorted primary postnatal day (PN) 3-5 Rho-eGFP retinal cells. Higher integration rates were achieved for cells that were expressing Rho-eGFP at PN3-5, indicating that post-mitotic photoreceptor precursors already expressing rhodopsin form the majority of integrating rods. We then investigated improvement of cell culture protocols for retinal progenitor cells (RPCs) derived from PN3-5 retinal cells in vitro. We succeeded in improving RPC survival and growth rates 25-fold, by modifying retinal dissociation, replacing N2 supplement with B27 supplement minus retinoic acid (B27 − RA) and coating flasks with fibronectin. However, levels of rhodopsin and similar photoreceptor-specific markers still diminished rapidly during growth in vitro, and did not re-appear after in vitro differentiation. Similarly, transplanted RPCs, whether proliferating or differentiated, did not form photoreceptors in vivo. Cultured RPCs upregulate genes such as Sox2 and nestin, markers of more primitive neural stem cells. Use of these cells for RD treatment will require identification of triggers that favour terminal photoreceptor differentiation and survival in vitro prior to transplantation.     

缺氧培养下大鼠视网膜祖细胞与脑神经干细胞内钙离子浓度差异的研究

目的:比较缺氧培养条件下新生大鼠视网膜祖细胞(retinal progenitor cells,RPCs)与脑神经干细胞(neural stemcells,NSCs)钙离子浓度的差异。方法:分离新生大鼠RPCs及大脑皮质NSCs,进行无血清体外培养;采用荧光免疫细胞化学的方法进行干细胞鉴定;缺氧培养后,光镜观察细胞形态,采用钙离子荧光探针结合激光共聚焦显微镜测定细胞内钙离子荧光强度。结果:缺氧培养后,大脑皮质NSCs较早出现肿胀、伸出突起等变化,随缺氧时间延长,两种细胞内钙离子荧光强度逐渐增强,缺氧12h后RPCs内钙离子荧光强度小于脑皮质NSCs(P<0.05),差异具有统计学意义。结论:缺氧培养12hRPCs内钙离子浓度低于大脑皮质NSCs。     

大鼠视网膜前体细胞的传代培养及体外分化诱导

目的了解表皮生长因子（EGF）、碱性成纤维细胞生长因子（bFGF）及睫状神经营养因子（CNTF）对其分化的影响。方法取孕18d的SD大鼠胚胎眼的视网膜，分别用悬浮法及贴壁法培养。传至第一代后转入分别含10ng／mlCNTF、20ng／mlEGF、10ng／mlbFGF、10％胎牛血清的DMEM：F12中进行诱导分化，贴壁后2、3、4、6d分别行nestin、Vimentin、Opsin及GFAP的二步法免疫组织化学染色。结果大鼠的RPCs在悬浮时呈球状生长。nestin及Vimentin染色阳性，悬浮培养传至一代，贴壁培养传至五代，传代后细胞数量不断减少并可在体外分化为含视网膜光感受器细胞及胶质细胞的混合神经元。CNTF、bFGF及EGF不同程度地增加了光感受器细胞的比例。结论RPCs可在体外培养并传代。CNTF、bFGF及EGF参与视网膜发育的调节。     

银杏内酯B联合视网膜干细胞移植对青光眼大鼠的影响及机制研究

目的：研究银杏内酯B联合干细胞移植对青光眼大鼠的影响及相关机制。

方法：实验共分为五组：正常对照组(Control)、青光眼模型组(GLA)、干细胞组(RSCs)、银杏内酯B组(GKB)与混合组(RSCs+ GKB)。眼球组织进行HE染色,TUNEL染色检测视网膜神经节细胞的凋亡,免疫印迹法(Western blot)检测Bcl-2、Bax以及Cleaved caspase-3和Cleaved caspase-9的蛋白表达水平,实时荧光定量PCR(RT-qPCR)分别检测各组组织中Bcl-2、Bax mRNA表达水平。

结果：HE染色结果显示,给予干细胞或银杏内酯B处理,减少纤维间质水肿与空泡的出现,混合组纤维间质少见水肿与空泡; 银杏内酯B联合干细胞处理后显著减少视网膜神经节细胞的凋亡,上调Bcl-2的蛋白与mRNA表达水平,并下调Bax的蛋白与mRNA表达水平、Cleaved caspase-3和Cleaved caspase-9的蛋白表达水平。

结论：银杏内酯B联合干细胞能够抑制青光眼大鼠视网膜神经节细胞的凋亡,改善青光眼,其作用机制可能与调控Bcl-2、Bax、Cleaved caspase-3和Cleaved caspase-9因子的表达有关。     

低氧诱导趋化因子受体表达对视网膜前体细胞迁移能力的影响

背景体外研究表明,趋化性细胞因子受体4（CXCR4）及其配体基质细胞衍生因子-1（SDF．1）在诱导视网膜前体细胞（RPCs）定向迁移的过程中可能起重要作用。RPCs表达CXCR4升高能增强干细胞的趋化活性,从而提高移植细胞的定向迁移能力。目的探讨RPCs在低氧条件下CXCR4受体的表达。方法分离孕龄17d的NIH小鼠的胚胎视网膜细胞并制备成含5×10^6～10×10^6个／L细胞的悬液,将细胞接种到25cm2培养瓶中,用全神经球贴壁培养法进行培养。RPCs在正常O2（体积分数16％O2）和低O2（体积分数10％O2）环境中培养12h和24h后,用逆转录聚合酶链反应（RT—PCR）法检测CXCR4和缺氧诱导因子-1（HIF-1）mRNA的表达;流式细胞仪（FACS）检测RPCs中CXCR4阳性细胞的百分比;Boyden小室实验观察30μg／L的SDF-1对RPCs的趋化效应。结果10％O2培养12h和24h后,RPCs中CXCR4mRNA的表达量（CXCR4mRNA／B—actinmRNA）分别为0．28±0．07和0．48±0．17,比正常氧培养组的0．16±0．02升高了1．75倍和3．00倍,10％O2培养12h和24h后RPCs中HIF-1mRNA表达量（HIF—1mRNA／B—actinmRNA）分别为0．18±0．07和0．38±0．13,比正常氧培养组的0．06±0．01升高了3．00倍和6．30倍,差异有统计学意义（P〈0．01）。Boyden小室实验表明,10％O2培养12h和24h后SDF-1对RPCs的趋化效应由正常氧的13．00％分别上升到36．00％和46．00％。FACS检测表明,10％O2诱导12h和24h后,RPCs中CXCR4阳性细胞率由正常氧浓度的9．01％分别上升到26．90％和46．10％,差异均有统计学意义（P〈0．01）。结论RPCs在低氧条件下CXCR4受体表达增加,同时对SDF-1的趋化能力增强。HIF-1的表达增加是CXCR4表达增高的可能机制。     

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。     

Induced expression of hematopoietic- and neurologic-expressed sequence 1 in retinal pigment epithelial cells during newt retina regeneration

Newts can regenerate their organs even as adults. For instance, when their neural retinas are completely removed by operation, the remaining retinal pigment epithelial (RPE) cells dedifferentiate to reconstruct neural retinas. To elucidate the molecular mechanisms of newt retina regeneration, we investigated genes upregulated in dedifferentiating RPE cells using differential display methods. We observed that a cDNA fragment of hematopoietic- and neurologic-expressed sequence 1 (Hn1) appeared to be induced within a few days of surgical removal of newt neural retina. Using an anti-HN1 antiserum against the recombinant HN1 protein, we carried out immunohistochemical analyses. The anti-HN1 antiserum recognized the plexiform layers and ganglion cell layer (GCL) but not the RPE cell layer in unoperated (normal) newt retinas. Using a glial fibrillary acidic protein antibody, Hn1 was shown to be possibly expressed in glial cells in normal neural retina. During retina regeneration, immunoreactivity for HN1 appeared in dedifferentiating RPE cells 10 days post-operation, and in retinal progenitor cells 18 days post-operation. Twenty seven days post-operation, HN1 immunoreactivity was localized in the plexiform layers and GCL as in the normal retina. Therefore, HN1 possibly plays an undefined role in dedifferentiating RPE cells and retinal progenitor cells during newt retina regeneration.     

Effect of endothelial progenitor cells derived from human umbilical cord blood on oxygen-induced retinopathy in mice by intravitreal transplantation

AIM: To investigate the effect of endothelial progenitor cells (EPCs) labeled by carboxy fluorescein diacetate succinimidyl ester (CFSE) on murine oxygen-induced retinopathy (OIR) by intravitreal transplantation. METHODS: After isolated from human umbilical cord blood mononuclear cells, EPCs were cultivated and then labeled with CFSE in vitro. C57BL/6J mice were placed to 75% hyperoxia chamber from P7 to P12 to establish OIR model. At P12, OIR mice were intravitreally injected with 1 μL suspension contained 2×105 EPCs (EPCs group) or isometric phosphate buffered saline (PBS group). The contralateral eye of each mice received no injection (OIR group). Evans blue angiography and frozen section were examined to track the labeled cells in OIR group at P15 and P19. Using retina paraffin sections and adenosinediphos phatase staining at P12 and P19, the effect of EPCs on OIR mice was evaluated quantitatively and qualitatively. RESULTS: The retinas from EPCs group with less non-perfusion area and fewer peripheral tufts were observed at P19, comparing with that from PBS or OIR group. The retinopathy in EPCs group receded earlier with less non-ganglion cells and neovascular nuclei, together with relatively regular distribution. The counts of the neovascular nuclei at P19 were reduced by 44% or 45%, compared with those of OIR group or PBS group respectively. Three days after EPCs injection, a large number of EPCs appeared in the vitreous cavity and adhered to the retinal surface. While at one week, the cells gathered between the internal plexiform layer and the inner limiting membrane, and some EPCs appeared in retinal vessels. CONCLUSION: EPCs transplantation can participate in the reparative procedure of the neovascularization in OIR.     

视网膜色素上皮细胞移植中CFDA-SE及免疫组化研究

目的探讨新型染料羧基荧光素乙酰乙酸[5-(and-6)-carboxyfluresceindiacetate,succinimidylester,CFDA-SE]与免疫组化方法相结合在视网膜色素上皮细胞(retinalpig-mentepithelialcells,RPECs)移植中应用的可行性。方法用CFDA-SE(10μmol·L-1)标记供体RPECs,37℃下孵育1min,通过玻璃体视网膜显微手术将细胞悬液植入同种异体青紫蓝兔视网膜下腔,分别在30d和60d时处死实验兔,荧光显微镜下观察标记的供体细胞,同时作紧密连接的结构蛋白ZO-1和细胞骨架蛋白Actin的免疫组化分析。结果荧光显微镜下观察到标记的供体RPECs可嵌插于宿主RPECs之间,铺成单层结构,并形成新的细胞间紧密连接,ZO-1、Actin的免疫组化结果经统计分析表明与原位RPECs之间的表达无显著差异(ZO-1:︱t︱=2.05,P<0.05;Actin:︱t︱=2·14,P<0.05)。结论CFDA-SE是一种快捷、稳定、安全的活体细胞染料,可作为理想的标记物应用于RPECs移植中。     

Notch-1调控视网膜前体细胞向视网膜神经节细胞分化

目的研究Notch-1对视网膜前体细胞(RPC)向视网膜神经节细胞(RGC)分化的调控作用。方法分离培养胚胎14 d龄Sprague-Dawley大鼠的RPC，实验组和对照组分别用含有Notch-1反义寡核苷酸链和无关序列寡核苷酸链的培养液进行诱导分化14 d，倒置相差显微镜每天观察细胞的生长和分化情况，Thy1.1标记RGC并进行计数。结果实验组和对照组的RPC都能分化为多种视网膜细胞类型，包括Thy1.1阳性的RGC，但两组RPC向RGC分化的百分比不同。实验组和对照组RGC的百分比分别为(16.57±4.31)%和(31.19±6.90)%，两组比较差异有统计学意义（t=9.84,P＜0.001）。结论Notch-1对RPC的分化具有负向调控作用，阻断Notch-1能促进RPC向RGC分化。(中华眼底病杂志, 2007, 23: 101-103)     

眼源性干细胞移植治疗视网膜疾病的研究进展

许多视网膜疾病,如视网膜色素变性、年龄相关性黄斑变性、视网膜脱离等都会引起视网膜光感受器的损伤,从而导致不可逆的视力丧失。目前对于此类疾病,临床上尚无有效的治疗方法。近年来随着对细胞工程研究的不断深入,干细胞移植被认为是治疗视网膜疾病最有前景的方法之一,将给不可逆性致盲眼病患者带来新的希望。本文就眼源性干细胞移植治疗视网膜疾病的最新研究进展综述如下。     

Characterization of early retinal progenitor microenvironment: presence of activities selective for the differentiation of retinal ganglion cells and maintenance of progenitors

The maintenance and differentiation of retinal progenitors take place in the context of the microenvironment in which they reside at a given time during retinal histogenesis. To understand the nature of the microenvironment in the developing retina, we have examined the influence of activities present during the early stage of retinal histogenesis on enriched retinal progenitors, using the neurosphere model. Early and late retinal progenitors, enriched as neurospheres from embryonic day 14 (E14) and E18 rat retina, respectively, were cultured in embryonic day 3 (E3) chick retinal conditioned medium, simulating the microenvironment present during early retinal histogenesis. Examination of the differentiation and proliferation of retinal progenitors revealed that the early microenvironment contains at least three regulatory activities, which are partitioned in different size fractions of the conditioned medium with different heat sensitivity. First, it is characterized by activities, present in heat stable <30 kDa fraction, that promote the differentiation of retinal ganglion cells (RGCs), the early born neurons. Second, it contains activities, present in heat-sensitive >30 kDa fraction, that regulate the number of early born neurons and maintain the pool of retinal progenitors. Third, it possesses activities, present in heat-sensitive <30 kDa fraction, that prevent the premature differentiation of early retinal progenitors into the late born neurons. Thus, our observations demonstrate the regulatory influence of microenvironment on the maintenance and differentiation of retinal progenitors and establish neurospheres as a viable model system for the examination of such influences.     

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。