Efficient cryopreservative conditions for cultivated limbal and conjunctival epithelial cells

PURPOSE: To examine the effects of cryopreservation on the viability of cultivated corneal limbal and conjunctival epithelial cells and to evaluate the optimal conditions for cryopreservation. METHODS: The cultivated human limbal epithelial cells (HLECs) were stored in media including 20%, 50%, and 90% fetal bovine serum (FBS) and 10% dimethyl sulfoxide (DMSO) at -196 degrees C for 1 week. The cultivated rabbit conjunctival epithelial cells were stored in 10%, 20%, and 50% FBS with 10% glycerol or DMSO as a cryoprotectant at -196 degrees C for 1 week. After thawing, cell viability was assessed using the trypan blue vital staining and 3-[4,5-dimethylthiazol-2-yl]-2,5-dephenyl tetrazolium bromide (MTT) assay. Immunofluorescent staining was performed with cytokeratin 3/12 antibody. Colony-forming efficiency (CFE) was evaluated 2 weeks after culture. RESULTS: HLECs cryopreserved with 50% FBS showed the highest cell viability, whereas those with 20% FBS revealed the lowest survival rate (87.1% +/- 0.8% and 79.8% +/- 4.01%, respectively; P = 0.030). CFE of HLECs was 2.13 +/- 1.35%, 2.31 +/- 2.23%, and 1.94 +/- 0.72% in cells with 20%, 50%, and 90% FBS, respectively (P > 0.05). For conjunctival epithelial cells, the cell viability was the highest with 50% FBS and 10% glycerol (95.0% +/- 4.27%), and the lowest survival rate was observed in the condition of 10% FBS and 10% DMSO (80.0% +/- 5.49%). CFE of cryopreserved conjunctival epithelial cells was 14.1% +/- 1.9% in cells with 20% FBS and glycerol and 13.5% +/- 2.0% in those with 20% FBS and DMSO (P > 0.05). HLECs expressed CK3/12 after cryopreservation in all conditions examined. CONCLUSIONS: The best results were yielded by 50% FBS for cell viability in HLECs. Glycerol seems to be superior to DMSO in cell viability of the rabbit conjunctival epithelium after cryopreservation.     

Stromal niche controls the plasticity of limbal and corneal epithelial differentiation in a rabbit model of recombined tissue

PURPOSE: The adult rabbit limbal basal epithelium contains corneal epithelial stem cells, which have been characterized by a negative expression of keratin-3 (K3) and a lower expression of connexin 43 (Cx43). This study was conducted to determine whether the limbal stroma dictates the plasticity of limbal and corneal epithelial differentiation. METHODS: Viable epithelial sheets of the central cornea and the pigmented limbus were isolated from Dutch belted rabbits by incubation of 50 mg/mL of dispase II in supplemental hormonal epithelial medium (SHEM) for 18 hours at 4 degrees C. The cleavage plane was studied by immunostaining with antibodies against K3, Cx43, integrin beta1, and collagen IV. Viability of single cells derived from these sheets was assessed by a live-dead assay. Such limbal (L) and corneal (K) epithelial sheets were recombined with either limbal (Ls) or corneal (Ks) stroma, and cultured in SHEM for 10 days before lifting to the air-fluid interface for 1 week. The resultant epithelial phenotype was determined by histology and immunostaining to K3 and Cx43, and apoptosis was investigated by Hoechst and TUNEL nuclear staining. RESULTS: Viability of isolated limbal and corneal epithelial sheets was determined to be 91.1% +/- 2.9%. The basal epithelium of isolated limbal epithelial sheets was positive for integrin beta1, negative for K3, but weakly positive for Cx43, and still retained patches of collagen IV. All recombinants showed stratified epithelia, with intraepithelial cysts with desquamated debris noted only in K/Ks, and epithelial outgrowth onto the insert filter from L/Ls. As expected, expression of K3 was negative in the basal layer of L/Ls, but positive in that of K/Ks. Expression of K3 was sporadically positive in the basal layer of L/Ks but largely negative in that of K/Ls. Expression of Cx43 was uniformly expressed in the basal layer of the K/Ks, but weak in that of L/Ls, K/Ls, and L/Ks. A higher apoptosis index was only noted in intraepithelial cysts of K/Ks. CONCLUSIONS: These results strongly indicate that the limbal stroma modulates epithelial differentiation, proliferation and apoptosis in the direction favoring stemness, whereas the corneal stroma promotes differentiation. Further investigation into elements constituting such a niche should help unveil the secrecy whereby stemness is controlled.     

The side population cells in the rabbit limbus sensitively increased in response to the central cornea wounding

PURPOSE: Side population (SP) cells are known to reside in the limbus as putative corneal epithelial stem cells. This study was performed to demonstrate the presence and the characteristics of SP cells in the rabbit limbal epithelium and explore their sensitivity in response to the central cornea wounding. METHODS: To sort out the SP cells, freshly isolated rabbit limbal and central corneal epithelial cells were subjected to Hoechst 33342 dye efflux assay. For characterization of the sorted SP cells, RT-PCR analysis, semi-dry three-dimensional (3-D) cell culture, and transplantation in nude mice were performed. To explore wound sensitivity of the limbal SP cells, the rabbit central cornea was wounded by direct contact of a 6-mm paper disk soaked with 1 N NaOH, and changes in the population size of the SP cells and the colony-forming efficiency (CFE) was monitored on days 1, 2, and 5 after wounding. RESULTS: The SP cells were present in the rabbit limbal epithelium with an incidence of 0.73% +/- 0.14% (n = 8) and were smaller in cell size than the major population (MP) cells, quiescent in the cell cycle, and in the undifferentiated state. The SP cells were able to regenerate the cornea-like structure with basal enrichment of p63-positive cells by in vitro 3-D culture and in vivo transplantation, all of which were best achieved by the whole population (WP) of cells comprising SP and MP cells. After central cornea wounding, this rare population of the limbal SP cells increased in size fivefold on day 1 and then decreased on day 2. The transient increase in the SP cells was subsequently followed by the propagation of an increase in CFE in the limbal MP cells on day 2 and then in the corneal MP cells on day 5. In the hematopoietic colony-forming assay, the limbal SP cells gave approximately eightfold higher CFU than the limbal MP cells. CONCLUSIONS: The SP cells identified in the rabbit limbus are an undifferentiated and noncycling rare epithelial cell population, which sensitively respond to the central cornea wounding by their transient increase in the population size.     

Culture of the corneal epithelium--comparison of the mitotic potential of limbal cells from living and cadaveric donors

PURPOSE: We analyse effectiveness of corneal limbal cells' culture prepared from heart-beating organ donors, that include living donors and from cadaver donors buttons following 3 days storage in 4 degrees C in Likorol. MATERIAL AND METHODS: For experiment 12 adults (living and heart-beating organ donors) aged 28-63 (mean 46.3) and 12 corneal buttons of cadaver (aged 18-51, mean 34.1) were qualified. Tissue samples (1 mm2) were taken from superior corneal limbus. Sample from living donor obtained during routine operation was sent immediately to laboratory, as well as from heart-beating organ donor. The limbal biopsy of preserved cornea was taken after 3 days storage in 4 degrees C (Likorol). Samples were treated with trypsin/EDTA solution before culture. Collected cells in similar density in 1 ml of medium laid on dishes inserts, covered with fibrin (Tissucol) and cultured in presence of feeder layer of fibroblasts (L929 line). Epithelial cells were cultured for 14 days at 37 degrees C in humidified 5% CO2 atmosphere in supplemented 2:1 mixture of DMEM and Ham's F12. On the 14th day cells were collected. Number of cells per 1 ml of medium was counted by cytometer. Immunostaining for epithelium type (Keratin 3) was performed. RESULTS: The number of cells obtained from cadaver donors reached 184.2+/-14.9% whereas from living donors revealed 1013.1+/-104.2%, increase in relation to number of delivered cells. We observed only 0.83+/-0.3 colonies per microscopic area in cultures from preserved tissue versus 6.67+/-0.6 colonies in cultures from living donor. CONCLUSIONS: The preservation in 4 degrees C in Likorol significantly decreases proliferative potential of the corneal limbus.     

Different cell sizes in human limbal and central corneal basal epithelia measured by confocal microscopy and flow cytometry

PURPOSE: In the epidermis, the highest clonogenicity, a feature of stem cells (SCs), is found in the smallest keratinocyte. In the limbal-corneal (LC) epithelium the SCs are exclusively localized in the basal epithelial layer of the limbal domain. The current study was conducted to determine whether this spatial SC arrangement is reflected in differences in the cell size between limbal and corneal cells. METHODS: In vivo confocal microscopy was used to scan and measure the size of the cells of the central cornea and the superior limbus in five normal subjects, from the superficial to the basal cell layer. Limbal and corneal pure epithelial sheets were isolated by dispase digestion from human tissues and dissociated into single cells by trypsin digestion. The forward (FSC; a relative measure of cell size) and side (SSC; a relative measure of cytoplasmic complexity) light-scattering properties of these cells were determined by flow cytometry. RESULTS: Confocal microscopy showed that diameters of the basal cells of the limbal and corneal zones were 10.1 +/- 0.8 and 17.1 +/- 0.8 micro m, respectively. The corresponding values for the superficial layers were 19.9 +/- 1.6 and 36.6 +/- 1.6 microm, respectively (P < 0.0001). The mean FSC and SSC of the limbal cells amounted to 65.7% +/- 8.7% and of the corneal cells, 74.4% +/- 4.6%. Furthermore, only 1.40% +/- 0.83% and 0.69% +/- 0.37% of the corneal cells had FSC and SSC equal to the lowest 15% of FSC and SCC of the limbal cells, respectively, indicating that the limbus contained a substantial proportion of very low FSC and SSC cells for which there was no corneal counterpart. CONCLUSIONS: The data collectively demonstrate that the smallest cells are located in the limbal basal epithelium. This feature may help isolate corneal SCs located in the limbus.     

角膜干细胞增殖与分化表达实验研究

目的 了解角膜缘干细胞体外生长的增殖分化特性,检测上皮细胞生长因子对干细胞增殖的促进作用。方法 采用ＤＭＥＭ和Ｆ１２培养基进行兔角膜上皮细胞培养,用克隆形成率（ＣＦＥ）、免疫组化染色和蛋白质免疫印迹等方法检测细胞的增殖力和分化表达状况。结果角膜缘干细胞（ＬＣ）在本培养条件下能够正常传代生长５代,ＣＦＥ为（５．０７±２．３５）％,而角膜中央上皮细胞（ＣＣ）仅第１次传代生长,ＣＦＥ为（１．１２±０．８     

角质细胞生长因子2促进兔角膜碱烧伤上皮愈合机制的研究

目的　探讨角质细胞生长因子2 (KGF- 2 )对实验性兔角膜中央碱烧伤后角膜上皮愈合的作用及其机制。方法　24只新西兰白兔的24只角膜碱烧伤眼按随机数字法分成4组,每组6只眼,其中A、B、C组为治疗组,分别以3种不同浓度: 1μg/ml、50μg/ml、100μg/mlKGF 2滴眼液治疗;D组为对照组,用磷酸盐缓冲液(PBS)滴眼液治疗;观察角膜上皮愈合情况,并做形态学检查及P63、角质蛋白单克隆抗体(AE5)、表皮细胞生长因子单克隆抗体(EGFR)免疫组化研究。结果　1 ~100μg/mlKGF 2能够促进兔角膜上皮愈合。角膜碱烧伤24h后100μg/mlKGF- 2组和对照组角膜上皮愈合率分别为40%和74% (P<0 .05);第4天时4组均出现一定反复;第10天时各治疗组近完全愈合。碱烧伤后第7天即可观察到P63阳性细胞不仅存在于角膜缘区的部分基底细胞中,同时也向角膜内迁移。如角膜碱烧伤后第7天角膜缘区P63阳性细胞数: 100μg/mlKGF 2组为( 53 .8±2. 6)个,对照组为(29. 5±2. 2)个,正常角膜为(17. 0±2. 1)个(P=0. 000);同时非角膜缘区P63阳性细胞数分别为: 100μg/mlKGF 2组为(69. 5±2. 8)个,对照组为(19 5±2 8)个,正常角膜为0个(P=0 .000)。结论　KGF- 2可激活角膜上皮干细胞,使其不断增殖分化,从而促进角膜上皮损伤的愈合。     

Corneal epithelial cultures generated from organ-cultured limbal tissue: factors influencing epithelial cell growth

PURPOSE: To explore the in vitro proliferative potential of human limbal epithelial cells after 31 degrees C organ-culture storage and to investigate putative factors influencing it. METHODS: 185 cultures of limbal explants were carried-out either from full-thickness explants (n = 102) or from enzymatically dissociated cells (n = 83) seeded on a feeder layer of human keratocytes. Epithelial outgrowth was assessed by phase contrast microscopy using a computerized image analysis software. Cell phenotype was evaluated by transmission electron microscopy and immunocytology. Univariate and multivariate analysis were performed to determine factors influencing epithelial growth in culture. RESULTS: An epithelial outgrowth of 100 square mm or more was observed in 52% of cultures, (average growth area: 440 +/- 256 mm at three weeks). Corneal epithelial phenotype was confirmed by transmission electron microscopy, and cytokeratin pattern. Cytokeratine 19, deltaNp63, nestin and vimentin positive staining revealed undifferentiated epithelial cells in both explant and cell suspension cultures at three weeks. Short death to cornea retrieval time (p < 0.03) and female donors (p < 0.01) were associated with higher cell growth. Enzymatic treatment of explants by trypsin, but not dispase, decreased cell proliferation at two (p < 0.03) and three weeks (p < 0.04). Donor age, duration of corneal storage, and source of the explant did not influence the cell growth. CONCLUSION: Organ-culture conditions can preserve limbal cell mitotic potential if limbal tissue is excised early after circulatory arrest. Human keratocytes can be used as a feeder layer allowing epithelial cells to maintain poorly differentiated phenotype in culture. Further investigations are needed to explain the influence of the donor sex on epithelial cell growth in culture.     

角膜缘niche细胞与基质细胞维持角膜缘干细胞功能的对比研究

目的　比较角膜缘niche细胞（limbal niche cells，LNCs）与角膜缘基质细胞（limbal stromal cells，LSCs）在维持角膜缘干细胞功能上的不同特性。方法　将LNCs和LSCs分别从6个角膜缘组织分离，并在相同的条件下培养、传代。LNCs与LSCs经丝裂霉素C（mitomycin C,MMC）处理后分为LNCs组与LSCs组作为饲养细胞分别与角膜缘干细胞共培养，比较两组角膜缘干细胞克隆形成率（colony-forming efficiency,CFE）、上皮细胞复层化以及细胞标志物和部分基因的表达。结果　LNCs组角膜缘干细胞CFE（6.57±1.54）%高于LSCs组（1.43±0.47）%。 LNCs组细胞复层上皮数（4~5层）多于LSCs组（2~3层）。角膜缘干细胞克隆与免疫荧光染色及mRNA半定量分析结果显示，LNCs组比LSCs组表达了更多干细胞标志物ΔNp63，能更有效地维持角膜缘干细胞的细胞特性。逆转录PCR分析结果显示，LNCs组与LSCs组都分泌了一些维持角膜缘干细胞生长的生长因子，但LNCs组比LSCs组高表达上皮型钙黏蛋白（E-cadherin），低表达营养神经素3（NT3），能更好地支持角膜上皮增殖。结论　LNCs比LSCs能更好地支持角膜缘干细胞的生长及维持其干细胞特性。     

The Preliminary Experimental Study of Induced Differentiation of Embryonic Stem Cells into Corneal Epithelial Cells

Purpose: To study preliminarily induced differentiation of embryonic stem cells into corneal epithelial cells in vitro.Methods: Murine embryonic stem cells were co-cultured with Rabbit limbal corneal epithelial cells in Transwell system to induce differentiation. Mophological and immunohistochemical examination were implemented.Results: The induced cells from embryonic stem cells have an epithelial appearance. The cells formed a network and were confluent into film gradually after being co-cultured with rabbit limbal corneal epithelial cells for 24 ~ 96 hours. The cells ranged mosaic structure and localized together with clear rim. Most of the cells showed polygonal appearance. Transmission electron microscope showed lots of microvilli on the surface of induced cells and tight junctions between them. These epithelial-like cells expressed the corneal epithelial cell specific marker cytokeratin3/cytokeratin12. Conclusion: The potential mechanism of the differentiation of murine embryonic stem cel     

High expression of p63 combined with a large N/C ratio defines a subset of human limbal epithelial cells: implications on epithelial stem cells

PURPOSE: To characterize human limbal epithelial cells based on the expression levels of nuclear protein p63 and the nucleus-to-cytoplasm (N/C) ratio. METHODS: Limbal, peripheral, and central corneal epithelia were separated from the stroma by Dispase II and subsequently were treated with trypsin to obtain single-cell suspensions. Cytospin smears of the cell suspensions were double immunostained for p63 and then stained for any one of the markers (acidic cytokeratins [AE1], K5, K3, or connexin 43 [Cx43]). They were counterstained with propidium iodide. More than 100 cells from each zone were analyzed for p63 expression levels and nuclear/cellular area using quantitative confocal microscopy. RESULTS: A gradient of p63-positive cells was observed in corneal and limbal epithelial cells. The percentage of p63-positive cells and the level of p63 expression were significantly higher in the limbal than in the peripheral or central corneal epithelium. Two-parameter (p63 levels and N/C ratio) analysis revealed the presence of a distinct population of small cells with higher levels of p63 and a large N/C ratio in the limbal epithelium. Such limbal epithelial cells were positive for AE1 and K5 but negative for K3 and Cx43. CONCLUSIONS: These results suggest that this distinct group of small cells in the limbal epithelium with greater N/C ratio, expressing high levels of nuclear protein p63, probably represent corneal epithelial stem cells.     

Partial enrichment of a population of human limbal epithelial cells with putative stem cell properties based on collagen type IV adhesiveness

The concept that corneal epithelium stem cells reside in limbus has been recognized for more than a decade, but isolation of these stem cells has not been accomplished. This study was an initial attempt to isolate a population of human limbal epithelial cells enriched for certain putative stem cell properties based on their phenotype. Epithelial cells harvested from fresh human limbal rings and their primary cultures were allowed to adhere to collagen IV-coated dishes for 20 min and 2 hr, sequentially. The rapidly adherent cells (RAC), slowly adherent cells and non-adherent cells were evaluated for certain stem cell properties: (a) BrdU-label retention, (b) expression of basal cell (integrin beta1, p63, ABCG2) and differentiation (involucrin, keratin 12) markers, and (c) colony forming efficiency (CFE) and growth capacity on a 3T3 fibroblast feeder layer. Among unfractionated cells and the three selected populations, the RAC, accounting for about 10% of whole population, were enriched 5-fold in BrdU label-retaining cells, displayed the highest number of integrin beta1 and p63 positive and involucrin negative cells, expressed high levels of DeltaNp63 and ABCG2 mRNA, and lacked involucrin and K12 expression, and possessed the greatest CFE and growth capacity. These findings demonstrated for the first time that human limbal epithelial cells with stem cell properties can be partially enriched by their adhesiveness to collagen IV. The RAC population enriched for certain putative stem cell properties may prove useful in the future for transplantation to diseased and damaged corneas with limbal stem cell deficiency.     

Existence of small slow-cycling Langerhans cells in the limbal basal epithelium that express ABCG2

Despite the obvious importance of limbal stem cells in corneal homeostasis and tumorigenesis, little is known about their specific biological characteristics. The purpose of this study was to characterize limbal slow-cycling cells based on the expression of ABCG2 and major histocompatibility complex (MHC) class II and the cell size. Wistar rats were daily injected with 5-bromo-2-deoxyuridine (BrdU) at a dose of 5 mg/100 g for 2 weeks. After 4-week BrdU-free period, corneal tissues were excised, and immunofluorescence staining for ABCG2, BrdU, and MHC class II was performed by confocal microscopy. In another series, corneal tissues of normal rat were double immunostained for ABCG2, keratin 14, keratin 3, CD11c, and MHC class II. In addition, limbal, peripheral and central corneal epithelial sheets were isolated by Dispase II digestion and dissociated into single cell by trypsin digestion and cytospin preparations were double immunostained for ABCG2 and MHC class II. The cell size and nucleus-to-cytoplasm (N/C) ratio of limbal ABCG2+ cells were analyzed and compared with those of cells from other zones. BrdU label-retaining cells (LRCs) with expression of ABCG2 were found in the limbal epithelial basal layer, but not in other parts of the cornea. Approximately 20% of these cells were MHC class II positive. All MHC class II+ cells in the corneal epithelium were positive for CD11c, a marker for dendritic cells (DCs). Double labeling with ABCG2 and keratin 14 showed that nearly four-fifth of limbal ABCG2+ cells were positive for keratin 14 but negative for keratin 3, exhibiting an undifferentiated epithelial cell lineage. Cytospin sample analysis revealed the presence of a distinct population of smaller ABCG2+ cells with expression of MHC class II with a larger N/C ratio in the limbal epithelium. A new population of small slow-cycling cells with large N/C ratio has been found to express ABCG2 in the limbal epithelial basal layer. Some of these cells normally express MHC class II antigen. These findings may have important implications for our understanding of the characteristics of limbal slow-cycling cells.     

体外兔胚胎成纤维细胞为饲养层克隆兔角膜缘干细胞

目的研究兔胚胎成纤维细胞体外克隆兔角膜缘干细胞。方法兔胚胎成纤维细胞经丝裂霉素C(MMC)处理成饲细胞,用消化法培养兔角膜缘基底层细胞并接种于含有经MMC处理饲细胞的12孔培养板,进行原代培养。观察其光镜特征、电镜结构,用间接免疫细胞化学染色等对克隆的细胞进行综合鉴别。结果克隆的细胞呈典型的上皮细胞形态,电镜下可见微绒毛、桥粒、张力丝等典型上皮细胞结构,单克隆抗体AE1、PCNA染色后细胞大多数阳性,单克隆抗体AE5染色后细胞染色偶见阳性。结论体外兔胚胎成纤维细胞为饲养层成功地克隆出兔角膜缘干细胞。     

Viability of limbal epithelium after anterior lamellar harvesting using a microkeratome

OBJECTIVE: To determine the viability in cold eye bank storage of different layers of central and limbal corneal epithelium, including the limbal basal stem cell population, on days 0, 3, 6, and 9 after harvest using a large diameter microkeratome system. METHODS: Twenty-two human whole globes not suitable for transplantation were obtained from an eye bank (San Diego Eye Bank, San Diego, California) and used for study. Large-diameter anterior corneal discs were prepared using a large diameter microkeratome and stained with calcein AM and an ethidium homodimer to differentiate live from dead cells, respectively. A laser confocal microscope and digital imaging were used to distinguish live (green) from dead (red) cells. Central and limbal epithelial regions were isolated and the middle and basal epithelial sections were cell counted by 3 independent observers. These sections were stored up to 9 days at 4 degrees C in an eye bank corneal storage medium. Differences were tested using nonparametric methods. MAIN OUTCOME MEASURES: The percentage of live cells in each of these epithelial layers was determined for up to 9 days in cold eye bank corneal storage medium. RESULTS: At all time points studied, the better protected basal epithelial layers displayed greater mean viability than the overlying middle epithelial layers. However, the difference was not statistically significant on all days. When comparing the basal epithelial viability of the limbal and central regions, after day 0 in 4 degrees C cold organ culture, the observed viability of the limbal basal epithelium, the purported location of the limbal epithelial stem cell region, was significantly greater than that of the central epithelium. On day 0, median limbal basal versus central basal epithelial viability were 100% (range, 71.7-100%) versus 98.4% (range, 88.9-100%) (P>0.05); on day 3, 100% (range, 64.3-100%) versus 63.4% (range, 13.6-95.5%) (P<0.0005); on day 6, 95.0% (range, 35.0-100%) versus 28.0% (range, 0-92.0%) (P<0.0005); and on day 9, 95.0% (range, 3.7-100%) versus 68.6% (range, 0-100%) (P<0.0005). CONCLUSIONS: After microkeratome harvesting, the limbal basal epithelium is significantly longer lived in cold eye bank storage than central basal epithelium and the middle layers of limbal and central epithelium. This longevity not only bodes well for organ storage of limbal grafts, but also confirms the hardiness of the stem cell region.     

体外人羊膜培养兔角膜缘上皮细胞的细胞形态与连接复合体形成的研究

目的观察体外人羊膜上培养出的兔角膜缘上皮细胞形态特征及与羊膜基底膜连接复合体的形成。方法将15只新西兰白兔角膜缘组织（2mm×2mm）,于37℃ 5％ CO2孵箱中用1．2U／ml裂解酶Ⅱ处理20min,之后在人羊膜上皮面先行浸液培养2周,后行气-液培养2周。于培养期间,每周定期进行透射电镜检查,以观察连接复合体的形成过程,培养至第4周后,采用AE5免疫组织化学、高碘酸．希夫、苏木精-伊红等染色方法鉴定分化的上皮细胞,鉴别杯状细胞,观察细胞的形态特征。结果兔角膜缘上皮细胞体外培养10—14d可充满人羊膜面,对AE5免疫组织化学方法染色分化出的上皮细胞均呈阳性而高碘酸．希夫染色均呈阴性。苏木精-伊红染色显示从兔角膜缘上皮细胞分化出的上皮细胞与正常兔角膜上皮细胞相比无明显差异;自培养至第14天均未见与羊膜基底膜的连接复合体形成;于第21天时仅观察到初始阶段的连接复合体,第28天时仍未见明显变化。结论于体外人羊膜上培养的兔角膜缘上皮细胞分化出的细胞是角膜上皮细胞,其形态与正常兔角膜上皮细胞相同,并与羊膜基底膜仅形成初始阶段的连接复合体。     

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.     

培养兔自体角膜缘干细胞移植的实验研究

目的 观察以羊膜为载体的兔角膜缘于细胞膜片移植治疗兔角膜缘于细胞缺损的效果。方法 制造兔角膜缘干细胞缺损的动物模型,以右眼为实验眼,从兔左眼取角膜缘组织,将兔角膜缘干细胞消化下来,接种于铺有羊膜的无菌六孔培养板中,待细胞形成多层角膜上皮细胞后,对兔角膜缘干细胞缺损动物模型行角膜缘干细胞羊膜移植术,并对治疗后的角膜进行裂隙灯及病理学检查。结果 临床和组织病理学染色证实：体外培养的兔角膜缘干细胞可在羊膜上继续增生、分化为多层角膜上皮细胞;角膜缘干细胞移植术后兔角膜缘轻度充血、角膜上皮完整、基质细胞浸润减轻、新生血管减少或消失。结论 应用角膜缘干细胞羊膜移植术可恢复其角膜上皮结构的完整性,减少角膜新生血管的形成,维持角膜缘的细胞屏障功能。     

异体角膜缘上皮细胞培养后移植的实验研究

目的观察含培养的角膜缘上皮细胞的羊膜片移植到角膜缘干细胞损伤的异体兔眼角膜上的效果。方法把羊膜为载体组织块培养的角膜缘上皮细胞移植到角膜缘干细胞损伤的异体兔眼角膜上,术后观察角膜混浊度、角膜新生血管、角膜上皮等情况,定期兔进行病理组织学检查。结果角膜缘上皮细胞在羊膜上培养16d形成3～4层,用含有培养的异体角膜上皮细胞的羊膜片移植的12只兔眼,术后第5天,损伤的角膜表面全部上皮化,第16天开始,12只兔眼逐渐出现排斥反应。结论含培养的角膜缘上皮细胞羊膜片异体移植术后早期角膜全部上皮化,晚期则出现排斥反应。     

培养角膜缘干细胞羊膜移植治疗碱烧伤动物的实验研究

目的 观察培养生长于羊膜的角膜缘干细胞移植的治疗角膜缘碱烧伤伤的效果。方法 将兔角膜缘干细胞在的代培养后接种于羊膜,对新西兰大白兔角膜缘碱烧伤动物模型行角膜缘干细胞羊膜移植术,并对治疗后的角膜进行临床及病理学检查。结果 体外培养的兔角膜缘士细胞可在羊膜上继续增殖、分化为密集的角膜上皮细胞层;角膜缘干细胞移植术后兔角膜缘轻度充血、角膜上皮完整基质细胞浸润减轻、新生血管减少。组织病理学染色证实,角膜缘