人工角膜载体的体外构建及生物相容性研究

目的　应用壳聚糖（chitosan，CS）和蚕丝蛋白（silk fibroin，SF）构建组织工程角膜基质，探讨不同比例的CS和 SF共混膜的生物特性，为以后的角膜移植奠定基础。方法　将SF和CS按体积比3∶1和4∶1混合，体外构建具有相应器官特征的角膜基质层；体外培养原代兔角膜基质及上皮细胞，检测细胞分布情况和载体膜片的物理特性；免疫组织化学法测定细胞表型和分布情况,CCK-8试剂盒测定载体膜片毒性，电镜下观察细胞结构形态和附着情况，将构建的膜片植入兔板层角膜中检测组织生物相容性。结果　载体膜片的吸水率均在90%左右，明显强于天然角膜，抗拉力SF/CS 3∶1组为 0.90±0.02，SF/CS 4∶1组为 1.30±0.05，透光率均大于60%，且抗拉力和透光率随着CS含量增加而增强，但与天然角膜组织间仍存在差异。与载体膜片共培养的细胞在培养2周后，电镜下可见膜片上形成致密的细胞层，重构的板层角膜结构与天然角膜相似。CCK-8法检测结果显示，合成膜无明显毒性。免疫组织化学染色结果显示，培养出的基质细胞形态与天然角膜相似。动物板层移植术后，裂隙灯观察载体膜片组术后半个月内充血消失，无明显的前房炎症反应，术后1个月拆线时无明显新生血管。免疫组织化学法检测术后病理组织未发现CD4+、CD8+、CD31+T细胞浸润。结论　CS-SF可以用于组织工程角膜基质的构建，这为重建角膜基质提供了方向。     

组织工程角膜研究和应用进展

中国角膜供体材料的严重缺乏导致众多的角膜盲患者不能通过角膜移植来复明仍是临床棘手的问题。近年来,细胞生物学、组织工程学和材料学的发展为替代人角膜材料开辟了更广阔的前景;而且以深板层移植和内皮移植为代表的成分板层移植的推陈出新从临床技术上有力地推动了组织工程角膜的研发。现就脱细胞角膜基质板层材料、上皮细胞和内皮细胞组织工程的基础研究和临床应用进展进行述评。     

Construction of a complete rabbit cornea substitute using a fibrin-agarose scaffold

PURPOSE: To construct a full-thickness biological substitute of the rabbit cornea by tissue engineering. METHODS: Ten rabbit corneas were surgically excised, and the three main cell types of the cornea (epithelial, stromal, and endothelial cells) were cultured. Genetic profiling of the cultured cells was performed by RT-PCR for the genes COL8 and KRT12. To develop an organotypic rabbit cornea equivalent, we used a sequential culture technique on porous culture inserts. First, endothelial cells were seeded on the base of the inserts. Then, a stroma substitute made of cultured keratocytes entrapped in a gel of human fibrin and 0.1% agarose was developed. Finally, cultured corneal epithelial cells were grown on the surface of the scaffold. Stratification of the epithelial cell layer was promoted by using an air-liquid culture technique. Corneal substitutes were analyzed by light and electron microscopy. RESULTS: All three types of corneal cells were efficiently cultured in the laboratory, expanded, and used to construct a full-thickness cornea substitute. Gene expression analyses confirmed that cultured endothelial cells expressed the COL8 gene, whereas epithelial cells expressed KRT12. Microscopic evaluation of the cornea substitutes demonstrated that epithelial cells tended to form a normal stratified layer and that stromal keratocytes proliferated rapidly in the stromal substitute. The endothelial monolayer exhibited a pattern similar to a normal corneal endothelium. CONCLUSIONS: These findings suggest that development of a full-thickness rabbit cornea model is possible in the laboratory and may open new avenues for research.     

Ocular surface reconstruction using autologous rabbit oral mucosal epithelial sheets fabricated ex vivo on a temperature-responsive culture surface

PURPOSE: Autologous stem cell transplantation for total limbal stem cell deficiency is immunologically preferable, to avoid allograft rejection. This study was undertaken to investigate the possibility of a novel tissue engineering approach for ocular surface reconstruction, using autologous oral mucosal epithelial stem cells expanded ex vivo on temperature-responsive cell culture surfaces. METHODS: Rabbit oral mucosal epithelial cells cultured on temperature-responsive culture surfaces with mitomycin-C-treated 3T3 feeder cells for 2 weeks produced confluent epithelial cell sheets. Putative progenitor cell populations were estimated by colony-forming assays. Autologous transplantation of these cell sheets to surgically manipulated eyes was performed, and ocular surface reconstruction and cell phenotypic modulation were examined. RESULTS: All cultured oral epithelial cells were nonenzymatically harvested as transplantable intact cell sheets by reducing culture temperature to 20 degrees C. Oral epithelial cells were stratified in three to five cell layers more similar to corneal epithelium than to oral mucosal epithelium. Colony-forming assays and immunofluorescence for p63, beta1-integrin, and connexin 43 indicated retention of viable stem and/or progenitor cell populations in cell sheets. Autologous transplantation to rabbit corneal surfaces successfully reconstructed the corneal surface, with restoration of transparency. Four weeks after transplantation, epithelial stratification was similar to that in the corneal epithelium, although the keratin expression profile retained characteristics of the oral mucosal epithelium. CONCLUSIONS: Cell sheet harvest technology enables fabrication of viable, transplantable, tissue-engineered epithelial cell sheets that retain putative progenitor cells from autologous oral mucosal epithelial cells. Promising clinical capabilities for autologous tissue-engineered epithelial cell sheets for ocular surface reconstruction are indicated.     

单纯去细胞猪角膜基质穿透性角膜移植治疗兔角膜溃疡

目的:探讨单纯去细胞猪角膜基质材料诱导兔自体角膜细胞再生及修复兔角膜溃疡的可行性.方法:新西兰白兔10只制作成角膜溃疡模型,接受单纯去细胞猪角膜材料的穿透性角膜移植术,排除发生手术并发症眼(2只),剩余8只术后进行大体观察(裂隙灯检查),观察植片透明度、新生血管、上皮修复情况.分别于3,6,8,16和24wk取材进行组织学观察,并取16wk兔行超声生物显微镜(UBM)检查、32wk兔行透射电镜检查.结果:角膜溃疡修复,眼表重建8只.初期角膜上皮反复糜烂,荧光素纳染色有荧光堆积,HE 组织学检查提示4wk时上皮细胞复层化.角膜基质细胞沿材料板层生长,排列规律;3～7d角膜缘新生血管发生,位于浅基质层,1～20d达高峰,深入植片或沿缝线环形生长,拆线后逐渐消退,32wk后闭锁仅余3～4支微血管;UBM提示角膜恢复自然曲率,植床与植片尚未修复完善.TEM 提示成纤维细胞分泌胶原原纤维,参与材料改建.结论:CACM支持细胞3D生长,促进自体细胞长入,参与角膜修复改建.     

以干燥脱水法保存的异种角膜基质为载体构建人工生物角膜上皮组织

目的:观察以干燥脱水法保存的鸵鸟角膜基质为载体构建人工生物角膜上皮组织的生物学特性。方法:采用组织块培养法获得新西兰大白兔角膜缘干细胞,经胰蛋白酶消化法获得细胞,种植于干燥脱水法保存的鸵鸟角膜板层基质上,采用气液界面培养法进行培养,通过倒置显微镜、透射电子显微镜、荧光显微镜观察其形态学、生长特点,超微结构及免疫学特征。结果:在干燥脱水法保存的鸵鸟角膜基质上种植兔角膜缘干细胞,接种72h后,细胞形成单层,移置气液交界面后继续培养7～10d,逐渐形成复层。经光镜、透射电镜、及免疫学检测显示其具有角膜上皮组织的生物学特性。结论:兔角膜缘干细胞能够在干燥脱水法保存的鸵鸟角膜基质载体上生长,并可形成复层,基本具有正常角膜上皮细胞的形态、超微结构和生物学特性。     

组织工程角膜三维构建的实验研究

目的以人胚胎干细胞（hESC）诱导细胞为种子细胞,以脱细胞猪角膜基质（APCM）为支架三维构建生物工程角膜,以期用于穿透性角膜移植,解决角膜供体极度匮乏的难题。方法实验研究。无菌条件下将新鲜猪角膜组织置于0.5% SDS溶液中4 ℃脱细胞 24 h,获取APCM。将hESCs与人角膜基质细胞通过Transwell共培养5 d,获取眼周间充质干细胞（POMPs）,再于人晶状体上皮细胞源性条件培养基继续培养14 d获取角膜内皮样细胞并进行鉴定和筛选纯化。将纯化后扩增的角膜内皮样细胞接种于APCM构建角膜内皮植片,并移植入角膜内皮功能失代偿动物模型进行泵功能评估;采用人角膜缘干细胞（LSCs）来源的条件培养基培养hESCs 12 d,诱导其分化人角膜上皮样细胞并筛选鉴定,将其与APCM构建的角膜上皮植片移植于LSC失代偿动物模型的角膜缘,观察其眼表修复能力。结果诱导的人角膜内皮样细胞表达内皮细胞相关标记物vimentin、N-cadherin、Na+/K+ATP酶和ZO-1。构建的角膜内皮植片能够促使角膜内皮功能失代偿动物的角膜逐渐恢复透明。构建的角膜上皮细胞植片具有4～5层细胞复层结构,类似于正常角膜上皮,且能够一定程度上修复LSC失代偿动物模型眼表。结论采用hESCs诱导分化来源的细胞与APCM构建的人角膜内皮植片和人角膜上皮植片具有类似于正常角膜的功能,为全层生物角膜的构建提供了良好的实验和理论基础,具有良好的临床应用前景。     

兔角膜上皮和基质细胞共同培养模型中的相互作用

目的探讨利用细胞生物学和工程学原理在体外培养角膜上皮和基质细胞,模拟上皮和基质细胞相互作用的生存环境,了解角膜上皮细胞和基质细胞间的作用规律。方法分别进行体外兔角膜上皮细胞和基质细胞的原代培养及传代的二维平面培养,利用特殊培养装置制作上皮细胞和基质细胞共同培养的模型,达到两种细胞胞体不混合,而其分泌的成分可以相互渗透、相互作用的目的,从而更好地观察各自细胞的生长状态。描绘角膜上皮细胞和基质细胞的生长曲线及二者在相互作用模型中的生长曲线。利用激光共聚焦显微镜观察上皮细胞和基质细胞在单独培养和三维共同培养模型中上皮细胞胞间通讯的变化特点。结果角膜上皮细胞倍增时间为3．45d,共同培养的上皮细胞倍增时间为3．30d,角膜基质细胞倍增时间为2．11d,共同培养的基质细胞倍增时间为2．32d,共同培养的上皮细胞增长与单独培养的上皮细胞相比,差异有统计学意义（P〈0．01）,共同培养的基质细胞增长与单独培养的基质细胞相比,差异有统计学意义（P〈0．01）。与角膜基质细胞共同培养的角膜上皮细胞胞间通讯明显高于单独培养的基质细胞,差异有统计学意义（U=2．691,P〈0．05）。结论共同培养的细胞模型是理想的。角膜上皮细胞在与基质细胞共同存在的条件下比单独培养下的增殖能力增强,而角膜基质细胞在与上皮细胞共同存在的条件下比单独培养的增殖能力减弱;而上皮细胞在与基质细胞共同存在的条件下,细胞间通讯增强。     

An explanation for the central to peripheral thickness variation in the mouse cornea

Background: The mouse corneal stroma varies in thickness across its diameter. The purpose of the present study was to explain this variation and to advance our understanding of stromal lamellar architecture in the mammalian cornea. Methods: Eight C57BL/6 mice were killed, eyes enucleated, immersed in 2% glutaraldehyde fixative, processed and sectioned transversely for light and transmission electron microscopy. Transmission electron micrographs were assembled into montages and printed at 5000× magnification and used for lamellar counts and thickness assessments. Results: The mouse cornea had an average of 49.8 ± 2.4 lamellae centrally averaging 2.1 µm in thickness versus 35.5 ± 3.0 lamellae, averaging 1.9 µm in thickness peripherally. The central to peripheral decrease in number lamellae and lamellar thickness measured utilizing the transmission electron microscope was statistically significant (P < 0.005). Conclusions: This study demonstrated that the thickness difference between the thicker central and thinner peripheral mouse cornea is explained primarily by the number of lamellae present and that the peripheral lamellar dropout occurred in the anterior 2/3 of stroma. The decreased lamellar count towards the periphery suggested that not all lamellae cross the cornea limbus to limbus. These findings may be relevant to the thickness variation of the human cornea.     

羊膜载体培养标记兔角膜内皮细胞移植的研究

目的探讨以羊膜基底膜为载体培养兔角膜内皮细胞移植的可能性,为培养内皮细胞移植治疗角膜内皮失代偿疾病提供依据与方法。方法体外培养扩增兔角膜内皮细胞,采用亲脂性碳青染料(CM-DiI)对细胞进行标记,种植于去除上皮细胞的羊膜基底膜上,体外培养形成单层角膜内皮层,并进行形态学、组织学、超微结构及细胞标记情况的观察;将羊膜为载体培养的内皮层对切除后板层的兔角膜进行移植,同时以无培养内皮细胞的羊膜移植和单纯角膜后板层切除为对照,术后观察角膜透明度与厚度,对其进行组织学与细胞标记情况的检测。结果 5～7d 角膜内皮细胞即在羊膜基底膜上融合成单层,细胞为扁平多角形,排列紧密,密度可达(3202.84±347.77)个/mm~2,荧光显微镜下可见内皮细胞被 CM-DiI 标记后显现红色荧光;培养内皮层移植后角膜维持相对的透明与薄度,而无内皮细胞羊膜移植和单纯后板层切除两组对照角膜严重水肿、混浊,厚度明显超过实验组角膜;培养内皮移植后角膜形成新的内皮层,通过标记的细胞发现移植后细胞仍为培养移植的内皮细胞而非周边细胞的移行。结论羊膜基底膜是角膜内皮细胞生长和移植的良好载体,体外培养角膜内皮细胞移植有望代替供体角膜移植,具有广阔的应用前景。(中华眼科杂志,2006,42:925-929)     

组织工程角膜片移植治疗无菌性角膜溃疡的实验研究

目的探讨组织工程角膜片治疗角膜溃疡的可行性及疗效。方法将16只新西兰大白兔制作成角膜溃疡模型,随机分为2组,每组8只,分别作单纯羊膜移植和以羊膜为载体的组织工程角膜片移植。术后进行大体观察、裂隙灯观察、组织学观察、扫描电镜观察。结果羊膜为载体组织工程角膜片移植治疗角膜溃疡,平均7.5周溃疡完全愈合,角膜恢复透明性和屈光性,较单纯羊膜移植组(平均9周)角膜溃疡修复快,效果好结论羊膜为载体构建的组织工程角膜片可以有效治疗角膜溃疡。     

Transplantation of tissue-engineered human corneal epithelium in limbal stem cell deficiency rabbit models

AIM: To evaluate the biological functions of tissue-engineered human corneal epithelium (TE-HCEP) by corneal transplantation in limbal stem cell deficiency (LSCD) rabbit models. METHODS: TE-HCEPs were reconstructed with DiI-labeled untransfected HCEP cells and denuded amniotic membrane (dAM) in air-liquid interface culture, and their morphology and structure were characterized by hematoxylin-eosin (HE) staining of paraffin-sections, immunohistochemistry and electron microscopy. LSCD models were established by mechanical and alcohol treatment of the left eyes of New Zealand white rabbits, and their eyes were transplanted with TE-HCEPs with dAM surface outside by lamellar keratoplasty (LKP). Corneal transparency, neovascularization, thickness, and epithelial integrality of both traumatic and post transplantation eyes were checked once a week by slit-lamp corneal microscopy, a corneal pachymeter, and periodic acid-Schiff (PAS) staining. At day 120 post surgery, the rabbits in each group were sacrificed and their corneas were examined by DiI label observation, HE staining, immunohistochemistry and electron microscopy. RESULTS: After cultured for 5 days on dAM, HCEP cells, maintaining keratin 3 expression, reconstructed a 6-7 layer TE-HCEP with normal morphology and structure. The traumatic rabbit corneas, entirely opaque, conjunctivalized and with invaded blood vessels, were used as LSCD models for TE-HCEP transplantation. After transplantation, obvious edema was not found in TE-HCEP-transplanted corneas which became more and more transparent, the invaded blood vessels reduced gradually throughout the monitoring period. The corneas decreased to normal thickness on day 25, while those of dAM eyes were over 575μm in thickness during the monitoring period. A 4-5 layer of epithelium consisting of TE-HCEP originated cells attached tightly to the anterior surface of stroma was reconstructed 120 days after TE-HCEP transplantation, which was similar to the normal control eye in morphology and structure. In contrast, intense corneal edema, turbid, invaded blood vessels were found in dAM eyes, and no multilayer epithelium was found but only a few scattered conjunctiva-like cells appeared. CONCLUSION: The TE-HCEP, with similar morphology and structure to those of innate HCEP, could reconstruct a multilayer corneal epithelium with normal functions in restoring corneal transparency and thickness of LSCD rabbits after transplantation. It may be a promising HCEP equivalent for clinical therapy of corneal epithelial disorders.     

组织工程技术构建兔角膜基质组织的实验研究

目的 探讨应用组织工程技术构建兔角膜基质层组织的可行性。方法 新西兰大白免40只,即母兔及其亲生子兔共20对。分离获取新生子兔角膜基质细胞,扩增、培养,汇合后,接种于聚羟基乙酸(PGA),形成细胞-生物材料复合物,移植于对应的母兔角膜基质层。绿色荧光蛋白(GFP)标记角膜基质细胞,示踪角膜基质构建过程。同时,对侧角膜仅行PGA移植,作为材料对照组。8周后取材,行组织学切片,Western blot检测Ⅰ型胶原及电镜下测定胶原纤维直径分布。结果术后8周,实验侧角膜逐渐恢复透明,形成新生角膜基质样组织,胶原与角膜表面平行,排列较整齐,组织学结构接近正常基质组织。实验组Western blot检测提示新生组织中基质细胞表达Ⅰ型胶原;电镜下胶原纤维直径[(29.0±4.7)nm]与正常角膜基质组织比较[(28.5±3.5)nm],差异无显著意义(P>0.05)。对照组正常角膜无新生基质组织形成。GFP标记角膜基质细胞,示踪角膜基质第8周时,荧光显微镜下可见新生组织呈绿色,提示GFP表达。结论 应用组织工程技术可以在兔受体角膜内构建角膜基质层组织。(中华眼科杂志,2004,40:517-521)     

Acellular ostrich corneal stroma used as scaffold for construction of tissue-engineered cornea

AIM: To assess acellular ostrich corneal matrix used as a scaffold to reconstruct a damaged cornea. METHODS: A hypertonic saline solution combined with a digestion method was used to decellularize the ostrich cornea. The microstructure of the acellular corneal matrix was observed by transmission electron microscopy (TEM) and hematoxylin and eosin (H&E) staining. The mechanical properties were detected by a rheometer and a tension machine. The acellular corneal matrix was also transplanted into a rabbit cornea and cytokeratin 3 was used to check the immune phenotype. RESULTS: The microstructure and mechanical properties of the ostrich cornea were well preserved after the decellularization process. In vitro, the methyl thiazolyl tetrazolium results revealed that extracts of the acellular ostrich corneas (AOCs) had no inhibitory effects on the proliferation of the corneal epithelial or endothelial cells or on the keratocytes. The rabbit lamellar keratoplasty showed that the transplanted AOCs were transparent and completely incorporated into the host cornea while corneal turbidity and graft dissolution occurred in the acellular porcine cornea (APC) transplantation. The phenotype of the reconstructed cornea was similar to a normal rabbit cornea with a high expression of cytokeratin 3 in the superficial epithelial cell layer. CONCLUSION: We first used AOCs as scaffolds to reconstruct damaged corneas. Compared with porcine corneas, the anatomical structures of ostrich corneas are closer to those of human corneas. In accordance with the principle that structure determines function, a xenograft lamellar keratoplasty also confirmed that the AOC transplantation generated a superior outcome compared to that of the APC graft.     

Pigment Epithelium-Derived Factor Peptide Promotes Corneal Nerve Regeneration: An In Vivo and In Vitro Study

PurposeTo investigate the potential of a pigment epithelium-derived factor (PEDF) peptide 44-mer to promote nerve regeneration in a rabbit corneal nerve injury model to demonstrate its neurotrophic ability in cultivated mouse trigeminal neuron cells.MethodsSubconjunctival or intrastromal injection of 44-mer on the cornea was performed in a rabbit model of corneal nerve injury created by corneal epithelial debridement. Immunocytochemical analysis (44-mer, anti-tubulin III, SMI312, CD11b, and α-SMA) and in vivo confocal microscopy were performed. Corneal sensation was estimated using a Cochet-Bonnet corneal esthesiometer. Primary cultivated mouse trigeminal neurons were used to examine the in vitro neurotrophic ability of 44-mer. The cellular morphology and the immunocytochemical staining with anti-tubulin III and SMI312 in different concentrations of 44-mer were compared, and a quantitative assessment of neurite outgrowth was performed.ResultsImmunohistochemical staining showed the retention of 44-mer in the corneal stroma for at least 7 days after a single dose of corneal intrastromal injection and promoted corneal nerve regeneration revealed by in vivo confocal microscopy. Corneal esthesiometer demonstrated gradual recovery of the corneal sensation in 44-mer-treated eyes with a lower corneal touch threshold than wounded vehicles and closer to baseline at 3 weeks after corneal injury (P < 0.001). In vitro studies showed a dose-dependent neurotrophic effect of 44-mer in cultivated trigeminal neuron cells.ConclusionsThe 44-mer showed in vivo and in vitro corneal neurotrophic abilities. Our results suggest that intrastromal injection of 44-mer into the corneal stroma may have a potential role in treating diseases related to corneal nerve damage.     

异种角膜基质材料的制备和体外细胞种植的实验研究

目的研究异种角膜基质生物支架材料的制备方法和体外种植兔角膜基质细胞后细胞在材料上的生长、增殖情况。方法将York猪全层角膜用去垢剂联合0．25％胰蛋白酶、DNA-RNA酶祛除猪角膜基质细胞并冻干制备成支架材料；将兔角膜组织块用胶原酶消化后，用含10％血清的DMEM培养液体外培养，并做波形丝蛋白，角蛋白免疫组织化学染色检测；将培养的兔角膜基质细胞的2～3代接种在材料上，培养5d后，做HE染色、扫描电镜观察。结果猪角膜基质片经脱细胞处理后，细胞成分祛除干净并保留了角膜组织的三维网格状结构，网状间隙明显增大，利于细胞生长；体外培养的兔角膜基质细胞波形丝蛋白染色为阳性、角蛋白染色为阴性；HE染色、扫描电镜结果显示兔角膜基质细胞在支架材料上生长、增殖良好。结论异源性角膜经祛脱细胞处理而获得的生物支架材料利于异种细胞的黏附和增殖，可进一步用于组织工程角膜的研究。     

猪脱细胞角膜基质组织结构特点与生物相容性研究

背景构建组织工程化角膜时,载体的选择十分重要。目前有多种载体可供选用,但脱细胞角膜基质是公认的较好载体。目的观察猪脱细胞角膜基质的组织结构特点,评价其与异种角膜基质和上皮细胞的生物相容性。方法取猪角膜组织进行组织块培养,经胰蛋白酶-EDTA酶消化角膜上皮、基质、内皮细胞,支架组织于-20℃冷冻干燥后灭菌保存。猪脱细胞角膜基质石蜡切片行常规苏木精一伊红染色,光学显微镜下观察组织的形态学特征;扫描电镜下观察其组织结构特点;并对其物理特性,如抗拉性、膨胀性、含水量和透明度进行评价。将猪脱细胞角膜基质移植到兔角膜基质层内,同时与体外培养的兔角膜上皮细胞共培养4周,分析其组织和细胞生物相容性。结果经酶消化处理后猪角膜组织中未见上皮、基质和内皮细胞,其胶原纤维直径大小、排列与正常角膜组织相同,抗拉性、膨胀性、含水量和透明度等物理特性与正常猪角膜相似。猪脱细胞角膜基质行异种兔角膜基质层间移植1周时可见轻度水肿,2周后水肿基本消退,4周时透明度较好。猪脱细胞角膜基质与兔角膜基质之间贴附良好,未见炎症反应及新生血管。兔角膜上皮细胞接种于猪脱细胞角膜基质上共培养4周后CK3表达阳性。猪脱细胞角膜基质脱水前与脱水2h、4h后及正常猪角膜基质间的抗拉性、膨胀性、含水量的差异均无统计学意义（P〉0．05）,但脱水2h、4h后及正常猪角膜基质的透明度明显好于脱水前,差异均有统计学意义（P〈0．01）。结论猪脱细胞角膜基质组织结构与正常猪角膜相似,与兔角膜基质和上皮细胞具有良好的生物相容性。     

纤维蛋白胶对眼表的作用

目的观察以纤维蛋白胶（FG）为载体构建兔角膜上皮、基质和内皮细胞片,以及FG对兔结膜和角膜的黏合作用。方法在培养板孔底制作薄层和厚层FG,将培养兔角膜3种细胞分别接种于FG表面,观察细胞生长情况。FG对兔结膜的黏合研究：分为A组（结膜原位粘合组）,B组（结膜移位粘合组）,对照组（单纯切除结膜植片）,每组5只眼,观察结膜组织黏合情况。FG对兔角膜的黏合研究：3例兔前板层角膜移植术,先用10—0尼龙线间断缝合4针固定植片,再用FG黏合,将植片固定于植床。结果角膜3种细胞在薄层和厚层FG表面生长良好：角膜上皮细胞可形成单层和复层;角膜基质细胞间网状连接;角膜内皮细胞排列紧密。对兔结膜的黏合研究：A组和B组植片与植床对位良好,紧密黏合。组织切片显示术后第4周A组和B组结膜上皮完整,炎症基本消退。对照组结膜上皮有局部脱落区,纤维层局部显示瘢痕组织结构特征。兔前板层角膜移植术后3个月,植片与受体角膜愈合良好。结论FG可作为角膜3种细胞的生长载体构建细胞片。FG对兔结膜和角膜组织有良好的黏合作用。     

Rabbit cornea microstructure response to changes in intraocular pressure visualized by using nonlinear optical microscopy

PURPOSE: To characterize the microstructural response of the rabbit cornea to changes in intraocular pressure (IOP) by using nonlinear optical microscopy (NLOM). METHODS: Isolated rabbit corneas were mounted on an artificial anterior chamber in series with a manometer and were hydrostatically pressurized by a reservoir. The chamber was mounted on an upright microscope stage of a custom-built NLOM system for corneal imaging without using exogenous stains or dyes. Second harmonic generation in collagen was used to image through the full thickness of the central corneal stroma at IOPs between 5 and 20 mm Hg. Microstructural morphology changes as a function of IOP were used to characterize the depth-dependent response of the central cornea. RESULTS: Regional collagen lamellae architecture through the full thickness of the stroma was specifically imaged as a function of IOP. Hypotensive corneas showed gaps between lamellar structures that decreased in size with increasing IOP. These morphologic features appear to result from interwoven lamellae oriented along the anterior-posterior axis and parallel to the cornea surface. They appear throughout the full thickness and disappear with tension in the anterior but persist in the posterior central cornea, even at hypertensive IOP. CONCLUSIONS: NLOM reveals interwoven collagen lamellae sheets through the full thickness of the rabbit central cornea oriented along the anterior-posterior axis and parallel to the surface. The nondestructive nature of NLOM allows 3-dimensional imaging of stromal architecture as a function of IOP in situ. Collagen morphologic features were used as an indirect measure of depth-dependent mechanical response to changes in IOP.     

Innervation of tissue-engineered corneal implants in a porcine model: a 1-year in vivo confocal microscopy study

PURPOSE: To examine the pattern of nerve regeneration within tissue-engineered corneal substitutes grafted into host porcine corneas over a 1-year postoperative period. METHODS: Biodegradable corneal substitutes from cross-linked collagen were implanted into the left eyes of 12 pigs by deep lamellar keratoplasty. Regeneration of severed nerves into the central implant region was investigated with in vivo confocal microscopy. Both implant-recipient and control (right) eyes were examined before surgery and 2, 6, 10, and 12 months after surgery, to quantify the number, density, diameter, and branching of nerve fiber bundles at various corneal depths. Transmission electron microscopy was used to confirm the presence of nerve bundles. RESULTS: Two months after surgery, corneal nerve ingrowth was observed within the deep anterior stroma, with a number and density of regenerated nerves significantly higher than in nonsurgical control eyes (P < 0.01). Nerves within the superficial anterior stroma regenerated by 6 to 10 months after surgery, and the first subbasal epithelial nerves were seen 10 months after surgery. After 1 year, subbasal nerve density recovered to preoperative levels. Nerve fibers in the deep anterior stroma remained significantly thinner relative to control eyes after 1 year (P < 0.001), where both superficial anterior and subbasal nerve diameter did not change relative to control eyes. CONCLUSIONS: The pattern of reinnervation within tissue-engineered corneal substitutes has been quantified in vivo. Innervation proceeded rapidly in the deep anterior stroma, followed by repopulation of more superficial regions. One year after surgery, nerve density within the tissue-engineered cornea increased or remained unchanged relative to controls in all corneal regions examined.