Effect of donor epithelium on corneal transplant survival

Two hundred thirty-two penetrating keratoplasties in 228 eyes were performed with or without the removal of donor corneal epithelium in a prospective, randomized clinical trial to determine the effect of epithelial removal on graft survival. The removal of epithelium did not reduce the likelihood of graft failure, irreversible allograft reaction, or reversible allograft reaction.     

不同移植手术治疗角膜缘干细胞缺损的实验研究

目的探讨以人羊膜为载体培养的角膜缘干细胞，自体及异体移植治疗全角膜缘干细胞缺损。方法制作兔眼角膜缘干细胞完全缺损3个月的模型。实验动物随机分为自体移植组和异体移植组，前者取对侧眼角膜缘组织，后者取异体兔眼角膜缘组织，均以去除上皮细胞的羊膜基底膜为载体，培养12d后行角膜缘干细胞羊膜移植术。术后观察3个月，以角膜上皮染色、角膜浑浊和新生血管3项指标进行临床疗效评定，通过病理检查评估术后角膜上皮修复情况，印迹细胞学检查移植前后角膜上皮的细胞表型。结果体外培养的兔角膜缘干细胞可在羊膜上粘附生长并增生，体外培养12d可形成复层。自体移植组和部分异体移植组术后角膜上皮逐渐愈合，透明度提高，基质细胞浸润减轻，新生血管减退或消失。印迹细胞学检查显示：移植前角膜上皮细胞PAS阳性，而移植后转为阴性；组织病理学显示：移植前角膜上皮大部分缺损，移植后呈现角膜上皮结构。部分异体移植组术后出现了免疫排斥反应。结论兔自体角膜缘干细胞羊膜移植术可重建眼表；免疫排斥反应仍是异体角膜缘干细胞羊膜移植术失败的主要原因。     

羊膜培养兔角膜缘上皮细胞及自体移植--角膜缘干细胞缺损的治疗

目的　探讨以人羊膜为载体培养兔角膜缘上皮细胞及其自体移植治疗全角膜缘干细胞缺损。方法　在8只兔右眼用正庚醇脱上皮和角膜缘环切的方法构建全角膜缘干细胞缺损模型2月。其中6只兔为实验组,活体取左眼角膜缘浅层小块,置羊膜上常规和气_液培养42天后进行自体移植治疗右眼角膜缘干细胞缺损;2只兔为对照组,直接用解冻无细胞人羊膜移植治疗右眼角膜缘干细胞缺损。进行细胞和术眼活体观察、组织学观察和电镜观察。结果　角膜缘上皮细胞在羊膜上生长良好,形成复层,细胞间的联结结构存在,细胞与羊膜组织粘附牢固。实验组移植手术后角膜迅速上皮化,恢复角膜表面光滑和透明,组织学观察和电镜观察呈现生理角膜上皮层的结构特点。但眼睑闭合不全可导致手术失败。对照组术后出现角膜缘干细胞缺损导致的角膜病变。结论　以羊膜为载体培养角膜缘上皮细胞后自体移植可有效地治疗角膜缘干细胞缺损导致的角膜病变。     

角膜缘干细胞的研究

角膜缘干细胞是位于角膜缘基底上皮层底的一类特殊类型的上皮细胞,随着细胞培养技术的发展,角膜缘干细胞体外培养后移植用于治疗由于角膜缘干细胞缺乏或者功能不全引起的眼表疾病成为研究的热点。本文就其解剖学定位、生物学特性、组织工程化角膜的基础性研究及其临床应用做一综述。     

Th2-biased immune system promotion of allogeneic corneal epithelial cell survival after orthotopic limbal transplantation

PURPOSE: The Th2-biased immune system can promote penetrating keratoplasty survival in mice. A series of experiments were performed to determine whether this system could prolong corneal limbal transplant (LT) survival. METHODS: BALB/c (H-2d) mice were immunized with 50 microg of keyhole limpet hemocyanin (KLH) in incomplete Freud's adjuvant. Four weeks later, the corneal epithelium, including the limbal area, was removed, and the mice received LT from B10.D2 (H-2d), C57BL/10 (H-2b), or enhanced green fluorescence protein (EGFP) transgenic (H-2b) donor mice. Immediately thereafter, recipient mice were immunized with 50 micro g of KLH or Hanks' balanced salt solution (HBSS; control) in complete Freund's adjuvant. The allograft fates were assessed clinically. Lymphocytes of recipients were examined for donor-specific proliferation and for donor-specific cytokine production in vitro. RESULT: The regenerated epithelia of all C57BL/10 (n=14) and B10.D2 (n=18) grafts were rejected swiftly in control mice, whereas 66.6% of C57BL/10 grafts (8/12, P<0.001) and 62.8% of B10.D2 grafts (22/35, P<0.001) in the KLH immune group remained significantly clear for 8 weeks. Moreover, EGFP donor epithelial cells were detected from the healthy corneas of KLH-immunized mice. As for the in vitro assay, at 1 week after B10.D2 grafting, lymphocytes from KLH-immunized groups showed neither proliferation nor increased cytokine secretion. CONCLUSIONS: The Th2-biased immune system can support LT prolongation irrespective of donor disparity and can suppress corneal neovascularization. This prolongation is not due to induction of donor-specific regulatory cells, but is presumably at least associated with the suppression of allosensitization.     

Comparison of limbal and peripheral human corneal epithelium in tissue culture

Peripheral human corneal epithelium grows better in tissue culture than central epithelium, but it is not known whether ocular limbal epithelium grows even better than does the peripheral corneal epithelium. In this work we compared the growth kinetics of limbal and peripheral human corneal epithelial cells in tissue culture. Four 1-2 mm2 explants, removed from the limbus or from peripheral cornea (1-2 mm inside the limbus) of eye bank eyes, were grown to confluence in primary culture. Cells were then passaged at 2 X 10(5) cells per dish. At intervals thereafter, the cells were counted in a hemocytometer to determine plating efficiency and growth curves. Mitotic activity was determined 4 days after passaging by labeling cultures with 3H-thymidine and counting aliquots using the hemocytometer and scintillation counter. In the primary cultures, limbal epithelium grew as small, uniformly polygonal cells. Peripheral corneal cells grew to a variety sizes. The 24 hr plating efficiency and doubling time of limbal epithelial cells were 47 +/- 8% and 80 +/- 14 hr, respectively, while those of peripheral corneal cells were 41 +/- 10% (P less than 0.1) and 131 +/- 25 hr (P less than 0.001). The mitotic activity of limbal cells was significantly higher than that of peripheral (2.9 +/- 1.2 vs. 0.8 +/- 0.6) (P less than 0.01). These results indicate that human ocular limbal epithelium grows better in culture than does peripheral human corneal epithelium.     

In vivo survival and stratification of cultured limbal epithelium

A 6-year-old Bangladeshi girl presented with total limbal stem cell deficiency in the left eye, secondary to a 6-month-old chemical injury. The patient had also previously undergone two limbal transplantation surgeries. At the authors' centre the child underwent autologous cultured limbal epithelium transplantation, on human amniotic membrane, without the use of air-lift technique. Symptomatic relief, re-epithelialization of the ocular surface, regression of corneal pannus and slight improvement in vision were all noted. The corneal button obtained at the time of keratoplasty (performed 4 months later) revealed stratified epithelium with basement membrane. Thirty-seven months post keratoplasty, the best-corrected visual acuity was 6/15 with clear graft and stable ocular surface. Herein, a case of limbal stem cell deficiency successfully managed by monolayer of cultured limbal epithelium is presented.     

组织工程上皮移植对碱烧伤角膜新生血管的影响

目的：评价组织工程上皮移植在碱烧伤角膜缘干细胞缺乏症中对角膜新生血管的抑制作用。

方法：回顾性非随机的病例研究。2006/2011年我院收治的19例(23眼)完全性角膜缘干细胞缺乏症的碱烧伤患者, 10例13眼行组织工程上皮移植,9例10眼行羊膜移植。所有患者在手术前后均用裂隙灯观察角膜新生血管情况,在术后第21,60d对角膜新生血管进行评分比较。

结果：术后第21d和术后第60d组织工程上皮移植组和羊膜移植组角膜新生血管均较术前明显减少( P<0.05),在术后两个评价时间点,组织工程上皮移植组平均角膜新生血管分数明显低于羊膜移植组。

结论：对碱烧伤所致角膜缘干细胞缺乏的患者,组织工程上皮移植抑制角膜新生血管的作用明显好于羊膜移植。     

Long-term results of allogeneic penetrating limbo-keratoplasty in total limbal stem cell deficiency

OBJECTIVE: To determine the prognosis of allogeneic penetrating limbo-keratoplasty in patients with total limbal stem cell deficiency and to find out if donor limbal stem cells survive in the long run. DESIGN: Noncomparative prospective case series. PARTICIPANTS: Forty-eight patients with total limbal stem cell deficiency. INTERVENTION: Allogeneic penetrating limbo-keratoplasty. All patients received systemic cyclosporin A and/or mycophenolate mofetil in the postoperative course. Thirteen patients received grafts with 0 to 1 HLA mismatches in the HLA-A, HLA-B, and HLA-DR loci; 13 patients received grafts with 2 to 6 mismatches; and 22 patients received untyped grafts. MAIN OUTCOME MEASURES: Long-term clear graft survival and survival of donor limbal stem cells. RESULTS: Five years postoperatively, 65% of the grafts with 0 to 1 mismatches, 41% of the grafts with 2 to 6 mismatches, and 14% of the untyped grafts were clear centrally (estimation according to Kaplan-Meier log rank test, P = 0.03). Immunogenetic analysis of epithelial cells from the surface of the graft could be performed successfully in 7 of 9 patients and revealed donor DNA in the epithelium of 5 of these 7 patients up to 56 months postoperatively. CONCLUSIONS: Long-term survival of donor epithelium could be demonstrated immunogenetically in patients undergoing allogeneic penetrating limbo-keratoplasty. Human leukocyte antigen-matched grafts seem to deliver better results than untyped grafts. Progress with matching and immunosuppressive strategies may further improve current results.     

Proliferation of the vascular endothelium of the iris following total debridement of the corneal epithelium and limbal excision of rabbits

BACKGROUND: Damage to the corneal epithelium causes not only a reaction for its repair but also affects other parts of the cornea as well as different components of the anterior segment of the eye. The purpose of this investigation was to analyze the consequences, following epithelial and limbal damage, to the iris of rabbits (Oryctolagus cuniculus). METHODS: The corneal epithelium was thoroughly scraped followed by surgical excision of the limbus. Next, (3)H-thymidine ((3)H-TdR) was injected intravitreally both into the right (experimental) and left (control) eyes which had their anterior segments processed for autoradiography at intervals of 2, 7 and 21 days after surgery (three rabbits per interval). The irises were also examined with scanning-electron and confocal microscopy after Evans blue injection. RESULTS: There was a high frequency of labeling in the cells of the iris blood vessels in the experimental eye, particularly the endothelial ones. The ratio of labeled cells between experimental and control irises was 40:1, with a population of nuclei increasing by 25% and remaining labeled up to 21 days. There was also an increase in the volume of the iris vasculature as shown by confocal microscopy. The high labeling frequencies of the vascular cells were observed throughout the iris from the ciliary to the pupillary regions. CONCLUSIONS: The lesions on the corneal epithelium elicit proliferation of the iris vascular cells, mainly its endothelium, as well as an early breakdown of the blood-aqueous barrier. The daughter cells resulting from the damage to the eye surface were detected up to 21 days after a single injection of (3)H-TdR, most likely due to their slow turnover. As a consequence of this proliferation, the vasculature of the iris increased in volume.     

Long-term survival of cryopreserved corneal endothelium

Corneas of five patients who received cryopreserved penetrating grafts 15 years previously were evaluated by regional specular microscopy and computer-assisted morphometric analysis. This technique quantitates changes in cell size and shape as well as cell number. Comparisons were made with five eyes in four patients 15 years after penetrating keratoplasty utilizing fresh grafts. In three patients, fresh and frozen tissue were transplanted in the same host. These examinations showed no difference in structure or function comparing cryopreserved tissue with fresh donor tissue.     

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.     

Penetrating limbo-keratoplasty for granular and lattice corneal dystrophy: survival of donor limbal stem cells and intermediate-term clinical results

PURPOSE: To assess clinical follow-up data, and to identify donor epithelial cells after homologous penetrating central limbo-keratoplasty in patients with granular and lattice corneal dystrophies compared with patients who underwent conventional penetrating keratoplasty (PK). DESIGN: Mixed retrospective and prospective nonrandomized comparative case series. PARTICIPANTS AND CONTROLS: Twenty-six patients who underwent 33 limbo-keratoplasty procedures for granular or lattice corneal dystrophy since May 1995 and a historical control group of 24 patients who underwent 36 PK procedures between November 1986 and May 1995. METHODS: Postoperatively, all but 2 limbo-keratoplasty patients were treated with systemic immunosuppressants for 6 months. All patients received long-term topical immune prophylaxis with prednisolone-21-acetate 1% (2 drops per day). After obtaining informed consent, epithelial cells were harvested from 10 limbo-keratoplasty eyes of 8 patients with granular dystrophy and 7 limbo-keratoplasty eyes of 7 patients with lattice dystrophy. Conjunctival epithelium or buccal mucosal epithelium for recipient identification and corneal epithelial cells from 3 graft sites were harvested. Deep-frozen donor corneoscleral rims were analyzed to characterize donor features. Genetic analysis was performed by polymerase chain reaction of short tandem repeat (STR) loci. MAIN OUTCOME MEASURES: The ratio of dystrophy recurrences in the graft was clinically assessed. Donor features in epithelial cells were genetically established if at least 1 STR profile differed from that of the recipient. RESULTS: There were 5 recurrences in limbo-keratoplasty eyes with granular dystrophy and 2 recurrences in limbo-keratoplasty eyes with lattice dystrophy, compared with 15 and 6 recurrences in PK eyes, respectively. The differences between limbo-keratoplasty and PK were not statistically significant over time (log-rank test; P = 0.14 for granular dystrophy and P = 0.56 for lattice dystrophy; alpha error, 0.05). For genetic analysis, 12 of 17 samples were evaluated. Donor epithelial cells were detected in 5 of the 12 samples (42%). CONCLUSIONS: Limbo-keratoplasty tended to be associated with fewer recurrences of granular and lattice dystrophies. However, the difference was not yet statistically significant, probably due to the disappearance of the transplanted limbal stem cells over time. Genetic analysis confirmed the survival of transplanted limbal stem cells over several years in some limbo-keratoplasty eyes, which might correlate with less recurrence. Limbo-keratoplasty, therefore, is likely to represent a first step towards long-term recurrence-free survival of corneal grafts in patients with granular and lattice dystrophies.     

Actin organization in migrating corneal epithelium of rabbits in situ

We have found previously that fibronectin enhances the migration of rabbit corneal epithelium both in vitro and in vivo. In this paper we report a change of actin localization in migrating corneal epithelium as determined by immunofluorescent microscopy. Rabbit cornea was cut into small blocks and cultured in TC-199 medium. In the normal cornea, actin was detected as diffuse fluorescence at each epithelial layer. After 8 hr of cultivation epithelial cells had not started to migrate significantly, but actin had accumulated at the cell membrane. After 24 hr, epithelial migration had begun, and actin-specific fluorescence was detected mainly in the basal cell layer at the leading edge. When fibronectin or epidermal growth factor was added to the culture medium, epithelial migration began 8 hr after initiation of culture, and at 24 hr actin-specific fluorescence at the basal side of the migrating epithelial cells appeared stronger than that of a control group cultured in TC-199 unsupplemented medium. At the same time, fibronectin-specific fluorescence was more intense beneath the migrating epithelial cells. It is known that fibronectin has an affinity to collagen, and thus it might coat the cut surface of the stroma. Epithelial cells may attach then to the stroma via coated fibronectin. When a large quantity of exogenous fibronectin is added or when fibronectin is synthesized by the addition of epidermal growth factor, it may further stimulate the organization of intracellular actin from globular form (G-actin) to fibrilar form (F-actin). As a result, the change of intracellular localization and appearance of organized actin molecule might lead to cellular migration.