Corneal Stem Cell Deficiency Research Articles

Palladium-103 plaque therapy for multifocal iris melanoma: Radiation of the entire anterior segment of the eye.

Purpose:To investigate the safety and tolerability of total anterior segment palladium-103 (103Pd) eye plaque brachytherapy for multifocal iris melanoma.Methods:Interventional case series of 11 patients with multifocal iris melanomas. Anterior segment ultrasound revealed tumor size, location, and intraocular margins. Epicorneal amniotic membrane grafts protected the cornea and decreased pain during total anterior segment 103-Pd ophthalmic plaque brachytherapy.Results:Eleven diffuse iris melanomas were American Joint Committee on Cancer 8th edition–classified as T1 (n = 5, 45.5%) and T2 (n = 6, 54.5%). Plaque radiation was completed to a minimum mean tumor dose of 85 Gy (mean dose rate, 58.1 cGy/h). Ultrasonographic tumor thickness regression was 41% (follow up mean 58.7, median 50, range: 8–139 months). Despite 100% local control and 100% eye retention, one patient (9.1%) developed metastatic disease. Four eyes required cataract surgery. There was no corneal stem-cell deficiency, corneal opacity, radiation maculopathy, or optic neuropathy. While visual acuity prior to treatment was 20/40 or better in 10 (91%), 9 were 20/40 or better (81.9%) at last follow-up. Four (36%) had glaucoma prior to treatment and three eyes developed glaucoma after treatment for a total of 63%.Conclusion:Total anterior segment (103Pd) plaque brachytherapy resulted in local control, good visual acuity, eye and life preservation in the treatment of multifocal iris melanoma.

The Limbal Epithelial Progenitors in the Limbal Niche Environment.

Limbal epithelial progenitors are stem cells located in limbal palisades of vogt. In this review, we present the audience with recent evidence that limbal epithelial progenitors may be a powerful stem cell resource for the cure of human corneal stem cell deficiency. Further understanding of their mechanism may shed lights to the future successful application of stem cell therapy not only to the eye tissue, but also to the other tissues in the human body.

Corneal Goblet Cells and Their Niche: Implications for Corneal Stem Cell Deficiency

Goblet cells are terminally differentiated cells secreting mucins and antibacterial peptides that play an important role in maintaining the health of the cornea. In corneal stem cell deficiency, the progenitor cells giving rise to goblet cells on the cornea are presumed to arise from differentiation of cells that migrate onto the cornea from the neighboring conjunctiva. This occurs in response to the inability of corneal epithelial progenitor cells at the limbus to maintain an intact corneal epithelium. This study characterizes clusters of cells we refer to as compound niches at the limbal:corneal border in the unwounded mouse. Compound niches are identified by high expression of simple epithelial keratin 8 (K8) and 19 (K19). They contain variable numbers of cells in one of several differentiation states: slow-cycling corneal progenitor cells, proliferating cells, nonproliferating cells, and postmitotic differentiated K12+Muc5ac+ goblet cells. Expression of K12 differentiates these goblet cells from those in the conjunctival epithelium and suggests that corneal epithelial progenitor cells give rise to both corneal epithelial and goblet cells. After wounds that remove corneal epithelial cells near the limbus, compound niches migrate from the limbal:corneal border onto the cornea where K8+ cells proliferate and goblet cells increase in number. By contrast, no migration of goblet cells from the bulbar conjunctiva onto the cornea is observed. This study is the first description of compound niches and corneal goblet cells and demonstration of a role for these cells in the pathology typically associated with corneal stem cell deficiency.

A comparative study on rabbit bone mesenchymal stem cells and human amniotic epithelial cells transplantation for rabbit limbal stem cell deficiency

Background Limbal stem cell deficiency usually leads to blindness, and traditional therapy is limited. Recent research demonstrated that bone mesenchymal stem cells ( BMSCs ) and human amniotic epithelial cells(AECs) could differentiate into many kinds of cells including corneal epithelial cells, but the outcome and effect of these cells on corneal stem cell deficiency are still unclear. Objective This study aimed to observe and compare the effects of rabbit BMSCs and human AECs transplantation for rabbit limbal stem cell deficiency. Methods Eighteen clean New Zealand rabbits were randomly divided into the amniotic stroma(AS) group, rabbit BMSCs group and human AECs group with 6 rabbits for each group. Limbal stem cell deficiency models were established by putting a piece of filter paper that had been soaked in a NaOH solution at the corneal center. Rabbit BMSCs were isolated and purified by density gradient centrifugation combined with the attachment culture method, and human AECs were collected by a sequential trypsin digestion technique,and the third generation rabbit BMSCs and the first generation human AECs were identified with RT-PCR. After that,cells were inoculated onto the denuded AS and grafted to the corneal surface of the experimental animals. Twenty-eight days after cell transplantation, the therapeutic effects were evaluated based on the corneal neovascularization and opacity scores. Corneal histopathological examination and immunohistochemistry were performed to evaluate and compare the effectiveness among AS,rabbit BMSCs and human AECs on corneal stem cell deficiency. The procedure complied with the Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission. Results The third generation of rabbit BMSCs grew well after 12 hours, and the first generation of human AECs formed a membrane-like monolayer after 48 hours of incubation on AS. Immunohistochemistry staining showed that, 28 days after transplantation, the surface cells of the cornea were positive for cytokeratin 3 in both the rabbit BMSCs group and human AECs group.Compared with the AS group,the corneal neovascularization and opacity grades were significantly decreased in the rabbit BMSCs group( Z=-2. 983, P =0. 003 ; Z =-2. 844, P =0. 004 ) and human AECs group ( Z =-2. 817, P =0. 005 ; Z =-2.041, P =0. 041 ). Histopathological analysis exhibited that stratified corneal epithelial-like cells formed on the corneal stroms 28 days after grafting and no signs of goblet cells and neovascularization were found. Less inflammatory cells and regular collagen fiber could be seen in the rabbit BMSCs group and human AECs group. In addition,clinical observation also revealed that the corneas were much clearer in the rabbit BMSCs group than the human A ECs group( Z =-2. 091 , P=0. 037 ), but the corneal neovascularization score was similar between them (Z = -0. 267,P=-0. 789). Conclusions Rabbit BMSCs and human AECs can differentiate into corneal epithelial-like cells on the damaged corneal surface and further demonstrate remarkable inhibitory effects on corneal neovascularization and inflammatory cells. The more dominant and prominent effect is the role played by rabbit BMSCs in the improvement of corneal transparency. Key words: Bone mesenchymal stem cell; Amniotic epithelial cell; Limbal stem cell; Corneal neovascularization; Stem cell transplantation

Transplantation of Ex Vivo Cultured Limbal Epithelial Stem Cells: A Review of Techniques and Clinical Results

Ex vivo cultured limbal epithelial stem cells have been used successfully to treat corneal limbal stem cell deficiency. We identified 17 reports of the application of this novel cell-based therapy in humans. In addition we identified four reports of the use of culture oral mucosal epithelial cells to treat limbal stem cell deficiency. We examined these reports to discern the success rate, complication rate, visual outcome, whether there is an optimal technique and which patients are the most likely to benefit. We also discuss the different culture methods employed and the regulations governing cell banks that are providing this service. We found that the techniques used to cultivate and transplant cells varied, but that no individual method was clearly superior. The reported success rate is similar across all studies for both allografts and autografts. The clinical indications for this treatment are not clearly defined as indicated by the variety of disorders treated. Follow-up is limited and the long-term success rate is yet to be established. Nonetheless, we conclude that there is sufficient evidence to support the continued use and refinement of this procedure as a treatment for corneal stem cell deficiency.

Amnios et problèmes de surface oculaire

The amniotic membrane, the most internal placental membrane, has various properties useful in ophthalmology. Collected on delivery by elective Caesarean section, the amnion is prepared under sterile conditions, and, usually, cryopreserved until its use as a biological bandage or as a substrate for epithelial growth in the management of various ocular surface conditions. Specifically, the amnion is used to : (1) limit formation of adhesive bands between eyelids and eyeball (symblepharon) or the progression of a fibrovascular outgrowth towards the cornea (pterygium) or to (2) facilitate the healing of corneal ulcers, bullous keratopathy, and corneal stem cell deficiency. In this last condition, either hereditary or acquired after a thermal or a chemical burn, corneal stem cells, located at a transitional zone between the cornea and conjunctiva, are lost. These cells are essential for renewal of corneal epithelium in normal and in diseased states. The loss of these cells leaves the corneal surface free for invasion by conjunctival epithelium. Not only, does conjunctival epithelium support the development of vascularisation on the normally avascular cornea, but some conjunctival cells differentiate into mucus secreting goblet cells. Such a change in phenotype leads to loss of corneal transparency and visual disability. The removal of this fibro-vascular outgrowth in combination with transplantation of both amniotic membrane and corneal stem cells are used to treat this condition. The amnion stimulates the proliferation of less differentiated cells which have the potential to reconstruct the cornea. This potential is at the origin of the hypothesis that the amnion may provide an alternative niche for limbal stem cells of the corneal epithelium. It abounds in cytokines and has antalgic, anti-bacterial, anti-inflammatory and anti-immunogenic properties, in addition to allowing, like fetal skin does, wound healing with minimal scar formation. These desirable properties are responsible for the increasing use of amniotic membrane in ophthalmology. The complete understanding of the mechanisms of action of amniotic membrane for ocular surface diseases has yet to be understood. Once revealed by research, they may provide new pharmacological avenues to treat ocular surface diseases.

Current Concepts and Challenges in Ocular Surface Reconstruction Using Cultivated Mucosal Epithelial Transplantation

Ocular surface disorders wherein corneal stem cells are deficient result in total conjunctivalization leading to severe visual dysfunction and blindness. Treatment of these diseases requires reconstruction of the ocular surface using epithelial transplantation to provide a smooth refractive corneal surface and biologic and physical barriers against a variety of destructive factors. Recently, regenerative medicine focusing on tissue-engineered techniques has been developed and established as a new clinical field. In particular, cultivated mucosal epithelial transplantation using well-differentiated, stratified epithelial sheets on amniotic membrane allows a rapid re-epithelial cover over the entire corneal surface, resulting in early reduction of inflammation and cicatrization. This surgical approach dramatically improves the prognosis of severe ocular surface diseases, especially severely inflamed corneal stem cell deficiency. This new approach not only provides early epithelialization but also allows reconstruction of the corneal surface using autologous cultivated epithelium including the cornea and oral mucosa from a small number of cell sources after amplification. Tissue-engineered strategies using autologous corneal or oral mucosal epithelial sheet transplantation avoid the risk of rejection and complications associated with immunosuppressive treatments. In addition to new cellular transplantation, combined automated lamellar therapeutic keratoplasty provides better refractive stromal interference and contributes to performance and safety of cataract surgery in severe corneal opacity cases. Although long-term prognosis and cell biologic behavior of tissue-engineered epithelium after transplantation should be carefully monitored, these recent surgical treatments have opened a new field for ocular surface reconstruction.

Sutureless Transplantation of Autologous Oral Mucosa Epithelial Cells in Corneal Reconstruction

New England Journal of Medicine Corneal Reconstruction With Tissue-Engineered Cell Sheets Composed of Autologous Oral Mucosal Epithelium: A New Approach to Ocular Surface Reconstruction in Bilateral Limbal Stem Cell Deficiency Kohji Nishida, MD, PhD; Masayuki Yamato, PhD; Yasutaka Hayashida, MD; Katsuhiko Watanabe, MSc; Kazuaki Yamamoto, MSc; Eijiro Adachi, MD, PhD; Shigeru Nagai, MSc; Akihiko Kikuchi, PhD; Naoyuki Maeda, MD, PhD; Hitoshi Watanabe, MD, PhD; Teruo Okano, PhD; Yasuo Tano, MD, PhD Background: Ocular trauma or disease may lead to severe corneal opacification and, consequently, severe loss of vision as a result of complete loss of corneal epithelial stem cells. Transplantation of autologous corneal stem-cell sources is an alternative to allograft transplantation and does not require immunosuppression, but it is not possible in many cases in which bilateral disease produces total corneal stem-cell deficiency in both eyes. We studied the use of autologous oral mucosal epithelial cells as a source of cells for the reconstruction of the corneal surface. Methods: We harvested 3-by-3-mm specimens of oral mucosal tissue from four patients with bilateral total corneal stem-cell deficiencies. Tissue-engineered epithelial-cell sheets were fabricated ex vivo by culturing harvested cells for two weeks on temperature-responsive cell-culture surfaces with 3T3 feeder cells that had been treated with mitomycin C. After conjunctival fibrovascular tissue had been surgically removed from the ocular surface, sheets of cultured autologous cells that had been harvested with a simple reduced-temperature treatment were transplanted directly to the denuded corneal surfaces (one eye of each patient) without sutures. Results: Complete reepithelialization of the corneal surfaces occurred within one week in all four treated eyes. Corneal transparency was restored and postoperative visual acuity improved remarkably in all four eyes. During a mean follow-up period of 14 months, all corneal surfaces remained transparent. There were no complications. Conclusions: Sutureless transplantation of carrier-free cell sheets composed of autologous oral mucosal epithelial cells may be used to reconstruct corneal surfaces and can restore vision in patients with bilateral severe disorders of the ocular surface. N Engl J Med. 2004;351:1187-1196.

Impression Cytology-proven Corneal Stem Cell Deficiency in Patients After Surgeries Involving the Limbus

To report three cases of limbal stem cell deficiency (confirmed by impression cytology) that followed multiple pterygium surgeries and therapeutic penetrating keratoplasty. The first case, after multiple pterygium surgeries, presented with corneal scarring and thickened epithelium with vascularization sparing the central cornea in the right eye and involving the entire cornea in the left eye. The second case presented with superficial scarring and extensive vascularization after failed therapeutic graft performed for a large perforated corneal ulcer. The third case was a clear graft performed for a progressing fungal ulcer with signs of conjunctivalization inferotemporally. Limbal stem cell deficiency was clinically suspected in all of these cases. Goblet cells with mucin globules were found on the corneal surface by impression cytology in all three cases. We report three cases of limbal stem cell deficiency (proven by impression cytology) that followed multiple pterygium surgeries and therapeutic penetrating keratoplasty. Surgical insult to the limbus is the predisposing factor for stem cell damage in these cases. Involvement of the limbus by infection and use of intensive medications are probable contributing factors for stem cell damage in cases of therapeutic penetrating keratoplasty.

Further evaluation of amniotic membrane banking for transplantation in ocular surface diseases.

Objective: To define the best conditions for amniotic membrane preparation, storage and banking in its use for corneal reconstruction. Methods: Amniotic membrane pieces were prepared under sterile conditions from placentas selected on the basis of donor medical and social history, serology, microbiological tests and histology. The pieces were kept at -140 degrees C but before grafting they were thawed and stored at 4 degrees C in RPMI medium, to have a preparation usable within 72 h. This procedure was validated by testing its therapeutic effectiveness in 25 patients 13 of which had corneal ulcers of various origin, 3 had sequelae of herpes simplex keratitis, 3 band keratopathy and 6 corneal stem cell deficiency due to chemical or thermal burns. Results: The preparation showed appreciable anti-inflammatory and analgesic effects. In the absence of corneal stem cell deficiency a stable re-epithelialisation was achieved in 15 out of 19 patients. When the limbus was lesioned, the amniotic membrane decreased vascularization and increased the number of corneal epithelial cells only in 1 of the 6 patients. No adverse reactions attributable to the tissue were recorded. Conclusions: A ready-to-use amniotic membrane preparation stored at 4 degrees C after cryopreservation has been tested in corneal reconstruction. Like the amniotic membrane thawed immediately before grafting, this preparation displayed full therapeutic effect in epithelial defects with stromal ulceration but without severe limbal stem cell deficiency. In two years banking activity 463 pieces of the preparation were successfully distributed to 90 Italian hospitals.

Autologous limbal transplantation in patients with unilateral corneal stem cell deficiency

AIMTo describe a surgical technique for autologous limbal stem cell transplantation and the outcome of a series of patients with unilateral stem cell deficiency.METHODSA report of six consecutive patients who...