Aims: To investigate the site of barrier function to the passive diffusion of a small molecule (phalloidin) in the corneal epithelium in the mouse. Methods: Penetration of phalloidin (molecular ...weight 1115 daltons) into the cornea was evaluated by studying fluorescent binding of phalloidin to actin in tissue sections, in whole mount preparations, and in the fixed intact globe by confocal microscopy. In addition, the location of tight junction proteins in the individual layers of the corneal epithelium was determined by immunohistochemistry. Results: Phalloidin staining of corneal sections was positive in all corneal layers in tissue sections and in all layers of the corneal epithelium except the suprabasal layer in excised fixed whole mounts of the cornea. However, when phalloidin staining was attempted in intact fixed globes, before excision of the cornea for whole mount preparation, only the most superficial layer of cells was stained indicating that phalloidin could not penetrate the tissue beyond the suprabasal epithelial layer. Detergent (Triton X-100) treatment of the excised cornea and the intact fixed globe, allowed penetration of phalloidin into the suprabasal epithelial layer. Tight junction proteins occludin, ZO-1 and claudin were present in most layers of the cornea but while ZO-1 and occludin were distributed in a typical pericellular pattern, claudin seemed to be particularly prominent in the suprabasal layer and appeared only as a discontinuous punctate pericellular pattern in the superficial layer. Intraepithelial leukocytes were detected in the superficial epithelium and the basal epithelium but not in the suprabasal epithelium. Conclusion: The suprabasal epithelium cell layer appears to represent the main barrier site to the passage of small molecules and cells in the mouse cornea and this property may be attribuatable to prominent claudin expression in this layer.
Scleral Grafts in Ophthalmic Surgery. A Review Dítě, Jakub; Netuková, Magdalena; Procházková, Alexandra ...
Česká a slovenská oftalmologie,
2024, Letnik:
80, Številka:
Ahead of print
Journal Article
Recenzirano
Odprti dostop
To summarize the history and current trends in the use of scleral grafts in ophthalmology.
We conducted a review of the literature through the MEDLINE and Cochrane Library databases. The search terms ...were "sclera", "graft", and "surgery". The search resulted in 1596 articles, of which we evaluated 192 as relevant. The relevant articles were sorted chronologically and according to the method of using scleral grafts, which enabled the development of a review article.
The sclera has been routinely used in ophthalmology since the 1950s in many different indications. Some of these indications have become practically obsolete over time (for example, use in the surgical management of retinal detachment), but a large number still find application today (especially use in glaucoma or oculoplastic surgery, or as a patch for a defect in the sclera or cornea).
Even though allogeneic sclera is currently used less frequently in ophthalmology compared to other tissue banking products and the range of its indications has partially narrowed, it remains a useful material due to its availability and properties.
Purpose The aim of our presentation is to introduce future eye bank product - corneal stromal lenticule from living donors, which can be used for allotransplantation. Methods ReLEx (refractive ...lenticule extraction) SMILE (small incision lenticule extraction) is a common approach in laser eye surgery. It is minimally invasive and flap-free procedure. During this procedure part of corneal stroma (lenticule) is created by femtosecond laser and consequently removed through small incision. The lenticule is basically waste material of the ReLEx SMILE procedure. In the International Eye Bank of Prague, we decided to establish new protocol for lenticule withdrawal, storage and release for transplantation. Results All donors signed an informed consent, and their serum was tested for the presence of infectious diseases. After ReLEx SMILE procedure the lenticule was stored in container with cryopreservation solution and frozen in the eye bank using the same protocol for frozen amniotic membrane. After 6 months in -80°C tissues were defrosted and examined histologically, using conventional light histology staining and electron microscopy. Conclusion We believe, that lenticule from living donor is a safe and effective tissue, that can be used for many indications and in particular situations represents good alternative to whole donor cornea and amniotic membrane.
To evaluate the results of posterior lamellar keratoplasties (DMEK and PDEK) in phakic eyes.
Retrospective analysis of surgeries performed in our department between June 2016 and December 2019. The ...main focus was put on postoperative visual acuity, corneal endothelial cell density and possible peroperative and postoperative complications including cataract formation.
We performed 12 surgeries on 11 eyes of 7 patients. The most prevalent primary diagnosis was Fuchs endothelial dystrophy (7 eyes), followed by bullous keratopathy after phakic anterior chamber IOL implantation (2 eyes) and ICE syndrome (2 eyes). The average length of follow-up was 12.5 months. Clinically significant complicated cataract had developed and was removed in 3 eyes, one eye required rebubbling due to graft detachment and one eye required rePDEK due to graft failure. At the end of follow-up, the average visual acuity was 0.87, while 82% of eyes achieved VA 0.8 or better, and the average endothelial cell density was 1589 cells/mm2.
Posterior lamellar keratoplasties (DMEK and PDEK) can be performed on phakic eyes. When performed by an experienced surgeon, these are safe procedures with good postoperative results and significant advantage in preserving younger patients accommodation.
To report the incidence of early allograft rejection after Descemet membrane endothelial keratoplasty (DMEK), that is, transplantation of isolated Descemet membrane with its endothelium.
The first ...series of 120 eyes of 105 patients operated on for Fuchs endothelial dystrophy or pseudophakic bullous keratopathy, with an average 2 years of follow-up after 9.0- to 10.0-mm-diameter DMEK, enrolled in our study.
During the entire study period, only 1 of the eyes showed any signs of a cellular immune response to the Descemet graft. A 76-year-old patient presented with discomfort, reduced visual acuity to counting fingers, corneal decompensation, and a Khodadoust line in the central cornea 4 months after (decentered) DMEK. Intensified topical corticoid therapy resulted in a complete visual recovery to 20/25 (0.8) within weeks.
A "classic" allograft rejection (with an appearance similar to that after penetrating keratoplasty) can occur after DMEK. However, compared with the earlier (endothelial) keratoplasty procedures, DMEK may be associated with a lower rejection rate of ≤ 1%, despite transplant diameters of ± 9.5 mm. The apparent immune tolerance in DMEK may result from either less "upregulation" or more "downregulation" of the immune system.
The cornea is one of the most commonly transplanted tissues worldwide. It is used to restore vision when severe visual impairment or blindness occurs in patients with corneal diseases or after ...trauma. Due to the global shortage of healthy donor corneas, decellularized corneal tissue has significant potential as an alternative to corneal transplantation. It preserves the native and biological ultrastructure of the cornea and, therefore, represents the most promising scaffold. This article discusses different methods of corneal decellularization based on the current literature. We searched PubMed.gov for articles from January 2009 to December 2023 using the following keywords: corneal decellularization, decellularization methods, and corneal transplantation. Although several methods of decellularization of corneal tissue have been reported, a universal standardised protocol of corneal decellularization has not yet been introduced. In general, a combination of decellularization methods has been used for efficient decellularization while preserving the optimal properties of the corneal tissue.
We investigated Ag trafficking from the cornea and T effector cell activation in secondary lymphoid tissue after corneal transplantation. In preliminary experiments, the central cornea was shown to ...contain a population of CD45(+), CD11b(+), CD11c- cells, with a few MHC class II(+) cells, and F4/80(+) cells. However, MHC class II(+) passenger leukocytes in donor cornea after allografting did not traffic to the draining lymph node. Instead, Ag (plasmid) delivered to the eye via the donor cornea during allograft was detected in host CD11c(+) and F4/80(+) APC in the draining lymph nodes and spleen. The earliest detection of APC-associated Ag was at 6 h in the draining lymph node and 24 h in the spleen. After 48 h Ag was not detected in the draining lymph node but was still present in the spleen. Ag applied to the donor corneal epithelium before allografting induced Ag-specific T cell activation and expansion in the draining lymph node with a peak response at 4-6 days, indicating that cross-presentation of Ag had occurred. We conclude therefore, that Ag is transported from the donor cornea within host APC and that this event occurs within hours after grafting. Ag is cross-presented to host CD4(+) T cells on MHC class II and leads to the activation of Ag-specific effector T cells and clonal expansion in the draining lymph node.
Glaucoma is a significant cause of blindness worldwide, and its treatment remains challenging. The disease progressively leads to damage to the optic disc and thus loss of visual acuity and visual ...field. High intraocular pressure (IOP) is a common risk factor. There are three major methods to treat this disease: topical, laser, and surgical. None of these are completely satisfactory; therefore, alternatives using new biomaterials are being sought. Since biomaterial engineering has experienced significant growth in recent decades, its products are gradually being introduced to various branches of medicine, with the exception of ophthalmology. Biomaterials, such as glaucoma drainage implants, have been successfully used to treat glaucoma. There is significant ongoing research on biomaterials as drug delivery systems that could overcome the disadvantages of topical glaucoma treatment, such as poor intraocular penetration or frequent drug administration. This article summarizes the use of novel biomaterials for glaucoma treatment presented in the literature. The literature search was based on articles published in English on PubMed.gov, Cochranelibrary.com, and Scopus.com between 2018 and 2023 using the following term "biomaterials in glaucoma." A total of 103 published articles, including twenty-two reviews, were included. Fifty-nine articles were excluded on the basis of their titles and abstracts.
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Artificial corneas (keratoprostheses) and biosynthetic collagen-based corneal equivalents are surgical implants designed to ease the global burden of corneal blindness. However, ...keratoprostheses in many cases fail due to development of fibrous retro-corneal membranes (RCM). Fibrous membranes which develop in the anterior chamber after prosthesis implantation do so on a matrix of fibrin. This study investigated fibrin deposition and RCM formation after full-thickness collagen-based hydrogel implants and compared them with syngeneic and allogeneic corneal grafts in mice. Fibrin cleared from the anterior chamber within 14 days in both allo- and syn-grafts but, persisted in hydrogel implants and developed into dense retro-corneal membrane (RCM) which were heavily infiltrated by activated myofibroblasts. In contrast, the number of CD11b+ macrophages infiltrating the initial deposition of fibrin in the anterior chamber (AC) after hydrogel implantation was markedly reduced compared to syn- and allo-grafts. Inoculation of mesenchymal stem cells prior to collagen gel implant promoted clearance of gel-associated fibrin from the anterior chamber. We propose that a failure of macrophage-mediated clearance of fibrin may be the cause of RCM formation after collagen-based hydrogel implants and that mesenchymal stem cell therapy promotes clearance of fibrin and prevents RCM formation.
The manuscript addresses the potential value of bone marrow-derived mesenchymal stem cell therapy for retro-corneal membrane (RCM) formation in full-thickness transplantation of biosynthetic corneal equivalents. This work reports the pathophysiological changes in the anterior chamber of the mouse eye following full-thickness recombinant human cross-linked collagen-based hydrogel implants in which persistent fibrin promotes the development of dense RCM. Furthermore, pre-treatment with mesenchymal stem cells reduces RCM formation and enhances corneal transparency.
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