Severe Limbal Stem Cell Deficiency Research Articles

Three-Dimensional Reconstruction of Subbasal Nerve Density in Eyes With Limbal Stem Cell Deficiency: A Pilot Study.

Corneal subbasal nerve parameters have been previously reported using 2-dimensional scans of in vivo laser scanning confocal microscopy (IVCM) in eyes with limbal stem cell deficiency (LSCD). This study aims to develop and validate a method to better quantify corneal subbasal nerve parameters and changes from reconstructed 3-dimensional (3D) images. IVCM volume scans from 73 eyes with various degrees of LSCD (mild/moderate/severe) confirmed by multimodal anterior segment imaging including IVCM and 20 control subjects were included. Using ImageJ, the scans were manually aligned and compiled to generate a 3D reconstruction. Using filament-tracing semiautomated software (Imaris), subbasal nerve density (SND), corneal nerve fiber length, long nerves (>200 μm), and branch points were quantified and correlated with other biomarkers of LSCD. 3D SND decreased in eyes with LSCD when compared with control subjects. The decrease was significant for moderate and severe LSCD ( P < 0.01). 3D SND was reduced by 3.7% in mild LSCD, 32.4% in moderate LSCD, and 96.5% in severe LSCD. The number of long nerves and points of branching correlated with the severity of LSCD ( P < 0.0001) and with declining SND (R 2 = 0.66 and 0.67, respectively). When compared with 2-dimensional scans, 3D reconstructions yielded significant increases of SND and branch points in all conditions except severe LSCD. 3D analysis showed a 46% increase in long nerves only in mild LSCD ( P < 0.01). This proof-of-concept study validates the use of 3D reconstruction to better characterize the corneal subbasal nerve in eyes with LSCD. In the future, this concept could be used with machine learning to automate the measurements.

Clinical and pathologic characterization of a mouse model of graded limbal stem cell deficiency

Limbal stem cell deficiency (LSCD) is a clinically challenging eye disease caused by damage to limbal stem cells (LSCs). Currently, the international consensus classifies LSCD into three clinical stages based on the disease severity. However, no existing animal models attempt to replicate the varying degrees of LSCD observed in clinical cases. The present study demonstrates an easy-to-create, reproducible, and reliable mouse model of graded LSCD. To achieve mild, moderate, or severe LSCD, filter paper rings with a variety of central angles (90°, 180°, or 270°) are utilized to deliver alkali burns to different sizes of the limbal area (1, 2, or 3 quarters). The animal model has successfully resulted in the development of clinical signs and pathological manifestations in escalating severity that are similarly observed in the three clinical stages of LSCD. Our study thus provides new insights into distinct pathological features underlying different grades of LSCD and serves as a new tool for further exploring the disease mechanisms and developing new effective therapeutics for repairing damaged LSCs.

Allogeneic limbo-deep anterior lamellar keratoplasty (Limbo-DALK)-A novel surgical technique in corneal stromal disease and limbal stem cell deficiency.

To describe a novel corneal surgical technique combining Deep Anterior Lamellar Keratoplasty (DALK) with grafting of allogeneic limbus (Limbo-DALK) for the treatment of eyes with corneal stromal pathology and limbal stem cell deficiency (LSCD). Clinical records of six Limbo-DALKs performed in five patients diagnosed with LSCD and corneal stromal pathology requiring keratoplasty were retrospectively reviewed. All patients were diagnosed with LSCD due to various pathologies including thermal and chemical burns, congenital aniridia or chronic inflammatory ocular surface disease. Parameters analysed included demographics, diagnoses, clinical history, thickness measurements using anterior segment OCT, visual acuity, and epithelial status. Regular follow-up visits were scheduled at 6 weeks as well as 3, 6, 9, and 12 and 18 months postoperatively. Main outcome measures were time to graft epithelialisation and the occurrence of corneal endothelial decompensation. Two grafts showed complete epithelial closure at 2 days, two at 14 days. In one eye, complete epithelial closure was not achieved after the first Limbo-DALK, but was achieved one month after the second Limbo-DALK. No endothelial decompensation occurred except in one patient with silicone oil associated keratopathy. Endothelial graft rejection was not observed in any of the grafts. Based on the data from this pilot series, limbo-DALK appears to be a viable surgical approach for eyes with severe LSCD and corneal stromal pathology, suitable for emergency situations (e.g. corneal ulceration with impending corneal perforation), while minimising the risk of corneal endothelial decompensation.

Outcome of keratolimbal allograft transplantation with deep anterior lamellar keratoplasty for bilateral limbal stem cell deficiency.

To evaluate and compare the outcome of keratolimbal allograft (KLAL) transplantation with or without deep anterior lamellar keratoplasty (DALK) for bilateral severe limbal stem cell deficiency (LSCD). This retrospective review included 49 eyes of 46 patients who underwent KLAL transplantation at the Department of Ophthalmology of Chinese PLA general hospital, 2009-2020, for bilateral severe LSCD were examined for corneal clarity and corneal scarring to determine whether to combine DALK with KLAL transplantation. Preoperative information, surgical decision tree, surgical procedures, and postoperative data were collected for each eye. All patients had preoperative severe or total LSCD. Twenty-four eyes underwent KLAL transplantation only, 25 KLAL transplantation plus DALK. The mean follow-up was 46.80 ± 31.22 months (18-158 months). Overall KLAL survival (with or without DALK) was 71.43% at the final follow-up (KLAL-only 66.67%, KLAL-DALK 76%). Kaplan-Meier survival analysis showed that the 3-year survival probability of all grafts was 70.53 ± 10.89% (KLAL-only 64.86 ± 10.11%, KLAL-DALK 75.79 ± 8.62%). The proportion of BCVA ≥ 20/200 eyes among all KLAL transplantations increased from 11 eyes (22.45%) preoperatively to 25 eyes (51.02%) after 1 year and 24 eyes (48.98%) at the last follow-up (P = 0.01). The proportion of BCVA ≥ 20/200 eyes in the KLAL-DALK group increased significantly (P = 0.04), from 16.0% at baseline to 48.0% after 1 year to 44.0% at the last follow-up. Seventeen eyes (34.69%) had postoperative complications. KLAL-DALK is an effective option to restore a stable ocular surface and visual acuity rapidly in patients with bilateral, late-stage, severe LSCD.

Downregulation of p38 MAPK Signaling Pathway Ameliorates Tissue-Engineered Corneal Epithelium.

Tissue-engineered corneal epithelium transplantation is effective treatment for severe limbal stem cell deficiency (LSCD), while epithelial terminal differentiation, tans-differentiation, and insufficient stem cell during construction affect the quality of tissue-engineered corneal epithelium. In this study, we applied SB203580 in the culture medium to downregulate the p38 mitogen-activated protein kinase (MAPK) signaling pathway during construction of tissue-engineered corneal epithelium. With application of SB203580, tissue-engineered corneal epithelium showed enhanced strength and condensed structure. The expression of progenitor cell markers ATP-binding cassette sub-family G member 2, tumor protein p63, keratin 14, and Wnt family member 7A was increased, differentiation markers keratin 12, paired box 6, keratin 10, and keratin 13 and trans-differentiation markers actin alpha 2, smooth muscle and snail family transcriptional repressor 1 was decreased, while cell junction markers claudin 1 and cadherin 1 was increased in the tissue-engineered corneal epithelium. The Wnt/catenin beta 1 signaling pathway was upregulated in the epithelium after p38 MAPK inhibition. Transplantation of tissue-engineered corneal epithelium treated with SB203580 to rabbit LSCD model showed faster wound healing and improved epithelial quality. We conclude that downregulation of p38 MAPK signaling pathway helps maintain the stemness and prevent terminal differentiation and abnormal differentiation of corneal epithelial cells during epithelium construction process, and thus can improve the quality of tissue-engineered corneal epithelium. Impact statement Downregulation of p38 MAPK signaling pathway helps maintain the self-renewal of limbal stem cells and prevents terminal differentiation and abnormal differentiation of corneal epithelial cells. Small molecules modulating p38 MAPK signaling pathway ameliorate tissue-engineered corneal epithelium.

Pediatric Phlyctenular Keratoconjunctivitis at a Tertiary Care Center in the United States.

The aim of this study was to evaluate characteristics and outcomes of pediatric phlyctenulosis at a tertiary care center in the United States. A retrospective cohort study of phlyctenulosis diagnosis in patients younger than 18 years was conducted. Demographics, presenting features, treatment regimens, and outcomes were analyzed. Seventy patients (95 eyes) with phlyctenulosis were identified. Fifty-four patients (77.1%) were Hispanic, which was greater than the center's proportion of pediatric patients identifying as Hispanic (53.8%, P < 0.0001). Common comorbidities included adjacent external/lid disease (82.9%), allergic/atopic disease (18.6%), and viral infections (8.6%). Nine patients had tuberculosis testing which was negative in all cases. Five patients had vitamin A testing which revealed deficiency in 1 patient. Treatment regimens were diverse and included varying combinations of topical and systemic medications. Complications included corneal scarring (27.4%), corneal neovascularization (40.0%), amblyopia (16.8%), corneal perforation (3.2%), and severe limbal stem-cell deficiency (1.1%). 26.3% of affected eyes had final visual acuity worse than 20/40. Differences in rates of corneal complications between Hispanic and non-Hispanic patients were not statistically significant, although severe corneal complications including perforation occurred only in the Hispanic group. This study presents a modern cohort of phlyctenulosis at a tertiary center in the United States and includes a larger proportion of Hispanic patients than expected. Phlyctenulosis carries high corneal morbidity and may frequently result in reduced visual acuity. Similar rates of corneal complications were seen in Hispanic versus non-Hispanic patients, but severe corneal complications were seen only in the Hispanic group.

Cultivated Limbal Epithelial Transplant Versus Conjunctival Limbal Auto Transplant in Uniocular Limbal Stem Cell Deficiency: Long-Term Results

Purpose: To evaluate and compare long-term efficacy of cultivated limbal epithelial cell transplant (CLET) and conjunctival limbal autograft (CLAU) in uniocular limbal stem cell deficiency (LSCD) in chemically injured eyes. Methods: This was a retrospective, interventional, comparative study, and comprised of sixty- one patients with unilateral severe LSCD who underwent CLET (10) and CLAU (51 patients). Surgical Procedure: Surgical procedure in CLET included superficial keratectomy, excision of fibrovascular tissue, securing amniotic membrane supporting cultured limbal stem cells and placement of bandage contact lens. CLAU included superficial keratectomy, excision of fibrovascular tissue, securing limbal stem cells graft with / without amniotic membrane transplant (AMT). Results: Following CLET ocular surface improved in all 10 patients and visual acuity improved significantly in three cases. CLAU was performed in 33 eyes and combined CLAU + AMT in 18 eyes. Visual acuity improved significantly in 26 (51%) eyes. Ocular surface and symblepharon grades improved in all patients during a mean 58.7±21.9 months follow up. Conclusion: CLET and CLAU is safe and effective in rehabilitating the ocular surface before penetrating keratoplasty (PKP) in uniocular severe LSCD. CLET has the advantage of avoiding iatrogenic limbal stem cell deficiency. CLAU enabled us to repair symblepharon simultaneously by taking extra conjunctiva.

Phenotypic Characterization of Corneal Epithelium in Long-Term Follow-Up of Patients Post-Autologous Cultivated Oral Mucosal Epithelial Transplantation.

To analyze the phenotype of the corneal epithelium in patients with long-term follow-up who underwent autologous cultivated oral mucosal epithelial transplantation (COMET) using in vivo confocal microscopy (IVCM) and impression cytology with immunofluorescence staining (ICIF). Thirteen eyes from patients with severe limbal stem cell deficiency, who underwent COMET at least 48 months before, were recruited in this noncomparative cohort study. After eye examination, IVCM and ICIF were performed. Clinical manifestations of the cornea were evaluated and compared with epithelial findings detected by IVCM and ICIF [cytokeratin (CK) 3, CK7, and CK12]. Two corneal buttons derived from patients receiving the corneal transplantation post-COMET were sent for immunohistochemistry (CK3, CK6, CK7, CK12, paired box gene 6, p63, zonula occludens-1, and integrin β -1). The mean age of patients was 51.2 ± 20.6 years, and the mean follow-up time since COMET was 78.7 ± 16.3 months. Six of 13 eyes showed clinically successful COMET. In these eyes, IVCM demonstrated predominant cornea-like epithelium and ICIF reported positivity for CK3 and CK12, confirming the presence of oral mucosal and corneal epithelium. Meanwhile, 7 eyes showed total conjunctivalization, corresponding with substantial conjunctival epithelium detected by IVCM and positivity for conjunctival (CK7) and oral mucosal epithelial (CK3) markers detected by ICIF. The immunohistochemistry of corneal buttons stained positive for oral mucosal, corneal epithelial, and stem cell markers (CK3, CK12, and p63). In long-term follow-up of COMET, epithelium of successful patients demonstrated cornea-like phenotype, whereas failed cases revealed mainly conjunctival phenotype. However, there were evidences that oral mucosal epithelial cells remained across the cornea in both successful and failed COMET as detected by IVCM and ICIF.

Risk factors for partial and total loss of limbal stem cells

Introduction: In certain pathological conditions limbal stem cells are unable to function adequately - to proliferate and differentiate through their inferior capabilities to maintain corneal integrity. They are either reduced in number or have abnormal cell function. This condition is known as limbal stem cell deficiency. Depending on its severity, limb stem cell deficiency is divided into partial (sectoral) and total diffuse. Aim: The purpose of this study is to investigate the risk factors for limbal stem cell deficiency. Material and M ethods: The study included 64 patients with LSC deficiency and the risk factors for setting in and progression of the disease were evaluated using a questionnaire and clinical trials. The results were processed with SPSS v. 20 for Windows, using variation, comparative and correlation analyses, and risk assessment analysis (RR). Results and D iscussion: As a primary risk factor wearing contact lenses that have a moderate dependence (r = 0.455; p <0.001) and carry a high risk of developing mild LSC (limbal stem cell) deficiency (RR = 13.85 (2.65 - 72.46)) stands out. A major risk factor for patients with moderate LSC deficiency are penetrating injuries that have a moderate dependence (r = 0.475; p <0.001) and significantly higher risk (RR = 15.37 (2.92 - 81.01)). In the severe form of LSC deficiency the major risk factors are chemical and thermal burns that have a significant correlation (r = 0.525; p <0.001) with severe LSC deficiency and carry an extremely high risk (RR = 12.35 (3.43 - 44.53) ) of occurring. Conclusion: The major risk factors for total limbal stem cell loss are chemical burns and injuries, and risk factors for partial loss are iatrogenic factors and the dry eye syndrome.

Corneal epithelial restoration after penetrating keratoplasty in repeated failed cultivated limbal stem cell grafts

Abstract Purpose To report a case of corneal epithelial restoration after penetrating keratoplasty following multiple complications in repeated failed cultivated stem cell grafts. Methods This is a case report of a 62-year old patient who was treated for unilateral severe limbal stem cell deficiency after a chemical burn of the right eye. Results Two attempts to reconstruct the ocular surface using autologous cultivated limbal stem cell grafts (CLET) failed, and were complicated by perforations requiring two emergency penetrating keratoplasties. While the first donor cornea revascularised quickly, the corneal epithelium of the second remained transparent, avascular and stable until one year postoperatively. In vivo confocal microscopic examination confirmed presence of a healthy corneal epithelial phenotype. Conclusions Occurrence of serious adverse events are related to an inadequate epithelial homeostasis following CLET. The mechanisms of action of limbal stem cell transplantation are still poorly understood and the corneal epithelial integrity may be maintained without limbal input.

Epithelial analysis of simple limbal epithelial transplantation in limbal stem cell deficiency by in vivo confocal microscopy and impression cytology.

Simple limbal epithelial transplantation (SLET) is a relatively new treatment for severe limbal stem cell deficiency. Outcomes of treatment are typically determined based on clinical manifestations. In this prospective-multicenter study, we aimed to analyze the epithelial phenotypes of the corneas after SLET using IVCM and IC, and correlated them with clinical findings. Ten eyes of nine patients, who underwent SLET (five autologous SLET and five living-related SLET) were recruited. A set of examinations included slit-lamp biomicroscopy, corneal in vivo confocal microscopy (IVCM), and impression cytology (IC) was performed in all eyes at least twice (≥ 3-month interval) postoperatively. Then, a correlation between findings of the three examinations was analyzed. There were seven eyes with clinical success (no central neovascularization) showed pure corneal epithelial phenotype or mixed corneal-conjunctival phenotypes (mostly cornea) in either IVCM or IC. Three eyes with clinical failure, presented with peripheral and central neovascularization, showed total or predominant conjunctival phenotype in IVCM and sole conjunctival phenotype in IC. From a total of 22 sets of examinations, there was a high correlation between clinical manifestation vs. IC (κ = 0.844, observed agreement = 81.82%) and a substantial correlation between clinical manifestation vs. IVCM (κ = 0.727, observed agreement = 76.19%) and between IVCM versus IC (κ = 0.729, observed agreement = 76.19%). In conclusion, IVCM and IC facilitate determination of epithelial phenotype of the cornea after SLET. There was a substantial to high correlation between IVCM, IC and clinical presentations. Findings observed by IVCM and IC may allow early detection of epithelial alterations in eyes underwent SLET before clinical recognition.

Case series of cultivated oral mucosa epithelium transplantation for limbal stem cell failure

Purpose: To report a case series of seven eyes (six patients) with severe limbal stem cell failure who underwent cultivated oral mucosa epithelium transplantation (COMET) in preparation for corneal transplant surgery and assess the change in visual acuity postoperatively.&#x0D; Design: Case series.&#x0D; Methods: A retrospective analysis of an interventional case series of six patients with severe limbal stem cell deficiency who underwent COMET between 2012 and 2015 was performed. Six eyes had COMET followed by corneal transplant, and one eye had corneal transplant preceding COMET. The change in the visual acuity after operation was evaluated.&#x0D; Results: A total of six patients with seven eyes were studied. All of them had severe ocular surface disease with limbal stem cell deficiency (LSCD) secondary to chemical injury (five eyes), SJS (one eye), and severe ocular rosacea (one eye). Four eyes had improvements in visual acuity, two of which achieved best corrected visual acuity (BCVA) of 6/12.&#x0D; Conclusion: The use of COMET helps to optimize the ocular surface in severe LSCD for further corneal transplant surgeries. It has helped to improve the graft uptake and subsequent visual improvement, especially in chronic chemical burn cases.&#x0D;

Classification of Limbal Stem Cell Deficiency Using Clinical and Confocal Grading

To grade the severity of limbal stem cell deficiency (LSCD) based on the extent of clinical presentation and central corneal basal epithelial cell density (BCD). This is a retrospective observational comparative study of 48 eyes of 35 patients with LSCD and 9 eyes of 7 normal subjects (controls). Confocal images of the central cornea were acquired. A clinical scoring system was created based on the extent of limbal and corneal surface involvement. LSCD was graded as mild, moderate, and severe stages based on the clinical scores. The degree of BCD reduction was given a score of 0 to 3. Compared with BCD in controls, BCD decreased by 23.0%, 40.4%, and 69.5% in the mild, moderate, and severe stages of LSCD classified by the clinical scoring system, respectively. The degree of BCD reduction was positively correlated with larger limbal and corneal surface involvement and when the central visual axis was affected (all P ≤ 0.0005). Mean corrected distance visual acuity logarithm of the minimum angle of resolution was 0.0 ± 0.0 in control eyes, 0.2 ± 0.5 in mild LSCD, 0.6 ± 0.4 in moderate LSCD, and 1.6 ± 1.1 in severe LSCD (P < 0.0001). There was a significant correlation between a higher clinical score and corrected distance visual acuity logarithm of the minimum angle of resolution (rho = 0.82; P < 0.0001) and a greater decrease in BCD (rho = -0.78; P < 0.0001). A clinical scoring system was developed to assess the extent of clinical presentation of LSCD. A classification system to grade the severity of LSCD can be established by combining the BCD score with the clinical score.

Surgical management of severe ocular surface injury due to Roman candle explosion accidents

PurposeTo report the clinical features, management, and outcomes of patients with ocular surface damage secondary to Roman candle explosion accidents. MethodsRetrospective, noncomparative, interventional case series of 11 patients with Roman candle explosion-related ocular surface injuries referred to the Cincinnati Eye Institute between 2007 and 2016. ResultsEleven patients (10 male, 1 female, mean age 22.4 years) sustained unilateral ocular surface injuries with presenting visual acuity ranging from count fingers to light perception. All patients had severe limbal stem cell deficiency with total ocular surface failure. Eight eyes received a conjunctival-limbal autograft (CLAU) with a keratolimbal allograft (KLAL), 1 eye received a living related-conjunctival limbal allograft (lr-CLAL) with a KLAL, and 2 eyes received a CLAU with lr-CLAL. Nine eyes underwent subsequent penetrating keratoplasty, and 7 eyes had reconstructive eyelid surgery. Nine eyes demonstrated improved visual acuity at last follow-up; seven eyes demonstrated a stable ocular surface at last follow-up. Nonadherence was noted in 7 patients, either with poor adherence with post-operative treatment or poor follow-up; this portended a worse visual result. ConclusionsRoman candle-related accidents can lead to severe ocular surface injury. Despite total ocular surface failure, these eyes can achieve good postoperative visual results following limbal stem cell transplantation and subsequent keratoplasty with appropriate compliance.

Nature and incidence of severe limbal stem cell deficiency in Australia and New Zealand.

This study aimed to determine the nature and incidence of severe limbal stem cell deficiency (LSCD) in Australia and New Zealand. A 1-year pilot surveillance study with a 1-year follow-up period was conducted in association with the Australian and New Zealand Ophthalmic Surveillance Unit. The study included patients reported by practising ophthalmologists on the Surveillance Unit's database. Ophthalmologists were provided with a definition of severe limbal stem cell deficiency, contacted on a monthly basis by the Unit and asked to report newly diagnosed cases. Severe LSCD was defined as at least 6 clock hours of whorl-like epitheliopathy, an opaque epithelium arising from the limbus, late fluorescein staining of the involved epithelium and superficial corneal neovascularization or conjunctivalization. On average, 286 report cards were sent by the Surveillance Unit to practising ophthalmologists each month (total 3429 over 12 months) and the Unit received an average of 176 responses per month (total 2111; 62% response rate). During the 1-year study period from April 2013 to March 2014, 14 positive cases were reported to the Unit. A range of underlying aetiologies were implicated, with contact lens over-wear and cicatrizing conjunctivitis being the most common (n = 3). This surveillance study is the first worldwide to document the incidence of limbal stem cell deficiency; however, because of study design limitations, it is likely to have been under-reported. It provides novel data on the demographics, clinical conditions and management of patients with limbal stem cell deficiency as reported by treating ophthalmologists.

Management of Limbal Stem Cell Deficiency: A Historical Perspective, Past, Present, and Future.

To review the management of limbal stem cell deficiency (LSCD) from a historical perspective, report the current treatment guidelines, and propose potential future treatments. A literature review was conducted to identify key publications regarding the management of LSCD since treatments were first reported. The advances in surgical treatments, as well as postoperative management, are described from a historical perspective. In addition, current treatment guidelines, as well as future management strategies, are discussed. The management of LSCD has changed dramatically during the last several decades. Before the understanding of the anatomy and physiology of the limbus, all patients with severe LSCD had a dismal prognosis. It was not until the understanding of the location and function of the limbal stem cells that successful management protocols could be formulated. This research gave rise to medical and surgical treatment that protected or replaced diseased or absent limbal stem cells. Understanding the role of the conjunctiva in severe ocular surface disease was also critical in the management of LSCD. Continued improvement in tissue harvesting and surgical techniques have led to improved outcomes in LSCD patients. Significant progress has been made during the last several decades to manage patients with LSCD. A substantial percent of patients can achieve improved visual acuity with current techniques. Continued research with new cell culture and tissue engineering techniques may be the next breakthrough to improve the outcomes for these most challenging patients.

PSY37 - Cost-effectiveness analysis of Ex-Vivo expanded Autologous Corneal Epithelial Cells containing Stem Cells to repair the damaged ocular surface in Patients with moderate to severe Limbal Stem Cell deficiency due to Ocular Burns in the UK

PSY37 - Cost-effectiveness analysis of Ex-Vivo expanded Autologous Corneal Epithelial Cells containing Stem Cells to repair the damaged ocular surface in Patients with moderate to severe Limbal Stem Cell deficiency due to Ocular Burns in the UK

T-style keratoprosthesis based on surface-modified poly (2-hydroxyethyl methacrylate) hydrogel for cornea repairs.

Corneal disease is a common cause of blindness, and keratoplasty is considered as an effective treatment method. However, there is a severe shortage of donor corneas worldwide. This paper presents a novel T-style design of a keratoprosthesis and its preparation methods, in which a mechanically and structurally effective artificial cornea is made based on a poly(2-hydroxyethyl methacrylate) hydrogel. The porous skirt was modified with hyaluronic acid and cationized gelatin, and the bottom of the optical column was coated with poly(ethylene glycol). The physical properties of the T-style Kpro were analyzed using ultraviolet and visible spectrophotometry and electron scanning microscopy. The surface chemical properties were characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface modification in the spongy skirt promoted cell adhesion and produced a firm bond between the corneal tissue and the implant device, while the surface modification in the optic column resisted cell adhesion and prevented retroprosthetic membrane formation. Through improved surgical techniques, the novel T-style keratoprosthesis provides enough mechanical stability to facilitate long-term biointegration with the host environment. In vivo implantation experiments showed that the T-style keratoprosthesis is a promising cornea alternative for patients with severe limbal stem cell deficiency and corneal opacity.

Diverse Approval Systems for Autologous Human Cells and Tissue Products

Human cells and tissue products are newly categorized products which are containing, consisting of, or derived from cells or tissue that are intended for implantation, transplantation, infusion, or transfer into human recipient. The human cells and tissue products are divided as autologous or allogeneic based on their origin. Since another product fabricated with patient’s own limbal epithelial stem cells, was approved as conditional approval for therapeutic indication which is the treatment of adult patients with moderate to severe limbal stem cell deficiency in the European Union, we reviewed the European Public Assessment Report. Of the ten autologous human cells and tissue products, the five products were evaluated using the clinical data with clinical experiences as well as retrospective observatory study or registry, or open clinical trials with small subjects, although for the rest of the products comparative clinical trials with control treatment were performed. In general, autologous human cells and tissue products would need post market-oriented evaluation rather than premarket-oriented evaluation for patients because some of these indications are for orphan diseases or life-threatening disease. However, the other products intended for repair of cartilaginous defects of knee, treatment of prostate cancer, or improvement of the appearance of nasolabial fold winkles were evaluated using comparative clinical data. As for the approval pathways, expedited or normal, both approval pathways are available in the US, the EU, and Japan. The expedited pathways include accelerated approval and humanitarian device exception in the US, conditional market authorization and market authorization under exceptional circumstances in the EU, and a conditional/time-limited approval system in Japan. Our additional review suggests that autologous human cells and tissue products approved using the expedited approval pathway would need post market-oriented evaluation rather than premarket-oriented evaluation.

Coculture of autologous limbal and conjunctival epithelial cells to treat severe ocular surface disorders: Long-term survival analysis

Background:Cultivated limbal epithelium for reconstruction of corneal surface is a well-established procedure; however, it is not adequate for damage which also extensively involves the conjunctiva. In severe cases of ocular surface damage that warrant additional conjunctival transplantation apart from cultivated limbal stem cell transplantation, we describe the long-term survival of a novel method of cocultivating autologous limbal and conjunctival epithelium on a single substrate.Materials and Methods:Forty eyes of 39 patients with severe limbal stem cell deficiency and conjunctival scarring or symblepharon underwent transplantation of autologous cocultivated epithelium on human amniotic membrane. A ring barrier was used to segregate the central limbal and peripheral conjunctival epithelia in vitro. Patients were followed up at regular intervals to assess stability of the ocular surface, defined by absence of conjunctivalization into the central 4 mm of the cornea and absence of diffuse fluorescein staining. Penetrating keratoplasty (PKP) was subsequently performed, where indicated, in patients with surface stability.Results:The cumulative survival probability was 60% at 1 year and 45% at 4 years by Kaplan–Meier analysis (mean follow-up duration: 33 ± 29 months, range: 1–87 months). Best-corrected visual acuity improved to greater than 20/200 in 38% eyes at the last follow-up, compared with 5% eyes before surgery. Immunohistochemistry in five of the corneal buttons excised for PKP showed an epithelial phenotype similar to cornea in all five.Conclusions:Synchronous use of cultured limbal and conjunctival epithelium offers a feasible alternative and a simpler one-step surgical approach to treat severe ocular surface disorders involving limbus and conjunctiva.