Limbal Epithelial Transplantation Research Articles

Managing Limbal Stem Cell Deficiency with Simple Limbal Epithelial Transplantation – Perspective and Practical Guide

Limbal stem cell deficiency (LSCD) is an important cause of blindness. Various etiological factors can cause this challenging disease and several ocular and systemic comorbidities often make the management challenging in these cases. Limbal stem cell transplantation (LSCT) is the gold standard treatment for LSCD. Various techniques of LSCT such as conjunctival limbal autograft and cultured limbal epithelial transplantation have been described to treat this condition. Simple limbal epithelial transplantation (SLET) is an innovative technique of LSCT that has established itself as a successful modality for treating LSCD while addressing limitations of other procedures such as cost, reach and replicability. This review attempts to present a detailed account of SLET comprising of case selection criteria, surgical procedure, post operative care and complications and comparative details of the various techniques of LSCT. We also discuss pertinent tips related to the procedure which we hope will be beneficial for both beginner surgeons and those already practicing SLET.

Allogeneic simple limbal epithelial transplantation for bilateral limbal stem cell deficiency in chronic vernal keratoconjunctivitis: A case report.

Introduction and importanceThis report describes the management of bilateral limbal stem cell deficiency (LSCD) in vernal keratoconjunctivitis (VKC) with allogeneic simple limbal epithelial transplantation (allo-SLET).Presentation of caseA 22-year-old female presented with bilateral VKC with total LSCD. A thick fibrotic pannus was present in both eyes, with visual axis involvement in the right eye. The central cornea in the left eye was clear. The patient underwent a cadaveric allo-SLET in the right eye to restore the ocular surface. Systemic immunosuppression with oral cyclosporine was administered following the surgery. The corrected visual acuity with scleral contact lenses (SCL) was 20/20 in both eyes which was maintained until the last follow-up visit, one year after the surgery. No recurrence of LSCD was observed in the right eye and the ocular surface was well epithelialized.DiscussionAllo-SLET is a simple and efficacious surgical technique for bilateral LSCD. Eyes with VKC have a wet ocular surface, relatively clear corneal stroma, and minimal adnexal involvement. Thus, allo-SLET is the ideal procedure to address LSCD in such cases. The systemic immunosuppression that is given for ensuring graft survival can also help control the underlying allergy. Scleral contact lenses improve the visual acuity and their long-term usage does not affect the functioning of the SLET transplants.ConclusionVKC with bilateral LSCD can be successfully managed with allogeneic SLET. Post-operative systemic immunosuppressants are essential to maintain viable grafts. The use of SCL can improve vision and they do not pose any risk to the SLET transplants.

Cotransplantation of Limbal Epithelial and Stromal Cells for Ocular Surface Reconstruction.

PurposeTo propose an improved stem cell-based strategy for limbal stem cell deficiency (LSCD) treatment.DesignExperimental randomized or parallel-group animal study.SubjectsFifty adult male New Zealand white rabbits.MethodsHuman limbal stem/progenitor cells (LSCs) and limbal stromal stem/progenitor cells (LSSCs) were cultured in serum-free conditions and further differentiated into corneal epithelial cells and keratocytes, respectively. All cell types were characterized with lineage-specific markers. Gene expression analysis was performed to identify the potential function of LSSCs in corneal regeneration. Two LSCD models of rabbits for transplantations were used: transplantation performed at the time of limbal and corneal epithelial excision (LSCD model) and transplantation performed after clinical signs were induced in an LSCD model (pLSCD model). The pLSCD model better mimics the pathologic changes and symptoms of human LSCD. Rabbit models received LSC or LSC plus LSSC treatment. Corneal epithelial defects, neovascularization, and opacity were assessed every 3 weeks for 24 weeks. ZsGreen-labeled LSSCs were used for short-term tracking in vivo.Main Outcome MeasuresRates of corneal epithelial defect area, corneal neovascularization and opacity scores, graft survival rate, and immunofluorescence staining of specific markers.ResultsBoth LSC transplantation and LSC plus LSSC cotransplantation effectively repaired the corneal surface in the LSCD model. These 2 strategies showed no significant differences in terms of graft survival rate or epithelial repair. However, corneal opacity was observed in the LSC group (in 3 of 8 rabbits), but not in the LSC plus LSSC group. Notably, when treating LSCD rabbits with distinguishable stromal opacification and neovascularization, cotransplantation of LSCs and LSSCs exhibited significantly better therapeutic effects than transplantation of LSCs alone, with graft survival rates of 87.5% and 37.5%, respectively. The implanted LSSCs could differentiate into keratocytes during the wound-healing process. RNA sequencing analysis showed that the stromal cells produced not only a collagen-rich extracellular matrix to facilitate reconstruction of the lamellar structure, but also niche factors that accelerated epithelial cell growth and inhibited angiogenesis and inflammation.ConclusionsThese findings highlight the support of stromal cells in niche homeostasis and tissue regeneration, providing LSC plus LSSC cotransplantation as a new treatment strategy for corneal blindness.

Cultivated Autologous Limbal Epithelial Cell Transplantation: New Frontier in the Treatment of Limbal Stem Cell Deficiency

Taking into consideration prior human experience with treating limbal stem cell deficiency (LSCD) with cultivated limbal epithelial cells (CLEC) from other countries, we have set a goal to optimize and standardize the techniques of CLEC preparation (called CALEC by our group) for the clinical trial in the United States. We performed an extensive literature review of all human trials, case series, and reports involving autologous cultivated limbal epithelial cell transplantation. Allogeneic cultivated limbal epithelial cell transplantations were reported only when combined with autologous studies. We also searched prior animal data aiding in detailing regulatory toxicology requirements. Between 1997 and 2020, the analysis of human trials revealed 21 studies on autologous grafts, and 13 studies analyzing both autologous grafts and allogeneic grafts. Of a total of 34 studies, 6 studies used good manufacturing process (GMP) facilities, and 11 studies had no animal-derived products or murine feeder layers, whereas only 1 study had both. Overall, the treatment with autologous CLEC grafts was 68.9% successful. In total there were 6 preclinical studies using rabbits, serving as surrogate studies to assess the safety and toxicity of cultivated limbal epithelial cells for human trials. Based on prior human experience, we further optimized the manufacturing conditions with GMP-grade and serum and animal-free reagents, and developed cell characterization assays for the CALEC product release. These data were used to develop a novel and consistent manufacturing process using only qualified and validated reagents for performing the first clinical trial on CALEC transplantation to treat LSCD in the United States.

Conjunctival Autograft versus Combined Amniotic Membrane and Mini-Simple Limbal Epithelial Transplant for Primary Pterygium Excision.

PurposeTo compare outcomes of conjunctival autograft (CAG) and combined amniotic membrane with mini-simple limbal epithelial transplant (mini-SLET) after primary pterygium excision.MethodsAll consenting adults with primary pterygium were included in this study. After pterygium excision, patients were randomized to receive either CAG or mini-SLET and both grafts were held in place with fibrin glue. The patients were followed-up at days 1, 3, 7, 14, and 30 and subsequently at the third, sixth, and ninth months. The recurrence rate was considered as the primary outcome measure whereas the operating time, postoperative symptoms, and surgical complications were considered the secondary outcome measures.ResultsThe study comprised of 264 eyes of 264 patients, of which 233 (88%) completed the nine months of follow-up. Of these, 118 (51%) received CAG and 115 (49%) received mini-SLET. The groups were comparable at baseline. Recurrence of pterygium was seen in two (1.6%) eyes in the CAG group and three (2.6%) eyes in the mini-SLET group (P = 0.68). Operative time for mini-SLET (20.33 1.28 min) was significantly higher than that for CAG (12.01 1.26 min) (P 0.001). Graft displacement was observed in one case in group II (P = 0.999). The Lim Bon Siong (foreign body sensation, lacrimation, pain, and irritation) score in the CAG group was statistically significant for all four symptoms at days 1 and 3; however, at day 7, foreign body sensation, pain, and irritation scores were significantly higher for the CAG group.ConclusionIn this study, the overall recurrence rate was very low and comparable between mini-SLET and the established technique of CAG after performing the primary pterygium excision. Despite a longer surgical time, mini-SLET appears to be a viable option for the management of primary pterygium.

Evaluation of Limbal Stem Cell Transplant Success in Ocular Chemical Injury.

We evaluated limbal stem cell transplant success in limbal stem cell deficiency due to chemical injury at a tertiary eye care center in Turkey with a novel system for describing limbal stem cell deficiency, as developed by the Limbal Stem Cell Working Group. Medical records of 80 eyes of 80 patients after limbal stem cell transplant for limbal stem cell deficiency secondary to chemical injury were included, with patients grouped according to surgical procedure, ie, limbal autograft, limbal allograft, and cultivated limbal epithelial cell transplant. Surgical success was defined as improvement in postoperative year 1 of limbal stem cell deficiency stage. Patients' mean age was 37.9 ± 15.7 years (range, 4-71 years). Male/female ratio was 2.4. Forty-five patients (56.3%) were injured with alkaline substance, and 16 (20%) with acid substance. Mean follow-up time was 60.3 ± 30.6 months (range, 6-118.6 months). Limbal autograft, allograft, and cultivated limbal epithelial cell transplants were performed in 58 (72.5%), 12 (15%), and 10 (12.5%) eyes, respectively. Intervals between injury and surgery in limbal autograft, limbal allograft, and cultivated limbal epithelial cell transplants were 43.3 ± 94.1 months (range, 0.5-592 months), 14.5 ± 10.6 months (range, 2.4-32.5 months), and 122.8 ± 158.9 months (range, 21.1-504 months),respectively (P = .02); and surgical success rates in each group were 65.5%, 41.7%, and 90%, respectively (P = .03). Overall surgical success rate was 65%. Accurate determination of the limbal stem cell deficiency stage is crucial for proper evaluation of surgical success. Surgery type and interval between injury and surgery were the most important factors associated with higher surgical success rates. Despite the limited number of patients in the subgroups, the results were remarkable to emphasize the significance of a novel limbal stem cell deficiency scoring system.

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.

A case of ocular chemical injury

A 11-year-old male patient came to ophthalmology OPD with complaints of loss of vision in left eye since 5 days. Patient gave history of trauma to the left eye by a chemical explosive from a carbide gun, following which patient developed diminution of vision in the left eye since 5 days. Patient was diagnosed with chemical injury. Patient had undergone amniotic membrane transplantation, along with simple limbal epithelial transplantation. After the surgery patient showed drastic improvement.

Waves of COVID-19 Pandemic: Effect on Ocular Surface Services at a Tertiary Eye Center in India

ObjectiveTo describe the impact of lockdown and unlock phases of the coronavirus disease 2019 (COVID-19) pandemic on the ocular surface services at a tertiary eye care center in India.MethodsThis cross-sectional hospital-based study included 18,127 patients presenting between March 25, 2017, and July 31, 2021. A comparative analysis of the data was performed on the patients diagnosed with ocular surface disorders (allergic eye disease, cicatrizing conjunctivitis, dry eye, limbal stem cell deficiency, and ocular surface burns) and ocular surface surgeries (amniotic membrane grafting, keratoprosthesis, mucous membrane grafting, and simple limbal epithelial transplantation) presenting during the lockdown and unlock phases and the previous three years before COVID-19.ResultsThe outpatient numbers dropped to 18.6% (172/954) and surgeries performed decreased to 2.8% (13/461) of pre-COVID-19 volumes during the lockdown phase. This was mainly because of a 74% reduction in the proportion of patients requiring inter-state travel to this tertiary care referral center. There was a gradual recovery of the outpatient numbers to 70.8% (565/798) and surgeries performed to 85.8% (109/127) of pre-COVID-19 volumes by February-March 2021. This gradual incremental trend was seen across all diagnoses and surgeries except for ocular burns, which showed an initial spike in the month of May followed by another sharp increase by the month of September that coincided with the gradual ease of lockdown regulations. The proportion of patients requiring inter-state travel showed an incomplete recovery to 77.2% of pre-COVID-19 distribution by March 2021.ConclusionThe first year of the COVID-19 pandemic saw a drastic reduction in the outpatient numbers and surgical volume in the lockdown phase, which gradually recovered during the unlock period. However, the impact of the second wave was significant and is showing a gradual recovery in patients accessing eye care services.

Midterm outcomes of penetrating keratoplasty following allogeneic cultivated limbal epithelial transplantation in patients with bilateral limbal stem cell deficiency.

To evaluate the midterm outcomes of penetrating keratoplasty (PK) following allogeneic cultivated limbal epithelial transplantation (CLET) for bilateral total limbal stem cell deficiency (LSCD). Ten patients (10 eyes) with bilateral LSCD were enrolled in this prospective noncomparative case series study. Each participant underwent PK approximately 6mo after a CLET. Topical tacrolimus, topical and systemic steroids, and oral ciclosporin were administered postoperatively. Best-corrected visual acuity (BCVA), intraocular pressure (IOP), ocular surface grading scores (OSS), corneal graft epithelial rehabilitation, persistent epithelial defect (PED), immunological rejection, and graft survival rate were assessed. The time interval between PK and allogeneic CLET was 6.90±1.29 (6-10)mo. BCVA improved from 2.46±0.32 logMAR preoperatively to 0.77±0.55 logMAR post-PK (P<0.001). Kaplan-Meier analysis of mean graft survival revealed graft survival rates of 100% at 12 and 24mo and 80.0% at 36mo. PEDs appeared in 5 eyes at different periods post-PK, and graft rejection occurred in 4 eyes. The total OSS decreased from 12.4±4.4 before allogeneic CLET to 1.4±1.51 after PK. A sequential therapy design of PK following allogeneic CLET can maintain a stable ocular surface with improved BCVA despite the relatively high graft rejection rate.

Surgical Management of Unilateral Partial Limbal Stem Cell Deficiency: Conjunctival Autografts versus Simple Limbal Epithelial Transplantation.

PurposeTo evaluate the clinical outcomes of conjunctival autograft (CAG) versus simple limbal epithelial transplant (SLET) for management of unilateral partial limbal stem cell deficiency (LSCD).MethodsThis retrospective, comparative, interventional case series evaluated 30 eyes of 30 patients with unilateral partial LSCD. After corneal pannus dissection, 17 patients underwent CAG where graft was harvested from the ipsilateral or contralateral eye, while 13 patients underwent SLET where limbal biopsy was harvested from the contralateral eye. The primary outcome measure was anatomical success in the form of restoration of a completely epithelised, stable, and avascular corneal surface at last follow-up.ResultsBoth groups were comparable in terms of age at time of surgery, preoperative best-corrected visual acuity, median duration since injury, number of clock hours of limbus involved, and number of previous surgeries performed. The most common etiology for LSCD was chemical burns in both groups. The median duration of post-operative follow-up was 5.6 months [interquartile range [(IQR): 3.6–15.1] in the CAG group versus 6.2 months (IQR: 4.5–12.2) in the SLET group (p=0.75)]. The anatomical success rates were 86.5 ± 8.9% in the CAG group and 28.3 ± 13.7% in the SLET group at final follow-up visit (p = 0.025). Most failures in both groups occurred within the first 8 months after surgery.ConclusionFor eyes with unilateral partial LSCD secondary to chemical burns, CAG is a safe and effective method for restoring the corneal epithelium. Limbal transplantation may not be necessary for the treatment of partial LSCD.

Longitudinal Changes in Corneal Epithelial Thickness and Reflectivity following Simple Limbal Epithelial Transplantation: An Optical Coherence Tomography-Based Study

ABSTRACTPurposeTo describe the changes in corneal epithelial thickness and reflectivity following simple limbal epithelial transplantation (SLET) using anterior segment optical coherence tomography (ASOCT).MethodsThis was a prospective imaging study of 31 eyes of 29 patients who had undergone autologous or allogeneic SLET for limbal stem cell deficiency and had stable, avascular surfaces postoperatively. ASOCT scans of all four quadrants were taken preoperatively and at 1-week, 1-month, 3-month, 6-month, and 1-year postoperative time points in the eyes undergoing SLET. Baseline scans were also taken from the normal eye in unilateral cases. The following parameters were obtained from the scans: (i) epithelial thickness (ET), (ii) stromal thickness, (iii) total corneal thickness, (iv) epithelial reflectivity (ER), (v) stromal reflectivity, and (vi) epithelial/stromal (ES) reflectivity ratio.ResultsChemical injury (24 eyes, 77.4%) was the most common indication for surgery. There was a significant improvement in the ET (184.8 ± 117.1 vs 60.3 ± 10 µm, p < .0001) and ER (144.5 ± 26.4 vs 120.9 ± 28.9, p < .0001) within the initial postoperative period following SLET, which remained stable at the end of 1 year follow-up. There was no difference in the ET of the post-SLET and normal eyes after the 3-month timepoint and this normalization was maintained until the end of the first year. A significant normalization was also noted in the ES reflectivity ratio at the end of 1 year (2.1 ± 0.8 vs 1 ± 0.2, p < .001). A significant correlation was found between the final visual acuity and the total corneal thickness (r = 0.942, p = .005).ConclusionThere is a significant improvement in the epithelial thickness and reflectivity of the cornea in eyes undergoing SLET. ASOCT provides a reliable objective measure of these changes and can be used to monitor the outcomes in these eyes postoperatively.

Allogeneic Cultivated Limbal Epithelial Sheet Transplantation in Reconstruction of Conjunctival Sac After Chemical and Thermal Burns.

The study aims to evaluate the effect of allogeneic cultivated limbal epithelial cell sheet transplantation (CLET) in reconstructing conjunctival sac for severe symblepharon after chemical and thermal burns. A retrospective, non-comparative case series. Thirty-six eyes (36 patients) underwent CLET for severe symblepharon and conjunctival sac stenosis or atresia. Symblepharon was separated, and pseudopterygium was preserved to replace the palpebral conjunctiva. Allogeneic cultivated limbal epithelial cell sheet using human amniotic membrane as a carrier was transplanted into the recipient's eye to reconstruct the conjunctival sac. The effect of conjunctival sac reconstruction, eye and eyelid movement, ocular surface restitution, and symblepharon recurrence were analyzed after surgery. Symblepharon was completely relieved in 30 of the 36 eyes (83.3%) by a single surgical procedure, with fornix reconstruction, as well as free movement of eye globe and eyelids. Strip-like symblepharon remained in 6 eyes (16.7%) and was completely relieved after the second CLET. Twenty patients without visual function received prostheses 3 months after surgery and the other sixteen patients underwent different corneal transplantation for visual acuity improvement. During the follow-up period, no one had symblepharon recurrence. The transplantation of cultivated allogeneic limbal epithelial sheets offers an effective and safe alternative in the treatment of symblepharon and reconstruction of conjunctival sac in eyes with severe ocular burns, which lays the foundation for subsequent treatments.

Preliminary experience & rationale of primary allo Simple Limbal Epithelial Transplantation (SLET) following surgical excision of Ocular Surface Tumors

AimTo report the preliminary outcomes and elucidate the possible rationale of alloSLET for primary ocular surface reconstruction following excision of extensive ocular surface tumors. MethodsRetrospective interventional case series with a minimum postoperative follow up of 1 year. AlloSLET was performed along with wide surgical excision and cryotherapy in 3 eyes. ResultsOf the 2 eyes with extensive OSSN and one with an extensive pigmented lesion, there was no occurrence of symblepharon in all 3 eyes. No features suggestive of LSCD was noted in 2 eyes. In the child with xeroderma pigmentosum and OSSN, early peripheral vascularization was noted at 1 year of follow up with reduced vision secondary to amblyopia. ConclusionPrimary alloSLET could be an alternative to primary autoSLET in eyes with extensive ocular surface tumors, commonly seen with ocular surface squamous neoplasia (OSSN) and pigmented lesions. This facilitates ocular surface reconstruction with reduced occurrence of symblepharon formation as well as limbal stem cell deficie4ncy (LSCD). It possibly, is the only option in eyes with OSSN with coexistent bilateral limbal insufficiency. It may obviate the need for autoSLET, primary or secondary in eyes with adequate residual limbus.

Stem Cells in the Path of Light, from Corneal to Retinal Reconstruction.

The future of eye reconstruction invariably includes stem cells transplantation. Corneal limbus, corneal stroma, trabeculum, retinal cells, optic nerve, and all structures that are irreversibly damaged and have no means to be repaired or replaced, through conventional treatment or surgery, represent targets for stem cell reconstruction. This review tries to answer the question if there is any clinical validation for stem therapies, so far, starting from the cornea and, on the path of light, arriving to the retina. The investigation covers the last 10 years of publications. From 2385 published sources, we found 56 clinical studies matching inclusion criteria, 39 involving cornea, and 17 involving retina. So far, corneal epithelial reconstruction seems well validated clinically. Enough clinical data are collected to allow some form of standardization for the stem cell transplant procedures. Cultivated limbal epithelial stem cells (CLET), simple limbal epithelial transplant (SLET), and oral mucosa transplantation are implemented worldwide. In comparison, far less patients are investigated in retinal stem reconstructions, with lower anatomical and clinical success, so far. Intravitreal, subretinal, and suprachoroidal approach for retinal stem therapies face specific challenges.

Proof-of-concept study of electrospun PLGA membrane in the treatment of limbal stem cell deficiency

ObjectiveThe aim of this study was to assess the safety of poly-lactic co-glycolic acid (PLGA) electrospun membranes as carriers for limbal tissue explants for treatment of limbal stem cell deficiency...

Efficacy and outcome of simple limbal epithelial transplantation for limbal stem cell deficiency verified by epithelial phenotypes integrated with clinical evaluation

PurposeTo evaluate the efficacy and outcome of simple limbal epithelial transplantation (SLET) for limbal stem cell deficiency (LSCD) using epithelial phenotype detection integrated with clinical manifestation. MethodsThis prospective multicenter study included patients with LSCD who underwent autologous SLET (autoSLET) and living-related allogenic SLET (Lr-alloSLET). All patients were assessed by slit-lamp biomicroscopy, in vivo confocal microscopy (IVCM), and impression cytology with immunofluorescence staining (ICIF) before and after surgery. The criteria for success were the presence of a clinically non-conjunctivalized cornea and corneal epithelium detected by IVCM or ICIF. Otherwise, the case would be considered a failure. Visual improvement and risk factors for SLET failure were analyzed. ResultsA total of 28 eyes of 26 patients (11 autoSLET and 17 Lr-alloSLET) were included. The median age was 53 years (range, 35–63), and the follow-up time was 29.5 months (range, 17.5–39.8). The overall survival rate was 89.3% at 2 years and 75.6% at 3 years with no difference between autoSLET and Lr-alloSLET (p = 0.24). Seven eyes subsequently underwent penetrating keratoplasty. Immunohistochemistry analysis showed that all corneal buttons had corneal epithelium and limbal stem cell markers. Visual improvement was achieved in both SLET groups (p < 0.001). Failed SLET developed between 5 and 32 months postoperatively. However, absolute risk factors for SLET failure were unidentified. ConclusionThe efficacy of autoSLET and Lr-alloSLET for LSCD was excellent. Limbal explants can regenerate and restore the corneal surface while maintaining the characteristics of limbal stem cells as shown by epithelial phenotype detection and immunohistochemistry integrated with clinical evaluation.

Tuning Electrospun Substrate Stiffness for the Fabrication of a Biomimetic Amniotic Membrane Substitute for Corneal Healing.

Corneal blindness is the fourth most common cause of vision impairment worldwide with a high incidence in global south countries. A recently developed surgical technique for treating corneal blindness is simple limbal epithelial transplantation (SLET), which uses small pieces of healthy limbal tissue (limbal explants) delivered to the damaged eye using the human amniotic membrane (AM) as a carrier. SLET relies on the use of tissue banks for the AM that reduces the availability of the technique. Replacing the AM with a synthetic membrane is key to making SLET more accessible to those who need it. Previous research has demonstrated the suitability of electrospun poly(lactide-co-glycolide) (PLGA) scaffolds as AM substitutes, and here, we report how these membranes can be tailored to mimic fundamental AM mechanical properties. To modify the stiffness of PLGA electrospun membranes, we explored different electrospinning solvent systems (1,1,1,3,3,3,-hexafluoroisopropanol (HFIP), dichloromethane (DCM), chloroform, and N,N-dimethylformamide (DMF)) and the use of plasticizers (PEG400 and glycerol). PEG400 was found to reduce stiffness from 60 MPa to around 4 MPa, approaching the values shown by the native AM. The biocompatibility of membranes with and without PEG400 was found to be comparable, and cell outgrowth from rabbit/porcine explants was successfully observed on the materials after 3 weeks. This research underpins the manufacture of next-generation fibrous biomimetic membranes that will ultimately be used as amniotic membrane substitutes for biomedical applications including SLET.

Clinical Aspects of Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis With Severe Ocular Complications in Brazil.

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are acute and potentially fatal inflammatory vesiculobullous reactions that affect the skin and mucous membranes, and which are most often triggered by particular medications and infections. In Brazil, the drugs most frequently associated with TEN and SJS include cold medicine such as dipyrone and NSAIDs, followed by carbamazepine, phenobarbital, penicillin, and allopurinol. Genetic variations have been found to increase the risk of SJS/TEN in response to triggering factors such as medications. The most closely associated genes found in Brazilian cold-medicine-related SJS/TEN patients with severe ocular complications are HLA-A*66:01 in those of mixed African and European ancestry and HLA-B*44:03 and HLA-C*12:03 in those of solely European ancestry. Our classification system for grading ocular surface complication severity in SJS/TEN patients revealed the most severe complications to be limbal stem cell deficiency and dry eye. Changes to the conjunctival flora have also been observed in SJS/TEN patients. Our group identified bacterial colonization in 95% of the eyes (55.5% of which were gram-positive cocci, 25.5% of which were gram-negative bacilli, and 19% of which were gram-positive bacilli). Several new treatment options in the acute and chronic ocular management of the SJS/TEN patients have been described. This article highlights some Brazilian institutions' contributions to ocular surface care in both the acute phase (including the use of amniotic membrane transplantation) and the chronic phase (such as eyelid margin and fornix reconstruction, minor salivary gland transplantation, amniotic membrane and limbal transplantation, scleral contact lenses, anti-angiogenic eyedrops for corneal neovascularization, ex-vivo cultivated limbal epithelium transplantation, conjunctival-limbal autografting, oral mucosa transplantation, and keratoprosthesis).

Histopathological Characteristics of Limbal Stem Cell Deficiency Secondary to Chronic Vernal Keratoconjunctivitis.

To describe the histopathological characteristics of limbal stem cell deficiency (LSCD) due to chronic vernal keratoconjunctivitis (VKC). This retrospective study included 14 eyes of 13 patients who underwent simple limbal epithelial transplantation for total LSCD from 2017 to 2018. The histological characteristics of the excised fibrovascular pannus were compared between 2 groups of 7 eyes, each with LSCD due to VKC and chemical burns (CB). Histological characteristics and type of inflammation were studied using special stains and immunohistochemistry. Fisher exact test was used to detect the statistical significance of the histological differences between both groups. Epithelial hypertrophy, epithelial downgrowth, and eosinophilic infiltration were noted in all eyes in the VKC group (7/7, 100%). Epithelial hypertrophy was noted in 3 of the 7 (42.8%) eyes in the CB group, whereas epithelial downgrowth and eosinophilic infiltrates were absent. The average chronic inflammatory score of the pannus (5.28) was higher in VKC than in CB (3.85; P = 0.1080). The presence of goblet cells was higher in the CB group (5/7, 1.4%) than in the VKC group (3/4, 2.8%), although not statistically significant. Other histological differences between the groups were not statistically significant. The histopathological features of LSCD in VKC reveal some distinctive characteristics. These include the presence of epithelial downgrowth, eosinophilic infiltration, and epithelial solid and cystic implants. Although this information may be used to establish the diagnostic criteria for VKC as the cause of LSCD, further studies are needed to elucidate the reasons behind these unique findings.