Inhibition effect of curcumin on UVB-induced secretion of pro-inflammatory cytokines from corneal limbus epithelial cells

~ AIM： To study the effects of curcumin on the secretion of interleukin （IL） -6 and IL-8 by corneal limbus epithelial cells. METHODS： Human corneal Iimbus epithelial cells were isolated and cultured from donor eyes and irradiated by UVB at different dosages with or without curcumin. MTT test was used for studying the effects of UVB and curcumin on the cell viability. The role of mitogen-activated protein kinase （MAPK） and nuclear factor-kappa B （NF-KB） pathways on the UVB-induced secretion of IL.6 and IL-8 were tested by addition of their inhibitors to the culture with or without UVB-radiation. Levels of various signal pathways, IL-6 and IL-8 in the cells and in the conditioned culture medium were measured by ELISA analysis. RESULTS： UVB at 20 mJ/cm2 or less and curcumin at 20 IJmol/L or less did not affect the cell viability of culturedlimbus epithelial cells （P〉0.05）. UVB irradiation at 10 and 20 mJ/cm2 induced a significant increase of secretion of IL-6 and IL-8 and upregulated NF-KB and phosphorylated MAPK pathways of cultured limbus epithelial cells （P〈0.05）. Various signal pathway inhibitors, including SP600125 （JNK inhibitor）, SB203580 （p38 MAPK inhibitor） and BAY11-7082 （NF-KB inhibitor） significantly decreased the UVB-induced secretion of IL-6 and IL-8 secretion （P〈0.05）. Curcumin at 5-20 pmol/L significantly inhibited UVB- induced secretion of IL-6 and IL-8 by limbus epithelial cells in a dose-dependent manner; while curcumin alone did not affect the secretion of IL-6 and IL-8. The upregulation of NF-KB and MAPK pathways induced by UVB treatment was significantly inhibited by curcumin, suggesting that NF-KB and MAPK pathways are involved in the inhibitory effect of curcumin on UVB-induced production of IL-6 and IL-8.

Corneal stromal mesenchymal stem cells: reconstructing a bioactive cornea and repairing the corneal limbus and stromal microenvironment

Corneal stroma-derived mesenchymal stem cells(CS-MSCs) are mainly distributed in the anterior part of the corneal stroma near the corneal limbal stem cells(LSCs). CS-MSCs are stem cells with self-renewal and multidirectional differentiation potential. A large amount of data confirmed that CS-MSCs can be induced to differentiate into functional keratocytes in vitro, which is the motive force for maintaining corneal transparency and producing a normal corneal stroma. CS-MSCs are also an important component of the limbal microenvironment. Furthermore, they are of great significance in the reconstruction of ocular surface tissue and tissue engineering for active biocornea construction. In this paper, the localization and biological characteristics of CS-MSCs, the use of CS-MSCs to reconstruct a tissue-engineered active biocornea, and the repair of the limbal and matrix microenvironment by CS-MSCs are reviewed, and their application prospects are discussed.

A sutureless subconjunctival M-shaped limbus incision for hard cataracts

Dear Editor,Iam Dr.Ping-Hong Lai,from the Jiangxi Eye Center,Jiangxi Provincial People＇s Hospital,Nanchang,Jiangxi Province,China.I would like to present the technique of subconjunctival M-shaped limbus incision for a series of cases with hard cataracts.

Effect of Bilateral Lateral Rectus Recession in Intermittent Exotropia according to the Limbus Insertion Distance

Purpose: The aim of this work was the evaluation of the effect of the limbus insertion distance (LID) of the lateral rectus on the surgical results of bilateral lateral rectus recession in intermittent exotropia (IXT) in children and adults. Patients and Methods: This retrospective study included 76 patients. The patients were divided into two groups: group I (age 5 - 13 y), group II (>13 y). All the patients had basic type of intermittent exotropia (IXT) and all of them underwent bilateral lateral recessions according to the preoperative angle of deviation. Intraoperatively, the distance of limbus insertion was measured by surgical calipers. The dose response effect was calculated as the difference between the preoperative angle and postoperative angle divided by total amount of recession and cases were followed at 1 month, 3 months, 6 months and 12 months postoperative. Results: The mean LID in group I was (6.2 ± 0.61 mm) and (6.1 ± 0.55 mm) in group II. The mean dose response (MDR) at 1 year postoperative was (2.32 ± 0.25 mm) in group I and (2.26 ± 0.23) in group II. In patients with LID 6.25 mm who had larger mean dose response (2.52 ± 0.15). There was a significant positive correlation between the LR muscle LID and the dose-response effect. Conclusion: There is positive correlation between the LID of the LR muscle and the recession effect in bilateral lateral rectus recession in treatment of IXT.

The Limbal Niche and Its Role in Maintaining Corneal Regeneration

In recent years, stem cells have been a focal point in research designed to evaluate the efficacy of ophthalmologic therapies, specifically those for corneal conditions. The corneal epithelium is one of the few regions of the body that maintains itself using a residual stem cell population within the adjacent limbus. Stem cell movement has additionally captivated the minds of researchers due to its potential application in different body regions. The cornea is a viable model for varying methods to track stem cell migratory patterns, such as lineage tracing and live imaging from the limbus. These developments have the potential to pave the way for future therapies designed to ensure the continuous regeneration of the corneal epithelium following injury via the limbal stem cell niche. This literature review aims to analyze the various methods of imaging used to understand the limbal stem cell niche and possible future directions that might be useful to consider for the better treatment and prevention of disorders of the cornea and corneal epithelium. .

An interferometric ex vivo study of corneal biomechanics under physiologically representative loading,highlighting the role of the limbus in pressure compensation

Background:The mechanical properties of the cornea are complex and regionally variable.This paper uses an original method to investigate the biomechanics of the cornea in response to hydrostatic loading over the typical physiological range of intra-ocular pressure(IOP)fluctuations thereby increasing understanding of clinically relevant corneal biomechanical properties and their contributions to the refractive properties of the cornea.Methods:Displacement speckle pattern interferometry(DSPI)was used to measure the total surface displacement of 40 porcine and 6 human corneal-scleral specimens in response to pressure variations up to 1 mmHg from a baseline of 16.5 mmHg.All specimens were mounted in a modified artificial anterior chamber(AAC)and loaded hydrostatically.Areas of high strain in response to loading were identified by comparing the displacements across different regions.Results:The nature of the response of the corneal surface to loading demonstrated high regional topographic variation.Mechanical properties were shown to be asymmetrical,and deformation of the limbal and pre-limbal regions dominated these responses respectively with over 90%(N-T)and 60%(S-I)of the total maximum displacement occurring in these regions indicating high-strain.In contrast,the curvature of the central cornea remained relatively unchanged merely translating in position.Conclusions:The limbal and pre-limbal regions of the cornea appear to be fundamental to the absorption of small pressure fluctuations facilitating the curvature of the central cornea to remain relatively unchanged.The differential mechanical properties of this region could have important implications for the application of corneal surgery and corneal crosslinking,warranting further investigation.

An interferometric ex vivo study of corneal biomechanics under physiologically representative loading,highlighting the role of the limbus in pressure compensation

Background:The mechanical properties of the cornea are complex and regionally variable.This paper uses an original method to investigate the biomechanics of the cornea in response to hydrostatic loading over the typical physiological range of intraocular pressure(IOP)fluctuations thereby increasing understanding of clinically relevant corneal biomechanical properties and their contributions to the refractive properties of the cornea.Methods:Displacement speckle pattern interferometry(DSPl)was used to measure the total surface displacement of 40 porcine and 6 human corneal-scleral specimens in response to pressure variations up to 1 mmHg from a baseline of 16.5 mmHg.All specimens were mounted in a modified artificial anterior chamber(AAC)and loaded hydrostatically.Areas of high strain in response to loading were identified by comparing the displacements across different regions.Results:The nature of the response of the corneal surface to loading demonstrated high regional topographic variation.Mechanical properties were shown to be asymmetrical,and deformation of the limbal and pre-limbal regions dominated these responses respectively with over 90%(nasal-temporal)and 60%(superior-inferior)of the total maximum displacement occurring in these regions indicating high strain.In contrast,the curvature of the central cornea remained relatively unchanged merely translating in position.Conclusions:The limbal and pre-limbal regions of the cornea appear to be fundamental to the absorption of small pressure fluctuations facilitating the curvature of the central cornea to remain relatively unchanged.The differential mechanical properties of this region could have important implications for the application of corneal surgery and corneal crosslinking,warranting further investigation.

An updated narrative review of treatment for limbal epithelial stem cell deficiency

Background and Objective:Nearly 30 years have passed since limbal stem cell deficiency(LSCD)was first identified by pioneers and given clinical attention.LSCD remains a difficult disease to treat.It can potentially lead to blinding.At present,understanding of limbal stem cells(LSCs)has deepened and various treatment options for LSCD have been devised.The objective of this review is to summarize basic knowledge of LSCD and current treatment strategies.Methods:PubMed search was performed to find studies published in English on LSCs and LSCD including original reports and reviews.Literatures published from 1989 to 2022 were reviewed.Key Content and Findings:LSCs are enigmatic stem cells for which no specific marker has been discovered yet.Although LSCD is not difficult to diagnose,it is still challenging to treat.An important advancement in the treatment of LSCD is the provision of guidelines for selecting systematic surgical treatment according to the patient’s condition.It is also encouraging that stem cell technologies are being actively investigated for their potential usefulness in the treatment of LSCD.Conclusions:Although various treatment options for LSCD have been developed,it should be kept in mind that the best chance of treatment for LSCD is in the early stage of the disease.Every effort should be made to preserve as many LSCs as possible in the early treatment of LSCD.

Human amniotic membrane transplantation: Different modalities of its use in ophthalmology

The amniotic membrane(AM) is the inner layer of the fetal membranes and consist of 3 different layers: the epithelium, basement membrane and stroma which further consists of three contiguous but distinct layers: the inner compact layer, middle fibroblast layer and the outermost spongy layer. The AM has been shown to have anti-inflammatory, anti-fibrotic, anti-angiogenic as well as anti-microbial properties. Also because of its transparent structure, lack of immunogenicity and the ability to provide an excellent substrate for growth, migration and adhesion of epithelial corneal and conjunctival cells, it is being used increasingly for ocular surface reconstruction in a variety of ocular pathologies including corneal disorders associated with limbal stem cell deficiency, surgeries for conjunctival reconstruction, as a carrier for ex vivo expansion of limbal epithelial cells, glaucoma surgeries and sceral melts and perforations. However indiscriminate use of human AM needs to be discouraged as complications though infrequent can occur. These include risk of transmission of bacterial, viral or fungal infections to the recipient if the donors are not adequately screened for communicable diseases, if the membrane is not processed under sterile condi-tions or if storage is improper. Optimal outcomes can be achieved only with meticulous case selection. This review explores the ever expanding ophthalmological indications for the use of human AM.

Studies of a pedigree with limbal dermoid cyst

AIM: To study clinical features and gene mutations within the paired-like homeodomain transcription factor 2 (PITX2) gene in a pedigree of bilateral limbal dermoids. METHODS: Complete eye examinations have been performed on each individual of the family. Exons of paired-like homeodomain transcription factor 2 ( PITX2)were amplified by polymerase chain reaction, sequenced, and compared with a reference database. RESULTS: We described the phenotype, clinic findings in a family with two affected members. The masses of the proband's eyes were excised surgically demonstrating a dermoid cyst by histopathological examination. No mutation was detected in the gene PITX2 in this pedigree. CONCLUSION: A family of limbal dermoid cyst was reported. In addition, no pathogenic sequence variations were found in PITX2, indicating that this phenotype in this family is a distinctive entity.

Cryopreserved limbal lamellar keratoplasty for peripheral corneal and limbal reconstruction

This study aimed to evaluate the outcomes and described the recovery process of cryopreserved limbal lamellar keratoplasty（CLLK） for peripheral corneal and limbal diseases. Thirteen eyes of 12 patients with a mean age of 41±23.9 y were included. The average follow-up was 12.1±5.6 mo. Stable ocular surface was achieved in all eyes at last follow-up. Epithelialization originated from both recipient and graft in 9 eyes. We conclude that CLLK compensates for the shortage of donor corneas and cryopreserved limbal grafts provide epithelialization sources in ocular surface reconstruction.

Effects of Ocular Parameters on Medial Rectus Faden Operation with Recession for Esotropia

Background: In the treatment of infantile and accommodative esotopia medial rectus (MR) recession combined posterior fixation suture (Faden operation) can be used. But, there is very limited literature on effect of ocular parameters (axial length, medial rectus width and the distance of medial rectus insertion to limbus) to this operation. Objective: To evaluate effects of ocular parameters on medial rectus Faden operations with recession for esotropia. Material and Methods: In this retrospective study, 38 patients (57 eyes) who underwent Faden operation with unilateral or bilateral recession (4 - 4.5 mm) on medial rectus were divided into three groups according to axial length, medial rectus width and the distance of medial rectus insertion to limbus. Preoperative and postoperative deviations compared. Results: 11 cases were infantile esotropia, 46 cases were acquired esotropia. Female/male rate was 19/19. The mean preoperative amount of esotropia at near was 49.95 ± 17.36 prism diopters (PD) and postoperative 1 week 11.77 ± 11.14 PD, 1 month 12.02 ± 11.52 PD and 6 months 9.46 ± 10.19 PD. The mean preoperative amount of esotropia at distance was 38.84 ± 19.03 PD and postoperative 1 week 7.25 ± 11.29 PD, 1 month 6.54 ± 10.52 PD and 6 months 4.40 ± 9.08 PD. Due to axial length, in shorter eyes, the decrease in mean post-operative deviation was statistically significant. Due to medial rectus width and the distance of medial rectus insertion, there was no statistically significant difference. Conclusions: Axial length has an effect on medial rectus Faden operations with recession but medial rectus width and medial rectus insertion distance from limbus do not.

Transplantation of corneal stem cells cultured on amniotic membrane for corneal burn: experimental and clinical study

OBJECTIVE: To investigate the proliferation and differentiation of cultured corneal stem cells and determine the effect of corneal stem cells cultured on amniotic membranes on the limbal area for treating corneal burns. METHODS: The proliferation and differentiation of corneal stem cells in vitro had been examined using colony-forming efficiency and immunohistochemistry. The stem cells had been cultured on amniotic membranes and transplanted to the limbal area for treating corneal burns. RESULTS: Corneal stem cells had a high proliferation capacity in primary and first passage, cytokeratin 3 was not expressed in primary culture but partly in first passage. The stem cells could proliferate to form cell layer on an amniotic membrane. When transplanted, stem cells could survive on limbus. After transplantation, ocular inflammation resolved, the cornea re-epithelialized, the stromal opacity reduced, the superficial neovascularity was lessened and the conjunctival fornix re-established. CONCLUSIONS: Ocular surface conditions could be improved by allograft of corneal stem cells cultured on amniotic membranes.

A new rat model of glaucoma induced by intracameral injection of silicone oil and electrocoagulation of limbal vessels

Background A satisfied glaucoma model is absent now.The aim of this study was to evaluate the effect of a combination of intracameral injection of silicone oil and electrocoagulation of corneal limbal vessels and episcleral veins in the rats to establish glaucoma model.Methods Operation was performed in each of the left eyes of 90 adult male rats.Right eyes were used as controls.Measurement of intraocular pressure （IOP） was performed with an applanation tonometer （Tong-Pen）.Retinal ganglion cells （RGCs） were retrogradely labeled by applying FluoroGold onto the bilateral superior colliculus.Results During the follow-up （24 weeks）,the lOP of the study eyes was significantly higher （P〈0.05） than the control eyes （at final examination,IOP of control eyes was （13.4±1.0） mmHg and lOP of study eyes was （16.1±1.8） mmHg）.Correspondingly,at 24 weeks after operation,the RGCs density of the study eyes （2286.11±290.45/mm^2） was significantly lower than the control eyes （2626.46±164.85/mm^2,P〈0.01）.In the operated eyes,histological examination showed excavation of optic disc and increased neuroglial cells in the optic nerve,reduced thickness of retina and diminution of retinal ganglion cells,and atrophy of ciliary body and iris.Notably,the anterior chamber angle of the operated eye remained open.Conclusions A combination of intracameral injection of silicone oil and electrocoagulation of comeal limbal vessels and episcleral veins may establish a reliable glaucoma model for further research.