Amniotic membrane inhibits squamous metaplasia of human conjunctival epithelium

Ozone exposure affects corneal epithelial fate by promoting mtDNA leakage and cGAS/STING activation

Ozone is a common air pollutant associated with various human diseases. The human ocular surface is frequently exposed to ozone in the troposphere, but the mechanisms by which ozone affects the ocular surface health remain unclear. This study aimed to establish a mouse model to investigate the effects of ozone exposure on the ocular surface and the corneal epithelium. The findings revealed that ozone exposure disrupted corneal epithelial homeostasis and differentiation, resulting in corneal squamous metaplasia. Further, ozone exposure induced oxidative damage and cytoplasmic leakage of mitochondrial DNA (mtDNA), thereby activating the cGAS/STING signaling pathway. The activation of the cGAS/STING signaling pathway triggered the activation of downstream NF-κB and TRAF6 signaling pathways, causing corneal inflammation, thereby promoting corneal inflammation and squamous metaplasia. Finally, C-176, a selective STING inhibitor, effectively prevented and treated corneal inflammation and squamous metaplasia caused by ozone exposure. This study revealed the role of mtDNA leakage-mediated cGAS/STING activation in corneal squamous epithelial metaplasia caused by ozone exposure. It also depicted the abnormal expression pattern of corneal epithelial keratin using three-dimensional images, providing new targets and strategies for preventing and treating corneal squamous metaplasia and other ocular surface diseases.

Safety and efficacy of intense pulsed light in the treatment of severe chronic ocular graft-versus-host disease

OBJECTIVE

To investigate the safety and efficacy of intense pulsed light (IPL) in the treatment of severe chronic ocular graft-versus-host disease (coGVHD).

METHODS

A prospective cohort study. Seventeen patients with severe coGVHD were selected for inclusion in this study. All subjects were treated with IPL every fortnight together with conventional treatment, observation time points were pre-treatment (W0), 4 weeks post-treatment (W4), 8 weeks post-treatment (W8) and 12 weeks post-treatment (W12). Dry eye related examinations include Tear meniscus height (TMH), Non-invasive break-up time (NIBUT), Schirmer I test, Tear film lipid layer thickness (LLT), Ocular surface staining (OSS) and assessment of meibomian gland. Corneal epithelial cell morphology and inflammatory cell infiltration were analyzed by corneal confocal microscopy, while goblet cell density and squamous epithelial grade were assessed by conjunctival imprinted cytology.

RESULTS

Patients did not experience any adverse reactions during the follow-up period. All subjects showed significant improvement in clinical symptoms and most signs after IPL treatment. The corneal confocal microscopy showed that the number of dendritic cells infiltrates in the corneal stroma was significantly reduced after IPL treatment (p < 0.001). Conjunctival blot cytology suggested an increase in the number of conjunctival goblet cells from 5.12 ± 2.71 cells/mm2 before treatment to 22.00 ± 4.58 cells/mm2 after treatment, with a statistically significant difference (p < 0.001). An improvement in conjunctival epithelial cell morphology and a decrease in squamous epithelial grade was also observed.

CONCLUSIONS

IPL treatment can effectively increase tear film stability in patients with severe coGVHD without significant side effects.

Mechanobiology of conjunctival epithelial cells exposed to wall shear stresses

The human conjunctival epithelial cells (HCEC) line the inner sides of the eyelids and the anterior part of the sclera. They include goblet cells that secret mucus into the tear film that protects the ocular surface. The conjunctival epithelium is subjected to mechano-physical stimuli due to eyelid movement during blinking, during wiping and rubbing the eyes, and when exposed to wind and air currents. We cultured primary HCEC under air-liquid interface (ALI) conditions in custom-designed wells that can be disassembled for installation of the in vitro model in a flow chamber. We exposed the HCEC after ALI culture of 8-10 days to steady and oscillatory airflows. The in vitro model of HCEC was exposed to steady wall shear stresses (sWSS) of 0.5 and 1.0 dyne/cm² for lengths of 30 and 60 min and to oscillatory wall shear stresses (oWSS) of 0.5 and 0.77 dyne/cm² amplitudes for a length of 10 min. Cytoskeletal alterations and MUC5AC mucin secretion in response to WSS were investigated using immunohistochemically fluorescent staining and enzyme-linked lectin assay (ELLA), respectively. The results revealed that both exposure times and sWSS values increased the polymerization of F-actin filaments while mucin secretion decreased. However, after a recovery of 24 h in the incubator we observed a decrease of F-actin fibers and mucin secretion only for exposure of 30 min. The length of exposure was more influential on cytoskeletal alterations than the level of sWSS. The very small effect of sWSS on mucin secretion is most likely related to the much smaller amount of goblet cell than in other mucus-secreting tissue. The results for both oWSS amplitudes revealed similar trends regarding F-actin and mucin secretion. Immediately post-exposure we observed an increase in polymerization of F-actin filaments while mucin secretion decreased. However, after 24-h recovery we observed that both F-actin and mucin secretion returned to the same values as for unexposed cultures. The results of this study suggest that WSS should be considered while exploring the physiological characteristics of HCEC.

Effectiveness and Safety of Trabeculectomy along with Amniotic Membrane Transplantation on Glaucoma: A Systematic Review

Purpose

To determine the effectiveness and safety of trabeculectomy along with amniotic membrane transplantation (AMT) for glaucoma.

Methods

This systematic review was performed using RevMan 5.3. We searched PubMed, EMBASE, and the Cochrane Library and included studies published until September 2019. The treatment group included patients with AMT and trabeculectomy (group A), and the control group had only trabeculectomy (group B). We only included randomized controlled trials. The outcomes were intraocular pressure (IOP), complete success rate, number of antiglaucoma medications, and complications.

Results

Five studies, including 174 eyes (87 eyes in the AMT group and 87 eyes in the control group), were eligible in this review. The parameters had no significant difference in heterogeneity between the AMT and control groups preoperatively. In the AMT group, the mean IOP was significantly lower at 3 and 12 months after operation (P < 0.0001 and P = 0.02, respectively), while the number of complete successes in the AMT group was significantly higher at 6 and 12 months (P = 0.02 and P = 0.003, respectively) compared with the control group. Complications, including a flat anterior chamber and hyphema, appeared to be decreased in the AMT group compared to the control group (P = 0.02 and P = 0.02, respectively). No differences were observed in the number of antiglaucoma medications, hypotony, encapsulated bleb, or choroidal detachment.

Conclusion

Compared with only trabeculectomy, it is more efficient and safer to add AMT to trabeculectomy during glaucoma filtering surgery.

An experimental study of amniotic lacrimal duct stents in the treatment of perimenopausal female rabbits with dry eye

The aim of the present study was to investigate the effects of an amniotic membrane lacrimal stent in the treatment of dry eye syndrome in a perimenopausal rabbit model. In total, 48 healthy female rabbits were randomly divided into four groups (12 rabbits/group): Group A, sham-operated group; group B, negative control group; group C, sham-implantation group; and group D, implantation with amniotic membrane lacrimal stents. A Schirmer I test (SIT), corneal fluorescein staining, optical coherence tomography angiography and corneal confocal microscopy were conducted and the biomechanical properties of the amniotic membrane were measured prior to and 2, 4 and 6 weeks after the operations. There were marked differences in the amount of tear secretion and the SIT following the operation compared with prior to the operation. The amount of tear secretion of group B and C was significantly reduced (F=8.894; P=0.0017). Compared with groups A, B and C, group D demonstrated a significant increase in the amount of tear secretion and a significant reduction in SIT (P<0.05). However, there was no statistical difference between the tear secretion of the A, B and C groups (P>0.05). The cornea epithelial of groups A and D was significantly thinner compared with groups B and C. The superior part [superior temporal (ST)5, superior (S)5, superior nasal (SN)5, ST6, S6 and SN6] was significantly thinner compared with the central part of the cornea epithelium. The corneal epithelia of all groups were thin in the center and thick at the edge. At 6 weeks after the operation, group D exhibited a markedly decreased number of anterior stromal luminescent cells, compared with groups A, B and C. Furthermore, the bending degree of corneal stromal neural trunks was significantly improved, and the density, branches and curvature of corneal epithelium sub-basal nerves ameliorated to a certain extent (P<0.05). Amniotic membrane lacrimal stents demonstrated specific therapeutic effects on dry eye in perimenopausal female rabbits.

Tissue remodeling after ocular surface reconstruction with denuded amniotic membrane

Amniotic membrane (AM) has been widely used as a temporary or permanent graft in the treatment of various ocular surface diseases. In this study, we compared the epithelial wound healing and tissue remodeling after ocular surface reconstruction with intact amniotic membrane (iAM) or denuded amniotic membrane (dAM). Partial limbal and bulbar conjunctival removal was performed on New Zealand rabbits followed by transplantation of cryo-preserved human iAM or dAM. In vivo observation showed that the epithelial ingrowth was faster on dAM compared to iAM after AM transplantation. Histological observation showed prominent epithelial stratification and increased goblet cell number on dAM after 2 weeks of follow up. Collagen VII degraded in dAM within 2 weeks, while remained in iAM even after 3 weeks. The number of macrophages and α-SMA positive cells in the stroma of remodelized conjunctiva in the dAM transplantation group was considerably less. In conclusion, dAM facilitates epithelial repopulation and goblet cell differentiation, further reduces inflammation and scar formation during conjunctival and corneal limbal reconstruction.

An engineered human conjunctival-like tissue to study ocular surface inflammatory diseases

The aim of this study was to develop a three-dimensional model of the human conjunctiva that can be used to perform physiology and pathophysiology experiments. Fibrin-based matrices (derived from human plasma or plasma cryoprecipitate) were used as scaffolds, and primary cells were obtained from conjunctival tissue. Conjunctival constructs were analyzed by immunofluorescent staining and scanning electron microscopy and cell proliferation was measured with alamarBlue® assay. After characterizing the constructs, four different experimental conditions were analyzed in cryoprecipitate matrices: controls, air-lifted cultures (to increase cell stratification), partially desiccated cultures (to mimic dry eye disease), and IL-13-treated cultures (to mimic allergy). Constructs were stained with hematoxylin/eosin to observe changes in morphology. High molecular weight glycoconjugates were identified by HPA staining. MUC5AC and IL-6 secretion was evaluated by ELISA. The fibrin-based matrices supported conjunctival cell growth. Epithelial cells grew on the surface of the scaffolds and underwent stratification that increased over time. These cells had microvilli, which suggests cell polarization and functionality. Fibroblasts were integrated in the scaffold and showed elongated shape. Compared to controls, air-lifted construct had increased epithelial stratification and upregulated MUC5AC secretion. Increased MUC5AC secretion also occurred in partially desiccated and IL-13-treated cultures. The inflammatory status of cells was evaluated by IL-6 levels which were increased in air-lifted and partially desiccated cultures, but not in IL-13-treated ones. In conclusion, we have developed a new three-dimensional model of human conjunctiva that can be used to study ocular surface inflammatory diseases.

Effect of Amniotic Membrane Suspension (AMS) and Amniotic Membrane Homogenate (AMH) on Human Corneal Epithelial Cell Viability, Migration and Proliferation In Vitro

PURPOSE

To analyze the effects of different concentrations of amniotic membrane suspension (AMS) or amniotic membrane homogenate (AMH) on human corneal epithelial cell (HCEC) viability, migration and proliferation.

METHODS

Amniotic membranes (AMs) of 13 placentas were prepared and stored at -80°C. For AMS preparation, following de-freezing, AM pieces were inserted in six-well plates and 5 ml Dulbecco's Modified Eagle's Medium (DMEM)/F12 (with 5% fetal bovine serum, FBS) per gram tissue was added for 96 h. After removal of the AM, the remaining supernatant was collected for experiments. For AMH preparation, following de-freezing, AMs were homogenized in liquid nitrogen and 5 ml DMEM/F12 (with 5% FBS) per gram tissue was added. Following centrifugation, the supernatant was collected for experiments. HCECs were expanded and incubated in DMEM/F12, 5% FBS supplemented by 15%, 30% or 100% AMS or 15% or 30% AMH. Viability was analyzed using Cell Proliferation Kit XTT, migration using wound healing assay and proliferation by the cell proliferation ELISA BrdU kit.

RESULTS

HCEC viability remained unchanged using 15% or 30% AMS (p = 1.0 for both); however, it decreased significantly using 100% AMS (p < 0.001) or 15% (p = 0.041) or 30% AMH (p < 0.001), compared to controls. Using 15% or 30% AMS, HCEC migration increased significantly (p < 0.001 for both). Using 15% or 30% AMH (p = 0.153; p = 0.083), HCEC migration remained unchanged and 100% AMS inhibited HCEC migration (p < 0.001). Next, 15% and 30% AMS had no effect on HCEC proliferation (p = 0.454 and p = 0.119), but 100% AMS (p < 0.001) and 15% (p = 0.002) and 30% AMH (p = 0.001) inhibited HCEC proliferation significantly.

CONCLUSION

With unchanged HCEC viability and proliferation and increased HCEC migration, 15% and 30% AMS application seems to be the most appropriate method to support epithelial healing.

An Ultra-thin Amniotic Membrane as Carrier in Corneal Epithelium Tissue-Engineering

Amniotic membranes (AMs) are widely used as a corneal epithelial tissue carrier in reconstruction surgery. However, the engineered tissue transparency is low due to the translucent thick underlying AM stroma. To overcome this drawback, we developed an ultra-thin AM (UAM) by using collagenase IV to strip away from the epithelial denuded AM (DAM) some of the stroma. By thinning the stroma to about 30 μm, its moist and dry forms were rendered acellular, optically clear and its collagen framework became compacted and inerratic. Engineered rabbit corneal epithelial cell (RCEC) sheets generated through expansion of limbal epithelial cells on UAM were more transparent and thicker than those expanded on DAM. Moreover, ΔNp63 and ABCG2 gene expression was greater in tissue engineered cell sheets expanded on UAM than on DAM. Furthermore, 2 weeks after surgery, the cornea grafted with UAM based cell sheets showed higher transparency and more stratified epithelium than the cornea grafted with DAM based cell sheets. Taken together, tissue engineered corneal epithelium generated on UAM has a preferable outcome because the transplanted tissue is more transparent and better resembles the phenotype of the native tissue than that obtained by using DAM for this procedure. UAM preserves compact layer of the amniotic membrane and maybe an ideal substrate for corneal epithelial tissue engineering.

Concise Review: Comparison of Culture Membranes Used for Tissue Engineered Conjunctival Epithelial Equivalents

The conjunctival epithelium plays an important role in ensuring the optical clarity of the cornea by providing lubrication to maintain a smooth, refractive surface, by producing mucins critical for tear film stability and by protecting against mechanical stress and infectious agents. A large number of disorders can lead to scarring of the conjunctiva through chronic conjunctival inflammation. For controlling complications of conjunctival scarring, surgery can be considered. Surgical treatment of symblepharon includes removal of the scar tissue to reestablish the deep fornix. The surgical defect is then covered by the application of a tissue substitute. One obvious limiting factor when using autografts is the size of the defect to be covered, as the amount of healthy conjunctiva is scarce. These limitations have led scientists to develop tissue engineered conjunctival equivalents. A tissue engineered conjunctival epithelial equivalent needs to be easily manipulated surgically, not cause an inflammatory reaction and be biocompatible. This review summarizes the various substrates and membranes that have been used to culture conjunctival epithelial cells during the last three decades. Future avenues for developing tissue engineered conjunctiva are discussed.

Proprotein convertase 5/6a is associated with bone morphogenetic protein-2-induced squamous cell differentiation

Squamous metaplasia in airway epithelium is a pathological process arising from abnormal remodeling/repair responses to injury. Proteolytic maturation of many growth and differentiation factors involved in tissue remodeling is controlled by proprotein convertases (PCs). However, the role of these convertases in airway remodeling remains poorly understood. Using a retinoic acid deficiency-induced squamous metaplasia model of cultured human nasal epithelial cells (HNECs), we observed a significant increase in the expression of PC5/6A, a PC member, and bone morphogenetic protein-2 (BMP-2), a candidate substrate for PC5/6A. Specific lentiviral short hairpin RNA-mediated PC5/6A knockdown decreased BMP-2 expression and maturation, decreased expression of squamous cell markers, and increased expression of ciliated cell markers. Decanoyl-Arg-Val-Lys-Arg-chloromethylketone (Dec-RVKR-CMK), a PC inhibitor, and LDN-193189, a BMP receptor inhibitor, suppressed squamous differentiation, promoted mucociliary differentiation, and down-regulated the BMP-2/Smad1/5/8/p38 signaling pathways. Dec-RVKR-CMK also decreased expression of PC5/6A, but not furin, another PC member, suggesting the involvement of PC5/6A in squamous differentiation of HNECs. Overexpression of PC5/6A and BMP-2 in the human nasal epithelial cell line RPMI-2650 demonstrated that PC5/6A can activate BMP-2. Under retinoic acid-sufficient culture conditions for mucociliary differentiation of HNECs, short-term expression of PC5/6A by the adenovirus system and addition of exogenous BMP-2 induced squamous differentiation. Furthermore, PC5/6A and BMP-2 were highly expressed in metaplastic squamous epithelium of human nasal polyps. Taken together, PC5/6A is involved in squamous differentiation of HNECs, possibly through up-regulation of the BMP-2/pSmad1/5/8/p38 signaling pathway, pointing to a potential therapeutic target for the prevention of chronic airway diseases that exhibit squamous metaplasia.

Effects of Honghua preserved amniotic membrane on scar healing in experimental glaucoma surgery

AIM

To investigate the efficacy and safety of Honghua preserved amniotic membrane (AM) for preventing scar formation of the filtering bleb in a rabbit model of glaucoma trabeculectomy surgery.

METHODS

Totally 36 rabbits (36 eyes) were randomly divided into 3 groups: the experimental group (ocular trabeculectomy in combination with Honghua preserved AM transplantation), the control group (ocular trabeculectomy surgery in combination with AM implantation), and the blank group (single trabeculectomy). Clinical observations [including intraocular pressure (IOP), filtering blebs and complications], Masson-Trichrome staining, real-time quantitative reverse transcription-polymerase chain reaction (real-time PCR), Western blot were performed on different time points (D1, D7, D14, D21 and D56) after the surgery.

RESULTS

After operated for 14d, there were statistically significant differences in the filtering blebs compared to the situation before operation (P<0.05), whereas no statistically difference on that among three groups (P>0.05). After 21d, the IOP of experimental group was lowest (P<0.05). There was significant difference between control group and blank group (P<0.05). On postoperative D14, the mean number of fibroblasts in the experimental group was significantly lower (40.6±10.2) compared to those in the control group (54.4±10.8) and blank group (68.2±11.6) (P<0.05, respectively). The mean numbers of the macrophage in the experimental and control groups were respcitively significantly lower versus the blank group (P<0.05, P<0.05, respectively). Compared to that in blank group, the level of transforming growth factor-β (TGF-β1) expression in sclera and conjunctival areas was reduced in the experimental and control groups on protein and mRNA level (P<0.05), but not significant difference between these two groups (P>0.05).

CONCLUSION

The trabeculectory surgery with Honghua preserved AM can control IOP, sustain the functional filtration bleb, inhibit the proliferation of fibroblasts and open the filtrating pathway on the rabbit glaucoma models.

Hypoxia affects in vitro proliferation and differentiation of mouse corneal epithelial progenitor cell

This study was to investigate the proliferation and differentiation of mouse corneal epithelial progenitor cell in hypoxic airlift culture. Mouse corneal epithelial progenitor cell line progenitor cells were cultured under airlift with normoxic and hypoxic conditions for various durations up to 2 wk. Under normoxic conditions when exposed to air, the hyperproliferation and abnormal epidermal-like differentiation of mouse corneal epithelium was induced, whereas when exposed to air under hypoxic conditions, although we observed augmented proliferation, the abnormal differentiation was inhibited. The mechanism by which hypoxia prevents abnormal differentiation may involve downregulation of Wnt signaling pathways, which were inhibited in cells cultured with hypoxic airlift technique. In conclusion, hypoxia can prevent abnormal differentiation while enhancing the proliferation of corneal epithelial cells by blocking Wnt/β-catenin signaling pathway.