TGFbeta pathobiology in the eye

Zwitterionic modified and freeze-thaw reinforced foldable hydrogel as intraocular lens for posterior capsule opacification prevention

Posterior capsule opacification (PCO) is a predominant postoperative complication, often leading to visual impairment due to the aberrant proliferation and adhesion of lens epithelial cells (LECs) and protein precipitates subsequent to intraocular lens (IOL) implantation. To address this clinical issue, a foldable and antifouling sharp-edged IOL implant based on naturally-derived cellulose hydrogel is synthesized. The mechanical strength and transparency of the hydrogel is enhanced via repeated freeze-thaw (FT) cycles. The incorporated zwitterionic modifications can remarkably prevent the incidence of PCO by exhibiting proteins repulsion and cell anti-adhesion properties. The graft of dopamine onto both the haptic and the periphery of the posterior surface ensures the adhesion of the hydrogel to the posterior capsule and impedes the migration of LECs without compromising transparency. In in vivo study, the zwitterionic modified foldable hydrogel exhibits uveal and capsular biocompatibility synchronously with no signs of inflammatory response and prevent PCO formation, better than that of commercialized and PEG-modified IOL. With foldability, endurability, antifouling effect, and adhesive to posterior capsule, the reported hydrogel featuring heterogeneous surface design displays great potential to eradicate PCO and attain post-operative efficacy after cataract surgery.

Evaluation of nintedanib efficacy: Attenuating the lens fibrosis in vitro and vivo

PURPOSE

Organ fibrosis is a huge challenge in clinic. There are no drugs for fibrotic cataracts treatments in clinic. Nintedanib is approved by the FDA for pulmonary fibrosis treatments. This study aims to investigate the efficacy and mechanism of nintedanib on fibrotic cataracts.

METHODS

Drug efficacy was validated through TGFβ2-induced cell models and injury-induced anterior subcapsular cataract (ASC) mice. A slit lamp and the eosin staining technique were applied to access the degree of capsular fibrosis. The CCK-8 assay was used to evaluate the toxicity and anti-proliferation ability of the drug. The cell migration was determined by wound healing assay and transwell assay. The anti-epithelial mesenchymal transition (EMT) and anti-fibrosis efficacy were evaluated by qRT-PCR, immunoblot, and immunofluorescence. The inhibition of nintedanib to signaling pathways was certified by immunoblot.

RESULTS

Nintedanib inhibited the migration and proliferation of TGFβ2-induced cell models. Nintedanib can also repress the EMT and fibrosis of the lens epithelial cells. The intracameral injection of nintedanib can also allay the anterior subcapsular opacification in ASC mice. The TGFβ2/ Smad and non-Smad signaling pathways can be blocked by nintedanib in vitro and in vivo.

CONCLUSION

Nintedanib alleviates fibrotic cataracts by suppressing the TGFβ2/ Smad and non-Smad signaling pathways. Nintedanib is a potential drug for lens fibrosis.

Revealing the Potency of Growth Factors in Bovine Colostrum

Colostrum is a nutritious milk synthesized by mammals during the postpartum period, and its rich bioactive components has led to a global increase in the consumption of bovine colostrum as a supplement. Bovine colostrum contains key components such as immunoglobulins, oligosaccharides, lactoferrin and lysozyme. It is a special supplement source due to its natural, high bioavailability and high concentrations of growth factors. Growth factors are critical to many physiological functions, and considering its presence in the colostrum, further research must be conducted on its safe application in many bodily disorders. Growth factors contribute to wound healing, muscle and bone development, and supporting growth in children. Additionally, the molecular mechanisms have been explored, highlighting the growth factors roles in cell proliferation, tissue regeneration, and the regulation of immune responses. These findings are crucial for understanding the potential health effects of bovine colostrum, ensuring its safe use, and forming a basis for future clinical applications. This review article examines the growth factors concentration in bovine colostrum, their benefits, clinical studies, and molecular mechanisms.

Potential therapeutic effects of peroxisome proliferator-activated receptors on corneal diseases

The cornea is an avascular tissue in the eye that has multiple functions in the eye to maintain clear vision which can significantly impair one's vision when subjected to damage. Peroxisome proliferator-activated receptors (PPARs), a family of nuclear receptor proteins comprising three different peroxisome proliferator-activated receptor (PPAR) isoforms, namely, PPAR alpha (α), PPAR gamma (γ), and PPAR delta (δ), have emerged as potential therapeutic targets for treating corneal diseases. In this review, we summarised the current literature on the therapeutic effects of PPAR agents on corneal diseases. We discussed the role of PPARs in the modulation of corneal wound healing, suppression of corneal inflammation, neovascularisation, fibrosis, stimulation of corneal nerve regeneration, and amelioration of dry eye by inhibiting oxidative stress within the cornea. We also discussed the underlying mechanisms of these therapeutic effects. Future clinical trials are warranted to further attest to the clinical therapeutic efficacy.

Lack of Elevated Expression of TGFβ3 Contributes to the Delay of Epithelial Wound Healing in Diabetic Corneas

Purpose

To investigate the mechanisms underlying the differential roles of TGFβ1 and TGFβ3 in accelerating corneal epithelial wound healing (CEWH) in diabetic (DM) corneas, with normoglycemia (NL) corneas as the control.

Methods

Two types of diabetic mice, human corneal organ cultures, mouse corneal epithelial progenitor cell lines, and bone marrow-derived macrophages (BMDMs) were employed to assess the effects of TGFβ1 and TGFβ3 on CEWH, utilizing quantitative PCR, western blotting, ELISA, and whole-mount confocal microscopy.

Results

Epithelial debridement led to an increased expression of TGFβ1 and TGFβ3 in cultured human NL corneas, but only TGFβ1 in DM corneas. TGFβ1 and TGFβ3 inhibition was significantly impeded, but exogenous TGFβ1 and, more potently, TGFβ3 promoted CEWH in cultured TKE2 cells and in NL and DM C57BL6 mouse corneas. Wounding induced similar levels of p-SMAD2/SMAD3 in NL and DM corneas but weaker ERK1/2, Akt, and EGFR phosphorylation in DM corneas compared to NL corneas. Whereas TGFβ1 augmented SMAD2/SMAD3 phosphorylation, TGFβ3 preferentially activated ERK, PI3K, and EGFR in healing DM corneas. Furthermore, TGFβ1 and TGFβ3 differentially regulated the expression of S100a9, PAI-1, uPA/tPA, and CCL3 in healing NL and DM corneas. Finally, TGFβ1 induced the expression of M1 macrophage markers iNOS, CD86, and CTGF, whereas TGFβ3 promoted the expression of M2 markers CD206 and NGF in BMDMs from db/db or db/+ mice.

Conclusions

Hyperglycemia disrupts the balanced expression of TGFβ3/TGFβ1, resulting in delayed CEWH, including impaired sensory nerve regeneration in the cornea. Supplementing TGFβ3 in DM wounds may hold therapeutic potential for accelerating delayed wound healing in diabetic patients.

Dental caries as a health risk for visual acuity in relation to salivary transforming growth factor beta-1 among students aged 8-10 years: A cross-sectional study

Background

Dental caries and an impairment in visual acuity (VA) may both be caused by a variety of risk factors. Various conditions of the eye can appear as a consequence of overall inflammation and active dental caries.

Aim

The present study aims to assess dental caries and salivary status by measuring the transforming growth factor beta-1 (TGF-β1) and flow rate between visually impaired students compared with students with normal vision.

Materials and Methods

Research was performed employing a cross-sectional comparative study design conducted among representative 653 students aged 8-10 years at primary schools in Al-Diwaniyah governorate using the Snellen E chart for measuring VA status. Partitioning the students according to the degree of VA into normal students with normal VA of 6/9 or better and students with visual impairment of 6/12 or worse was done. Sub-sample of 180 students was recruited randomly from both groups, age and gender-matched participants for salivary analysis, and dental caries assessment measured by decay, missed, filled index, according to the World Health Organization in 2013.

Results

Out of 653 students, only 70 students suffer from a decrease in VA. Dental caries was more prevalent in those who had a decrease in VA compared with normal groups. For primary teeth decay, missed, filled teeth index (DMFT/dmft), the result was not significant but highly significant for DMFT/dmft. A significant decrease in salivary flow rate and increased salivary TGF-β1 level among visually impaired students was found.

Conclusions

According to the current research, the study population that has impaired VA, dental health status has greatly deteriorated.

GMFB/AKT/TGF-β3 in Müller cells mediated early retinal degeneration in a streptozotocin-induced rat diabetes model

Retinal degeneration, characterized by Müller cell gliosis and photoreceptor apoptosis, is considered an early event in diabetic retinopathy (DR). Our previous study proposed that GMFB may mediate diabetic retinal degeneration. This study identified GMFB as a sensitive and functional gliosis marker for DR. Compared to the wild type (WT) group, Gmfb knockout (KO) significantly improved visual function, attenuated gliosis, reduced the apoptosis of neurons, and decreased the mRNA levels of tumor necrosis factor α (Tnf-α) and interleukin-1β (Il-1β) in diabetic retinas. Tgf-β3 was enriched by hub genes using RNA sequencing in primary WT and KO Müller cells. Gmfb KO significantly upregulated the transforming growth factor (TGF)-β3 protein level via the AKT pathway. The protective effect of TGF-β3 in the vitreous resulted in significantly improved visual function and decreased the number of apoptotic cells in the diabetic retina. The protection of Gmfb KO in primary Müller cells against high glucose (HG)-induced photoreceptor apoptosis was partially counteracted by TGF-β3 antibody and administration of TGFBR1/2 inhibitors. Nuclear receptor subfamily 3 group C member 1 (NR3C1) binds to the promoter region of Gmfb and regulates Gmfb mRNA at the transcriptional level. NR3C1 was increased in the retinas of early diabetic rats but decreased in the retinas of late diabetic rats. N'-[(1E)-(3-Methoxyphenyl)Methylene]-3-Methyl-1H-Pyrazole-5-Carbohydrazide (DS-5) was identified as an inhibitor of GMFB, having a protective role in DR. We demonstrated that GMFB/AKT/TGF-β3 mediated early diabetic retinal degeneration in diabetic rats. This study provides a novel therapeutic strategy for treating retinal degeneration in patients with DR.

Development and Verification of a Novel Three-Dimensional Aqueous Outflow Model for High-Throughput Drug Screening

Distal outflow bleb-forming procedures in ophthalmic surgery expose subconjunctival tissue to inflammatory cytokines present in the aqueous humor, resulting in impaired outflow and, consequently, increased intraocular pressure. Clinically, this manifests as an increased risk of surgical failure often necessitating revision. This study (1) introduces a novel high-throughput screening platform for testing potential anti-fibrotic compounds and (2) assesses the clinical viability of modulating the transforming growth factor beta-SMAD2/3 pathway as a key contributor to post-operative outflow reduction, using the signal transduction inhibitor verteporfin. Human Tenon's capsule fibroblasts (HTCFs) were cultured within a 3D collagen matrix in a microfluidic system modelling aqueous humor drainage. The perfusate was augmented with transforming growth factor beta 1 (TGFβ1), and afferent pressure to the tissue-mimetic was continuously monitored to detect treatment-related pressure elevations. Co-treatment with verteporfin was employed to evaluate its capacity to counteract TGFβ1 induced pressure changes. Immunofluorescent studies were conducted on the tissue-mimetic to corroborate the pressure data with cellular changes. Introduction of TGFβ1 induced treatment-related afferent pressure increase in the tissue-mimetic. HTCFs treated with TGFβ1 displayed visibly enlarged cytoskeletons and stress fiber formation, consistent with myofibroblast transformation. Importantly, verteporfin effectively mitigated these changes, reducing both afferent pressure increases and cytoskeletal alterations. In summary, this study models the pathological filtration bleb response to TGFβ1, while demonstrating verteporfin's effectiveness in ameliorating both functional and cellular changes caused by TGFβ1. These demonstrate modulation of the aforementioned pathway as a potential avenue for addressing post-operative changes and reductions in filtration bleb outflow capacity. Furthermore, the establishment of a high-throughput screening platform offers a valuable pre-animal testing tool for investigating potential compounds to facilitate surgical wound healing.

Lanosterol Synthase Prevents EMT During Lens Epithelial Fibrosis Via Regulating SREBP1

Purpose

Epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) is a predominant pathological process underlying fibrotic cataracts. Here we investigated the role and mechanism of lanosterol synthase (LSS), a key rate-limiting enzyme in sterol biosynthesis, in EMT of LECs.

Methods

Human lens epithelial explants, primary rabbit LECs, and whole rat lenses were treated with TGFβ2. RNA-sequencing was conducted to explore genetic changes during fibrosis of human lens epithelial explants. Loss- and gain-of-function studies were performed in primary LECs to investigate roles and mechanisms of LSS, lanosterol and sterol regulatory element binding transcription protein 1 (SREBP1) in EMT. Rat lenses were applied to evaluate the potential effect of lanosterol on lens fibrosis. Expression of LSS, SREBP1, EMT-related regulators, and markers were analyzed by Western blot, qRT-PCR, or immunofluorescent staining.

Results

LSS and steroid biosynthesis were downregulated in TGFβ2-induced lens fibrosis. LSS inhibition directly triggered EMT by inducing Smad2/3 phosphorylation and nucleus translocation, an overexpression of LSS protected LECs from EMT by inhibiting Smad2/3 activation. Moreover, LSS inhibition decreased the expression of SREBP1, which regulated EMT via intervening TGFβ2/Smad2/3 transduction. Furthermore, lanosterol protected LECs from EMT caused by both TGFβ2 treatment and LSS inhibition via suppressing Smad2/3 activation and maintained lens transparency by preventing fibrotic plaques formation.

Conclusions

We first identified that LSS protected LECs from EMT and played an antifibrotic role to maintain lens transparency. Additionally, lanosterol and sterol biosynthesis regulation might be promising strategies for preventing and treating fibrotic cataracts.

Tenascins and osteopontin in biological response in cornea

The structural composition, integrity and regular curvature of the cornea contribute to the maintenance of its transparency and vision. Disruption of its integrity caused by injury results in scarring, inflammation and neovascularization followed by losses in transparency. These sight compromising effects is caused by dysfunctional corneal resident cell responses induced by the wound healing process. Upregulation of growth factors/cytokines and neuropeptides affect development of aberrant behavior. These factors trigger keratocytes to first transform into activated fibroblasts and then to myofibroblasts. Myofibroblasts express extracellular matrix components for tissue repair and contract the tissue to facilitate wound closure. Proper remodeling following primary repair is critical for restoration of transparency and visual function. Extracellular matrix components contributing to the healing process are divided into two groups; a group of classical tissue structural components and matrix macromolecules that modulate cell behaviors/activities besides being integrated into the matrix structure. The latter components are designated as matricellular proteins. Their functionality is elicited through mechanisms which modulate the scaffold integrity, cell behaviors, activation/inactivation of either growth factors or cytoplasmic signaling regulation. We discuss here the functional roles of matricellular proteins in mediating injury-induced corneal tissue repair. The roles are described of major matricellular proteins, which include tenascin C, tenascin X and osteopontin. Focus is directed towards dealing with their roles in modulating individual activities of wound healing-related growth factors, e. g., transforming growth factor β (TGF β). Modulation of matricellular protein functions could encompass a potential novel strategy to improve the outcome of injury-induced corneal wound healing.

Klotho prevents transforming growth factor-β2-induced senescent-like morphological changes in the retinal pigment epithelium

Degenerative changes of the retinal pigment epithelium (RPE) triggered by transforming growth factor-β2 (TGF-β2) and oxidative stress play a critical role in the progression of age-related macular degeneration (AMD). The expression of α-klotho, an antiaging protein, declines with age, increasing the risk factors for age-related diseases. Here, we investigated the protective effects of soluble α-klotho on TGF-β2-induced RPE degeneration. The morphological changes induced by TGF-β2, including epithelial-mesenchymal transition (EMT), were attenuated in the mouse RPE by the intravitreal injection (IVT) of α-klotho. In ARPE19 cells, EMT and morphological alterations by TGF-β2 were attenuated by co-incubation with α-klotho. TGF-β2 decreased miR-200a accompanied by zinc finger e-box binding homeobox1 (ZEB1) upregulation and EMT, all of which were prevented by α-klotho co-treatment. Inhibitor of miR-200a mimicked TGF-β2-induced morphological changes, which were recovered by ZEP1 silencing, but not by α-klotho, implying the upstream regulation of α-klotho on miR-200a-ZEP1-EMT axis. α-Klotho inhibited receptor binding of TGF-β2, Smad2/3 phosphorylation, extracellular signal-regulated protein kinase 1/2 (ERK1/2)-a mechanistic target of rapamycin (mTOR) activation and oxidative stress via NADPH oxidase 4 (NOX4) upregulation. Furthermore, α-klotho recovered the TGF-β2-induced mitochondrial activation and superoxide generation. Interestingly, TGF-β2 upregulated α-klotho expression in the RPE cells, and genetic suppression of endogenous α-klotho aggravated TGF-β2-induced oxidative stress and EMT. Lastly, α-klotho abrogated senescence-associated signaling molecules and phenotypes induced by long-term incubation with TGF-β2. Hence, our findings indicate that the antiaging α-klotho plays a protective role against EMT and degeneration of the RPE, demonstrating the therapeutic potential for age-related retinal diseases, including the dry type of AMD.

Recurrence of Idiopathic Orbital Inflammation: An 11-year Retrospective Study

PURPOSE

The high recurrence rate of idiopathic orbital inflammation (IOI) has been reported. This study aims to determine existing predictive factors for the recurrence of IOI.

METHODS

This was an 11-year retrospective study with at least a 12-month follow-up. Fifty patients with biopsy-proven IOI admitted between 2006 and 2017 at our tertiary hospital were observed. We compared the clinical characteristics, histopathological profile, and biomarker expressions (mast cell, immunoglobulin G4, tumor necrosis factor-alpha, and transforming growth factor-beta) of 16 patients with recurrence (Group I) and 34 patients with no recurrence (Group II). Statistical comparison and multivariate analysis were performed to establish the predictive factors.

RESULTS

We discovered five recurrence predictive factors: presentation of proptosis (odds ratio [OR] 4.96, 95% confidence interval [CI] 1.36-18.03), visual impairment (OR 15, 95% CI 1.58-142.72), extraocular muscle (EOM) restriction (OR 3.86, 95% CI 1.07-13.94), nonanterior involvement (OR 7.94, 95% CI 1.88-33.5), and corticosteroid (CS) alone treatment (OR 7.20, 95% CI 1.87-27.8). On multivariate analysis, nonanterior involvement and CS alone treatment were validated as predictive factors (area under the curve = 0.807 [95% CI 0.69-0.92]). Histopathological profile and biomarker expressions were not associated with recurrence. However, there was a 22-fold higher recurrence risk for granulomatous-type patients given CS alone treatment.

CONCLUSION

Unlike the five clinical characteristics mentioned, both histopathology and biomarker variables were not associated with recurrence. CS alone treatment for patients with nonanterior involvement or granulomatous type is proven to increase the risk of recurrence. Therefore, we suggest not giving CS without any combination treatment with other modalities for this group of patients.

Loss of TRPV4 Cation Channel Inhibition of Macrophage Infiltration and Neovascularization in a Mouse Cornea

Corneal injury-associated inflammation could induce inward-growing neovascularization from the periphery of the tissue. Such neovascularization could cause stromal opacification and curvature disturbance, and both potentially impair visual function. In this study, we determined the effects of the loss of transient receptor potential vanilloid 4 (TRPV4) expression on the development of neovascularization in the corneal stroma in mice by producing a cauterization injury in the central area of the cornea. New vessels were immunohistochemically labeled with anti-TRPV4 antibodies. TRPV4 gene knockout suppressed the growth of such CD31-labeled neovascularization in association with the suppression of infiltration of macrophages and tissue messenger RNA expression of the vascular endothelial cell growth factor A level. Treatment of cultured vascular endothelial cells with supplementation of HC-067047 (0.1 μM, 1 μM, or 10 μM), a TRPV4 antagonist, attenuated the formation of a tube-like structure with sulforaphane (15 μM, for positive control) that modeled the new vessel formation. Therefore, the TRPV4 signal is involved in injury-induced macrophagic inflammation and neovascularization activity by vascular endothelial cells in a mouse corneal stroma. TRPV4 could be a therapeutic target to prevent unfavorable postinjury neovascularization in the cornea.

Cell derived matrices from bovine corneal endothelial cells as a model to study cellular dysfunction

PURPOSE

Fuchs endothelial corneal dystrophy (FECD) is a progressive corneal disease that impacts the structure and stiffness of the Descemet's membrane (DM), the substratum for corneal endothelial cells (CECs). These structural alterations of the DM could contribute to the loss of the CECs resulting in corneal edema and blindness. Oxidative stress and transforming growth factor-β (TGF-β) pathways have been implicated in endothelial cell loss and endothelial to mesenchymal transition of CECs in FECD. Ascorbic acid (AA) is found at high concentrations in FECD and its impact on CEC survival has been investigated. However, how TGF-β and AA effect the composition and rigidity of the CEC's matrix remains unknown.

METHODS

In this study, we investigated the effect of AA, TGF-β1 and TGF-β3 on the deposition, ultrastructure, stiffness, and composition of the extracellular matrix (ECM) secreted by primary bovine corneal endothelial cells (BCECs).

RESULTS

Immunofluorescence and electron microscopy post-decellularization demonstrated a robust deposition and distinct structure of ECM in response to treatments. AFM measurements showed that the modulus of the matrix in BCECs treated with TGF-β1 and TGF-β3 was significantly lower than the controls. There was no difference in the stiffness of the matrix between the AA-treated cell and controls. Gene Ontology analysis of the proteomics results revealed that AA modulates the oxidative stress pathway in the matrix while TGF-β induces the expression of matrix proteins collagen IV, laminin, and lysyl oxidase homolog 1.

CONCLUSIONS

Molecular pathways identified in this study demonstrate the differential role of soluble factors in the pathogenesis of FECD.

Differential effects of acetylsalicylic acid and mitomycin C on cytokine-induced Tenon's capsule myofibroblast transdifferentiation and activity: Implications for glaucoma surgery

Inflammation-driven scarring is a major contributor to surgical failure after subconjunctival bleb forming glaucoma surgery. The current gold standard anti-scarring adjuvant mitomycin C (MMC) has variable effectiveness and is associated with significant risks. Acetylsalicylic acid (ASA), when delivered locally, repurposes the typically pro-inflammatory cyclooxygenase (COX-2) signaling for the resolution of inflammation and mitigating inflammation-mediated fibrosis. The aim of this study is to compare the effects of ASA and MMC in an in vitro model of subconjunctival scarring. Glaucoma patient-derived Tenon's capsule fibroblasts (HTCFs) were treated with TGFβ1 (2 ng/mL) plus or minus ASA (1600 μg/ml), or MMC (0.05, 0.1, 0.2 mg/mL). In vitro collagen contraction, MTT, LDH, immunofluorescence, and Western blot assays were performed. To elucidate the mechanistic effects of ASA in TGFβ1-induced HTCFs, liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to identify and measure pro-inflammatory and pro-resolving lipid mediator secretion. ASA was at least as effective as MMC in reducing TGFβ1-induced HTCF-mediated collagen contraction, metabolic activity, and pro-fibrotic protein expression, with less cytotoxicity. Within cytokine-activated HTCFs, ASA significantly impaired secretion of pro-inflammatory lipid mediators prostaglandin E2 and 6-keto-prostaglandin F1α and significantly increased secretion of the pro-resolving mediators 5-hydroxyeicosatetraenoic acid (HETE), 15-HETE and 18-hydroxyeicosapentaenoic acid (HEPE). ASA reduces cytokine-induced myofibroblast transdifferentiation in HTCFs, being non-inferior to MMC in vitro. ASA's effects are associated with a unique lipid mediator expression profile, suggesting that the ASA-induced resolution of inflammation may be a promising strategy to mitigate inflammation-mediated scarring and could offer a novel alternative as a surgical adjuvant.

Sphingosine-1-phosphate and ceramide-1-phosphate promote migration, pro-inflammatory and pro-fibrotic responses in retinal pigment epithelium cells

Retinal pigment epithelium (RPE) cells, essential for preserving retina homeostasis, also contribute to the development of retina proliferative diseases, through their exacerbated migration, epithelial to mesenchymal transition (EMT) and inflammatory response. Uncovering the mechanisms inducing these changes is crucial for designing effective treatments for these pathologies. Sphingosine-1-phosphate (S1P) and ceramide-1-phosphate (C1P) are bioactive sphingolipids that promote migration and inflammation in several cell types; we recently established that they stimulate the migration of retina Müller glial cells (Simón et al., 2015; Vera et al., 2021). We here analyzed whether S1P and C1P regulate migration, inflammation and EMT in RPE cells. We cultured two human RPE cell lines, ARPE-19 and D407 cells, and supplemented them with either 5 μM S1P or 10 μM C1P, or their vehicles, for 24 h. Analysis of cell migration by the scratch wound assay showed that S1P addition significantly enhanced migration in both cell lines. Pre-treatment with W146 and BML-241, antagonists for S1P receptor 1 (S1P1) and 3 (S1P3), respectively, blocked exogenous S1P-induced migration. Inhibiting sphingosine kinase 1 (SphK1), the enzyme involved in S1P synthesis, significantly reduced cell migration and exogenous S1P only partially restored it. Addition of C1P markedly stimulated cell migration. Whereas inhibiting C1P synthesis did not affect C1P-induced migration, inhibiting S1P synthesis strikingly decreased it; noteworthy, addition of C1P promoted the transcription of SphK1. These results suggest that S1P and C1P stimulate RPE cell migration and their effect requires S1P endogenous synthesis. Both S1P and C1P increase the transcription of pro-inflammatory cytokines IL-6 and IL-8, and of EMT marker α-smooth muscle actin (α-SMA) in ARPE-19 cells. Collectively, our results suggest new roles for S1P and C1P in the regulation of RPE cell migration and inflammation; since the deregulation of sphingolipid metabolism is involved in several proliferative retinopathies, targeting their metabolism might provide new tools for treating these pathologies.

Initial Healing Effects of Platelet-Rich Plasma (PRP) Gel and Platelet-Rich Fibrin (PRF) in the Deep Corneal Wound in Rabbits

Platelet concentrates (PCs), including platelet-rich plasma (PRP) gel and platelet-rich fibrin (PRF), are autologous blood-derived biomaterials containing numerous growth factors. This study aimed to evaluate the initial healing effects of PRP gel and PRF on deep corneal wounds. Thirty-three eyes from New Zealand white rabbits were divided into four groups: group 1, lamellar keratectomy (LK); group 2, LK + commercial porcine small intestinal submucosal membrane (SIS); group 3, LK + SIS + PRP gel; and group 4, LK + SIS + PRF. Postoperative clinical and histological findings were observed for eight weeks. Group 1 showed no neovascularization during the observation period, and incompletely recovered with a thin cornea. Group 2 showed active healing through neovascularization, and a thick cornea was regenerated through the sufficient generation of myofibroblasts. Although group 3 showed a healing effect similar to that of group 2, angiogenesis and subsequent vessel regression were promoted, and corneal opacity improved more rapidly. In group 4, angiogenesis was promoted during initial healing; however, the incidence of complications, such as inflammation, was high, and myofibroblasts were hardly generated in the corneal stroma, which adversely affected remodeling. In conclusion, while PRP gel is a safe surgical material for promoting remodeling through vascular healing and myofibroblast production in deep corneal wounds, the use of PRF is not recommended.

TGF-β Superfamily Signaling in the Eye: Implications for Ocular Pathologies

The TGF-β signaling pathway plays a crucial role in several key aspects of development and tissue homeostasis. TGF-β ligands and their mediators have been shown to be important regulators of ocular physiology and their dysregulation has been described in several eye pathologies. TGF-β signaling participates in regulating several key developmental processes in the eye, including angiogenesis and neurogenesis. Inadequate TGF-β signaling has been associated with defective angiogenesis, vascular barrier function, unfavorable inflammatory responses, and tissue fibrosis. In addition, experimental models of corneal neovascularization, diabetic retinopathy, proliferative vitreoretinopathy, glaucoma, or corneal injury suggest that aberrant TGF-β signaling may contribute to the pathological features of these conditions, showing the potential of modulating TGF-β signaling to treat eye diseases. This review highlights the key roles of TGF-β family members in ocular physiology and in eye diseases, and reviews approaches targeting the TGF-β signaling as potential treatment options.

Toll-Like Receptor 4 Signaling in the Trabecular Meshwork

Primary open-angle glaucoma is one of the leading causes of blindness worldwide. With limited therapeutics targeting the pathogenesis at the trabecular meshwork (TM), there is a great need for identifying potential new targets. Recent evidence has implicated Toll-like receptor 4 (TLR4) and it is signaling pathway in augmenting the effects of transforming growth factor beta-2 (TGFβ2) and downstream extracellular matrix production. In this review, we examine the role of TLR4 signaling in the trabecular meshwork and the interplay between endogenous activators of TLR4 (damage-associated molecular patterns (DAMPs)), extracellular matrix (ECM), and the effect on intraocular pressure

Extracellular Vesicles in Corneal Fibrosis/Scarring

Communication between cells and the microenvironment is a complex, yet crucial, element in the development and progression of varied physiological and pathological processes. Accumulating evidence in different disease models highlights roles of extracellular vesicles (EVs), either in modulating cell signaling paracrine mechanism(s) or harnessing their therapeutic moiety. Of interest, the human cornea functions as a refractive and transparent barrier that protects the intraocular elements from the external environment. Corneal trauma at the ocular surface may lead to diminished corneal clarity and detrimental effects on visual acuity. The aberrant activation of corneal stromal cells, which leads to myofibroblast differentiation and a disorganized extracellular matrix is a central biological process that may result in corneal fibrosis/scarring. In recent years, understanding the pathological and therapeutic EV mechanism(s) of action in the context of corneal biology has been a topic of increasing interest. In this review, we describe the clinical relevance of corneal fibrosis/scarring and how corneal stromal cells contribute to wound repair and their generation of the stromal haze. Furthermore, we will delve into EV characterization, their subtypes, and the pathological and therapeutic roles they play in corneal scarring/fibrosis.

Interfering Hsa_circRNA_0060640 Suppresses TGF-β2-Induced Proliferation, Motility and EMT in Human Lens Epithelium Cells by Targeting miR-214-3p and Collagen Type I alpha2 Chain

BACKGROUND

Circular RNA (circRNA) is a novel star factor in the research of ocular diseases including cataract and the most common postoperative complication posterior capsule opacification (PCO). Hsa_circRNA_0060640 (circ_0060640) is an age-related cataract-related circRNA. However, its role in cataractogenesis is unrevealed yet.

METHODS

PCO in vitro model was established in human lens epithelium cells (hLECs) induced by transforming growth factor-beta2 (TGF-β2). RNA and protein expressions were respectively detected by quantitative PCR and western blotting. Direct interaction between two RNAs was predicted by Starbase tool and confirmed by dual-luciferase reporter assay. MTS and EdU assays measured cell proliferation; Transwell, starch wound and western blotting assays evaluated cell motility and epithelial-mesenchymal transition (EMT).

RESULTS

Circ_0060640 expression is higher in anterior lens capsule tissues from human cataractous eyes and TGF-β2-stimulated hLECs cells line SRA01/04. RNA interference of circ_0060640 could prevent SRA01/04 cells from TGF-β2-induced cell proliferation, migration and invasion, accompanied with decreased N-cadherin and α-smooth muscle actin and increased E-cadherin. Mechanistically, circ_0060640 directly controls microRNA (miR)-214-3p expression and then regulates gene expression of collagen type I alpha2 chain (COL1A2). Notably, COL1A2 inhibition is underlying the protective role of circ_0060640 silencing and miR-214-3p ectopic expression in TGF-β2-stimulated SRA01/04 cells.

CONCLUSION

Circ_0060640 is a novel cataract-related gene and its silencing could block TGF-β2-evoked hLECs proliferation, motility and EMT in vitro via targeting miR-214-3p-COL1A2 axis. Therefore, targeting circ_0060640 via RNA interference might be a treatment strategy for PCO development.

Pigment Epithelia of the Eye: Cell-Type Conversion in Regeneration and Disease

Pigment epithelial cells (PECs) of the retina (RPE), ciliary body, and iris (IPE) are capable of altering their phenotype. The main pathway of phenotypic switching of eye PECs in vertebrates and humans in vivo and/or in vitro is neural/retinal. Besides, cells of amphibian IPE give rise to the lens and its derivatives, while mammalian and human RPE can be converted along the mesenchymal pathway. The PECs’ capability of conversion in vivo underlies the lens and retinal regeneration in lower vertebrates and retinal diseases such as proliferative vitreoretinopathy and fibrosis in mammals and humans. The present review considers these processes studied in vitro and in vivo in animal models and in humans. The molecular basis of conversion strategies in PECs is elucidated. Being predetermined onto- and phylogenetically, it includes a species-specific molecular context, differential expression of transcription factors, signaling pathways, and epigenomic changes. The accumulated knowledge regarding the mechanisms of PECs phenotypic switching allows the development of approaches to specified conversion for many purposes: obtaining cells for transplantation, creating conditions to stimulate natural regeneration of the retina and the lens, blocking undesirable conversions associated with eye pathology, and finding molecular markers of pathology to be targets of therapy.

Monoclonal antibodies in diabetic retinopathy

INTRODUCTION

Diabetic retinopathy (DR), as one of the main complications of diabetes, is among the leading causes of blindness and visual impairment worldwide.

AREAS COVERED

Current clinical therapies include photocoagulation, vitrectomy, and anti-vascular endothelial growth factor (VEGF) therapies. Bevacizumab and ranibizumab are two monoclonal antibodies (mAbs) inhibiting angiogenesis. Intravitreal ranibizumab and bevacizumab can decrease the rate of blindness and retinal thickness, and improve visual acuity whether as monotherapy or combined with other treatments. They can increase the efficacy of other treatments and decrease their adverse events. Although administered intravitreally, they also might enter the circulation and cause systemic effects. This study is aimed to review our current knowledge about mAbs, bevacizumab and ranibizumab, in DR including superiorities, challenges, and limitations. Meanwhile, we tried to shed light on new ideas to overcome these limitations. Our latest search was done in April 2021 mainly through PubMed and Google Scholar. Relevant clinical studies were imported.

EXPERT OPINION

Future direction includes detection of more therapeutic targets considering other components of DR pathophysiology and shared pathogenesis of DR and neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease, the treat-and-extend regimen, and new ways of drug delivery and other routes of ocular drug administration.

Soluble very low-density lipoprotein receptor (sVLDLR) inhibits fibrosis in neovascular age-related macular degeneration

Subretinal fibrosis is a key pathological feature in neovascular age‐related macular degeneration (nAMD). Previously, we identified soluble very low‐density lipoprotein receptor (sVLDLR) as an endogenous Wnt signaling inhibitor. This study investigates whether sVLDLR plays an anti‐fibrogenic role in nAMD models, including Vldlr^−/− mice and laser‐induced choroidal neovascularization (CNV). We found that fibrosis factors including P‐Smad2/3, α‐SMA, and CTGF were upregulated in the subretinal area of Vldlr^−/− mice and the laser‐induced CNV model. The antibody blocking Wnt co‐receptor LRP6 significantly attenuated the overexpression of fibrotic factors in these two models. Moreover, there was a significant reduction of sVLDLR in the interphotoreceptor matrix (IPM) in the laser‐induced CNV model. A transgenic strain (sVLDLR‐Tg) with sVLDLR overexpression in the IPM was generated. Overexpression of sVLDLR ameliorated the profibrotic changes in the subretinal area of the laser‐induced CNV model. In addition, Wnt and TGF‐β signaling synergistically promoted fibrogenesis in human primary retinal pigment epithelium (RPE) cells. CRISPR/Cas9‐mediated LRP6 gene knockout (KO) attenuated this synergistic effect. The disruption of VLDLR expression promoted, while the overexpression of sVLDLR inhibited TGF‐β‐induced fibrosis. These findings suggest that overactivated Wnt signaling enhances the TGF‐β pathway in subretinal fibrosis. sVLDLR confers an antifibrotic effect, at least partially, through the inhibition of Wnt signaling and thus, has therapeutic potential for fibrosis.

Artesunate inhibits the development of PVR by suppressing the TGF-β/Smad signaling pathway

Proliferative vitreoretinopathy (PVR) is the main cause of retinal detachment surgery failure. The epithelial-mesenchymal transition (EMT) induced by transforming growth factor (TGF-β2) plays an important role in the development of PVR. Artesunate has been widely studied as a treatment for ophthalmic diseases because of its antioxidant, anti-inflammatory, antiapoptotic and antiproliferative properties. The purpose of this study was to investigate the effects of artesunate on the TGF-β2-induced EMT in ARPE-19 cells and PVR development. We found that artesunate inhibited the proliferation and contraction of ARPE-19 cells after the EMT and the autocrine effects of TGF-β2 on ARPE-19 cells. Additionally, the levels of Smad3 and p-Smad3 were increased in clinical samples, and artesunate decreased the levels of Smad3 and p-Smad3 in ARPE-19 cells treated with TGF-β2. Artesunate also inhibited the occurrence and development of PVR in vivo. In summary, artesunate inhibits the occurrence and development of PVR by inhibiting the EMT in ARPE-19 cells.

FAK Inhibition Attenuates Corneal Fibroblast Differentiation In Vitro

Corneal fibrosis (or scarring) occurs in response to ocular trauma or infection, and by reducing corneal transparency, it can lead to visual impairment and blindness. Studies highlight important roles for transforming growth factor (TGF)-β1 and -β3 as modulators in corneal wound healing and fibrosis, leading to increased extracellular matrix (ECM) components and expression of α-smooth muscle actin (αSMA), a myofibroblast marker. In this study, human corneal fibroblasts (hCF) were cultured as a monolayer culture (2D) or on poly-transwell membranes to generate corneal stromal constructs (3D) that were treated with TGF-β1, TGF-β3, or TGF-β1 + FAK inhibitor (FAKi). Results show that hCF 3D constructs treated with TGF-β1 or TGF-β3 impart distinct effects on genes involved in wound healing and fibrosis-ITGAV, ITGB1, SRC and ACTA2. Notably, in the 3D construct model, TGF-β1 enhanced αSMA and focal adhesion kinase (FAK) protein expression, whereas TGF-β3 did not. In addition, in both the hCF 2D cell and 3D construct models, we found that TGF-β1 + FAKi attenuated TGF-β1-mediated myofibroblast differentiation, as shown by abrogated αSMA expression. This study concludes that FAK signaling is important for the onset of TGF-β1-mediated myofibroblast differentiation, and FAK inhibition may provide a novel beneficial therapeutic avenue to reduce corneal scarring.

Understanding Drivers of Ocular Fibrosis: Current and Future Therapeutic Perspectives

Ocular fibrosis leads to severe visual impairment and blindness worldwide, being a major area of unmet need in ophthalmology and medicine. To date, the only available treatments are antimetabolite drugs that have significant potentially blinding side effects, such as tissue damage and infection. There is thus an urgent need to identify novel targets to prevent/treat scarring and postsurgical fibrosis in the eye. In this review, the latest progress in biological mechanisms underlying ocular fibrosis are discussed. We also summarize the current knowledge on preclinical studies based on viral and non-viral gene therapy, as well as chemical inhibitors, for targeting TGFβ or downstream effectors in fibrotic disorders of the eye. Moreover, the role of angiogenetic and biomechanical factors in ocular fibrosis is discussed, focusing on related preclinical treatment approaches. Moreover, we describe available evidence on clinical studies investigating the use of therapies targeting TGFβ-dependent pathways, angiogenetic factors, and biomechanical factors, alone or in combination with other strategies, in ocular tissue fibrosis. Finally, the recent progress in cell-based therapies for treating fibrotic eye disorders is discussed. The increasing knowledge of these disorders in the eye and the promising results from testing of novel targeted therapies could offer viable perspectives for translation into clinical use.

Dpp/TGFβ-superfamily play a dual conserved role in mediating the damage response in the retina

Retinal homeostasis relies on intricate coordination of cell death and survival in response to stress and damage. Signaling mechanisms that coordinate this process in the adult retina remain poorly understood. Here we identify Decapentaplegic (Dpp) signaling in Drosophila and its mammalian homologue Transforming Growth Factor-beta (TGFβ) superfamily, that includes TGFβ and Bone Morphogenetic Protein (BMP) signaling arms, as central mediators of retinal neuronal death and tissue survival following acute damage. Using a Drosophila model for UV-induced retinal damage, we show that Dpp released from immune cells promotes tissue loss after UV-induced retinal damage. Interestingly, we find a dynamic response of retinal cells to this signal: in an early phase, Dpp-mediated stimulation of Saxophone/Smox signaling promotes apoptosis, while at a later stage, stimulation of the Thickveins/Mad axis promotes tissue repair and survival. This dual role is conserved in the mammalian retina through the TGFβ/BMP signaling, as supplementation of BMP4 or inhibition of TGFβ using small molecules promotes retinal cell survival, while inhibition of BMP negatively affects cell survival after light-induced photoreceptor damage and NMDA induced inner retinal neuronal damage. Our data identify key evolutionarily conserved mechanisms by which retinal homeostasis is maintained.

Lobeglitazone attenuates fibrosis in corneal fibroblasts by interrupting TGF-beta-mediated Smad signaling

PURPOSE

Transforming growth factor beta 1 (TGF-β1) is an important cytokine released after ocular surface injury to promote wound healing. However, its persistence at the injury site triggers a fibrotic response that leads to corneal scarring and opacity. Thiazolidinediones (TZDs) are synthetic peroxisome proliferator-activated receptor gamma (PPAR-γ) ligands used to regulate glucose and lipid metabolism in the management of type 2 diabetes. Studies have also showed TZDs have antifibrotic effect. In this study, we investigated the antifibrotic effect of the TZD lobeglitazone on TGF-β1-induced fibrosis in corneal fibroblasts.

METHODS

Human primary corneal fibroblasts were cultivated and treated with TGF-β1 (5 ng/mL) to induce fibrosis, with or without pre-treatments with different concentrations of lobeglitazone. Myofibroblast differentiation and extracellular matrix (ECM) protein expression was evaluated by western blotting, immunofluorescence, real-time PCR, and collagen gel contraction assay. The effect of lobeglitazone on TGF-β1-induced reactive oxygen species (ROS) generation was evaluated by DCFDA-cellular ROS detection assay kit. Signaling proteins were evaluated by western blotting to determine the mechanism underlying the antifibrotic effect.

RESULTS

Our results showed lobeglitazone attenuated TGF-β1-induced ECM synthesis and myofibroblast differentiation of corneal fibroblasts. This antifibrotic effect appeared to be independent of PPAR signaling and rather due to the inhibition of the TGF-β1-induced Smad signaling. Lobeglitazone also blocked TGF-β1-induced ROS generation and nicotinamide adenine dinucleotide phosphate oxidase (Nox) 4 transcription.

CONCLUSION

These findings indicate that lobeglitazone may be a promising therapeutic agent for corneal scarring. KEY MESSAGES.

LncRNA-MALAT1/miRNA-204-5p/Smad4 Axis Regulates Epithelial-Mesenchymal Transition, Proliferation and Migration of Lens Epithelial Cells

MATERIALS AND METHODS

LECs were cultured and induced with TGF-β2 (10 ng/mL). SiRNA against MALAT1 (Si-MALAT1) was transfected into LECs to knockdown the expression of MALAT1. To overexpress or knockdown miR-204-5p, miR-204-5p mimics (miR-204-5p mimics) and anti-miR-204-5p (miR-204-5p inhibitor) were transfected into LECs. We used RNA FISH to identify the location of MALAT1. RNA levels of MALAT1 and miR-204-5p were analyzed by RT-qPCR. Additionally, target protein levels of Smad4, epithelial differentiation and mesenchymal markers were analyzed with Western blot. We employed EdU Labeling to measured cell proliferation and performed Transwell Assay to analyze the cell migration. Dual-luciferase reporter assays in LECs were conducted to verify whether miRNA-204-5p was negatively regulated by MALAT1 and Smad4 was a direct target of miR-204-5p.

RESULTS

The expression of MALAT1 was upregulated in PCO specimens. MALAT1 was overexpressed in TGF-β2 induced LECs, and the knockdown of MALAT1 could attenuate TGF-β2 induced EMT. Besides, the upregulation of MALAT1 was correlated with the downregulation of miR-204-5p and upregulation of Smad4. Importantly, MALAT1 was revealed to be located in the cytoplasm of LECs. Furthermore, luciferase reporter assays confirmed that MALAT1 could negatively regulate the expression of miR-204-5p and then regulate its direct target Smad4. Finally, the knockdown of MALAT1 could inhibit the EMT, proliferation, and migration of LECs; however, those can be reversed by anti-miR-204-5p.

CONCLUSIONS

Our findings reveal that MALAT1 may regulate EMT, proliferation, and migration of LECs as a ceRNA by "sponging" miR-204-5p and targeting Smad4, and serve as a promising therapeutic target in preventing PCO.

Inhibition of TGF-β2-induced migration and epithelial-mesenchymal transition in ARPE-19 by sulforaphane

AIM

To investigate the effects of sulforaphane (SFN) on transforming growth factor (TGF)-β2 stimulated migration and epithelial-mesenchymal transition (EMT) in ARPE-19 cells.

METHODS

ARPE-19 cells were cultured in the presence or absence of SFN or TGF-β2. SFN toxicity was assessed by performing a lactate dehydrogenase assay (LDH) and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays, and cell migration was evaluated by Transwell migration assay. Actin stress fiber formation in ARPE-19 cells was determined using immunofluorescence analysis. Immunoblotting analysis was used to determine fibronectin and α-smooth muscle actin expressions along with the degree of Smad and Akt phosphorylation.

RESULTS

SFN inhibited ARPE-19 migration. Additionally, SFN attenuated TGF-β2-induced appearance of actin stress fibers as well as fibronectin and α-smooth muscle actin expressions in these cells. SFN also hindered the TGF-β2-stimulated phosphorylation of Smad2, Smad3, and Akt. SFN showed no cytotoxicity towards ARPE-19 cells.

CONCLUSION

SFN inhibits TGF-β2-stimulated migration and EMT in ARPE-19 cells, probably by preventing the establishment of actin stress fibers and Akt and Smad2/3 signaling.

The Vitreous Ecosystem in Diabetic Retinopathy: Insight into the Patho-Mechanisms of Disease

Diabetic retinopathy is one of the leading causes of blindness in the world with the incidence of disease ever-increasing worldwide. The vitreous humor represents an extensive and complex interactive arena for cytokines in the diabetic eye. In recent decades, there has been significant progress in understanding this environment and its implications in disease pathophysiology. In this review, we investigate the vitreous ecosystem in diabetic retinopathy at the molecular level. Areas of concentration include: the current level of knowledge of growth factors, cytokine and chemokine mediators, and lipid-derived metabolites in the vitreous. We discuss the molecular patho-mechanisms of diabetic retinopathy based upon current vitreous research.

Ocular TGF-β, Matrix Metalloproteinases, and TIMP-1 Increase with the Development and Progression of Diabetic Retinopathy in Type 2 Diabetes Mellitus

Diabetic retinopathy (DR) is a sight-threatening late complication of diabetes mellitus (DM). Even though its pathophysiology has not been fully elucidated, several studies suggested a role for transforming growth factor- (TGF-) β, matrix metalloproteinases (MMPs), and tissue inhibitors of matrix metalloproteinase (TIMP) in the onset and progression of the disease. Consequently, the aim of this study was to analyze the concentrations of TGF-β1, TGF-β2, TGF-β3, MMP-3, MMP-9, and TIMP-1 in patients with different stages of DR in order to identify stage-specific changes in their concentrations during the progression of the disease. Serum and aqueous humor (AH) samples were collected during intraocular surgery, and eyes were classified into the following groups: healthy controls (n = 17), diabetic patients with non-apparent DR (n = 23), mild/moderate nonproliferative DR (NPDR) (n = 13), and advanced NPDR/proliferative DR (PDR) without vitreal hemorrhage (n = 14). None of the patients had been under anti-VEGF or laser treatment within six months prior to surgery. In the AH, TGF-β1 levels increased in advanced NPDR/PDR by a factor of 5.5 compared to the control group. Similarly, an increase in MMP-3 and TIMP-1 levels in the AH was evident in the later stages of DR, corresponding to a 7.7- and 2.4-fold increase compared to the control group, respectively, whereas serum levels of the studied proteins remained similar. In conclusion, increased concentrations of TGF-β1, MMP-3, and TIMP-1 in the AH, but not in the serum, in advanced NPDR/PDR indicate that the intraocular regulation for these cytokines is independent of the systemic one and suggest their involvement in the progression of DR.

Transcriptional Profiling Identifies Upregulation of Neuroprotective Pathways in Retinitis Pigmentosa

Hereditary retinal degenerations like retinitis pigmentosa (RP) are among the leading causes of blindness in younger patients. To enable in vivo investigation of cellular and molecular mechanisms responsible for photoreceptor cell death and to allow testing of therapeutic strategies that could prevent retinal degeneration, animal models have been created. In this study, we deeply characterized the transcriptional profile of mice carrying the transgene rhodopsin V20G/P23H/P27L (VPP), which is a model for autosomal dominant RP. We examined the degree of photoreceptor degeneration and studied the impact of the VPP transgene-induced retinal degeneration on the transcriptome level of the retina using next generation RNA sequencing (RNASeq) analyses followed by weighted correlation network analysis (WGCNA). We furthermore identified cellular subpopulations responsible for some of the observed dysregulations using in situ hybridizations, immunofluorescence staining, and 3D reconstruction. Using RNASeq analysis, we identified 9256 dysregulated genes and six significantly associated gene modules in the subsequently performed WGCNA. Gene ontology enrichment showed, among others, dysregulation of genes involved in TGF-β regulated extracellular matrix organization, the (ocular) immune system/response, and cellular homeostasis. Moreover, heatmaps confirmed clustering of significantly dysregulated genes coding for components of the TGF-β, G-protein activated, and VEGF signaling pathway. 3D reconstructions of immunostained/in situ hybridized sections revealed retinal neurons and Müller cells as the major cellular population expressing representative components of these signaling pathways. The predominant effect of VPP-induced photoreceptor degeneration pointed towards induction of neuroinflammation and the upregulation of neuroprotective pathways like TGF-β, G-protein activated, and VEGF signaling. Thus, modulation of these processes and signaling pathways might represent new therapeutic options to delay the degeneration of photoreceptors in diseases like RP.

Factors Affecting Posterior Capsule Opacification in the Development of Intraocular Lens Materials

Posterior capsule opacification (PCO) is the most common complication arising from the corrective surgery used to treat cataract patients. PCO arises when lens epithelial cells (LEC) residing in the capsular bag post-surgery undergo hyper-proliferation and transdifferentiation into myofibroblasts, migrating from the posterior capsule over the visual axis of the newly implanted intraocular lens (IOL). The developmental pathways underlying PCO are yet to be fully understood and the current literature is contradictory regarding the impact of the recognised risk factors of PCO. The aim of this review is firstly to collate the known biochemical pathways that lead to PCO development, providing an up-to-date chronological overview from surgery to established PCO formation. Secondly, the risk factors of PCO are evaluated, focussing on the impact of IOLs’ properties. Finally, the latest experimental model designs used in PCO research are discussed to demonstrate the ongoing development of clinical PCO models, the efficacy of newly developed IOL technology, and potential therapeutic interventions. This review will contribute to current PCO literature by presenting an updated overview of the known developmental pathways of PCO, an evaluation of the impact of the risk factors underlying its development, and the latest experimental models used to investigate PCO. Furthermore, the review should provide developmental routes for research into the investigation of potential therapeutic interventions and improvements in IOL design in the aid of preventing PCO for new and existing patients.

Impairment of corneal epithelial wound healing is association with increased neutrophil infiltration and reactive oxygen species activation in tenascin X-deficient mice

The purpose of the study was to uncover the role of tenascin X in modulation of healing in mouse corneas subjected to epithelium debridement. Healing in corneas with an epithelial defect was evaluated at the levels of gene and protein expression. Wound healing-related mediators and inflammatory cell infiltration were detected by histology, immunohistochemistry and real-time RT-PCR. Tenascin X protein was upregulated in the wounded wild-type (WT) corneal epithelium. The lack of tenascin X impaired closure of an epithelial defect and accelerated infiltration of neutrophils into the wound periphery as compared to the response in WT tissue. Expression of wound healing-related proinflammatory and reparative components, i.e., interleukin-6, transforming growth factor β, matrix metalloproteinases, were unaffected by the loss of tenascin X expression. Marked accumulation of malondialdehyde (a lipid peroxidation-derived product) was observed in KO healing epithelia as compared with its WT counterpart. Neutropenia induced by systemic administration of a specific antibody rescued the impairment of epithelial healing in KO corneas, with reduction of malondialdehyde levels in the epithelial cells. Finally, we showed that a chemical scavenging reactive oxygen species reversed the impairment of attenuation of epithelial repair with a reduction of tissue levels of malondialdehyde. In conclusion, loss of tenascin X prolonged corneal epithelial wound healing and increased neutrophilic inflammatory response to debridement in mice. Tenascin X contributes to the control of neutrophil infiltration needed to support the regenerative response to injury and prevent the oxidative stress mediators from rising to cytotoxic levels.

Involvement of Müller Glial Autoinduction of TGF-β in Diabetic Fibrovascular Proliferation Via Glial-Mesenchymal Transition

Purpose

Müller glial–mesenchymal transition (GMT) is reported as the fibrogenic mechanism promoted by TGF-β–SNAIL axis in Müller cells transdifferentiated into myofibroblasts. Here we show the multifaceted involvement of TGF-β in diabetic fibrovascular proliferation via Müller GMT and VEGF-A production.

Methods

Surgically excised fibrovascular tissues from the eyes of patients with proliferative diabetic retinopathy were processed for immunofluorescence analyses of TGF-β downstream molecules. Human Müller glial cells were used to evaluate changes in gene and protein expression with real-time quantitative PCR and ELISA, respectively. Immunoblot analyses were performed to detect TGF-β signal activation.

Results

Müller glial cells in patient fibrovascular tissues were immunopositive for GMT-related molecular markers, including SNAIL and smooth muscle protein 22, together with colocalization of VEGF-A and TGF-β receptors. In vitro administration of TGF-β1/2 upregulated TGFB1 and TGFB2, both of which were suppressed by inhibitors for nuclear factor-κB, glycogen synthase kinase-3, and p38 mitogen-activated protein kinase. Of the various profibrotic cytokines, TGF-β1/2 application exclusively induced Müller glial VEGFA mRNA expression, which was decreased by pretreatment with small interfering RNA for SMAD2 and inhibitors for p38 mitogen-activated protein kinase and phosphatidylinositol 3-kinase. Supporting these findings, TGF-β1/2 stimulation to Müller cells increased the phosphorylation of these intracellular signaling molecules, all of which were also activated in Müller glial cells in patient fibrovascular tissues.

Conclusions

This study underscored the significance of Müller glial autoinduction of TGF-β as a pathogenic cue to facilitate diabetic fibrovascular proliferation via TGF-β–driven GMT and VEGF-A–driven angiogenesis.

DNA-based eyelid trait prediction in Chinese Han population

The eyelid folding represents one of the most distinguishing features of East Asian faces, involving the absence or presence of the eyelid crease, i.e., single vs. double eyelid. Recently, a genome-wide association study (GWAS) identified two SNPs (rs12570134 and rs1415425) showing genome-wide significant association with the double eyelid phenotype in Japanese. Here we report a confirmatory study in 697 Chinese individuals of exclusively Han origin. Only rs1415425 was statistically significant (P-value = 0.011), and the allele effect was on the same direction with that reported in Japanese. This SNP combined with gender and age explained 10.0% of the total variation in eyelid folding. DNA-based prediction model for the eyelid trait was developed and evaluated using logistic regression. The model showed mild to moderate predictive capacity (AUC = 0.69, sensitivity = 63%, and specificity = 70%). We further selected six additional SNPs by massive parallel sequencing of 19 candidate genes in 24 samples, and one SNP rs2761882 was statistically significant (P-value = 0.027). All predictors including these two SNPs (rs1415425 and rs2761882), gender, and age explained 11.2% of the total variation. The combined prediction model obtained an improved predictive capacity (AUC = 0.72, sensitivity = 62%, and specificity = 66%). Our study thus provided a confirmation of previous GWAS findings and a DNA-based prediction of the eyelid trait in Chinese Han individuals. This model may add value to forensic DNA phenotyping applications considering gender and age can be separately inferred from genetic and epigenetic markers. To further improve the prediction accuracy, future studies should focus on identifying more informative SNPs by large GWASs in East Asian populations.

Wound Healing After Alkali Burn Injury of the Cornea Involves Nox4-Type NADPH Oxidase

Purpose

Corneal injury that occurs after burning with alkali initiates wound-healing processes, including inflammation, neovascularization, and fibrosis. Excessive reactions to injury can reduce corneal transparency and thereby compromise vision. The NADPH oxidase (Nox) enzyme complex is known to be involved in cell signaling for wound-healing angiogenesis, but its role in corneal neovascularization has been little studied.

Methods

The center corneas of wild-type and Nox4 knockout (KO) mice were injured with 3 µL 1 M NaOH, while the contralateral corneas remained untouched. On day 7, mRNA expression levels of NADPH oxidase isoforms, the proangiogenic factors VEGF-A and TGFβ1, and proinflammatory genes ICAM-1 and VCAM-1 were determined. Corneal neovascularization and fibrosis were visualized using PECAM-1 antibody and picrosirius red staining, respectively, on the same day.

Results

Expressions of both Nox2 and Nox4 gene isoforms as well as the above genes were markedly increased in the injured corneas at 7 days. Injured corneas showed neovascularization and fibrosis as well as an increase in clinical opacity score. All responses stimulated by alkali burn were abrogated in Nox4 KO mice.

Conclusions

Nox4 could be a new target to treat pathologic corneal wound-healing responses and such targeting might prevent blindness caused by burn injuries.

Immune-Mediated Retinal Vasculitis in Posterior Uveitis and Experimental Models: The Leukotriene (LT)B4-VEGF Axis

Retinal vascular diseases have distinct, complex and multifactorial pathogeneses yet share several key pathophysiological aspects including inflammation, vascular permeability and neovascularisation. In non-infectious posterior uveitis (NIU), retinal vasculitis involves vessel leakage leading to retinal enlargement, exudation, and macular oedema. Neovascularisation is not a common feature in NIU, however, detection of the major angiogenic factor—vascular endothelial growth factor A (VEGF-A)—in intraocular fluids in animal models of uveitis may be an indication for a role for this cytokine in a highly inflammatory condition. Suppression of VEGF-A by directly targeting the leukotriene B4 (LTB4) receptor (BLT1) pathway indicates a connection between leukotrienes (LTs), which have prominent roles in initiating and propagating inflammatory responses, and VEGF-A in retinal inflammatory diseases. Further research is needed to understand how LTs interact with intraocular cytokines in retinal inflammatory diseases to guide the development of novel therapeutic approaches targeting both inflammatory mediator pathways.

Glaucoma and neuroinflammation: An overview

Glaucoma is an optic neuropathy characterized by well-defined optic disc morphological changes (i.e., cup enlargement, neuroretinal border thinning, and notching, papillary vessel modifications) consequent to retinal ganglion cell loss, axonal degeneration, and lamina cribrosa remodeling. These modifications tend to be progressive and are the main cause of functional damage in glaucoma. Despite the latest findings about the pathophysiology of the disease, the exact trigger mechanisms and the mechanism of degeneration of retinal ganglion cells and their axons have not been completely elucidated. Neuroinflammation may play a role in both the development and the progression of the disease as a result of its effects on retinal environment and retinal ganglion cells. We summarize the latest findings about neuroinflammation in glaucoma and examine the connection between risk factors, neuroinflammation, and retinal ganglion cell degeneration.

Immunology and Pathology in Ocular Drug Development

Clear vision is dependent on features that protect the anatomical integrity of the eye (cornea and sclera) and those that contribute to internal ocular homeostasis by conferring hemangiogenic (avascular tissues and antiangiogenic factors), lymphangiogenic (lack of draining lymphatics), and immunologic (tight junctions that form blood-ocular barriers, immunosuppressive cells, and modulators) privileges. The later examples are necessary components that enable the eye to maintain an immunosuppressive environment that responds to foreign invaders in a deviated manner, minimizing destructive inflammation that would impair vision. These conditions allowed for the observations made by Medawar, in 1948, of delayed rejection of allogenic tissue grafts in the anterior chamber of mouse eye and permit the sequestration of foreign invaders (eg, Toxoplasma gondii) within the retina of healthy individuals. Yet successful development of intraocular drugs (biologics and delivery devices) has been stymied by adverse ocular pathology, much of which is driven by immune pathways. The eye can be intolerant of foreign protein irrespective of delivery route, and endogenous ocular cells have remarkable plasticity when recruited to preserve visual function. This article provides a review of current understanding of ocular immunology and the potential role of immune mechanisms in pathology observed with intraocular drug delivery.

AMPK Activation by 5-Amino-4-Imidazole Carboxamide Riboside-1-β-D-Ribofuranoside Attenuates Alkali Injury-Induced Corneal Fibrosis

Purpose

Increased TGF-β1 synthesis after corneal alkali injury is implicated in corneal fibrosis, as it promotes transdifferentiation of keratocytes into myofibroblasts. The activation of 5'-adenosine monophosphate-activated protein kinase (AMPK) by 5-amino-4-imidazole carboxamide riboside-1-β-d-ribofuranoside (AICAR) inhibits TGF-β1-induced fibrosis in other cell types. We investigated the antifibrotic effect of AICAR in corneal fibroblasts after alkali injury.

Methods

Mouse models of corneal alkali burn, produced by placing 2-mm-diameter filter paper soaked in 0.1-N NaOH on the right cornea for 30 seconds, were treated with the test drugs 4× daily for 21 days. The central cornea was scanned by optical coherence tomography (OCT). Corneal tissues were obtained and processed for western blotting and immunohistochemistry. For in vitro analysis, primary human corneal fibroblasts were treated directly with TGF-β1 to induce fibrosis, with or without AICAR pretreatment. Myofibroblast activation and extracellular matrix (ECM) protein synthesis were detected by western blotting, real-time PCR, and collagen gel contraction assay. Signaling proteins were analyzed by western blotting.

Results

Alkali injury induced the upregulation of TGF-β1 expression, which led to increased α-smooth muscle actin (α-SMA) and fibronectin synthesis and myofibroblast differentiation. AMPK activation by AICAR significantly suppressed TGF-β1 and ECM protein expression. The antifibrotic effect of AICAR was AMPK dependent, as treatment with the AMPK inhibitor Compound C attenuated the antifibrotic response.

Conclusions

AMPK activation by AICAR suppresses the myofibroblast differentiation and ECM synthesis that occur after alkali injury in corneal fibroblasts.

Human umbilical cord mesenchymal stem cell-derived exosomal miR-27b attenuates subretinal fibrosis via suppressing epithelial-mesenchymal transition by targeting HOXC6

BACKGROUND AND AIM

Subretinal fibrosis resulting from neovascular age-related macular degeneration (nAMD) is one of the major causes of serious and irreversible vision loss worldwide, and no definite and effective treatment exists currently. Retinal pigmented epithelium (RPE) cells are crucial in maintaining the visual function of normal eyes and its epithelial-mesenchymal transition (EMT) is associated with the pathogenesis of subretinal fibrosis. Stem cell-derived exosomes have been reported to play a crucial role in tissue fibrosis by transferring their molecular contents. This study aimed to explore the effects of human umbilical cord-derived mesenchymal stem cell exosomes (hucMSC-Exo) on subretinal fibrosis in vivo and in vitro and to investigate the anti-fibrotic mechanism of action of hucMSC-Exo.

METHODS

In this study, human umbilical cord-derived mesenchymal stem cells (hucMSCs) were successfully cultured and identified, and exosomes were isolated from the supernatant by ultracentrifugation. A laser-induced choroidal neovascularization (CNV) and subretinal fibrosis model indicated that the intravitreal administration of hucMSC-Exo effectively alleviated subretinal fibrosis in vivo. Furthermore, hucMSC-Exo could efficaciously suppress the migration of retinal pigmented epithelial (RPE) cells and promote the mesenchymal-epithelial transition by delivering miR-27b-3p. The latent binding of miR-27b-3p to homeobox protein Hox-C6 (HOXC6) was analyzed by bioinformatics prediction and luciferase reporter assays.

RESULTS

This study showed that the intravitreal injection of hucMSC-Exo effectively ameliorated laser-induced CNV and subretinal fibrosis via the suppression of epithelial-mesenchymal transition (EMT) process. In addition, hucMSC-Exo containing miR-27b repressed the EMT process in RPE cells induced by transforming growth factor-beta2 (TGF-β2) via inhibiting HOXC6 expression.

CONCLUSIONS

The present study showed that HucMSC-derived exosomal miR-27b could reverse the process of EMT induced by TGF-β2 via inhibiting HOXC6, indicating that the exosomal miR-27b/HOXC6 axis might play a vital role in ameliorating subretinal fibrosis. The present study proposed a promising therapeutic agent for treating ocular fibrotic diseases and provided insights into the mechanism of action of hucMSC-Exo on subretinal fibrosis.

Quantitative measurement of mechanical properties in wound healing processes in a corneal stroma model by using vibrational optical coherence elastography (OCE)

Corneal wound healing, caused by frequent traumatic injury to the cornea and increasing numbers of refractive surgeries, has become a vital clinical problem. In the cornea, wound healing is an extremely complicated process. However, little is known about how the biomechanical changes in wound healing response of the cornea. Collagen-based hydrogels incorporating corneal cells are suitable for replicating a three-dimensional (3D) equivalent of the cornea in-vitro. In this study, the mechanical properties of corneal stroma models were quantitatively monitored by a vibrational optical coherence elastography (OCE) system during continuous culture periods. Specifically, human corneal keratocytes were seeded at 5 × 10⁵ cells/mL in the hydrogels with a collagen concentration of 3.0 mg/mL. The elastic modulus of the unwounded constructs increased from 2.950 ± 0.2 kPa to 11.0 ± 1.4 kPa, and the maximum thickness decreased from 1.034 ± 0.1 mm to 0.464 ± 0.09 mm during a 15-day culture period. Furthermore, a traumatic wound in the construct was introduced with a size of 500 µm. The elastic modulus of the neo-tissue in the wound area increased from 1.488 ± 0.4 kPa to 6.639 ± 0.3 kPa over 13 days. This study demonstrates that the vibrational OCE system is capable of quantitative monitoring the changes in mechanical properties of a corneal stroma wound model during continuous culture periods and improves our understanding on corneal wound healing processes.

Multimodal imaging and electroretinography highlights the role of VEGF in the laser-induced subretinal fibrosis of monkey

Age-related macular degeneration (AMD) is a leading cause of blindness. Laser-induced nonhuman primate choroidal neovascularization (CNV) is a widely used animal model of neovascular AMD. Subretinal fibrosis (SFb) is the major limiting factor of effective anti-VEGF therapy for neovascular AMD, yet SFb has never been systematically analyzed in the primate CNV model and if VEGF directly affect SFb is unknown. We recruited a large cohort of rhesus macaques to study the occurrence, multimodal imaging and electroretinography (ERG) features, and related cytokines of SFb. Here we show that among 33 rhesus macaques, 88% CNV eyes developed SFb. Spectral domain optical coherence tomography (SD-OCT) identified four types of subretinal hyper-reflective material (SHRM) of SFb in primate. Multimodal imaging is reliable for monitoring SFb and matches the histological results well. Reduced amplitude of oscillatory potentials correlates with the thinning of inner retina layers and is a possible SFb indicator. Iba1⁺ microglia/macrophage cells infiltrated in the fibrotic lesions, and aqueous cytokine analysis identified four fibrosis-related factors (GM-CSF, IL-10, TGFβ2 and VEGF). Unexpectedly, we found sustained expression of VEGF may be an important inducer of SFb, and anti-VEGF therapy actually partially suppresses SFb. Taken together, our data suggest the laser-induced primate SFb model, coupled with multimodal imaging and ERG recording, is a useful system to dissect the pathogenesis and explore the rationale of treatment for SFb; and combined therapy with anti-VEGF and anti-fibrosis agents is necessary for AMD treatment.

Role of Natural Killer Cells in Uveal Melanoma

Simple Summary

Metastatic Uveal Melanoma (MUM) is a lethal malignancy with no durable treatment available to date. A vast majority of patients with MUM present with liver metastasis. The liver harbors metastatic disease with an apparent lack of a cytotoxic T cell response. It is becoming evident that MUM is not an immunologically silent malignancy and the investigation of non-T cell anti-tumor immunity is warranted. In this review, we highlight the relevance of Natural Killer (NK) cells in the biology and treatment of MUM. Potent anti-NK cell immunosuppression employed by uveal melanoma alludes to its vulnerability to NK cell cytotoxicity. On the contrary, micro-metastasis in the liver survive for several years within close vicinity of a plethora of circulating and liver-resident NK cells. This review provides unique perspectives into the potential role of NK cells in control or progression of uveal melanoma.

Abstract

Uveal melanoma has a high mortality rate following metastasis to the liver. Despite advances in systemic immune therapy, treatment of metastatic uveal melanoma (MUM) has failed to achieve long term durable responses. Barriers to success with immune therapy include the immune regulatory nature of uveal melanoma as well as the immune tolerant environment of the liver. To adequately harness the anti-tumor potential of the immune system, non-T cell-based approaches need to be explored. Natural Killer (NK) cells possess potent ability to target tumor cells via innate and adaptive responses. In this review, we discuss evidence that highlights the role of NK cell surveillance and targeting of uveal melanoma. We also discuss the repertoire of intra-hepatic NK cells. The human liver has a vast and diverse lymphoid population and NK cells comprise 50% of the hepatic lymphocytes. Hepatic NK cells share a common niche with uveal melanoma micro-metastasis within the liver sinusoids. It is, therefore, crucial to understand and investigate the role of intra-hepatic NK cells in the control or progression of MUM.

Myh11+ microvascular mural cells and derived mesenchymal stem cells promote retinal fibrosis

Retinal diseases are frequently characterized by the accumulation of excessive scar tissue found throughout the neural retina. However, the pathophysiology of retinal fibrosis remains poorly understood, and the cell types that contribute to the fibrotic response are incompletely defined. Here, we show that myofibroblast differentiation of mural cells contributes directly to retinal fibrosis. Using lineage tracing technology, we demonstrate that after chemical ocular injury, Myh11+ mural cells detach from the retinal microvasculature and differentiate into myofibroblasts to form an epiretinal membrane. Inhibition of TGFβR attenuates Myh11+ retinal mural cell myofibroblast differentiation, and diminishes the subsequent formation of scar tissue on the surface of the retina. We demonstrate retinal fibrosis within a murine model of oxygen-induced retinopathy resulting from the intravitreal injection of adipose Myh11-derived mesenchymal stem cells, with ensuing myofibroblast differentiation. In this model, inhibiting TGFβR signaling does not significantly alter myofibroblast differentiation and collagen secretion within the retina. This work shows the complexity of retinal fibrosis, where scar formation is regulated both by TGFβR and non-TGFβR dependent processes involving mural cells and derived mesenchymal stem cells. It also offers a cautionary note on the potential deleterious, pro-fibrotic effects of exogenous MSCs once intravitreally injected into clinical patients.

Quantification of Growth Factors and Fibronectin in Diverse Preparations of Platelet-Rich Plasma for the Treatment of Ocular Surface Disorders (E-PRP)

Purpose

The purpose of this study was to quantify the presence of growth factors (GFs) and fibronectin in autologous platelet-rich plasma for topical ocular use (E-PRP) comparing their concentration when different preparation and preservation procedures were applied.

Methods

E-PRP was prepared with blood from healthy volunteers. The count of platelets, leukocytes, and red blood cells in the whole blood and E-PRP were performed. The concentration of the GFs platelet-derived growth factor BB (PDGF-BB), transforming growth factor β1 (TGF-β1), epidermal growth factor (EGF), vascular endothelial growth factor A (VEGF-A), and fibronectin was determined in each of the four procedures applied including fresh, frozen at −20°C for 3 months, fresh-spin, and frozen-spin at −20°C E-PRP samples. Posterior statistical analysis was performed to establish significant differences between groups and between GFs in relation to the amounts of platelets.

Results

Platelets in the E-PRP doubled in the number of basal values of whole blood (P ≤ 0.01). The blood cells in the E-PRP decreased drastically in red cells (99%) and also in leukocytes (82%). The concentration of PDGF-BB and EGF was significantly higher (P < 0.01) when the E-PRP samples were frozen at −20°C. However, no significant differences were observed for TGF-β1, VEGF-A, and fibronectin (P > 0.05). The concentration of GFs in the E-PRP did not necessarily correlate with the number of platelets.

Conclusions

Freezing the E-PRP for 3 months at −20°C increased the concentration of important proteins, such as PDGF-BB and EGF, and maintained the levels of others. These findings are essential because treatments, such as E-PRP, used by patients with ocular surface dysfunctions tend to prolong it in time. In addition, subsequent centrifugation of the E-PRP decreased the values of TFG-β1, but not the other GFs, which would allow adjusting the concentration of TFG-β1, as necessary. This procedure guarantees their correct conservation and viability.

Translational Relevance

This work demonstrates how clinical application can be improved by starting from basic research. The quantification of GFs and fibronectin in platelet-rich plasma (PRP) helps to clarify which is the best mode of preparation and preservation of PRP for clinical applications. This allows to optimize the product that is delivered to the patients as a treatment for the dysfunctions of the ocular surface, guaranteeing that the conservation does not affect at all the quality of the PRP that it is going to be used.

Response of Retinal Pigment Epithelium (RPE)-Choroid Explants to Thermal Stimulation Therapy of the RPE (TSR)

BACKGROUND AND OBJECTIVES

The thermal stimulation therapy of the retinal pigment epithelium (TSR) is a sublethal laser technique for thermal stimulation of the retinal pigment epithelium (RPE)-Bruch's membrane (BrM)-complex. The aim of this study was to investigate the influence of TSR on the release of age-related macular degeneration (AMD)-relevant cell mediators.

STUDY DESIGN/MATERIALS AND METHODS

Porcine RPE-BrM-choroid explants were irradiated with a 532 nm continuous wave laser using different spot sizes (100-300 µm, duration 100 milliseconds, 15-100 mW). Cell death was investigated by calcein staining. Explants were treated with grids of sublethal spots and cultivated in modified Ussing chambers. The effect on matrix metalloproteinase-2 (MMP-2) and -9 was investigated by zymography and quantitative reverse transcription polymerase chain reaction. Secretion of vascular endothelial growth factor (VEGF), pigment epithelium derived factor (PEDF), and transforming growth factor-β (TGF-β) was analyzed by enzyme-linked immunosorbent assay and expression of HSP70 was examined by western blot. Integrity of the RPE/BrM-complex was analyzed by scanning electron microscopy.

RESULTS

Laser powers of 15 mW (100 µm) and 45 mW (300 µm) did not induce RPE cell death. The integrity of the RPE/BrM-complex was not impaired after TSR. After TSR with 300 µm spot size, we observed a significant increase of active MMP-2 in the basal compartments. The content of PEDF significantly increased in treated explants in both compartments with 100 and 300 µm spot sizes. VEGF and TGF-β secretion was not triggered by TSR.

CONCLUSIONS

TSR represents a possible RPE stimulating treatment for dry AMD. TSR increases the basal release of active MMP-2, which might reverse age-related thickening of BrM. VEGF secretion was not triggered by TSR while anti-angiogenic PEDF was increased, indicating an induction of an anti-angiogenic and neuroprotective environment. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.