Investigation of Conjunctival Fibrosis Response Using a 3D Glaucoma Tenon's Capsule + Conjunctival Model

Low Intraocular Pressure Induces Fibrotic Changes in the Trabecular Meshwork and Schlemm's Canal of Sprague Dawley Rats

Purpose

Continuous artificial aqueous humor drainage in the eyes of patients with glaucoma undergoing trabeculectomy likely exerts abnormal shear stress. However, it remains unknown how changes in intraocular pressure (IOP) can affect aqueous humor outflow (AHO).

Methods

Here, we induced and maintained low intraocular pressure (L-IOP) in healthy Sprague Dawley (SD) rats by puncturing their eyes using a tube (200-µm diameter) for 2 weeks. After the rats were euthanized, their eyes were removed, fixed, embedded, stained, and scanned to analyze the physiological and pathological changes in the trabecular meshwork (TM) and Schlemm's canal (SC). We measured SC parameters using ImageJ software and assessed the expression of various markers related to flow shear stress (KLF4), fibrosis (TGF-β1, TGF-β2, α-SMA, pSmad1/5, pSmad2/3, and fibronectin), cytoskeleton (integrin β1 and F-actin), diastolic function (nitric oxide synthase and endothelial nitric oxide synthase [eNOS]), apoptosis (cleaved caspase-3), and proliferation (Ki-67) using immunofluorescence or immunohistochemistry.

Results

L-IOP eyes showed a larger SC area, higher eNOS expression, and lower KLF4 and F-actin expression in the TM and SC (both P < 0.05) than control eyes. The aqueous humor of L-IOP eyes had a higher abundance of fibrotic proteins and apoptotic cells than that of control eyes, with significantly higher TGF-β1, α-SMA, fibronectin, and cleaved caspase-3 expression (all P < 0.05).

Conclusions

In conclusion, a persistence of L-IOP for 2 weeks may contribute to fibrosis in the TM and SC and might be detrimental to conventional AHO in SD rat eyes.

Translational Relevance

Clinicians should consider that aberrant shear force induced by aqueous humor fluctuation may damage AHO outflow channel when treating patients.

Lysophosphatidic Acid Modulates TGF-β2-Induced Biological Phenotype in Human Conjunctival Fibroblasts

BACKGROUND

Although lysophosphatidic acid (LPA) is known to have multiple pathophysiological roles, its contributions to ocular tissues, especially conjunctival fibrogenesis, remain to be elucidated.

METHODS

To study this issue, the effects of LPA on transforming growth factor-β2 (TGF-β2)-induced fibrogenesis of two-dimensional (2D) and three-dimensional (3D) cultures of human conjunctival fibroblasts (HconF) were examined by the following analyses: (1) planar proliferation determined by transepithelial electrical resistance (TEER) and fluorescein isothiocyanate (FITC)-dextran permeability measurements, (2) real-time metabolic analyses, (3) measurements of the size and stiffness of 3D spheroids, and (4) mRNA expression of extracellular matrix (ECM) molecules and their modulators.

RESULTS

LPA had no effect on TGF-β2-induced increase in the planar proliferation of HconF cells. LPA induced a more quiescent metabolic state in 2D HconF cells, but this metabolic suppression by LPA was partially blunted in the presence of TGF-β2. In contrast, LPA caused a substantial decrease in the hardness of 3D HconF spheroids independently of TGF-β2. In agreement with these different LPA-induced effects between 2D and 3D cultured HconF cells, mRNA expressions of ECM and their modulators were differently modulated.

CONCLUSION

The findings that LPA induced the inhibition of both TGF-β2-related and -unrelated subepithelial proliferation of HconF cells may be clinically applicable.

Pharmacological Stimulation of Soluble Guanylate Cyclase Counteracts the Profibrotic Activation of Human Conjunctival Fibroblasts

Conjunctival fibrosis is a serious clinical concern implicated in a wide spectrum of eye diseases, including outcomes of surgery for pterygium and glaucoma. It is mainly driven by chronic inflammation that stimulates conjunctival fibroblasts to differentiate into myofibroblasts over time, leading to abnormal wound healing and scar formation. Soluble guanylate cyclase (sGC) stimulation was found to suppress transforming growth factor β (TGFβ)-induced myofibroblastic differentiation in various stromal cells such as skin and pulmonary fibroblasts, as well as corneal keratocytes. Here, we evaluated the in vitro effects of stimulation of the sGC enzyme with the cell-permeable pyrazolopyridinylpyrimidine compound BAY 41-2272 in modulating the TGFβ1-mediated profibrotic activation of human conjunctival fibroblasts. Cells were pretreated with the sGC stimulator before challenging with recombinant human TGFβ1, and subsequently assayed for viability, proliferation, migration, invasiveness, myofibroblast marker expression, and contractile properties. Stimulation of sGC significantly counteracted TGFβ1-induced cell proliferation, migration, invasiveness, and acquisition of a myofibroblast-like phenotype, as shown by a significant downregulation of FAP, ACTA2, COL1A1, COL1A2, FN1, MMP2, TIMP1, and TIMP2 mRNA levels, as well as by a significant reduction in α-smooth muscle actin, N-cadherin, COL1A1, and FN-EDA protein expression. In addition, pretreatment with the sGC stimulator was capable of significantly dampening TGFβ1-induced acquisition of a contractile phenotype by conjunctival fibroblasts, as well as phosphorylation of Smad3 and release of the proinflammatory cytokines IL-1β and IL-6. Taken together, our findings are the first to demonstrate the effectiveness of pharmacological sGC stimulation in counteracting conjunctival fibroblast-to-myofibroblast transition, thus providing a promising scientific background to further explore the feasibility of sGC stimulators as potential new adjuvant therapeutic compounds to treat conjunctival fibrotic conditions.

MiR-29b Downregulation by p53/Sp1 Complex Plays a Critical Role in Bleb Scar Formation After Glaucoma Filtration Surgery

Purpose

To investigate the function and mechanism of tumor protein p53 in pathological scarring after glaucoma filtration surgery (GFS) using human Tenon's fibroblasts (HTFs) and a rabbit GFS model.

Methods

The expression of p53 in bleb scarring after GFS and transforming growth factor-β (TGF-β)-induced HTFs (myofibroblasts [MFs]) was examined by western blot and immunochemical analysis. The interaction between p53 and specificity protein 1 (Sp1) was investigated by immunoprecipitation. The role of p53 and Sp1 in the accumulation of collagen type I alpha 1 chain (COL1A1) and the migration of MFs was evaluated by western blot, quantitative real-time polymerase chain reaction (qRT-PCR), wound healing, and Transwell assay. The regulatory mechanisms among p53/Sp1 and miR-29b were detected via qRT-PCR, western blot, luciferase reporter assay, and chromatin immunoprecipitation assay. The therapeutic effect of mithramycin A, a specific inhibitor of Sp1, on scarring formation was evaluated in a rabbit GFS model.

Results

p53 was upregulated in bleb scar tissue and MFs. p53 and Sp1 form a transcription factor complex that induces the accumulation of COL1A1 and promotes the migration of MFs through downregulation of miR-29b, a known suppressor of COL1A1. The p53/Sp1 axis inhibits miR-29b expression by the direct binding promoter of the miR-29b gene. Mithramycin A treatment attenuated bleb scar formation in vivo.

Conclusions

The p53/Sp1/miR-29b signaling pathway plays a critical role in bleb scar formation after GFS. This pathway could be targeted for therapeutic intervention of pathological scarring after GFS.

Translational Relevance

Our research indicates that inhibition of p53/Sp1/miR-29b is a promising therapeutic strategy for preventing post-GFS pathological scarring.

Slow Interstitial Fluid Flow Activates TGF-β Signaling and Drives Fibrotic Responses in Human Tenon Fibroblasts

BACKGROUND

Fibrosis limits the success of filtering glaucoma surgery. We employed 2D and 3D in vitro models to assess the effects of fluid flow on human tenon fibroblasts (HTF).

METHODS

HTF were exposed to continuous or pulsatile fluid flow for 48 or 72 h, at rates expected at the transscleral outflow site after filtering surgery. In the 2D model, the F-actin cytoskeleton and fibronectin 1 (FN1) were visualized by confocal immunofluorescence microscopy. In the 3D model, mRNA and whole cell lysates were extracted to analyze the expression of fibrosis-associated genes by qPCR and Western blot. The effects of a small-molecule inhibitor of the TGF-β receptor ALK5 were studied.

RESULTS

Slow, continuous fluid flow induced fibrotic responses in the 2D and 3D models. It elicited changes in cell shape, the F-actin cytoskeleton, the deposition of FN1 and activated the intracellular TGF-β signaling pathway to induce expression of fibrosis-related genes, such as CTGF, FN1 and COL1A1. ALK5-inhibition reduced this effect. Intermittent fluid flow also induced fibrotic changes, which decreased with increasing pause duration.

CONCLUSIONS

Slow interstitial fluid flow is sufficient to induce fibrosis, could underlie the intractable nature of fibrosis following filtering glaucoma surgery and might be a target for antifibrotic therapy.

Full thickness 3D in vitro conjunctiva model enables goblet cell differentiation

In vitro culture and generation of highly specialized goblet cells is still a major challenge in conjunctival 3D in vitro equivalents. A model comprising all physiological factors, including mucus-secreting goblet cells has the potential to act as a new platform for studies on conjunctival diseases. We isolated primary conjunctival epithelial cells and fibroblasts from human biopsies. 3D models were generated from either epithelial layers or a combination of those with a connective tissue equivalent. Epithelial models were investigated for marker expression and barrier function. Full-thickness models were analyzed for goblet cell morphology and marker expression via immunofluorescence and quantitative real-time PCR. Simple epithelial models cultured at the air-liquid interface showed stratified multi-layer epithelia with pathologic keratinization and without goblet cell formation. The combination with a connective tissue equivalent to generate a full-thickness model led to the formation of a non-keratinized stratified multi-layer epithelium and induced goblet cell differentiation. In our model, a high resemblance to natural conjunctiva was achieved by the combination of conjunctival epithelial cells with fibroblasts embedded in a collagen-hydrogel as connective tissue equivalent. In the future, our conjunctival in vitro equivalent enables the investigation of goblet cell differentiation, conjunctival pathologies as well as drug testing.

Quantitative systems pharmacology of the eye: Tools and data for ocular QSP

Good eyesight belongs to the most-valued attributes of health, and diseases of the eye are a significant healthcare burden. Case numbers are expected to further increase in the next decades due to an aging society. The development of drugs in ophthalmology, however, is difficult due to limited accessibility of the eye, in terms of drug administration and in terms of sampling of tissues for drug pharmacokinetics (PKs) and pharmacodynamics (PDs). Ocular quantitative systems pharmacology models provide the opportunity to describe the distribution of drugs in the eye as well as the resulting drug-response in specific segments of the eye. In particular, ocular physiologically-based PK (PBPK) models are necessary to describe drug concentration levels in different regions of the eye. Further, ocular effect models using molecular data from specific cellular systems are needed to develop dose-response correlations. We here describe the current status of PK/PBPK as well as PD models for the eyes and discuss cellular systems, data repositories, as well as animal models in ophthalmology. The application of the various concepts is highlighted for the development of new treatments for postoperative fibrosis after glaucoma surgery.

Deuterated polyunsaturated fatty acids provided protection against oxidative stress in ocular fibroblasts derived from glaucoma patients

Glaucoma is a complex neurodegenerative disease of the optic nerve that leads to irreversible sight loss. Lowering intraocular pressure (IOP) medically or surgically represents the mainstay of treatment but despite adequate treatment optic nerve function can continue to deteriorate leading to blindness. There is significant clinical and experimental evidence that oxidative stress is involved in the pathogenesis of glaucoma. Decreasing the formation of lipid peroxidation products or scavenging them chemically could be beneficial in limiting the deleterious effects of oxidative stress in glaucoma. A solution to control the susceptibility of PUFAs to noxious lipid peroxidation reactions is by regioselective deuteration. Deuterium incorporated into PUFAs at bis-allylic positions (D-PUFAs) inhibits the rate-limiting step of lipid peroxidation. In this study, we have shown that Tenon's ocular fibroblasts from glaucoma patients have significantly increased basal oxidative stress compared to non-glaucomatous control patients. Furthermore, we have shown that deuterated polyunsaturated fatty acids (D-PUFAs) provide an enhanced rescue of menadione induced lipid peroxidation in both non-glaucomatous and glaucomatous Tenon's ocular fibroblasts using malondialdehyde (MDA) levels as a marker. Our study suggests that D-PUFAs may provide a potentially safe and effective method to reduce cytotoxic oxidative stress in glaucoma.

Understanding Inflammation-associated Ophthalmic Pathologies: A Novel 3D Co-culture Model of Monocyte-myofibroblast Immunomodulation

PURPOSE

Inflammation is associated with, and may be causal of, a variety of ophthalmic pathologies. These pathologies are currently difficult to model in vitro because they involve complex interactions between the innate immune system, stromal cells, and other cells that normally maintain ocular tissue homeostasis. Using transscleral drainage channel fibrosis after glaucoma surgery as an example of inflammation-associated ocular fibrosis, we have assessed a simple but novel 3D cell culture system designed to reveal the immunomodulatory impacts of ocular connective tissue cells on monocytes, a major cellular component of the circulating immune system.

METHODS

Primary human Tenon's capsule fibroblasts derived from five unrelated patients were activated into myofibroblasts in 3D collagen matrices under isometric tension, with and without exposure to an inflammatory cytokine-enhanced milieu, and co-cultured with an immortalized human monocyte cell line (THP-1 cells). Quantitative PCR analyses were performed on 8 candidate genes to assess the impacts of inflammatory cytokines on the myofibroblasts and the monocytes in mono-cultures and compared to cells in co-culture to clearly distinguish any co-culture-induced impacts on gene expression.

RESULTS

Our data indicate that both Tenon's capsule myofibroblasts in 3D mono-culture and THP-1 monocytes in suspension mono-culture were responsive to inflammatory cytokine stimuli. Co-culture with Tenon's capsule myofibroblasts significantly modulated the gene expression responses of THP-1 monocytes to inflammatory cytokine stimulation, indicative of an immunomodulatory "feedback" system between these cell types.

CONCLUSION

Our findings provide proof of principle for the use of simple 3D co-culture systems as a means to enhance our understanding of ocular stromal cell interactions with cells of the innate immune system and to provide more informative in vitro models of inflammation-associated ophthalmic pathologies.

Capsulectomy Shunt Revision versus Repeat Shunt Implantation Following Ahmed Glaucoma Valve Failure in Refractory Glaucoma

PURPOSE

To investigate the efficacy of capsulectomy shunt revision (CSR) compared with the implantation of a second Ahmed glaucoma valve (re-AGV) in glaucoma patients with failed shunts.

DESIGN

Quasi-experimental study.

SUBJECTS

Forty-six eyes with failed Ahmed glaucoma valves (AGVs) were included in the study; 25 underwent CSR, whereas 21 underwent re-AGV.

METHODS

Patients were scheduled for CSR or re-AGV based on the appearance and accessibility of the existing AGV versus the feasibility for re-AGV in other quadrants. The CSR involved incision and dissection down to the thick fibrous capsule around the AGV plate, which was excised extensively. For re-AGV, the second shunt was implanted in the supranasal or infranasal quadrants.

MAIN OUTCOME MEASURES

Surgical success, defined as intraocular pressure (IOP) > 5 mmHg, ≤ 21 mmHg, IOP reduction ≥ 20% from baseline, and no reoperation for glaucoma. Secondary outcome measures were IOP, number of glaucoma medications, and complications during a 12-month follow-up period.

RESULTS

Mean IOP was significantly lower than preoperative values at all time points in both study groups (P < 0.001). Intraocular pressure decreased significantly from 28.3 ± 5.04 mmHg at baseline to 16.4 ± 2.4 mmHg at final follow-up in the capsulectomy group (P = 0.002). Corresponding IOP values for re-AGV were 30.99 ± 6.2 and 13.6 ± 3.8 mmHg, respectively (P = 0.001). Intraocular pressure in the CSR group was higher than re-AGV during the study (P = 0.003). The cumulative probability of success at 12 months was significantly higher in the re-AGV group (87.5% vs 53.3%, P = 0.002). There was no significant difference in the number of glaucoma medications and overall complications rate between the study groups. Wound leakage was the only complication more common in the CSR group (P = 0.012).

CONCLUSION

In the eyes with a failed AGV, re-AGV and CSR are both effective. Implantation of a second shunt seems more effective than the surgical revision of an existing device; however, the latter procedure may be a viable option in selected cases.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Anti-glaucoma medications lowered decorin and altered profibrotic proteins in human tenon's fibroblasts

Long term exposure to anti-glaucoma medications (AGMs) leads to an increase in extracellular matrix (ECM) accumulation in primary glaucoma patients. This study aims to evaluate the effect of topical AGMs in primary human tenon's fibroblasts (HTFs) and analyze the expression of profibrotic and anti-fibrotic proteins. Primary HTFs were cultured from patients undergoing cataract (control) and trabeculectomy. The different types of AGMs in single/multiple combinations (BB, PG, AA, CAI, CH, combinations of 3- PG + AA + CAI, 4A- BB + PG + AA + CAI, 4B- BB + PG + CAI + CH and 5- BB + PG + AA + CAI + CH) on chronic exposure were tested for cell viability using MTT assay and morphological alterations. Profibrotic proteins mainly SPARC, LOXL2, COL1A1 and anti-fibrotic DCN were analyzed in treated HTFs using q-PCR and ELISA. Sirius red staining and collagen gel contraction (CGC) assay were performed to assess collagen synthesis and the contractility of HTFs, respectively. Except for AA and CH, the other AGMs at a higher concentration were found to decrease the cell viability of HTFs. The morphology of HTFs were altered on exposure to BB, CH and AA; Profibrotic proteins i.e., SPARC, LOXL2 and COL1A1 were significantly increased (p < 0.05) on exposure to a combination of AGMs with TGF-β1, whereas the anti-fibrotic DCN expression was significantly lowered (p < 0.05) in single/multiple AGM exposure. Sirius red staining showed increased collagen synthesis with combinations of AGMs with TGF-β1. Meanwhile, HTFs showed increased collagen gel contraction with TGF-β1, CAI and CH. This study reveals that altered profibrotic proteins, with significantly lowered DCN on chronic exposure of AGMs in HTFs.

Open Conjunctival Approach for Sub-Tenon's Xen Gel Stent Placement and Bleb Morphology by Anterior Segment Optical Coherence Tomography

PRCIS

Sub-Tenon's implantation of the Xen Gel stent resulted in significant intraocular pressure (IOP) lowering along with a low rate of postoperative bleb needling, and a favorable bleb morphology on anterior segment optical coherence tomography (AS-OCT).

PURPOSE

The aim was to assess clinical outcomes and bleb morphology following sub-Tenon's implantation of the Xen Gel Stent.

METHODS

The medical records of patients who underwent sub-Tenon's Xen Gel Stent implantation with intraoperative mitomycin-C through an open conjunctival approach were reviewed. Postoperative IOP and number of glaucoma medications at 1, 3, 6, 9, and 12 months were assessed. Bleb morphology was analyzed at various timepoints using AS-OCT (Topcon DRI OCT version 1.1.1).

RESULTS

Twenty-six eyes were included in the study. Mean age was 69.4±8.0 years. Mean preoperative IOP was 28.1±7.8 mm Hg on an average of 3.5±0.9 glaucoma medications. Mean IOP at postoperative month 12 (n=23 eyes) was 12.9±4.0 mm Hg (P<0.01) on an average of 0.3±0.6 (P<0.01) glaucoma medications. Three eyes (12%) required postoperative needle revision. Bleb morphology in the early postoperative period (≤3 mo) was characterized by multiple small subconjunctival microcysts on AS-OCT. At the intermediate (6 to 12 mo) and long-term (>12 mo) timepoints, reduction in microcysts with multiple internal parallel layers of aqueous flow and a uniform pattern were more frequently noted. All functional blebs were characterized by the presence of a posterior episcleral fluid lake. Failed blebs showed absence of aqueous humor around the distal end of the microshunt.

CONCLUSION

Following an open conjunctival approach, sub-Tenon's placement of the Xen Gel Stent with significant IOP lowering was achieved. In eyes with good shunt function, bleb morphology by AS-OCT showed a posterior episcleral fluid lake similar to findings following trabeculectomy.

Mechanosensitive pathways are regulated by mechanosensitive miRNA clusters in endothelial cells

Shear stress is known to affect many processes in (patho-) physiology through a complex, multi-molecular mechanism, termed mechanotransduction. The sheer complexity of the process has raised questions how mechanotransduction is regulated. Here, we comprehensively evaluate the literature about the role of small non-coding miRNA in the regulation of mechanotransduction. Regulation of mRNA by miRNA is rather complex, depending not only on the concentration of mRNA to miRNA, but also on the amount of mRNA competing for a single mRNA. The only mechanism to counteract the latter factor is through overarching structures of miRNA. Indeed, two overarching structures are present miRNA families and miRNA clusters, and both will be discussed in details, regarding the latest literature and a previous conducted study focussed on mechanotransduction. Both the literature and our own data support a new hypothesis that miRNA-clusters predominantly regulate mechanotransduction, affecting 65% of signalling pathways. In conclusion, a new and important mode of regulation of mechanotransduction is proposed, based on miRNA clusters. This finding implicates new avenues for treatment of mechanotransduction and atherosclerosis.

A Tenon's capsule/bulbar conjunctiva interface biomimetic to model fibrosis and local drug delivery

Glaucoma filtration surgery is one of the most effective methods for lowering intraocular pressure in glaucoma. The surgery efficiently reduces intra-ocular pressure but the most common cause of failure is scarring at the incision site. This occurs in the conjunctiva/Tenon’s capsule layer overlying the scleral coat of the eye. Currently used antimetabolite treatments to prevent post-surgical scarring are non-selective and are associated with potentially blinding side effects. Developing new treatments to target scarring requires both a better understanding of wound healing and scarring in the conjunctiva, and new means of delivering anti-scarring drugs locally and sustainably. By combining plastic compression of collagen gels with a soft collagen-based layer, we have developed a physiologically relevant model of the sub-epithelial bulbar conjunctiva/Tenon’s capsule interface, which allows a more holistic approach to the understanding of subconjunctival tissue behaviour and local drug delivery. The biomimetic tissue hosts both primary human conjunctival fibroblasts and an immune component in the form of macrophages, morphologically and structurally mimicking the mechanical proprieties and contraction kinetics of ex vivo porcine conjunctiva. We show that our model is suitable for the screening of drugs targeting scarring and/or inflammation, and amenable to the study of local drug delivery devices that can be inserted in between the two layers of the biomimetic. We propose that this multicellular-bilayer engineered tissue will be useful to study complex biological aspects of scarring and fibrosis, including the role of inflammation, with potentially significant implications for the management of scarring following glaucoma filtration surgery and other anterior ocular segment scarring conditions. Crucially, it uniquely allows the evaluation of new means of local drug delivery within a physiologically relevant tissue mimetic, mimicking intraoperative drug delivery in vivo.