Distinct iris gene expression profiles of primary angle closure glaucoma and primary open angle glaucoma and their interaction with ocular biometric parameters.

BACKGROUND: This study aimed to evaluate differences in iris gene expression profiles between primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG) and their interaction with biometric characteristics. DESIGN: Prospective study. PARTICIPANTS: Thirty-five subjects with PACG and thirty-three subjects with POAG who required trabeculectomy were enrolled at the Singapore National Eye Centre, Singapore. METHODS: Iris specimens, obtained by iridectomy, were analysed by real-time polymerase chain reaction for expression of type I collagen, vascular endothelial growth factor (VEGF)-A, -B and -C, as well as VEGF receptors (VEGFRs) 1 and 2. Anterior segment optical coherence tomography (ASOCT) imaging for biometric parameters, including anterior chamber depth (ACD), anterior chamber volume (ACV) and lens vault (LV), was also performed pre-operatively. MAIN OUTCOME MEASURES: Relative mRNA levels between PACG and POAG irises, biometric measurements, discriminant analyses using genes and biometric parameters. RESULTS: COL1A1, VEGFB, VEGFC and VEGFR2 mRNA expression was higher in PACG compared to POAG irises. LV, ACD and ACV were significantly different between the two subgroups. Discriminant analyses based on gene expression, biometric parameters or a combination of both gene expression and biometrics (LV and ACV), correctly classified 94.1%, 85.3% and 94.1% of the original PACG and POAG cases, respectively. The discriminant function combining genes and biometrics demonstrated the highest accuracy in cross-validated classification of the two glaucoma subtypes. CONCLUSIONS: Distinct iris gene expression supports the pathophysiological differences that exist between PACG and POAG. Biometric parameters can combine with iris gene expression to more accurately define PACG from POAG.

Validation of the glaucoma filtration surgical mouse model for antifibrotic drug evaluation.

Glaucoma is a progressive optic neuropathy, which, if left untreated, leads to blindness. The most common and most modifiable risk factor in glaucoma is elevated intraocular pressure (IOP), which can be managed surgically by filtration surgery. The postoperative subconjunctival scarring response, however, remains the major obstacle to achieving long-term surgical success. Antiproliferatives such as mitomycin C are commonly used to prevent postoperative scarring. Efficacy of these agents has been tested extensively on monkey and rabbit models of glaucoma filtration surgery. As these models have inherent limitations, we have developed a model of glaucoma filtration surgery in the mouse. We show, for the first time, that the mouse model typically scarred within 14 d, but when augmented with mitomycin C, more animals maintained lower intraocular pressures for a longer period of time concomitant with prolonged bleb survival to beyond 28 d. The morphology of the blebs following mitomycin C treatment also resembled well-documented clinical observations, thus confirming the validity and clinical relevance of this model. We demonstrate that the antiscarring response to mitomycin C is likely to be due to its effects on conjunctival fibroblast proliferation, apoptosis and collagen deposition and the suppression of inflammation. Indeed, we verified some of these properties on mouse conjunctival fibroblasts cultured in vitro. These data support the suitability of this mouse model for studying the wound healing response in glaucoma filtration surgery, and as a potentially useful tool for the in vivo evaluation of antifibrotic therapeutics in the eye.

Multiple DNA-binding sites in Tetrahymena telomerase.

Telomerase is a ribonucleoprotein enzyme that maintains chromosome ends through de novo addition of telomeric DNA. The ability of telomerase to interact with its DNA substrate at sites outside its catalytic centre ('anchor sites') is important for its unique ability to undergo repeat addition processivity. We have developed a direct and quantitative equilibrium primer-binding assay to measure DNA-binding affinities of regions of the catalytic protein subunit of recombinant Tetrahymena telomerase (TERT). There are specific telomeric DNA-binding sites in at least four regions of TERT (the TEN, RBD, RT and C-terminal domains). Together, these sites contribute to specific and high-affinity DNA binding, with a K(d) of approximately 8 nM. Both the K(m) and K(d) increased in a stepwise manner as the primer length was reduced; thus recombinant Tetrahymena telomerase, like the endogenous enzyme, contains multiple anchor sites. The N-terminal TEN domain, which has previously been implicated in DNA binding, shows only low affinity binding. However, there appears to be cooperativity between the TEN and RNA-binding domains. Our data suggest that different DNA-binding sites are used by the enzyme during different stages of the addition cycle.

Valproic acid exerts specific cellular and molecular anti-inflammatory effects in post-operative conjunctiva.

Valproic acid (VPA) is a histone deacetylase inhibitor used clinically for neurological disorders. It is also potentially useful as anti-fibrotic therapy as it reduced collagen deposition in the post-operative conjunctiva. In this study, we further evaluated the effects of VPA on post-operative inflammation using the mouse model of conjunctival scarring. VPA, injected into the subconjunctiva immediately after surgery, did not cause any adverse tissue response when examined by live microscopy and produced an apparent reduction of proinflammatory and proangiogenic markers in immunohistological examinations. In-depth analyses of the treated operated tissues revealed that VPA selectively inhibited the CD45highF4/80low macrophage subset as well as the production of specific proinflammatory cytokines/ chemokines, including CXCL1, IL-5, IL-6, and IL-10 which were reduced by ≥ 2.0-fold. VPA also specifically reduced tissue NF-кB2 p100 protein by mean 3.87-fold. On conjunctival fibroblasts, VPA treatment resulted in decreased secretion of specific cytokines, including CCL2, VEGF-A, and IL-15. In the presence of TNF-α, VPA inhibited the induction of specific cytokines/chemokines, notably CCL5 and VEGF-A, as well as NF-кB2 p100. In corroboration, VPA suppressed TNF-α stimulation of NF-кB reporter transcription by 1.51-fold. These data indicate that VPA can modulate both proinflammatory cellular and molecular targets in a selective manner and may therefore attenuate surgery-induced conjunctival inflammation. These and previous findings suggest that, by suppressing key mediators of both inflammation and fibrosis, VPA is a useful therapeutic for improving surgical outcome involving the conjunctiva. KEY MESSAGES: VPA inhibited recruitment of a CD45highF4/80low macrophage subset. VPA reduced chemokine and cytokine levels in treated tissues. VPA selectively suppressed tissue NF-кB2 p100 levels. VPA suppressed TNF-α induction of chemokines, cytokines and NF-кB2 p100 expression. VPA suppressed TNF-α stimulation of NF-кB reporter.

Bevacizumab Promotes T-Cell-Mediated Collagen Deposition in the Mouse Model of Conjunctival Scarring.

Purpose: We determine the effects of bevacizumab on collagen production in a mouse model of conjunctival scarring. Methods: Experimental surgery was performed as described for the mouse model of conjunctival scarring, and bevacizumab was introduced by conjunctival injection. The capacity of bevacizumab to recognize conjunctival VEGF-A was determined by ELISA. Col1a1 was measured by real-time PCR and immunoblotting. T cells and collagen were visualized by immunofluorescence and picrosirius red staining of bleb cryosections. Conjunctival CD4+ or CD8a+ T cells were counted by flow cytometry. Mouse splenic T cells were cultured with bevacizumab/IgG and their numbers, cell cycle, and collagen production were measured using a cell counter, flow cytometry, and sircol soluble collagen assay, respectively. Reconstitution experiments in severe combined immunodeficiency (SCID) mice were performed by injection of freshly isolated T cells on day 2 postoperatively. Results: Bevacizumab recognized approximately 20% of endogenous murine VEGF-A. Injection of bevacizumab raised Col1a1 expression in the blebs at mRNA and protein levels. Bevacizumab did not induce collagen in conjunctival fibroblasts, but increased CD4+ and CD8a+ cell numbers as well as collagen production by these cells. Collagen appeared to accumulate in the vicinity of T cells in the bevacizumab-treated blebs. While SCID blebs did not show elevated collagen levels, reconstitution with CD4+ or CD8a+ cells resulted in increased Col1a1 expression at mRNA and protein levels. Conclusions: Bevacizumab increased collagen production in the mouse model of conjunctival scarring. This collagen induction was mediated by T cells that were also stimulated by bevacizumab to increase in numbers.

Upregulation of distinct collagen transcripts in post-surgery scar tissue: a study of conjunctival fibrosis.

Excessive accumulation of collagen is often used to assess the development of fibrosis. This study aims to identify collagen genes that define fibrosis in the conjunctiva following glaucoma filtration surgery (GFS). Using the mouse model of GFS, we have identified collagen transcripts that were upregulated in the fibrotic phase of wound healing via RNA-seq. The collagen transcripts that were increased the most were encoded by Col8a1, Col11a1 and Col8a2 Further analysis of the Col8a1, Col11a1 and Col8a2 transcripts revealed their increase by 67-, 54- and 18-fold, respectively, in the fibrotic phase, compared with 12-fold for Col1a1, the most commonly evaluated collagen gene for fibrosis. However, only type I collagen was significantly upregulated at the protein level in the fibrotic phase. Type VIII and type I collagens colocalized in fibrous structures and in ACTA2-positive pericytes, and appeared to compensate for each other in expression levels. Type XI collagen showed low colocalization with both type VIII and type I collagens but can be found in association with macrophages. Furthermore, we show that both mouse and human conjunctival fibroblasts expressed elevated levels of the most highly expressed collagen genes in response to TGFß2 treatment. Importantly, conjunctival tissues from individuals whose GF surgeries have failed due to scarring showed 3.60- and 2.78-fold increases in type VIII and I collagen transcripts, respectively, compared with those from individuals with no prior surgeries. These data demonstrate that distinct collagen transcripts are expressed at high levels in the conjunctiva after surgery and their unique expression profiles may imply differential influences on the fibrotic outcome.

Valproic acid suppresses collagen by selective regulation of Smads in conjunctival fibrosis.

Overproduction of type I collagen is associated with a wide range of fibrotic diseases as well as surgical failure such as in glaucoma filtration surgery (GFS). Its modulation is therefore of clinical importance. Valproic acid (VPA) is known to reduce collagen in a variety of tissues with unclear mechanism of action. In this report, we demonstrate that VPA inhibited collagen production in both conjunctival fibroblasts and the mouse model of GFS. In fibroblasts, VPA decreased type I collagen expression which intensified with longer drug exposure and suppressed steady-state type I collagen promoter activity. Moreover, VPA decreased Smad2, Smad3 and Smad4 but increased Smad6 expression with a similar intensity-exposure profile. Reduction of Smad3 using small hairpin RNA and/or overexpression of Smad6 resulted in decreased collagen expression which was exacerbated when VPA was simultaneously present. Furthermore, fibrogenic TGF-ß2 failed to induce collagen when VPA was present, as opposed to the myofibroblast markers, beta-actin, alpha-smooth muscle actin and tenascin-C, which were elevated by TGF-ß2. VPA suppressed p3TP-Lux luciferase activity and selectively rescued Smad6 expression from suppression by TGF-ß2. Notably, SMAD6 overexpression reduced the effectiveness of TGF-ß2 in inducing collagen expression. In corroboration, VPA inhibited type I collagen but increased Smad6 expression in the late phase of wound healing in the mouse model of GFS. Taken together, our data indicate that VPA has the capacity to effectively suppress both steady-state and fibrogenic activation of type I collagen expression by modulating Smad expression. Hence, VPA is potentially applicable as an anti-fibrotic therapeutic by targeting collagen. Key message: • VPA modulates type I collagen expression via members of the Smad family. • VPA suppresses Smad2, Smad3 and Smad4 but upregulates Smad6. • Smad3 and Smad6 are involved in VPA regulation of steady-state collagen expression. • Smad6 is involved in VPA modulation of TGF-ß-stimulated collagen expression. • VPA reduces collagen and upregulates Smad6 in the mouse model of glaucoma filtration surgery.

Aberrant DNA methylation of matrix remodeling and cell adhesion related genes in pterygium.

BACKGROUND: Pterygium is a common ocular surface disease characterized by abnormal epithelial and fibrovascular proliferation, invasion, and matrix remodeling. This lesion, which migrates from the periphery to the center of the cornea, impairs vision and causes considerable irritation. The mechanism of pterygium formation remains ambiguous, and current treatment is solely surgical excision, with a significant risk of recurrence after surgery. Here, we investigate the role of methylation in DNA sequences that regulate matrix remodeling and cell adhesion in pterygium formation. METHODOLOGY/PRINCIPAL FINDINGS: Pterygium and uninvolved conjunctiva samples were obtained from the same eye of patients undergoing surgery. The EpiTYPER Sequenom technology, based on differential base cleavage and bisulfite sequencing was used to evaluate the extent of methylation of 29 matrix and adhesion related genes. In pterygium, three CpG sites at -268, -32 and -29 bp upstream of transglutaminase 2 (TGM-2) transcription initiation were significantly hypermethylated (p<0.05), whereas hypomethylation was detected at CpGs +484 and +602 bp downstream of matrix metalloproteinase 2 (MMP-2) transcription start site, and -809, -762, -631 and -629 bp upstream of the CD24 transcription start site. RT-qPCR, western blot and immunofluorescent staining showed that transcript and protein expression were reduced for TGM-2 and increased for MMP-2 and CD24. Inhibition of methylation in cultured conjunctival epithelial cells increased these transcripts. CONCLUSIONS/SIGNIFICANCE: We found regions of aberrant DNA methylation which were consistent with alteration of TGM-2, MMP-2, and CD24 transcript and protein expression, and that inhibition of methylation in cultured cells can increase the expression of these genes. Since these genes were related to cell adhesion and matrix remodeling, dysregulation may lead to fibroblastic and neovascular changes and pterygium formation. These results have implications for the prognostication of pterygium in clinical practice, for example, detection of epigenetic changes may have a role in predicting post surgical recurrence of aggressive lesions.