Shandiz Tehrani

Astrocyte Processes Label for Filamentous Actin and Reorient Early Within the Optic Nerve Head in a Rat Glaucoma Model

PURPOSE To determine if astrocyte processes label for actin and to quantify the orientation of astrocytic processes within the optic nerve head (ONH) in a rat glaucoma model. METHODS Chronic intraocular pressure (IOP) elevation was produced by episcleral hypertonic saline injection and tissues were collected after 5 weeks. For comparison, eyes with optic nerve transection were collected at 2 weeks. Fellow eyes served as controls. Axonal degeneration in retrobulbar optic nerves was graded on a scale of 1 to 5. Optic nerve head sections (n ≥ 4 eyes per group) were colabeled with phalloidin (actin marker) and antibodies to astrocytic glial fibrillary acidic protein and aquaporin 4, or axonal tubulin βIII. Confocal microscopy and FIJI software were used to quantify the orientation of actin bundles. RESULTS Control ONHs showed stereotypically arranged actin bundles within astrocyte processes. Optic nerve head actin bundle orientation was nearly perpendicular to axons (82.9° ± 6.3° relative to axonal axis), unlike the retrobulbar optic nerve (45.4° ± 28.7°, P < 0.05). With IOP elevation, ONH actin bundle orientation became less perpendicular to axons, even in eyes with no perceivable axonal injury (i.e., 38.8° ± 15.1° in grade 1, P < 0.05 in comparison to control ONHs). With severe injury, ONH actin bundle orientation became more parallel to the axonal axis (24.1° ± 28.4°, P < 0.05 in comparison to control ONHs). Optic nerve head actin bundle orientation in transected optic nerves was unchanged. CONCLUSIONS Actin labeling identifies fine astrocyte processes within the ONH. Optic nerve head astrocyte process reorientation occurs early in response to elevated IOP.

Gender Difference in the Pathophysiology and Treatment of Glaucoma

Abstract Glaucoma is the principal cause of irreversible blindness in the world, the second leading cause of blindness in the United States, and it results in optic nerve head axonal degeneration and corresponding visual field deficits. Intraocular pressure (IOP) is the only known modifiable risk factor in glaucoma. Non-modifiable risk factors for glaucoma include age, ethnicity, central corneal thickness, and family history. While our understanding of the role of gender as a risk factor in glaucoma development and progression remains nascent, multiple observations have shown gender differences in the incidence and prevalence of glaucoma. Depending on the type of glaucoma, hormone therapy, oral contraceptive use and menopausal status have also been associated with glaucoma. In addition, pregnancy leads to changes in IOP, while the treatment of glaucoma must be tailored based on the systemic effects of topical therapeutics on the mother and fetus. This review will focus on the epidemiologic, anatomic and endocrinologic differences in male and female glaucoma patients. In addition, this review will discuss treatment modalities that may be more appropriate for one gender than the other, especially with respect to a woman’s pregnancy status.

Astrocyte Structural and Molecular Response to Elevated Intraocular Pressure Occurs Rapidly and Precedes Axonal Tubulin Rearrangement within the Optic Nerve Head in a Rat Model.

Glaucomatous axon injury occurs at the level of the optic nerve head (ONH) in response to uncontrolled intraocular pressure (IOP). The temporal response of ONH astrocytes (glial cells responsible for axonal support) to elevated IOP remains unknown. Here, we evaluate the response of actin-based astrocyte extensions and integrin-based signaling within the ONH to 8 hours of IOP elevation in a rat model. IOP elevation of 60 mm Hg was achieved under isoflurane anesthesia using anterior chamber cannulation connected to a saline reservoir. ONH astrocytic extension orientation was significantly and regionally rearranged immediately after IOP elevation (inferior ONH, 43.2° ± 13.3° with respect to the anterior-posterior axis versus 84.1° ± 1.3° in controls, p<0.05), and re-orientated back to baseline orientation 1 day post IOP normalization. ONH axonal microtubule filament label intensity was significantly reduced 1 and 3 days post IOP normalization, and returned to control levels on day 5. Phosphorylated focal adhesion kinase (FAK) levels steadily decreased after IOP normalization, while levels of phosphorylated paxillin (a downstream target of FAK involved in focal adhesion dynamics) were significantly elevated 5 days post IOP normalization. The levels of phosphorylated cortactin (a downstream target of Src kinase involved in actin polymerization) were significantly elevated 1 and 3 days post IOP normalization and returned to control levels by day 5. No significant axon degeneration was noted by morphologic assessment up to 5 days post IOP normalization. Actin-based astrocyte structure and signaling within the ONH are significantly altered within hours after IOP elevation and prior to axonal cytoskeletal rearrangement, producing some responses that recover rapidly and others that persist for days despite IOP normalization.

A period of controlled elevation of IOP (CEI) produces the specific gene expression responses and focal injury pattern of experimental rat glaucoma

Purpose We determine if several hours of controlled elevation of IOP (CEI) will produce the optic nerve head (ONH) gene expression changes and optic nerve (ON) damage pattern associated with early experimental glaucoma in rats. Methods The anterior chambers of anesthetized rats were cannulated and connected to a reservoir to elevate IOP. Physiologic parameters were monitored. Following CEI at various recovery times, ON cross-sections were graded for axonal injury. Anterior ONHs were collected at 0 hours to 10 days following CEI and RNA extracted for quantitative PCR measurement of selected messages. The functional impact of CEI was assessed by electroretinography (ERG). Results During CEI, mean arterial pressure (99 ± 6 mm Hg) and other physiologic parameters remained stable. An 8-hour CEI at 60 mm Hg produced significant focal axonal degeneration 10 days after exposure, with superior lesions in 83% of ON. Message analysis in CEI ONH demonstrated expression responses previously identified in minimally injured ONH following chronic IOP elevation, as well as their sequential patterns. Anesthesia with cannulation at 20 mm Hg did not alter these message levels. Electroretinographic A- and B-waves, following a significant reduction at 2 days after CEI, were fully recovered at 2 weeks, while peak scotopic threshold response (pSTR) remained mildly but significantly depressed. Conclusions A single CEI reproduces ONH message changes and patterns of ON injury previously observed with chronic IOP elevation. Controlled elevation of IOP can allow detailed determination of ONH cellular and functional responses to an injurious IOP insult and provide a platform for developing future therapeutic interventions.

The Utility of Diaton Tonometer Measurements in Patients With Ocular Hypertension, Glaucoma, and Glaucoma Tube Shunts: A Preliminary Study for its Potential Use in Keratoprosthesis Patients.

Purpose:Glaucoma is common in patients with the Boston type 1 keratoprosthesis (KPro). Because of the inability to perform corneal applanation in KPro patients, digital palpation is currently the mainstay for assessment of intraocular pressure (IOP). The purpose of this study was to determine whether the Diaton tonometer, which estimates IOP through transpalpebral scleral indentation, can reasonably detect high IOP when compared with Goldmann applanation tonometry (GAT) in patients with ocular hypertension, glaucoma, or glaucoma tube shunts. If reliable in these patients, it may be helpful in patients with KPros. Materials and Methods:We prospectively measured IOP using GAT and Diaton transpalpebral tonometry (DTT) on the upper and lower eyelids in 87 eyes of 57 adult participants with ocular hypertension and glaucoma, several of whom had glaucoma tube shunts. Results:The correlation coefficient between GAT and DTT on the upper eyelid was 0.64 (P<0.0001). For detecting an IOP of >21 mm Hg as measured by GAT, DTT on the upper eyelid had a sensitivity and specificity of 65% and 81%, respectively. The positive and negative predictive values were 74% and 73%, respectively. Bland-Altman analysis demonstrated limits of agreement of 2.0±19.5 mm Hg for GAT versus DTT on the upper eyelid. The presence of a tube shunt did not significantly affect the results. Conclusions:Diaton tonometry has a large margin of error compared with GAT in patients with ocular hypertension, glaucoma, and glaucoma tube shunts. However, given the current lack of an objective and quantitative method of IOP measurement in KPro patients, Diaton tonometry may be useful in this population as a supplement to digital palpation.

Thin Central Corneal Thickness and Early-Onset Glaucoma in Lacrimo-auriculo-dento-digital Syndrome

Thin Central Corneal Thickness and Early-Onset Glaucoma in Lacrimo-auriculo-dento-digital Syndrome Thin central corneal thickness (CCT) is a well-established risk factor for glaucoma development and progression.1 Lacrimoauriculo-dento-digital (LADD) syndrome is an autosomal dominant syndrome associated with multiple congenital anomalies.2,3 We describe a young patient with LADD syndrome who had extremely thin CCT and severe open-angle glaucoma.

In Vivo Small Molecule Delivery to the Optic Nerve in a Rodent Model

Small molecule delivery to the optic nerve would allow for exploration of molecular and cellular pathways involved in normal physiology and optic neuropathies such as glaucoma, and provide a tool for screening therapeutics in animal models. We report a novel surgical method for small molecule drug delivery to the optic nerve head (ONH) in a rodent model. In proof-of-principle experiments, we delivered cytochalasin D (Cyt D; a filamentous actin inhibitor) to the junction of the superior optic nerve and globe in rats to target the actin-rich astrocytic cytoskeleton of the ONH. Cyt D delivery was quantified by liquid chromatography and mass spectrometry of isolated optic nerve tissue. One day after Cyt D delivery, anterior ONH filamentous actin bundle content was significantly reduced as assessed by fluorescent-tagged phalloidin labeling, relative to sham delivery. Anterior ONH nuclear counts and axon-specific beta-3 tubulin levels, as well as peripapillary retinal ganglion cell layer nuclear counts were not significantly altered after Cyt D delivery relative to sham delivery. Lastly, the surgical delivery technique caused minimal observable axon degeneration up to 10 days post-surgery. This small molecule delivery technique provides a new approach to studying optic neuropathies in in vivo rodent models.

Unilateral Double Optic Nerve Head Pits

Presented in part at: the International Society of Ocular Oncology meeting, March 24e28, 2017, Sydney, Australia. Financial Disclosure(s): The author(s) have made the following disclosure(s): A.H.S.: Consultant e Castle Biosciences Inc. D.S.G.: Travel compensation and Coeprincipal investigator: Children’s Oncology Group trial; Travel compensation and consultant e American Board of Ophthalmology; Consultant e AbbVie, Aura Biosciences, American Society of Clinical Oncology, Castle Biosciences; Grantse Housemann/ Wilkins Foundation and Lois Kuss Fund for Glaucoma Research. B.L.G.: Unpaid Medical Director of Ocular Oncology at Impact Genetics; Employed e Hospital for Sick Children; Expert testimony e legal cases; Grants pending e Retina Society; Travel expenses e SickKids, and reports a pension. B.P.M.: Consultant to, holds stock in, and receives travel expenses e Aura Biosciences. S.E.P.: Member of the Scientific Advisory Board e Baylor Miraca Genetics Laboratories; Grants pending e National Institutes of Health; Royalties e Antibody Users; Travel expenses e American Association of Cancer Research.