Cytoprotective effect of hyaluronic acid and hydroxypropyl methylcellulose against DNA damage induced by thimerosal in Chang conjunctival cells.

BACKGROUND: To investigate genotoxicity of the preservative thimerosal (Thi), and the cytoprotective and antioxidant effects of hyaluronic Acid (HA) and hydroxypropyl methylcellulose (HPMC) on Chang conjunctival cells. METHOD: Cells were divided into three groups. One group was exposed to Thi at various concentrations (0.00001 %∼0.001 %) for 30 min; the other two groups were pretreated with 0.3 % HA or 0.3 % HPMC for 30 min before the Thi exposure. After cell viability was evaluated, alkaline comet assay and detection of the phosphorylated form of the histone variant H2AX (γH2AX) foci were used to determine DNA damage. Reactive oxygen species (ROS) production was assessed by the fluorescent probe, 2', 7'-dichlorodihydrofluorescein diacetate (DCFH-DA). RESULTS: A significant change of cell viability was observed after exposure to 0.001 % Thi for 30 min. DNA single- and double-strand breaks were significantly increased in a dose-dependent manner with Thi exposure. In addition, intracellular ROS induced by Thi was dose-dependent, except at 0.001 % less ROS was induced than at 0.0005 %. However, cells pretreated with 0.3 % HA or 0.3 % HPMC showed significantly increased cell survival, decreased DNA damage, and decreased ROS production compared to cells exposed to Thi alone. Pretreatment with 0.3 % HA was found to be even more protective than 0.3 % HPMC. CONCLUSION: Thi can induce DNA damage in human conjunctival epithelial cells, probably due to oxidative stress. HA and HPMC are protective agents that have antioxidant properties and can decrease DNA damage induced by Thi. Pretreatment of 0.3 % HA may be more protective of the ocular surface than 0.3 % HPMC.

Exposure rate of unwrapped hydroxyapatite orbital implants in enucleation surgery.

OBJECTIVE: To document the long-term exposure rate of unwrapped coralline hydroxyapatite (HA) orbital implants and explore possible risk factors. DESIGN: This retrospective case series (May 2008-April 2013) reviewed the 234 patients with anophthalmia who underwent insertion of an unwrapped HA orbital implant by one of two different surgical closing techniques. RESULTS: Of the 234 cases, 151 underwent a rectus end-to-end suturing closure technique and 83 underwent a rectus orthotopic suturing closure technique. The time of follow-up ranged from 25 months to 69 months (mean 41.9 months). Implant exposure developed in 11 cases. Three in the rectus end-to-end suturing closure group (2.0%) and eight in the rectus orthotopic suturing closure group (9.6%). In the rectus end-to-end suturing technique, a crosswise fixation of vascularised rectus muscle tissue is formed across the front of the implant; in this group the incidence of implant exposure was reduced (OR=8.11, p=0.013). Prior ocular surgery was found to be a factor increasing the incidence of HA exposure (OR=2.73, p=0.032). CONCLUSIONS: The placement of an unwrapped HA orbital implant with rectus end-to-end suturing in enucleation surgery was associated with a low rate of exposure in most cases. The end-to-end suturing creates a joint-like structure over the HA sphere, protecting the Tenon's capsule and conjunctiva from its rough surface and reducing the risk of implant exposure. Prior ocular surgery may be another risk factor for HA exposure.