In vivo release and retinal toxicity of cyclosporine-loaded intravitreal device.

PURPOSE: To determine the in vivo release profile and retinal safety of cyclosporine A (CsA) delivered from a biodegradable poly-lactide-co-glycolide (PLGA) device in the vitreous cavity of rabbits' eyes. METHODS: A total of 60 animals (60 eyes) divided into two groups were used. For the in vivo release study, 32 eyes received PLGA implants containing 350 µg of CsA, and 16 eyes received the implants without drug (control). Four animals of CsA group and two of the control group were killed weekly until 8 weeks; the vitreous was removed, and CsA concentration was evaluated. Ophthalmological examination was performed in the animals prior to implant placement and weekly during the study period. Electroretinography (ERG) was performed in other six animals for each group, treated and control, at the beginning and at the end of the study (8 weeks) when they were killed and had their eyes processed for histology. RESULTS: No sign of inflammation was noticed on slit lamp examinations and the IOP maintained stable during the study period in CsA and control groups. CsA concentration in the vitreous (ng/ml) was 257.07 ± 117.23, 271.15 ± 98.96, 296.66 ± 86.25, 256.27 ± 99.22, 304.50 ± 88.18, 326.35 ± 105.24, 491.25 ± 119.90 and 589.93 ± 132.55 after 1, 2, 3, 4, 5, 6, 7 and 8 weeks of implantation, respectively. At the end of the study, 21.67 % of mass loss was found. The retina did not show any histological alteration in either group, but a significant reduction in dark-adapted b-wave amplitude was observed in the CsA group, with no changes in a-wave amplitude. CONCLUSIONS: These data show that the PLGA system is safe, but the selective reduction in ERG b-wave amplitude indicates that the PLGA with 350 µg CsA causes retinal function impairment, specifically on the rod postreceptor pathway, 8 weeks after implantation. These ERG changes were not associated with any histological damage as seen at the light microscopy level.

Sistema de liberação contendo ciclosporina para o tratamento de ceratoconjuntivite seca: estudo preliminar / Cyclosporine-loaded delivery system for the treatment of keratoconjunctivitis sicca: a pilot study

Objetivo: Este trabalho objetivou o desenvolvimento de um sistema mucoadesivo de liberação de ciclosporina A (CsA) para o tratamento de ceratoconjuntivite seca (CCS). Métodos: O sistema mucoadesivo foi preparado na forma de filme utilizando o polímero quitosana e CsA (25%p/v). Foram administrados no saco conjuntival do olho direito de coelhos normais (n=6) e a aferição da produção de lágrimas foi realizada diariamente antes e após a aplicação, de forma bilateral, durante sete dias, por meio do teste lacrimal de Schirmer. Avaliação oftalmológica foi realizada diariamente durante todo o estudo e seguido da análise histológica. Resultados: Os valores médios de produção de lágrimas foram alterados de 9,88 ± 0,37 mm/min para 16,02 ± 0,38 mm/min antes e após a administração do sistema respectivamente, significando um aumento de aproximadamente 60%. Todos os coelhos apresentaram hiperemia da conjuntiva palpebral e lacrimejamento. A hiperemia permaneceu durante 48 h após administração dos sistemas com resolução espontânea e o lacrimejamento foi diagnosticado até o final do experimento. Não foram observados outros sinais de reações indesejáveis. Nenhuma alteração histológica foi observada na mucosa conjuntival bulbar e palpebral à histopatologia. Conclusão: Os sistemas desenvolvidos são aparentemente seguros e eficientes criando expectativa para o tratamento da CCS. Novos estudos são necessários para avaliar a concentração de CsA liberada, assim como aceitabilidade e toxicidade dos sistemas em tratamentos mais prolongados.

Purpose: The present work aimed to present the development of a conjunctival mucosa system for the controlled delivery of cyclosporine A (CsA) in the treatment of keratoconjunctivitis sicca (KCS). Methods: The conjunctival mucosa system was prepared in the form of films containing chitosan as the polymer and CsA as the drug (25%w/v). The films were applied to the conjunctival sac of one eye from normal rabbits (n=6), and the evaluation of lachrymal production was performed daily, before and after application, for seven days. Clinical examination was executed daily on the eyes of each animal during the entire period of study. Histological analyses were carried out at the end of the study. Results: The average amount of lachrymal production changed from 9.88 ± 0.37 mm/min to 16.02 ± 0.38 mm/min, respectively, before and after applying the systems, which indicates an increase of approximately 60%. All rabbits presented hyperemia in the palpebral conjunctiva and tearing. Hyperemia continued for 48h after the application of the systems with spontaneous resolution, and tearing was diagnosed throughout the entire study. No other sign of undesirable reactions could be observed. Moreover, no histological changes could be identified in the bulbar and palpebral conjunctival mucosa. Conclusion: The developed systems proved to be safe and efficient in this pilot study and present a promising future for the treatment of KCS. Other studies are warranted to evaluate the released concentration of CsA as well as the feasibility and toxicity of these systems in a more prolonged treatment.

Montmorillonite clay based polyurethane nanocomposite as substrate for retinal pigment epithelial cell growth.

The subretinal transplantation of retinal pigment epithelial cells (RPE cells) grown on polymeric supports may have interest in retinal diseases affecting RPE cells. In this study, montmorillonite based polyurethane nanocomposite (PU-NC) was investigated as substrate for human RPE cell growth (ARPE-19 cells). The ARPE-19 cells were seeded on the PU-NC, and cell viability, proliferation and differentiation were investigated. The results indicated that ARPE-19 cells attached, proliferated onto the PU-NC, and expressed occludin. The in vivo ocular biocompatibility of the PU-NC was assessed by using the HET-CAM; and through its implantation under the retina. The direct application of the nanocomposite onto the CAM did not compromise the vascular tissue in the CAM surface, suggesting no ocular irritancy of the PU-NC film. The nanocomposite did not elicit any inflammatory response when implanted into the eye of rats. The PU-NC may have potential application as a substrate for RPE cell transplantation.