| Objective: To investigate the efficacy and feasibility of retinoic acid drug delivery system(RA DDS) as a new glaucoma anti-scarring agent by observing its effects on a rabbit model of glaucoma filtration surgery and side effects on eyelid, conjunctiva, cornea, and anterior champer of rabbit eye. To evaluate the mechanism of prevention postoperative scarring of retinoic acid drug delivery system at the protein and messenger RNA levels. Methods: (1)Synthetic of retinoic acid drug delivery system: The material of drug delivery system is a polymer polylactioglycolic acid( PLGA ) of polylactic acid(PLA) and polyglycolic acid(PGA). 1mg retinoic acid was incorporated into a membranous PLGA with a shape of 3×5mm, 0.5mm thickness. The membraneous PLGA will dissolve within 3 months.(2)In a randomized, prospective, masked-observer study, filtering surgery was performed in both eyes of 25 New Zealand white rabbits, weighing 2 to 2.5 kg and aged 12 to 14 weeks. The all left eyes received RA DDS, 15 right eyes only received DDS randomly; the remaining 10 right eyes were null vehicle. (3)Tolerance and safety of retinoic acid drug delivery system in subscleral-flap administration were investigated by assessment of local toxicity, using clinical parameters such as anterior chamber activity, lid edema, chemosis, hemorrhage, and corneal toxicity. (4)Effects on conjunctival scarring and filtration surgery outcome of retinoic acid drug delivery system were evaluated by observations of the bleb area , height , the intraocular pressure (IOP) and anterior chamberdepth . ?The New Zealand White rabbits were killed on days 7, 14, 30, 60 and 90 after surgery . Both eyes were enucleated and histologically analyzed to observe inflammatory cells , fibroblasts and the extracellular matrix components in surgery sites of rabbits eyes. ?Tissue sections were immunohistochemically stained for Transforming Growth Factor-62 (TGF-B2) protein express and proliferating cell nuclear antigen (PCNA) protein express of fibroblast in surgery sites of rabbits eyes . Semi-quantification of TGF-B2 messenger RNA was performed using reverse transcription-polymerase chain reaction (RT-PCR) . By this , the mechanism of prevention postoperative scarring of retinoic acid drug delivery system can be evaluated at the protein and mRNA levels. Results: (D Placements of retinoic acid drug delivery system in surgery sites were well tolerated in surgery eyes of New Zealand White rabbits. No intraocular inflammation was seen in any rabbit at any time in the study, as well as lid edema, chemosis, hemorrhage, and corneal toxicity. ?Retinoic acid drug delivery system was associated with successful filtration surgery, evidenced by bleb morphology. Because any subconjunctival scarring occurring at the filtration site causes flattening and a decrease in surface area of the bleb, important indicators of effective filtration surgery include the presence of a raised and a well-formed bleb. At day 90 after surgery, bleb failure was present in only one rabbit (20%) treated with retinoic acid drug delivery system , but at 3 weeks or so after surgery, all (100%) of the vehicle-treated groups showed failure. Compared with PLGA group and NV group, the IOP remained consistently lower than baseline measurements in the RA+PLGA group (P< 0.001, log rank) analyzed by Kaplan-Meier curve. ? The retinoic acid drug delivery system appeared to be associated with reduced scarring activity at a microscopic level. Total scar formation and architecture in the subconjunctival areas at the filtration site, judged by staining characteristics with Weigert and Van Gieson, was significantly reduced in RA+PLGA treatment compared with control treatments (P<0.001,Chi-square). ?Compared to PLGA treatment and NV treatment, the expression of TGF-J32 secreted by inflammatory cells , fibroblasts and other cells in filtration sites at protein and mRNA levels was significantly reduced in RA+PLGA treatment . The retinoic acid drug delivery system also reduced fibroblast activity, with a significantly reduction in the number and expression of PCNA of fibroblast. Conclusions: The retinoic acid drug delivery system can release retinoic acid sustainly and slowly for a long period of time after surgery, which has strong effects on reduction inflammatory cells activity and fibroblast activity in surgery sites. The retinoic acid drug delivery system was found to improve glaucoma filtration surgery outcome significantly by reduction the deposition of elastic and collagen fibers in the subconjunctival areas at the filtration site. During the whole time in this study, the retinoic acid drug delivery system expressed no toxicity and side-effects. It has potential as a new safe and effective anti-scarring agent for easy use in glaucoma filtration surgery.
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