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Henrik Barth, Sven W. Crafoord, Cyrille Vinchon, Timothy M. O’Shea, Christopher D. Pritchard, Fredrik K. Ghosh; A New Model for In Vitro Testing of Vitreous Substitute Candidates. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3765.
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© ARVO (1962-2015); The Authors (2016-present)
To describe a new model for in vitro assessment of novel vitreous substitute candidates.
The biological impact of three vitreous substitute candidates were explored in a retinal explant culture model; a polyalkyl-imide hydrogel (Bio-Alcamid®), a two component hydrogel of 20 wt.% poly(ethylene glycol) in phosphate buffered saline (PEG) and a cross-linked sodium hyaluronic acid hydrogel (Healaflow®). The gels where applied to explanted adult rat retinas and then kept in culture for 5 days. Gel exposed explants were compared with explants incubated under standard conditions (medium only). Cryosections of the specimens were stained with hematoxylin and eosin, immunohistochemical markers (GFAP, Rhodopsin), and TUNEL.
Explants kept under standard conditions as well as PEG exposed explants displayed disruption of retinal layers with moderate pyknosis of first, second and third order neurons. They also displayed moderate fragmentation of DNA (TUNEL). Bio-Alcamid® exposed explants displayed severe thinning and disruption of retinal layers with massive cell-death. Healaflow® treated explants displayed normal retinal lamination with significantly better preservation of retinal neurons compared with control specimens, and almost no DNA-fragmentation. Retinas exposed to Healaflow® and retinas kept under standard condition showed variable labeling of GFAP with generally low expression and some areas of upregulation, PEG-exposed retinas showed increased GFAP labeling, and Bio-Alcamid® exposed retinas showed sparse labeling of GFAP.
Research into novel vitreous substitutes has important implications for both medical and surgical vitreoretinal disease. The in vitro model presented here provides a method of biocompatibility testing prior to more costly and cumbersome in vivo experiments. The explant culture system under standard conditions imposes reactions within the retina that can be used for comparison using vitreous substitute candidates. These reactions include disruption of layers, cell-death and GFAP upregulation. PEG gel imposes reactions similar to the control retinas whereas Healaflow® shows protection from culture induced trauma, indicating a favorable biocompatibility. Bio-Alcamid® adversely affects the retina strongly, which is consistent with the results of prior in vivo trials.
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