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Alexander Levy, Sarah M Baldivia, Rafael Grytz; Collagen crosslinking using genipin diminishes cyclic softening of tree shrew sclera during lens-induced myopia development. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2178.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the effect of exogenous crosslinking using genipin on the cyclic softening response of the remodeling tree shrew sclera during monocular -5 diopter (D) lens wear.
Cyclic tensile tests were performed on 2-mm wide scleral strips, first at physiological loads (50 cycles, 0-3.3 g, 30 sec/cycle) and subsequently after 10 minutes rest at supra-physiological loads (50 cycles, 0-33.3 g, 60 sec/cycle) conditions. Two scleral strips were obtained from each eye of two juvenile tree shrews exposed to 4 days of monocular -5 D lens wear to induce axial elongation and myopia. The scleral strips of the control eye were mechanically tested immediately after enucleation or after 24 hours incubation at 37°C in PBS. The scleral strips of the lens treated eye were tested after 24 hours incubation in PBS or PBS supplemented with genipin at a low cytotoxicity concentration (1mM). Cyclic softening was defined as the incremental strain increase from one to the next cycle. This value was averaged over both animals and cycles 5 to 50. Cycles that led to tissue failure were excluded.
At both loading conditions (physiological / supra-physiological loads), the average incremental strain increase (% per cycle) was nearly identical in the fresh (0.03 /0.2) and PBS incubated tissue of the control eye (0.03/0.26). The cyclic softening was approximately four times higher in the sclera of the myopic eye (0.14/0.81) and two orders of magnitude lower after genipin crosslinking (0.001/0.004).
Results indicate that cyclic tensile loading leads to continued softening of the juvenile tree shrew sclera. The softening rate increases during lens-induced myopia and is diminished after genipin crosslinking. This finding suggests that axial elongation in myopia may be due to a remodeling mechanism that increases the cyclic softening response of the sclera, which can be inhibited by scleral crosslinking using genipin.
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