OBJECTIVETo observe the expressions of the collagen , matrix metalloproteases-2 (MMP-2), and tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) in the posterior sclera of newborn guinea pigs with negative lens-defocused myopia.

METHODSNewborn guinea pigs were monocularly defocused by -10D lens. After 4 weeks of defocus, the eyes were removed to provide posterior scleral samples for detection. Expression of collagen was detected by immunohistochemistry on frozen sections of guinea pig sclera, and the protein levels of MMP-2 and TIMP-2 were evaluated by Western blot.

RESULTSImmunohistochemical analysis indicated that the expressions of collagen and TIMP-2 were significantly lower and the expression of MMP-2 was significantly higher in the posterior sclera in the defocused eyes than in the contralateral eyes (all P < 0.01). However, all these indicators were not significantly different between the contralateral eyes and normal control eyes (all P > 0.05). In the defocused animals, the refraction of defocused eyes was positively correlated with the expression levels of collagen (r = 0.79, P < 0.01) and TIMP-2 (r = 0.74, P < 0.05) and was negatively correlated with the expression level of MMP-2 (r = -0.78, P < 0.01) in posterior sclera.

CONCLUSIONAlteration of extracellular matrix in the posterior sclera, probably participated by MMP-2, may exist during the development of defocus-induced myopia.