Aquaporin-1 upregulation is associated with scleral remodeling during myopia development in mice

To determine the functional importance of aquaporin-1 (Aqp1) in scleral remodeling during myopia development using in vivo and in vitro models.

Forty-two C57BL/6J mice were randomly assigned into experimental (n=28) and normal control (NC) groups (n=14). In the experimental group, the right eyes underwent form deprivation (deprived eye, DE), whereas the left eyes served as self-controls (fellow eye, FE). Mice in the normal control (NC) group received no treatment in either eye. Refraction was measured before and after myopia induction, and axial length was measured at the end of the experiment. The expression levels of Aqp1, hypoxia-inducible factor-1 alpha (Hif-1α), matrix metallopeptidase 9 (Mmp9), and collagen type I alpha1 (Col1α1) in sclera were determined by immunofluorescence staining, qRT-PCR, and/or western blotting. Scleral morphology was evaluated using hematoxylin and eosin staining.

After two weeks of form-deprivation, DE eyes exhibited a significant myopic shift (1.66±0.09 D) compared with FE eyes (4.92±0.06 D) and NC eyes (left: 4.78±0.11 D; right: 4.91±0.10 D). Scleral thinning was found in DE eyes. Expression levels of Aqp1, HIF-1α, and Mmp9 were significantly upregulated, whereas Col1α1 expression level was significantly downregulated in DE eyes compared to FE and NC eyes. In vitro, hypoxic exposure significantly increased Aqp1 expression level in human scleral fibroblasts (HSFs). Aqp1 overexpression induced a concomitant upregulation of Mmp9. Conversely, treatment with 200 mM acetazolamide under hypoxic conditions inhibited the expression levels of both Aqp1 and Mmp9.

The findings indicated that Aqp1 upregulation was associated with scleral remodeling during myopia development and Aqp1 could contribute to this process, at least in part, through regulation of Mmp9 expression level.