Purpose:
To compare differential gene expression signatures produced in tree shrew sclera by three different visual conditions that all produce ocular elongation and myopia.
Methods:
Three groups of tree shrews (n=7 per group) were used: 4 days of monocular -5 D lens wear (ML), 4 days of monocular translucent diffuser wear (FD), and continuous darkness for 11 days (DK). Treatment ended at the same time point (28 days of visual experience). The untreated contralateral eyes in ML and FD groups served as controls. Real-time PCR was used to measure the relative changes in mRNA levels for 22 candidate genes: TGFB1, TGFB2, TGFBR3, VDR, CTGF, THBS1, SPARC, TNC, SPP1, TIMP1, MMP2, MMP14, ADAMTS5, TGFBI, COL1A1, SDC2, ANXA1, ANXA2, FBLN1, CAPN2, CAPNS1, and ACAN, in comparison to a reference gene (POLR2A).
Results:
The treated eyes in all groups responded with a myopic shift. Based on previous studies, the myopia in all groups was actively progressing. In the ML group, the mRNA expression level of 17 of 22 candidate genes showed significant differential changes (treated vs. control eyes, paired t-test, p<0.05). In the MD group, 18 of 22 genes showed significant differential changes. Comparing DK group (average of R & L eyes) to the ML group control eyes, 3 genes showed differential expression (unpaired t-test). The direction and magnitude of the differential gene expression patterns in the ML and FD groups are very similar (A), r2 = 0.969, as is the differential gene expression pattern of the DK group compared with the control eye of the ML group (B), r2 = 0.766.
Conclusions:
The very similar gene expression signatures produced in the sclera by the three different myopiagenic visual conditions suggest that the mechanisms that produce scleral remodeling and axial elongation are similar, regardless of the specific visual stimuli that produce the scleral changes.