The Role of cGMP in Ocular Growth and the Development of Form-Deprivation Myopia in Guinea Pigs

Development of myopia is associated with remodeling of the sclera, a tissue composed principally of collagen. Cyclic guanosine monophosphate (cGMP) regulates collagen synthesis in several organs; therefore, we investigated the effects of soluble guanylyl cyclase (sGC) stimulation and inhibition on refraction and ocular growth in guinea pigs under normal and form-deprived (FD) conditions.Retinal and scleral cGMP concentrations were measured in normal and monocularly FD guinea pigs at 2 days, 1 week, and 2 weeks of form deprivation and following 2 days recovery. Stimulation of sGC by BAY41-2272 and inhibition by NS-2028 were achieved by daily subconjunctival injection in normal and FD eyes. Refraction and axial parameters were measured at the commencement, middle, and cessation of the experiment. cGMP levels were also determined at the end of the experiment.Retinal and scleral cGMP concentrations increased in FD eyes from 2 days to 2 weeks (P ≤ 0.029). Levels decreased after 2 days of recovery (P ≤ 0.003). Daily injections of BAY41-2272 induced a myopic shift (P ≤ 0.001) and ocular elongation (P ≤ 0.01) in normal animals, but did not alter myopia in FD eyes (P > 0.05). In contrast, daily injections of NS-2028 partially reduced myopic shifts (P ≤ 0.012) and ocular elongation (P ≤ 0.015) induced by form deprivation, but did not affect ocular growth and refraction in normal eyes (P > 0.05). Retinal and scleral cGMP levels were increased by BAY41-2272 in normal eyes and decreased by NS-2028 in FD eyes.Changes in cGMP signaling contribute to myopic development. Thus, cGMP may be a potential therapeutic target for preventing/treating myopia.