Purchase this article with an account.
David S. Hammond, Christine F. Wildsoet; Lens Defocus-induced Changes In The Ocular Somatostatin Signaling Pathway of Chicks. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3429.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Due to its location between the retina and the choroid, it is likely that the RPE relays retinal growth modulatory signals to the choroid and sclera. As a potential signal relay, we targeted the somatostatin (SST) pathway, SST being already linked to both retinal signaling and RPE function. We examined the effect of optical defocus, a known modulator of ocular growth, on gene expression of somatostatin (SST) and its receptor SST2R in the retina and RPE respectively.
Chicks were either left untreated (controls) or treated with monocular +10 or -10 D lenses for 2 or 48 h or 18 days. Ocular biometry was performed at all time points by high frequency A-scan ultrasonography. SST and SSTR2 gene expression levels were quantified using real-time PCR on total RNA extracted from the retina and RPE respectively. Quantification of mRNA targets was performed using the relative expression software tool, normalizing transcript levels to untreated control birds.
As expected, choroidal thickness decreased and increased in -10 and +10 D lens treated eyes respectively (p<0.05, 2 & 48 h, & 18 d), while their untreated fellows were unaffected, showing similar growth changes to the eyes of control birds. With +10 D lenses, significant increases in retinal SST transcript levels were found after 48 h of lens wear (↑1.7, p=0.008, n=4) and likewise, SSTR2 transcript levels in the RPE were increased after 48 h (↑3.2, p=0.001, n=8). With -10 D lenses, significant increases in retinal SST expression were also found, but only after a much longer period (18 days) lens wear (↑1.4, p=0.029, n=4). Interestingly, while RPE from eyes wearing -10 D lenses for 48 h showed no change in SSTR2 expression (0.855, p=0.572,n=8), RPE from their fellow eyes showed increased SSTR2 expression (↑2.5, p=0.005, n=8).
Our observation of altered SSTR2 expression in the RPE of eyes undergoing altered eye growth supports a role for this growth factor in eye growth regulation and the RPE’s involvement as the conduit for relaying and perhaps integrating retinal signals passing to the choroid and sclera. Our data also add to accumulating evidence suggesting that the two eyes of the chicks are independently regulated with respect to their growth, although the pathways mediating this coupling remain to be elucidated.
This PDF is available to Subscribers Only