Purchase this article with an account.
J. A. Summers Rada, L. R. Hollaway; RALDH2 Mediates Retinoic Acid Synthesis in Chick Choroids During the Recovery From Induced Myopia. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3672.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Previous studies have demonstrated that scleral proteoglycan synthesis is rapidly (within hours) down-regulated in response to myopic defocus. This down-regulation of scleral proteoglycan synthesis is largely responsible for slowing the rate of vitreous chamber elongation, and together with concomitant choroidal thickening, the reduction of negative refractive error. Retinoic acid, synthesized by the choroid, has been implicated in the local regulation of scleral proteoglycan synthesis in vivo. The aim of the present study was to extend these previous findings by measuring the expression of the three aldehyde dehydrogenases responsible for retinoic acid synthesis in the retina and choroids of chick eyes experiencing myopic defocus.
Myopia was induced in White leghorn chicks by form deprivation for 10 days, followed by up to four days of unrestricted vision (recovery). Expression of RALDH1, RALDH2 and RALDH3 was examined at 0 - 4 days of recovery by real-time PCR. The choroidal distribution of RALDH2 was evaluated by immunohistochemisty and confocal microscopy. A retinoic acid reporter cell line was used to demonstrate retinoic acid synthesis by isolated choroids from control and treated eyes by measuring β-galactosidase expression with ortho-nitrophenyl-ß-galactosidase (ONPG). Comparisons between control and recovering eyes were made using paired t-tests.
The retina expressed RALDH1, RALDH2 and RALDH3 at similar levels in control eyes. Following 12 hrs of recovery, retinal RALDH2 expression was significantly reduced as compared to controls (↓70% p < 0.01). Only RALDH2 and RALDH3 mRNA could be detected in the chick choroid, with RALDH2 as the predominant transcript (>100 fold that of RALDH3). Choroidal RALDH2 mRNA pools were significantly elevated following 12 and 24 hrs of recovery (↑60% and ↑188%, respectively p < 0.01) and returned to control levels by four days of recovery. RALDH2 was localized within the recovering choroid to a narrow cellular region adjacent to the sclera. Retinoic acid synthesis was significantly elevated in isolated choroids following 24 hr of recovery ( ↑5.2 fold, p <0.05).
The results of this study suggest that RALDH2 is the major aldehyde dehydrogenase in the chick choroid and is responsible for increased retinoic acid synthesis in response to myopic defocus.
This PDF is available to Subscribers Only