Abstract
Purpose: :
This study examined the gene expression of BMP2 and BMP4 in chick retinal pigment epithelium (RPE) with imposed optical defocus as part of a larger investigation of the role of RPE in eye growth regulation.
Methods: :
White-Leghorn chicks wore monocular -10 D or +10 D lenses from 19 days of age for 2 or 48 hours. At the end of the lens treatment periods, chicks were sacrificed, eyes enucleated, RPE isolated and RNA extracted. RNA was subjected to cDNA synthesis, and real-time PCR amplification. Primers for chick BMP2, BMP4, and GAPDH (house-keeping gene) were designed using Primer Express 3.0 and gene information in the NCBI database. Ten-fold serial dilutions of cDNA were used for generating standard curves for each pair of primers. Paired Student’s t-test was used to compare lens-treated eyes with their fellow eyes, which served as controls.
Results: :
Expression of both BMP2 and BMP4 were down-regulated after 2 and 48 h treatment with the -10 D lenses. Expression of BMP2 was down-regulated by 12.3 and 3.9 fold, after 2 and 48 h treatment respectively (p < 0.01, n = 8; p < 0.001, n = 10). Similarly, expression of BMP4 was down-regulated by 4.1 and 1.8 fold after 2 and 48 hours treatment respectively (p < 0.001, n = 8; p < 0.01, n = 10). The opposite trends were observed with the +10 D lens treatment and although the results for the 2 h treatment period did no reach statistical significance, changes in expression were in the same direction for both genes and all five treated chicks. Mean changes in expressions after 2 h were 6.0 and 2.5 fold, for BMP2 and BMP4 respectively (p = 0.121, n = 5; p = 0.086, n = 5). The expression of BMP2 was also elevated at 48 h (2.3 fold, p < 0.05, n = 5).
Conclusions: :
Expression of BMP2 and BMP4 in chick RPE is sensitive to imposed defocus. The bidirectional, defocus-sign dependence of these changes is consistent with roles for these two growth factors in defocus-induced modulation (initiating/inhibiting) of eye growth, either as components of the signal pathway or direct growth modulators.
Keywords: myopia • retinal pigment epithelium • gene/expression