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Patrick Carney, Breanna Ford, Daniel Nomura, Christine Frances Wildsoet; Sex specific endocrine differences in sclera of myopically progressing chicks. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5865. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Human myopia is more common and on average presents with a more severe clinical phenotype in females (F) than in males (M). We tested the hypothesis that differences in the levels of one or more scleral steroid hormones (SH) and/or receptors (SHR) may underlie these differences.
Seven day-old White-Leghorn chicks (24 M, 24 F) were monocularly form deprived (FD) to induce myopia. Refractive error (RE) and axial length (AL) data were collected at 20 days of age (19 M, 19 F); on the next day, chicks were sacrificed, sexed, and 6 mm diameter fibrous scleral (FSc) samples collected and homogenized. FSc samples from myopic and fellow eyes of FD chicks (5M & 5F) were analyzed via tandem mass spectroscopy to quantify SH levels. SHR gene expression in FSc from both eyes of FD chicks (19 M & 19 F) was assessed by qPCR.
Results: The deprived eyes of F chicks were more myopic than their M counterparts (-30.77 Diopters (D, F) & -22.18 D (M), p=0.001), although there was no significant difference in their AL (11.12 mm (F) & 11.34 mm (M), p = 0.354). Neither REs nor ALs of fellow eyes showed M vs. F differences (RE: F = 1.75 (F) & 1.67 D (M); AL: 10.11 mm (F), 10.16 mm (M)), were significantly different (p>0.05). In relation to the FSc, there was a small, albeit not significant increase in corticosterone levels in FD versus fellow eyes of M chicks. Additionally, a range of other SH and SHR transcripts were found in FSc (Table 1). For the glucocorticoid receptor (GR), gene expression was elevated in FD eyes relative to fellows in F chicks (1.85X, p = 0.001) and decreased in M chicks (0.83X, p = 0.001). FD eyes of F chicks also showed relative over-expression of the estrogen receptor (ER) ß (1.35X, p = 0.046), and reduced expression of ERα (0.83X, p = 0.001) and androgen receptor (AR)(0.72x, p =0.001).
Our results revealed scleral expression of multiple SH and SHR transcripts, with significant sex specific differences in some. This is consistent with roles of sex differentiable SH and/or SHRs in ocular growth modulation and their contribution to reported differences in susceptibility to myopia in humans.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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