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Andrew David Pucker, Ashely R Carpenter, Hugh J Morris, Andrew J Fischer, Kirk M McHugh, Donald O Mutti; Ciliary Muscle Cell Changes During Guinea Pig Emmetropization. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2180.
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© ARVO (1962-2015); The Authors (2016-present)
To establish normal morphological parameters and to characterize ciliary muscle (CM) cell changes with age during guinea pig emmetropization.
Three pigmented guinea pig eyes were collected at three different ages (n = 9 eyes). Mean refractive error was determined with retinoscopy by two trained examiners. Eyes were then enucleated, hemisected, and fixed with paraformaldehyde. Temporal eye segments were then embedded in OCT compound and 30 µm serial sections were collected; the two most temporal slides of each eye were then labeled with anti-α-smooth muscle actin antibodies (smooth muscle) and Draq5 nuclear stain. Sections were then visualized with a fluorescent microscope (Leica Microsystems) and analyzed with Stereo Investigator (MBF Bioscience) to determine the mean CM cross-sectional area, nuclei number, and cell cross-sectional area.
Guinea pigs displayed emmetropization as refractive error decreased from +9.08 ± 2.75 D at 1-day-old to +2.91 ± 0.88 D at 90-days-old. The mean CM length and CM cross-sectional area both significantly increased with age, from 0.42 ± 0.035 mm to 0.90 ± 0.095 mm (p = 0.003) and from 0.037 ± 0.005 mm2 to 0.057 ± 0.015 mm2 (p = 0.011), respectively. The mean cross-sectional area covered by each CM cell did not change (p = 0.82), which is consistent with the marginal increase in the mean CM cell number from 72.0 ± 7.4 cells to 105.5 ± 19.2 cells per section (p = 0.059; all by Jonckheere-Terpstra test).
Guinea pig CM undergoes morphologic changes during development in the first 90 days of life characterized by significant increases in cross-sectional area and length while the mean area occupied by each cell does not significantly change. These data suggest that the CM grows via cell proliferation rather than through hypertrophy. These normative data will be useful when contrasted with potential CM changes during myopia induction experiments.
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