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BT Hassell, DA Samuelson, PA Lewis, KN Gelatt; Smooth Muscle Actin Localization in the Trabecular Meshwork of Dogs with Primary and Secondary Glaucoma . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1038.
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Purpose:It has been recognized that the cells of the trabecular meshwork (TM) contain smooth muscle actin (smA) and possess contractile abilities, which can alter aqueous outflow. We have also shown that the number of TM cells in canine eyes with primary open-angle glaucom (POAG) are less than that of age-matched normal eyes. It is hypothesized that the subpopulation of TM cells with smA will decline more rapidly in glaucomatous eyes than that which occurs normally with age, and may be an important component during the early stages of POAG. Accordingly, we have examined the presence of smA in the TM of canine eyes with primary and secondary forms of glaucoma and compared them to age-matched controls. Methods:Sagital sections of the whole globes from 25 dogs, 17 glaucomatous (5 with primary glaucoma and 12 with secondary glaucoma) and 8 normal) were cut. The sections were incubated with primary antibody (mouse anti-human sm actin) overnight at 50°C and treated sequentially with secondary antibody ([rabbit anti-mouse immunoglobin]), peroxidase labeled streptavidin, and substrate chromagen solution (AEC) and appropriate washes. Sections of canine cardiac tissue were used as positive and negative controls for each run. Results:Labeling was observed in the meshwork of 10 out of the 17 glaucomatous individuals, distributed across all of the age groups represented including eyes with primary and secondary glaucoma. Smooth muscle actin labeling was observed in the TM of 7 out of 14 eyes with closed angle glaucoma. Positive immunoreaction was observed in 3 out of 3 eyes with open angles. Labeling of smA was observed in the anterior part of the TM in 4 of the 17 glaucomatous eyes, all of which had secondary glaucoma. All non-glaucomatous eyes showed greater labeling than the glaucomatous eyes of the same age. The localization pattern of smA within the TM was most affected among those with primary glaucoma. Conclusion:It was concluded that while there is an age-related loss of smA within the TM of canine eyes, it is more severe in glaucomatous eyes, especially those with the primary form.
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