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Sumit Bhattacharya, Robin R Hodges, Sharmila Masli, Darlene Dartt; Alteration in Cell Structure and Function in Lacrimal Gland of Thrombospondin-1-/- Mouse of Sjögren’s Syndrome. Invest. Ophthalmol. Vis. Sci. 2014;55(13):62.
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© ARVO (1962-2015); The Authors (2016-present)
Dry Eye is a complex disease that targets the ocular surface and tear film causing abnormal tear production. We characterized a novel mouse model thrombospondin-1-/-, (TSP-1-/-) which mimics chronic dry eye in humans with an age-dependent increase in dry eye signs. The purpose of this study is to determine whether cell structure, Ca2+ mobilizing pathways and protein secretion are affected in female TSP-1-/- compared to wild type (WT) mice.
Acinar cell size was determined using NIH Image J. Cytokine levels in lacrimal glands were measured with Q-PCR using primers to interleukins (IL) -1β, IL-6 and IL-17A; IFN- γ; and TNF-α. We performed live cell Ca2+ imaging experiments on isolated mouse lacrimal gland tissue. Intracellular Ca2+ ([Ca2+]i) levels in lacrimal acinar clumps were monitored under a fluorescent microscope upon exposure to various pharmacological compounds. Protein secretion was measured by fluorescence assay which detects the lacrimal gland secretory protein peroxidase.
Morphological changes were observed in TSP-1-/- acini when compared to WT mice. There was a marked decrease in cell size and cell area in 12- and 24-week old female TSP-1-/- mice with respect to WT animals. Moreover, extensive changes in expression of markers of intracellular organelles were found in TSP-1-/- compared to WT acinar cells. Increases in pro-inflammatory cytokine levels were also observed in 24-week old but not 4- or 12-week old TSP-1-/- or any age WT mice. Lymphocytic infiltration detected in H&E stained sections from 4-, 12- and 24-week old female WT versus TSP-1-/- mice was in agreement with pro-inflammatory cytokine expression. Ca2+ imaging studies showed that activation of muscarinic and α1-adrenergic receptor pathways in 12-week old TSP-1-/- acini led to a significant elevation in [Ca2+]i levels when compared to WT acini. In contrast, there was a significant decrease in protein secretion during stimulation by α1-adrenergic, but not cholinergic agonists in 12-week old female TSP-1-/- compared to WT acini.
Morphological changes accompanied by alterations in Ca2+ handling mechanisms lead to disruption in [Ca2+]i levels and lacrimal gland secretion in TSP-1-/- mice. Glandular dysfunction precedes cellular inflammation in this animal model.
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