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A. Tochigi, R. D. Walkup, T. Nakajima, T. R. Shearer, M. Azuma; Secretion of Lacritin From Cultured Monkey Lacrimal Acinar Cells. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5286. doi: https://doi.org/.
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Lacritin is one of the major proteins in tears. So far, lacritin has been detected only in primates, where it is suspected to be an important factor in maintaining the ocular surface. Lacritin is thought to be synthesized in the lacrimal gland and then secreted into tear fluid. However, the mechanism for secretion of lacritin is not clear because no culture system for primate acinar cells has been established. Thus, the purposes of the present study were to 1) establish a culture procedure for acinar cells from monkey lacrimal gland and 2) determine secretion of lacritin in cultured acinar cells.
Acinar cells were isolated from monkey lacrimal gland and cultured. Expression of mRNA and protein for lacritin were detected by quantitative RT-PCR and immunoblotting, and intracellular calcium was measured by Fluo-4. Acinar cells were identified by immunohistochemistry as cells with granules containing tear proteins. Secretion of lacritin was induced with carbachol.
Acinar cells started proliferating at 3 days, and cell numbers gradually increased thereafter. The known tear protein lipocalin and patches of lacritin were observed in the cytosol of cultured acinar cells. Since lacritin protein gradually decreased with culture time, secretion of lacritin was measured on day 1 of culture. Carbachol stimulated lacritin secretion as well as other tear proteins. Addition of carbachol also increased cellular calcium in a dose-dependent manner.
A protocol for culture of acinar cells from monkey lacrimal gland was successfully established. Secretion of tear proteins by carbachol confirmed the validity of the culture protocol. Our culture system is useful for studies of proteins such as lacritin, which are expressed only in primates.Dr. Shearer receives a research contract and consulting fees from, and Dr. Azuma is an employee of, Senju Pharmaceutical Co. Ltd.
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