Changes in the number and distribution of myoepithelial cells in the rat parotid gland during postnatal development |
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Authors: | Tsujimura Toshiya Ikeda Rie Aiyama Shigeo |
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Institution: | (1) Department of Histology, School of Life Dentistry at Tokyo, The Nippon Dental University, 1-9-20 Fujimi, Chiyoda-ku, Tokyo 102-8159, Japan |
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Abstract: | The mature rat parotid gland shows hardly any cell bodies of myoepithelial cells around the acini, only a few cell processes
being visible. However, in the early postnatal period, the rat parotid gland shows many myoepithelial cell bodies around the
acini, including the intercalated ducts. In order to clarify the reason for the disappearance of myoepithelial cells from
the area around the acinus during postnatal development, changes in the number and distribution of myoepithelial cells in
the rat parotid gland were examined histochemically and chronologically, with particular reference to cell proliferation and
cell death. From day 7 to day 14, many myoepithelial cells showing a positive reaction with anti-actin antiserum were found
around the acini and intercalated ducts, but thereafter the number of such cells decreased gradually, particularly around
the acini, and had almost disappeared after day 35. BrdU/PCNA-positive myoepithelial cells surrounding the acini were easily
detected on day 14, but disappeared by day 21, whereas BrdU/PCNA-positive acinar cells remained numerous even after day 21.
TUNEL/ISEL staining showed no positive myoepithelial cells throughout the observation period. Transmission electron microscopy
also demonstrated no myoepithelial cells with chromatin condensation characteristic of apoptosis through the observation period.
These findings suggest that the main reason for the disappearance of myoepithelial cells from the area around the acinus during
postnatal development is the large difference between the number of myoepithelial cells and that of acinar cells, because
the acinar cells retain their proliferative activity even after myoepithelial cells have become quiescent. |
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Keywords: | Myoepithelial cell Parotid gland Growth and development Change in distribution Rats |
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