Morphological changes of myoepithelial cells of mouse lacrimal glands during postnatal development

To reveal the correlation between myoepithelial cell configuration and size/shape of glandular endpieces (acini), we observed postnatal developmental changes of myoepithelial cells in the lacrimal glands of mice. Glandular and myoepithelial cells were examined in paraffin sections and in isolated acini. In newborns, rudiments of acini showed no clear lumina and glandular cells had few secretory granules. There were no myoepithelial cells with actin. At 3 days after birth, some rudiments showed lumina; however, secretory granules were not salient. Round cells in the periphery of the acini showed immunoreactivity for actin. In 1-week-old mice, glandular cells were polarized: luminal cytoplasm contained some secretory granules, and nuclei were located basally. Most myoepithelial cells were flattened and sometimes projected thin processes in various directions. At 2 weeks, the glandular cells increased their size and contained numerous secretory granules, and the myoepithelial cells were almost stellate. In 4-8 week-old mice, acini increased their size, and myoepithelial cells were very thin and processes were prolonged in length and increased in number. During postnatal development, their distribution of myoepithelial cells was more scarce, while the size of acini increased. This reciprocal relation of myoepithelial cell distribution and acinar size may indicate that the changes of myoepithelial cell configurations depend on the change of acinus size.