Changes in the subepithelial mesenchymal cell process meshwork in developing facial prominences in mouse embryos.
We examined temporal and spatial changes in the subepithelial mesenchymal cell process meshwork (CPM) in normally developing medial (MNP) and lateral nasal prominences (LNP) in mouse embryos by light and scanning electron microscopy. Marked changes were found only in the MNP during the fusion of the MNP and LNP. The CPM density in the prospective fusion area of the MNP gradually increased as the epithelial surfaces approached each other, attained its maximum just before contact, and decreased after contact. The CPM density in the prospective fusion area of the LNP changed only slightly even when the epithelial surfaces approached each other. The increase in CPM density paralleled that in the density of mesenchymal cell bodies. The LNP grew more actively toward the line of fusion than did the MNP during the progressive fusion of the two prominences. A larger number of fusion-associated epithelial morphological changes--the appearance of superficial protruding cells and cell degeneration--occurred in the MNP than in the LNP. These findings suggest that the increased CPM density is closely related to the growth of the facial prominences and the fusion-associated epithelial morphology and that the CPM plays an important role in the epithelial-mesenchymal interaction during the formation of the upper lip and primary palate.
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Igawa
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M
Yasuda
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H
Nakamura
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T
Ohura
D000818:Animals; D004847:Epithelial Cells; D004848:Epithelium / Q000648:ultrastructure; D005145:Face / Q000166:cytology / Q000196:embryology* / Q000648:ultrastructure; D005260:Female; D005865:Gestational Age; D051379:Mice; D008815:Mice, Inbred Strains; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D010159:Palate / Q000196:embryology; D011247:Pregnancy