Branching Morphogenesis of Mouse Embryonic Submandibular Epithelia Cultured under Three Different Conditions. (mouse submandibular gland/epithelial branching/morphogenesis/collagenase/heparitinase/heparin/Matrigel)

Open Access
Publisher Website
Google Scholar
Abstract
To investigate how the mesenchyme interacts with the epithelium, we employed three different culture systems: System A, in which intact submandibular gland rudiments at the mid 13‐day stage were cultured on Millipore filters; System B, in which the 13‐day epithelium and mesenchyme were separated once with dispase, recombined again, and cultured on the filter; System C, in which the separated 13‐day epithelium was clotted with Matrigel and cultured with the mesenchyme across the filter or in the presence of EGF instead of the mesenchyme. In Systems A and B, 13‐day epithelia expanded and produced similar lobules with narrow clefts and stalk. When the 13‐day epithelium was cultured in System C under the influence of the mesenchyme, it formed rather oval lobules with stalk that were superficially similar to those in System A, but narrow clefts, as seen in the intact early 13‐day gland, were rarely found in System C. Furthermore, no long stalk formation was observed when EGF was introduced in place of the mesenchyme. A bacterial collagenase from Clostridium histolyticum gave a considerable inhibition of branching of the 13‐day epithelium in Systems A and B, but no significant inhibition was observed in System C when the mesenchyme or EGF was employed as the source of diffusible factor(s). In contrast, although the 13‐day epithelium was significantly resistant to the action of heparitinase I from Flavobacterium heparinum in Systems A and B, the enzyme almost completely inhibited the expansion and branching of the epithelium in System C. Judging from these observations, we conclude that the mechanisms of lobular formation in Systems A and B are not the same as those in System C, where the epithelium is clotted with basement membrane matrix components during tissue culture.