Influence of epithelial‐mesenchymal interaction on the viability of facial mesenchyme in vitro

Abstract

Separation and recombination experiments, employing a variety of tissue configurations in organ culture, were performed to determine the extent to which the epithelium of the maxillary process influences the viability of the underlying mesenchyme during organogenesis. The results of these studies indicated that the viability of mesenchyme of the maxillary process of early stage embryos was severely impaired when separated from the overlying epithelium. The influence of epithelium on the viability of mesenchyme was stage dependent; that is, the requirement for the presence of epithelium for the maintenance of the viability of mesenchyme became progressively less pronounced at older developmental stages. The response of mesenchyme to the presence of recombined epithelium resulted in the appearance of a delimited zone of influence extending, within specific boundaries, from the epithelial-mesenchymal interface. Preliminary data from homotypic (maxillary epithelium-maxillary mesenchyme), heterotypic (limb apical ectodermal ridge-maxillary mesenchyme) and heterochronic (stage 28 epithelium-stage 22 mesenchyme) recombination experiments indicated that viability of mesenchyme could be achieved only through direct epithelial-mesenchymal contact which allowed restoration of normal morphological relationships at the interface of the two tissues.

Influence of epithelial‐mesenchymal interaction on the viability of facial mesenchyme II: Synthesis of basement‐membrance components during tissue recombination

“…Light microscopic examination of explants after 24 hours of culture revealed, first, that a developmental compartment, comparable in size and dimensions to that observed in the previous study of Saber et al (1989), was present in the explants from which laminin and type IV collagen had been removed; second, a gradient of cell viability extended from the edge of the developmental compartment to the distal edge of the explant furthest from the epithelial-mesenchymal interface (Fig. 4).…”

“…In this case, however, it was found that the original protocol of Saber et al (1989) basement-membrane components and a second enzymatic digestion was found to be unnecessary and, in fact, undesirable since it resulted in disaggregation of the tissue fragment. As seen in Figures 3e,f, when the protocol of Saber et al was employed for tissue separation and then stained after incubation for l hour with monoclonal antibodies to either laminin or collagen, essentially no signal was found.…”

“…Treatment of maxillary process explants employing the protocol of Saber et al (1989) revealed that basement-membrane components were not entirely removed by the procedures utilized in that study. For example, at stage 22, untreated maxillary process explants stained with monoclonal antibodies to laminin after 1 hour in organ culture revealed a continuous, thick basement-membrane (Fig.…”

“…The results of this study indicate that the protocol employed by Saber et al (1989) did not remove basement-membrane components after enzymatic tissue separation procedures. Fragments of laminin and type IV collagen remained adherent to isolated epithelia prior to recombination with mesenchyme.…”

“…Photograph courtesy of Dr. K.K. Sulik (from Saber et al, 1989). mesenchyme was washed in the HBSS-FBS mixture ( l : l , VN), and then transferred directly to a complex culture media consisting of BGJ-Fitton-Jackson modification (GIBCO, Grand Island, NY) supplemented with 15% fetal bovine serum, 50 Fglml ascorbic acid, and 2% strepipenicillin. After the second enzymatic treatment, the epithelium was again washed in HBSS-FBS mixture, and was then transferred to media.…”