A quantitative assessment of mesenchymal contribution to epithelial growth rate in mouse embryonic lung developing in vitro

Abstract

The experimental analysis of factors operating in lung morphogenesis has shown that the normal pattern of the bronchial tree is related to a mesenchymal budding-promoting activity, distributed non-uniformly throughout the mesenchymal mantle. No budding is present in the absence of mesenchyme (Dameron, 1961 a, b, 1962). The position of secondary epithelial buds may be changed by substituting “active” for “inactive” mesenchyme (Alescio & Cassini, 1962a, b; see also for a review and pertinent references Sorokin, 1965). Recent in vitro experiments by Colombo Piperno (1966) dealt with the problem of whether the inductive influence of pulmonary mesenchyme could also operate as a stimulus for the expansion and global growth of the epithelial tree. In order to answer this question a procedure was devised to modify, in a definite way, the quantitative ratio of mesenchyme to epithelium of the 11-day pulmonary rudiment of mouse embryos, without disorganizing the natural topographic arrangement of the two tissues.