Cell Proliferation and Cell Differentiation in Tissue Cultures of Adult Muco‐ciliary Epithelia*

Explants and monolayers from a variety of muco-ciliary epithelia were cultivated in vitro and the kinetics of their proliferation and differentiation described. New epithelial lining and epithelial-like monolayer sheets of cells formed, in which the migration cells were all originally undifferentiated cycling stem cells. They divided and differentiated in ML growth into cell types characteristic of the tissue source; however, the control mechanisms which regulate cell division and cell differentiation in the tissues were lost outside the tissue framework. Cell division and cyto-differentiation in ML growths both in ciliated and in mucus-producing cells, were not always mutually exclusive.