Juxtaposition of two heterotypic monolayer cell cultures of chick limb buds

In chick limb buds, mesenchymal cells of the progress zone (PZ-cells) at different developmental stages segregate one from the other in mixed cell cultures, suggesting they have different cell affinity. In order to learn the possible roles of such differences in the cells, two heterotypic leg PZ-cell populations (cells from stages 25/26 and 20/21) in vitro were juxtaposed to allow them to form the boundary. A method with double cylindrical columns was used to make adjoining monolayer cell cultures. It was shown that heterotypic juxtaposition produced two chondrogenic patterns along the boundary: aggregates of chondrocytes formed by stage 20/21 PZ-cells and a chondrocyte-free band formed by those at stage 25/26. Juxtaposition of PZ-cells and proximal cells also formed these patterns, while that between cells from anterior and posterior PZ formed indistinct patterns along the boundary. Homotypic PZ-cell juxtaposition did not produce these patterns. The results suggest that different cell affinity has a role in the segmentation of cartilage patterns at a point along the proximodistal axis, as well as a role in retaining cells in one area so as not to be recruited to other condensation areas.