Is the movement of single cells within solid tissue masses induced by trypsinization?

Embryonic chick cells, labeled with tritiated thymidine (³H]TdR), isolated with trypsin and allowed to “recover” or isolated without trypsin were seeded onto the surfaces of solid tissue masses in culture. Autoradiographs revealed extensive migration of single, labeled cells within the tightly packed cell masses. The ability of single cells to infiltrate solid tissue masses in culture does not, therefore, seem to depend upon prior proteolytic treatment.