  Cell migration is crucial to many physiological and pathological processes.
During migration, a cell adapts its morphology, including the overall
morphology and nucleus morphology, in response to various cues in complex
microenvironments, e.g. topotaxis and chemotaxis. Thus, cellular morphology
dynamics can encode migration strategies based on which various migration
mechanisms can be inferred. However, how to decipher cell migration mechanisms
encoded in the morphology dynamics remains a challenging problem. Here we
introduce a novel universal metric, namely cell morphological entropy (CME), by
combining parametric morphological analysis with Shannon entropy. The utility
of CME, which accurately quantifies the complex cellular morphology on multiple
length scales through the deviation from the perfect circular shape, is
demonstrated using a variety of normal and tumorous cell lines in distinct in
vitro microenvironments. Our results reveal that 1) the effects of geometric
constraints on cell nucleus, 2) the emerging interplays of MCF-10A cells
migrating on collagen gel, and 3) the critical transition of tumor spheroid
from proliferation to invasion. The analysis indicates that the CME offers a
physically interpretable and efficient tool to quantify morphology on multiple
length scales in real-time, which provides more insights into cell migration,
and further contributing to the understanding of the diverse behavioral modes
as well as collective cell motility in more complex microenvironment.
