Quantification of human neutrophil motility in three-dimensional collagen gels. Effect of collagen concentration

Leukocytes must migrate through tissues to fulfill their role in the immune response, but direct methods for observing and quantifying cell motility have mostly been limited to migration on two-dimensional surfaces. We have now developed methods for examining neutrophil movement in a three-dimensional gel containing 0.1 to 0.7 mg/ml rat tail tendon collagen. Neutrophil-populated collagen gels were formed within flat glass capillary tubes, permitting direct observation with light microscopy. By following the tracks of individual cells over a 13.5-min observation period and comparing them to a stochastic model of cell movement, we quantified cell speed within a given gel by estimating a random motility coefficient (mu) and persistence time (P). The random motility coefficient changed significantly with collagen concentration in the gel, varying from 1.6 to 13.3 x 10(-9) cm2/s, with the maximum occurring at a collagen gel concentration of 0.3 mg/ml. The methods described may be useful for studying tissue dynamics and for evaluating the mechanism of cell movement in three-dimensional gels of extracellular matrix (ECM) molecules.