Submitted on May 2, 2005
Accepted on August 19, 2005
Cytoskeletal Remodeling and Cellular Activation during Deformation of Neutrophils into Narrow Channels
Belinda Yap1 and Roger D. Kamm2*
1 Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA; Department of Mechanical Engineering and Biological Engineering Division, Massachusetts Institute of Technology, Cambridge, MA, USA
2 Department of Mechanical Engineering and Biological Engineering Division, Massachusetts Institute of Technology, Cambridge, MA, USA
* To whom correspondence should be addressed. E-mail: rdkamm{at}mit.edu.
Neutrophils are subjected to mechanical stimulation as they deform into the narrow capillary segments of the pulmonary microcirculation. The present study seeks to understand the changes in the cytoskeletal structure and the extent of biological activation as a result of this process. Neutrophils were passed through narrow polycarbonate filter pores under physiological driving pressures, fixed and stained downstream in order to visualize the F-actin content and distribution. Below a threshold capillary size, the cell remodeled its cytoskeleton through initial F-actin depolymerization, followed by recovery and increase in F-actin content associated with formation of pseudopods. This rapid depolymerization and subsequent recovery of F-actin was consistent with our previous observation of an immediate reduction in moduli with eventual recovery when the cells were subjected to deformation. Results also show that neutrophils must be retained in their elongated shape for an extended period of time for pseudopod formation, suggesting that a combination of low driving pressures and small capillary diameters promotes cellular activation. These observations show that mechanical deformation of neutrophils into narrow pulmonary capillaries have the ability to influence cytoskeletal structure, the degree of cellular activation and migrational tendencies of the cells.
