Mechanical deformation of monocytic THP-1 cells : occurrence of two seqential phases with differential sensitivity to metabolic inhibitors

TL;DR

This study investigates the mechanical deformation of monocytic THP-1 cells, revealing two sequential phases with different sensitivities to metabolic inhibitors, highlighting the role of active metabolism in cell shape changes.

Contribution

It demonstrates that cell deformation involves two phases with distinct metabolic dependencies, providing new insights into the mechanics of immune cell shape changes.

Findings

First phase of deformation is energy-independent and affected by microfilament and microtubule inhibitors.

Second phase requires active metabolism and is abolished by energy production inhibitors.

Active metabolic processes are essential for extensive morphological changes in cells.

Abstract

Blood leukocytes can exhibit extensive morphological changes during their passage through small capillary vessels. The human monocytic THP-1 cell line was used to explore the metabolic dependence of these shape changes. Cells were aspirated into micropipettes for determination of the rate of protrusion formation. They were then released and the kinetics of morphological recovery was studied. Results were consistent with Evans' model (Blood, 64 : 1028, 1984) of a viscous liquid droplet surrounded by a tensile membrane. The estimated values of cytoplasmic viscosity and membrane tension were 162 Pa.s and 0.0142 millinewton/m respectively. The influence of metabolic inhibitors on cell mechanical behaviour was then studied : results strongly suggested that deformation involved two sequential phases. The cell elongation rate measured during the first 30 seconds following the onset of aspiration was unaffected by azide, an inhibitor of energy production, and it was about doubled by cytochalasin D, a microfilament inhibitor, and colchicine, a microtubule inhibitor. However, during the following two minutes, deformation was almost abolished in cells treated with azide and cytochalasin D, whereas the protrusion of control cells exhibited about threefold length increase. It is concluded that, although cells seemed to deform as passive objects, active metabolic processes were required to allow extensive morphological changes triggered by external forces.