Fluid shear stress-induced cytosolic calcium signalling and degranulation dynamics in mast cells

A mast cell line (rat basophilic leukaemia cells, RBL-2H3) was used in vitro to study cellular responses to fluid shear stress generated by a rotating rotor in a cell dish. The [Ca²⁺]_c (cytosolic calcium concentration) in mast cells was detected by confocal fluorescence microscopy after Fluo-3/AM (acetoxymethyl ester) staining. Cytosolic calcium fluorescence intensity oscillated, pulsed, or steadily increased after the application of a weak, moderate or strong fluid shear stress respectively. From a mathematical model, we reproduced a change in [Ca²⁺]_c under different levels of fluid shear stress in mast cells. The model calculation confirmed another experimental observation, specifically, that the degranulation rate increases with shear stress and reaches certain steady values. Since mast cells can react clearly and quickly and obviously to mechanical stimuli, calcium signalling and degranulation dynamics could be one of the mechanisms of acupuncture and massage therapies.