Dynamics of Plasma and Granule Membrane in Murine Bone Marrow-Derived Mast Cells after Re-stimulation

Mast cells are derived from hematopoietic stem cells and play important roles in allergic responses. Mast cells are long-lived compared with other granular cell types. Since the response of the individual mast cell after FcεRI-induced degranulation is unclear, the aim of this study was to analyze morphological changes in individual mast cells after restimulation. To observe plasma and granule membrane dynamics, AcGFP-actb (β-actin) and DsRed-monomer (DRM)- CD63 fusion constructs were introduced into bone marrow-derived mast cells (BMMCs). Furthermore, AcGFP-CD63 and DRM-Cma1 (mMCP-5) were introduced into BMMCs. Re-stimulation resulted in increased β-hexosaminidase release and cytokine mRNA expression similar to those observed during initial stimulation. Moreover, expression of FcεRI on BMMCs 24 h after initial stimulation was similar to that measured before initial stimulation. Changes in morphology of the plasma membrane and colocalization of granules and plasma membrane were observed after initial stimulation. BMMCs returned to normal 120 min after the initial stimulation. These phenomena were also observed in BMMCs after re-stimulation. BMMC chymase content decreased 20 min after stimulation but returned to near normal 24 h after stimulation. These findings suggest that mast cell functions can be maintained and that these cells can be repeatedly degranulated after FcεRI-mediated stimulation.