Abstract
Intercellular bridges are plasma continuities formed at the end of the cytokinesis process that facilitate intercellular mass transport between the two daughter cells. However, it remains largely unknown how the intercellular bridge mediates Ca(2+) communication between postmitotic cells. In this work, we utilize BV-2 microglial cells planted on dumbbell-shaped micropatterned assemblies to resolve spatiotemporal characteristics of Ca(2+) signal transfer over the intercellular bridges. With the use of such micropatterns, considerably longer and more regular intercellular bridges can be obtained than in conventional cell cultures. The initial Ca(2+) signal is evoked by mechanical stimulation of one of the daughter cells. A considerable time delay is observed between the arrivals of passive Ca(2+) diffusion and endogenous Ca(2+) response in the intercellular-bridge-connected cell, indicating two different pathways of the Ca(2+) communication. Extracellular Ca(2+) and the paracrine pathway have practically no effect on the endogenous Ca(2+) response, demonstrated by application of Ca(2+)-free medium, exogenous ATP, and P2Y(13) receptor antagonist. In contrast, the endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin and inositol trisphosphate (IP(3)) receptor blocker 2-aminoethyl diphenylborate significantly inhibit the endogenous Ca(2+) increase, which signifies involvement of IP(3)-sensitive calcium store release. Notably, passive Ca(2+) diffusion into the connected cell can clearly be detected when IP(3)-sensitive calcium store release is abolished by 2-aminoethyl diphenylborate. Those observations prove that both passive Ca(2+) diffusion and IP(3)-mediated endogenous Ca(2+) response contribute to the Ca(2+) increase in intercellular-bridge-connected cells. Moreover, a simulation model agreed well with the experimental observations.