Multiple calcium patterns of rat osteoblasts under fluidic shear stress.

The intracellular calcium ([Ca2+ ]i ) response induced by external forces can be diverse and complex. Using primary osteoblasts from Wistar rats, we found multiple patterns of [Ca2+ ]i responses induced by fluidic shear stress (Fss), including homogeneous non-oscillation and heterogeneous oscillations. These multiple-patterned [Ca2+ ]i responses could be influenced by Fss intensity, cell density, and cell differentiation. Our real-time measurements with free calcium, ATP, ATP without calcium, suramin, apyrase, and thapsigargin confirmed homogeneous [Ca2+ ]i patterns and/or heterogeneous [Ca2+ ]i oscillations with respect to the combined degree of external Ca2+ influx, and intracellular Ca2+ release. Our theoretical model supported diverse Fss-induced calcium activities as well. We concluded that a singular factor of Ca2+ influx or release dominated to produce smooth homogeneous patterns, but combined factors produced oscillatory heterogeneous patterns. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2039-2051, 2018.