Role of Ca2+ Signaling by 3D Osteocyte Networks in Mechanoadaptive Response of the Bone Multicellular Unit

Summary Osteocytes are the most numerous cell in bone tissue, which act as mechanosensors and coordinate adaptive bone remodeling. Current model systems have been unable to unify the mechanisms by which osteocytes to sense mechanical stimuli, transmit signals across an extensive 3D network, and how these transient signals

drive adaptive bone remodeling by osteoblasts and osteoclasts. In this work, we will use a new bone multicellular unit (BMU) chip that enables longitudinal visualization of mechanosensitive calcium signaling across 3D osteocyte networks, enabling and characterization of the role of this signaling mechanism on the

mechanoadaptive response of osteoblasts and osteoclasts in normal and injured states. Using BMU-chip, this work will test the hypothesis, ‘Discontinuity in 3D osteocyte networks alters mechanically-evoked calcium signal propagation which in turn modulates the spatiotemporal remodeling of effector cells’ using three specific aims.

Aim 1 will define how Pulsed Unidirectional Fluid Flow Stimuli (PUFFS) modulates dynamic changes in calcium signaling across 3D network of osteocytes. Aim 2 will determine how 3D osteocyte networks subjected to PUFFS modulate direct and indirect signaling and osteoblastic bone formation and osteoclastic resorption activities. Aim

3 will identify how targeted disruption of 3D osteocyte networks influence calcium signaling and long-term functional outcomes. Completion of the proposed aims will provide a comprehensive understanding of how mechanically evoked calcium signaling across osteocyte networks modulates functional outcomes within the

BMU in normal and injured conditions. Our team, with complementary expertise in biomedical engineering, bone cell biology, orthopedic surgery and statistical analysis is well suited to execute this project. In the future, BMU- chips could be utilized to probe other mechanotransduction pathways, and accelerate the development and

evaluation of drugs to treat bone disease.