| Engineered fluidic platforms recapitulate cellular environments, and enable readily controlled and observed cell interrogation and response. Functional microfluidic devices mimic native tissue geometry, topography, and/or chemical signaling. Measuring cell response to mechanical and chemical stimuli in vitro is a critical step toward understanding in vivo cell behaviors. Utilizing systems that precisely control these stimuli and mimic the pericellular space in which cells exist provides insight into cell-cell communication in health and disease. Cells that possess and communicate via dendrites present a unique set of environmental constraints that can be evaluated by specialized fluidic systems. These include dendritic cells of the immune system, neurons and glia of the nervous system, and osteocytes in bone. For these cell models, confined pericellular space and cell interconnectivity are fundamental aspects of device design.;In this work, we used fluidic systems to investigate cell-cell communication between dendrite-possessing cells. Preliminary studies examined how cell contact impacts the chemotaxis of neuronal- and glial-derived cells. Initial results demonstrated a need for a new fluidic platform to enable micro and nanoscale examination of cell-cell communication. The Macro-micro-nano (Mmicron) platform was developed to model and control small molecule diffusion between discrete cell populations. This system was particularly suited for osteocytes, as the micro-to-nanoscale features recapitulate the mineral-encased osteocyte network, known as the lacunar-canalicular system (LCS).;The Mmicron system is a novel, more physiologically relevant tool to examine the communication of osteocytes and other dendrite-possessing cells. Osteocytes within the Mmicron approximate the dendritic morphology of native osteocytes within the LCS, forming elongated, nanoscale processes, which communicate via functional gap junctions. Additionally, osteocytes exposed to heat stress in one compartment of the Mmicron were shown to predictably undergo apoptosis, release ATP through Pannexin 1 membrane channels, and induce RANKL upregulation in bystander osteocytes. RANKL upregulation was dependent on ATP binding to P2X7 receptors within the opposing compartment of the Mmicron. By parsing the components of osteocyte apoptosis as a chemical trigger for bone remodeling, the Mmicron system will further elucidate bone function and facilitate development of treatments with increased pharmacologic specificity for bone deficiency diseases, such as osteoporosis. |
