Microfluidics Chamber System for Bone Cell Mechanotransduction Study and Bone Tissue Engineering Application

INTRODUCTION: One of the great challenges for both basic science study and tissue engineering is constructing a 3-D structure that closely mimics the in vivo microenvironments of cells . In bone tissue, osteocytes form the most abundant cell type, and are suggested as mechanosensor cells, which translate mechanical stimuli into downstream biochemical signals that further regulate bone remodeling . Recent studies indicated that one of the key factors for osteocyte mechanotransduction is the unique lacunar-canalicular structure, in which the osteocytic process is located in the center of canaliculi .However, conventional in vitro loading devices lack the critical geometric and physical characteristics of the extracellular environment that osteocytes reside in. Therefore, a more realistic in vitro environment is needed so that osteocyte mechanotransduction can be better understood. Furthermore, the creation of a physiologically relevant microenvironment will be critical in developing an optimal artificial bone tissue in which the effects of mechanical loading on bone cells can be well controlled and the artificial bone tissue can better remodel its structure to meet its specific mechanical environment. In this study, we designed an in vitro microfluidics chamber system (MCS) to mimic the in vivo lacunar-canaliculi network in bone. We successfully printed our design on both polydimethyl siloxane (PDMS) and poly lactic acid (PLA) substrate, a biocompatible material that has been certificated by the Food and Drug Administration and widely used in both industry and medical field. Cell culture and mechanical testing were performed on PDMS and PLA substrate, respectively. This unique microfluidics chamber system will allow us to better study mechanotransduction in osteocytes and to construct an optimal artificial bone tissue replacement. METHODS: MCS was designed (Fig. 1) using AutoCAD software based on previous studies on the in vivo lacunar-canalicular structure , The micro-channels representing the canaliculi were 2 μm in width, and the micro-chambers representing the lacuna were 20, 30, 40 μm in diameter.