Intervertebral Disc-on-a-Chip^MF: A New Model for Mouse Disc Culture via Integrating Mechanical Loading and Dynamic Media Flow

This study aims to develop an ex vivo organ-on-a-chip model, intervertebral Disc-on-a-Chip^MF, to investigate integrated effects of mechanical loading and nutrition on disc health. The system consists of a detachable multilayer microfluidic chip, a Computer-Arduino-based control system, and a mechanical loading unit, which were optimized for accurate axial force measurement and the maintenance of a 21-day ex vivo disc culture. To ensure accuracy of axial force, we optimized the axial mechanical loading regimen, used the Computer-Arduino-based system and low-profile force sensors (LPFS) to control the mechanical loading unit, and modeled the force distribution by using computational simulation. A 21-day ex vivo disc culture was demonstrated using the Disc-on-a-Chip^MF system, with optimized mechanical loading (0.02 MPa at 1Hz, 1.5 hr/day) and flow rate (1 μL/min). The structural integrity, collagen breakdown, catabolic enzyme activities, and disc cell and collagen alignment revealed that the on-chip cultured discs exhibited a preferred disc health similar to that of native discs for up to 21 days, while discs in a static culture showed detrimental degenerative changes. The mouse Disc-on-a-Chip^MF system mimics in vivo disc microenvironment and provides a valuable platform for studying the effects of various factors on disc health and degeneration and testing new therapies.