Development of the biomechanical disc culture system for intervertebral disc mechanobiology.

摘要

Intervertebral disc (IVD) degeneration is considered to be one of sources of low back pain and current treatment strategy is based on treating this symptom by surgical means despite poor understanding about the relationship between pain and degeneration of the disc. Apart from genetic disposition, abnormal mechanical stress is considered as a contributing factor to the degeneration of this load bearing joint and several in vitro and in vivo studies reported that non-physiological stresses can cause or accelerate biological symptoms leading to disc degeneration. However, conditions employed in these studies did not represent the physiology in its entirety.;Methods. It was attempted to develop: (1) a culture protocol to keep IVD motion segments viable for prolonged periods in culture, (2) a biomechanical disc culture system (BDCS) for a comprehensive study on mechanobiology of IVDs, and (3) study IVD response to chronic application of (a) axial compressive stress (0.2MPa) and (b) combined load with axial compressive stress (0.2 MPa) along with non physiologic shear load (1.5 N∼0.5 times Body weight) for a period of 7 days.;Results. (1) Culture protocol was evaluated successfully with >95% cell viability for up to 2 weeks in culture; (2) working prototype of BDCS was successfully developed and validated; (3) compressive loaded IVDs and shear loaded IVDs showed comparable cell viability to controls. There was no significant difference in responses between the loaded groups histologically and also mechanically. All loaded IVDs had similar morphology with mechanical properties such as static modulus, dynamic modulus, creep deformation and relaxation did not show any significant difference.;Conclusion. Culture of IVD motion segment is possible; further optimization of culture protocol is necessary to completely validate the system. The BDCS can be used to study mechanobiology of IVDs and other load bearing tissues also. The IVDs responded to mechanical loading; higher magnitude of shear may be required to induce significant change indicating IVD degeneration. Results are encouraging and future studies are warranted for optimization for a successful study design for IVD mechanobiology research.