EFFECT OF STRETCHING STIMULATION DURING CULTURE ON MENISCAL ENTHESIS CONSTRUCTS

Abstract

Tissue engineered (TE) menisci have been seen as a very promising treatment for meniscus injury repair in human knee joints. Although much effort has been focused on the TE meniscus body, less attention has been paid to the connective integration between the meniscus and the underlying bone, which plays a significant role in the mechanical stability and the success rate of meniscal repair. This specific connective tissue in the knee joint is called the meniscal enthesis. In this research, a simplified meniscal enthesis construct model is used as a platform for experiments and testing to mimic the complex native enthesis structure. The model is composed of a collagen gel with fibrochondrocytes (meniscus region), decellularized bone plugs (bone region), and an interface region. Stretching stimulation along the axial direction has been applied onto clamped meniscal enthesis constructs during culture as an attempt to improve the mechanical performance and collagen fiber organization. For the realization of the stretching function, a bioreactor was designed and produced using 3D printing technique with polylactic acid (PLA) material. After 4 weeks of culture on the bioreactors, tensile testing and histology analysis were applied onto the constructs for exploration of potential effect of stretching during culture. As a result, the 3D printed bioreactor successfully realized the stretching function on meniscal enthesis constructs. Stretched constructs showed more longitudinal fiber bundles while less radial ones. Stretching stimulation also increased the strain of failure while decreased the tensile modulus and ultimate tensile stress of the constructs. For further research, parameters like stretching rate, culture time before stretching and directions of loading should be considered for improvement of fiber organization and mechanical properties of meniscal enthesis constructs.