Jasmine Chong (MHSc): Development of an in vitro outer annulus fibrosus-cartilage endplate interface model

March 14, 2018 @ 9:30 am – 10:00 am
Rosebrugh Building
Rosebrugh Bldg, Toronto, ON M5S 3G9

Room: RS 211


INTRODUCTION: The intervertebral disc consists of annulus fibrosus (AF) tissue that surrounds a centrally placed nucleus pulposus, and is integrated to adjacent vertebral bodies through a cartilage endplate (CEP). Disc degeneration can lead to chronic neck or lower back pain. As current treatments do not restore complete functionality, attention has turned to developing a biological disc replacement. Integration of an engineered disc with adjacent cartilage tissue is required to ensure mechanical stability.

HYPOTHESIS: An in vitro model of the outer AF (OAF)-CEP interface can be generated, which will allow for investigation of mechanical factors that influence integration.

METHODS: OAF cells and articular chondrocytes were isolated from bovine caudal discs and synovial joints to form their respective tissues in vitro. OAF cells were cultured on multilamellar nanofibrous polycarbonate urethane scaffolds. Resulting OAF and cartilage tissues were co-cultured for up to 4 weeks to form an OAF-CEP interface. The interface was evaluated histologically, and composition was determined by immunohistochemical staining for collagen type I, collagen type II, and aggrecan. Cellular composition was determined by labelling chondrocytes with green fluorescent CFDA dye. Interface strength was evaluated by a pull-apart test.

RESULTS: Reliable integration occurred when 2-week old OAF tissues were co-cultured with 3-day old cartilage. The interface stained positively for collagen type I (OAF), collagen type II and aggrecan (cartilage). Chondrocytes remained localized to the cartilage tissue and OAF cells were seen invading the cartilage at the interface. Preliminary results revealed no significant differences in mechanical strength between 3 and 4-week old interface constructs.

CONCLUSION: It is possible to engineer a biological AF-CEP interface model. Future study will focus on comparing this model to native interface tissue, and on determining the role of dynamic compressive loading on interface strength and composition.