Intervertebral disc (IVD) degeneration is not completely understood because of the lack of relevant models. In vivo models are inappropriate because animals are quadrupeds. IVD is composed of the Nucleus Pulposus (NP) and the Annulus Fibrosus (AF), an elastic tissue that surrounds NP. AF consists of concentric lamellae made of collagen I and glycosaminoglycans with fibroblast-like cells located between layers. In this study, we aimed to develop a novel 3D in vitro model of Annulus Fibrosus to study its degeneration. For this purpose, we reproduced the microenvironment of AF cells using 3D printing. An ink consisting of dense collagen (30 mg.mL-1) and tyramine-functionalized hyaluronic acid (THA) at 7.5 mg.mL-1 was first designed by modulating pH and [NaCl] in order to inhibit the formation of polyionic complexes between collagen and THA. Then, composite inks were printed in different gelling baths to form collagen hydrogels. Last, THA photocrosslinking using eosin and green light was performed to strengthen hydrogels. Selected 3D printed constructs were then cellularized with fibroblasts.INTRODUCTION
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