Modulation of extracellular matrix by annulus fibrosus cells on tailored silk based angle-ply intervertebral disc construct

Abstract

Reconstruction of native tissue's anatomical and biophysical milieu dictates the success of tissue engineered graft's cellular fate. Herein, we report a facile fabrication procedure to replicate the anatomical and biomechanical features of annulus fibrosus (AF) tissue. A seamless, full thickness disc-like angle-ply construct was fabricated using silk fibroin (SF) protein. To mimic the gradual transition of mechanical gradient from inner to outer region of native AF tissue, SF proteins from two different sources (namely Bombyx mori, BM SF as mulberry, and Antheraea assamensis, AA SF and Philosamia ricini, PR SF as non-mulberry) were blended that provided differential mechanical and cell binding properties. Fabricated constructs were physicochemically and biologically characterized. The seeded porcine AF cells were found to proliferate and align along the lamellar pores as visualized through staining. Gene expression study concluded higher expression of collagen-I with enhancement of mechanical properties, whereas an opposite trend was observed for both collagen-II and aggrecan. Overall, the angle-ply construct with tailored mechanical properties supported cellular alignment and proliferation, and modulated the extracellular matrix (ECM) deposition forming a functional AF tissue like construct, thus providing a robust foundation as an alternative tissue engineered strategy in intervertebral disc (IVD) regeneration for future replacement therapy.