Comparison of Annulus Fibrosus Cell Collagen Remodeling Rates in a Micro-Tissue System

It has been suggested that curvature progression in adolescent idiopathic scoliosis occurs through irreversible changes in the intervertebral discs. Strains of mice have been identified who differ in their disc wedging response upon extended asymmetrical compression. Annulus fibrosus tissue remodeling could contribute to the faster disc wedging progression previously observed in these mice. Differences in collagen remodeling capacity of annulus fibrosus cells between these in-bred mice strains was compared using an in vitro micro-tissue system. Annulus fibrosus cells of 8-10 week-old LG/J ("fast-healing") and C57BL/6J ("normal healing") mice were embedded in a micro-tissue platform and cultured for 48 hours. Hereafter, tissues were partially released and cultured for another 96 hours. Micro-tissue surface area and waistcoat contraction, collagen orientation and collagen content were measured. After 96 hours post-release, micro-tissues with annulus fibrosus cells of LG/J mice showed more surface area contraction (p < 0.001) and waistcoat contraction (p = 0.002) than C57BL/6J micro-tissues. Collagen orientation did not differ at 24 hours after partial release. However, at 96 hours, collagen in the micro-tissues from LG/J annulus fibrosus cells was aligned more than in those from C57BL/6J mice (p < 0.001). Collagen content did not differ between micro-tissues at 96 hours. Annulus fibrosus cells of inbred LG/J mice were better able to remodel and realign their collagen fibers than those from C57BL/6J mice. The remodeling of annulus fibrosus tissue could be contributing to the faster disc wedging progression observed in LG/J mice. This article is protected by copyright. All rights reserved