Spine-on-a-chip: Human annulus fibrosus degeneration model for simulating the severity of intervertebral disc degeneration

Abstract

The aetiology of intervertebral disc (IVD) degeneration accompanied by low back pain (LBP) is largely unknown, and there are no effective fundamental therapies. Symptomatic IVD is known to be associated with nerve root compression. However, even in the absence of nerve compression, LBP occurs in patients with IVD degeneration. We hypothesize that this phenomenon is associated with a concentration of pro-inflammatory cytokines such as interleukin (IL)-1β and tumour necrosis factor-alpha (TNF-α), which can lead to altered histologic features and cellular phenotypes observed during IVD degeneration. This study investigated the effects of the concentration of IL-1β and macrophage derived soluble factor including IL-1β and TNF-α on the painful response of human annulus fibrosus (AF) cells using a newly developed spine-on-a-chip. Human AF cells were treated with a range of concentrations of IL-1β and macrophage soluble factors. Our results show that increasing the concentration of inflammatory initiator caused modulated expression of pain-related factors, angiogenesis molecules, and catabolic enzymes. Furthermore, accumulated macrophage derived soluble factors resulted in morphological changes in human AF cells and kinetic alterations such as velocity, dendritic length, cell area, and growth rate, similar to that reported within degenerative IVD. Thus, a better understanding of the relationships between molecular and kinetic alterations can provide fundamental information regarding the pathology of IVD degenerative progression.

Microfluidic Chip with Low Constant-Current Stimulation (LCCS) Platform: Human Nucleus Pulposus Degeneration In Vitro Model for Symptomatic Intervertebral Disc

“…As a chemoattractant related to immune cell recruitment, IL-1β increases the expression of CCLs, chemokine ligand (CXCL), and IL-8 [37][38][39][40]. Our previous study also confirmed the increased expression of MMP and IL-8 [20,[41][42][43][44][45]. When stimulation by IL-1β diffusion, within the LCCS platform, was permitted to incubate channels, this study also verified the increased gene expression of IL-8, MMP-1, and MMP-3 in human NP cells.…”

In vitro model of distinct catabolic and inflammatory response patterns of endothelial cells to intervertebral disc cell degeneration

“…The IL-1β-mediated NF-κB (p65 and p50 subunits) signal transduction pathway is well known to control the expression of a number of inflammatory and catabolic genes 2 . In our previous study and the current study, IL-1β stimulation induced the translocation of p65 protein into the nucleus, resulting in the upregulation of IL-6, IL-8, MMP-1, and MMP-3 in human AF or NP cells [25][26][27] . IVD cells from degenerative conditions secreted and expressed VEGF under various experimental conditions 13,28,29 .…”

Microfluidic Disc-on-a-Chip Device for Mouse Intervertebral Disc—Pitching a Next-Generation Research Platform To Study Disc Degeneration

“…Recently, Hwang et al reported a "spine-on-a-chip" device to induce human AF cell degeneration with IL-1 for 72 h. 58 However, like most of reported microfluidic systems, AF cells were cultured in a monolayer for a short period of time, which does not replicate 3D environment of discs. Additionally, isolated human annulus cells may not maintain an annulus cell phenotype without proper ECM.…”