High amplitude and low frequency cyclic mechanical strain promotes degeneration of human nucleus pulposus cells via the NF‐κB p65 pathway

Abstract

Disc degeneration alters the structure and function of intervertebral discs and is the basis of spinal degenerative diseases. To establish the molecular mechanism of intervertebral disc degeneration caused by mechanical strain, this study examined the effects of different amplitude (3%, 9%, 19%) cyclic mechanical strain (CMS) at a low frequency (0.01 Hz) on the secretion of cartilage extracellular matrix, expression of inflammatory cytokines and catabolic proteases, and activation of NF-κB signaling pathway in human nucleus pulposus cells. We also investigated effects of low frequency and high amplitude (19%) CMS on degeneration of human nucleus pulposus cells in the presence or absence of p65 inhibitor, p65 silencing shRNA, or p65 overexpression. While 3% CMS did not significantly decrease aggrecan or type II collagen expression, or increase TNF-α, IL-1β, IL-6 expression, 9% and 19% CMS showed the significant effects. Low frequency and high amplitude (19%) CMS was found to promote p65 activation in human nucleus pulposus cells, and IL-1β was found to promote p65 nuclear translocation though IκB kinase phosphorylation. Furthermore, degeneration process of nucleus pulposus cells was found attenuated in the presence of p65 inhibitor or p65 silencing shRNA, but promoted with p65 overexpression. These data suggest that high amplitude and low frequency CMS could promote degeneration of human nucleus pulposus cells significantly via the NF-κB p65 pathway. Our findings have uncovered the effect of CMS on human nucleus pulposus cell degeneration and have identified a previously unknown intrinsic underlying mechanism.

TRPV4 Inhibition and CRISPR-Cas9 Knockout Reduce Inflammation Induced by Hyperphysiological Stretching in Human Annulus Fibrosus Cells

“…Our model exhibits features of stretch-induced low-grade mechanoflammation, representative of early-stage AF injury [ 12 ]. In agreement with previous studies [ 13 , 14 , 15 , 16 , 17 ], the hyperphysiological cyclic stretching of AF cells induced an increase in gene expression of IL6, IL8, COX2 and MMP1. This pro-inflammatory response was transient and decreased with increasing stretching durations.…”

“…This is compatible with a single continuous loading event, rather than a repetitive loading regime. The reduction of COL2A1 and ACAN mRNA in response to cyclic stretching, also previously reported by another study [ 13 ], confirms the degenerative purpose of our hyperphysiological stretching regime. The moderate but significant increase in PGE2 release caused by hyperphysiological cyclic stretching further confirms the COX2 gene expression increase.…”

“…Several studies have previously proved the detrimental effects of hyperphysiological mechanical loading on IVD cells at the molecular level. Cyclic stretching of IVD (mostly AF) cells at a high strain from 8 to 20% was shown to induce the downregulation of anabolic markers (ACAN, COL2) [ 13 ] and the upregulation of catabolic (MMP1, MMP3, MMP9, MMP13, ADAMTS4, ADAMTS5) [ 13 , 14 ] and (pro-)inflammatory (COX2, PGE2, IL1β, IL6, IL8, IL15, TLR2, TLR4, NGF, TNFα, MCP1, MCP3, MIG) [ 13 , 14 , 15 , 16 , 17 ] mediators. Stretch-induced inflammation in the IVD may be regulated by the NF-κB [ 13 ] or the mitogen-activated protein kinase (MAPK: ERK1/2, p38 and JNK) [ 17 ] signaling pathways.…”

Responses of apoptosis and matrix metabolism of annulus fibrosus cells to different magnitudes of mechanical tension in vitro

“…However, these mechanical demands are reported to be initiating factors for disc degeneration in some cases [16]. Recently, increasing evidence has indicated that cell-mediated matrix remodeling is the secondary response to mechanical stimulation during daily activities, which ultimately leads to degenerative changes [8,12,13,24–26]. For intervertebral disc, much progress has been made in explaining mechanobiologic effects of NP tissue, whereas much less has been done in investigating biological responses of AF tissue to mechanical stimuli.…”

Antiaging Factor Klotho Retards the Progress of Intervertebral Disc Degeneration through the Toll-Like Receptor 4-NF-κB Pathway

“…Also, the elasticity and loadresistance of intervertebral disc lessen. Recent studies found that a series of inflammatory factors involved in the IDD process, which closely related to the occurrence and development of IDD [1][2][3]. However, the role of various inflammatory factors and the molecular mechanisms involved in IDD is not fully definitude.…”