Annular puncture with tumor necrosis factor-alpha injection enhances painful behavior with disc degeneration in vivo

Abstract

BACKGROUND CONTEXT Painful intervertebral disc degeneration is extremely common and costly. Effective treatments are lacking because the nature of discogenic pain is complex with limited capacity to distinguish painful conditions from age-related changes in the spine. Hypothesized sources of discogenic pain include chronic inflammation, neurovascular ingrowth, and structural disruption. PURPOSE This study aimed to investigate inflammation, pro-neurovascular growth factors, and structural disruption as sources of painful disc degeneration STUDY DESIGN/SETTING This study used an in vivo study to address these hypothesized mechanisms with anterior intradiscal injections of tumor necrosis factor-alpha (TNFα), pro-neurovascular growth factors: nerve growth factor and vascular endothelial growth factor (NGF and VEGF), and saline with additional sham surgery and naïve controls. Depth of annular puncture was also evaluated for its effects on structural and painful degeneration. METHODS Rat lumbar discs were punctured (shallow or deeper puncture) and intradiscally injected with saline, TNFα, or NGF and VEGF. Structural disc degeneration was assessed using X-ray, magnetic resonance imaging (MRI), and histology. The rat painful condition was evaluated using Von Frey hyperalgesia measurements, and substance P immunostaining in dorsal root ganglion (DRG) was performed to determine the source of pain. RESULTS Saline injection increased painful responses with degenerative changes in disc height, MRI intensity, and morphologies of disc structure and cell. TNFα and NGF/VEGF accelerated painful behavior, and TNFα-injected animals had increased substance P in DRGs. Deeper punctures led to more severe disc degeneration. Multiple regression analysis showed that the painful behavior was correlated with disc height loss. CONCLUSIONS We concluded that rate and severity of structural disc degeneration was associated with the amount of annular disruption and puncture depth. The painful behavior was associated with disc height loss and discal inflammatory state, whereas pro-inflammatory cytokines might play a more important role in the level of pain, which might have resulted from enhanced DRG sensitization. These in vivo painful disc degeneration models with different severities of structural changes may be useful for investigating discogenic pain mechanisms and for screening therapies, although interpretations must note the differences between all surgically induced animal models and the human condition.

Nanoparticle fullerol alleviates radiculopathy via NLRP3 inflammasome and neuropeptides

“…Neurotrophic factors and substances involved in the pathophysiology of neuropathic pain include NGF, BDNF, substance P, and other chemokines. 44 Astrocytes and activated microglia play a role in nociceptive hypersensitivity by releasing modulators such as substance P, CGRP, and pro-inflammatory cytokines. 28,45 In the current study, GFAP immunostaining positive signals were elevated in the fullerol treated group.…”

Tumor necrosis factor-α: a key contributor to intervertebral disc degeneration

“…Annular puncture with TNF-α injection has been shown to enhance painful behavior with disc degeneration in vivo [15]. In a porcine model, lumbar discs receiving exogenous TNF-α injection display degenerative changes with annulus fissure, cell cluster, NP matrix loss, vascularization, and interleukin (IL)-1β expression in the outer annulus, suggesting TNF-α as a driver in disc degeneration [16].…”

Changes and significance of inflammatory cytokines in a rat model of cervical spondylosis

“…It also facilitates matrix degradation and upregulates substance P, suggesting it may sensitize nerves to painful responses or facilitate structural disruption (20,21). Lai et al (22) confirmed that compared with the changed cervical structure or partial neurovascular hyperplasia, the pain caused by cervical spondylosis was more closely linked with local inflammation. When comparing nucleus pulposus material from disk herniation vs. painful degenerative disk disease, higher levels of TNF-α were detected in the painful degenerative disk disease group (23,24).…”