Gadolinium enhancement in newly diagnosed patients with lumbar disc herniations are associated with inflammatory peridiscal tissue reactions – Evidence of fragment degradation?

Association between lipid-lowering agents with intervertebral disc degeneration, sciatica and low back pain: a drug-targeted mendelian randomized study and cross-sectional observation

BACKGROUND

Abnormal lipid metabolism is linked to intervertebral disc degeneration (IVDD), sciatica, and low back pain (LBP), but it remains unclear whether targeted interventions can prevent these issues. This study investigated the causal effects of lipid-lowering drug use on IVDD, sciatica, and LBP development.

METHODS

Single-nucleotide polymorphisms (SNPs) linked to total cholesterol (TC), low-density-lipoprotein cholesterol (LDL-C), and non-high-density-lipoprotein cholesterol (non-HDL-C) were obtained from the Global Lipids Genetics Consortium's genome-wide association study (GWAS). Genes near HMGCR, PCSK9, and NPC1L1 were selected to represent therapeutic inhibition targets. Using Mendelian randomization (MR) focusing on these drug targets, we identified causal effects of PCSK9, HMGCR, and NPC1L1 on the risk of developing IVDD, sciatica, and LBP, with coronary heart disease risk serving as a positive control. Using summary data from Mendelian randomization (SMR) analysis, we evaluated potential therapeutic targets for IVDD, sciatica, and LBP through protein quantitative trait loci (pQTL). The genetic associations with IVDD, sciatica, LBP, and coronary heart disease were derived from FinnGen (discovery) and UK Biobank (replication). Additionally, a cross-sectional observational study was performed using data from the National Health and Nutrition Examination Survey (NHANES) to further investigate the connection between LBP and statin use, with a sample size of 4343 participants. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated to assess the outcomes.

RESULTS

The NHANES-based cross-sectional study indicated that non-statin use was associated with an increased risk of developing LBP (OR = 1.29, 95% CI [1.04, 1.59], P = 0.019). Moreover, Inverse-variance weighting (IVW) analysis revealed that NPC1L1-mediated reductions in TC, LDL-C, and non-HDL-C concentrations were associated with a decreased risk of developing IVDD (P = 9.956E-03; P = 3.516E-02; P = 1.253E-04). Similarly, PCSK9-mediated reductions in LDL-C and TC concentrations were linked to a lower risk of developing sciatica (P = 3.825E-02; P = 2.709E-02). Sensitivity analysis confirmed the stability and reliability of the MR results. MST1 (macrophage stimulating 1) levels was inversely associated with IVDD, sciatica, and LBP risks.

CONCLUSION

The results of cross-sectional study suggested that non-use of statins was positively correlated with LBP. The results of Mendelian randomization study suggest that NPC1L1 could lower the risk of developing IVDD by reducing TC, LDL-C, and non-HDL-C levels. Additionally, PCSK9 may reduce the risk of developing sciatica by lowering LDL-C and TC levels. In contrast, HMGCR appears to have no significant effect on IVDD, sciatica, or LBP development. Nonetheless, further research is needed to verify these preliminary results. MST1 warrants further exploration as a potential therapeutic target. It is necessary to do further research to validate these findings.

Characteristics and mechanisms of resorption in lumbar disc herniation

Lumbar disc herniation (LDH) can be spontaneously absorbed without surgical treatment. However, the pathogenesis and physiological indications for predicting protrusion reabsorption are still unclear, which prevents clinicians from preferentially choosing conservative treatment options for LDH patients with reabsorption effects. The purpose of this review was to summarize previous reports on LDH reabsorption and to discuss the clinical and imaging features that favor natural absorption. We highlighted the biological mechanisms involved in the phenomenon of LDH reabsorption, including macrophage infiltration, inflammatory responses, matrix remodeling, and neovascularization. In addition, we summarized and discussed potential clinical treatments for promoting reabsorption. Current evidence suggests that macrophage regulation of inflammatory mediators, matrix metalloproteinases, and specific cytokines in intervertebral disc is essential for the spontaneous reabsorption of LDH.

Lumbar disc extrusions reduce faster than bulging discs due to an active role of macrophages in sciatica

OBJECTIVE

This retrospective observational histological study aims to associate the size and type of disc herniation with the degree of macrophage infiltration in disc material retrieved during disc surgery in patients with sciatica.

METHODS

Disc tissue of 119 sciatica patients was embedded in paraffin and stained with hematoxylin and CD68. Tissue samples were categorized as mild (0-10/cm2), moderate (10-100/cm2), and considerable (> 100/cm2) macrophage infiltration. All 119 patients received an MRI at baseline, and 108 received a follow-up MRI at 1-year. MRIs were reviewed for the size and type of the disc herniations, and for Modic changes in the vertebral endplates.

RESULTS

Baseline characteristics and duration of symptoms before surgery were comparable in all macrophage infiltration groups. The degree of macrophage infiltration was not associated with herniation size at baseline, but significantly associated with reduction of size of the herniated disc at 1-year post surgery. Moreover, the degree of macrophage infiltration was higher in extrusion in comparison with bulging (protrusion) of the disc. Results were comparable in patients with and without Modic changes.

CONCLUSION

Macrophage infiltration was positively associated with an extruded type of disc herniation as well as the extent of reduction of the herniated disc during 1-year follow-up in patients with sciatica. This is an indication that the macrophages play an active role in reducing herniated discs. An extruded disc herniation has a larger surface for the macrophages to adhere to, which leads to more size reduction.

The contradictory effect of macrophage-related cytokine expression in lumbar disc herniations: a systematic review

PURPOSE

Sciatic symptoms due to lumbar disc herniation are likely to be caused not solely by mechanical compression of the nerve root, but also by pain-inducing elements from inflammatory processes. Key components in the inflammatory reaction are M1 and M2 macrophages, with the M1 type being associated with pro-inflammatory processes and M2 with anti-inflammatory-processes.

METHOD

The present systematic review summarizes all studies on associations between M1 and M2 macrophages and their related inflammation factors and pain symptoms in lumbar disc herniations. Literature search was performed using an optimally sensitive search string. Studies were selected for inclusion by means of predefined inclusion and exclusion criteria and subsequently graded for risk of bias. A total of 14 studies were included. Overall risk of bias was moderate (8/14), and three studies had high risk of bias and three has low risk of bias.

RESULTS

Regarding M1-related cytokines, high levels of TNF-α, TNFR1, IL-6, IL-8, and IFN-γ were all associated high VAS scores. In contrast, high levels of TNFR2 were associated with lower VAS scores. Moreover, no associations were found for IL-1a and IL-1β. Results regarding M2-related cytokines revealed the opposite: high levels of both IL-4 and IL-10 were associated with lower VAS scores. No associations were established for TGF-β. Moreover, the presence of macrophages (CD68) was negatively associated with VAS scores.

CONCLUSION

While M1-related pro-inflammatory cytokines worsen pain symptoms, M2-related anti-inflammatory cytokines alleviate pain symptoms. Nevertheless, the present evidence is limited, and further research on the underlying pathophysiological mechanism in sciatica is required. These slides can be retrieved under Electronic Supplementary Material.

Disc inflammation and Modic changes show an interaction effect on recovery after surgery for lumbar disc herniation

Purpose

To study the interaction between Modic changes (MC) and inflammation by macrophages in the disc, in relation to clinical symptoms before and after discectomy for lumbar disc herniation.

Methods

Disc tissue was embedded in paraffin and stained with haematoxylin and CD68. Subsequently, tissue samples were categorized for degree of inflammation. Type of MC was scored on MRI at baseline. Roland Disability Questionnaire (RDQ) score and visual analogue scale for back pain and leg pain separately were considered at baseline and 1-year follow-up post-surgery. Main and interaction effects of MC and inflammation were tested against clinical outcome questionnaires. In addition, this analysis was repeated in bulging and extruded discs separately.

Results

Disc material and MRI’s of 119 patients were retrieved and analysed. Forty-eight patients demonstrated mild inflammation, 45 showed moderate inflammation, and 26 showed considerable inflammation. In total, 49 out of 119 patients demonstrated MC. Grade of disc inflammation did not associate with the presence of MC. At baseline, no main or interaction effects of MC and inflammation were found on the clinical scores. However, during follow-up after discectomy, significant interaction effects were found for RDQ score: Only in patients with MC at baseline, patients remained significantly more disabled (3.2 points p = 0.006) if they showed considerable disc inflammation compared to patients with mild inflammation. The additional analysis showed similar results in extruded discs, but no significant effects in bulging discs.

Conclusions

An interaction effect of MC and disc inflammation by macrophages is present. Only in patients with MC, those with considerable inflammation recover less satisfactory during follow-up after surgery.

Graphic abstract

These slides can be retrieved under Electronic Supplementary Material.

Gadolinium Enhancement Is Not Associated With Disc Inflammation in Patients With Sciatica

STUDY DESIGN

Retrospective observational histological study.

OBJECTIVE

To evaluate the reliability of gadolinium enhancement as a marker for inflammation by associating gadolinium enhancement findings with the degree of inflammation as measured by macrophage infiltration in disc material retrieved during disc surgery in patients with sciatica.

SUMMARY OF BACKGROUND DATA

Disc inflammation often occurs in sciatica patients, a noninvasive tool that is used to assess disc inflammation is Gadolinium enhanced MR imaging.

METHODS

Disc tissue was retrieved from patients in the Sciatica trial (N = 119), a multicenter randomized controlled trial in patients with sciatica. Disc tissue was embedded in paraffin and stained with hematoxylin and CD68. Tissue samples were categorized as mild (0-10 macrophages/cm), moderate (10-100 macrophages/cm), and considerable (>100 macrophages/cm) inflammation. Of the 119 MRIs, 96 were additionally performed with contrast-enhanced gadolinium.

RESULTS

Seventy-four patients showed gadolinium enhancement of the disc herniation and 26 of the nerve root. Degree of inflammation by macrophages was not associated with gadolinium enhancement of nerve roots or herniated discs. These results did not change if the patient groups with and without Modic type 2 changes were evaluated separately. Furthermore, no associations were observed between gadolinium enhancement and presence of Modic type 2 changes.

CONCLUSION

This study found gadolinium enhanced MRI findings to be unreliable as an indicator for inflammation of disc herniation or nerve root in patients with sciatica.

LEVEL OF EVIDENCE

2.

Therapeutic effect of percutaneous endoscopic lumbar discectomy on lumbar disc herniation and its effect on oxidative stress in patients with lumbar disc herniation

This study investigated the therapeutic effect of percutaneous endoscopic lumbar discectomy on lumbar disc herniation, and explored its effect on oxidative stress in patients with lumbar disc herniation. One hundred and ten patients with lumbar disc herniation were selected in The Affiliated People's Hospital of Shanxi Medical University from May 2015 to May 2016. Patients were divided into control group (n=50) and observation group (n=60) according to different surgical methods. Patients in control group were subjected to traditional open discectomy, while patients in observation group were treated with percutaneous endoscopic lumbar discectomy. Surgical-related indicators, ODI and VAS scores before and 3 months after surgery, serum inflammatory factors and oxidative stress indicators were compared between 2 groups. There was no significant difference in operation time between the groups. Blood loss, incision size and time of bed rest in observation group were better than those in control group (P<0.05). Compared with preoperative levels, ODI and VAS scores of the two groups were significantly reduced at 3 months after surgery, but the scores of observation group were significantly higher than those of control group (P<0.05). There were no significant differences in the levels of serum inflammatory factors TNF-α and CRP and oxidative stress indicators MDA, MPO, SOD and TAC between the two groups before surgery (P>0.05). Levels of serum inflammatory factors TNF-α and CRP and oxidative stress indicators MDA and MPO were significantly lower and levels of oxidative stress indicators SOD and TAC were significantly higher in observation group than in control group (P<0.05). Therefore, treatment of lumbar disc herniation with percutaneous endoscopic lumbar discectomy has the advantages of small trauma, less blood loss and fast recovery, and can effectively improve the dysfunction, reduce pain and serum levels of inflammatory factors, and improve the levels of oxidative stress indicators, thereby improving the surgical results. Thus, this method should be considered for wide-use.