Relative telomere length and oxidative DNA damage in hypertrophic ligamentum flavum of lumbar spinal stenosis

Cellular and Molecular Mechanisms of Hypertrophy of Ligamentum Flavum

Hypertrophy of the ligamentum flavum (HLF) is a common contributor to lumbar spinal stenosis (LSS). Fibrosis is a core pathological factor of HLF resulting in degenerative LSS and associated low back pain. Although progress has been made in HLF research, the specific molecular mechanisms that promote HLF remain to be defined. The molecular factors involved in the onset of HLF include increases in inflammatory cytokines such as transforming growth factor (TGF)-β, matrix metalloproteinases, and pro-fibrotic growth factors. In this review, we discuss the current understanding of the mechanisms involved in HLF with a particular emphasis on aging and mechanical stress. We also discuss in detail how several pathomechanisms such as fibrosis, proliferation and apoptosis, macrophage infiltration, and autophagy, in addition to several molecular pathways involving TGF-β1, mitogen-activated protein kinase (MAPKs), and nuclear factor-κB (NF-κB) signaling, PI3K/AKT signaling, Wnt signaling, micro-RNAs, extracellular matrix proteins, reactive oxygen species (ROS), etc. are involved in fibrosis leading to HLF. We also present a summary of the current advancements in preclinical animal models for HLF research. In addition, we update the current and potential therapeutic targets/agents against HLF. An improved understanding of the molecular processes behind HLF and a novel animal model are key to developing effective LSS prevention and treatment strategies.

Exploring emotional well-being, spiritual, religious and personal beliefs and telomere length in chronic pain patients-A pilot study with cross-sectional design

Living with chronic pain is associated with substantial suffering and high societal costs. Patient reported outcomes (PROM's) and cellular ageing should be considered in pain management. The aim of this study was to explore correlations of PROM's and cellular ageing (telomere length [TL] and telomerase activity [TA]) amongst patients with chronic non-malignant pain. This was an explorative pilot study with cross-sectional design and recruitment was done at two pain rehabilitation facilities in Sweden, with inpatient setting/integrative care and outpatient setting/multimodal care, respectively. Eighty-four patients were enrolled by referral to pain rehabilitation in Sweden. The main outcome measures collected after admission in addition to TL and TA were the following PROMs: Numerical Rating Scale (NRS), Chronic Pain Acceptance Questionnaire (CPAQ), Hospital Anxiety and Depression Scale (HADS), Five Facets Mindfulness Questionnaire (FFMQ), WHO Quality of Life-Spiritual, Religious and Personal Beliefs (WHOQoL-SRPB) and EuroQol 5 Dimensions (EQ-5D). All the PROM's showed evidence of poor overall health status among the participants. TL correlated negatively with HADS score (r = -.219, p = .047) and positively with WHOQoL-SRPB (r = .224, p = .052). TL did not correlate with any of the pain measures. TA correlated positively with pain spread (r = .222, p = .049). A mediation of the direct effect of spiritual well-being on TL by anxiety and depression could be shown (b = 0.008; p = .045). The correlations between TL and SRPB and anxiety and depression suggest some importance of emotional and SRPB dimensions in pain management, with implications for cellular aging, which may warrant further study. Trial registration: ClinicalTrials.gov Identifier: NCT02459639.

Identification and validation of hub genes and pathways associated with mitochondrial dysfunction in hypertrophy of ligamentum flavum

Background: Lumbar spinal stenosis which can lead to irreversible neurologic damage and functional disability, is characterized by hypertrophy of ligamentum flavum (HLF). Recent studies have indicated that mitochondrial dysfunction may contribute to the development of HLF. However, the underlying mechanism is still unclear. Methods: The dataset GSE113212 was obtained from the Gene Expression Omnibus database, and the differentially expressed genes were identified. The intersection of DEGs and mitochondrial dysfunction-related genes were identified as mitochondrial dysfunction-related DEGs. Gene Ontology analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, and Gene Set Enrichment Analysis were performed. Protein-protein interaction network was constructed, and miRNAs and transcriptional factors of the hub genes were predicted via the miRNet database. Small molecule drugs targeted to these hub genes were predicted via PubChem. Immune infiltration analysis was performed to evaluate the infiltration level of immune cells and their correlation with the hub genes. In final, we measured the mitochondrial function and oxidative stress in vitro and verified the expression of hub genes by qPCR experiments. Results: In total, 43 genes were identified as MDRDEGs. These genes were mainly involved in cellular oxidation, catabolic processes, and the integrity of mitochondrial structure and function. The top hub genes were screened, including LONP1, TK2, SCO2, DBT, TFAM, MFN2. The most significant enriched pathways include cytokine-cytokine receptor interaction, focal adhesion, etc. Besides, SP1, PPARGC1A, YY1, MYC, PPARG, and STAT1 were predicted transcriptional factors of these hub genes. Additionally, increased immune infiltration was demonstrated in HLF, with a close correlation between hub genes and immune cells found. The mitochondrial dysfunction and the expression of hub genes were validated by evaluation of mitochondrial DNA, oxidative stress markers and quantitative real-time PCR. Conclusion: This study applied the integrative bioinformatics analysis and revealed the mitochondrial dysfunction-related key genes, regulatory pathways, TFs, miRNAs, and small molecules underlying the development of HLF, which improved the understanding of molecular mechanisms and the development of novel therapeutic targets for HLF.

Administration of N-Acetylcysteine to Regress the Fibrogenic and Proinflammatory Effects of Oxidative Stress in Hypertrophic Ligamentum Flavum Cells

Ligamentum flavum hypertrophy (LFH) is a major cause of lumbar spinal stenosis (LSS). In hypertrophic ligamentum flavum (LF) cells, oxidative stress activates intracellular signaling and induces the expression of inflammatory and fibrotic markers. This study explored whether healthy and hypertrophic LF cells respond differently to oxidative stress, via examining the levels of phosphorylated p38 (p-p38), inducible nitric oxide synthase (iNOS), and α-smooth muscle actin (α-SMA). Furthermore, the efficacy of N-acetylcysteine (NAC), an antioxidant, in reversing the fibrogenic and proinflammatory effects of oxidative stress in hypertrophic LF cells was investigated by assessing the expression levels of p-p38, p-p65, iNOS, TGF-β, α-SMA, vimentin, and collagen I under H2O2 treatment with or without NAC. Under oxidative stress, p-p38 increased significantly in both hypertrophic and healthy LF cells, and iNOS was elevated in only the hypertrophic LF cells. This revealed that oxidative stress negatively affected both hypertrophic and healthy LF cells, with the hypertrophic LF cells exhibiting more active inflammation than did the healthy cells. After H2O2 treatment, p-p38, p-p65, iNOS, TGF-β, vimentin, and collagen I increased significantly, and NAC administration reversed the effects of oxidative stress. These results can form the basis of a novel therapeutic treatment for LFH using antioxidants.

Harpagophytum procumbens Inhibits Iron Overload-Induced Oxidative Stress through Activation of Nrf2 Signaling in a Rat Model of Lumbar Spinal Stenosis

Lumbar spinal stenosis (LSS) is a common degenerative spinal condition in older individuals that causes impaired walking and other disabilities due to severe lower back and leg pain. Ligamentum flavum hypertrophy is a major LSS cause that may result from oxidative stress caused by degenerative cascades, including imbalanced iron homeostasis that leads to excessive reactive oxygen species production. We investigated the effects of Harpagophytum procumbens (HP) on iron-induced oxidative stress associated with LSS pathophysiology. Primary spinal cord neuron cultures were incubated in FeSO₄-containing medium, followed by addition of 50, 100, or 200 μg/mL HP. Cell viability was assessed by CCK-8 and live/dead cell assays and by propidium iodide-live imaging. In an in vivo rat model of LSS, HP were administered at 100, 200, and 400 mg/kg, and disease progression was monitored for up to 3 weeks. We investigated the in vitro and in vivo effects of HP on iron-induced neurotoxicity by immunochemistry, real-time PCR, and flow cytometry. HP exerted neuroprotective effects and enhanced neurite outgrowths of iron-injured rat primary spinal cord neurons in vitro. HP treatment significantly reduced necrotic cell death and improved cells' antioxidative capacity via the NRF2 signaling pathway in iron-treated neurons. At 1 week after HP administration in LSS rats, the inflammatory response and oxidative stress markers were substantially reduced through regulation of excess iron accumulation. Iron that accumulated in the spinal cord underneath the implanted silicone was also regulated by HP administration via NRF2 signaling pathway activation. HP-treated LSS rats showed gradually reduced mechanical allodynia and amelioration of impaired behavior for 3 weeks. We demonstrated that HP administration can maintain iron homeostasis within neurons via activation of NRF2 signaling and can consequently facilitate functional recovery by regulating iron-induced oxidative stress. This fundamentally new strategy holds promise for LSS treatment.

Telomere Shortening and Increased Oxidative Stress in Lumbar Disc Degeneration

Lumbar disc degeneration (LDD) contributes to low back pain. This study aimed to determine relative telomere length (RTL), oxidative stress status, and antioxidant levels and examine the relationships between RTL, oxidative stress, and the severity in LDD patients. A total of 100 subjects, 50 LDD patients and 50 healthy controls, were enrolled in the case−control study. Blood leukocyte RTL was analyzed using quantitative real-time polymerase chain reaction. Lipid peroxidation was determined by malondialdehyde (MDA) assay. Plasma 8-hydroxy 2′-deoxyguanosine (8-OHdG) values were determined using enzyme-linked immunosorbent assay. Total antioxidant capacity (TAC) and ferric reducing antioxidant power (FRAP) in plasma were also measured. The LDD patients had significantly shorter telomeres than the healthy controls (p = 0.04). Blood leukocyte RTL was inversely correlated with the LDD severity (r = −0.41, p = 0.005). Additionally, plasma MDA and 8-OHdG levels were markedly greater in LDD patients than in the controls (p = 0.01 and p = 0.002, respectively). Furthermore, the plasma MDA level showed a positive correlation with the radiographic severity (r = 0.49, p = 0.001). There was a positive correlation between plasma 8-OHdG and the severity (r = 0.60, p < 0.001). Moreover, plasma TAC and FRAP levels were significantly lower in LDD patients than in the controls (p = 0.04). No significant differences in plasma TAC and FRAP were observed among the three groups of LDD severity. We found that RTL was negatively correlated with the severity while plasma MDA and 8-OHdG levels were positively correlated with the severity. These findings suggest that blood leukocyte RTL, plasma MDA, and 8-OHdG may have potential as noninvasive biomarkers for the assessment of severity in LDD.

Premature Senescence and Telomere Shortening Induced by Oxidative Stress From Oxalate, Calcium Oxalate Monohydrate, and Urine From Patients With Calcium Oxalate Nephrolithiasis

Oxidative stress, a well-known cause of stress-induced premature senescence (SIPS), is increased in patients with calcium oxalate (CaOx) kidney stones (KS). Oxalate and calcium oxalate monohydrate (COM) induce oxidative stress in renal tubular cells, but to our knowledge, their effect on SIPS has not yet been examined. Here, we examined whether oxalate, COM, or urine from patients with CaOx KS could induce SIPS and telomere shortening in human kidney (HK)-2 cells, a proximal tubular renal cell line. Urine from age- and sex-matched individuals without stones was used as a control. In sublethal amounts, H₂O₂, oxalate, COM, and urine from those with KS evoked oxidative stress in HK-2 cells, indicated by increased protein carbonyl content and decreased total antioxidant capacity, but urine from those without stones did not. The proportion of senescent HK-2 cells, as indicated by SA-βgal staining, increased after treatment with H₂O₂, oxalate, COM, and urine from those with KS. Expression of p16 was higher in HK-2 cells treated with H₂O₂, oxalate, COM, and urine from those with KS than it was in cells treated with urine from those without stones and untreated controls. p16 was upregulated in the SA-βgal positive cells. Relative telomere length was shorter in HK-2 cells treated with H₂O₂, oxalate, COM, and urine from those with KS than that in cells treated with urine from those without stones and untreated controls. Transcript expression of shelterin components (TRF1, TRF2 and POT1) was decreased in HK-2 cells treated with H₂O₂, oxalate, COM, and urine from those with KS, in which case the expression was highest. Urine from those without KS did not significantly alter TRF1, TRF2, and POT1 mRNA expression in HK-2 cells relative to untreated controls. In conclusion, oxalate, COM, and urine from patients with CaOx KS induced SIPS and telomere shortening in renal tubular cells. SIPS induced by a lithogenic milieu may result from upregulation of p16 and downregulation of shelterin components, specifically POT1, and might contribute, at least in part, to the development of CaOx KS.

Elevated Mitochondrial Reactive Oxygen Species within Cerebrospinal Fluid as New Index in the Early Detection of Lumbar Spinal Stenosis

Lumbar spinal stenosis (LSS) is a common neurodegenerative condition. However, how neurogenic claudication develops with severe leg pain has not yet been clearly elucidated. Moreover, cerebrospinal fluid (CSF) physiology at the lumbosacral level is poorly understood because of the difficulties involved in quantification and visualization. Recent studies have suggested that assessment of mitochondrial function in CSF provides an indirect way to assess neurological disorders and an important feature of disease progression. In this study, we assessed the relevance of endogenous extracellular mitochondria in the CSF of rats after LSS. Mitochondrial changes within the CSF were analyzed following LSS at 1 week using flow cytometry. An increase in cell size and number was observed in CSF with LSS, and reactive oxygen species (ROS) levels were also increased within the CSF at 1 week in the LSS group. Elevated mitochondrial ROS and functional changes in the CSF are hallmarks of LSS. The present study is the first to demonstrate that elevated mitochondrial ROS within the CSF is a new index for the early detection of LSS. Moreover, it may represent a potential novel treatment target for LSS.

SIRT6 enhances telomerase activity to protect against DNA damage and senescence in hypertrophic ligamentum flavum cells from lumbar spinal stenosis patients

Lumbar spinal stenosis (LSS) is a condition wherein patients exhibit age-related fibrosis, elastin-to-collagen ratio reductions, and ligamentum flavum hypertrophy. This study was designed to assess the relationship between SIRT6 and telomerase activity in hypertrophic ligamentum flavum (LFH) cells from LSS patients. We observed significant reductions in SIRT6, TPP1, and POT1 protein levels as well as increases in telomerase reverse transcriptase (TERT) levels and telomerase activity in LFH tissues relative to non- hypertrophic ligamentum flavum (LFN) tissues. When SIRT6 was overexpressed in these LFH cells, this was associated with significant increases in telomerase activity and a significant reduction in fibrosis-related protein expression. These effects were reversed, however, when telomerase activity was inactivated by hTERT knockdown in these same cells. SIRT6 overexpression was further found to reduce the frequency of senescence-associated β-galactosidase (SA-β-Gal)-positive LFH cells and to decrease p16, MMP3, and L1 mRNA levels and telomere dysfunction-induced foci (TIFs) in LFH cells. In contrast, hTERT knockdown-induced telomerase inactivation eliminated these SIRT6-dependent effects. Overall, our results indicate that SIRT6 functions as a key protective factor that prevents cellular senescence and telomere dysfunction in ligamentum flavum cells, with this effect being at least partially attributable to SIRT6-dependent telomerase activation.

Ligamentum flavum fibrosis and hypertrophy: Molecular pathways, cellular mechanisms, and future directions

Hypertrophy of ligamentum flavum (LF), along with disk protrusion and facet joints degeneration, is associated with the development of lumbar spinal canal stenosis (LSCS). Of note, LF hypertrophy is deemed as an important cause of LSCS. Histologically, fibrosis is proved to be the main pathology of LF hypertrophy. Despite the numerous studies explored the mechanisms of LF fibrosis at the molecular and cellular levels, the exact mechanism remains unknown. It is suggested that pathophysiologic stimuli such as mechanical stress, aging, obesity, and some diseases are the causative factors. Then, many cytokines and growth factors secreted by LF cells and its surrounding tissues play different roles in activating the fibrotic response. Here, we summarize the current status of detailed knowledge available regarding the causative factors, pathology, molecular and cellular mechanisms implicated in LF fibrosis and hypertrophy, also focusing on the possible avenues for anti-fibrotic strategies.

Selenium-Alleviated Hepatocyte Necrosis and DNA Damage in Cyclophosphamide-Treated Geese by Mitigating Oxidative Stress

Selenium (Se) has been well recognized as an immune-enhancing agent with antioxidant and anti-tumor properties. The commonly used chemotherapy drug, cyclophosphamide (CTX), induces liver injury by increasing the reactive oxygen species (ROS) level. However, little is known about how Se alleviates CTX-induced liver injury in geese. In this study, 90 male Magang geese (3 days old) were randomly allocated into three groups (control, CTX, and Se + CTX group) with three replicates per group and ten geese per replicate. The control and CTX groups were fed a basal diet (Se content was 0.03 mg/kg). The Se + CTX group was fed a basal diet containing 0.44 mg/kg sodium selenite (Se content was 0.2 + 0.03 mg/kg). The control group was injected with 0.5 mL saline, while the CTX and Se + CTX groups were injected with CTX at 40 mg/kg body weight per day on days 21-23. The liver index, liver histology, and ultra-micromorphology detected antioxidant enzyme activity in the liver and serum. In addition, we detected the liver marker enzymes and protein levels in serum, and hepatocyte DNA damage. Se could alleviate liver development dysregulation, hepatocyte structural damage, the disturbances in antioxidant enzyme (GPx, CAT, and SOD) activity, and malondialdehyde (MDA) levels in the serum and liver. Besides, Se could alleviate the dysregulation of liver marker enzyme (ALT and AST) activity and protein (ALB and TP) levels in the serum, and DNA migration induced by CTX. In conclusion, Se may inhibit hepatocyte necrosis and DNA damage by inhibiting CTX-induced oxidative stress.

[Percutaneous full-endoscopic bilateral decompression via unilateral posterior approach for lumbar spinal stenosis]

OBJECTIVE

To design the surgical strategy of percutaneous full-endoscopic bilateral decompression via unilateral posterior approach for bilateral lumbar spinal stenosis (LSS) and to evaluate the effectiveness.

METHODS

The percutaneous full-endoscopic bilateral decompression via unilateral posterior approach for bilateral LSS was designed according to the pathological features of LSS. The technique was used to treat 42 patients with LSS between January 2016 and January 2018. There were 18 males and 24 females with an average age of 61.7 years (range, 46-81 years). The duration of symptoms was 1-20 years, with an average of 9.7 years. The surgical segment at L 4, 5 were 27 cases, at L 5, S 1 were 15 cases. The operation time and perioperative complications were recorded. Lumbar X-ray, CT, and MRI examinations were performed at 1 week, 3 months, and 1 year after operation. Visual analogue scale (VAS) score was used to evaluate the low back pain and leg pain, Oswestry disability index (ODI) was used to evaluate the lumbar function, and single continuous walking distance (SCWD) was used to evaluate lower extremity nerve function. The clinical efficacy was evaluated by MacNab criteria at 1 year after operation.

RESULTS

All patients underwent surgery successfully. The operation time was 68-141 minutes with an average of 98.2 minutes. All 42 patients were followed up 12-24 months with an average of 18.8 months. There were 2 cases of dural tears during operation, and 1 case of transient dysfunction of the lower limbs of the decompression channel after operation. All of them were cured after corresponding treatment. No serious complications such as death, major bleeding, or irreversible nerve injury occurred during follow-up. No segmental instability was found according to postoperative lumbar hyperextension and flexion X-ray films, and postoperative CT and MRI imaging showed that the stenotic lumbar spinal canal was significantly enlarged, and the compression of the nerve root was sufficient. The VAS score of low back pain and leg pain, ODI score, and SCWD at each time point after operation were significantly improved when compared with those before operation ( P<0.05); the indexes were significantly improved over time after operation, and the differences were significantly ( P<0.05). The clinical efficacy was evaluated by MacNab standard at 1 year after operation, and the results were excellent in 18 cases, good in 20 cases, fair in 3 cases, and poor in 1 case. The excellent and good rate was 90.5%.

CONCLUSION

The percutaneous full-endoscopic bilateral decompression via unilateral posterior approach for LSS is a safe and effective procedure. A well-designed surgical strategy and mastery of its technical points are important guarantees for successful operation and satisfactory results.

Blood leukocyte LINE-1 hypomethylation and oxidative stress in knee osteoarthritis

Aim

Joints inflammation is one of the most pathologic processes leading to the development of osteoarthritis (OA), possibly leading to genomic instability. LINE-1 is transposable elements, and alterations in LINE-1 methylation induced by 8-hydroxy-2′-deoxyguanosine (8-OHdG) can cause genomic instability contributing to OA development. Herein, the present study examined associations between LINE-1 methylation, 8-OHdG, and knee OA severity.

Methods

LINE-1 methylation levels were measured in 104 knee OA patients and 96 healthy controls by quantitative combined bisulfite restriction analysis. 8–OHdG was investigated by ELISA. The knee OA severity was appraised by questionnaires (VAS, WOMAC, KOOS, and lequesne index) and radiological severity based on the grading of Kellgren and Lawrence (KL) standard criteria.

Key findings

Blood leukocyte LINE-1 methylation levels were significantly lower in knee OA patients than in healthy controls. Interestingly, individuals with LINE-1 hypomethylation were significantly associated with an elevated risk of knee OA. Linear regression analysis revealed that LINE-1 methylation was independently associated with KL grading of knee OA. Furthermore, plasma 8–OHdG levels in OA cases were not significantly different from those in healthy volunteers, whereas synovial fluid 8–OHdG values were considerably higher than in paired plasma specimens of the OA subjects.

Significance

This study demonstrated that LINE-1 hypomethylation in blood leukocytes was associated with increased risk and radiographic severity of knee OA, and increased synovial fluid 8–OHdG levels were observed in knee OA patients. Collectively, LINE-1 hypomethylation and elevated 8–OHdG could emerge as biomarkers indicating the severity of knee OA and may take a possible part in the pathological process of knee OA.

Decreased catalase expression is associated with ligamentum flavum hypertrophy due to lumbar spinal canal stenosis

BACKGROUND

This is an immunohistologic study of gene expression between patients and controls.This study aims to evaluate expression of the catalase gene in hypertrophied ligamentum flavum (LF) specimens obtained from patients with lumbar spinal canal stenosis (LSCS).LSCS is one of the most common spinal disorders. It is well known that LF hypertrophy plays an important role in the onset of LSCS. Although degenerative changes, aging, and mechanical stress are all thought to contribute to hypertrophy and fibrosis of the LF, the precise pathogenesis of LF hypertrophy remains unknown. Previous genetic studies have tried to determine the mechanism of LF hypertrophy. However, the association between catalase gene expression and LF hypertrophy has not yet been explored.

METHODS

LF specimens were surgically obtained from 30 patients with spinal stenosis (LSCS group) and from 30 controls with lumbar disc herniation (LDH group). LF thickness was measured at the thickest point using calipers to an accuracy of 0.01 mm during surgical intervention. The extent of LF elastin degradation and fibrosis were graded (grades 0-4) by hematoxylin and eosin staining and Masson trichrome staining, respectively. The resulting LF measurements, histologic data, and immunohistologic results were then compared between the 2 groups.

RESULTS

The average LF thickness was significantly higher in the LSCS group than in the LDH group (5.99 and 2.95 mm, respectively, P = .004). Elastin degradation and fibrosis of the LF were significantly more severe in spinal stenosis samples than in the disc herniation samples (3.04 ± 0.50 vs 0.79 ± 0.60, P = .007; 3.01 ± 0.47 vs 0.66 ± 0.42, P = .009, respectively). Significantly lower expression of catalase was observed in the perivascular area of LF samples obtained from patients with LSCS compared with controls (61.80 ± 31.10 vs 152.80 ± 41.13, respectively, P = .009).

CONCLUSION

Our findings suggest that decreased expression of catalase is associated with LF hypertrophy in patients with LSCS.