Alteration of gene expression in intervertebral disc degeneration of passive cigarette- smoking rats: separate quantitation in separated nucleus pulposus and annulus fibrosus

Biomaterials delivery strategies to repair degenerated intervertebral discs by regulating the inflammatory microenvironment

Intervertebral disc degeneration (IVDD) is one of the leading causes of lower back pain. Although IVDD cannot directly cause death, it can cause pain, psychological burdens, and economic burdens to patients. Current conservative treatments for IVDD can relieve pain but cannot reverse the disease. Patients who cannot tolerate pain usually resort to a strategy of surgical resection of the degenerated disc. However, the surgical removal of IVDD can affect the stability of adjacent discs. Furthermore, the probability of the reherniation of the intervertebral disc (IVD) after surgery is as high as 21.2%. Strategies based on tissue engineering to deliver stem cells for the regeneration of nucleus purposes (NP) and annulus fibrosus (AF) have been extensively studied. The developed biomaterials not only locally withstand the pressure of the IVD but also lay the foundation for the survival of stem cells. However, the structure of IVDs does not provide sufficient nutrients for delivered stem cells. The role of immune mechanisms in IVDD has recently become clear. In IVDD, the IVD that was originally in immune privilege prevents the attack of immune cells (mainly effector T cells and macrophages) and aggravates the disease. Immune regulatory and inflammatory factors released by effector T cells, macrophages, and the IVD further aggravate IVDD. Reversing IVDD by regulating the inflammatory microenvironment is a potential approach for the treatment of the disease. However, the biological factors modulating the inflammatory microenvironment easily degrade in vivo. It makes it possible for different biomaterials to modulate the inflammatory microenvironment to repair IVDD. In this review, we have discussed the structures of IVDs and the immune mechanisms underlying IVDD. We have described the immune mechanisms elicited by different biological factors, including tumor necrosis factors, interleukins, transforming growth factors, hypoxia-inducible factors, and reactive oxygen species in IVDs. Finally, we have discussed the biomaterials used to modulate the inflammatory microenvironment to repair IVDD and their development.

Adjacent segment disease after minimally invasive transforaminal lumbar interbody fusion for degenerative lumbar diseases: incidence and risk factors

Study design

Retrospective study.

Objectives

To explore the incidence and risk factors for symptomatic adjacent segment disease (ASD) in patients enveloped in degenerative lumbar diseases after minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF).

Methods

Data were retrospectively analyzed on 744 patients who underwent MIS-TLIF for degenerative lumbar diseases in our hospital from October 2012 to December 2018. The patients were divided into the ASD group and non-ASD (N-ASD) group on the basis of developing ASD at follow-up, and then the incidence of ASD was calculated. Clinical and radiological risk factors were assessed over time to determine their association with ASD by excluding less important factors.

Results

Data were missing for 26 patients, while a total of 718 patients were successfully monitored after MIS-TLIF. Of the 718 individuals participated in the study, 34 (4.7%) patients plagued by ASD required surgical intervention. The average onset time of ASD was 62.7 ± 15.1 months. Univariate analysis results shows that age, bone mineral density (BMD), body mass index (BMI), preoperative adjacent intervertebral disc height and preoperative adjacent segment disc degeneration were significantly different between the ASD and N-ASD groups (p < 0.05). The logistic regression analysis results demonstrated that BMD (p = 0.039, OR = 0.986, 95% CI 0.899–1.115), BMI (p = 0.041, OR = 1.119, 95% CI 1.103–2.397), and preoperative adjacent intervertebral disc degeneration (p = 0.023, OR = 1.215, 95% CI 1.015–1.986) may be seen as risk factors for ASD after MIS-TLIF.

Conclusions

The incidence of ASD was about 4.7% in patients suffer from degenerative lumbar diseases after MIS-TLIF. BMD, BMI and preoperative adjacent intervertebral disc degeneration might be the risk factors for the occurrence of ASD after MIS-TLIF. Our research also suggested that patients with lower BMD, higher BMI and disc preoperative adjacent segment disc degeneration were more likely to develop ASD after MIS-TLIF.

Anti-degenerative effect of melatonin on intervertebral disc: protective contribution against inflammation, oxidative stress, apoptosis, and autophagy

Intervertebral disc (IVD) degeneration is a leading cause of lower back pain. Although the etiology of IVD degeneration (IVDD) is unclear, excessive oxidative stress, inflammation and apoptosis and disruption of autophagy play important role in the pathogenesis of IVDD. Therefore, finding a solution to mitigate these processes could stop or reduce the development of IVDD. Melatonin, a powerful antioxidant, plays an important role in regulating cartilage tissue hemostasis. Melatonin inhibits destruction of extracellular matrix (ECM) of disc. Melatonin preserves ECM contents including sox-9, aggrecan, and collagen II through inhibiting matrix degeneration enzymes such as MMP-13. These protective effects may be mediated by the inhibition of oxidative stress, inflammation and apoptosis, and regulation of autophagy in IVD cells.

Relationship of lumbar disc degeneration with hemoglobin value and smoking

BACKGROUND/OBJECTIVE

Although a number of studies report an important effect of smoking on disc degeneration and herniation, others did not identify such a relationship. The purpose of this study was to assess the relationship of lumbar disc degeneration with hemoglobin value and smoking.

METHODS

The study included 200 adult patients who presented to the neurosurgery polyclinic with a complaint of back pain. Smoking habits were classified as "smoking for more than 10 years", "smoking for less than 10 years", and "not smoking". Lumbar disc degeneration was classified on modified Pfirrmann score according to lumbar MR images. Degeneration level was compared according to smoking group on Kruskal-Wallis test. The relationship between hemoglobin value and disc degeneration according to smoking group was assessed on the Spearman correlation coefficient.

RESULTS

Disc degeneration values were significantly different between groups in L5-S1, L4-L5 and L3-L4 (P=0.018, P=0.012, P=0.038). Degeneration levels in L5-S1 in those who did not smoke were significantly lower than in those who smoked for both less and more than 10 years (P=0.048, P=0.022). No significant differences were found in degeneration level between those who smoked for more versus less than 10 years. For L3-L4 degeneration, there was a significant relationship with hemoglobin value in the group that did not smoke and in the group that smoked for more than 10 years (r=-0.395; P=0.009, r=0.329; P=0.018).

CONCLUSION

This study found that, when risk factors such as systemic disease, heavy working conditions, obesity, trauma and family history were excluded, smoking increased lumbar disc degeneration. In addition, chronic smoking was found to increase hemoglobin values.

Detection of apoptosis and matrical degeneration within the intervertebral discs of rats due to passive cigarette smoking

Although low-back pain is considered to be associated with cigarette smoking, the influence of cigarette smoking on the intervertebral discs (IVD) has not been confirmed. We established a rat model of passive cigarette smoking-induced IVD degeneration, and investigated the cytohistological changes in the IVD and the accompanying changes in gene expression. IVD from rats exposed to 8 weeks of passive cigarette smoking were stained with Elastica van Gieson, and exhibited marked destruction of the supportive structure of the reticular matrix in the nucleus pulposus (NP). Positive signals on safranin O, alcian blue, type II collagen and aggrecan staining were decreased in the destroyed structure. Safranin O and type II collagen signals were also decreased in the cartilage end-plate (CEP) after 4- and 8-weeks of cigarette smoking. In the CEP, the potential for apoptosis was increased significantly, as demonstrated by staining for single-strand DNA. However, there were no signs of apoptosis in the NP or annulus fibrosus cells. Based on these findings, we hypothesized that passive cigarette smoking-induced stress stimuli first affect the CEP through blood flow due to the histological proximity, thereby stimulating chondrocyte apoptosis and reduction of the extracellular matrix (ECM). This leads to reduction of the ECM in the NP, destroying the NP matrix, which can then progress to IVD degeneration.

Inflammatory Processes Associated with Canine Intervertebral Disc Herniation

Intervertebral disc herniation (IVDH) is an important pathology in humans and also in dogs. While the molecular disease mechanisms are well investigated in humans, little is known about the inflammatory mediators in naturally occurring canine IVDH. The objective of this study was to investigate whether the involved proinflammatory cytokines in human IVDH are also key cytokines in canine IVDH and thus to elucidate the suitability of the dog as a model for human trials. 59 samples from 25 dogs with surgically confirmed thoracolumbar IVDH were collected and classified in three subgroups: herniated (H), affected non-herniated (NH) disc, and adjacent non-affected (NA) disc. Discs from 11 healthy dogs acted as controls (C). Samples were analyzed for IL-1, IL-6, IL-8, and TNF-α expression (qPCR/ELISA) as well as cell infiltration and activation of the MAP kinase pathways (immunohistochemistry). Gene and protein expression of all key cytokines could be detected in IVDH affected dogs. Canine IVDH was significantly associated with a higher gene expression of IL-6 (H > C, NH > C) and TNF-α (H > C, NH > C, NA > C) and a significant down-regulation of IL-1β (H < C). Dogs with spontaneous pain had significantly higher IL-6 mRNA compared to those with pain arising only upon palpation. An inter-donor comparison (H and HN relative to NA) revealed a significant increase of IL-6 gene expression (H > NA, NH > NA). IL-8 (H > C, NA > C) and TNF-α (NH > C) protein levels were significantly increased in diseased dogs while inversely, IL-6 protein levels were significantly higher in patients with better clinical outcome. Aside from resident IVD cells, mostly monocytes and macrophages were found in extruded material, with concomitant activation of extracellular signal-regulated kinase p38 in the majority of samples. Dogs with spontaneous IVDH might provide a useful model for human disc diseases. Although the expression of key cytokines found in human IVDH was also demonstrated in canine tissue, the inflammatory mechanisms accompanying canine IVDH diverges partially from humans, which will require further investigations in the future. In dogs, IL-6 seems to play an important pathological role and may represent a new potential therapeutic target for canine patients.

The Effect of Smoking on Spinal Fusion

BACKGROUND

Spinal fusion surgery is performed about half a million times per year in the United States and millions more worldwide. It is an effective method for reducing pain, increasing stability, and correcting deformity in patients with various spinal conditions. In addition to being a well-established risk factor for a variety of medical conditions, smoking has deleterious effects on the bone healing of spinal fusions. This review aims to specifically analyze the ways in which smoking affects the outcomes of spinal fusion and to explore ways in which these negative consequences can be avoided.

PURPOSE

This article provides a complete understanding of the ways smoking affects spinal fusion from a biochemical and clinical perspective. Recommendations are also provided for ways in which surgeons can limit patient exposure to the most serious negative outcomes associated with cigarette smoking.

STUDY DESIGN/SETTING

This study was a retrospective literature review done using the NCBI database. The research was compiled at NYU Hospital for Joint Diseases and the NYU Center for Musculoskeletal Care.

METHODS

A comprehensive literature review was done spanning research on a variety of subjects related to smoking and spinal fusion surgery. The biochemistry of smoking and fusion healing were examined in great detail. In addition, both in vivo animal studies and human clinical studies were evaluated to explore fusion success related to the effects of smoking and its biochemical factors on spinal fusion surgery.

RESULTS

Smoking significantly increases the risk of pseudoarthrosis for patients undergoing both lumbar and cervical fusions. In addition to nonunion, smoking also increases the risk of other perioperative complications such as infection, adjacent-segment pathology, and dysphagia. Treatment options are available that can be explored to reduce the risk of smoking-related morbidity, such as nicotine replacement therapy and use of bone morphogenetic proteins (BMPs).

CONCLUSIONS

It has been clearly demonstrated from both a biochemical and clinical perspective that smoking increases the rate of perioperative complications for patients undergoing spinal fusion surgery, particularly pseudoarthosis. It has also been shown that there are certain approaches that can reduce the risk of morbidity. The most important recommendation is smoking cessation for four weeks after surgery. In addition, patients may be treated with certain surgical techniques, including the use of BMPs, to reduce the risk of pseudoarthrosis. Lastly, nicotine replacement therapy is an area of continued interest in relation to spinal fusion outcomes and more research needs to be done to determine its efficacy moving forward.

ADAMTS5 Deficiency Protects Mice From Chronic Tobacco Smoking-induced Intervertebral Disc Degeneration

STUDY DESIGN

ADAMTS5-deficient and wild type (WT) mice were chronically exposed to tobacco smoke to investigate effects on intervertebral disc degeneration (IDD).

OBJECTIVE

The aim of this study was to demonstrate a role for ADAMTS5 in mediating tobacco smoking-induced IDD.

SUMMARY OF BACKGROUND DATA

We previously demonstrated that chronic tobacco smoking causes IDD in mice because, in part, of proteolytic destruction of disc aggrecan. However, it was unknown which matrix proteinase(s) drive these detrimental effects.

METHODS

Three-month-old WT (C57BL/6) and ADAMTS5 mice were chronically exposed to tobacco smoke (four cigarettes/day, 5 day/week for 6 months). ADAMTS-mediated cleavage of disc aggrecan was analyzed by Western blot. Disc total glycosaminoglycan (GAG) content was assessed by dimethyl methylene blue assay and safranin O/fast green histology. Vertebral osteoporosity was measured by microcomputed tomography. Human nucleus pulposus (hNP) cell cultures were also exposed directly to tobacco smoke extract (TSE), a condensate containing the water-soluble compounds inhaled by smokers, to measure ADAMTS5 expression and ADAMTS-mediated cleavage of aggrecan. Activation of nuclear factor (NF)-κB, a family of transcription factors essential for modulating the cellular response to stress, was measured by immunofluorescence assay.

RESULTS

Genetic depletion of ADAMTS5 prevented vertebral bone loss, substantially reduced loss of disc GAG content, and completely obviated ADAMTS-mediated proteolysis of disc aggrecan within its interglobular domain (IGD) in mice following exposure to tobacco smoke. hNP cell cultures exposed to TSE also resulted in upregulation of ADAMTS5 protein expression and a concomitant increase in ADAMTS-mediated cleavage within aggrecan IGD. Activation of NF-κB, known to be required for ADAMTS5 gene expression, was observed in both TSE-treated hNP cell cultures and disc tissue of tobacco smoke-exposed mice.

CONCLUSION

The findings demonstrate that ADAMTS5 is the primary aggrecanase mediating smoking-induced disc aggrecanolysis and IDD. Mouse models of chronic tobacco smoking are important and useful for probing the mechanisms of disc aggrecan catabolism and IDD.

LEVEL OF EVIDENCE

N/A.

Disc cell senescence in intervertebral disc degeneration: Causes and molecular pathways

The accumulation of senescent disc cells in degenerative intervertebral disc (IVD) suggests the detrimental roles of cell senescence in the pathogenesis of intervertebral disc degeneration (IDD). Disc cell senescence decreased the number of functional cells in IVD. Moreover, the senescent disc cells were supposed to accelerate the process of IDD via their aberrant paracrine effects by which senescent cells cause the senescence of neighboring cells and enhance the matrix catabolism and inflammation in IVD. Thus, anti-senescence has been proposed as a novel therapeutic target for IDD. However, the development of anti-senescence therapy is based on our understanding of the molecular mechanism of disc cell senescence. In this review, we focused on the molecular mechanism of disc cell senescence, including the causes and various molecular pathways. We found that, during the process of IDD, age-related damages together with degenerative external stimuli activated both p53-p21-Rb and p16-Rb pathways to induce disc cell senescence. Meanwhile, disc cell senescence was regulated by multiple signaling pathways, suggesting the complex regulating network of disc cell senescence. To understand the mechanism of disc cell senescence better contributes to developing the anti-senescence-based therapies for IDD.

Passive cigarette smoking changes the circadian rhythm of clock genes in rat intervertebral discs

We aimed to elucidate the molecular changes in intervertebral discs (IVDs) caused by passive smoking. Rats were subjected to 8 weeks of passive smoking; thereafter, their lumbar vertebrae were harvested. The annulus fibrosus and cartilage endplate (AF/CEP) were harvested together, and the nucleus pulposus (NP) was isolated separately. The expression of 27,342 rat genes was analyzed. In 3 "nonsmoking" rats, 96 of 112 genes whose expression varied ≥10-fold between the AF/CEP and NP were more highly expressed in the AF/CEP. With these differentially expressed genes, we uncovered novel AF/CEP and NP marker genes and indicated their possible novel functions. Although passive smoking induced less marked alteration in the gene expression profiles of both the AF/CEP and NP, multiple clock-related genes showed altered expression. These genes were expressed with a circadian rhythm in IVD cells, and most genes showed a phase shift of -6 to -9 h induced by passive smoking. Some clock-related genes showed abolished oscillation in the NP. Passive smoking also changed the expression levels of proteases and protease inhibitors and reduced the expression of NP marker genes. Thus, passive smoking induces changes in the circadian rhythm of a peripheral clock (IVD clock) that might be involved in molecular events related to IVD degeneration.

Effect of perfluorotributylamine-enriched alginate on nucleus pulposus cell: Implications for intervertebral disc regeneration

Various scaffolds have been attempted for intervertebral disc regeneration, but their effectiveness was limited by loss of nutrients within the scaffolds. It has been suggested that the disc is not severely hypoxic and limited availability of oxygen results in disc degeneration. Therefore, a certain oxygen level might be beneficial for disc regeneration, which has not been given enough attention in previous studies. Here, we used perfluorotributylamine (PFTBA) for the first time as an oxygen regulator in alginate scaffold for disc regeneration in vitro and in vivo. We found that the characteristics of alginate were not affected by PFTBA and the oxygen level of the scaffold was regulated. Then, human nucleus pulposus (NP) cells were cultured in the PFTBA-enriched alginates. It was found that PFTBA could promote NP cell survival and proliferation. In addition, 2.5% PFTBA was capable of regulating extracellular matrix (ECM) to a disc-like tissue graft with little effect on the expression of NP cell markers. Finally, 2.5% PFTBA-enriched alginate was found to restore the disc height and the ECM in a mouse disc degeneration model, indicating its beneficial effect on alleviating disc degeneration. These findings highlight the promising application of PFTBA in further intervertebral disc regeneration.

Molecular basis of intervertebral disc degeneration and herniations: what are the important translational questions?

BACKGROUND

Intervertebral disc degeneration is a common condition with few inexpensive and effective modes of treatment, but current investigations seek to clarify the underlying process and offer new treatment options. It will be important for physicians to understand the molecular basis for the pathology and how it translates to developing clinical treatments for disc degeneration. In this review, we sought to summarize for clinicians what is known about the molecular processes that causes disc degeneration.

RESULTS

A healthy disc requires maintenance of a homeostatic environment, and when disrupted, a catabolic cascade of events occurs on a molecular level resulting in upregulation of proinflammatory cytokines, increased degradative enzymes, and a loss of matrix proteins. This promotes degenerative changes and occasional neurovascular ingrowth potentially contributing to the development of pain. Research demonstrates the molecular changes underlying the harmful effects of aging, smoking, and obesity seen clinically while demonstrating the variable influence of exercise. Finally, oral medications, supplements, biologic treatments, gene therapy, and stem cells hold great promise but require cautious application until their safety profiles are better outlined.

CONCLUSIONS

Intervertebral disc degeneration occurs where there is a loss of homeostatic balance with a predominantly catabolic metabolic profile. A basic understanding of the molecular changes occurring in the degenerating disc is important for practicing clinicians because it may help them to inform patients to alter lifestyle choices, identify beneficial or harmful supplements, or offer new biologic, genetic, or stem cell therapies.

MicroRNA-93 regulates collagen loss by targeting MMP3 in human nucleus pulposus cells

OBJECTIVES

Degenerated disc disease is one of the most common medical conditions in patients suffering from low back pain. Recent studies have shown that microRNAs can regulate cell function in many pathological conditions. The aim of this study was to investigate expression and role of miR-93 in disc degeneration.

MATERIALS AND METHODS

Quantitative RT-PCR was employed to investigate level of miR-93 in degenerative nucleus pulposus (NP) tissues. Then, functional analysis of miR-93 in regulating collagen II expression was performed. Subsequently, western blotting and luciferase reporter assay were used to detect the target gene.

RESULTS

We showed that miR-93 was significantly down-regulated in degenerative NP tissues and its levels were associated with grade of disc degeneration. Overexpression of miR-93 stimulated type II collagen expression in NP cells. Moreover, MMP3 was identified as a putative target of miR-93. MiR-93 inhibited MMP3 expression by directly targeting its 3'UTR, and this was abolished by miR-93 binding site mutations. Additionally, restoration of MMP3 in miR-93-overexpressed NP cells reversed effects of type II collagen expression. Expression of MMP3 inversely correlated with miR-93 expression in degenerative NP tissues.

CONCLUSIONS

Taken together, we demonstrated that miR-93 contributed to abnormal NP cell type II collagen expression by targeting MMP3, involved in intervertebral disc degeneration.

Smoking induces transcription of the heat shock protein system in the joints

OBJECTIVES

Smoking increases the risk of developing rheumatoid arthritis (RA) and worsens the course of the disease. In the current study we analysed whether smoking can affect gene expression directly in the joints.

METHODS

Synovial fibroblasts were incubated with 5% cigarette smoke extract and changes in gene expression were detected using whole genome microarrays and verified with real-time PCR. Synovial tissues were obtained from smoking and non-smoking patients with RA undergoing joint replacement surgery and from mice exposed to cigarette smoke or ambient air in a whole body exposure chamber for 3 weeks.

RESULTS

Microarray and real-time PCR analysis showed a significant upregulation of the heat shock proteins DnaJA4, DnaJB4, DnaJC6, HspB8 and Hsp70 after stimulation of synovial fibroblasts with 5% cigarette smoke extract. Similarly, in synovial tissues of smokers with RA the expression of DnaJB4, DnaJC6, HspB8 and Hsp70 was significantly higher compared with non-smokers with RA. Upregulation of DnaJB4 and DnaJC6 in joints by smoking was also confirmed in mice exposed to cigarette smoke.

CONCLUSIONS

Our data clearly show that smoking can change gene expression in the joints, which can lead to the activation of signalling pathways that promote development of autoimmunity and chronic joint inflammation.

Investigating the role of DNA damage in tobacco smoking-induced spine degeneration

BACKGROUND CONTEXT

Tobacco smoking is a key risk factor for spine degeneration. However, the underlying mechanism by which smoking induces degeneration is not known. Recent studies implicate DNA damage as a cause of spine and intervertebral disc degeneration. Because tobacco smoke contains many genotoxins, we hypothesized that tobacco smoking promotes spine degeneration by inducing cellular DNA damage.

PURPOSE

To determine if DNA damage plays a causal role in smoking-induced spine degeneration.

STUDY DESIGN

To compare the effect of chronic tobacco smoke inhalation on intervertebral disc and vertebral bone in normal and DNA repair-deficient mice to determine the contribution of DNA damage to degenerative changes.

METHODS

Two-month-old wild-type (C57BL/6) and DNA repair-deficient Ercc1(-/Δ) mice were exposed to tobacco smoke by direct inhalation (4 cigarettes/day, 5 days/week for 7 weeks) to model first-hand smoking in humans. Total disc proteoglycan (PG) content (1,9-dimethylmethylene blue assay), PG synthesis ((35)S-sulfate incorporation assay), aggrecan proteolysis (immunoblotting analysis), and vertebral bone morphology (microcomputed tomography) were measured.

RESULTS

Exposure of wild-type mice to tobacco smoke led to a 19% increase in vertebral porosity and a 61% decrease in trabecular bone volume. Intervertebral discs of smoke-exposed animals also showed a 2.6-fold decrease in GAG content and an 8.1-fold decrease in new PG synthesis. These smoking-induced degenerative changes were similar but not worse in Ercc1(-/Δ) mice.

CONCLUSIONS

Short-term exposure to high levels of primary tobacco smoke inhalation promotes degeneration of vertebral bone and discs. Disc degeneration is primarily driven by reduced synthesis of proteoglycans needed for vertebral cushioning. Degeneration was not exacerbated in congenic DNA repair-deficient mice, indicating that DNA damage per se does not have a significant causal role in driving smoke-induced spine degeneration.

Smoking Cessation Related to Improved Patient-Reported Pain Scores Following Spinal Care

BACKGROUND

Smoking is associated with low back pain, intervertebral disc disease, inferior patient outcomes following surgical interventions, and increased rates of postoperative complications. The purpose of the present study was to examine the effect of smoking and smoking cessation on pain and disability in patients with painful spinal disorders.

METHODS

We examined a prospectively maintained database of records for 5333 patients with axial or radicular pain from a spinal disorder with regard to smoking history and the patient assessment of pain on four visual analog scales during the course of care. Confounding factors, including secondary gain, sex, age, and body mass index, were also examined. The mean duration of follow-up was eight months. Multivariate statistical analysis was performed with variables including smoking status, secondary gain status, sex, depression, and age as predictors of pain and disability.

RESULTS

Compared with patients who had never smoked, patients who were current smokers reported significantly greater pain in all visual analog scale pain ratings (p < 0.001). The mean improvement in reported pain over the course of care was significantly different between nonsmokers and current smokers (p <0.001). Compared with patients who had continued to smoke, those who had quit smoking during the course of care reported significantly greater improvement in pain in visual analog scale pain ratings for worst (p = 0.013), current (p < 0.05), and average weekly pain (p = 0.024). The mean improvement in the visual analog scale pain ratings was clinically important in patients in all three groups of nonsmokers. As a group, those who had continued smoking during treatment had no clinically important improvement in reported pain.

CONCLUSIONS

Given a strong association between improved patient-reported pain and smoking cessation, this study supports the need for smoking cessation programs for patients with a painful spinal disorder.

Spine degeneration in a murine model of chronic human tobacco smokers

OBJECTIVE

To investigate the mechanisms by which chronic tobacco smoking promotes intervertebral disc degeneration (IDD) and vertebral degeneration in mice.

METHODS

Three month old C57BL/6 mice were exposed to tobacco smoke by direct inhalation (4 cigarettes/day, 5 days/week for 6 months) to model long-term smoking in humans. Total disc proteoglycan (PG) content [1,9-dimethylmethylene blue (DMMB) assay], aggrecan proteolysis (immunobloting analysis), and cellular senescence (p16INK4a immunohistochemistry) were analyzed. PG and collagen syntheses ((35)S-sulfate and (3)H-proline incorporation, respectively) were measured using disc organotypic culture. Vertebral osteoporosity was measured by micro-computed tomography.

RESULTS

Disc PG content of smoke-exposed mice was 63% of unexposed control, while new PG and collagen syntheses were 59% and 41% of those of untreated mice, respectively. Exposure to tobacco smoke dramatically increased metalloproteinase-mediated proteolysis of disc aggrecan within its interglobular domain (IGD). Cellular senescence was elevated two-fold in discs of smoke-exposed mice. Smoke exposure increased vertebral endplate porosity, which closely correlates with IDD in humans.

CONCLUSIONS

These findings further support tobacco smoke as a contributor to spinal degeneration. Furthermore, the data provide a novel mechanistic insight, indicating that smoking-induced IDD is a result of both reduced PG synthesis and increased degradation of a key disc extracellular matrix protein, aggrecan. Cleavage of aggrecan IGD is extremely detrimental as this results in the loss of the entire glycosaminoglycan-attachment region of aggrecan, which is vital for attracting water necessary to counteract compressive forces. Our results suggest identification and inhibition of specific metalloproteinases responsible for smoke-induced aggrecanolysis as a potential therapeutic strategy to treat IDD.

Differential effects of nicotine and tobacco smoke condensate on human annulus fibrosus cell metabolism

Tobacco smoking increases the risk of intervertebral disc degeneration (IDD) and back pain, but the mechanisms underlying the adverse effects of smoking are largely unknown. Current hypotheses predict that smoking contributes to IDD indirectly through nicotine-mediated vasoconstriction which limits the exchange of nutrients between the discs and their surroundings. We alternatively hypothesize that direct contact of disc cells, that is, cells in the outermost annulus and those present along fissures in degenerating discs, with the vascular system containing soluble tobacco smoking constituents could perturb normal metabolic activities resulting in IDD. In this study, we tested our hypothesis by comparing the effects of direct exposure of human disc cells to tobacco smoke condensate and nicotine on cell viability and metabolic activity. We showed that smoke condensate, which contains all of the water-soluble compounds inhaled by smokers, exerts greater detrimental effects on human disc cell viability and metabolism than nicotine. Smoke condensate greatly induced an inflammatory response and gene expression of metalloproteinases while reduced active matrix synthesis and expression of matrix structural genes. Therefore, we have demonstrated that disc cell exposure to the constituents of tobacco smoke has negative consequences which have the potential to alter disc matrix homeostasis.

Impact of passive smoking on the bones of rats

Many epidemiological surveys have identified smoking as a risk factor for osteoporosis, but it is unclear whether smoking has a direct effect on bone metabolism and if such an effect could cause osteoporosis. Therefore, we examined whether smoking causes osteoporosis based on the impact of smoke exposure on the bones of rats. A rat model of passive cigarette smoking was prepared by breeding rats in a cigarette-smoking box for 4 or 8 weeks. Histological changes, micro-computed tomographic (CT) analysis, mechanical bone strength, and bone mineral density of the femur and lumbar vertebrae were examined in these rats and in control rats that were not exposed to smoke. Lower mechanical bone strength was observed in smoke-exposed rats, but these differences were not significant. Significantly lower bone mineral density was found in the femur (P<.01) and lumbar bones (P<.001) of 8-week smoke-exposed rats compared to controls. In a micro-CT scan of lumbar vertebrae, the bone volume, trabecular thickness, trabecular number, and trabecular separation differed significantly between smoke-exposed rats and controls. Histologically, the osteocytes in the smoke-exposed rats were small (approximately 25% of the size in controls), and decreased numbers of marrow cells and osteoblasts (P<.01), as well as a black carbon dust-like substance, were found in the bone of smoke-exposed rats. These results indicate that smoking significantly decreases bone mineral density, which causes osteoporosis, and the organizational changes in the bone suggest a direct effect of smoking on bone structure. Fewer marrow cells were present in the smoke-exposed rats, and a black carbon dust-like substance was observed.

Microarray analysis of laser capture microdissected-anulus cells from the human intervertebral disc

STUDY DESIGN

Five Thompson Grade I/II discs (Group 1), 7 Grade III discs (Group 2), and 3 Grade IV discs (Group IV) were studied here in a project approved by the authors' Human Subjects Institutional Review Board.

OBJECTIVES

Our objective was to use laser capture microdissection (LCM) to harvest cells from the human anulus and to derive gene expression profiles using microarray analysis.

SUMMARY OF BACKGROUND DATA

Appropriate gene expression is essential in the intervertebral disc for maintenance of extracellular matrix (ECM), ECM remodeling, and maintenance of a viable disc cell population. During disc degeneration, cell numbers drop, making gene expression studies challenging.

METHODS

LCM was used to harvest cells from paraffin-embedded sections of human anulus tissue. Gene profiling used Affymetrix GeneChip Human X3P arrays. ANOVA and SAM permutation analysis were applied to dCHIP normalized, filtered, and log-transformed gene expression data ( approximately 33,500 probes), and data analyzed to identify genes that were significantly differentially expressed between the 3 groups.

RESULTS

We identified 47 genes that were significantly differentially expressed between the 3 groups (P < 0.001 and lowest q values). Compared with the healthiest discs (Grade I/II), 13 genes were up-regulated and 19 down-regulated in both the Grade III and the Grade IV discs. Genes with biologic significance regulated during degeneration involved cell senescence, low cell division rates, hypoxia-related genes, heat-shock protein 70 interacting protein, neuropilin 2, and interleukin-23p19 (interleukin-12 family).

CONCLUSIONS

Results expand our understanding of disc aging and degeneration and show that LCM is a valuable technique that can be used to collect mRNA amounts adequate for microarray analysis from the sparse cell population of the human anulus.