Healing of a painful intervertebral disc should not be confused with reversing disc degeneration: implications for physical therapies for discogenic back pain

Dynamic Pressure Stimulation Upregulates Collagen II and Aggrecan in Nucleus Pulposus Cells Through Calcium Signaling

STUDY DESIGN

An in vitro study to investigate the effect of pressure stimulation on nucleus pulposus (NP) cells.

OBJECTIVE

The aim of this study was to investigate the question whether physical stimulation can be leveraged to enhance extracellular matrix (ECM) synthesis as a preventive measure for intervertebral disc (IVD) degeneration.

SUMMARY OF BACKGROUND DATA

ECM plays an important role in regulating hydration and pressure balance of the IVD.

METHODS

Cellular stimulation devices with different pressurizing protocols were used to create a pressurized environment to cells cultures. The setup was used to mimic the pressurized conditions within IVD to investigate the effect of pressure stimulation on NP cells.

RESULTS

Pressure stimulation at 300 kPa can enhance the synthesis of ECM proteins Collagen II and aggrecan in NP cells and the effect of dynamic pressure stimulation outperformed the static one. The difference between static and dynamic pressure stimulation was due primarily to calcium signaling activated by pressure fluctuation. The superior effect of dynamic pressure holds for a wide range of stimulation durations, relating to the range of spontaneous calcium oscillations in NP cells.

CONCLUSION

The results link mechanotransduction to the downstream ECM protein synthesis and suggest slow exercises that correspond with spontaneous calcium oscillations in NP cells can be effective to stimulate ECM synthesis in IVD.

Lumbar Intervertebral Disc Herniation: Annular Closure Devices and Key Design Requirements

Lumbar disc herniation is one of the most common degenerative spinal conditions resulting in lower back pain and sciatica. Surgical treatment options include microdiscectomy, lumbar fusion, total disc replacement, and other minimally invasive approaches. At present, microdiscectomy procedures are the most used technique; however, the annulus fibrosus is left with a defect that without treatment may contribute to high reherniation rates and changes in the biomechanics of the lumbar spine. This paper aims to review current commercially available products that mechanically close the annulus including the AnchorKnot® suture-passing device and the Barricaid® annular closure device. Previous studies and reviews have focused mainly on a biomimetic biomaterials approach and have described some mechanical and biological requirements for an active annular repair/regeneration strategy but are still far away from clinical implementation. Therefore, in this paper we aim to create a design specification for a mechanical annular closure strategy by identifying the most important mechanical and biological design parameters, including consideration of material selection, preclinical testing requirements, and requirements for clinical implementation.

Laser Reconstruction of Spinal Discs Experiments and Clinic

Degenerative disease of the intervertebral discs (DDD) is currently a serious problem facing the world community. The surgical methods and conservative therapy used today, unfortunately, do not stop the pathological process, but serve as a palliative method that temporarily relieves pain and improves the patient’s quality of life. Therefore, at present, there is an active search for new methods of treating DDD. Among new techniques of treatment, biological methods, and minimally invasive surgery, including the use of laser radiation, which, depending on the laser parameters, can cause ablative or modifying effects on the disc tissue, have acquired considerable interest. Here, we analyze a new approach to solving the DDD problem: laser tissue modification. This review of publications is focused on the studies of the physicochemical foundations and clinical applications of a new method of laser reconstruction of intervertebral discs. Thermomechanical action of laser radiation modifies tissue and leads to its regeneration as well as to a long-term restoration of disc functions, elimination of pain and the return of patients to normal life.

Computational comparison of three different cage porosities in posterior lumbar interbody fusion with porous cage

Porous interbody cages, manufactured using additive laser melting technology, have recently been used in lumbar fusion surgery. The major advantage of a porous cage is the presence of space inside the cage for bone ingrowth. However, the biomechanical effects of different porosities on the lumbar segment with and without bone fusion (ingrowth) are still unclear. Hence, the present study aimed to compare the biomechanical responses, including the stress and range of motion (ROM) of the lumbar L3-L4 segments with three different types of porous cages along with a posterior instrument (PI) with and without bone fusion using computer simulation. A lumbar L3-L4 segment model with a PI and porous cages was used in this study. Three different porosities, namely 12.5, 41.2, and 80.84% were used. The diameter of the pores of the porous cage was uniformly set to 0.5 mm. In addition, a traditional PEEK cage was used in this study. Two different bone statuses, with and without bone fusion (ingrowth into the pores of the porous cage and the inner space of the PEEK cage), were considered. The results indicated that although the contact pressure on the bone surface reduced, the cage stress increased with increasing cage porosity. Furthermore, cage stress and contact pressure also increased in cases with bone fusion compared with those without bone fusion. The contact pressure on the bone surface with a cage porosity of 80.8% decreased by 40% (from 943.1 to 575.5 MPa), 37.7% (from 133 to 82.9 MPa), 40.4% (from 690.8 to 412 MPa), and 34.2% (from 533 to 351.1 MPa), respectively, for flexion, extension, lateral bending, and rotation, respectively, compared with that with a cage porosity of 12.5%. The rotational ROM of the PEEK cage with bone fusion was clearly larger than those of the porous cages. Porous cages have recently become popular owing to improved manufacturing technology. This study provides scientific data on the strength and weakness of porous cages with different porosities for clinical use.

TNF-α suppresses SHOX2 expression via NF-κB signaling pathway and promotes intervertebral disc degeneration and related pain in a rat model

This study was conducted to verify the relative expression patterns of SHOX2 and its regulation by tumor necrosis factor alpha (TNF-α) during the development of intervertebral disc degeneration (IVDD). A rat disc-degeneration model was subjected to disc puncture (DP) and intradiscal injections with TNF-α to determine the roles of TNF-α and SHOX2 expression in IVDD in vivo. TNF-α and SHOX2 expression patterns in different degenerative rat nucleus pulposus (NP) tissues were measured by immunohistochemistry (IHC). The effects of TNF-α on IVDD were determined by magnetic resonance imaging (MRI) and pain development of wet-dog shakes (WDS) were blinded assessment by pain-behavior testing, respectively. Changes in TNF-α on SHOX2 expression were measured by Western blot analysis and real-time reverse transcription polymerase chain reaction (RT-PCR). The roles of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) in TNF-α-mediated SHOX2 activation were studied using viral transfection, Western blot analysis, and real-time RT-PCR. In vivo, TNF-α accelerated the process of IVDD and suppressed SHOX2 expression; compared to the DP group, WDS was significantly increased in TNF-α intradiscal injection group at 2 to 6 weeks after puncture (P < .05); In NP cells, TNF-α negatively affected the IVDD-associated SHOX2 suppression. While TNF-α promotes IVDD through activation of both MAPK and NF-κB signaling, it seemed that only NF-κB signaling controlled the TNF-α-mediated SHOX2 suppression that is associated with IVDD. The results of this study indicated that TNF-α inhibits SHOX2 expression and has promoted effects on IVDD in the rat model, and these effects might be associated with through NF-κB signaling pathway and promotes IVDD and related pain in a rat model.

The effect of compressive loading rate on annulus fibrosus strength following endplate fracture

Intervertebral disc degeneration poses a considerable healthcare challenge, although the process is not well understood. Endplate fracture marks severe biomechanical compromise in a segment and may be correlated with degeneration of the disc. The purpose of this experiment was to investigate the relationship between endplate fracture velocity and damage to the annulus fibrosus. Following overnight-thawing, 27 frozen porcine cervical spines were dissected into motion segments (vertebra-disc-vertebra) and compressed until fracture at one of three loading rates (fast=15 mm/s, medium=1.5 mm/s, and slow=0.15 mm/s), or remained unfractured (control). Two annular samples were extracted and mechanically tested from each segment: 1) Bilayer samples underwent uniaxial tension to a stretch-ratio of 1.5; 2) Multilayer samples were delaminated with a 180° peel test configuration. All three rates of compression resulted in specimen fracture observed in the endplate and/or vertebra with varying degree of severity. Significant differences were detected in compressive strength and stiffness of motion segments when loaded at different rates of compression; interestingly these differences were not observed in the mechanical properties of the annulus fibrosus suggesting that at slow rates of loading, fracture of the endplate precedes destruction of the annulus fibrosus. In corroboration of these findings, gross and histological analysis reported no signs of annular disruption, strengthening assertions that annular damage did not occur.

The effects of axial loading on the morphometric and T2 characteristics of lumbar discs in relation to disc degeneration

BACKGROUND

Intervertebral disc degeneration affects the morphology, biomechanics and biochemistry of the disc. The study aimed to compare the effects of compression and traction on lumbar discs measurements in relation to degeneration.

METHODS

Thirty-five volunteers (30 (SD 11) yrs.) with and without chronic back pain rested supine 15 min before an unloaded T₂-mapping MRI, were then loaded 20 min with 50% body weight with imaging during the last 5 min, and then repeated this process under traction. For lumbar discs, height, angle, width, mean-T₂, and T₂-weighted centroid locations were calculated. A repeated measure ANCOVA and Cohen's d compared loading conditions. Relations between measurement changes between conditions and degeneration assessed by Pfirrmann ratings were examined graphically.

FINDINGS

From compression to traction, we observed significant: decrease in L1-2 mean-T₂ (Effect size = -0.35); inferior and posterior shift in L4-5 (0.4, 0.14) and L5-S1 (0.25, 0.33) T₂-weighted centroid. From unloaded to compression, we observed a significant: increase in L5-S1 width (Effect Size = 0.22); anterior shift in L1-2 T₂-weighted centroid (0.39); and L3-4 (mean 2.1°) and L4-5 (1.8°) extension angle. More degeneration was graphically related with larger changes from Compression to Traction (more superior and, anterior position of the T₂-weighted centroid, increased height, reduced extension of segmental angle) and from Unloaded to Compression larger changes in inferior displacement of the T_2-weighted centroid, decrease in height) but less anterior displacement of the centroid and less change in segmental angles.

INTERPRETATION

The largest loading responses were at lower levels, generally with more degeneration. T₂-weighted centroid locations, angle and disc height detected the largest loading response.

Effects of specific muscle activation for low back pain on activity limitation, pain, work participation, or recurrence: A systematic review

BACKGROUND

Specific muscle activation (SMA) is a commonly used treatment for people with low back pain (LBP) however there is variability in systematic reviews to date on effectiveness. This may be because of the use of eligibility criteria incongruent with original descriptions of the SMA approach.

PURPOSE

The purpose of this study was to determine the effectiveness of SMA on improving activity limitation, pain, work participation or recurrence for people with LBP.

STUDY DESIGN

Systematic review METHODS: Computer databases were searched for randomised controlled trials (RCTs) published in English up to September 6, 2019. Eligibility criteria were chosen to ensure all clinically relevant RCTs were included and trials of poorly defined or executed SMA excluded. Outcomes for activity limitation, pain, work participation or recurrence were extracted.

RESULTS

Twenty-eight RCTs were included in this review with 18 being considered high quality. GRADE quality assessment revealed low to high quality evidence that SMA was more effective than exercise, conservative medical management, multi-modal physiotherapy, placebo, advice and minimal intervention.

CONCLUSIONS

This systematic review is the first to evaluate the effectiveness of SMA in accordance with the original clinical descriptions. We found significant evidence supporting the effectiveness of SMA for the treatment of LBP. Where significant results were demonstrated, the between-group differences were in many comparisons clinically important based on contemporary definitions and an effect size of 0.5 or more. Practitioners should consider SMA as a treatment component in their patients with LBP.

Clinical features as predictors of histologically confirmed inflammation in patients with lumbar disc herniation with associated radiculopathy

Background

An understanding of the clinical features of inflammation in low back pain with or without leg symptoms may allow targeted evaluations of anti-inflammatory treatment in randomised-controlled-trials and clinical practice.

Purpose

This study evaluated the diagnostic accuracy of clinical features to predict the presence/absence of histologically confirmed inflammation in herniated disc specimens removed at surgery in patients with lumbar disc herniation and associated radiculopathy (DHR).

Study design

Cohort Study.

Methods

Disc material from patients with DHR undergoing lumbar discectomy was sampled and underwent histological/immunohistochemistry analyses. Control discs were sampled from patients undergoing surgical correction for scoliosis. Baseline assessment comprising sociodemographic factors, subjective examination, physical examination and psychosocial screening was conducted and a range of potential clinical predictors of inflammation developed based on the existing literature. Multi-variate analysis was undertaken to determine diagnostic accuracy.

Results

Forty patients with DHR and three control patients were recruited. None of the control discs had evidence of inflammation compared to 28% of patients with DHR. Predictors of the presence of histologically confirmed inflammation included back pain < 5/10, symptoms worse the next day after injury, lumbar flexion range between 0 and 30° and a positive clinical inflammation score (at least 3 of: constant symptoms, morning pain/stiffness greater than 60-min, short walking not easing symptoms and significant night symptoms). The model achieved a sensitivity of 90.9%, a specificity of 92.9%, and a predictive accuracy of 92.3%.

Conclusion

In a sample of patients with lumbar DHR a combination of clinical features predicted the presence or absence of histologically confirmed inflammation.

Clinical relevance

These clinical features may enable targeted anti-inflammatory treatment in future RCTs and in clinical practice.

Isolated Lumbar Extension Resistance Training Improves Strength, Pain, and Disability, but Not Spinal Height or Shrinkage ("Creep") in Participants with Chronic Low Back Pain

Objective. Loss of disc height is commonly associated with chronic low back pain (CLBP). Isolated lumbar extension (ILEX) exercise for the lumbar extensors is recommended to treat CLBP and is suggested such exercise might promote disc healing and regeneration. This study examined a 12-week ILEX intervention on indirect determination of disc height and shrinkage through seated stadiometry, strength, pain, and disability. Design. A quasi-experimental wait-list controlled design was used. Nine participants underwent pretesting (T1), a 12-week control period, retesting (T2), a 12-week intervention period, and finally posttesting (T3). Seated stadiometry, ILEX strength, pain, and disability were measured at each time point. Results. No significant repeated-measures effects for any seated stadiometry variables occurred. Significant improvement across the intervention period (T2 to T3) was found for strength (P <0.0001; effect size [ES] = 2.42). Change in pain was not significant for repeated effects (P = 0.064); however, ES for the intervention period (T2 to T3) was moderate (ES = -0.77). Change in disability was significant between time point T1 and T3 (P = 0.037) and ES for the intervention period (T2 to T3) was large (ES = -0.92). Pain and disability achieved minimal clinically important changes. Conclusions. This is apparently the first study to examine disc change in vivo after exercise in CLBP. Results of the present study, though supporting ILEX resistance training to improve strength, pain, and disability, did not find any effect on spinal height.

The Evolving Case Supporting Individualised Physiotherapy for Low Back Pain

Low-back pain (LBP) is one of the most burdensome health problems in the world. Guidelines recommend simple treatments such as advice that may result in suboptimal outcomes, particularly when applied to people with complex biopsychosocial barriers to recovery. Individualised physiotherapy has the potential of being more effective for people with LBP; however, there is limited evidence supporting this approach. A series of studies supporting the mechanisms underpinning and effectiveness of the Specific Treatment of Problems of the Spine (STOPS) approach to individualised physiotherapy have been published. The clinical and research implications of these findings are presented and discussed. Treatment based on the STOPS approach should also be considered as an approach to individualised physiotherapy in people with LBP.

Development and Characterization of a Novel Bipedal Standing Mouse Model of Intervertebral Disc and Facet Joint Degeneration

BACKGROUND

Intervertebral disc degeneration is a major cause of chronic low back pain, and excessive loading contributes to intervertebral disc degeneration. However, the lack of an effective bipedal in vivo animal model limits research about this condition.

QUESTIONS/PURPOSES

To evaluate the utility of a new type of bipedal standing mouse model for intervertebral disc degeneration, we asked: (1) Are there spinal degeneration changes in bipedal mice as determined by lumbar disc height, histologic features, and immunohistochemistry measures compared with control mice? (2) Are the bipedal mice comparable to aged mice for simulating the spinal degeneration caused by increased stress?

METHODS

Thirty-two 8-week-old male C57BL/6 mice were divided into experimental and control groups. Based on their hydrophobia, mice in the experimental group were placed in a limited water-containing space (5 mm deep) and were thereby induced to actively take a bipedal standing posture. This was conducted twice a day for a total of 6 hours a day, 7 days a week. Control mice were similarly placed in a limited but water-free space. Video surveillance was used to calculate the percentage of time spent in the bipedal stance for the two groups of mice. Compared with the control group, the percentage of time standing on both feet in the experimental group was higher (48% ± 5%, 95% confidence interval [CI], 42%-54% versus 95% ± 1%, 95% CI, 92%-97%; p < 0.001). Eight mice from both groups were then randomly euthanized at either 6 or 10 weeks and lumbar spine specimens (L3-L6) were collected. The lumbar disc height index (DHI%) of the two groups was compared using micro-CT measurements, and the extent of disc degeneration was assessed based on histologic staining (cartilage endplate height, disc degeneration score) and by immunohistochemistry (Col2a1,CollagenX, matrix metalloprotease-13 [MMP-13], osteocalcin [OCN]). In addition, the histopathologic features of spinal degeneration were compared with 12- and 18-month-old mice. A p value < 0.05 indicated a significant difference.

RESULTS

Lumbar disc degeneration was aggravated after 10 weeks with the DHI% decreasing (5.0% ± 0.4%; 95% CI, 4.6%-5.5% versus 4.6 ± 0.3%; 95% CI, 4.3%-4.9%; p = 0.011). Histologically, the cartilage endplate height of the experimental group was decreased compared with the control group (30 ± 6 μm; 95% CI, 24-37 μm versus 70 ± 7 μm; 95% CI, 63-79 μm; p < 0.001), and the disc degeneration score was increased (5 ± 1; 95% CI, 4-6 versus 1 ± 1; 95% CI, 0-2; p < 0.001). Expression of Col2a1, vimentin, and aggrecan in the experimental group was decreased compared with the control group, whereas the expressions of collagen X (60% ± 2%; 95% CI, 55%-66% versus 19% ± 3%; 95% CI, 17%-24%; p < 0.001), MMP-13 (54% ± 8%; 95% CI, 49%-61% versus 1% ± 1%; 95% CI, 1%-2%; p < 0.001), and OCN (41% ± 3%; 95% CI, 34%-49% versus 5% ± 1%; 95% CI, 2%-7%, p < 0.001) were increased. The spine degeneration caused by this model was primarily manifested in the degeneration of the annulus fibrosus and facet joints compared with aged mice, whereas the degree of degeneration in the nucleus pulposus tissue and cartilage endplates was mild.

CONCLUSIONS

We believe we have established a noninvasive and effective in vivo bipedal mouse model for studying disc degeneration and biologic signal transduction comparable to that seen in intervertebral disc degeneration.

CLINICAL RELEVANCE

This in vivo mouse model of intervertebral disc degeneration can simulate the pathogenesis of spinal degeneration caused by increased stress and this can be used to study questions such as disc herniation in young adults.

A Novel Treatment Combination for Failed Back Surgery Syndrome, With a 41-Month Follow-Up: A Retrospective Case Report

Objective

The purpose of this retrospective case report was to describe chiropractic management of a patient with failed back surgery syndrome.

Clinical Features

A 45-year-old woman presented 2 years after L4-L5 and L5-S1 fusion surgery with low back and sciatic pain. Her physical exam included a positive straight leg raise and diminished lower-extremity reflexes and muscle strength. The patient's magnetic resonance imaging showed right disc bulging and annular tearing at L2-L3 and L3-L4 disc bulging with foraminal impingement.

Intervention and Outcome

A total of 52 treatments were provided over 28 weeks consisting of multidirectional functional decompression (FD) unweighted gait training, core exercises while in FD, strengthening exercises on a vibration platform, and supine spinal FD with vibration and chiropractic spinal manipulative therapy. Over the course of treatment, the patient noted gradual improvement in function (Oswestry Disability Index) and pain (Numeric Rating Scale), with a reduction in pain medications. Follow-up of 41 months posttreatment revealed an Oswestry Disability Index score of 0 and Numeric Rating Scale score of 0, and the patient no longer was using any pain medication.

Conclusion

After a course of care, the patient in this study reported resolution of symptoms, decrease in pain medications, and improvement of function.

Materials for the Spine: Anatomy, Problems, and Solutions

Disc degeneration affects 12% to 35% of a given population, based on genetics, age, gender, and other environmental factors, and usually occurs in the lumbar spine due to heavier loads and more strenuous motions. Degeneration of the extracellular matrix (ECM) within reduces mechanical integrity, shock absorption, and swelling capabilities of the intervertebral disc. When severe enough, the disc can bulge and eventually herniate, leading to pressure build up on the spinal cord. This can cause immense lower back pain in individuals, leading to total medical costs exceeding $100 billion. Current treatment options include both invasive and noninvasive methods, with spinal fusion surgery and total disc replacement (TDR) being the most common invasive procedures. Although these treatments cause pain relief for the majority of patients, multiple challenges arise for each. Therefore, newer tissue engineering methods are being researched to solve the ever-growing problem. This review spans the anatomy of the spine, with an emphasis on the functions and biological aspects of the intervertebral discs, as well as the problems, associated solutions, and future research in the field.

Thixotropic PVA hydrogel enclosing a hydrophilic PVP core as nucleus pulposus substitute

A thixotropic polyvinyl alcohol (PVA) hydrogel, containing a hydrophilic poly-vinyl pyrrolidone (PVP) core, was obtained in order to develop a preformed 3D network able to maintain injectability. PVA was mixed with PVP in two different molar ratios (1:1 and 1:3) and chemically cross-linked using trisodium trimetaphosphate (STMP), which is able to react only with PVA component. A combination of Time of Flight- Secondary Ion Mass Spectrometry (ToF-SIMS), elemental analysis and UV spectroscopy permitted to determine both the cross-linking arm length and the crosslinking degree. Hydrogels were characterized in terms of swelling pressurization, rheological and mechanical behaviour. In particular, the viscoelastic behaviour of the hydrogel was analysed in shear and compression stress under dynamic conditions and compared with the performance of healthy human nucleus pulposus. In conclusion, the study demonstrated that the scaffold obtained mixing PVA and PVP in a molar ratio 1:1 can be considered a promising material to be utilised in the replacement of nucleus pulposus.

Finite element analysis of the influence of three-joint spinal complex on the change of the intervertebral disc bulge and height

This study evaluated the changes of height and bulging occurring in individual layers of the annulus fibrosus of the intervertebral disc for 3 load scenarios (axial compression, flexion, and extension). The numerical model of a single motion segment of the thoracic spine was analysed for 2 different configurations, ie, for the model of a physiological segment and a segment with the posterior column removed. In the physiological segment, all annulus fibrosus layers decrease in height regardless of the applied load, bulging outside the intervertebral disc. Removal of the posterior column increases mobility and disrupts the load transfer system, with the lamellae bulging into the intervertebral disc.

Aberrantly expressed messenger RNAs and long noncoding RNAs in degenerative nucleus pulposus cells co-cultured with adipose-derived mesenchymal stem cells

Background

Stem cell therapy is considered as a promising alternative to treat intervertebral disc degeneration (IDD). Extensive work had been done on identifying and comparing different types of candidate stem cells, both in vivo and in vitro. However, few studies have shed light on degenerative nucleus pulposus cells (NPCs), especially their biological behavior under the influence of exogenous stem cells, specifically the gene expression and regulation pattern. In the present study, we aimed to determine messenger RNAs (mRNAs) and long non-coding RNAs (lncRNAs), which are differentially expressed during the co-culturing process with adipose-derived mesenchymal stem cells (ASCs) and to explore the involved signaling pathways and the regulatory networks.

Methods

We compared degenerative NPCs co-cultured with ASCs with those cultured solely using lncRNA-mRNA microarray analysis. Based on these data, we investigated the significantly regulated signaling pathways based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database. Moreover, 23 micro RNAs (miRNAs), which were demonstrated to be involved in IDD were chosen; we investigated their theoretic regulatory importance associated with our microarray data.

Results

We found 632 lncRNAs and 1682 mRNAs were differentially expressed out of a total of 40,716 probes. We then confirmed the microarray data by real-time PCR. Furthermore, we demonstrated 197 upregulated, and 373 downregulated Gene Ontology terms and 176 significantly enriched pathways, such as the mitogen-activated protein kinase (MAPK) pathway. Also, a signal-net was constructed to reveal the interplay among differentially expressed genes. Meanwhile, a mRNA-lncRNA co-expression network was constructed for the significantly changed mRNAs and lncRNAs. Also, the competing endogenous RNA (ceRNA) network was built.

Conclusion

Our results present the first comprehensive identification of differentially expressed lncRNAs and mRNAs of degenerative NPCs, altered by co-culturing with ASCs, and outline the gene expression regulation pattern. These may provide valuable information for better understanding of stem cell therapy and potential candidate biomarkers for IDD treatment.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1677-x) contains supplementary material, which is available to authorized users.

TSG-6 secreted by bone marrow mesenchymal stem cells attenuates intervertebral disc degeneration by inhibiting the TLR2/NF-κB signaling pathway

Inflammation has been correlated with intervertebral disc degeneration (IDD). Recent evidence suggests that TNF-α-stimulated gene 6 protein (TSG-6) secreted by bone marrow mesenchymal stem cells (BMSCs) displays a remarkable ability to inhibit inflammatory processes in a variety of diseases. However, it is unknown whether BMSCs exert their therapeutic effect against IDD by secreting TSG-6. Here we investigated the effects of BMSCs and TSG-6 on IDD and explored the possible underlying mechanisms in vitro and in vivo. We found that BMSCs and TSG-6 reduced the expression of MMP-3 and MMP-13, and increased the expression of collagen II and aggrecan in the IL-1β-treated nucleus pulposus cells (NPCs), but the protective effects of BMSCs and TSG-6 were attenuated when TSG-6 expression was silenced. We also found that the activation of the TLR2/NF-κB pathway was inhibited by BMSCs and TSG-6. The levels of IL-6 and TNF-α in the degenerated NPCs were reduced and the proliferation of IL-1β-treated NPCs was increased in the presence of BMSCs and TSG-6. Furthermore, in vivo experiments showed that BMSCs and TSG-6 restored the MRI T2-weighted signal intensity and increased collagen II and aggrecan expression in the degenerated nucleus pulposus (NP) tissues. Finally, our results showed that BMSCs and TSG-6 downregulated the TLR2/NF-κB signaling and reduced the expression of MMPs and inflammatory cytokines in the degenerated NP tissues. The present study is the first to demonstrate the involvement of TLR2/NF-κB pathway in the potential anti-IDD therapeutic effect of TSG-6, and the results provide new insight into the beneficial effect of BMSCs in the treatment of IDD.

Development of a Multivariate Prognostic Model for Pain and Activity Limitation in People With Low Back Disorders Receiving Physiotherapy

OBJECTIVE

To identify predictors for back pain, leg pain, and activity limitation in patients with early persistent low back disorders (LBDs).

DESIGN

Prospective inception cohort study.

SETTING

Primary care private physiotherapy clinics in Melbourne, Australia.

PARTICIPANTS

Individuals (N=300) aged 18-65 years with low back and/or referred leg pain of ≥6 weeks and ≤6 months duration.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Numeric rating scales for back pain and leg pain as well as the Oswestry Disability Scale.

RESULTS

Prognostic factors included sociodemographics, treatment related factors, subjective/physical examination, subgrouping factors, and standardized questionnaires. Univariate analysis followed by generalized estimating equations were used to develop a multivariate prognostic model for back pain, leg pain, and activity limitation. Fifty-eight prognostic factors progressed to the multivariate stage where 15 showed significant (P<.05) associations with at least 1 of the 3 outcomes. There were 5 indicators of positive outcome (2 types of LBD subgroups, paresthesia below waist, walking as an easing factor, and low transversus abdominis tone) and 10 indicators of negative outcome (both parents born overseas, deep leg symptoms, longer sick leave duration, high multifidus tone, clinically determined inflammation, higher back and leg pain severity, lower lifting capacity, lower work capacity, and higher pain drawing percentage coverage). The preliminary model identifying predictors of LBDs explained up to 37% of the variance in outcome.

CONCLUSIONS

This study evaluated a comprehensive range of prognostic factors reflective of both the biomedical and psychosocial domains of LBDs. The preliminary multivariate model requires further validation before being considered for clinical use.

Halofuginone attenuates intervertebral discs degeneration by suppressing collagen I production and inactivating TGFβ and NF-кB pathway

Most low back pain is caused by intervertebral discs (IVD) degeneration, a disease that prevalence is increasing with age. Halofuginone, an analog of ferbrifugine isolated from plant Dichroa febrifuga, has drawn much attention in recent years for the wide range of bioactivities in malaria, cancer, fibrotic and autoimmune diseases. In this study, we evaluated the benefit effects of halofuginone in IVD degeneration treatment in a validated rabbit puncture model. Halofuginone treatment could attenuate disc degeneration by suppressing the decrease of discs height and nucleus pulposus signal strength. Besides, halofuginone treatment could suppress mRNA and protein expression of collagen I in nucleus pulposus. This might possibly due to the inactivation of transform growth factor-β (TGFβ) signal pathway by down-regulating p-Samd3 and up-regulating inhibitory Smad7. Then, we evaluated the effects of halofuginone treatment on nuclear factor of kappa B (NF-κB) signal pathway and its downstream pro-inflammatory cytokines. The level of p-p65 and p-IκBα was down-regulated in halofuginone treated group, indicating the inactivation of NF-κB signal pathway. The mRNA expression of interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), interleukin 6 (IL-6) and interleukin 8 (IL-8) was decreased in nucleus pulposus too, indicating the down-regulation of pro-inflammatory cytokines. In conclusion, halofuginone treatment could attenuate IVD degeneration and this was possibly due to suppressing of collagen I production and inactivation of TGFβ and NF-κB signal pathway in nucleus pulposus of degenerated discs. These results suggest that halofuginone has the potential for IVD degeneration treatment, but more research is needed to validate this.

Effects of Training and Overtraining on Intervertebral Disc Proteoglycans

STUDY DESIGN

Animal experimental study.

OBJECTIVE

Evaluate the effect of physical activity and overtraining condition on glycosaminoglycan concentration on the intervertebral disc (IVD) using a rat running model.

SUMMARY OF BACKGROUND DATA

Some guidelines recommend the implementation of a physical exercise program as treatment for low back pain; however, cyclic loading impact on the health of the IVD and whether there is a dose-response relationship is still incompletely understood.

METHODS

Thirty-two rats ages 8 weeks were divided into four groups with eight animals each. The first 8 weeks were the adaptive phase, the overtraining phase was from the ninth to the eleventh week, which consisted of increasing the number of daily training sessions from 1 to 4 and the recovery phase was represented by the 12th and 13th weeks without training. Control group 1 (CG1) did not undergo any kind of training. Control group 2 (CG2) completed just the adaptive phase. Overtraining group 1 (OT1) completed the overtraining phase. Overtraining group 2 (OT2) completed the recovery phase. Running performance tests were used to assess the "overtraining" status of the animals. IVD glycosaminoglycans were extracted and quantified, and identified by electrophoresis.

RESULTS

Glycosaminoglycans showed a distribution between chondroitin sulfate and dermatan sulfate. Glycosaminoglycans quantification showed decreasing concentration at the following order: OT1 > CG2 > OT2 > CG1. Increased expression of dermatan sulfate was verified at the groups submitted to any training.

CONCLUSION

Overtraining condition, as assessed by muscle and cardiovascular endurance did not lessen glycosaminoglycan concentration in the IVD. In fact, physical exercise increased glycosaminoglycan concentration in the IVD in proportion to the training load, even at overtraining condition, returning to normal levels after the recovery phase and glycosaminoglycan production is a reversible acute positive response for mechanical stimulation of the IVD.

LEVEL OF EVIDENCE

N/A.

Age-related differences in the response of the L5-S1 intervertebral disc to spinal traction

BACKGROUND

Lumbar traction is a common treatment for low back pain; however its mechanisms of action are poorly understood. It has been hypothesized that a key effect of lumbar traction is its capacity to influence fluid movement within the intervertebral disc (IVD).

OBJECTIVES

To determine differences in the apparent diffusion coefficient (ADC) obtained with lumbar diffusion-weighted imaging (DWI) of the L5-S1 IVD before, and during, the application of lumbar traction.

DESIGN

Case series, repeated measures.

METHODS

A static traction load of ∼50% of body-weight was applied to the low back using a novel "MRI-safe" apparatus. DWI of the lumbar spine was performed prior to, and during the application of the traction load.

RESULTS

Participants were currently asymptomatic and included a young adult group (n = 18) and a middle-aged group (n = 15). The young adult group had a non-significant 2.2% increase in ADC (mean change = 0.03 × 10^-3 mm²/s, SD = 0.24, 95% CI = -0.09, 0.15). The ADC for the middle-aged group significantly increased by 20% (mean change of 0.18 × 10^-3 mm²/s, SD = 0.19; 95% CI = 0.07, 0.28; p = 0.003; effect size = 0.95). There was an inverse relationship between the ADC obtained before traction and the percent increase in ADC that was measured during traction.

CONCLUSION

Static traction was associated with an increase in diffusion of water within the L5-S1 IVDs of middle-age individuals, but not in young adults, suggesting age-related differences in the diffusion response. Further study is needed to assess the relationship between these findings and the symptoms of back pain.

LEVEL OF EVIDENCE

4.

Physiological effects of physical therapy interventions on lumbar intervertebral discs: A systematic review

BACKGROUND CONTEXT

The use of physical therapy has been recommended in the treatment of low back pain based on primarily mechanical and neurophysiological effects. Recent studies have measured the physiological effects of physical therapy interventions, including manual therapy and traction, on the intervertebral discs (IVD), and these findings may have implications for the long-term management or even prevention of low back pain.

PURPOSE

The objective of this systematic review is to investigate the literature regarding possible physiological effects of physical therapy interventions on the intervertebral disc (IVD).

STUDY DESIGN

Systematic Review.

METHODS

A literature search of published articles through December 2014 resulted in the retrieval of 8 clinical studies assessing the influence of physical therapy interventions on the physiology of the IVD.

RESULTS

Three studies, including two using animal models, investigated the effects of 30-minute intermittent traction on disc height. One in vivo animal study and two studies using human subjects assessed changes of disc height associated with static traction. Three studies investigated the effects of lumbar spine manipulation and mobilization on changes in water diffusion within the IVD. All studies confirmed, either directly or indirectly, that their respective intervention influenced disc physiology primarily through water flow.

CONCLUSION

Physical therapy interventions may have an effect on the physiology of the IVD, primarily through water diffusion and molecular transport, which are important for the health of the IVD.

Biomechanical Effects of Human Lumbar Discography: In Vitro Experiments and Their Finite Element Validation

STUDY DESIGN

An experimental and computational finite element analysis of human lumbar spine discography and its resulting effects on disk biomechanics.

OBJECTIVE

To characterize the changes in stress and displacement of the human lumbar spine disks after puncture due to discography.

SUMMARY OF BACKGROUND DATA

Discography of the intervertebral disk (IVD) may be used to diagnose pathology of the disk and determine whether it may be a source for chronic back pain. It has recently been suggested that discography may lead to IVD degeneration, and has been a cause of controversy among spine care physicians.

MATERIALS AND METHODS

Both in vivo experiment using cadaveric specimens and a finite element model of the same L3-L5 lumbar spine was developed using computed tomography scans. Discography was simulated in the model as an area in the disk affected by needle puncture. The material properties in the nucleus pulposus were adjusted to match experimental data both before and after puncture.

RESULTS

Puncture of the IVD leads to increased deformation and increased stresses in the annulus fibrosis region of the disk. Pressure in the nucleus pulposus was found to decrease after puncture. Experimental and computational results correlated well.

CONCLUSIONS

Puncturing the IVD changes disk biomechanics and hence may lead to progressive spine degenerations in particular in the punctured disks.

A regenerative approach towards recovering the mechanical properties of degenerated intervertebral discs: Genipin and platelet-rich plasma therapies

Degenerative disc disease, associated with discrete structural changes in the peripheral annulus and vertebral endplate, is one of the most common pathological triggers of acute and chronic low back pain, significantly depreciating an individual's quality of life and instigating huge socioeconomic costs. Novel emerging therapeutic techniques are hence of great interest to both research and clinical communities alike. Exogenous crosslinking, such as Genipin, and platelet-rich plasma therapies have been recently demonstrated encouraging results for the repair and regeneration of degenerated discs, but there remains a knowledge gap regarding the quantitative degree of effectiveness and particular influence on the mechanical properties of the disc. This study aimed to investigate and quantify the material properties of intact (N = 8), trypsin-denatured (N = 8), Genipin-treated (N = 8), and platelet-rich plasma-treated (N = 8) discs in 32 porcine thoracic motion segments. A poroelastic finite element model was used to describe the mechanical properties during different treatments, while a meta-model analytical approach was used in combination with ex vivo experiments to extract the poroelastic material properties. The results revealed that both Genipin and platelet-rich plasma are able to recover the mechanical properties of denatured discs, thereby affording promising therapeutic modalities. However, platelet-rich plasma-treated discs fared slightly, but not significantly, better than Genipin in terms of recovering the glycosaminoglycans content, an essential building block for healthy discs. In addition to investigating these particular degenerative disc disease therapies, this study provides a systematic methodology for quantifying the detailed poroelastic mechanical properties of intervertebral disc.

Evaluating the low back biomechanics of three different office workstations: Seated, standing, and perching

The objective of this study was to evaluate how different workstations may influence physical behavior in office work through motion and how that may affect spinal loads and discomfort. Twenty subjects performed a typing task in three different workstations (seated, standing, and perching) for one hour each. Measures of postural transitions, spinal loads, discomfort, and task performance were assessed in order to understand the effects of workstation interaction over time. Results indicated that standing had the most amount of motion (6-8 shifts/min), followed by perching (3-7 shifts/min), and then seating (<1 shift/min). Standing had the highest reports of discomfort and seating the least. However, spinal loads were highest in A/P shear during standing (190N posterior shear, 407N anterior shear) compared to perching (65N posterior shear, 288N anterior shear) and seating (106N posterior shear, 287 anterior shear). These loads are below the risk threshold for shear, but may still elicit a cumulative response. Perching may induce motion through supported mobility in the perching stool, whereas standing motion may be due to postural discomfort. Office workstation designs incorporating supported movement may represent a reasonable trade-off in the costs-benefits between seating and standing.

Catabolic effects of endothelial cell-derived microparticles on disc cells: Implications in intervertebral disc neovascularization and degeneration

Neovascularization of intervertebral discs, a phenomenon considered pathological since normal discs are primarily avascular structures, occurs most frequently in annulus fibrosus (AF) of degenerated discs. Endothelial cells (ECs) are involved in this process, but the mechanism of the interaction between AF and endothelial cells is unclear. In this study, we evaluated the effects on matrix catabolic activity of AF cells by the extracellular endothelial microparticles (EMPs) and soluble protein factors (SUP fraction) produced from ECs. Passage 1 human AF cells grown in monolayer cultures were treated for 72 h with 250 µg of EMPs or SUP fraction isolated from culture of the microvascular endothelial cell line, HEMC-I. Live-cell imaging revealed uptake of EMPs by AF cells. RT-PCR analysis demonstrated increased mRNA expression of MMP-1 (50.3-fold), MMP-3 (4.5-fold) and MMP-13 (5.5-fold) in AF cell cultures treated with EMPs compared to untreated control. Western analysis also demonstrated increased MMP protein expression in EMP-treated AF cells. AF cells treated with the SUP fraction also exhibited a dramatic increase in MMP mRNA and protein expression. Increased MMP expression is primarily due to EMP or SUP stimulation of AF cells since EMPs or SUP fraction alone contained negligible amount of MMPs. Interestingly, MMP activity was elevated in AF cell cultures treated with EMPs but not with SUP. This study revealed enhanced matrix catabolism as a molecular consequence of action of ECs on AF cells via EMPs, which might be expected during neo-angiogenesis of degenerating disc. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1466-1474, 2016.

Effects of individualised directional preference management versus advice for reducible discogenic pain: A pre-planned secondary analysis of a randomised controlled trial

BACKGROUND

Low back disorders are prevalent and directional preference management is a common treatment with mixed evidence for effectiveness.

OBJECTIVES

To determine the effectiveness of individualised directional preference management plus guideline-based advice versus advice alone in participants with reducible discogenic pain of 6-week to 6-month duration.

DESIGN

Pre-planned secondary analysis of a multicentre, parallel group randomised controlled trial.

METHODS

Participants were randomly allocated to receive a 10-week physiotherapy program of 10-sessions of individualised directional preference management plus guideline-based advice (n = 40) or 2-sessions of advice alone (n = 38). Primary outcomes were back pain, leg pain and activity limitation. Outcomes were taken at baseline and 5, 10, 26, and 52-weeks.

RESULTS

Between-group differences significantly favoured directional preference management compared with advice for back pain at 5-weeks (1.28; 95% CI 0.34-2.23) and 10-weeks (1.45; 95% CI 0.51-2.40), and leg pain at 10-weeks (1.21; 95% CI 0.04-2.39). These short-term differences were not maintained. There were no significant differences between-groups for activity limitation. Secondary outcomes and responder analyses favoured directional preference management suggesting between-group differences were clinically important.

CONCLUSIONS

In people with reducible discogenic pain, individualised directional preference management plus guideline-based advice resulted in significant and rapid improvement in short-term back and leg pain compared with advice alone. These effects were not maintained at long-term and there were no differences in activity limitation. Individualised directional preference management could be considered for patients with reducible discogenic pain seeking rapid pain relief however further research is indicated.

Determining the reliability of a custom built seated stadiometry set-up for measuring spinal height in participants with chronic low back pain

Indirect measurement of disc hydration can be obtained through measures of spinal height using stadiometry. However, specialised stadiometers for this are often custom-built and expensive. Generic wall-mounted stadiometers alternatively are common in clinics and laboratories. This study examined the reliability of a custom set-up utilising a wall-mounted stadiometer for measurement of spinal height using custom built wall mounted postural rods. Twelve participants with non-specific chronic low back pain (CLBP; females n = 5, males n = 7) underwent measurement of spinal height on three separate consecutive days at the same time of day where 10 measurements were taken at 20 s intervals. Comparisons were made using repeated measures analysis of variance for 'trial' and 'gender'. There were no significant effects by trial or interaction effects of trial x gender. Intra-individual absolute standard error of measurement (SEM) was calculated for spinal height using the first of the 10 measures, the average of 10 measures, the total shrinkage, and the rate of shrinkage across the 10 measures examined as the slope of the curve when a linear regression was fitted. SEMs were 3.1 mm, 2.8 mm, 2.6 mm and 0.212, respectively. Absence of significant differences between trials and the reported SEMs suggests this custom set-up for measuring spinal height changes is suitable use as an outcome measure in either research or clinical practice in participants with CLBP.

Can specific loading through exercise impart healing or regeneration of the intervertebral disc?

BACKGROUND CONTEXT

Low back pain (LBP) is highly prevalent and presents an enormous cost both through direct health care and indirectly through significant work and production loss. Low back pain is acknowledged widely to be a multifactorial pathology with a variety of symptoms, dysfunctions, and a number of possible sources of pain. One source that has been suspected and evidenced for some time is the intervertebral disc. Some degree of disc degeneration is a physiologic process associated with aging, however, more severe degeneration and/or structural abnormality may be indicative of a pathologic process or injury and is more commonly present in those suffering from LBP. Much like other tissues (ie, muscle, bone, etc.), it has been suspected that there exists an optimal loading strategy to promote the health of the disc. Exercise is often prescribed for LBP and effectively reduces pain and disability. However, whether specific loading through exercise might plausibly heal or regenerate the intervertebral discs is unknown.

PURPOSE

To examine the effects of loading on regenerative processes in the intervertebral disc and consider the potential for specific exercise to apply loading to the lumbar spine to produce these effects.

STUDY DESIGN

A brief narrative literature review.

METHODS

Studies examining the effects of loading on the intervertebral discs were reviewed to examine the plausibility of using loading through exercise to induce regeneration or healing of the intervertebral disc.

RESULTS

Research from animal model studies suggests the existence of a dose-response relationship between loading and regenerative processes. Although high loading at high volumes and frequencies might accelerate degeneration or produce disc injury, high loading, yet of low volume and at low frequency appears to induce potentially regenerative mechanisms, including improvements in disc proteoglycan content, matrix gene expression, rate of cell apoptosis, and improved fluid flow and solute transport.

CONCLUSIONS

Research suggests a dose-response relationship between loading and disc regenerative processes and that the loading pattern typically used in the lumbar extension resistance exercise interventions (high load, low volume, and low frequency) might impart healing or regeneration of the intervertebral discs. Future research should examine an exercise intervention with in vivo measurement of changes in disc condition. This may provide further evidence for the "black box" of treatment mechanisms associated with exercise interventions.

Inflammatory Kinetics and Efficacy of Anti-inflammatory Treatments on Human Nucleus Pulposus Cells

STUDY DESIGN

Human nucleus pulposus (NP) cell culture study investigating response to tumor necrosis factor-α (TNFα), effectiveness of clinically available anti-inflammatory drugs, and interactions between proinflammatory cytokines.

OBJECTIVE

To characterize the kinetic response of proinflammatory cytokines released by human NP cells to TNFα stimulation and the effectiveness of multiple anti-inflammatories with 3 substudies: Timecourse, Same-time blocking, Delayed blocking.

SUMMARY OF BACKGROUND DATA

Chronic inflammation is a key component of painful intervertebral disc degeneration. Improved efficacy of anti-inflammatories requires better understanding of how quickly NP cells produce proinflammatory cytokines and which proinflammatory mediators are most therapeutically advantageous to target.

METHODS

Degenerated human NP cells (n = 10) were cultured in alginate with or without TNFα (10 ng/mL). Cells were incubated with 1 of 4 anti-inflammatories (anti-IL-6 receptor/atlizumab, IL-1 receptor anatagonist, anti-TNFα/infliximab and sodium pentosan polysulfate/PPS) in 2 blocking-studies designed to determine how intervention timing influences drug efficacy. Cell viability, protein, and gene expression for IL-1β, IL-6, and IL-8 were assessed.

RESULTS

Timecourse: TNFα substantially increased the amount of IL-6, IL-8, and IL-1β, with IL-1β and IL-8 reaching equilibrium within ∼72 hours (IL-1β: 111 ± 40 pg/mL, IL-8: 8478 ± 957 pg/mL), and IL-6 not reaching steady state after 144 hours (1570 ± 435 pg/mL). Anti-TNFα treatment was most effective at reducing the expression of all cytokines measured when added at the same time as TNFα stimulation. Similar trends were observed when drugs were added 72 hours after TNFα stimulation, however, no anti-inflammatories significantly reduced cytokine levels compared with TNF control.

CONCLUSION

IL-1β, IL-6, and IL-8 were expressed at different rates and magnitudes suggesting different roles for these cytokines in disease. Autocrine signaling of IL-6 or IL-1β did not contribute to the expression of any proinflammatory cytokines measured in this study. Anti-inflammatory treatments were most effective when applied early in the inflammatory process, when targeting the source of the inflammation.

LEVEL OF EVIDENCE

N/A.

Expression of matrix factors in the process of neovascularization of intervertebral disc

<sec><title>OBJECTIVE:</title><p> To investigate the effects of proteins products of endothelial cells (ECs) on the annulus fibrosus (AF) cell metabolism in an in vitro culture.</p></sec><sec><title>METHODS:</title><p>Human AF cells were expanded in monolayer cultures and treated with proteins from the medium of cell line HMEC-1 (Human Microvascular Endothelial Cells) (125µg/ml). After 72h of treatment RNA was isolated from AF cells for analysis of gene expression and the culture medium was collected for protein expression analysis.</p></sec><sec><title>RESULTS:</title><p> The qRT-PCR analysis demonstrated increased gene expression of matrix metalloproteinases (MMPs) in AF cells treated with protein products of endothelial cells compared with cells from control group of AF cells: MMP-1 243.10 times (p<0.05), MMP-2 1.37 time (p<0.05), MMP-3 39.83 times (p<0.05) and MMP-13 5.70 times (p<0.05). In contrast, tissue inhibitors of metalloproteinases (TIMPs) were suppressed; TIMP-2 (0.55 time) (p<0.05) and TIMP-3 (0.60 time) (p<0.05) in the exposed groups. The expression of aggrecan gene (0.83 time) (p<0.05), an important extracellular matrix component, was also reduced. MMP-1 and MMP-3 detection was performed, confirming the results of PCR by Western Blot technique.</p></sec><sec><title>CONCLUSIONS:</title><p> In this study, we observed that the proteins produced by ECs induced the MMPs expression and suppressed the TIMPs as well as the aggrecan in primary cells of the human intervertebral disc, targeting the development of potential treatments for intervertebral disc degeneration and associated discogenic pain.</p></sec>

Severity and pattern of post-traumatic intervertebral disc degeneration depend on the type of injury

BACKGROUND CONTEXT

The burst fracture of a vertebra is the result of a complex loading procedure and is often associated with intervertebral disc (IVD) degeneration. Likewise, the presumed etiologies are (i) the structural perturbation of the IVD/end plate, (ii) the impact of loading energy alone, and (iii) the depressurization of the nucleus pulposus.

PURPOSE

To describe the pathogenesis of post-traumatic disc degeneration (DD) by comparing the severity and patterns of degeneration with different injury models.

STUDY DESIGN

New data from an in vitro organ culture study are compared with the previous work on the same model system.

METHODS

To investigate in detail the contribution of each factor (i-iii) to DD, we extended our previous work to compare three different segmental trauma processes in a rabbit full-organ in vitro model: burst fracture (Group A, etiologies i-iii), equienergetic loading without a fracture (Group B, ii), and endplate puncturing (Group C, iii). DD markers (apoptosis, necrosis, matrix remodeling, inflammation) were monitored up to 28 days posttrauma. Gene transcription data were subjected to principal component analysis and agglomerative hierarchical clustering to identify and compare pathologic patterns.

RESULTS

Only Group A showed the full profile of DD: reduced glycosaminoglycan content, increased caspase-3/7 and lactate dehydrogenase (LDH) activity, and elevated messenger RNA of catabolic (matrix metalloproteinase-1, -3, -13) and proinflammatory (tumor necrosis factor-alpha, interleukin [IL]-6, IL-8, and monocyte chemotactic protein-1) genes. In Group B, only catabolic and proinflammatory genes were slightly upregulated. In Group C, LDH but not caspase-3/7 activity was increased. Catabolic and proinflammatory genes were upregulated, although less compared with Group A. Principal component analysis revealed different transcription patterns for Group C.

CONCLUSIONS

The structural perturbation of the end plate/IVD, but not the loading energy or nuclear depressurization, promotes DD. In addition, end-plate puncturing triggers a different pathogenesis, consistent with a more continuous matrix remodeling process.

Annulus fibrosus cell characteristics are a potential source of intervertebral disc pathogenesis

In the end stage of intervertebral disc degeneration, cartilage, bone, endothelial cells, and neurons appear in association with the worsening condition. The origin of the abnormal cells is not clear. This study investigated the properties of progenitor cells in the annulus fibrosus (AF) using one in vitro and two in vivo models. Cultivation of rabbit AF cells with chondrogenic media significantly increased expressions of collagen and aggrecan. Upon exposure to osteogenic conditions, the cultures showed increased mineralization and expression of osteopontin, runx2, and bmp2 genes. Two models were used in the in vivo subcutaneous implantation experiments: 1) rabbit AF tissue in a demineralized bone matrix (DBM) cylinder (DBM/AF), and, 2) rat intact and needle punctured lumbar discs. Bone formation in the AF tissue was detected and hypertrophic chondrocytes and osteoblasts were present 1 month after implantation of the DBM/AF to nude mice. In addition to collagen I and II, immunostaining shows collagen X and osteocalcin expression in DBM/AF specimens 4 months after implantation. Similar changes were detected in the injured discs. Almost the entire needle punctured disc had ossified at 6 months. The results suggest that AF cells have characteristics of progenitor cells and, under appropriate stimuli, are capable of differentiating into chondrocytes and osteoblasts in vitro as well as in vivo. Importantly, these cells may be a target for biological treatment of disc degeneration.

A reappraisal of the deconditioning hypothesis in low back pain: review of evidence from a triumvirate of research methods on specific lumbar extensor deconditioning

OBJECTIVE

'Disuse' and 'Deconditioning' in relation to low back pain (LBP) are terms often used interchangeably. Discussions of 'disuse' refer to general physical inactivity, which evidence suggests does not differ between symptomatic and asymptomatic persons. 'Deconditioning' refers to a decrease in function, commonly both cardiovascular/aerobic fitness and muscular strength/endurance, again noting little difference. However, examination of decreased function relating specifically to lumbar extensor musculature deconditioning has yet to be examined, corroborating all possible methods. Thus, this review attempts to reappraise the deconditioning hypothesis in LBP, specifically considering lumbar extensor deconditioning.

METHODS

A literature review was conducted examining both cross-sectional and prospective data on specific lumbar extensor deconditioning and LBP. A narrative approach and 'snowballing' style literature search was used involving initial use of PubMed and Google Scholar databases searching up to December 2012. Included were studies utilizing the following three research methods, allowing specific induction of the role of such deconditioning; (1) strength/endurance testing of the isolated lumbar extensor musculature, (2) imaging and histochemical examination of the lumbar extensor musculature, and (3) fatigue testing of the lumbar extensor musculature using electromyography.

RESULTS/FINDINGS

Despite issues interpreting individual studies due to methods, the majority of evidence suggests LBP is associated with decreased strength/endurance, atrophy, and excessive fatigability of the lumbar extensors. Prospective studies also suggest lumbar extensor deconditioning may be a common risk factor predicting acute low back injury and LBP.

CONCLUSIONS

The hypothesis of specific lumbar extensor deconditioning as being a causal factor in LBP is presently well supported. It is by no means the only causative factor and further research should more rigorously test this hypothesis addressing the methodological issues highlighted regarding previous studies. However, its role suggests specific exercise may be a worthwhile preventative and rehabilitative approach.

Why do some intervertebral discs degenerate, when others (in the same spine) do not?

This review suggests why some discs degenerate rather than age normally. Intervertebral discs are avascular pads of fibrocartilage that allow movement between vertebral bodies. Human discs have a low cell density and a limited ability to adapt to mechanical demands. With increasing age, the matrix becomes yellowed, fibrous, and brittle, but if disc structure remains intact, there is little impairment in function, and minimal ingrowth of blood vessels or nerves. Approximately half of old lumbar discs degenerate in the sense of becoming physically disrupted. The posterior annulus and lower lumbar discs are most affected, presumably because they are most heavily loaded. Age and genetic inheritance can weaken discs to such an extent that they are physically disrupted during everyday activities. Damage to the endplate or annulus typically decompresses the nucleus, concentrates stress within the annulus, and allows ingrowth of nerves and blood vessels. Matrix disruption progresses by mechanical and biological means. The site of initial damage leads to two disc degeneration "phenotypes": endplate-driven degeneration is common in the upper lumbar and thoracic spine, and annulus-driven degeneration is common at L4-S1. Discogenic back pain can be initiated by tissue disruption, and amplified by inflammation and infection. Healing is possible in the outer annulus only, where cell density is highest. We conclude that some discs degenerate because they are disrupted by excessive mechanical loading. This can occur without trauma if tissues are weakened by age and genetic inheritance. Moderate mechanical loading, in contrast, strengthens all spinal tissues, including discs.

Persistent degenerative changes in the intervertebral disc after burst fracture in an in vitro model mimicking physiological post-traumatic conditions

PURPOSE

Post-traumatic disc degeneration (DD) is currently investigated with models not fully matching the clinical condition, in particular post-traumatic loading of the disc is not considered. Therefore, the aim was to establish an in vitro burst fracture model that more closely mimics the in vivo situation by including post-traumatic physiological loading and to investigate DD under these conditions.

METHODS

72 rabbit spinal segments (disc/endplates + 1/3 of adjacent vertebrae) were harvested from T8/9 to L5/6 and assigned to control (n = 36) or trauma groups (n = 36). Burst fractures were induced at day 0 in the trauma group using a dropped-weight device. From day 1 to 28, all specimens were cultured at 37 °C and were dynamically loaded daily (~1 MPa nominal pressure, 1 Hz, 2,500 cycles). At day 1, 7, 14, and 28, 9 specimens from each group were taken for analysis: histology (n = 2), total disc glycosaminoglycan (GAG) content (n = 3) normalized to DNA, and qPCR of DD marker genes (n = 4) in the nucleus pulposus and the annulus fibrosus.

RESULTS

Burst fracture with post-traumatic physiological loading resulted in a 65 % loss of GAG/DNA by day 28. Histological sections confirmed the remodeling of the matrix. Catabolic (MMP-1/-3), pro-apoptotic (TNF-α, fas ligand), and pro-inflammatory (IL-1/-6, iNOS) gene transcription was substantially up-regulated in the nucleus after the trauma and did not normalize to control within 28 days. Similar results were found for the annulus on lower levels.

CONCLUSION

An in vitro burst fracture model with physiological post-traumatic loading was established. Under these conditions, burst spinal segments undergo strong and persistent degenerative changes.

The effect of a cyclooxygenase 2 inhibitor on early degenerated human nucleus pulposus explants

Study Design Preclinical in vitro culture of human degenerated nucleus pulposus (NP) tissue. Objective Cyclooxygenase 2 inhibitors (e.g., celecoxib) inhibit prostaglandin E2 (PGE2) production, and they have been shown to upregulate regeneration of articular cartilage. In this study, we developed an explant culture system for use with human tissue and tested the potential of celecoxib. Methods NP explants were cultured with or without 1 μM of celecoxib and were analyzed at days 0 and 7 for biochemical content (water, sulfated glycosaminoglycans, hydroxyproline, and DNA), gene expression (for disk matrix anabolic and catabolic markers), and PGE2 content. Results Water and biochemical contents as well as gene expression remained close to native values after 1 week of culture. PGE2 levels were not increased in freshly harvested human NP tissue and thus were not reduced in treated tissues. Although no anabolic effects were observed at the dosage and culture duration used, no detrimental effects were observed and some specimens did respond by lowering PGE2. Conclusions Human degenerated NP explants were successfully cultured in a close to in vivo environment for 1 week. Further research, especially dosage-response studies, is needed to understand the role of PGE2 in low back pain and the potential of celecoxib to treat painful disks.

Inflammatory mediators in intervertebral disk degeneration and discogenic pain

Although degeneration of the intervertebral disk has historically been described as a misbalance between anabolic and catabolic factors, the role of inflammatory mediators has long been neglected. However, past research clearly indicates that inflammatory mediators such as interleukin (IL)-1β, IL-6, IL-8 and tumor necrosis factor-α are expressed at higher levels in "diseased" intervertebral disks. Both disk cells as well as invading macrophages can be the source of the detected cytokines. Importantly, occurrence of inflammatory mediators in the disk can worsen the progress of degeneration by inducing the expression of matrix degrading enzymes as well as by inhibiting extracellular matrix synthesis. In addition, inflammatory mediators play a crucial role in pain development during intervertebral disk herniation (i.e., sciatica) and disk degeneration (i.e., discogenic pain). This review provides information on the most relevant inflammatory mediators during different types of disk diseases and explains how these factors can induce disk degeneration and the development of discogenic and sciatic/radiculopathic pain.

Notochordal cell-derived therapeutic strategies for discogenic back pain

An understanding of the processes that occur during development of the intervertebral disk can help inform therapeutic strategies for discogenic pain. This article reviews the literature to identify candidates that are found in or derived from the notochord or notochordal cells and evaluates the theory that such factors could be isolated and used as biologics to target the structural disruption, inflammation, and neurovascular ingrowth often associated with discogenic back pain. A systematic review using PubMed was performed with a primary search using keywords "(notochordal OR notochord) And (nerves OR blood vessels OR SHH OR chondroitin sulfate OR notch OR CTGF) NOT chordoma." Secondary searches involved keywords associated with the intervertebral disk and pain. Several potential therapeutic candidates from the notochord and their possible targets were identified. Studies are needed to further identify candidates, explore mechanisms for effect, and to validate the theory that these candidates can promote structural restoration and limit or inhibit neurovascular ingrowth using in vivo studies.

The Use of a Novel Injectable Hydrogel Nucleus Pulposus Replacement in Restoring the Mechanical Properties of Cyclically Fatigued Porcine Intervertebral Discs

Repeated flexion and extension of an intervertebral disc has been shown to affect the angular stiffness of spinal motion segments and is a barometer of the mechanical integrity of the disc. A degenerated disc that loses height causes higher levels of stress on the annulus and facet joints which may increase its level of degeneration; restoring disc height may therefore help to slow this degenerative cascade. Previous research has indicated that nucleus implants have the potential to improve the mechanical characteristics of a disc and an implant that is custom-fit to the intervertebral disc yields the best results with respect to decreasing annular degeneration. Two groups of porcine spinal motion segments were exposed to repeated flexion and extension. One group was then injected with a novel hydrogel while the other group was used as a control. Both groups were then exposed to another round of cyclic flexion and extension to examine the effect that the hydrogel had on restoring the original mechanics to the motion segments. Angular stiffness was restored to the group which received the hydrogel injection in addition to a significant improvement in specimen height. No significant changes were seen in the group which did not receive an injection. It would appear that use of the novel injectable hydrogel is able to restore angular stiffness to cyclically fatigued spinal motion segments. It is also important to note that continued repetition of the event causing specimen fatigue after performing hydrogel injection will result in an eventual return to the same fatigued state.

Long-term culture of bovine nucleus pulposus explants in a native environment

BACKGROUND CONTEXT

Chronic low back pain is a disease with tremendous financial and social implications, and it is often caused by intervertebral disc degeneration. Regenerative therapies for disc repair are promising treatments, but they need to be tested in physiological models.

PURPOSE

To develop a physiological in vitro explant model that incorporates the native environment of the intervertebral disc, for example, hypoxia, low glucose, and high tissue osmolarity.

STUDY DESIGN

Bovine nucleus pulposus (NP) explants were cultured for 42 days in conditions mimicking the native physiological environment. Two different approaches were used to balance the swelling pressure of the NP: raised medium osmolarity or an artificial annulus.

METHODS

Bovine NP explants were either cultured in media with osmolarity balanced at isotonic and hypertonic levels compared with the native tissue or cultured inside a fiber jacket used as an artificial annulus. Oxygen and glucose levels were set at either standard (21% O2 and 4.5 g/L glucose) or physiological (5% O2 and 1 g/L glucose) levels. Samples were analyzed at Day 0, 3, and 42 for tissue composition (water, sulfated glycosaminoglycans, DNA, and hydroxyproline contents and fixed charge density), tissue histology, cell viability, and cellular behavior with messenger RNA (mRNA) expression.

RESULTS

Both the hypertonic culture and the artificial annulus approach maintained the tissue matrix composition for 42 days. At Day 3, mRNA expressions of aggrecan, collagen Type I, and collagen Type II in both hypertonic and artificial annulus cultures were not different from Day 0; however, at Day 42, the artificial annulus preserved the mRNA expression closer to Day 0. Gene expressions of matrix metalloprotease 13, tissue inhibitor of matrix metalloprotease 1, and tissue inhibitor of matrix metalloprotease 2 were downregulated under physiological O2 and glucose levels, whereas the other parameters analyzed were not affected.

CONCLUSIONS

Although the hypertonic culture and the artificial annulus approach are both promising models to test regenerative therapies, the artificial annulus was better able to maintain a cellular behavior closer to the native tissue in longer term cultures.

Preliminary evidence for the features of non-reducible discogenic low back pain: survey of an international physiotherapy expert panel with the Delphi technique

OBJECTIVES

The lumbar intervertebral disc is a known source of low back pain (LBP). Various clinical features of discogenic pain have been proposed, but none have been validated. Several subgroups of discogenic pain have been hypothesised, with non-reducible discogenic pain (NRDP) proposed as a relevant clinical subgroup. The objectives of this study were to obtain consensus from an expert panel on the features of discogenic low back pain, the existence of subgroups of discogenic LBP, particularly NRDP, and the associated features of NRDP.

DESIGN

Three-round Delphi survey.

PARTICIPANTS

Twenty-one international physiotherapists with expertise in LBP.

METHODS

Panellists listed and ranked features that they believed to be indicative of discogenic pain and NRDP. On completion of Round 3, features with ≥50% agreement between panellists were deemed to have reached consensus.

RESULTS

After three rounds, 10 features of discogenic LBP were identified. Nineteen of the panellists believed that NRDP was a subgroup of discogenic LBP, and nine features of NRDP were identified.

CONCLUSION

This study provides preliminary validation for the features associated with discogenic LBP. It also provides evidence supporting the existence and features of NRDP as a separate clinical subgroup of discogenic LBP.