Establishment of an Animal Model of Disk Degeneration by Intradiskal Injection of Monosodium Iodoacetate.

BACKGROUND: Disk degeneration (DD) stands for the most common cause of low back pain. The establishment of an animal model plays an intrinsic role in the clarification of the physiopathology of DD. The purpose of this study is to select an optimal dose of monosodium iodoacetate (MIA) that may generate a reliable model of DD. METHODS: Thirty-four rats were used in this study. The disks (Co7/8, Co8/9, and Co 9/10) received 1 shot of intradiskal injection of 0.02 mg, 0.1 mg, and 0.5 mg of MIA solution, respectively. Half of the rats were euthanized 3 weeks after MIA injection, and the other half 6 weeks after injection. RESULTS: Magnetic resonance imaging evaluation showed that the mean T2-weighted signal intensity at 6 weeks decreased significantly in the 0.1 and 0.5 mg groups. The disk height of the control group was significantly higher than those of the 0.1 mg and 0.5 mg groups. Histologic and macroscopic results revealed time-and-dose-depending degeneration in the disks that received MIA. Additionally, MIA produced cell death in the nucleus pulposus cells with an elevated percentage. The injected disk with 0.1 mg MIA demonstrated a progressive degeneration, the disk injected with 0.5 mg MIA induced DD acutely 3 weeks post MIA injection, while the dose of 0.02 mg of MIA did not show much degeneration. CONCLUSIONS: We concluded that 0.1 mg MIA is the most suitable dose to establish a model of DD, which enabled us to replicate the onset, progression, and outcome of diverse histopathologies of DD in the clinic.

Development of a novel model of intervertebral disc degeneration by the intradiscal application of monosodium iodoacetate (MIA) in rat.

BACKGROUND CONTEXT: Low back pain is one of the most common musculoskeletal disorders. Although, the pathology of intervertebral disc (IVD) degeneration has been modeled using various biological methods, these models are inadequate for simulating similar pathologic states in humans. PURPOSE: This study investigated whether monosodium iodoacetate (MIA) injection into the IVD of rats could generate a reliable model of IVD degeneration. STUDY DESIGN/SETTINGS: In vivo animal study. METHODS: MIA was injected into two-disc spaces (L4-5 and L5-6) of Sprague-Dawley rats. Their behaviors were examined by measuring weight load shifts from hind to forefoot, rearing, and von Frey tests. We examined the inhibition of pain behavior through intraperitoneal morphine injection and measured cyclooxygenase-2 (COX-2) and transcription factor nuclear factor-kappa B (NF-κB) levels in the IVD and dorsal root ganglion (DRG) by Western blot. Bone alterations were assessed by microfocus computed tomography (micro-CT), and IVD and/or cartilage changes were evaluated by hematoxylin and eosin and safranin-O staining and inducible nitric oxide synthase (iNOS) immunohistochemistry. The other authors declare no conflicts of interest. This project funded by the Memorial Fund and the National Research Foundation of Korea (NRF). RESULTS: We observed increased weight load shifts to the forefoot and decreased rearing. Morphine-injected rats showed reduced pain. NF-κB and COX-2 expression increased in the IVD and left and/or right DRG. Micro-CT analyses suggested progressive bone deformation. Histologic examination showed decreased IVD width and nucleus pulposus area. Cartilaginous changes indicated epiphyseal growth plate loss. Finally, iNOS expression was increased in the subchondral endplate. CONCLUSIONS: These results suggest that low back pain (LBP) models can be developed by MIA injection into the IVDs of rats and that an animal model is useful for exploring degenerative alterations in the affected discs. Therefore, MIA injection may be a useful model for the study of changes in the IVD to elucidate the mechanisms underlying clinical symptoms, such as LBP, in patients with IVD degeneration. CLINICAL SIGNIFICANCE: This model in which MIA was injected into the disc better represented the human histologic and behavioral characteristics than the existing puncture model.

Intradiscal injection of monosodium iodoacetate induces intervertebral disc degeneration in an experimental rabbit model.

BACKGROUND: Establishing an optimal animal model for intervertebral disc (IVD) degeneration is essential for developing new IVD therapies. The intra-articular injection of monosodium iodoacetate (MIA), which is commonly used in animal models of osteoarthritis, induces cartilage degeneration and progressive arthritis in a dose- and time-dependent manner. The purpose of this study was to determine the effect of MIA injections into rabbit IVDs on the progression of IVD degeneration evaluated by radiographic, micro-computerized tomography (micro-CT), magnetic resonance imaging (MRI), and histological analyses. METHODS: In total, 24 New Zealand White (NZW) rabbits were used in this study. Under general anesthesia, lumbar discs from L1-L2 to L4-L5 had a posterolateral percutaneous injection of MIA in contrast agent (CA) (L1-L2: CA only; L2-L3: MIA 0.01 mg; L3-L4: 0.1 mg; L4-L5: 1.0 mg; L5-L6: non-injection (NI) control). Disc height was radiographically monitored biweekly until 12 weeks after injection. Six rabbits were sacrificed at 2, 4, 8, and 12 weeks post-injection and processed for micro-CT, MRI (T2-mapping), and histological analyses. Three-dimensional (3D) disc height in five anatomical zones was evaluated by 3D reconstruction of micro-CT data. RESULTS: Disc height of MIA-injected discs (L2-L3 to L4-L5) gradually decreased time-dependently (P < 0.0001). The disc height of MIA 0.01 mg-injected discs was significantly higher than those of MIA 0.1 and 1.0 mg-injected discs (P < 0.01, respectively). 3D micro-CT analysis showed the dose- and time-dependent decrease of 3D disc height of MIA-injected discs predominantly in the posterior annulus fibrosus (AF) zone. MRI T2 values of MIA 0.1 and 1.0 mg-injected discs were significantly decreased compared to those of CA and/or NI controls (P < 0.05). Histological analyses showed progressive time- and dose-degenerative changes in the discs injected with MIA (P < 0.01). MIA induced cell death in the rabbit nucleus pulposus with a high percentage, while the percentage of cell clones was low. CONCLUSIONS: The results of this study showed, for the first time, that the intradiscal injection of MIA induced degenerative changes of rabbit IVDs in a time- and dose-dependent manner. This study suggests that MIA injection into rabbit IVDs could be used as an animal model of IVD degeneration for developing future treatments.

Tungsten accumulates in the intervertebral disc and vertebrae stimulating disc degeneration and upregulating markers of inflammation and pain.

Tungsten is incorporated in many industrial goods, military applications and medical devices due to its ability to impart flexibility, strength and conductance to materials. Emerging evidence has questioned the safety of tungsten exposure as studies have demonstrated it can promote tumour formation, induce pulmonary disease and alter immune function. Although tungsten is excreted from the body it can accumulate in certain organs such as the brain, colon, liver, kidneys, spleen and bones, where most of the bioaccumulation occurs. Whether prolonged tungsten exposure leads to accumulation in other tissues is unknown. The present study demonstrated that mice exposed to 15 ppm sodium tungstate for 4 weeks in their drinking water showed comparable accumulation in both the bony vertebrae and intervertebral discs (IVDs). Lumbar IVD height was significantly reduced in tungsten-exposed mice and accompanied by decreased proteoglycan content and increased fibrosis. In addition to catabolic enzymes, tungsten also increased the expression of the inflammatory cytokines IL-1ß and tumour necrosis factor (TNF)-α as well as the neurotrophic factors nerve growth factor (NGF) and brain-derived nerve factor (BDNF) in IVD cells. Tungsten significantly increased the presence of nociceptive neurons at the endplates of IVDs as observed by the expression of calcitonin gene-related peptide (CGRP) and anti-protein gene product 9.5 (PGP9.5) in endplate vessels. The present study provided evidence that tungsten may enhance disc degeneration and fibrosis as well as increase the expression of markers for pain. Therefore, tungsten toxicity may play a role in disc degeneration disease.

Magnetic resonance imaging evaluation of the effects of cigarette and maras powder (smokeless tobacco) on lumbar disc degeneration.

OBJECTIVE: The main aim of this study was to investigate and compare the effects of the use of Maras powder and cigarettes on lumbar disc degeneration. PAIENTS AND METHODS: This study included 87 adult patients who presented at our hospital with a complaint of mechanical low back pain and underwent lumbar magnetic resonance imaging (MRI). Patients meeting the inclusion criteria were divided into three groups. Group 1 included those who smoked Maras powder but not cigarettes, group 2 was comprised of those who smoked cigarettes but did not use Maras powder, and group 3 was comprised of those who did not use tobacco (no cigarettes or Maras powder) (control group). Lumbar disc degeneration was rated according to the Pfirrmann classification. Hematological parameters were obtained from all three groups. RESULTS: Degeneration levels in group 1 were significant when compared to the other groups at all disc levels. Maras powder contributed to intervertebral disc degeneration and this effect increased gradually towards the distal area. The neutrophil to lymphocyte ratio was significantly higher in group 1 than in the other two groups, and was positively correlated with the duration of use of Maras powder (r = 0.689, p ≤ 0.001). CONCLUSION: Although more prevalent in the Maras powder group, lumbar disc degeneration increased significantly with tobacco usage. The results of our study show that Maras powder, commonly used regionally, is likely to cause more spinal disc degeneration than cigarettes.

High glucose promotes annulus fibrosus cell apoptosis through activating the JNK and p38 MAPK pathways.

Diabetes mellitus (DM) is an important risk factor of intervertebral disc degeneration. A high glucose niche-mediated disc cell apoptosis is an implicate causative factor for the spine degenerative diseases related with DM. However, the effects of a high glucose niche on disc annulus fibrosus (AF) cell apoptosis and the potential signaling transduction pathway is unclear. The present study is to investigate the effects of high glucose on disc AF cell apoptosis and the role of two potential signaling pathways in this process. Rat AF cells were cultured in baseline medium or medium with different concentrations (0.1 and 0.2 M) of glucose for 3 days. Flow cytometry was used to assess the degree of apoptosis. Activity of caspase 3/9 was evaluated by chemical kit. Expression of pro-apoptotic and anti-apoptotic molecules was analyzed by real-time polymerase chain reaction and Western blot. In addition, activity of the C-Jun NH2-terminal kinases (JNK) pathway and p38 mitogen-activated protein kinase (MAPK) pathway was evaluated by Western blot. Compared with the control group, high glucose culture increased cell apoptosis ratio and caspase-3/9 activity, up-regulated expression of bax, caspase-3, cleaved caspase-3 and cleaved PARP, and down-regulated expression of bcl-2 in a glucose concentration-dependent manner. Additionally, high glucose culture increased expression of the p-JNK and p-p38 MAPK in a concentration-dependent manner. Further results showed that inhibition of the JNK or p38 MAPK pathway attenuated the effects of high glucose on AF cell apoptosis. Together, high glucose promoted disc AF cell apoptosis through regulating the JNK pathway and p38 MAPK pathway in a glucose concentration-dependent manner.

Inhibition of both endplate nutritional pathways results in intervertebral disc degeneration in a goat model.

BACKGROUND: The vertebral endplate route was demonstrated to be the main pathway for nutrition to the intervertebral disc. However, it is still a controversial issue on whether the blocking of the endplate nutritional pathway could result in intervertebral disc degeneration (IDD) in animal models. The aim was therefore to investigate the effect of the inhibition of both endplate nutritional pathways by bone cement injection on the IDD in a goat model. METHODS: Two lumbar intervertebral discs (L2-3 and L3-4) in eight 24-month-old goats were blocked in both endplate nutritional pathways by cement injection, and the other two lumbar intervertebral discs (L1-2 and L4-5) remained intact as normal controls. Effective blocking area percentage in nucleus pulposus (NP) was calculated, and X-rays, magnetic resonance imaging (MRI), and histology studies were performed at 4, 12, 24, and 48 weeks after operation. RESULTS: The mean effective blocking area percentage was 60.7 ± 5.3%. Imaging examinations at the time of 48 weeks after blocking the endplate nutritional pathways showed obvious IDD, with larger disc height reduction and higher degrees of disc degeneration grading compared with the normal controls. Histological examinations including HE, Masson's trichrome, Sirius Red, and proteoglycan stainings also confirmed the degenerative changes of the blocked discs. CONCLUSIONS: The endplate nutritional route could be inhibited by blocking both endplate pathways with cement injection in a goat model. The severe inhibition in the endplate nutritional pathways may result in IDD.

Effects of Intradiscal Injection of Local Anesthetics on Intervertebral Disc Degeneration in Rabbit Degenerated Intervertebral Disc.

Analgesic discoblock is widely used for the diagnosis or treatment of discogenic low back pain by injecting local anesthetics. The purpose of this study was to investigate the deleterious effects of local anesthetics on degenerated rabbit intervertebral disks (IVDs) using an organotypic culture model and in vivo long-term follow-up model. To induce IVD degeneration, a rabbit annular puncture model was used. For the organotypic culture model, degenerated IVDs were harvested 1 month after the initial annular puncture and cultured for 3 or 7 days after intradiscal injection of local anesthetics (1% lidocaine and 0.5% bupivacaine). To perform in vivo analysis, local anesthetics were injected into degenerated IVDs, and IVDs were prepared for histological analysis after 6 or 12 months. In the organotypic model, terminal deoxynucleotidyl transferase dUTP nick end labeling-positive nucleus pulposus (NP) cells were significantly increased in the bupivacaine group compared with the other groups. In the in vivo study, the number of NP cells was significantly decreased in the saline and local anesthetics groups compared with the untreated control and puncture-only groups. However, there was no significant difference among the saline, lidocaine, and bupivacaine groups. In addition, histological analysis showed no significant difference of IVD degeneration among the puncture-only, saline, lidocaine, and bupivacaine groups. Although bupivacaine induced apoptotic NP cell death in the organotypic culture model, in vivo observations did not show any definitive proof to suggest that local anesthetics were capable of promoting degeneration in the degenerated IVD, except for pressurized injection-induced damage. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1963-1971, 2019.

Are radio-contrast agents commonly used in discography toxic to the intact intervertebral disc tissue cells?

In the literature, there have been no studies showing clear results on how radio-contrast pharmaceuticals would affect intact disc tissue cells. In this context, it was aimed to evaluate the effects of iopromide and gadoxetic acid, frequently used in the discography, on intact lumbar disc tissue in pharmaco-molecular and histopathological level. Primary cell cultures were prepared from the healthy disc tissue of the patients operated in the neurosurgery clinic. Except for the control group, the cultures were incubated with the indicated radio-contrast agents. Cell viability, toxicity and proliferation indices were tested at specific time intervals. The cell viability was quantitatively analysed. It was also visually rechecked under a fluorescence microscope with acridine orange/propidium iodide staining. Simultaneously, cell surface morphology was analysed with an inverted light microscope, while haematoxylin and eosin (H&E) staining methodology was used in the histopathological evaluations. The obtained data were evaluated statistically. Unlike the literature, iopromide or gadoxetic acid did not have any adverse effects on the cell viability, proliferation and toxicity (P < 0.05). Although this study reveals that radio-contrast pharmaceuticals used in the discography, often used in neurosurgical practice, can be safely used, it should be remembered that this study was performed in an in vitro environment.

Melatonin protects vertebral endplate chondrocytes against apoptosis and calcification via the Sirt1-autophagy pathway.

Melatonin is reportedly associated with intervertebral disc degeneration (IDD). Endplate cartilage is vitally important to intervertebral discs in physiological and pathological conditions. However, the effects and mechanism of melatonin on endplate chondrocytes (EPCs) are still unclear. Herein, we studied the effects of melatonin on EPC apoptosis and calcification and elucidated the underlying mechanism. Our study revealed that melatonin treatment decreases the incidence of apoptosis and inhibits EPC calcification in a dose-dependent manner. We also found that melatonin upregulates Sirt1 expression and activity and promotes autophagy in EPCs. Autophagy inhibition by 3-methyladenine reversed the protective effect of melatonin on apoptosis and calcification, while the Sirt1 inhibitor EX-527 suppressed melatonin-induced autophagy and the protective effects of melatonin against apoptosis and calcification, indicating that the beneficial effects of melatonin in EPCs are mediated through the Sirt1-autophagy pathway. Furthermore, melatonin may ameliorate IDD in vivo in rats. Collectively, this study revealed that melatonin reduces EPC apoptosis and calcification and that the underlying mechanism may be related to Sirt1-autophagy pathway regulation, which may help us better understand the association between melatonin and IDD.

Time-Course Investigation of Intervertebral Disc Degeneration Induced by Different Sizes of Needle Punctures in Rat Tail Disc.

BACKGROUND This study aimed to determine the best size needle to use in inducing IVDD and to find the proper time point of disc degeneration suitable for further biologic treatment study. MATERIAL AND METHODS First, rat tail level 5/6, 7/8, and 9/10 discs were punctured by 18G, 21G, or 25G needles. Then, degeneration was assessed by radiography, MRI, and histological evaluation at 2, 4, and 6 weeks after puncture. Later, real-time reverse transcriptase (RT-PCR) was used to examine mRNA expressions of aggrecan, collagen type II, hypoxia-inducible factor-1a (HIF-1a), glucose transporter1 (GLUT-1), and vascular endothelial growth factor (VEGF). RESULTS Significant differences were identified in almost all parameters compared with the control group in the 18G and 21G group at almost all time points. To assess the effect of different needle sizes on DHI, we used magnetic resonance imaging (MRI), grade, and mRNA expression. We found significant differences between different groups, except for DHI between the 21G group and 25G group and MRI grade between the 18G and 21G group at the 2-week time point. In assessing the effect of different needle sizes on HE staining score and toluidine blue staining grade, statistical differences were observed at some time points. The effects of time on all parameters were significant at almost all time points in all groups. CONCLUSIONS The middle-size needle (21G) performed better in inducing disc degeneration. The 2-week time point may be better for use in further experimental studies.

Overexpression of miR-140-5p inhibits lipopolysaccharide-induced human intervertebral disc inflammation and degeneration by downregulating toll-like receptor 4.

Toll-like receptor 4 (TLR4) families are receptors for ligands that initiate extracellular or intracellular signaling, such as lipopolysaccharides (LPS). It has been reported that TLR4 activation resulted in the upregulation of a coordinated set of proinflammatory mediators and inhibition of matrix expression in the intervertebral disc (IVD). miR-140-5p (miR-140) is reported to participate in cellular anti-inflammatory processes and target TLR4. In the present study, we investigated the relationship between TLR4 and miR-140 in IVD degeneration. The expression of TLR4, interleukin (IL)-6, IL-I, L-1ß and tumor necrosis factor (TNF)-α was higher, in high-grade IVD degeneration tissues than in low-grade tissues. In contrast, the expression of miR-140, aggrecan and collagen type II was lower in high-grade IVD degeneration tissues than in low-grade IVD degeneration tissues. LPS stimulation resulted in significant increases in TLR4 expression and decreases in miR-140 expression in nucleus pulposus (NP) cells and TLR4 was identified as a target of miR-140 by dual-luciferase reporter assay. The overexpression of miR-140 inhibited the upregulation of the expression of TLR4, TNF-α, IL-1ß and IL-6 inflammation cytokines, and the activation of NF-κB and reversed the downregulation of the expression of aggrecan and collagen type II induced by LPS stimulation. In conclusion, the present study may lead to a greater understanding of IVD degeneration and provide new insights into the treatment of this disease.

Spermidine promotes nucleus pulposus autophagy as a protective mechanism against apoptosis and ameliorates disc degeneration.

Spermidine has therapeutic effects in many diseases including as heart diastolic function, myopathic defects and neurodegenerative disorders via autophagy activation. Autophagy has been found to mitigate cell apoptosis in intervertebral disc degeneration (IDD). Accordingly, we theorize that spermidine may have beneficial effects on IDD via autophagy stimulation. In this study, spermidine's effect on IDD was evaluated in tert-butyl hydroperoxide (TBHP)-treated nucleus pulposus cells of SD rats in vitro as well as in a puncture-induced rat IDD model. We found that autophagy was actuated by spermidine in nucleus pulposus cells. In addition, spermidine treatment weakened the apoptotic effects of TBHP in nucleus pulposus cells. Spermidine increased the expression of anabolic proteins including Collagen-II and aggrecan and decreased the expression of catabolic proteins including MMP13 and Adamts-5. Additionally, autophagy blockade using 3-MA reversed the beneficial impact of spermidine against nucleus pulposus cell apoptosis. Autophagy was thus important for spermidine's therapeutic effect on IDD. Spermidine-treated rats had an accentuated T2-weighted signal and a diminished histological degenerative grade than vehicle-treated rats, showing that spermidine inhibited intervertebral disc degeneration in vivo. Thus, spermidine protects nucleus pulposus cells against apoptosis through autophagy activation and improves disc, which may be beneficial for the treatment of IDD.

A Degenerative/Proinflammatory Intervertebral Disc Organ Culture: An Ex Vivo Model for Anti-inflammatory Drug and Cell Therapy.

Resolution of intervertebral disc (IVD) degeneration-associated inflammation is a prerequisite for tissue regeneration and could possibly be achieved by strategies ranging from pharmacological to cell-based therapies. In this study, a proinflammatory disc organ culture model was established. Bovine caudal disc punches were needle punctured and additionally stimulated with lipopolysaccharide (10 µg/mL) or interleukin-1ß (IL-1ß, 10-100 ng/mL) for 48 h. Two intradiscal therapeutic approaches were tested: (i) a nonsteroidal anti-inflammatory drug, diclofenac (Df) and (ii) human mesenchymal stem/stromal cells (MSCs) embedded in an albumin/hyaluronan hydrogel. IL-1ß-treated disc organ cultures showed a statistically significant upregulation of proinflammatory markers (IL-6, IL-8, prostaglandin E2 [PGE2]) and metalloproteases (MMP1, MMP3) expression, while extracellular matrix (ECM) proteins (collagen II, aggrecan) were significantly downregulated. The injection of the anti-inflammatory drug, Df, was able to reduce the levels of proinflammatory cytokines and MMPs and surprisingly increase ECM protein levels. These results point the intradiscal application of anti-inflammatory drugs as promising therapeutics for disc degeneration. In parallel, the immunomodulatory role of MSCs on this model was also evaluated. Although a slight downregulation of IL-6 and IL-8 expression could be found, the variability among the five donors tested was high, suggesting that the beneficial effect of these cells on disc degeneration needs to be further evaluated. The proinflammatory/degenerative IVD organ culture model established can be considered a suitable approach for testing novel therapeutic drugs, thus reducing the number of animals in in vivo experimentation. Moreover, this model can be used to address the cellular and molecular mechanisms that regulate inflammation in the IVD and their implications in tissue degeneration.

Enhancement of Lumbar Fusion and Alleviation of Adjacent Segment Disc Degeneration by Intermittent PTH(1-34) in Ovariectomized Rats.

Osteoporosis, which is prevalent in postmenopausal or aged populations, is thought to be a contributing factor to adjacent segment disc degeneration (ASDD), and the incidence and extent of ASDD may be augmented by osteopenia. Parathyroid hormone (PTH) (1-34) has already been shown to be beneficial in osteoporosis, lumbar fusion and matrix homeostasis of intervertebral discs. However, whether PTH(1-34) has a reversing or retarding effect on ASDD in osteopenia has not been confirmed. In the present study, we evaluated the effects of intermittent PTH(1-34) on ASDD in an ovariectomized (OVX) rat model. One hundred 3-month-old female Sprague-Dawley rats underwent L4 -L5 posterolateral lumbar fusion (PLF) with spinous-process wire fixation 4 weeks after OVX surgery. Control groups were established accordingly. PTH(1-34) was intermittently administered immediately after PLF surgery and lasted for 8 weeks using the following groups (n = 20) (V = vehicle): Sham+V, OVX+V, Sham+PLF+V, OVX+PLF+V, OVX+PLF+PTH. The fused segments showed clear evidence of eliminated motion on the fusion-segment based on manual palpation. Greater new bone formation in histology was observed in PTH-treated animals compared to the control group. The extent of ASDD was significantly increased by ovariotomy. Intermittent PTH(1-34) significantly alleviated ASDD by preserving disc height, microvessel density, relative area of vascular buds, endplate thickness and the relative area of endplate calcification. Moreover, protein expression results showed that PTH(1-34) not only inhibited matrix degradation by decreasing MMP-13, ADAMTS-4 and Col-I, but also promote matrix synthesis by increasing Col-II and Aggrecan. In conclusion, PTH(1-34), which effectively improves lumbar fusion and alleviates ASDD in ovariectomized rats, may be a potential candidate to ameliorate the prognosis of lumbar fusion in osteopenia.

Effects of Tobacco Smoking on the Degeneration of the Intervertebral Disc: A Finite Element Study.

Tobacco smoking is associated with numerous pathological conditions. Compelling experimental evidence associates smoking to the degeneration of the intervertebral disc (IVD). In particular, it has been shown that nicotine down-regulates both the proliferation rate and glycosaminoglycan (GAG) biosynthesis of disc cells. Moreover, tobacco smoking causes the constriction of the vascular network surrounding the IVD, thus reducing the exchange of nutrients and anabolic agents from the blood vessels to the disc. It has been hypothesized that both nicotine presence in the IVD and the reduced solute exchange are responsible for the degeneration of the disc due to tobacco smoking, but their effects on tissue homeostasis have never been quantified. In this study, a previously presented computational model describing the homeostasis of the IVD was deployed to investigate the effects of impaired solute supply and nicotine-mediated down-regulation of cell proliferation and biosynthetic activity on the health of the disc. We found that the nicotine-mediated down-regulation of cell anabolism mostly affected the GAG concentration at the cartilage endplate, reducing it up to 65% of the value attained in normal physiological conditions. In contrast, the reduction of solutes exchange between blood vessels and disc tissue mostly affected the nucleus pulposus, whose cell density and GAG levels were reduced up to 50% of their normal physiological levels. The effectiveness of quitting smoking on the regeneration of a degenerated IVD was also investigated, and showed to have limited benefit on the health of the disc. A cell-based therapy in conjunction with smoke cessation provided significant improvements in disc health, suggesting that, besides quitting smoking, additional treatments should be implemented in the attempt to recover the health of an IVD degenerated by tobacco smoking.

Intervertebral disc degenerative changes after intradiscal injection of TNF-α in a porcine model.

PURPOSE: To investigate whether exogenous tumor necrosis factor-α (TNF-α) will initiate a degenerative process in intervertebral disc in vivo. METHODS: Exogenous TNF-α in dosages of 50 and 100 ng in 50 µL Dulbecco's Modified Essential Medium (DMEM) was injected into porcine lumbar discs; a third disc was injected only with 50 µL DMEM as a control. Magnetic resonance imaging (MRI) yielding T1- and T2-weighted images, T2-mapping, and post-contrast T1 images was performed and histology was studied as well. RESULTS: After 3 months, a significant decrease in T2 value calculated from T2-mapping MRI was observed in the annulus and nucleus of both groups injected with TNF-α along with a slight decrease in disc height and nucleus volumes in comparison to the control discs. No obvious visual differences among the groups were observed in the normal T1- and T2-weighted MRI images. Post-contrast T1 MRI showed increased annulus enhancement in both TNF-α-injected groups compared to the control discs, while no enhancement difference was observed in the nucleus. Histological analysis showed degenerative changes with annulus fissure, cell cluster, nucleus matrix loss, vascularization and interleukin-1ß expression in the outer annulus of both TNF-α-injected discs, while no degenerative changes were observed in the control discs. CONCLUSIONS: Intradiscal injection of exogenous TNF-α caused early stage disc degeneration in a porcine model. It may thus support the hypothesis of exogenic TNF-α being an important early pathogenetic factor in disc degeneration.

Pingyangmycin-induced in vivo lumbar disc degeneration model of rhesus monkeys.

STUDY DESIGN: Animal experimental study. OBJECTIVE: To establish a slowly progressive and reproducible intervertebral disc degeneration model and determine the performance of T1ρ magnetic resonance imaging in the evaluation of disc degeneration. SUMMARY OF BACKGROUND DATA: Recently, one of the hotspots of research efforts was related to management of early stage of disc degeneration. To our knowledge, a functional animal model that mimics ischemic and slowly progressive disc degeneration of humans does not exist. METHODS: The subchondral bone adjacent to the lumbar intervertebral discs (from L3-L4 to L6-L7) of 8 rhesus monkeys was randomly injected with 4 mL of Pingyangmycin (PYM) solution (1.5 mg/mL, PYM), or 4 mL of phosphate buffered saline (Vehicle control), or exteriorized but not injected anything (Sham), respectively. The degenerative process was investigated by using radiography and T1ρ magnetic resonance imaging at 1, 3, 6, 9, 12, and 15 months postoperatively. Histological scoring, immunohistochemistry, and real-time polymerase chain reaction were performed at 15 months. RESULTS: The mean T1ρ values of nucleus pulposus and annulus fibrosus in the PYM group significantly decreased after 3 and 6 months, respectively, followed by slow decrease, and the histological score was significantly higher at 15 months, compared with the control groups. The results of molecular analysis revealed a significant increase matrix metalloprotease-3, A disintegrin and metalloproteinase with thrombospondin motifs -5, tumor necrosis factor α, interleukin-1ß, interleukin-6 expressions, and marked reduction in aggrecan, type II collagen, von Willebrand factor expressions at the messenger RNA levels in the PYM group. Spearman correlation analysis of Pfirrmann grades showed significantly inverse correlation with T1ρ values of nucleus pulposus and annulus fibrosus (r = -0.634, -0.617, respectively, P < 0.01). CONCLUSION: Injection of PYM into the subchondral bone adjacent to the lumbar intervertebral discs of rhesus monkeys can results in mild, slowly progressive disc degeneration, which mimics the onset of human disc degeneration, and the T1ρ magnetic resonance imaging is suited for evaluating intervertebral disc degeneration. LEVEL OF EVIDENCE: N/A.

Chronic ingestion of advanced glycation end products induces degenerative spinal changes and hypertrophy in aging pre-diabetic mice.

Intervertebral disc (IVD) degeneration and pathological spinal changes are major causes of back pain, which is the top cause of global disability. Obese and diabetic individuals are at increased risk for back pain and musculoskeletal complications. Modern diets contain high levels of advanced glycation end products (AGEs), cyto-toxic components which are known contributors to obesity, diabetes and accelerated aging pathologies. There is little information about potential effects of AGE rich diet on spinal pathology, which may be a contributing cause for back pain which is common in obese and diabetic individuals. This study investigated the role of specific AGE precursors (e.g. methylglyoxal-derivatives (MG)) on IVD and vertebral pathologies in aging C57BL6 mice that were fed isocaloric diets with standard (dMG+) or reduced amounts of MG derivatives (dMG-; containing 60-70% less dMG). dMG+ mice exhibited a pre-diabetic phenotype, as they were insulin resistant but not hyperglycemic. Vertebrae of dMG+ mice displayed increased cortical-thickness and cortical-area, greater MG-AGE accumulation and ectopic calcification in vertebral endplates. IVD morphology of dMG+ mice exhibited ectopic calcification, hypertrophic differentiation and glycosaminoglycan loss relative to dMG- mice. Overall, chronic exposure to dietary AGEs promoted age-accelerated IVD degeneration and vertebral alterations involving ectopic calcification which occurred in parallel with insulin resistance, and which were prevented with dMG- diet. This study described a new mouse model for diet-induced spinal degeneration, and results were in support of the hypothesis that chronic AGE ingestion could be a factor contributing to a pre-diabetic state, ectopic calcifications in spinal tissues, and musculoskeletal complications that are more generally known to occur with chronic diabetic conditions.