Acidic Environment Induces Pyroptosis of NLRP3 Inflammatory Vesicle-Mediated Nucleus Pulposus Cells Through Up-Regulation of POSTN Expression

SUMMARY: Intervertebral disc degeneration (IVDD) is induced by nucleus pulposus (NP) dysfunction as a result of massive loss of NP cells. It has been reported that the acidic microenvironment of the intervertebral disc (IVD) can induce NP cell pyroptosis, and that up-regulation of periostin (POSTN) expression has a negative effect on NP cell survival. However, the relationship between the acidic environment, POSTN expression level and NP cell pyroptosis is unclear. Therefore, the aim of this study was to explore the relationship between acidic environment and POSTN expression level in NP cells, as well as the effect of POSTN in acidic environment on NP cell pyroptosis. NP cells were obtained from the lumbar vertebrae of Sprague Dawley (SD) male rats. These cells were divided into normal and acidic groups according to whether they were exposed to 6 mM lactic acid solution. And NP cells in the acidic group were additionally divided into three groups: (1) Blank group: no transfection; (2) NC group: cells transfected with empty vector plasmid; (3) sh-POSTN group: cells transfected with sh-POSTN plasmid to knock down the expression level of POSTN. Quantitative real-time PCR (qRT-PCR) and western blot was performed to assess the expression of POSTN at the mRNAand protein levels. CCK8 was used to evaluate cell survival. Western blot, in addition, was performed to examine acid-sensing ion channels (ASIC)-related proteins. And pyroptosis was detected by ELISA and western blot. The expression level of POSTN was significantly increased in NP cells in acidic environment. Knockdown of POSTN expression promoted the survival of NP cells in acidic environment and reduced the protein levels of ASIC3 and ASIC1a in NP cells. Moreover, knockdown of POSTN expression decreased the pyroptosis proportion of NP cells and the levels of pro-inflammatory cytokines interleukin (IL)-1β and IL-18. The levels of pyroptosis-related proteins NLRP3, ASC, cleaved-Caspase-1, and cleaved-GSDMD were also affected by the decreased POSTN expression. The extracellular acidic environment created by lactic acid solution activated NLRP3 inflammatory vesicle-induced caspase-1 to get involved in NP cell pyroptosis by up-regulating POSTN expression.

La degeneración del disco intervertebral (DDIV) es inducida por una disfunción del núcleo pulposo (NP) como resultado de una pérdida masiva de células NP. Se ha informado que el microambiente ácido del disco intervertebral (DIV) puede inducir la piroptosis de las células NP y que la regulación positiva de la expresión de periostina (POSTN) tiene un efecto negativo en la supervivencia de las células NP. Sin embargo, la relación entre el ambiente ácido, el nivel de expresión de POSTN y la piroptosis de las células NP es poco clara. Por lo tanto, el objetivo de este estudio fue explorar la relación entre el ambiente ácido y el nivel de expresión de POSTN en células NP, así como el efecto de POSTN en ambiente ácido sobre la piroptosis de las células NP. Las células NP se obtuvieron de las vertebras lumbares de ratas macho Sprague Dawley (SD). Estas células se dividieron en grupos normales y ácidos según se expusieron a una solución de ácido láctico 6 mM. Las células NP en el grupo ácido se dividieron adicionalmente en tres grupos: (1) Grupo en blanco: sin transfección; (2) grupo NC: células transfectadas con plásmido vector vacío; (3) grupo sh-POSTN: células transfectadas con plásmido sh-POSTN para reducir el nivel de expresión de POSTN. Se realizó una PCR cuantitativa en tiempo real (qRT-PCR) y una transferencia Western para evaluar la expresión de POSTN en los niveles de ARNm y proteína. Se utilizó CCK8 para evaluar la supervivencia celular. Además, se realizó una transferencia Western para examinar las proteínas relacionadas con los canales iónicos sensibles al ácido (ASIC). La piroptosis se detectó mediante ELISA y Western blot. El nivel de expresión de POSTN aumentó significativamente en células NP en ambiente ácido. La eliminación de la expresión de POSTN promovió la supervivencia de las células NP en un ambiente ácido y redujo los niveles de proteína de ASIC3 y ASIC1a en las células NP. Además, la eliminación de la expresión de POSTN disminuyó la proporción de piroptosis de las células NP y los niveles de citocinas proinflamatorias interleucina (IL) - 1β e IL-18. Los niveles de proteínas relacionadas con la piroptosis NLRP3, ASC, Caspasa-1 escindida y GSDMD escindida también se vieron afectados por la disminución de la expresión de POSTN. El ambiente ácido extracelular creado por la solución de ácido láctico activó la caspasa-1 inducida por vesículas inflamatorias NLRP3 para involucrarse en la piroptosis de las células NP mediante la regulación positiva de la expresión de POSTN.

Clinical manifestation and treatment strategy of intervertebral space infection after radiofrequency ablation of lumbar nucleus pulposus / 中国骨伤

OBJECTIVE@#To study the clinical manifestations and treatment of intervertebral space infection after percutaneous lumbar radiofrequency ablation of nucleus pulposus.@*METHODS@#A retrospective analysis was performed of 496 patients who underwent percutaneous lumbar disc decompression using low-temperature plasma radiofrequency ablation nucleus pulposus from June 2009 to June 2019. Six patients had lumbar infection, and the infection rate was 1.21%. All patients were male, ranging in age from 20 to 61 years old. Three patients underwent single segment radiofrequency ablation, two patients underwent dual segments ablation;and one patient underwent three segment ablation, totaling 10 intervertebral discs. One patient was complicated with type 2 diabetes before operation. The interval between infection occurrence ranged from 21 to 65 days.@*RESULTS@#All 6 patients were followed up, and the duration ranged from 18 to 40 months, with an average of 24 months. Among them, 2 patients presented with symptoms of low back pain accompanied by fever, and imaging examination showed intervertebral space infection accompanied by abscess. In addition, 4 patients experienced low back pain but no fever, and MRI showed abnormal signals of the infected intervertebral endplate or vertebral body. One patient showed staphylococcus aureus in blood culture, while the remaining 5 patients showed negative bacterial culture. All the patients were treated with antibiotics after diagnosis. Four patients were treated with conservative management to control infection;1 patient was treated with debridement of posterior lumbar infection focus, and 1 patient was treated with debridement of posterior lumbar infection focus combined with interbody fusion and internal fixation.@*CONCLUSION@#The occurrence of intervertebral space infection during lumbar radiofrequency ablation nucleoplasty should be given sufficient attention. Strict aseptic technique, avoiding repeated multi segment puncture, realizing early detection and treatment, and selecting appropriate treatment methods according to the severity of infection is the guarantee of achieving curative effect.

Aucubin combined with ADSCs-exos protects TBHP-induced nucleus pulposus cells via TLR4/NF-κB pathway / 中国中药杂志

This paper aims to investigate the effects and mechanisms of adipose-derived stem cells-exosomes(ADSCs-exos) toge-ther with aucubin in protecting human-derived nucleus pulposus cells(NPCs) from inflammatory injury, senescence, and apoptosis. The tert-butyl hydroperoxide(TBHP)-induced NPCs were assigned into normal, model, aucubin, ADSCs-exos, and aucubin+ADSCs-exos groups. The cell viability was examined by cell counting kit-8(CCK-8), cell proliferation by EdU staining, cell senescence by senescence-associated-β-galactosidase(SA-β-Gal), and cell cycle and apoptosis by flow cytometry. Enzyme-linked immunosorbent assay was employed to examine the expression of interleukin-1β(IL-1β), IL-10, and tumor necrosis factor-α(TNF-α). Real-time fluorescence quantitative PCR and Western blot were employed to determine the mRNA and protein levels of aggregated proteoglycan(aggrecan), type Ⅱ collagen alpha 1(COL2A1), Toll-like receptor 4(TLR4), and nuclear factor-kappa B(NF-κB). The results showed that compared with the model group, the aucubin or ADSCs-exos group showed enhanced viability and proliferation of NPCs, decreased proportion of G_0/G_1 phase cells, increased proportion of S phase cells, reduced apoptosis and proportion of cells in senescence, lowered IL-1β and TNF-α levels, elevated IL-10 level, down-regulated mRNA and protein levels of TLR4 and NF-κB, and up-regulated mRNA and protein levels of aggrecan and COL2A1. Compared with the aucubin or ADSCs-exos group, the aucubin+ADSCs-exos combination further increased the viability and proliferation of NPCs, decreased the proportion of G_0/G_1 phase cells, increased the proportion of S phase cells, reduced the apoptosis and proportion of cells in senescence, lowered the IL-1β and TNF-α levels, elevated the IL-10 level, down-regulated the mRNA and protein levels of TLR4 and NF-κB, and up-regulated the mRNA and protein levels of aggrecan and COL2A1. In summary, both aucubin and ADSCs-exos could exert protective effects by inhibiting inflammatory responses, reducing apoptosis and senescence of NPCs, improving cell viability and proliferation as well as extracellular matrix synthesis, which may be associated with the inhibition of TLR4/NF-κB signaling pathway activation. The combination of both plays a synergistic role in the protective effects.

Analgesic Effects of Two Types of Spinal Manipulation in Acute Lumbar Radiculopathy Model Rats / 中国结合医学杂志

OBJECTIVE@#To compare the analgesic effects of two types of spinal manipulation (SM) in acute lumbar radiculopathy (ALR) model rats induced by self-transplantation of autologous nucleus pulposus (ANP), and clarify the therapeutic mechanism.@*METHODS@#Totally 108 male Sprague-Dawley rats were randomly divided into 6 groups by a random number table (18 rats in each group), including a blank group with no interference, a sham operation group with a surgery by making a local soft tissue incision on the left side of L5-6 vertebral segment, a model group with ALR of L5 extraforaminal nerve by ANP self-transplantation without other interference, a sham manipulation (SMA) group with simulating physical rotation, as well as a mobilization (MOB) group with simulating low-velocity and variable-amplitude rotation and a manipulation (MAN) group with simulating high-velocity and low-amplitude rotation. The interventions in SMA, MOB, and MAN groups started 1 day after modeling followed by another 5 treatments at days 3, 5, 8, 10 and 12. Rats in the other 3 groups did not receive any special intervention. Behavioral pain tests of 50% mechanical pain withdrawal threshold (50% PWT) and paw withdrawal latency (PWL) were conducted 1 day before operation followed by another 10 tests on days 1-7, 10, 12 and 14. Immunohistochemical expression of nitric oxide synthase (NOS) was investigated on days 5 and 12 after operation.@*RESULTS@#After 3 experimental SM interventions, 50% PWT and PWL were higher in the MAN group than the SMA group on days 6 and 7, and higher on days 10, 12 and 14 postoperatively (P<0.05 or P<0.01), while the same indices were significantly higher in the MOB group than MAN group on days 1-4 (P<0.05 or P<0.01). The expression of NOS was lower in the MAN and MOB groups than SMA group on day 12 postoperatively (P<0.01).@*CONCLUSIONS@#Both manipulation and mobilization produced better results than sham interference in relieving pain by reducing neuroinflammation possibly. At the early period, compared with manipulation, mobilization presented less sensitive response to pain until later visit. SM may inhibit the overexpression of NOS, thereby alleviating severe radiculopathy.

Research progress in mechanism of Chinese herbal compounds and monomers in delaying lumbar intervertebral disc degeneration / 中国中药杂志

Traditional Chinese medicine has unique advantages in the treatment of degenerative bone and joint diseases, and its widely used in clinical practice. In recent years, many scholars have conducted a large number of basic studies on the delay of intervertebral disc degeneration by herbal compound and monomeric components from different perspectives. In order to further elucidate its mechanism of action, this paper summarizes the in vivo and in vitro experimental studies conducted at the level of both herbal compound and single components, respectively, in order to provide references for the basic research on the treatment of lumbar intervertebral disc degeneration by Chinese medicine. A summary shows that commonly used herbal compound prescriptions include both classical prescriptions such as Duhuo Jisheng Decoction, as well as clinical experience prescriptions such as Yiqi Huoxue Recipe. Angelicae Sinensis Radix, Chuanxiong Rhizoma, Rehmanniae Radix Praeparata, Achyranthis Bidentatae Radix, and Eucommiae Cortex were used most frequently. Tonic for deficiency and blood stasis activators were used most frequently. The most utilized monomeric components include icariin, ginsenoside Re, salvianolic acid B and aucubin. The main molecular mechanisms by which herbal compound and monomeric components delay of lumbar intervertebral disc degeneration include improving the intervertebral disc microenvironment, promoting the synthesis of aggregated proteoglycans and type Ⅱ collagen in the intervertebral disc, reducing the degradation of the extracellular matrix, and inhibiting apoptosis in the nucleus pulposus cells, etc. The main signaling pathways involved include Wnt/β-catenin signaling pathway, MAPK-related signaling pathway, mTOR signaling pathway, Fas/FasL signaling pathway, PI3 K/Akt signaling pathway, NF-κB signaling pathway, JAK/STAT signaling pathway, and hedgehog signaling pathway, etc.

Pharmacological inhibition of mTORC1 activity protects against inflammation-induced apoptosis of nucleus pulposus cells

Lumbar disc herniation is a common disease characterized by the degeneration of intervertebral discs (IVDs), accompanied by imbalance of metabolic and inflammatory homeostasis. Current studies establish that IVD degeneration is induced by increased apoptosis of nucleus pulposus (NP) cells. However, the underlying mechanisms of NP cell survival/apoptosis are not well elucidated. Here, we reveal a novel mechanism by which mTORC1 signaling controls NP cell survival through regulating metabolic homeostasis. We demonstrated that hyperactivated mTORC1 activity induced by inflammatory cytokines engenders the apoptosis of NP cells, whereas pharmacological inhibition of mTORC1 activity promotes NP cell survival. Using an integrative approach spanning metabolomics and biochemical approaches, we showed that mTORC1 activation enhanced glucose metabolism and lactic acid production, and therefore caused NP cell apoptosis. Our study identified mTORC1 in NP cells as a novel target for IVD degeneration, and provided potential strategies for clinical intervention of lumbar disc herniation.

17β-estradiol inhibits interleukin-1β-induced rat nucleus pulposus cell apoptosis through the PI3K/Akt/mTOR signal pathway / 生理学报

The apoptosis of nucleus pulposus cells (NPCs) is the main cellular process of intervertebral disc degeneration (IVDD). Our previous studies showed that 17β-estradiol (E

Expression and clinical significance of receptor-interacting protein serine-threonine kinases 1 in the nucleus pulposus of patients with lumbar disc herniation / 中国骨伤

OBJECTIVE@#To investigate the expression and clinical significance of receptor interacting protein serine-threonine kinases 1 (RIPK1) in the nucleus pulposus of patients with lumbar disc herniation (LDH).@*METHODS@#Nucleus pulposus tissue specimens of 40 patients with LDH patients underwent surgical treatment from January 2016 to January 2018 as the case group, and nucleus pulposus tissue specimens of 30 patients with lumbar spine fracture underwent surgical treatment at the same time as the control group. The expression of RIPK1 mRNA and protein of receptor interaction were detected by polymerase chain reaction (PCR) and Western blot, respectively. The expression of RIPK1 protein in the nucleus pulposus were detected by immunohistochemical staining. The concentrations of RIPK1 and tumor necrosis factor-α (TNF-α) in nucleus pulposus were detected by ELISA method. The relationship between the concentrations of RIPK1, TNF-α in nucleus pulposus and the Pearce grade of LDH patients was analyzed by one-way ANOVA. The correlation between RIPK1 and TNF-α was analyzed by Pearson.@*RESULTS@#RIPK1 was weakly positively expressed in nucleus pulposus of control group, and RIPK1 protein was positively or strongly positively expressed in case group. The expression of RIPK1 mRNA in nucleus pulposus of case group was higher than that of control group (@*CONCLUSION@#The expression levels of RIPK1 mRNA and protein in the intervertebral disc tissues of LDH patients are higher than those of normal intervertebral disc tissues, and increased with the increase of Pearce grade, which may be an important factor involved in LDH inflammatory disease.

Simple nucleus pulposus removal for the treatment of prolapsed and displaced lumbar disc herniation / 中国骨伤

OBJECTIVE@#To explore the clinical effect of the simple nucleus pulposus removal and small incision interlaminar window in the treatment of prolapsed and displaced lumbar disc herniation.@*METHODS@#From February 2016 to February 2018, 35 patients with single-segment prolapse and displaced lumbar disc herniation were treated by the simple nucleus pulposus removal and small incision interlaminar window under general anesthesia. Among them, there were 21 males and 14 females;aged (42±17) years;27 cases of L@*RESULTS@#All the operations were successful and the operation time was 30 to 60 min with an average of 40 min, the intraoperative blood loss was 10 to 30 ml with an average of 20 ml. All the patients were followed up for 1 to 3 years with an average of 1.2 years. Thirty-five patients with low back pain and lower limb symptoms were significantly relieved or disappeared. According to modified Macnab standard, 29 cases obtained excellent results, 5 good, and 1 fair.@*CONCLUSION@#Applying the concept of minimally invasive operation, small incision interlaminar window and simple nucleus pulposus removal for the treatment of prolapsed and displaced lumbar disc herniation has the advantages of short operation time, definite curative effect, and less trauma. And it is a safe and effective surgical method under the premise of strict control of the indications.

Vértebra limbus, rara causa de dolor lumbar en jóvenes / Limbus vertebra as a rare cause of lumbar pain in young people

RESUMEN La vértebra limbus es una rara condición poco descrita en la literatura médica. Se caracteriza por una herniación marginal intracorporal del núcleo pulposo que resulta en la separación de un fragmento óseo de forma triangular. Usualmente se presenta en niños o adolescentes, principalmente en la columna lumbar, y ocasiona dolor que, en la mayoría de los casos, mejora con el tratamiento con antiinflamatorios.

A B S T R A C T The limbus vertebra is a rare condition poorly described in the medical literature. Marginal intrabody herniation of the nucleus pulposus resulting in the separation of a triangular bone fragment. It usually occurs in children or adolescents mainly in the lumbar spine and causes pain that in most cases improves with treatment with anti-inflammatories.

Ginsenoside Rd inhibits IL-1ß-induced inflammation and degradation of intervertebral disc chondrocytes by increasing IL1RAP ubiquitination

Many compounds of ginsenosides show anti-inflammatory properties. However, their anti-inflammatory effects in intervertebral chondrocytes in the presence of inflammatory factors have never been shown. Increased levels of pro-inflammatory cytokines are generally associated with the degradation and death of chondrocytes; therefore, finding an effective and nontoxic substance that attenuates the inflammation is worthwhile. In this study, chondrocytes were isolated from the nucleus pulposus tissues, and the cells were treated with ginsenoside compounds and IL-1β, alone and in combination. Cell viability and death rate were assessed by CCK-8 and flow cytometry methods, respectively. PCR, western blot, and immunoprecipitation assays were performed to determine the mRNA and protein expression, and the interactions between proteins, respectively. Monomeric component of ginsenoside Rd had no toxicity at the tested range of concentrations. Furthermore, Rd suppressed the inflammatory response of chondrocytes to interleukin (IL)-1β by suppressing the increase in IL-1β, tumor necrosis factor (TNF)-α, IL-6, COX-2, and inducible nitric oxide synthase (iNOS) expression, and retarding IL-1β-induced degradation of chondrocytes by improving cell proliferation characteristics and expression of aggrecan and COL2A1. These protective effects of Rd were associated with ubiquitination of IL-1 receptor accessory protein (IL1RAP), blocking the stimulation of IL-1β to NF-κB. Bioinformatics analysis showed that NEDD4, CBL, CBLB, CBLC, and ITCH most likely target IL1RAP. Rd increased intracellular ITCH level and the amount of ITCH attaching to IL1RAP. Thus, IL1RAP ubiquitination promoted by Rd is likely to occur by up-regulation of ITCH. In summary, Rd inhibited IL-1β-induced inflammation and degradation of intervertebral disc chondrocytes by increasing IL1RAP ubiquitination.

Provável extrusão de núcleo pulposo aguda e não compressiva em um cão: relato de caso / Probable acute non-compressive nucleus pulposus extrusion in a dog: case report

A extrusão discal aguda e não compressiva é caracterizada pela extrusão de caráter agudo/hiperagudo e não compressivo do núcleo pulposo de um disco intervertebral não degenerado. Pode ser chamada de hérnia de disco de baixo volume e alta velocidade ou explosões discais e geralmente está associado a exercícios intensos ou episódios traumáticos. O núcleo pulposo é fortemente forçado através de uma pequena fissura no ânulo fibroso dorsal, provocando uma contusão espinhal. Este relato tem como objetivo apresentar um caso de provável extrusão aguda de núcleo pulposo não compressiva. Foi atendido um cão macho, três anos e seis meses de idade, maltês, pesando 4,1kg. Como queixa principal, o proprietário relatou dificuldade locomotora e dor à manipulação há um dia, sem histórico de trauma. Foi constatada paraparesia não ambulatória de início agudo com ausência de propriocepção e dor superficial em membros pélvicos e dor à palpação epaxial da coluna toracolombar. A ressonância magnética (RM) evidenciou extensa área de hipersinal em segmento toracolombar da medula espinhal, sem sinais de compressão medular e de atenuação da intensidade do núcleo pulposo do disco intervertebral L1-L2. Foi feito diagnóstico presuntivo de mielopatia focal não compressiva com edema medular de todo segmento toracolombar, característico de uma extrusão aguda de núcleo pulposo não compressiva. Foi prescrito tratamento com anti-inflamatório esteroidal, analgésico, repouso absoluto e protocolo de reabilitação com acupuntura e fisioterapia. Após sete dias de tratamento, o animal recuperou a sensibilidade dolorosa superficial em membros pélvicos e evoluiu para paraparesia ambulatória. Os resultados deste relato sugerem que a RM pode ser útil para fazer um diagnóstico presuntivo em cães com histórico e sinais clínicos compatíveis. Além disso, o tratamento conservativo em extrusões discais não compressivas é preconizado e o paciente pode apresentar boa recuperação.(AU)

Acute and non-compressive disc extrusion is characterized by the acute character of extrusion of the nucleus pulposus without real compression of the spine. It has been called low-volume and high speed disc herniation or disc explosions, and usually is associated with an intense exercise or traumatic episode. This report aims to present a case of an acute extrusion of nucleus pulposus with no compression of the spinal cord. A 3.5 year-old male dog of the Maltes breed, weighing 4.1kg was presented at the Veterinary Hospital with locomotion disorders and pain during manipulation with no history of trauma. At the physical and neurological examination, non-ambulatory paraparesis of acute onset with absence of proprioception and superficial pain in hind limbs was found, as well as pain on palpation of epaxial thoracolumbar spine. Magnetic resonance imaging (MRI) showed extensive hyper intense area in the thoracolumbar spinal cord, with no signs of spinal cord compression, and decreased intensity of the nucleus pulposus of the L1-L2 intervertebral disc. Additionally, a spinal cord edema in all thoracolumbar segments was seen that is characteristic of an acute extrusion of non-compressive nucleus pulposus. A presumptive diagnosis of non-compressive myelopathy was assumed. The dog was prescribed steroidal anti-inflammatory, analgesic, absolute rest and rehabilitation protocol, including acupuncture and physiotherapy. The patient recovered superficial pain in the pelvic limbs and evolved into ambulatory paraparesis after seven days. The results of this report suggested that MRI can be useful for making a presumptive diagnosis in dogs with a history of compatible clinical signs. Moreover, the conservative treatment in non-compressive disc extrusions can be feasible.(AU)

Effect of Static Load on the Nucleus Pulposus of Rabbit Intervertebral Disc Motion Segment in Ex vivo Organ Culture / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The development of mechanically active culture systems helps increase the understanding of the role of mechanical stress in intervertebral disc (IVD) degeneration. Motion segment cultures allow for preservation of the native IVD structure, and adjacent vertebral bodies facilitate the application and control of mechanical loads. The purpose of this study was to establish loading and organ culture methods for rabbit IVD motion segments to study the effect of static load on the whole disc organ.</p><p><b>METHODS</b>IVD motion segments were harvested from rabbit lumbar spines and cultured in no-loading 6-well plates (control conditions) or custom-made apparatuses under a constant, compressive load (3 kg, 0.5 MPa) for up to 14 days. Tissue integrity, matrix synthesis, and the matrix gene expression profile were assessed after 3, 7, and 14 days of culturing and compared with those of fresh tissues.</p><p><b>RESULTS</b>The results showed that ex vivo culturing of motion segments preserved tissue integrity under no-loading conditions for 14 days whereas the static load gradually destroyed the morphology after 3 days. Proteoglycan contents were decreased under both conditions, with a more obvious decrease under static load, and proteoglycan gene expression was also downregulated. However, under static load, immunohistochemical staining intensity and collagen Type II alpha 1 (COL2A1) gene expression were significantly enhanced (61.54 ± 5.91, P = 0.035) and upregulated (1.195 ± 0.040, P = 0.000), respectively, compared with those in the controls (P < 0.05). In contrast, under constant compression, these trends were reversed. Our initial results indicated that short-term static load stimulated the synthesis of collagen Type II alpha 1; however, sustained constant compression led to progressive degeneration and specifically to a decreased proteoglycan content.</p><p><b>CONCLUSIONS</b>A loading and organ culture system for ex vivo rabbit IVD motion segments was developed. Using this system, we were able to study the effects of mechanical stimulation on the biology of IVDs, as well as the pathomechanics of IVD degeneration.</p>

Effect of microRNA-21 on the proliferation of human degenerated nucleus pulposus by targeting programmed cell death 4

This study aims to explore the effect of microRNA-21 (miR-21) on the proliferation of human degenerated nucleus pulposus (NP) by targeting programmed cell death 4 (PDCD4) tumor suppressor. NP tissues were collected from 20 intervertebral disc degeneration (IDD) patients, and from 5 patients with traumatic spine fracture. MiR-21 expressions were tested. NP cells from IDD patients were collected and divided into blank control group, negative control group (transfected with miR-21 negative sequences), miR-21 inhibitor group (transfected with miR-21 inhibitors), miR-21 mimics group (transfected with miR-21 mimics) and PDCD4 siRNA group (transfected with PDCD4 siRNAs). Cell growth was estimated by Cell Counting Kit-8; PDCD4, MMP-2,MMP-9 mRNA expressions were evaluated by qRT-PCR; PDCD4, c-Jun and p-c-Jun expressions were tested using western blot. In IDD patients, the expressions of miR-21 and PDCD4 mRNA were respectively elevated and decreased (both P<0.05). The miR-21 expressions were positively correlated with Pfirrmann grades, but negatively correlated with PDCD4 mRNA (both P<0.001). In miR-21 inhibitor group, cell growth, MMP-2 and MMP-9 mRNA expressions, and p-c-Jun protein expressions were significantly lower, while PDCD4 mRNA and protein expressions were higher than the other groups (all P<0.05). These expressions in the PDCD4 siRNA and miR-21 mimics groups was inverted compared to that in the miR-21 inhibitor group (all P<0.05). MiR-21 could promote the proliferation of human degenerated NP cells by targeting PDCD4, increasing phosphorylation of c-Jun protein, and activating AP-1-dependent transcription of MMPs, indicating that miR-21 may be a crucial biomarker in the pathogenesis of IDD.