Lactoferricin mediates anabolic and anti-catabolic effects in the intervertebral disc

Stress-Activated Protein Kinases in Intervertebral Disc Degeneration: Unraveling the Impact of JNK and p38 MAPK

Intervertebral disc degeneration (IDD) is a major cause of lower back pain. The pathophysiological development of IDD is closely related to the stimulation of various stressors, including proinflammatory cytokines, abnormal mechanical stress, oxidative stress, metabolic abnormalities, and DNA damage, among others. These factors prevent normal intervertebral disc (IVD) development, reduce the number of IVD cells, and induce senescence and apoptosis. Stress-activated protein kinases (SAPKs), particularly, c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK), control cell signaling in response to cellular stress. Previous studies have shown that these proteins are highly expressed in degenerated IVD tissues and are involved in complex biological signal-regulated processes. Therefore, we summarize the research reports on IDD related to JNK and p38 MAPK. Their structure, function, and signal regulation mechanisms are comprehensively and systematically described and potential therapeutic targets are proposed. This work could provide a reference for future research and help improve molecular therapeutic strategies for IDD.

Innovative Biological Treatment Methods for Degenerative Disc Disease

Low back pain is the leading cause of work absences and years lived with disability, and it is often associated with degenerative disc disease. In recent years, biological treatment approaches such as the use of growth factors, cell injections, annulus fibrosus (AF) repair, nucleus pulposus replacement, and tissue-engineered discs have been explored as means for preventing or reversing degenerative disc disease. Both animal and clinical studies have shown promising results for cell-based therapy on the grounds of its regenerative potential. Clinical data also indicate that stem cell injection is safe when appropriately performed, albeit its long-term safety and efficacy are yet to be explored. Numerous challenges also remain to be overcome, such as isolating, differentiating, and preconditioning the disc cells, as well as managing the nutrient-deficient and oxygen-deficient micromilieu of the intervertebral disc (IVD). AF repair methods including devices used in clinical trials have shown success in decreasing reherniation rates and improving overall clinical outcomes. In addition, recent studies that combined AF repair and nucleus pulposus replacement have shown improved biomechanical stability in IVDs after the combined treatment. Tissue-engineered IVDs for total disc replacement are still being developed, and future studies are necessary to overcome the challenges in their delivery, efficacy, and safety.

Growing a backbone - functional biomaterials and structures for intervertebral disc (IVD) repair and regeneration: challenges, innovations, and future directions

Back pain and associated maladies can account for an immense amount of healthcare cost and loss of productivity in the workplace. In particular, spine related injuries in the US affect upwards of 5.7 million people each year. The degenerative disc disease treatment almost always arises due to a clinical presentation of pain and/or discomfort. Preferred conservative treatment modalities include the use of non-steroidal anti-inflammatory medications, physical therapy, massage, acupuncture, chiropractic work, and dietary supplements like glucosamine and chondroitin. Artificial disc replacement, also known as total disc replacement, is a treatment alternative to spinal fusion. The goal of artificial disc prostheses is to replicate the normal biomechanics of the spine segment, thereby preventing further damage to neighboring sections. Artificial functional disc replacement through permanent metal and polymer-based components continues to evolve, but is far from recapitulating native disc structure and function, and suffers from the risk of unsuccessful tissue integration and device failure. Tissue engineering and regenerative medicine strategies combine novel material structures, bioactive factors and stem cells alone or in combination to repair and regenerate the IVD. These efforts are at very early stages and a more in-depth understanding of IVD metabolism and cellular environment will also lead to a clearer understanding of the native environment which the tissue engineering scaffold should mimic. The current review focusses on the strategies for a successful regenerative scaffold for IVD regeneration and the need for defining new materials, environments, and factors that are so finely tuned in the healthy human intervertebral disc in hopes of treating such a prevalent degenerative process.

Absence of VEGFR-1/Flt-1 signaling pathway in mice results in insensitivity to discogenic low back pain in an established disc injury mouse model

Although degenerative disc disease (DDD) and related low back pain (LBP) are growing public health problems, the underlying disease mechanisms remain unclear. An increase in the vascular endothelial growth factor (VEGF) levels in DDD has been reported. This study aimed to examine the role of VEGF receptors (VEGFRs) in DDD, using a mouse model of DDD. Progressive DDD was induced by anterior stabbing of lumbar intervertebral discs in wild type (WT) and VEGFR-1 tyrosine-kinase deficient mice (vegfr-1TK-/- ). Pain assessments were performed weekly for 12 weeks. Histological and immunohistochemical assessments were made for discs, dorsal root ganglions, and spinal cord. Both vegfr-1TK-/- and WT mice presented with similar pathological changes in discs with an increased expression of inflammatory cytokines and matrix-degrading enzymes. Despite the similar pathological patterns, vegfr-1TK-/- mice showed insensitivity to pain compared with WT mice. This insensitivity to discogenic pain was related to lower levels of pain factors in the discs and peripheral sensory neurons and lower spinal glial activation in the vegfr-1TK- /- mice than in the WT mice. Exogenous stimulation of bovine disc cells with VEGF increased inflammatory and cartilage degrading enzyme. Silencing vegfr-1 by small-interfering-RNA decreased VEGF-induced expression of pain markers, while silencing vegfr-2 decreased VEGF-induced expression of inflammatory and metabolic markers without changing pain markers. This suggests the involvement of VEGFR-1 signaling specifically in pain transmission. Collectively, our results indicate that the VEGF signaling is involved in DDD. Particularly, VEGFR-1 is critical for discogenic LBP transmission independent of the degree of disc pathology.

MicroRNA-181a exerts anti-inflammatory effects via inhibition of the ERK pathway in mice with intervertebral disc degeneration

Enzymatic decomposition of extracellular matrix and possibly local inflammation may cause intervertebral disc degeneration (IDD). MicroRNAs have been reported to correlate with the development of IDD. In this experiment, we aim at finding out the role of miR-181a in the inflammation of IDD and the underlying mechanism. The targeting relationship between miR-181a and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) was verified. Following the establishment of IDD mouse models, disc height index (DHI) and the change of DHI (%DHI) were measured. The functional role of miR-181a in IDD was determined using ectopic expression and depletion and reporter assay experiments. Expression of miR-181a, TRAIL, extracellular signal-regulated kinase (ERK) pathway-related genes and inflammatory factors was evaluated. Also, the expression of collagen I and collagen II was observed. miR-181a directly targeted TRAIL. IDD mice exhibited significant degeneration of the intervertebral disc. miR-181a was downregulated while TRAIL was upregulated in mice with IDD. miR-181a upregulation and the ERK pathway inhibition could reduce expression of TRAIL, ERK pathway-related genes, inflammatory factors, and collagen I, but promote collagen II expression. Our results reveal that upregulation of miR-181a protects against inflammatory response by inactivating the ERK pathway via suppression of TRAIL in IDD mice. These results point to miR-181a as a potential therapeutic target for the clinical management of IDD.

Emission and Cytotoxicity of Surgical Smoke: Cholesta-3,5-Diene Released from Pyrolysis of Prostate Tissue

Respiratory and lung irritants can be a by-product of the surgical pyrolysis of human tissues. Seven prostate tissues were collected during the transurethral resection of a prostate (TURP). Tissue samples, pyrolyzed in a pyrolysis sampling system, were collected and analyzed for the characterization of aerosols in the surgical smoke. In the pyrolyzed particulate matter (PM) from the TURP, Cholestra-3,5-diene was identified as the most dominant component along with 9-methylanthracene, hentriacontane, and dotriacontane based on the mass fragment structure determined using gas chromatography-mass spectrometry (GC-MS). As a molecular marker, Cholesta-3,5-diene can be associated with a cytotoxic in primary human oral keratinocytes (HOK). In this research, the presence of Cholestra-3,5-diene is reported for the first time as a by-product of surgical pyrolysis.

Cell type-specific effects of Notch signaling activation on intervertebral discs: Implications for intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is the major cause of back pain. Notch signaling is activated in annulus fibrosus (AF) and nucleus pulposus (NP) tissues of degenerated IVDs, and induced by IL1-β and TNF-α in NP cells. However, the role of Notch activatin in the pathogenesis of IVD degeneration is largely unknown. In this study, we overexpressed the Notch1 intracellular domain (NICD1) in AF, NP, and chondrogenic ATDC5 cells via adenoviruses. Overexpression of NICD1 activated transcription of Notch signaling target genes in AF, NP, and ATDC5 cells, and caused cell type-specific effects on expression of matrix anabolic and catabolic genes. Activation of Notch signaling promoted expression of matrix catabolic genes and inhibited expression of matrix anabolic genes in both AF and ATDC5 cells, whereas its activation suppressed expression of matrix catabolic genes (including Mmp3, Mmp13, Adamts4, and Adamts5) and attenuated TNF-α and inflammatory macrophage-induced Mmp13 expression in NP cells. Consistently, sustained activation of Notch1 signaling in postnatal IVDs in mice severely disrupted growth plate and endplate cartilage tissues, but did not overly affect NP tissues. Together, these data indicated that activation of Notch signaling exerted differential and cell type-specific effects in intervertebral discs, and specific Notch signaling regulation may be considered during the treatment of IVD degeneration.

Collagen-derived N-acetylated proline-glycine-proline upregulates the expression of pro-inflammatory cytokines and extracellular matrix proteases in nucleus pulposus cells via the NF-κB and MAPK signaling pathways

N-acetylated proline-glycine-proline (N-Ac-PGP) is a chemokine involved in inflammatory diseases and is found to accumulate in degenerative discs. N-Ac-PGP has been demonstrated to have a pro-inflammatory effect on human cartilage endplate stem cells. However, the effect of N-Ac-PGP on human intervertebral disc cells, especially nucleus pulposus (NP) cells, remains unknown. The purpose of this study was to investigate the effect of N-Ac-PGP on the expression of pro-inflammatory factors and extracellular matrix (ECM) proteases in NP cells and the molecular mechanism underlying this effect. Therefore, Milliplex assays were used to detect the levels of various inflammatory cytokines in conditioned culture medium of NP cells treated with N-Ac-PGP, including interleukin-1β (IL-1β), IL-6, IL-17, tumor necrosis factor-α (TNF-α) and C-C motif ligand 2 (CCL2). RT-qPCR was also used to determine the expression of pro-inflammatory cytokines and ECM proteases in the NP cells treated with N-Ac-PGP. Moreover, the role of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways in mediating the effect of N-Ac-PGP on the phenotype of NP cells was investigated using specific signaling inhibitors. Milliplex assays showed that NP cells treated with N-Ac-PGP (10 and 100 µg/ml) secreted higher levels of IL-1β, IL-6, IL-17, TNF-α and CCL2 compared with the control. RT-qPCR assays showed that NP cells treated with N-Ac-PGP (100 µg/ml) had markedly upregulated expression of matrix metalloproteinase 3 (MMP3), MMP13, a disintegrin and metalloproteinase with thrombospondin motif 4 (ADAMTS4), ADAMTS5, IL-6, CCL-2, CCL-5 and C-X-C motif chemokine ligand 10 (CXCL10). Moreover, N-Ac-PGP was shown to activate the MAPK and NF-κB signaling pathways in NP cells. MAPK and NF-κB signaling inhibitors suppressed the upregulation of proteases and pro-inflammatory cytokines in NP cells treated with N-Ac-PGP. In conclusion, N-Ac-PGP induces the expression of pro-inflammatory cytokines and matrix catabolic enzymes in NP cells via the NF-κB and MAPK signaling pathways. N-Ac-PGP is a novel therapeutic target for intervertebral disc degeneration.

Coumestrol Counteracts Interleukin-1β-Induced Catabolic Effects by Suppressing Inflammation in Primary Rat Chondrocytes

In the present study, we investigated the anti-catabolic effects of coumestrol, a phytoestrogen derived from herbal plants, against interleukin-1β-induced cartilage degeneration in primary rat chondrocytes and articular cartilage. Coumestrol did not affect the viability of human normal oral keratinocytes and primary rat chondrocytes treated for 24 h and 21 days, respectively. Although coumestrol did not significantly increase the proteoglycan contents in long-term culture, it abolished the interleukin-1β-induced loss of proteoglycans in primary rat chondrocytes and knee articular cartilage. Furthermore, coumestrol suppressed the expression of matrix-degrading enzymes such as matrix metalloproteinase-13, -3, and -1 in primary rat chondrocytes stimulated with interleukin-1β. Moreover, the expression of catabolic factors such as nitric oxide synthase, cyclooxygenase-2, prostaglandin E₂, and inflammatory cytokines in interleukin-1β-stimulated primary rat chondrocytes was suppressed by coumestrol. In summary, these results indicate that coumestrol counteracts the catabolic effects induced by interleukin-1β through the suppression of inflammation. Therefore, based on its biological activity and safety profile, coumestrol could be used as a potential anti-catabolic biomaterial for osteoarthritis.

Adenovirus-mediated GDF-5 promotes the extracellular matrix expression in degenerative nucleus pulposus cells

OBJECTIVE

To construct a recombinant adenovirus vector-carrying human growth and differentiation factor-5 (GDF-5) gene, investigate the biological effects of adenovirus-mediated GDF-5 (Ad-GDF-5) on extracellular matrix (ECM) expression in human degenerative disc nucleus pulposus (NP) cells, and explore a candidate gene therapy method for intervertebral disc degeneration (IDD).

METHODS

Human NP cells of a degenerative disc were isolated, cultured, and infected with Ad-GDF-5 using the AdEasy-1 adenovirus vector system. On Days 3, 7, 14, and 21, the contents of the sulfated glycosaminoglycan (sGAG), deoxyribonucleic acid (DNA) and hydroxyproline (Hyp), synthesis of proteoglycan and collagen II, gene expression of collagen II and aggrecan, and NP cell proliferation were assessed.

RESULTS

The adenovirus was an effective vehicle for gene delivery with prolonged expression of GDF-5. Biochemical analysis revealed increased sGAG and Hyp contents in human NP cells infected by Ad-GDF-5 whereas there was no conspicuous change in basal medium (BM) or Ad-green fluorescent protein (GFP) groups. Only cells in the Ad-GDF-5 group promoted the production of ECM, as demonstrated by the secretion of proteoglycan and up-regulation of collagen II and aggrecan at both protein and mRNA levels. The NP cell proliferation was significantly promoted.

CONCLUSIONS

The data suggest that Ad-GDF-5 gene therapy is a potential treatment for IDD, which restores the functions of degenerative intervertebral disc through enhancing the ECM production of human NP cells.

Berberine-induced anticancer activities in FaDu head and neck squamous cell carcinoma cells

In the present study, we investigated berberine‑induced apoptosis and the signaling pathways underlying its activity in FaDu head and neck squamous cell carcinoma cells. Berberine did not affect the viability of primary human normal oral keratinocytes. In contrast, the cytotoxicity of berberine was significantly increased in FaDu cells stimulated with berberine for 24 h. Furthermore, berberine increased nuclear condensation and apoptosis rates in FaDu cells than those in untreated control cells. Berberine also induced the upregulation of apoptotic ligands, such as FasL and TNF-related apoptosis-inducing ligand, and triggered the activation of caspase-8, -7 and -3, and poly(ADP ribose) polymerase, characteristic of death receptor-dependent extrinsic apoptosis. Moreover, berberine activated the mitochondria‑dependent apoptotic signaling pathway by upregulating pro-apoptotic factors, such as Bax, Bad, Apaf-1, and the active form of caspase-9, and downregulating anti-apoptotic factors, such as Bcl-2 and Bcl-xL. In addition, berberine increased the expression of the tumor suppressor p53 in FaDu cells. The pan-caspase inhibitor Z-VAD-fmk suppressed the activation of caspase-3 and prevented cytotoxicity in FaDu cells treated with berberine. Interestingly, berberine suppressed cell migration through downregulation of vascular endothelial growth factor (VEGF), matrix metalloproteinase (MMP)-2, and MMP-9. Moreover, the phosphorylation of extracellular signal-regulated kinase (ERK1/2) and p38, components of the mitogen-activated protein kinase pathway that are associated with the expression of MMP and VEGF, was suppressed in FaDu cells treated with berberine for 24 h. Therefore, these data suggested that berberine exerted anticancer effects in FaDu cells through induction of apoptosis and suppression of migration. Berberine may have potential applications as a chemotherapeutic agent for the management of head and neck squamous carcinoma.

Biological Effects of the Herbal Plant-Derived Phytoestrogen Bavachin in Primary Rat Chondrocytes

The aim of this study was to examine the anabolic and anticatabolic functions of bavachin in primary rat chondrocytes. With bavachin treatment, chondrocytes survived for 21 d without cell proliferation, and the proteoglycan content and extracellular matrix increased. Short-term monolayer culture of chondrocytes showed that gene induction of both aggrecan and collagen type II, major extracellular matrix components, was significantly upregulated by bavachin. The expression and activities of cartilage-degrading enzymes such as matrix metalloproteinases and a disintegrin and metalloproteinase with thrombospondin motifs were inhibited significantly by bavachin, while tissue inhibitors of metalloprotease were significantly upregulated. Bavachin inhibits the expression of inducible nitric oxide synthase, a representative catabolic factor, and downregulated the expression of nitric oxide, cyclooxygenase-2, and prostaglandin E2 in a dose-dependent manner in chondrocytes. Our results suggest that the bavachin has anabolic and potent anticatabolic biological effects on chondrocytes, which may have considerable promise in treating articular cartilage degeneration in the future.

LIM mineralization protein-1 suppresses TNF-α induced intervertebral disc degeneration by maintaining nucleus pulposus extracellular matrix production and inhibiting matrix metalloproteinases expression

Imbalanced metabolism of Nucleus pulposus (NP) extracellular matrix (ECM) is closely correlated to Intervertebral Disc Degenerative Disease. LIM mineralization protein-1 (LMP-1) has been proven to induce sulfated glycosaminoglycan (sGAG) production in NP and have an anti-inflammatory effect in pre-osteoclast. However, whether it has any effect on the NP ECM production and degradation under inflammatory stimulation has not been studied. In the current study, a TNF-α induced cell model was established in vitro. Lentivirus encoding LMP-1 (LV-LMP-1) and short heparin LMP-1 (LV-shLMP-1) were constructed to overexpress and knockdown LMP-1 expression in NP cells. LMP-1 mRNA level was regulated in a dose-dependent manner after transfection. LV-LMP-1 increased whereas LV-shLMP-1 decreased collagen II, aggrecan, versican expression, and sGAG production. LV-LMP-1 abolished while LV-shLMP-1 aggravated TNF-α mediated down-regulation of the above matrix genes via ERK1/2 activation. Moreover, LV-LMP-1 abrogated TNF-α induced MMP-3 and MMP-13 expression via inhibiting p65 translocation and MMP-3 and MMP-13 promoter activity. These results indicated that LMP-1 had an ECM production maintenance effect under inflammatory stimulation. This effect was via up-regulation of matrix genes expression at least partially through ERK1/2 activation, and down-regulation of MMPs expression through NF-κB inhibition.

Effect of biphasic electrical current stimulation on IL-1β-stimulated annulus fibrosus cells using in vitro microcurrent generating chamber system

STUDY DESIGN

Human annulus fibrosus (AF) cells were stimulated in vitro with interleukin (IL)-1β and exposed to biphasic electrical currents.

OBJECTIVE

To identify the effect of biphasic electrical currents on the production of the extracellular matrix-modifying enzymes and inflammatory mediators in IL-1β-stimulated AF cells.

SUMMARY OF BACKGROUND DATA

Symptomatic disc degeneration is an important cause of chronic intractable lumbar pain and is associated with macrophage-mediated inflammation in the AF. The inflammatory reaction relationship has not been studied in the AF.

METHODS

Human AF cells were treated with 1 ng/mL IL-1β and cultured in a microcurrent generating chamber system. The levels of matrix metalloproteinase (MMP)-1, MMP-3, tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, IL-6, IL-8, vascular endothelial growth factor (VEGF), insulin-like growth factor, and nitric oxide (NO) were measured. Expression of cyclooxygenase 2 and type I collagen mRNA was analyzed.

RESULTS

Compared with unstimulated cells, IL-1β-stimulated AF cells produced significantly higher levels of MMP-1, MMP-3, IL-6, IL-8, NO, and VEGF, and lower levels of TIMP-1 and TIMP-2. Exposure to a 250-mV/mm field induced time-dependent increases in IL-6, NO, MMP-1, TIMP-1, VEGF, and insulin-like growth factor-1 production. The cells exposed to 500-mV/mm field produced significantly less MMP-1, TIMP-1, IL-6, and VEGF than unexposed cells (MMP-1, 17.2 ± 4.7 ng/mL vs. 27.3 ± 3.9 ng/mL, P< 0.05; TIMP-1, 12.4 ± 3.3 ng/mL vs. 22.3 ± 2.1 ng/mL, P< 0.02; IL-6, 2.5 ± 0.9 ng/mL vs. 6.39 ± 1.90 ng/mL, P< 0.05; and VEGF, 0.1 ± 0.04 ng/mL vs. 0.44 ± 0.15 ng/mL, P< 0.03). NO production was markedly increased at 500 mV/mm (P< 0.0001).

CONCLUSION

We showed that exposure of IL-1β-stimulated AF cells to a 500 mV/mm inhibited MMP-1, IL-6, VEGF, and TIMP-1 production. The results suggest that biphasic electrical current stimulation may have efficacy in diminishing symptomatic disc degeneration.

LEVEL OF EVIDENCE

N/A.

A current review of molecular mechanisms regarding osteoarthritis and pain

Osteoarthritis afflicts millions of individuals across the world resulting in impaired quality of life and increased health costs. To understand this disease, physicians have been studying risk factors, such as genetic predisposition, aging, obesity, and joint malalignment; however have been unable to conclusively determine the direct etiology. Current treatment options are short-term or ineffective and fail to address pathophysiological and biochemical mechanisms involved with cartilage degeneration and the induction of pain in arthritic joints. OA pain involves a complex integration of sensory, affective, and cognitive processes that integrate a variety of abnormal cellular mechanisms at both peripheral and central (spinal and supraspinal) levels of the nervous system Through studies examined by investigators, the role of growth factors and cytokines has increasingly become more relevant in examining their effects on articular cartilage homeostasis and the development of osteoarthritis and osteoarthritis-associated pain. Catabolic factors involved in both cartilage degradation in vitro and nociceptive stimulation include IL-1, IL-6, TNF-α, PGE2, FGF-2 and PKCδ, and pharmacologic inhibitors to these mediators, as well as compounds such as RSV and LfcinB, may potentially be used as biological treatments in the future. This review explores several biochemical mediators involved in OA and pain, and provides a framework for the understanding of potential biologic therapies in the treatment of degenerative joint disease in the future.

Lactoferricin mediates anti-inflammatory and anti-catabolic effects via inhibition of IL-1 and LPS activity in the intervertebral disc

The catabolic cytokine interleukin-1 (IL-1) and endotoxin lipopolysaccharide (LPS) are well-known inflammatory mediators involved in degenerative disc disease, and inhibitors of IL-1 and LPS may potentially be used to slow or prevent disc degeneration in vivo. Here, we elucidate the striking anti-catabolic and anti-inflammatory effects of bovine lactoferricin (LfcinB) in the intervertebral disc (IVD) via antagonism of both IL-1 and LPS-mediated catabolic activity using in vitro and ex vivo analyses. Specifically, we demonstrate the biological counteraction of LfcinB against IL-1 and LPS-mediated proteoglycan (PG) depletion, matrix-degrading enzyme production, and enzyme activity in long-term (alginate beads) and short-term (monolayer) culture models using bovine and human nucleus pulposus (NP) cells. LfcinB significantly attenuates the IL-1 and LPS-mediated suppression of PG production and synthesis, and thus restores PG accumulation and pericellular matrix formation. Simultaneously, LfcinB antagonizes catabolic factor mediated induction of multiple cartilage-degrading enzymes, including MMP-1, MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5, in bovine NP cells at both mRNA and protein levels. LfcinB also suppresses the catabolic factor-induced stimulation of oxidative and inflammatory factors such as iNOS, IL-6, and toll-like receptor-2 (TLR-2) and TLR-4. Finally, the ability of LfcinB to antagonize IL-1 and LPS-mediated suppression of PG is upheld in an en bloc intradiscal microinjection model followed by ex vivo organ culture using both mouse and rabbit IVD tissue, suggesting a potential therapeutic benefit of LfcinB on degenerative disc disease in the future.

Lactoferricin enhances BMP7-stimulated anabolic pathways in intervertebral disc cells

Bone-morphogenetic protein-7 (BMP7) is a well-known anabolic and anti-catabolic growth factor on intervertebral disc (IVD) matrix and cell homeostasis. Similarly, Lactoferricin B (LfcinB) has recently been shown to have pro-anabolic, anti-catabolic, anti-oxidative and/or anti-inflammatory effects in bovine disc cells in vitro. In this study, we investigated the potential benefits of using combined peptide therapy with LfcinB and BMP7 for intervertebral disc matrix repair and to understand cellular and signaling mechanisms controlled by these factors. We studied the effects of BMP7 and LfcinB as individual treatments and combined therapy on bovine nucleus pulposus (NP) cells by assessing proteoglycan (PG) accumulation and synthesis, and the gene expression of matrix protein aggrecan and transcription factor SOX-9. We also analyzed the role of Noggin, a BMP antagonist, in IVD tissue and examined its effect after stimulation with LfcinB. To understand the molecular mechanisms by which LfcinB synergizes with BMP7, we investigated the ERK-SP1 axis as a downstream intracellular signaling regulator involved in BMP7 and LfcinB-mediated activities. Treatment of bovine NP cells cultured in alginate with LfcinB plus BMP7 synergistically stimulates PG synthesis and accumulation in part by upregulation of aggrecan gene expression. The synergism results from LfcinB-mediated activation of Sp1 and SMAD signaling pathways by (i) phosphorylation of SMAD 1/5/8; (ii) downregulation of SMAD inhibitory factors [i.e., noggin and SMAD6 (inhibitory SMAD)]; and (iii) upregulation of SMAD4 (universal co-SMAD). These data indicate that LfcinB-suppression of Noggin may eliminate the negative feedback of BMP7, thereby maximizing biological activity of BMP7 and ultimately shifting homeostasis to a pro-anabolic state in disc cells. We propose that combination growth factor therapy using BMP7 and LfcinB may be beneficial for treatment of disc degeneration.

Cell signaling pathways related to pain receptors in the degenerated disk

Many of the causes of low back pain are still unknown; sufficient evidence indicates that both degenerative and mechanical change within the intervertebral disk (IVD) is a relevant factor. This article reviews intracellular signaling pathways related to pain receptors in the degenerated IVD. Several reports have demonstrated the number of nerve fibers in the IVD was increased in degenerated disks. In recent years, some groups have reported that an increase in nerve fibers is associated with the presence of inflammatory mediators and/or neurotrophins in the IVD. Cell signaling events, which are regulated by inflammatory mediators and neurotrophins, must be identified to clarify the mechanism underlying low back pain. Major intracellular signaling pathways (nuclear factor kappa β, mitogen-activated protein kinases, and Wnts) potentially play vital roles in mediating the molecular events responsible for the initiation and progression of IVD degeneration. These signaling pathways may represent therapeutic targets for the treatment of IVD degeneration and its associated back pain.

Molecular and genetic advances in the regeneration of the intervertebral disc

Background:

Owing to the debilitating nature of degenerative disc disease (DDD) and other spine pathologies, significant research has been performed with the goal of healing or regenerating the intervertebral disc (IVD). Structural complexity, coupled with low vascularity and cellularity, make IVD regeneration an extremely challenging task.

Methods:

Tissue engineering-based strategies utilize three components to enhance tissue regeneration; scaffold materials to guide cell growth, biomolecules to enhance cell migration and differentiation, and cells (autologous, or allogeneic) to initiate the process of tissue formation. Significant advances in IVD regeneration have been made utilizing these tissue engineering strategies.

Results:

The current literature demonstrates that members of the transforming growth factor beta (TGF-β) superfamily are efficacious in the regeneration of an anabolic response in the IVD and to facilitate chondrogenic differentiation. Gene therapy, though thwarted by safety concerns and the risk of ectopic transfection, has significant potential for a targeted and sustained regenerative response. Stem cells in combination with injectable, biocompatible, and biodegradable scaffolds in the form of hydrogels can differentiate into de novo IVD tissue and facilitate regeneration of the existing matrix. Therapies that address both anabolism and the inherent catabolic state of the IVD using either direct inhibitors or broad-spectrum inhibitors show extensive promise.

Conclusion:

This review article summarizes the genetic and molecular advances that promise to play an integral role in the development of new strategies to combat DDD and promote healing of injured discs.

Polyol pathway mediates enhanced degradation of extracellular matrix via p38 MAPK activation in intervertebral disc of diabetic rats

The aim of this study was to determine the significance of diabetes on degradation of intervertebral disc (IVD) extracellular matrix. Diabetic rats showed a significant increase in glucose and sorbitol contents in the IVD. The levels of aldose reductase, p38 and metalloproteinases, and degradation of metalloproteinase-derived aggrecan and type II collagen were increased, while tissue inhibitors of metalloproteinases levels were decreased in the IVD of diabetic rats. These changes were markedly affected by inhibition of aldose reductase or p38. Diabetes might contribute to enhanced matrix degradation in the IVD and the polyol pathway might mediate this process via p38 activation.

Bovine lactoferricin induces TIMP-3 via the ERK1/2-Sp1 axis in human articular chondrocytes

Bovine lactoferricin (LfcinB) is a heparan sulfate-binding peptide with multiple bioactivities. In human articular cartilage, LfcinB antagonizes interleukin-1 β (IL-1β) and fibroblast growth factor 2 (FGF-2) in proteoglycan metabolism, catabolic protease expression, and induction of pro-inflammatory mediators. LfcinB specifically activates ERK1/2, p38 and Akt, but whether these signaling pathways control the expression of LfcinB target genes remained unknown. In this report, we characterized a novel aspect of LfcinB-mediated genetic response in human articular chondrocytes, tissue inhibitor of metalloproteinase 3 (TIMP-3) induction. Inhibition of individual signaling pathways revealed that ERK1/2 functions as the major pathway in TIMP-3 expression, whereas Akt plays a minor role. Further investigation identified Sp1 as a critical transcriptional activator in TIMP-3 regulation, and Sp1 activity is modulated by ERK1/2, not Akt. Comparative quantification indicates that significant downregulation of TIMP-3 occurs in OA chondrocytes, suggesting a beneficial role of LfcinB in OA pathogenesis. Our results collectively provide new insights into the mechanism of action of LfcinB, and support the candidacy of LfcinB as a chondroprotective agent.

Toll-like receptor adaptor signaling molecule MyD88 on intervertebral disk homeostasis: in vitro, ex vivo studies

MyD88 is an adapter protein that links toll-like receptors (TLRs) and Interleukin-1 receptors (IL-1Rs) with downstream signaling molecules. The MyD88 has been found to be an essential mediator in the development of osteoarthritis in articular cartilage. However, the role of the MyD88 pathway has yet to be elucidated in the intervertebral disk (IVD). Using in vitro techniques, we analyzed the effect of MyD88 pathway-specific inhibition on the potent inflammatory and catabolic mediator LPS and IL-1 in bovine and human nucleus pulposus (NP) cells by assessing matrix-degrading enzyme expression, including matrix metalloproteases (MMPs) and a disintegrin-like and metalloprotease with thrombospondin motifs (ADAMTS family). We also analyzed inhibition of MyD88 in the regulation of inducible nitric oxide synthase and TLR-2. Finally, we used an ex vivo organ culture model to assess the effects of MyD88 inhibitor (MyD88i) on catabolic factor-induced disk degeneration in mice lumbar disks. In bovine NP cells, MyD88i potently antagonizes LPS- or IL-1-mediated induction of cartilage-degrading enzyme production, including MMP-1, MMP-13, ADAMTS-4, and ADAMTS-5. MyD88i also attenuates the LPS- or IL-1-mediated induction of iNOS and TLR-2 gene expression. Our ex vivo findings reveal inhibition of MyD88 via counteraction of IL-1-mediated proteoglycan depletion. The findings from this study demonstrate the potent anti-inflammatory and anti-catabolic effects of inhibition of MyD88 pathway inhibition on IVD homeostasis, suggesting a potential therapeutic benefit of a MyD88i in degenerative disk disease in the future.