TNF-alpha induces MMP2 gelatinase activity and MT1-MMP expression in an in vitro model of nucleus pulposus tissue degeneration

MMP-2 mediates local degradation and remodeling of collagen by annulus fibrosus cells of the intervertebral disc

INTRODUCTION

Degeneration of the intervertebral disc (IVD) is characterized by marked degradation and restructuring of the annulus fibrosus (AF). Although several matrix metalloproteinases (MMPs) have been found to be more prevalent in degenerate discs, their coordination and function within the context of the disease process are still not well understood. In this study, we sought to determine whether MMP-2 is associated with degenerative changes in the AF and to identify the manner by which AF cells use MMP-2.

METHODS

Two established animal models of disc degeneration, static compression and transannular needle puncture of rodent caudal discs, were examined for MMP-2 immunopositivity. With lentiviral transduction of an shRNA expression cassette, we screened and identified an effective shRNA sequence for generating stable RNA interference to silence MMP-2 expression in primary rat AF cells. Gelatin films were used to compare gelatinase activity and spatial patterns of degradation between transduced cells, and both noninfected and nonsense shRNA controls. The functional significance of MMP-2 was determined by assessing the ability for cells to remodel collagen gels.

RESULTS

Both static compression and 18-g annular puncture of rodent caudal discs stimulated an increase in MMP-2 activity with concurrent lamellar disorganization in the AF, whereas 22-g and 26-g needle injuries did not. To investigate the functional role of MMP-2, we established lentivirus-mediated RNAi to induce stable knockdown of transcript levels by as much as 88%, and protein levels by as much as 95% over a 10-day period. Culturing transduced cells on gelatin films confirmed that MMP-2 is the primary functional gelatinase in AF cells, and that MMP-2 is used locally in regions immediately around AF cells. In collagen gels, transduced cells demonstrated an inability to remodel collagen matrices.

CONCLUSIONS

Our study indicates that increases in MMP-2 observed in human degenerate discs are mirrored in experimentally induced degenerative changes in rodent animal models. AF cells appear to use MMP-2 in a very directed fashion for local matrix degradation and collagen remodeling. This suggests that MMP-2 may have a functionally significant role in the etiology of degenerative disc disease and could be a potential therapeutic target.

The effects of microenvironment in mesenchymal stem cell-based regeneration of intervertebral disc

BACKGROUND CONTEXT

Recent studies have demonstrated new therapeutic strategy using transplantation of mesenchymal stem cells (MSCs), especially bone marrow-derived MSCs (BM-MSCs), to preserve intervertebral disc (IVD) structure and functions. It is important to understand whether and how the MSCs survive and thrive in the hostile microenvironment of the degenerated IVD. Therefore, this review majorly examines how resident disc cells, hypoxia, low nutrition, acidic pH, mechanical loading, endogenous proteinases, and cytokines regulate the behavior of the exogenous MSCs.

PURPOSE

To review and summarize the effect of the microenvironment in biological characteristics of BM-MSCs for IVD regeneration; the presence of endogenous stem cells and the state of the art in the use of BM-MSCs to regenerate the IVD in vivo were also discussed.

STUDY DESIGN

Literature review.

METHODS

MEDLINE electronic database was used to search for articles concerning stem/progenitor cell isolation from the IVD, regulation of the components of microenvironment for MSCs, and MSC-based therapy for IVD degeneration. The search was limited to English language.

RESULTS

Stem cells are probably resident in the disc, but exogenous stem cells, especially BM-MSCs, are currently the most popular graft cells for IVD regeneration. The endogenous disc cells and the biochemical and biophysical components in the degenerating disc present a complicated microenvironment to regulate the transplanted BM-MSCs. Although MSCs regenerate the mildly degenerative disc effectively in the experimental and clinical trials, many underlying questions are in need of further investigation.

CONCLUSIONS

There has been a dramatic improvement in the understanding of potential MSC-based therapy for IVD regeneration. The use of MSCs for IVD degeneration is still at the stage of preclinical and Phase 1 studies. The effects of the disc microenvironment in MSCs survival and function should be closely studied for transferring MSC transplantation from bench to bedside successfully.

Gender differences in non-ischemic myocardial remodeling: are they due to estrogen modulation of cardiac mast cells and/or membrane type 1 matrix metalloproteinase

This review is focused on gender differences in cardiac remodeling secondary to sustained increases in cardiac volume (VO) and generated pressure (PO). Estrogen has been shown to favorably alter the course of VO-induced remodeling. That is, the VO-induced increased extracellular matrix proteolytic activity and mast cell degranulation responsible for the adverse cardiac remodeling in males and ovariectomized rodents do not occur in intact premenopausal females. While less is known regarding the mechanisms responsible for female cardioprotection in PO-induced stress, gender differences in remodeling have been reported indicating the ability of premenopausal females to adequately compensate. In view of the fact that, in male mice with PO, mast cells have been shown to play a role in the adverse remodeling suggests favorable estrogen modification of mast cell phenotype may also be responsible for cardioprotection in females with PO. Thus, while evidence is accumulating regarding premenopausal females being cardioprotected, there remains the need for in-depth studies to identify critical downstream molecular targets that are under the regulation of estrogen and relevant to cardiac remodeling. Such studies would result in the development of therapy which provides cardioprotection while avoiding the adverse effects of systemic estrogen delivery.

Exogenous and autocrine growth factors stimulate human intervertebral disc cell proliferation via the ERK and Akt pathways

Intervertebral disc (IVD) degeneration is accompanied by growth factor-overexpression and increased cell proliferation, probably representing a tissue repair process. Accordingly, we studied the effect of exogenous and autocrine growth factors on the proliferation of human IVD cells. We observed that Platelet-Derived Growth Factor (PDGF), basic Fibroblast Growth Factor (bFGF), and Insulin-like Growth Factor-I (IGF-I) stimulate DNA synthesis of human IVD cells, through the activation of the MEK/ERK and the PI-3K/Akt signal transduction pathways. Furthermore, medium conditioned (CM) by IVD cells induced DNA synthesis in the same cells, indicating the secretion of autocrine growth factors. The MEK/ERK and PI-3K/Akt pathways were also induced by CM, while their inhibition reversed in large part the DNA synthesis induction by CM. These responses to the exogenous and autocrine growth factors were qualitatively similar in both nucleus pulposus (NP) and annulus fibrosus (AF) cell cultures. Immunohistochemical studies in human biopsies showed significant activation of both signaling pathways, which was most prominent in the clusters of proliferating cells. These in vitro and in vivo data indicate that the proliferation of human IVD cells is regulated by exogenous and autocrine growth factors mainly via the MEK/ERK and PI-3K/Akt pathways; this may contribute to the design of future interventional approaches.

The Molecular Mechanisms that Promote Edema After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a devastating type of stroke with no effective therapies. Clinical advances in ICH treatment are limited by an incomplete understanding of the molecular mechanisms responsible for secondary injury and poor outcome. Increasing evidence suggests that cerebral edema is a major contributor to secondary injury and poor outcome in ICH. ICH activates specific signaling pathways that promote edema and damage neuronal tissue. By increasing our understanding of these pathways, we may be able to target them pharmaceutically to reduce edema in ICH patients. In this review, we focus on three major signaling pathways that promote edema after ICH: (1) the coagulation cascade and thrombin, (2) the inflammatory response and matrix metalloproteinases, and (3) the complement cascade and hemoglobin toxicity. We will describe the experimental evidence that confirms these pathways promote edema in ICH, discuss potential targets for new therapies, and comment on important directions for future research.

Adenosine A3 receptor stimulation reduces muscle injury following physical trauma and is associated with alterations in the MMP/TIMP response

We have previously demonstrated that in response to traumatic injury in skeletal muscle, there is a dysregulation of the matrix metalloproteases (MMPs) and their inhibitors (TIMPs), a response hypothesized to interfere with proper skeletal muscle regeneration. Moreover, we have shown that pharmacological activation of the adenosine A(3) receptor by Cl-IBMECA in skeletal muscle can protect against ischemia-reperfusion and eccentric exercise injury. However, the mechanism by which Cl-IBMECA protects muscle tissue is poorly defined. This study evaluated the effects of Cl-IBMECA on MMP/TIMP expression in skeletal muscle and tested the hypothesis that adenosine A(3) receptor-stimulated protection of skeletal muscle following traumatic injury is associated with a blunting of MMPs involved in inflammatory processes and collagen degradation, and an increase in MMPs associated with extracellular matrix remodeling. Sixty C57BL/6J male mice were injected with Cl-IBMECA (n = 30) or a vehicle (n = 30), and Evans blue dye. Injury was induced by applying a cold steel probe (-79°C) to the tibialis anterior (TA) muscle for 10 s. TA muscles from uninjured and injured legs were collected 3, 10, and 24 h postinjury for analysis of muscle injury and MMP/TIMP mRNA and protein levels. Twenty-four hours postinjury, 56.8% of the fibers were damaged in vehicle-treated mice vs. 35.4% in Cl-IBMECA-treated mice (P = 0.02). Cl-IBMECA treatment reduced membrane type 1 (MT1)-MMP, MMP-3, MMP-9, and TIMP-1 mRNA expression 2- to 20-fold compared with vehicle-treated mice (P < 0.05). Cl-IBMECA decreased protein levels of latent/shed MT1-MMP 23-2,000%, respectively, 3-10 h postinjury. In Cl-IBMECA-treated mice, latent MMP-2 was decreased 20% 3 h postinjury, active MMP-3 was decreased 64% 3 h postinjury, and latent/active MMP-9 was decreased 417,631% 3 h postinjury and 20% 10 h postinjury. Protein levels of active MMP-2 and latent MMP-3 were increased 25% and 74% 3 h postinjury, respectively. The present study elucidates a new protective role of adenosine A(3) receptor stimulation in posttraumatic skeletal muscle injury.

Attenuation of inflammatory events in human intervertebral disc cells with a tumor necrosis factor antagonist

STUDY DESIGN

The inflammatory responses of primary human intervertebral disc (IVD) cells to tumor necrosis factor α (TNF-α) and an antagonist were evaluated in vitro.

OBJECTIVE

To investigate an ability for soluble TNF receptor type II (sTNFRII) to antagonize TNF-α-induced inflammatory events in primary human IVD cells in vitro.

SUMMARY OF BACKGROUND DATA

TNF-α is a known mediator of inflammation and pain associated with radiculopathy and IVD degeneration. sTNFRs and their analogues are of interest for the clinical treatment of these IVD pathologies, although information on the effects of sTNFR on human IVD cells remains unknown.

METHODS

IVD cells were isolated from surgical tissues procured from 15 patients and cultured with or without 1.4 nmol/L TNF-α (25 ng/mL). Treatment groups were coincubated with varying doses of sTNFRII (12.5-100 nmol/L). Nitric oxide (NO), prostaglandin E₂ (PGE₂), and interleukin-6 (IL6) levels in media were quantified to characterize the inflammatory phenotype of the IVD cells.

RESULTS

Across all patients, TNF-α induced large, statistically significant increases in NO, PGE₂, and IL6 secretion from IVD cells compared with controls (60-, 112-, and 4-fold increases, respectively; P < 0.0001). Coincubation of TNF-α with nanomolar doses of sTNFRII significantly attenuated the secretion of NO and PGE₂ in a dose-dependent manner, whereas IL6 levels were unchanged. Mean IC₅₀ values for NO and PGE₂ were found to be 35.1 and 20.5 nmol/L, respectively.

CONCLUSION

Nanomolar concentrations of sTNFRII were able to significantly attenuate the effects of TNF-α on primary human IVD cells in vitro. These results suggest this sTNFR to be a potent TNF antagonist with potential to attenuate inflammation in IVD pathology.

Possible mechanism of betel-quid-extract-induced expression of matrix metalloproteinase-2

BACKGROUND/PURPOSE

Betel quid extract (BQE) has been demonstrated to induce matrix metalloproteinase (MMP)-2 expression. This study aimed to establish the possible mechanism involved in this event.

METHODS

Western blotting, reverse-transcription polymerase chain reaction, and gelatin zymography were used to study the expression level of MMP-2. LY294002, PD98059, U0126, N-acetyl-L-cysteine, SB203580, SP600125, and Bay 11-7082 were used to pretreat OECM-1 cells before BQE treatment and MMP-2 detection.

RESULTS

OECM-1 cells were subjected to short-term (10 minutes) or long-term (24 hours) BQE treatment (designated as SBT and LBT, respectively), and we found that both treatments increased MMP-2 protein and extracellular signal-regulated kinase (ERK) phosphorylation levels in a concentration- and time-dependent manner. LBT also increased MMP-2 mRNA level. LBT-induced MMP-2 secretion was not inhibited by PD98059 (up to 50 μM) when ERK was effectively blocked, but was attenuated by LY294002 (0-10 μM) in a concentration-dependent manner. This LBT effect was inhibited strongly by SB203580 (10 μM), SP600125 (10 μM), and Bay 11-7082 (10 μM) and mildly by N-acetyl-L-cysteine (5 mM), but not by U0126 (10 μM).

CONCLUSION

Both SBT and LBT upregulate MMP-2 expression, and LBT-induced MMP-2 expression might be mediated by phosphoinositide 3-kinase, p38 mitogen-activated protein kinase, c-Jun N-terminal kinase, and nuclear factor-κB, and to a lesser extent, by reactive oxygen species, rather than by ERK.

Intradiscal transplantation of synovial mesenchymal stem cells prevents intervertebral disc degeneration through suppression of matrix metalloproteinase-related genes in nucleus pulposus cells in rabbits

INTRODUCTION

Synovial mesenchymal stem cells (MSCs) have high proliferative and chondrogenic potentials, and MSCs transplanted into the articular cartilage defect produce abundant extracellular matrix. Because of similarities between the articular cartilage and the intervertebral disc cartilage, synovial MSCs are a potential cell source for disc regeneration. Here, we examined the effect of intradiscal transplantation of synovial MSCs after aspiration of nucleus pulposus in rabbits.

METHODS

The nucleus pulposus tissues of rabbit's intervertebral discs were aspirated to induce disc degeneration, and allogenic synovial MSCs were transplanted. At 2, 4, 6, 8, 16, 24 weeks postoperatively, we evaluated with imaging analyses such as X-ray and magnetic resonance imaging (MRI), and histological analysis. To investigate interaction between synovial MSCs and nucleus pulposus cells, human synovial MSCs and rat nucleus pulposus cells were co-cultured, and species specific microarray were performed.

RESULTS

The existence of transplanted cells labeled with DiI or derived from green fluorescent protein (GFP)-expressing transgenic rabbits was confirmed up until 24 weeks. X-ray analyses demonstrated that intervertebral disc height in the MSC group remained higher than that in the degeneration group. T2 weighted MR imaging showed higher signal intensity of nucleus pulposus in the MSC group. Immunohistological analyses revealed higher expression of type II collagen around nucleus pulposus cells in the MSC group compared with even that of the normal group. In co-culture of rat nucleus pulposus cells and human synovial MSCs, species specific microarray revealed that gene profiles of nucleus pulposus were altered markedly with suppression of genes relating matrix degradative enzymes and inflammatory cytokines.

CONCLUSIONS

Synovial MSCs injected into the nucleus pulposus space promoted synthesis of the remaining nucleus pulposus cells to type II collagen and inhibition of expressions of degradative enzymes and inflammatory cytokines, resulting in maintaining the structure of the intervertebral disc being maintained.

Update on the pathophysiology of degenerative disc disease and new developments in treatment strategies

Degenerative disc disease (DDD) continues to be a prevalent condition that afflicts populations on a global scale. The economic impact and decreased quality of life primarily stem from back pain and neurological deficits associated with intervertebral disc degeneration. Although much effort has been invested into understanding the etiology of DDD and its relationship to the onset of back pain, this endeavor is a work in progress. The purpose of this review is to provide focused discussion on several areas in which recent advances have been made. Specifically, we have categorized these advances into early, middle, and late phases of age-related or degenerative changes in the disc and into promising minimally invasive treatments, which aim to restore mechanical and biological functions to the disc.

Cardiac mast cells: the centrepiece in adverse myocardial remodelling

Increased numbers of mast cells have been reported in explanted human hearts with dilated cardiomyopathy and in animal models of experimentally induced hypertension, myocardial infarction, and chronic volume overload secondary to aortocaval fistula and mitral regurgitation. Accordingly, mast cells have been implicated to have a major role in the pathophysiology of these cardiovascular disorders. In vitro studies have verified that mast cell proteases are capable of activating collagenase, gelatinases and stromelysin. Recent results have shown that with chronic ventricular volume overload, there is an elevation in mast cell density, which is associated with a concomitant increase in matrix metalloproteinase (MMP) activity and extracellular matrix degradation. However, the role of the cardiac mast cell is not one dimensional, with evidence from hypertension and cardiac transplantation studies suggesting that they can also assume a pro-fibrotic phenotype in the heart. These adverse events do not occur in mast cell deficient rodents or when cardiac mast cells are pharmacologically prevented from degranulating. This review is focused on the regulation and dual roles of cardiac mast cells in: (i) activating MMPs and causing myocardial fibrillar collagen degradation and (ii) causing fibrosis in the stressed, injured or diseased heart. Moreover, there is strong evidence that premenopausal female cardioprotection may at least partly be due to gender differences in cardiac mast cells. This too will be addressed.

Mice deficient in PKCbeta and apolipoprotein E display decreased atherosclerosis

Endothelial activation is a central initiating event in atheroma formation. Evidence from our laboratory and others has demonstrated links between activation of early growth response-1 (Egr-1) and atherosclerosis and also has demonstrated that activated protein kinase C (PKC) betaII is a critical upstream regulator of Egr-1 in response to vascular stress. We tested the role of PKCbeta in regulating key events linked to atherosclerosis and show that the aortas of apoE(-/-) mice display an age-dependent increase in PKCbetaII antigen in membranous fractions vs. C57BL/6 animals with a approximately 2-fold increase at age 6 wk and a approximately 4.5-fold increase at age 24 wk. Consistent with important roles for PKCbeta in atherosclerosis, a significant decrease in atherosclerotic lesion area was evident in PKCbeta(-/-)/apoE(-/-) vs. apoE(-/-) mice by approximately 5-fold, in parallel with significantly reduced vascular transcripts for Egr-1 and matrix metalloproteinase (MMP)-2 antigen and activity vs. apoE(-/-) mice. Significant reduction in atherosclerosis of approximately 2-fold was observed in apoE(-/-) mice fed ruboxistaurin chow (PKCbeta inhibitor) vs. vehicle. In primary murine and human aortic endothelial cells, the PKCbeta-JNK mitogen-activated protein kinase pathway importantly contributes to oxLDL-mediated induction of MMP2 expression. Blockade of PKCbeta may be beneficial in mitigating endothelial perturbation and atherosclerosis.

The cellular pathobiology of the degenerate intervertebral disc and discogenic back pain

In 2007, three times as many peer reviewed publications covering the biology and biotherapeutics of intervertebral disc (IVD) disease appeared in the literature than in 1997. This is testimony to the upsurge in interest in the IVD, mainly driven by the openings that modern molecular pathology has generated to investigate mechanisms of human disease and the potential offered by novel therapeutic technologies to use data coming from these studies to positively influence chronic discogenic back pain and sciatica. Molecular pathology has shown IVD degeneration, a major cause of low back pain, to be a complex, active disorder in which disturbed cytokine biology, cellular dysfunction and altered load responses play key roles. This has translated into a search for target molecules and disease processes that might be the focus of future, evidence-based therapies for back pain. It is not possible to describe the totality of advances that have been made in understanding the biology of the IVD in recent years, but in this review those areas of biology that are currently influencing, or could conceivably soon impinge on, clinical thinking or practice around IVD degeneration and discogenic back pain are described and discussed.