Alison K Cross

Sheffield Hallam University, Sheffield, England, United Kingdom

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Publications (32)108.36 Total impact

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    ABSTRACT: Chronic low back pain (LBP) is the most common cause of disability worldwide. New ideas surrounding LBP are emerging that are based on interactions between mechanical, biological and chemical influences on the human IVD. The degenerate IVD is proposed to be innervated by sensory nerve fibres and vascularised by blood vessels, and it is speculated to contribute to pain sensation. However, the incidence of nerve and blood vessel ingrowth, as well as whether these features are always associated, is unknown. We investigated the presence of nerves and blood vessels in the nucleus pulposus (NP) of the IVD in a large population of human discs. Immunohistochemistry was performed with 61 human IVD samples, to identify and localise nerves (neurofilament 200 [NF200]/protein gene product 9.5) and blood vessels (CD31) within different regions of the IVD. Immunopositivity for NF200 was identified within all regions of the IVD within post-mortem tissues. Nerves were seen to protrude across lamellar ridges and through matrix towards NP cells. Nerves were identified deep within the NP and were in many cases, but not always, seen in close proximity to fissures or in areas where decreased matrix was seen. Fifteen percent of samples were degenerate and negative for nerves and blood vessels, whilst 16 % of all samples were degenerate with nerves and blood vessels. We identified 52 % of samples that were degenerate with nerves but no blood vessels. Interestingly, only 4 % ofall samples were degenerate with no nerves but positive for blood vessels. Of the 85 samples investigated, only 6 % of samples were non-degenerate without nerves and blood vessels and 7 % had nerves but no blood vessels. This study addresses the controversial topic of nerve and blood vessel ingrowth into the IVD in a large number of human samples. Our findings demonstrate that nerves are present within a large proportion of NP samples from degenerate IVDs. This study shows a possible link between nerve ingrowth and degeneration of the IVD and suggests that nerves can migrate in the absence of blood vessels.
    Full-text · Article · Dec 2015 · Arthritis Research & Therapy
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    ABSTRACT: Nerve and blood vessel ingrowth during intervertebral disc degeneration, is thought to be a major cause of low back pain, however the regulation of this process is poorly understood. Here, we investigated the expression and regulation of a subclass of axonal guidance molecules known as the class 3 semaphorins, and their receptors; plexins and neuropilins within human NP tissue and their regulation by pro-inflammatory cytokines. Importantly this determined whether semaphorin expression was associated with the presence of nerves and blood vessels in tissues from human intervertebral discs. The study demonstrated that semaphorin3A, 3C, 3D, 3E and 3F and their receptors were expressed by native NP cells and further demonstrated their expression was regulated by IL-1β but to a lesser extent by IL-6 and TNFα. This is the first study to identify sema3C, sema3D and their receptors within the nucleus pulposus of intervertebral discs. Immunopositivity shows significant increases in semaphorin3C, 3D and their receptor neuropilin-2 in degenerate samples which were shown to contain nerves and blood vessels, compared to non-degenerate samples without nerves and blood vessels. Therefore data presented here suggests that semaphorin3C may have a role in promoting innervation and vascularisation during degeneration, which may go on to cause low back pain.
    Full-text · Article · Jun 2015 · Oncotarget

  • No preview · Article · Oct 2014 · Journal of Neuroimmunology
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    ABSTRACT: IntroductionThe degenerate intervertebral disc (IVD) becomes innervated by sensory nerve fibres, and vascularised by blood vessels. This study aimed to identify neurotrophins, neuropeptides and angiogenic factors within native IVD tissue and to further investigate whether pro-inflammatory cytokines are involved in the regulation of expression levels within nucleus pulposus (NP) cells, nerve and endothelial cells.Methods Quantitative real-time PCR (qRT-PCR) was performed on 53 human IVDs from 52 individuals to investigate native gene expression of neurotrophic factors and their receptors, neuropeptides and angiogenic factors. The regulation of these factors by cytokines was investigated in NP cells in alginate culture, and nerve and endothelial cells in monolayer using RT-PCR and substance P (SP) protein expression in interleukin-1 (IL-1ß) stimulated NP cells.ResultsInitial investigation on uncultured NP cells identified expression of all neurotrophins by native NP cells, whilst the nerve growth factor (NGF) receptor was only identified in severely degenerate and infiltrated discs, and brain derived neurotrophic factor (BDNF) receptor expressed by more degenerate discs. BDNF expression was significantly increased in infiltrated and degenerate samples. SP and vascular endothelial growth factor (VEGF) were higher in infiltrated samples. In vitro stimulation by IL-1ß induced NGF in NP cells. Neurotropin-3 was induced by tumour necrosis factor alpha in human dermal microvascular endothelial cells (HDMECs). SP gene and protein expression was increased in NP cells by IL-1ß. Calcitonin gene related peptide was increased in SH-SY5Y cells upon cytokine stimulation. VEGF was induced by IL-1ß and interleukin-6 in NP cells, whilst pleiotrophin was decreased by IL-1ß. VEGF and pleiotrophin were expressed by SH-SY5Y cells, and VEGF by HDMECs, but were not modulated by cytokines.Conclusions The release of cytokines, in particular IL-1ß during IVD degeneration, induced significant increases in NGF and VEGF which could promote neuronal and vascular ingrowth. SP which is released into the matrix could potentially up regulate the production of matrix degrading enzymes and also sensitise nerves, resulting in nociceptive transmission and chronic low back pain. This suggests that IL-1ß is a key regulatory cytokine, involved in the up regulation of factors involved in innervation and vascularisation of tissues.
    Full-text · Article · Aug 2014 · Arthritis Research & Therapy
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    ABSTRACT: Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disease, considered to be autoimmune in origin. Post-translational modification of central nervous system proteins, including glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP), through citrullination of arginine residues, may lead to exposure of neoepitopes, triggering autoimmunity. Here we investigated the expression of citrullinated proteins in active MS lesions, MS normal appearing white matter and control brain white matter. We demonstrate increased citrullinated GFAP and MBP by immunohistochemistry and western blotting in areas of ongoing demyelination, suggesting a pivotal role for deimination of GFAP and MBP in MS pathogenesis MS.
    Full-text · Article · May 2014 · Journal of Neuroimmunology

  • No preview · Article · May 2014 · Global Spine Journal
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    ABSTRACT: The aims of these studies were to identify the cytokine and chemokine expression profile of nucleus pulposus (NP) cells and to determine the relationships between NP cell cytokine and chemokine production and the characteristic tissue changes seen during intervertebral disc (IVD) degeneration. Real-time q-PCR cDNA Low Density Array (LDA) was used to investigate the expression of 91 cytokine and chemokine associated genes in NP cells from degenerate human IVDs. Further real-time q-PCR was used to investigate 30 selected cytokine and chemokine associated genes in NP cells from non-degenerate and degenerate IVDs and those from IVDs with immune cell infiltrates ('infiltrated'). Immunohistochemistry (IHC) was performed for four selected cytokines and chemokines to confirm and localize protein expression in human NP tissue samples. LDA identified the expression of numerous cytokine and chemokine associated genes including 15 novel cytokines and chemokines. Further q-PCR gene expression studies identified differential expression patterns in NP cells derived from non-degenerate, degenerate and infiltrated IVDs. IHC confirmed NP cells as a source of IL-16, CCL2, CCL7 and CXCL8 and that protein expression of CCL2, CCL7 and CXCL8 increases concordant with histological degenerative tissue changes. Our data indicates that NP cells are a source of cytokines and chemokines within the IVD and that these expression patterns are altered in IVD pathology. These findings may be important for the correct assessment of the 'degenerate niche' prior to autologous or allogeneic cell transplantation for biological therapy of the degenerate IVD.
    Full-text · Article · Dec 2013 · Arthritis research & therapy
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    ABSTRACT: The objective of the study was to investigate how inflammatory cytokines, IL-1β, and TNF-α control NOTCH signaling activity in nucleus pulposus (NP) cells. An increase in expression of selective NOTCH receptors (NOTCH1 and -2), ligand (JAGGED2), and target genes (HES1, HEY1, and HEY2) was observed in NP cells following cytokine treatment. A concomitant increase in NOTCH signaling as evidenced by induction in activity of target gene HES1 and HEY1 promoters and reporter 12xCSL was seen. Moreover, treatment increased activity of a 2-kb NOTCH2 promoter. Treatment of cells with NF-κB and MAPK inhibitors abolished the inductive effect of cytokines on NOTCH2 promoter and its expression. Gain and loss-of-function studies confirmed the inductive effect of p65 on NOTCH2 promoter activity. In contrast, p50 blocked the cytokine induction of promoter activity. Supporting promoter studies, lentiviral delivery of sh-p65, and sh-IKKβ significantly decreased cytokine dependent change in NOTCH2 expression. Interestingly, MAPK signaling showed an isoform-specific control of NOTCH2 promoter; p38α/β2/δ, ERK1, and ERK2 contributed to cytokine dependent induction, whereas p38γ played no role. Analysis of human NP tissues showed that NOTCH1 and -2 and HEY2 expression correlated with each other. Moreover, expression of NOTCH2 and IL-1β as well as the number of cells immunopositive for NOTCH2 significantly increased in histologically degenerate discs compared with non-degenerate discs. Taken together, these results explain the observed dysregulated expression of NOTCH genes in degenerative disc disease. Thus, controlling IL-1β and TNF-α activities during disc disease may restore NOTCH signaling and nucleus pulposus cell function.
    No preview · Article · Apr 2013 · Journal of Biological Chemistry
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    ABSTRACT: Objective To investigate tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β) regulation of CCL3 expression in nucleus pulposus (NP) cells and in macrophage migration. Methods Quantitative reverse transcription–polymerase chain reaction and immunohistochemistry were used to measure CCL3 expression in NP cells. Transfections were used to determine the role of NF-κB, CCAAT/enhancer binding protein (C/EBPβ), and MAPK on cytokine-mediated CCL3 promoter activity. The effect of NP-conditioned medium on macrophage migration was measured using a Transwell system. ResultsAn increase in CCL3 expression and promoter activity was observed in NP cells after TNFα or IL-1β treatment. Treatment of cells with NF-κB and MAPK inhibitors abolished the effect of the cytokines on CCL3 expression. The inductive effect of p65 and C/EBPβ on the CCL3 promoter was confirmed through gain-of-function and loss-of-function studies. Notably, cotransfection with p50 completely blocked cytokine- and p65-dependent induction. In contrast, c-Rel and RelB had little effect on promoter activity. Lentiviral transduction with short hairpin RNA for p65 (shp65) and shIKKβ significantly decreased the TNFα-dependent increase in CCL3 expression. Analysis of degenerated human NP tissue samples showed that CCL3, but not CCL4, expression correlated positively with the grade of tissue degeneration. Importantly, treatment of macrophages with conditioned medium of NP cells treated with TNFα or IL-1β promoted their migration. Pretreatment of macrophages with an antagonist of CCR1, the primary receptor for CCL3 and CCL4, blocked cytokine-mediated migration. Conclusion Our findings indicate that TNFα and IL-1β modulate the expression of CCL3 in NP cells by controlling the activation of MAPK, NF-κB, and C/EBPβ signaling. The CCL3–CCR1 axis may play an important role in promoting macrophage infiltration in degenerated, herniated discs.
    No preview · Article · Mar 2013 · Arthritis & Rheumatology

  • No preview · Article · Sep 2012 · Global Spine Journal

  • No preview · Article · Sep 2012 · Global Spine Journal

  • No preview · Article · Sep 2012 · Global Spine Journal

  • No preview · Conference Paper · Sep 2012

  • No preview · Conference Paper · Sep 2012
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    ABSTRACT: ADAMTS-13 is the Von Willebrand factor (vWF) cleaving protease, responsible for the cleavage and down-regulation of the pro-thrombotic properties of ultra large VWF multimers. It is expressed predominantly by the hepatic stellate cells of the liver, but is also found to be expressed in other tissues, including brain. Reduced ADAMTS-13 is associated with a variety of thrombotic microangiopathies. Since the cellular origin and regulation of ADAMTS-13 expression in the brain is unknown, we aimed to investigate this in four different central nervous system (CNS)-derived cell lines, SHSY-5Y (human neuroblastoma), U373 (human astroglioma), CHME-3 (human foetal microglia) and hCMEC/D3 (adult human brain endothelial cells). All cell lines expressed ADAMTS-13 mRNA constitutively with neuroblastoma cells showing the highest expression. Interleukin (IL)-1β down-regulated ADAMTS-13 mRNA expression in astroglioma cells and microglial cells whereas TNF and IL-6 treatment showed no significant differences in ADAMTS-13 mRNA expression in any cell line tested. ADAMTS-13 protein expression was reduced in a dose-dependent manner only in astroglioma cells following stimulation by IL-1β. The ability of IL-1β to significantly reduce ADAMTS-13 mRNA expression in human microglia and astroglioma cells suggests a role in the haemostasis of the local microenvironment under inflammatory conditions. This is the first report of ADAMTS-13 expression in cells of the CNS; however, its function remains to be determined.
    No preview · Article · Jul 2011 · Journal of Molecular Neuroscience
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    ABSTRACT: Multiple sclerosis is a chronic immune-mediated disease of the CNS. Although it is a predominantly T-cell mediated condition, B cells and autoreactive antibodies play an important role in its pathogenesis, with the presence of oligoclonal immunoglobulins in the cerebrospinal fluid being an important diagnostic indicator. The target of these immunoglobulins has not yet been fully characterized. However, post-translational modifications of CNS-specific proteins are thought to contribute to their production through the generation of novel epitopes. One post-translational modification in particular, the conversion of the amino acid arginine to the nonstandard amino acid, citrulline, has been increasingly described in the literature as a factor in the pathogenesis of this condition. In this article, we summarize and discuss the current knowledge on citrullination in multiple sclerosis, the importance of this in relation to its pathogenesis and, potentially, its diagnosis.
    No preview · Article · Jul 2011 · Future Neurology
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    ABSTRACT: Clarification of the pathophysiological mechanisms of intra-arterial thromboembolism may lead to novel treatments for cerebrovascular disease. There is increasing evidence for the role of von Willebrand factor (VWF) cleaving protease (ADAMTS-13) in modulating the thrombotic cascade in high flow arterial settings. VWF multimers are rich in ultra large forms (ULVWF) which can rapidly bind its primary platelet receptor resulting in spontaneous aggregation of platelets. Under normal conditions, these ULVWF are regulated by rapid proteolysis converting them to smaller, less active forms. The protease responsible for cleavage of ULVWF is ADAMTS-13. We measured the ADAMTS-13 antigen and ADAMTS-13 activity levels in the plasma of consecutive patients with transient ischaemic attack (TIA), compared with nonstroke controls, in a hospital based TIA clinic. This was compared with VWF levels. Samples were analysed in the acute phase and at 3 months postevent. In our pilot study patients with partial anterior circulation type TIAs had significantly reduced ADAMTS-13 activity compared to controls (p=0.0394). No significant differences were seen between high- and low-risk ABCD2 scored patients. We did not observe any significant changes in VWF levels in our study sample. Our pilot study suggests a potential role for altered ADAMTS-13 activity in the pathophysiology of TIA.
    No preview · Article · Nov 2010 · Journal of neurology, neurosurgery, and psychiatry
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    ABSTRACT: The ADAMTS enzymes (a disintegrin and metalloproteinase with thrombospondin type 1-like motifs) have important roles in central nervous system (CNS) physiology and pathology. This current study aimed to analyse the expression of ADAMTS-9 following transient middle cerebral artery occlusion (tMCAo) in the rat, a model of focal cerebral ischaemia. Using real-time RT-PCR, ADAMTS-9 mRNA was demonstrated to be significantly up-regulated in tMCAo brain tissue compared to sham-operated at 24h post-ischaemia. The mature form of the ADAMTS-9 protein was only detected by Western blotting in brains subjected to tMCAo at 24h. In situ hybridisation demonstrated that ADAMTS-9 mRNA was expressed by neurones in tMCAo tissue. This study indicates that ADAMTS-9 expression is modulated in response to cerebral ischaemia in vivo and further research will resolve whether it plays a role in the subsequent degenerative or repair processes.
    No preview · Article · Apr 2009 · Neuroscience Letters
  • CM Bradford · AK Cross · G Haddock · MN Woodroofe
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    ABSTRACT: Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disease, which predominantly affects the white matter of the central nervous system (CNS). It is the most common neurological disease in young adults with a mean age of onset of 30 years (Trapp and Nave, 2008). The disease is characterized by destruction of the myelin sheath, which insulates the axons of nerves, resulting in lesions of demyelinated axon fibres (Lassman, 2004). Within these lesions there is infi ltration of T and B lymphocytes and macrophages, as well as locally activated CNS resident cells, astrocytes and microglia (Musse and Harauz, 2007).
    No preview · Article · Jan 2009
  • A K Cross · M N Woodroofe

    No preview · Article · Sep 2008 · Inflammopharmacology