Abstract
BackgroundInflammation is a key contributor to central nervous system (CNS) injury such as stroke, and is a major target for therapeutic intervention. Effective treatments for CNS injuries are limited and applicable to only a minority of patients. Stem cell-based therapies are increasingly considered for the treatment of CNS disease, because they can be used as in-situ regulators of inflammation, and improve tissue repair and recovery. One promising option is the use of bone marrow-derived mesenchymal stem cells (MSCs), which can secrete anti-inflammatory and trophic factors, can migrate towards inflamed and injured sites or can be implanted locally. Here we tested the hypothesis that pre-treatment with inflammatory cytokines can prime MSCs towards an anti-inflammatory and pro-trophic phenotype in vitro.MethodsHuman MSCs from three different donors were cultured in vitro and treated with inflammatory mediators as follows: interleukin (IL)-1α, IL-1β, tumour necrosis factor alpha (TNF-α) or interferon-γ. After 24 h of treatment, cell supernatants were analysed by ELISA for expression of granulocyte-colony stimulating factor (G-CSF), IL-10, brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), IL-1 receptor antagonist (IL-1Ra) and vascular endothelial growth factor (VEGF). To confirm the anti-inflammatory potential of MSCs, immortalised mouse microglial BV2 cells were treated with bacterial lipopolysaccharide (LPS) and exposed to conditioned media (CM) of naïve or IL-1-primed MSCs, and levels of secreted microglial-derived inflammatory mediators including TNF-α, IL-10, G-CSF and IL-6 were measured by ELISA.ResultsUnstimulated MSCs constitutively expressed anti-inflammatory cytokines and trophic factors (IL-10, VEGF, BDNF, G-CSF, NGF and IL-1Ra). MSCs primed with IL-1α or IL-1β showed increased secretion of G-CSF, which was blocked by IL-1Ra. Furthermore, LPS-treated BV2 cells secreted less inflammatory and apoptotic markers, and showed increased secretion of the anti-inflammatory IL-10 in response to treatment with CM of IL-1-primed MSCs compared with CM of unprimed MSCs.ConclusionsOur results demonstrate that priming MSCs with IL-1 increases expression of trophic factor G-CSF through an IL-1 receptor type 1 (IL-1R1) mechanism, and induces a reduction in the secretion of inflammatory mediators in LPS-activated microglial cells. The results therefore support the potential use of preconditioning treatments of stem cells in future therapies.
Highlights
Inflammation is a key contributor to central nervous system (CNS) injury such as stroke, and is a major target for therapeutic intervention
We show for the first time that Mesenchymal stem/stromal cell (MSC) express high constitutive levels of key anti-inflammatory and trophic factors, and that priming with IL-1 triggers secretion of the trophic factor granulocyte-colony stimulating factor (G-CSF), an effect that was only observed in response to IL-1
Enzyme-linked immunosorbent assay Levels of human IL-10, brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), Tumour necrosis factor alpha (TNF-α) and G-CSF in culture media from MSCs were quantified by ELISA using DuoSet® kits (R&D Systems, UK) according to the manufacturer’s instructions
Summary
Inflammation is a key contributor to central nervous system (CNS) injury such as stroke, and is a major target for therapeutic intervention. Stem cells are undifferentiated cells found in many adult tissues, the function of which is renewal of damaged tissues during ageing or after disease and injuries Because of their regenerative properties, these cells are being increasingly considered as new therapeutic agents for the treatment of central nervous system (CNS) diseases. Once infiltrated into the brain, MSCs produce an array of mediators such as cytokines and growth factors [8, 9] that promote tissue repair mainly by activating endogenous repair mechanisms [10, 11], and by acting as temporal immunesuppressants [1, 6] These properties make MSCs ideal candidates for cell-based therapies, for the treatment of CNS disorders such as stroke, Huntington’s disease, amyotrophic lateral sclerosis or Parkinson’s disease [12]. The precise mechanisms by which MSCs exert beneficial effects remain elusive [17]
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