Inflammatory Cytokine Induced Regulation of Superoxide Dismutase 3 Expression by Human Mesenchymal Stem Cells

Kevin Kemp, Elizabeth Gray, Elizabeth Mallam, Neil Scolding, Alastair Wilkins

Increasing evidence suggests that bone marrow derived-mesenchymal stem cells (MSCs) have neuroprotective properties and a major mechanism of action is through their capacity to secrete a diverse range of potentially neurotrophic or anti-oxidant factors. The recent discovery that MSCs secrete superoxide dismutase 3 (SOD3) may help explain studies in which MSCs have a direct anti-oxidant activity that is conducive to neuroprotection in both in vivo and in vitro. SOD3 attenuates tissue damage and reduces inflammation and may confer neuroprotective effects against nitric oxide-mediated stress to cerebellar neurons; but, its role in relation to central nervous system inflammation and neurodegeneration has not been extensively investigated. Here we have performed a series of experiments showing that SOD3 secretion by human bone marrow-derived MSCs is regulated synergistically by the inflammatory cytokines TNF-alpha and IFN-gamma, rather than through direct exposure to reactive oxygen species. Furthermore, we have shown SOD3 secretion by MSCs is increased by activated microglial cells. We have also shown that MSCs and recombinant SOD are able to increase both neuronal and axonal survival in vitro against nitric oxide or microglial induced damage, with an increased MSC-induced neuroprotective effect evident in the presence of inflammatory cytokines TNF-alpha and IFN-gamma. We have shown MSCs are able to convey these neuroprotective effects through secretion of soluble factors alone and furthermore demonstrated that SOD3 secretion by MSCs is, at least, partially responsible for this phenomenon. SOD3 secretion by MSCs maybe of relevance to treatment strategies for inflammatory disease of the central nervous system.