Multipotent mesenchymal stromal cells decrease transforming growth factor β1 expression in microglia/macrophages and down-regulate plasminogen activator inhibitor 1 expression in astrocytes after stroke

Multipotent mesenchymal stromal cells (MSCs) decrease the expression of transforming growth factor beta 1 (TGF beta 1) in astrocytes and subsequently decrease astrocytic plasminogen activator inhibitor 1 (PAI-1) level in an autocrine manner. Since activated microglia/macrophages are also a source of TGF beta 1 after stroke, we therefore tested whether MSCs regulate TGF beta 1 expression in microglia/macrophages and subsequently alters PAI-1 expression after ischemia. TGF beta 1 and its downstream effector phosphorylated SMAD 2/3 (p-SMAD 2/3) were measured in mice subjected to middle cerebral artery occlusion (MCAo). MSC treatment significantly decreased TGF beta 1 protein expression in both astrocytes and microglia/macrophages in the ischemic boundary zone (IBZ) at day 14 after stroke. However, the p-SMAD 2/3 was only detected in astrocytes and decreased after MSC treatment. In vitro, RT-PCR results showed that the TGF beta 1 mRNA level was increased in both astrocytes and microglia/macrophages in an astrocyte-microglia/macrophage co-culture system after oxygen-glucose deprived (OGD) treatment. MSCs treatment significantly decreased the above TGF beta 1 mRNA level under OGD conditions, respectively. OGD increased the PAI-1 mRNA in astrocytes in the astrocyte-microglia/macrophage co-culture system, and MSC administration significantly decreased this level. PAI-1 mRNA was very low in microglia/macrophages compared with that in astrocytes under different conditions. Western blot results also verified that MSC administration significantly decreased p-SMAD 2/3 and PAI-1 level in astrocytes in astrocyte-microglia/macrophage co-culture system under OGD conditions. Our in vivo and in vitro data, in concert, suggest that MSCs decrease TGF beta 1 expression in microglia/macrophages in the IBZ which contribute to the down-regulation of PAI-1 level in astrocytes. Published by Elsevier Ireland Ltd.