Creation and characterisation of 11β hydroxysteroid dehydrogenase type 1 transgenic mesenchymal stem cells for use in models of acute respiratory distress syndrome

Abstract Background: Human bone marrow mesenchymal stem cell (MSC) administration reduces inflammation in pre-clinical models of lung injury, however clinical efficacy in patients with acute respiratory distress syndrome (ARDS) has not been shown. Upregulation of the glucocorticoid activating enzyme, 11β hydroxysteroid dehydrogenase type 1 (HSD-1) within the alveolar space elevates local anti-inflammatory cortisol levels, and promotes alveolar macrophage efferocytosis. Administration of HSD-1 transgenic MSCs (tMSCs) that overexpress HSD-1 may enhance local cortisol activation. This combined cellular and gene therapy may be more effective at reducing inflammation in ARDS than cellular therapy alone. Methods: Molecular cloning was used to create a recombinant lentiviral vector containing the HSD-1 and green fluorescent protein (GFP) transgenes. MSCs were transfected using this lentivirus, then transfection efficiency was assessed using flow-cytometry. HSD-1 transgene expression was assessed using immunofluorescence and western blotting. Thin layer chromatography was used to assess HSD-1 function in tMSCs. Bi-lineage differentiation and flow-cytometry were used to determine whether tMSCs maintained a stem cell phenotype. Results: A recombinant lentiviral vector was created containing the HSD-1 and GFP transgenes under the control of a tetracycline promoter. MSCs were successfully transfected, with a transfection efficiency of 91.1%. HSD-1 transgene expression was confirmed by immunofluorescence and western blot. Functional HSD-1 activity was evident within tMSCs, with predominant reductase cortisol activation, following treatment with the transcriptional activator doxycycline. HSD-1 reductase activity was maintained for 72 hours after doxycycline was removed from tMSCs. HSD-1 tMSCs maintained the capacity for osteogenic and adipogenic differentiation, and maintained expression of MSC surface markers. Conclusions: We successfully transduced tMSCs to express the HSD-1 transgene that functions predominantly as a reductase. Administration of HSD-1 tMSCs to in vivo models of ARDS may attenuate inflammation through activation of cortisol in the alveolar space.