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Background: Previously, we showed that EP4 receptor agonist increases the number and suppressive activity of myeloid derived suppressor cells (MDSCs; both G-MDSCs and M-MDSCs) in the bone marrow culture in vitro. Methods: In the first part, mice were rendered asthmatic using HDM and then the role of intravenous adoptive transfer of MDSCEP4 (MDSCs generated and activated using the EP4 agonist in vitro) was assessed. In the second part, the role of three different doses of intravenous EP4 receptor agonist L902,688 (0.1, 0.2 and 0.4 mg/kg) on in vivo generation of MDSCs and respectively their anti-inflammatory role in asthmatic mice was studied. Results: We found that adoptive transfer of MDSCEP4 could ameliorate the immune response in a murine asthma model. Furthermore, EP4 agonist therapy increases the number of MDSCs in the spleen and lung of asthmatic mice, in a dose response manner, and reduces the inflammatory responses and histopathological changes. Furthermore, MDSCs isolated from EP4 agonist treated asthmatic mice could significantly reduce the proliferation of CD4+ T cells mainly through arginase 1 and inducible nitric oxide synthase. Conclusion: Our results demonstrate that EP4 agonist generates and activates anti-inflammatory MDSCs to suppress the proliferation of T cells and airway inflammation, likely by upregulating arginase 1 and inducible nitric oxide synthase. EP4 agonist therapy seems to be a potential therapeutic target that would ultimately result in anti-inflammatory effects in asthmatic patients through generation and activation of MDSCs.

Genome editing using site-specific endonucleases (SSE) holds great potential to repair disease-causing genes. In this study we offer a promising approach to deliver SSEs as nuclease-encoded, chemically modified mRNA (nec-mRNA) together with a repair template to correct the lung disease Surfactant Protein-B (SP-B) deficiency while simultaneously reducing SSE-induced off-target effects. To assess the potential of mRNA-encoded nucleases to create site specific double-strand breaks (DSBs), we evaluated a panel of 15 transcription activator-like effector nucleases (TALENs) and 36 Zink-Finger nucleases (ZFNs) for non-homologous end-joining (NHEJ) and also tested for the integration of a promoter template by homology-directed repair (HDR) in vitro . In addition we compared different mRNA modifications to assess immunoreactions against nec-mRNA. Finally, we co-administered intratracheally nec-mRNA with the repair template to SP-B deficient mice and evaluated the survival and promoter integration efficacy. Compared to plasmid-DNA, delivery of mRNA-encoded nucleases resulted in more frequent induction of DSBs ( P P in vitro . While being only transiently expressed, incorporation of modified nucleosides into nec-mRNA and complexation into nanoparticles (NPs) increased mRNA expression levels ( P in vivo . Also, no immune activation was observed. Importantly, delivery of nec-mRNA-NP to SP-B deficient mice lead to prolonged survival rates compared with matched control groups ( P In conclusion, we have shown that delivery of nec-mRNA-NP together with a repair template results in successful, site-specific genome editing in vivo .