Chemically Modified SDF-1α mRNA Promotes Random Flap Survival by Activating the SDF-1α/CXCR4 Axis in Rats

Abstract

Background: Random skin flaps are frequently applied in surgery for patients suffering from soft tissue defects caused by congenital deformities, trauma and tumor resection. However, ischemia and necrosis in distal parts of random skin flaps remains a common challenge that limits the clinical application of this procedure. Recently, chemically modified mRNA (modRNA) was found to have great therapeutic potential. Here, we explored the potential of fibroblasts engineered to express modified mRNAs encoding the stromal cell-derived factor-1α (SDF-1α) to improve vascularization and survival of therapeutic random skin flaps. Methods: Ex vivo fibroblasts were transfected with plasmids encoding GFP, luciferase or SDF-1α modRNAs. The transfection efficiency and recombinant protein expression were assessed. Rat random skin flaps models were injected intradermally with fibroblasts transfected with modRNA in vivo. The degree of necrosis and apoptosis in skin flaps were evaluated by histological analysis. Expression of SDF-1α/CXCR4 pathway-related proteins was evaluated by western blot and immunofluorescence analyses. Findings: Our study showed that fibroblasts pre-treated with SDF-1α modRNA have the potential to salvage ischemic skin flaps. Through a detailed analysis, we revealed that a fibroblast SDF-1α modRNA combinatorial treatment dramatically reduced tissue necrosis and significantly promoted neovascularization in random skin flaps compared to that in the control and vehicle groups. Moreover, SDF-1α modRNA transcription in fibroblasts promoted activation of the SDF-1α/CXCR4 pathway, with concomitant inactivation of the MEK/ERK, PI3K/AKT and JAK2/STAT3 signaling pathways, indicating a possible correlation with cell proliferation and migration. Interpretation: Fibroblast-mediated SDF-1α modRNA expression represents a promising strategy for random skin flap regeneration. Funding Statement: This work was supported by grants from the Wenzhou Public Welfare Science and Technology Project (Y20170238), the National Natural Science Foundation of China (81401798), the Zhejiang Provincial Natural Science Foundation of China (LQ13C100001), Zhejiang Provincial Project for Medical and Health Science and Technology (2013KYA128), Shanghai Pujiang Program (18PJD031), Shanghai Collaborative Innovation Program on Translational Medicine (TM201821), the Biomedical Engineering fund of Shanghai Jiao Tong University (YG2016MS28) and fund from Shanghai Key Laboratory of Tissue Engineering. Declaration of Interests: The authors declare no conflict of interest. Ethics Approval Statement: This study was approved by the Animal Care and Use Committee of Wenzhou Medical University (ethics code: wydw2017-0159).