MicroRNA-34a deficiency leads to impaired wound closure by augmented inflammation in mice

Na Zhao; Guojian Wang; Shuang Long; Mengjia Hu; Jining Gao; Xinze Ran; Junping Wang; Yongping Su; Tao Wang

doi:10.21037/atm.2020.03.161

MicroRNA-34a deficiency leads to impaired wound closure by augmented inflammation in mice

Ann Transl Med. 2020 Apr;8(7):447. doi: 10.21037/atm.2020.03.161.

Authors

Na Zhao¹, Guojian Wang¹, Shuang Long¹, Mengjia Hu¹, Jining Gao¹, Xinze Ran¹, Junping Wang¹, Yongping Su¹, Tao Wang¹

Affiliation

¹ Institute of Combined Injury, State Key Laboratory of Trauma, Burn and Combined Injury, Chongqing Engineering Research Center for Nanomedicine, College of Preventive Medicine, Third Military Medical University, Chongqing 400038, China.

Abstract

Background: Proper inflammation resolution is critical for cutaneous wound healing and disordered inflammation resolution results in chronic nonhealing wounds. However, the cellular and molecular mechanisms for resolution of inflammation during skin wound healing are not well understood. MicroRNA-34a is regarded as one tumor suppressor with complexed immune regulatory effects, yet its role during skin wound repair is still unclear.

Methods: Circular full thickness excisional wounds were made on the dorsal skin of C57 mice and miR-34a expression pattern was examined by real time RT-PCR and in situ hybridization. The wound healing rates and histologic morphometric analysis were quantified and compared between wounds treated with antagomir-34a and autologous control antagomir-NC wounds, as well as wounds between miR-34a knockout (KO) and wild type (WT) mice. Immunohistochemistry (IHC) for both MPO and F4/80 were performed to examine the infiltrative neutrophils and macrophages in wounds from miR-34a KO and WT mice. Cytokines including IL-1β, IL-6, TNF-α and IL-10, were detected and analyzed by real time RT-PCR during wound healing. IHC for IL-6 and p-STAT3 were quantified, and WB for p-STAT3 and IL-6R were examined in wounds of miR-34a KO and WT mice.

Results: We found miR-34a was significantly downregulated in the inflammatory phase and back to normal levels in the proliferative phase. Both topical knockdown wounds miR-34a levels by antagomir gel and systematic knockout miR-34a using KO mice resulted in impaired wound healing with delayed re-epithelialization and augmented inflammation. IHC results indicated that there were more residual infiltrative inflammatory cells in the proliferative phase. Moreover, over-activated IL-6/STAT3 signal pathway was identified in the wounds of miR-34a KO mice.

Conclusions: Our findings reveal that miR-34a deficiency augments skin wound inflammation response and leads to impaired wound healing, which suggest that targeted inhibition of miR-34a for tissue repair/regeneration should be with serious consideration.

Keywords: IL-6; STAT3; Skin wound healing; inflammation; miR-34a.