Mesenchymal stromal cells ameliorate acute lung injury induced by LPS mainly through stanniocalcin-2 mediating macrophage polarization

Haijin Lv; Qiuli Liu; Yao Sun; Xiaomeng Yi; Xuxia Wei; Wei Liu; Qi Zhang; Huimin Yi; Guihua Chen

doi:10.21037/atm.2020.02.105

Mesenchymal stromal cells ameliorate acute lung injury induced by LPS mainly through stanniocalcin-2 mediating macrophage polarization

Ann Transl Med. 2020 Mar;8(6):334. doi: 10.21037/atm.2020.02.105.

Authors

Haijin Lv^{1

2}, Qiuli Liu^{2

3}, Yao Sun¹, Xiaomeng Yi¹, Xuxia Wei¹, Wei Liu^{2

4}, Qi Zhang^{2

3}, Huimin Yi¹, Guihua Chen^{4

5}

Affiliations

¹ Surgical and Transplant Intensive Care Unit, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou 510630, China.
² Key Laboratory of Liver Disease Biotherapy and Translational Medicine of Guangdong Higher Education Institutes, Sun Yat-sen University, Guangzhou 510630, China.
³ The Biotherapy Center, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou 510630, China.
⁴ Guangdong Provincial Key Laboratory of Liver Disease Research, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou 510630, China.
⁵ Department of Hepatic Surgery and Liver Transplantation Center, The Third Affiliated Hospital, Organ Transplantation Institute, Sun Yat-sen University, Guangzhou 510630, China.

Abstract

Background: Acute lung injury (ALI) is a devastating syndrome with no effective pharmacological therapies in the clinic. Mesenchymal stromal cells (MSCs) have been demonstrated to promote inflammation resolution and tissue repair in ALI. However, the specific mechanisms of this have not been clearly elucidated. Stanniocalcin-2 (STC2) is a stress-responsive protein that has anti-oxidative properties. Our previous study found that STC2 is a highly expressed stanniocalcin in MSCs, which may be involved in immunomodulatory activities. However, the role of STC2 in MSCs to resolve ALI has never been elucidated.

Methods: Specific shRNA was used to downregulate STC2 in MSCs. We detected ROS, cell apoptosis, and paracrine factors changes in MSCs. STC2-associated antioxidant genes were also investigated by Co-immunoprecipitation (Co-IP) and immunofluorescence. Macrophage (THP1 cells) phenotype transitions were measured by flow cytometry after coculturing with MSCs in vitro. Then, we used MSCs to treat LPS-induced ALI in mice, and assessed injury scores inflammation, and antioxidant activities in the lungs of the mice. Alveolar macrophage (AM) phenotypes and CFSE-labeled MSC apoptosis in collected bronchoalveolar fluids (BALF) were also analyzed by flow cytometry.

Results: After the STC2 knockdown, MSCs increased ROS generation and cell apoptosis after PX12 pretreatment. The antioxidant protein Nrf2 was colocalized with STC2 in the nucleus. A lack of STC2 expression in MSCs produced less interleukin 10 (IL10) and blunted macrophage polarization in THP1 cells. Furthermore, in the murine LPS-induced ALI model, the STC2 knockdown counteracted the inflammatory resolution and antioxidative effect of MSCs in the lungs. MSC^shSTC2-treated mice had a higher lung injury score than the controls, which may be attributed to diminished AM polarization and increased apoptosis of MSCs in vivo.

Conclusions: Collectively, these results suggested that STC2 is essential to the anti-oxidative and anti-inflammation properties of MSCs and could prove to be crucial for stem cell therapies for ALI.

Keywords: Stanniocalcins-2 (STC2); acute lung injury (ALI); apoptosis; macrophage; mesenchymal stromal cells (MSCs).