IL-33 Promotes ST2-Dependent Fibroblast Maturation via P38 and TGF-β in a Mouse Model of Epidural Fibrosis

  • Tissue Eng Regen Med. 2022 Jun;19(3):577-588. doi: 10.1007/s13770-021-00425-1.
Haoran Wang   #  1 ,  Tao Wu   #  1 ,  Feng Hua  1 ,  Jinpeng Sun  1 ,  Yunfeng Bai  1 ,  Weishun Wang  2 ,  Jun Liu  1 ,  Mingshun Zhang  3
Affiliations
  • 1. Department of Orthopedics, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China.
  • 2. Department of Orthopedics, Sir Run Run Hospital, Nanjing Medical University, Nanjing, China.
  • 3. NHC Key Laboratory of Antibody Technique, Jiangsu Province Engineering Research Center of Antibody Drug, Department of Immunology, Nanjing Medical University, Nanjing, China. [email protected].
  • # Contributed equally.
PMID: 35195855 DOI: 10.1007/s13770-021-00425-1
Abstract

Background: Recent evidence suggests that IL-33, a novel member of the IL-1β family, is involved in organ fibrosis. However, the roles of IL-33 and its receptor ST2 in epidural fibrosis post spine operation remain elusive.

Methods: A mouse model of epidural fibrosis was established after laminectomy. IL-33 in the wound tissues post laminectomy was measured with Western blotting, ELISA and immunoflurosence imaging. The fibroblast cell line NIH-3T3 and primary fibroblasts were treated with IL-33 and the mechanisms of maturation of fibroblasts into myofibroblasts were analyzed. To explore roles of IL-33 and its receptor ST2 in vivo, IL-33 knockout (KO) and ST2 KO mice were employed to construct the model of laminectomy. The epidural fibrosis was evaluated using H&E and Masson staining, western-blotting, ELISA and immunohistochemistry.

Results: As demonstrated in western blotting and ELISA, IL-33 was increased in epidural wound tissues post laminectomy. The immunoflurosence imaging revealed that endothelial cells (CD31+) and fibroblasts (α-SAM+) were major producers of IL-33 in the epidural wound tissues. In vitro, IL-33 promoted fibroblast maturation, which was blocked by ST2 neutralization antibody, suggesting that IL-33-promoted-fibroblasts maturation was ST2 dependent. Further, IL-33/ST2 activated MAPK p38 and TGF-β pathways. Either p38 inhibitor or TGF-β inhibitor decreased fibronectin and α-SAM production from IL-33-treated fibroblasts, suggesting that p38 and TGF-β were involved with IL-33/ST2 signal pathways in the fibroblasts maturation. In vivo, IL-33 KO or ST2 KO decreased fibronectin, α-SMA and Collagen deposition in the wound tissues of mice that underwent spine surgery. In addition, TGF-β1 was decreased in IL-33 KO or ST2 KO epidural wound tissues.

Conclusion: In summary, IL-33/ST2 promoted fibroblast differentiation into myofibroblasts via MAPK p38 and TGF-β in a mouse model of epidural fibrosis after laminectomy.

Keywords
Epidural fibrosis; Fibroblast; IL-33; ST2; TGF-β1; p38.
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