Fabrication of Interleukin-4 Encapsulated Bioactive Microdroplets for Regulating Inflammation and Promoting Osteogenesis

Int J Nanomedicine. 2023 Apr 19:18:2019-2035. doi: 10.2147/IJN.S397359. eCollection 2023.

Abstract

Background: Despite the inherent regenerative ability of bone, large bone defect regeneration remains a major clinical challenge for orthopedic surgery. Therapeutic strategies medicated by M2 phenotypic macrophages or M2 macrophage inducer have been widely used to promote tissue remodeling. In this study, ultrasound-responsive bioactive microdroplets (MDs) encapsulated with bioactive molecule interleukin-4 (IL4, hereafter designated MDs-IL4) were fabricated to regulate macrophage polarization and potentiate the osteogenic differentiation of human mesenchymal stem cells (hBMSCs).

Materials and methods: The MTT assay, live and dead staining, and phalloidin/DAPI dual staining were used to evaluate biocompatibility in vitro. H&E staining was used to evaluate biocompatibility in vivo. Inflammatory macrophages were further induced via lipopolysaccharide (LPS) stimulation to mimic the pro-inflammatory condition. The immunoregulatory role of the MDs-IL4 was tested via macrophage phenotypic marker gene expression, pro-inflammatory cytokine level, cell morphological analysis, and immunofluorescence staining, etc. The immune-osteogenic response of hBMSCs via macrophages and hBMSCs interactions was further investigated in vitro.

Results: The bioactive MDs-IL4 scaffold showed good cytocompatibility in RAW 264.7 macrophages and hBMSCs. The results confirmed that the bioactive MDs-IL4 scaffold could reduce inflammatory phenotypic macrophages, as evidenced by changing in morphological features, reduction in pro-inflammatory marker gene expression, increase of M2 phenotypic marker genes, and inhibition of pro-inflammatory cytokine secretion. Additionally, our results indicate that the bioactive MDs-IL4 could significantly enhance the osteogenic differentiation of hBMSCs via its potential immunomodulatory properties.

Conclusion: Our results demonstrate that the bioactive MDs-IL4 scaffold could be used as novel carrier system for other pro-osteogenic molecules, thus having potential applications in bone tissue regeneration.

Keywords: IL-4; bioactive microdroplets; biocompatibility; immunoregulation; macrophages; osteogenesis.

MeSH terms

  • Bone and Bones
  • Cell Differentiation
  • Cytokines
  • Humans
  • Immunologic Factors
  • Inflammation / drug therapy
  • Inflammation / metabolism
  • Interleukin-4* / metabolism
  • Osteogenesis*

Substances

  • Interleukin-4
  • Cytokines
  • Immunologic Factors

Grants and funding

This work was financially supported by the National Natural Science Foundation of China (Grant No. 82060620 and 31960209), Outstanding Youth Scientific Fund of Guizhou Province (Qian Ke He Platform Talents [2023] 5639), Guizhou Science and Technology Program Project (Grant No. Qiankehe Foundation - ZK[2023] General 502), Guizhou Science and Technology Fund Project (Grant No. [2020]1Y093), Zunyi Science and Technology Fund Project (Grant No. Zunyi Kehe HZ Zi [2021]40), Future Eminent Clinician Plan of Zunyi Medical University (Grant No. 2022-02) and Doctoral Science Research Startup Funding of Zunyi Medical University (Grant No. F-934 and No. 2017-01).