Topical Application of Mesenchymal Stem Cell Exosomes Alleviates the Imiquimod Induced Psoriasis-Like Inflammation

Int J Mol Sci. 2021 Jan 13;22(2):720. doi: 10.3390/ijms22020720.


Severe psoriasis, a chronic inflammatory skin disease is increasingly being effectively managed by targeted immunotherapy but long-term immunotherapy poses health risk and loss of response. Therefore, there is a need for alternative therapy strategies. Mesenchymal stem/stromal cell (MSC) exosomes are widely known for their potent immunomodulatory properties. Here we investigated if topically applied MSC exosomes could alleviate psoriasis-associated inflammation. Topically applied fluorescent exosomes on human skin explants were confined primarily to the stratum corneum with <1% input fluorescence exiting the explant over a 24-h period. Nevertheless, topically applied MSC exosomes in a mouse model of imiquimod (IMQ) psoriasis significantly reduced IL-17 and terminal complement activation complex C5b-9 in the mouse skin. MSC exosomes were previously shown to inhibit complement activation, specifically C5b-9 complex formation through CD59. Infiltration of neutrophils into the stratum corneum is characteristic of psoriasis and neutrophils are a major cellular source of IL-17 in psoriasis through the release of neutrophil extracellular traps (NETs). We propose that topically applied MSC exosomes inhibit complement activation in the stratum corneum and this alleviates IL-17 release by NETS from neutrophils that accumulate in and beneath the stratum corneum.

Keywords: exosome; mesenchymal stem cell; psoriasis.

MeSH terms

  • Administration, Topical
  • Animals
  • Biomarkers
  • Biopsy
  • Disease Models, Animal
  • Exosomes / metabolism*
  • Imiquimod / adverse effects*
  • Mesenchymal Stem Cells / metabolism*
  • Mice
  • Permeability
  • Phenotype
  • Psoriasis / etiology*
  • Psoriasis / pathology*
  • Psoriasis / therapy
  • Skin / drug effects
  • Skin / metabolism
  • Skin / pathology
  • Skin Absorption


  • Biomarkers
  • Imiquimod