Background
Psoriasis, a T cell-mediated chronic inflammatory skin condition, is characterized by the interaction of T cells with various cell types, forming an inflammatory microenvironment that sustains psoriatic inflammation. The homeostasis of these tissue-resident T cells are supported by fibroblasts, the primary structural cells in the dermis. In psoriasis, there is an increased expression of matrix metalloproteinase 2 (MMP2), mediating the structural alterations of skin tissues and the modulation of inflammation. Additionally, the CD100-PLXNB2 axis is known to enhance psoriasis inflammation via keratinocytes, and CD103 levels are associated with the severity of psoriasis upon relapse.
Objective
To elucidate the role of fibroblasts and the MMP2/CD100 axis in modulating psoriasis inflammation.
Methods
CD100 expression and function in psoriasis were assessed using immunofluorescence, ELISA, single-cell transcriptome sequencing, cellular interaction analyses, and qRT-PCR. CD8+ T cells from psoriasis patients were isolated using magnetic beads to investigate the regulatory effect of MMP2 on CD100 expression on their membranes. Single-cell transcriptome sequencing, spatial transcriptome sequencing, mimetic timing analysis, immunofluorescence, and flow cytometry were utilized to determine the origin of MMP2 and its impact on CD103+CD8+ T cells. The hypotheses were further validated in vivo using MMP2 and CD100 inhibitors.
Results
Soluble CD100 (sCD100) was significantly upregulated in both psoriatic lesions and peripheral blood, amplifying psoriasis inflammation by promoting the production of inflammatory cytokines by keratinocytes, fibroblasts, and endothelial cells through the sCD100-PLXNB2 axis. Fibroblasts with high MMP2 expression (MMP2hi) exacerbate psoriasis symptoms by facilitating CD100 shedding from CD8+ T cell membranes. Additionally, it was demonstrated that fibroblasts enhance the upregulation of the CD8+ T cell residency factor CD103 in co-cultures with CD8+ T cells. Inhibitors targeting MMP2 and CD100 proved effective in reducing inflammation in a model of imiquimod-induced psoriasis.
Conclusion
Our findings underscore the pivotal role of MMP2hi fibroblasts in the amplification and recurrence of inflammatory responses in psoriasis. These fibroblasts augment psoriasis inflammation through the CD100-PLXNB2 axis by facilitating CD100 shedding on CD8+ T cell membranes and by upregulating CD103, thereby enhancing CD8+ T cell residency.
