Preliminary exploration of effects of the JAK inhibitor tofacitinib on pyoderma gangrenosum: In vitro inhibition of NETs and Th17 differentiation.

BACKGROUND: Pyoderma gangrenosum (PG), a refractory inflammatory disorder, remains a condition with incompletely understood pathogenesis. Currently, no FDA-approved treatments are available. Janus kinase (JAK) inhibitors have been reported sporadically in case studies as effective treatments for PG. OBJECTIVE: To characterize the cellular and molecular landscape associated with JAK/STAT (signal transducer and activator of transcription) pathway overactivation in PG lesions, and investigate the potential effects of tofacitinib on PG. METHODS: Single-cell RNA sequencing (scRNA-seq) and multiplex immunohistochemistry (mIHC) were employed to characterize the cellular and molecular landscape of JAK/STAT pathway overactivation in PG. In vitro experiments (immunostaining, qPCR, western blot, flow cytometry) were performed to further validate the potential effects of tofacitinib on PG. RESULTS: We identified significant overactivation of the JAK/STAT pathway in PG lesions-particularly in advanced stages-which, in terms of immune inflammation, is primarily driven by myeloid cells and T cells. This activation was associated with enhanced neutrophil extracellular trap (NET) formation in myeloid cells and aberrant differentiation/plasticity of Th17 and Th17.1 (IL-17/IFN-γ double-producing) cells. In vitro cell experiments further demonstrated that the JAK inhibitor tofacitinib suppresses STAT phosphorylation in myeloid and T cells, myeloid NETosis, and IL-17A production. CONCLUSION: Our study investigated immunological profiling of PG lesions via scRNA-seq and mIHC, along with in vitro validation. These findings delineate a multi-axis cellular and molecular landscape of PG linked to aberrant JAK/STAT signaling, and provide preliminary in vitro evidence supporting potential inhibitory effects of tofacitinib on key pathological processes of PG.