PEGylated black-phosphorus nanosheet–alginate hydrogels enable local PRRX1 delivery to drive fibroblast reprogramming in intestinal fibrosis

Intestinal fibrosis drives stricturing complications in Crohn's disease (CD), yet the core stromal regulators remain incompletely defined. Here, we profile paired fibrotic and non-fibrotic ileum from CD patients using single-cell RNA sequencing and identify a selective expansion of fibroblasts enriched for an ECM-high transcriptional program. Among candidate transcription factors, PRRX1 was consistently upregulated in fibrotic regions and validated at transcript and protein levels. Functional interrogation using a Col1a2-Cre; Prrx1^fl/fl mouse model demonstrated that fibroblast-specific deletion of Prrx1 mitigated DNBS-induced fibrosis, confirming its pathogenic role in vivo. To complement this loss-of-function approach, we developed a PEGylated black phosphorus-alginate hydrogel (PRRX1@BP-PEG/Alg) for intrarectal delivery of recombinant PRRX1. This system exhibited high protein loading, mucosal adhesion, and controlled release. PRRX1 delivery reprogrammed human intestinal fibroblasts toward a matrix-producing phenotype, elevating FAP and COL1A1 expression and enriching profibrotic pathways. In vivo, PRRX1@BP-PEG/Alg exacerbated histological fibrosis and mesenchymal activation, as confirmed by colon proteomics. ChIP-seq and reporter assays further identified PRRX1 as a direct transactivator of the Fap promoter. Together, these data define a PRRX1-FAP regulatory axis driving fibroblast activation and intestinal fibrosis.