Scar management through modulation of the fibrotic microenvironment by CAR-Trem2-macrophages

Dipeptidyl peptidase 4 (Dpp4) plays a pivotal role in fibrotic and nonfunctional scar development following skin injury and is present in a subset of fibroblasts implicated in scar formation. Simultaneously, heterogeneous vascular endothelial cells (ECs) retain their capacity to drive tissue regeneration and repair within scarred areas. Effective strategies for inhibiting scar-associated fibroblasts and regulating EC subtypes in the scar microenvironment remain unclear. Here, we engineered CAR-Trem2-Ms capable of targeting DPP4+ fibroblasts and modulating EC phenotypes within the scar microenvironment to effectively prevent and treat scarring. Furthermore, compared to those in normal control samples, DPP4 expression levels were higher in both clinical scar databases and samples from scar patients. We transferred a CAR gene specifically targeting Dpp4+ fibroblasts into macrophages, which were then induced into CAR-Trem2-Ms with 1,25-dihydroxycholecalciferol (an active form of VD, VD3). Hydrogel micropore microneedles (mMNs) were employed to deliver CAR-Trem2-Ms to effectively alleviate scar formation. Single-cell transcriptome sequencing and analysis revealed that CAR-Trem2-Ms could modify EC phenotypes and regulate fibrosis by suppressing the profibrotic gene Lrg1. CAR-Trem2-Ms effectively inhibited fibrosis in fibroblasts induced by high EC LRG1 expression in vitro, further revealing the underlying mechanism by which CAR-Trem2-Ms exert their antifibrotic effects. Our findings offer a promising approach for treating post-traumatic scarring and provide novel insights into the pathological mechanisms underlying fibrosis.