Scrnaseq Reveals Cellular Drivers Of Retrodiscal Tissue Adaptation Following Add

Adaptive remodeling of retrodiscal tissue following anterior disc displacement (ADD) of temporomandibular joint (TMJ) has been recognized for decades, but its cellular mechanisms remain elusive. This study aims to resolve key drivers of retrodiscal tissue adaptation in a porcine ADD model. Six 5-month-old female Bama miniature pigs underwent surgery on the left TMJ (ADD group: disc displacement via nickel-titanium spring, n=3; Sham group: TMJ capsule exposure, n=3), approved by the Animal Ethics Committee of Zhejiang Chinese Medical University (20230227-08). After 5 weeks, discs and retrodiscal tissues were harvested and evaluated by histological staining. Single cell RNA sequencing (scRNA-seq) was performed and analyzed using Seurat package, CytoTRACE and CellChat. Primary porcine fibroblasts were treated with fibroblast growth factor 2 (FGF2) and bone morphogenetic protein 5 (BMP5) under chondrogenic induction, then evaluated by qRT-PCR and western blot. Adaptive remodeling occurred in retrodiscal tissue after ADD induction, with dense connective tissue replacing loose connective tissue and cartilaginous metaplasia. ScRNA-seq captured pronounced fibroblast expansion during remodeling, notably the subcluster FB1 with high developmental potential, and the emergence of mural cell subcluster MC4 linked to ECM remodeling. CellChat analysis highlighted MC4-FB1 crosstalk via FGF/BMP signaling. In vitro, FGF2 and BMP5 synergistically enhanced ECM synthesis and chondrogenic differentiation of fibroblasts. Fibroblast activation is pivotal for retrodiscal tissue adaptation following ADD, driven by MC4-derived FGF2/BMP5 signaling. These findings provide mechanistic insights into cellular interactions during retrodiscal tissue remodeling and offer therapeutic targets for ADD.