Hyperlipidemia-induced metabolic dysregulation impairs tendon homeostasis: the role of TGF-β/Smad2 signaling pathway in lipid-mediated extracellular matrix remodeling.

Hyperlipidemia is a globally prevalent metabolic disorder, and the lipid metabolic dysregulation it induces is closely associated with the onset and progression of tendon pathologies, which are typically characterized by ECM dyshomeostasis, disorganized collagen fiber structure and impaired biomechanical properties in the affected tendons. The TGF-β signaling pathway serves as a central regulator of tendon ECM metabolic homeostasis, among which the TGF-β/Smad2 axis can directly mediate the balanced regulation of collagen synthesis and degradation in tendons, yet its specific role and underlying molecular mechanism in hyperlipidemia-induced tendon ECM dysfunction remain poorly defined. We examined how oxidized lipids affect the TGF-β/Smad2 signaling axis in tendon tissue. Specifically, we assessed TβRII localization within lipid rafts, TGF-β activation, downstream transcription of Col1a1 and lysyl oxidase (LOX), and matrix metalloproteinase-1 (MMP-1) activity. Oxidized lipids disrupted TβRII localization in lipid rafts, leading to impaired TGF-β activation. This suppressed Smad2 signaling, decreased Col1a1 transcription and LOX expression, and increased MMP-1 activity. Consequently, tendon collagen synthesis declined while degradation rose, undermining structural integrity and intrinsic repair capacity. Hyperlipidemia-driven suppression of the TGF-β/Smad2 axis is the critical mechanism linking metabolic dysregulation to tendon matrix failure. Restoring TGF-β/Smad2 signaling represents a promising therapeutic strategy to mitigate hyperlipidemia-induced tendon damage and poor healing.