Targeting VGLL4 maintains extracellular matrix homeostasis and mitigates osteoarthritis in a preclinical model

Extracellular matrix homeostasis is crucial for hyaline cartilage integrity, however, the mechanism of extracellular matrix homeostasis in hyaline cartilage is poorly understood. Single-cell sequencing shows that VGLL4 is highly expressed in chondrocytes but declines after injury/aging. VGLL4 deficiency impairs collagen/elastin formation, causes extracellular matrix disorganization and osteoarthritis in Col2-CreERT2; Vgll4^fl/fl mice, and is exacerbated by destabilization of the medial meniscus surgery. Mechanistically, the VGLL4-TEAD-SMAD3 complex maintains extracellular matrix homeostasis through specific interactions: TEAD4 (E263/D266/ Q269/H427) binds SMAD3 (K81/F260) via hydrogen bonds and hydrophobic contacts, while VGLL4 (H240/F241) engages TEAD4 (F337/F373) through π-stacking. Notably, intra-articular delivery of adeno-associated virus encoding either SMAD3 or VGLL4 effectively ameliorates osteoarthritis pathology, whereas interaction-deficient mutants lose therapeutic efficacy. This study demonstrates that VGLL4 serves as a critical regulator of extracellular matrix homeostasis in chondrocytes. The VGLL4 complex represents a potential therapeutic target for treating osteoarthritis and cartilage fibrosis.