PDGF-BB inhibits SP1/Angptl7 mediated chondro-endothelial crosstalk via stress-sensitivity Piezo1 regulation in osteoarthritis.

INTRODUCTION

Osteoarthritis (OA) involves cartilage degradation and subchondral bone alterations, yet the mechanisms of chondro-endothelial crosstalk remain unclear. Stress-sensitive Piezo1 and SP1/Angptl7 signaling may play key roles in this process. This research aimed to investigate whether Platelet-derived growth factor (PDGF)-BB regulates chondro-endothelial crosstalk via Piezo1-mediated SP1/Angptl7 inhibition.

METHODS

Single- and multiple-cell-component organoids (chondrocytes SW1353 and endothelial HMEC-1) were constructed using high-throughput 3D culture. Organoids were treated with MIA to induce OA-like changes, followed by PDGF-BB with or without Yoda1 (Piezo1 activator) or Angptl7. In vivo, OA was induced in rats by intraarticular MIA injection, and PDGF-BB or sodium hyaluronate (SH)-PDGF was administered. Histology and immunofluorescence were used to assess F-actin formation, Piezo1 activation, SP1 phosphorylation, Angptl7 and VEGF/Notch/DLL4 expression.

RESULTS

PDGF-BB inhibited F-actin formation and reduced Piezo1 activation in OA chondrocytes. It suppressed SP1 phosphorylation and Angptl7 expression, downregulating VEGF/Notch/DLL4 signaling and reducing endothelial invasion in organoids. These effects were partially reversed by Yoda1 and fully reversed by Angptl7. In vivo, PDGF-BB and SH-PDGF attenuated cartilage degeneration and reduced Piezo1 activation, SP1 phosphorylation, and Angptl7 expression.

DISCUSSION: PDGF-BB alleviates OA by inhibiting SP1/Angptl7-mediated chondro-endothelial crosstalk, partially via stress-sensitive Piezo1 regulation through cytoskeletal remodeling. Multiple-cell-component organoids provide a valuable in vitro model for studying cartilage pathophysiology.