A lymphatic organ-on-a-chip reveals flow-responsive LEC paracrine signals promoting BMSC osteogenesis in jawbone...

The lymphatic system is essential for fluid homeostasis and immune surveillance, yet its role in skeletal regeneration remains poorly defined. Here, we introduce a biomimetic organ-on-a-chip (OoC) model that recapitulates lymphatic endothelial cell (LEC) behavior under precisely controlled flow-mediated environments and elucidates their regulatory contribution in alveolar bone repair. Under flow-mediated shear stress, LECs exhibited enhanced sprouting, forming lumenized lymphatic structures in vitro. Furthermore, conditioned medium from perfused LECs significantly promoted the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Mass spectrometry identified WISP1 as a key mechanoresponsive secreted factor with high levels in LECs that activated canonical Wnt signaling in BMSCs, thus contributing to enhanced osteogenic marker expression and mineralization. In vivo validation using a murine molar extraction model with controlled occlusal loading revealed that occlusal loading promoted lymphangiogenesis and accelerated alveolar bone regeneration, accompanied by elevated WISP1 expression within alveolar sockets. Conversely, pharmacological suppression of lymphatic expansion through MAZ51 administration impaired bone formation while reducing WISP1 levels, thereby confirming the functional contribution of lymphatic vessels in alveolar bone regeneration. Together, these findings demonstrate that LECs function as mechanoresponsive regulators that transduce shear-related cues into osteoinductive signals through WISP1-mediated paracrine communication. Our study uncovers a previously unrecognized lymphatic-osteogenic signaling axis and establishes a physiologically relevant OoC platform for systematic investigation of lymphatic mechanotransduction in bone regeneration.