Angiogenesis is uncoupled from osteogenesis during calvarial bone regeneration

• Published in: Nature communications 2024-06, Vol.15 (1), p.4575-22, Article 4575
• Main Authors: Bixel, M. Gabriele, Sivaraj, Kishor K., Timmen, Melanie, Mohanakrishnan, Vishal, Aravamudhan, Anusha, Adams, Susanne, Koh, Bong-Ihn, Jeong, Hyun-Woo, Kruse, Kai, Stange, Richard, Adams, Ralf H.
• Format: Article
• Language: English
• Subjects: 13/1; 14; 14/69; 38/91; 42/34; 49/39; 631/136/815/816; 631/443/63; 631/80/84/750; 64/110; Angiogenesis; Animals; Bioengineering; Blood flow; Blood vessels; Bone blood flow; Bone growth; Bone healing; Bone Regeneration - physiology; Bones; Female; Femur; Fractures; Healing; Hemopoiesis; Heterogeneity; Humanities and Social Sciences; Hypoxia; Lesions; Long bone; Male; Mesenchymal stem cells; Mesenchymal Stem Cells - cytology; Mesenchymal Stem Cells - metabolism; Mice; Mice, Inbred C57BL; multidisciplinary; Neovascularization, Physiologic; Ossification; Osteoblasts; Osteoblasts - cytology; Osteoblasts - metabolism; Osteogenesis; Osteoprogenitor cells; Periosteum; Receptors, Notch - genetics; Receptors, Notch - metabolism; Regeneration; Regeneration (physiology); Science; Science (multidisciplinary); Signal Transduction; Skull; Vascular endothelial growth factor; Vascular Endothelial Growth Factor A - metabolism; Vascularization
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-48579-5

Bone regeneration requires a well-orchestrated cellular and molecular response including robust vascularization and recruitment of mesenchymal and osteogenic cells. In femoral fractures, angiogenesis and osteogenesis are closely coupled during the complex healing process. Here, we show with advanced longitudinal intravital multiphoton microscopy that early vascular sprouting is not directly coupled to osteoprogenitor invasion during calvarial bone regeneration. Early osteoprogenitors emerging from the periosteum give rise to bone-forming osteoblasts at the injured calvarial bone edge. Microvessels growing inside the lesions are not associated with osteoprogenitors. Subsequently, osteogenic cells collectively invade the vascularized and perfused lesion as a multicellular layer, thereby advancing regenerative ossification. Vascular sprouting and remodeling result in dynamic blood flow alterations to accommodate the growing bone. Single cell profiling of injured calvarial bones demonstrates mesenchymal stromal cell heterogeneity comparable to femoral fractures with increase in cell types promoting bone regeneration. Expression of angiogenesis and hypoxia-related genes are slightly elevated reflecting ossification of a vascularized lesion site. Endothelial Notch and VEGF signaling alter vascular growth in calvarial bone repair without affecting the ossification progress. Our findings may have clinical implications for bone regeneration and bioengineering approaches. Fractured long bones regenerate through osteo-angiogenic coupling, but how calvarial bone healing occurs is not yet clear. Here they show that regenerating blood vessels separate from co-migrating progenitors in calvarial bones, resulting in osteoblasts mineralizing a previously vascularized lesion.