Vascular Endothelial Growth Factor (VEGF)-induced Up-regulation of CCN1 in Osteoblasts Mediates Proangiogenic Activities in Endothelial Cells and Promotes Fracture Healing

Abstract

Angiogenesis is indispensable during fracture repair, and vascular endothelial growth factor (VEGF) is critical in this process. CCN1 (CYR61) is an extracellular matrix signaling molecule that has been implicated in neovascularization through its interactions with several endothelial integrin receptors. CCN1 has been shown to be up-regulated during the reparative phase of fracture healing; however, the role of CCN1 therein remains unclear. Here, the regulation of CCN1 expression in osteoblasts and the functional consequences thereof were studied. Stimulation of osteoblasts with VEGF resulted in a dose-and time-dependent up-regulation of CCN1 mRNA and protein. An up-regulation of both cell surface-associated CCN1 as well as extracellular matrix-associated CCN1 in osteoblasts was found. The supernatant of VEGF-prestimulated osteoblasts was chemotactic for endothelial cells, increasing their migration and stimulated capillary-like sprout formation. These effects could be attributed to the presence of CCN1 in the osteoblast supernatant as they were prevented by an antibody against CCN1 or by small interfering RNA-mediated knockdown of osteoblast CCN1. Moreover, the supernatant of VEGF-prestimulated osteoblasts induced angiogenesis in Matrigel plugs in vivo in a CCN1-dependent manner. In addition, blockade of CCN1 prevented bone fracture healing in mice. Taken together, the present work demonstrates a potential paracrine loop consisting of the VEGF-mediated up-regulation of CCN1 in osteoblasts that attracts endothelial cells and promotes angiogenesis. Such a loop could be operative during fracture healing.

Positive effect of tadalafil, a phosphodiesterase-5 inhibitor, on fracture healing in rat femur

“…VEGF activity is essential for normal angiogenesis as well as appropriate callus architecture and mineralization in response to bone injury. It was demonstrated that sildenafil induced VEGF expression in human coronary arteriolar endothelial cells as an angiogenic response; [23] however, the same effect was not observed in fracture healing by Histing et al [11] Their results might have been due to the time when analysis was performed. Local levels of endogenous VEGF peak at five days and decrease toward normal levels at day 10 after fracture [24] or bony injury.…”

“…[18,19] Angiogenic processes play a crucial role in the very early stages of fracture healing, affecting both endochondral and intramembranous pathways of osteogenesis. [20][21][22] Hausman et al [23] reported that antiangiogenic agents severely impair fracture healing by causing defective granulation tissue, absence of cartilage differentiation, and endochondral ossification. VEGF activity is essential for normal angiogenesis as well as appropriate callus architecture and mineralization in response to bone injury.…”

DJ-1 promotes angiogenesis and osteogenesis by activating FGF receptor-1 signaling

“…In particular, cell-to-cell communication between diverse cell-types, such as endothelial cells, osteoblasts, osteoclasts and fibroblasts, is vital to the healing process [12][13][14] . Impaired bone healing is associated with a reduction in vascular supply and limited nutrient availability at the site of injury, suggesting that an impaired angiogenic response is a major cause for this pathology [13][14][15][16][17] .…”

CCN1 Promotes VEGF Production in Osteoblasts and Induces Endothelial Progenitor Cell Angiogenesis by Inhibiting miR-126 Expression in Rheumatoid Arthritis

“…(35) Several lines of evidence in this study show that VEGF expression in osteoblasts is regulated by CCN1. First, treatment of osteoblasts with CCN1 increased VEGF mRNA and protein expression.…”