VEGF-C, a lymphatic growth factor, is a RANKL target gene in osteoclasts that enhances osteoclastic bone resorption through an autocrine mechanism.
Osteoclasts are bone-resorbing cells, but they also secrete and respond to cytokines. Here, we test the hypothesis that osteoclasts secrete the lymphatic growth factor, VEGF-C, to increase their resorptive activity. Osteoclasts and osteoclast precursors were generated by culturing splenocytes with macrophage colony-stimulating factor and RANKL from wild-type, NF-kappaBp50(-/-)/p52(-/-), and Src(-/-) mice. Expression of VEGFs was measured by real time reverse transcription-PCR, Western blotting, and immunostaining. The effect of VEGF-C signaling on osteoclast function was determined by osteoclastogenesis and pit assays. RANKL increased the expression of VEGF-C but not of other VEGFs in osteoclasts and their precursors. RANKL-induced VEGF-C expression was reduced in NF-kappaBp50(-/-)/p52(-/-) precursors or wild-type cells treated with an NF-kappaB inhibitor. VEGF-C directly stimulated RANKL-mediated bone resorption, which was reduced by the VEGF-C-specific receptor blocker, VEGFR3:Fc. Osteoclasts express VEGFR3, and VEGF-C stimulated Src phosphorylation in osteoclasts. VEGF-C-mediated bone resorption was abolished in Src(-/-) osteoclasts or cells treated with an Src inhibitor. We conclude that RANKL stimulates osteoclasts and their precursors to release VEGF-C through an NF-kappaB-dependent mechanism, indicating that VEGF-C is a new RANKL target gene in osteoclasts and functions as an autocrine factor regulating osteoclast activity.
Zhang
Qian
Q
Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, New York 14642, USA.
Guo
Ruolin
R
Lu
Yan
Y
Zhao
Lan
L
Zhou
Quan
Q
Schwarz
Edward M
EM
Huang
Jing
J
Chen
Di
D
Jin
Zheng-Gen
ZG
Boyce
Brendan F
BF
Xing
Lianping
L
D000818:Animals; D019898:Autocrine Communication / Q000187:drug effects*; D001862:Bone Resorption / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D008214:Lymphocytes / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010010:Osteoclasts / Q000187:drug effects* / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D053245:RANK Ligand / Q000494:pharmacology*; D015398:Signal Transduction; D042582:Vascular Endothelial Growth Factor C / Q000235:genetics / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism
D053245:RANK Ligand; D042582:Vascular Endothelial Growth Factor C; D019061:src-Family Kinases