Skeletal overexpression of connective tissue growth factor impairs bone formation and causes osteopenia.
Connective tissue growth factor (CTGF), a member of the CCN family of proteins, is expressed in skeletal cells, and the ctgf null mutation leads to neonatal lethality due to defects in skeletal development. To define the function of CTGF in the postnatal skeleton, we created transgenic mice overexpressing CTGF under the control of the human osteocalcin promoter. CTGF transgenic female and male mice exhibited a significant decrease in bone mineral density, compared with wild-type littermate controls. Bone histomorphometry revealed that CTGF overexpression caused decreased trabecular bone volume due to impaired osteoblastic activity because mineral apposition and bone formation rates were decreased. Osteoblast and osteoclast number and bone resorption were not altered. Calvarial osteoblasts and stromal cells from CTGF transgenics displayed decreased alkaline phosphatase and osteocalcin mRNA levels and reduced bone morphogenetic protein (BMP) signaling mothers against decapentaplegic, Wnt/beta-catenin, and IGF-I/Akt signaling. In conclusion, CTGF overexpression in vivo causes osteopenia, secondary to decreased bone formation, possibly by antagonizing BMP, Wnt, and IGF-I signaling and activity.
Department of Research, Saint Francis Hospital and Medical Center, 114 Woodland Street, Hartford, Connecticut 06105-1299, USA.
Anna
A
Smerdel-Ramoya
Stefano
S
Zanotti
Lisa
L
Stadmeyer
Deena
D
Durant
Ernesto
E
Canalis
D000818:Animals; D001851:Bone Diseases, Metabolic / Q000235:genetics*; D019485:Bone Morphogenetic Proteins / Q000502:physiology; D001842:Bone and Bones / Q000378:metabolism*; D002478:Cells, Cultured; D055513:Connective Tissue Growth Factor; D004622:Embryo, Mammalian; D005260:Female; D018507:Gene Expression Regulation, Developmental; D017874:Immediate-Early Proteins / Q000235:genetics* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D010006:Osteoblasts / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D010012:Osteogenesis / Q000235:genetics*; D011247:Pregnancy; D015398:Signal Transduction / Q000235:genetics; D015854:Up-Regulation; D051153:Wnt Proteins / Q000502:physiology
D019485:Bone Morphogenetic Proteins; C526317:CCN2 protein, human; C526318:CCN2 protein, mouse; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D051153:Wnt Proteins; D015675:Osteocalcin; D055513:Connective Tissue Growth Factor; D007334:Insulin-Like Growth Factor I