Endothelin-1 expression in long-term cultures of fetal rat calvarial osteoblasts: regulation by BMP-7.
Endothelin-1 (ET-1) is a vasoactive peptide that modulates bone metabolism via regulatory effects on osteoblasts, chondrocytes, and osteoclasts. While ET-1 may circulate in the blood stream, tissue-specific expression of this peptide is more physiologically relevant. In the present study we measured ET-1 synthesis in sections of fetal rat calvaria (FRC) and in cultured FRC osteoblasts. Regulation of ET-1 synthesis in FRC osteoblasts by bone morphogenetic protein-7 (BMP-7) and transforming growth factor-beta1 (TGF-beta1) also was examined. Immunohistochemical analysis revealed ET-1 staining in calvarial osteoblasts, endothelial cells, and osteocytes. ET-1 mRNA expression was detected in cultured FRC cells and ET-1 peptide was present in conditioned media. During long-term culture of FRC cells (26 days) ET-1 peptide production rose sharply and peaked during the time of cellular proliferation (Days 0-3) then returned to baseline levels by Day 18, when mineralized nodules were forming. Treatment of FRC cells with BMP-7 enhanced ET-1 levels by three-fold on Day 3 and enhanced nodule formation by 15-fold on Day 26. To determine whether ET-1 was involved in an autocrine manner in BMP-7-induced nodule formation, cells were cultured in the presence of BMP-7 and BQ-123, an ET(A) receptor antagonist. BQ-123 had no effect on nodule formation in control or BMP-7-treated cells, indicating that osteoblast-derived ET-1 regulates other cell types in vivo during the bone formation process.
Department of Biology, Trinity University, San Antonio, Texas 78212, USA. akitten@egcrc.net
A M
AM
Kitten
C J
CJ
Andrews
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D019332:Endothelin-1 / Q000032:analysis / Q000235:genetics*; D005333:Fetus / Q000166:cytology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D010006:Osteoblasts / Q000737:chemistry / Q000166:cytology* / Q000502:physiology*; D010456:Peptides, Cyclic / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012886:Skull / Q000166:cytology; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053773:Transforming Growth Factor beta1
D000959:Antihypertensive Agents; C525821:Bmp7 protein, rat; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D019332:Endothelin-1; D010456:Peptides, Cyclic; D012333:RNA, Messenger; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C072247:cyclo(Trp-Asp-Pro-Val-Leu)