Dioxins interfere with differentiation of osteoblasts and osteoclasts.
We have previously shown that the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) affects bone growth, modelling and mechanical strength in vivo. In this study, we utilized differentiation of bone marrow stem cells to osteoblasts and osteoclasts as a model system to study the effects of TCDD on bones. Stem cells were isolated from bone marrow of femurs and tibias of rats and mice. Progress of osteoblastic differentiation was monitored by measuring mRNA expression levels of differentiation markers from control and TCDD-treated cells using quantitative RT-PCR. TCDD significantly and dose-dependently decreased the mRNA levels of RUNX2, alkaline phosphatase and osteocalcin. Also the activity of alkaline phosphatase was significantly inhibited in both rat and mice cells. In the case of osteoclasts, TCDD decreased the number of TRACP+ multinucleated cells, with corresponding decreases in the number of F-actin rings and the area of resorption. Studies in AHR-knockout mice indicated that TCDD has no effect on the expression of osteoblastic differentiation markers suggesting that TCDD mediates its effects by AHR. Both osteoblastic and osteoclastic effects took place at very low doses of TCDD, as in most cases 100 fM TCDD was enough to significantly affect the differentiation markers. Therefore, differentiation of osteoblasts and osteoclasts from bone marrow stem cells seems to be a very sensitive target for TCDD. Disrupting effects in osteoblastic cells, in addition to disturbed osteoclastogenesis, may thus play a role in adverse effects on bone quality in TCDD exposed animals.
Korkalainen
Merja
M
National Institute for Health and Welfare, Department of Environmental Health, P.O. Box 95, FI-70701 Kuopio, Finland. merja.korkalainen@thl.fi
Kallio
Elise
E
Olkku
Anu
A
Nelo
Katri
K
Ilvesaro
Joanna
J
Tuukkanen
Juha
J
Mahonen
Anitta
A
Viluksela
Matti
M
D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics; D004147:Dioxins / Q000633:toxicity*; D004785:Environmental Pollutants / Q000633:toxicity*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
D050659:Core Binding Factor Alpha 1 Subunit; D004147:Dioxins; D004785:Environmental Pollutants; D000072317:Polychlorinated Dibenzodioxins; C493716:Runx2 protein, mouse; D015675:Osteocalcin; D000469:Alkaline Phosphatase