L-type calcium channels in growth plate chondrocytes participate in endochondral ossification
✍ Scribed by Edna E. Mancilla; Mario Galindo; Barbara Fertilio; Mario Herrera; Karime Salas; Hector Gatica; Annelise Goecke
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 397 KB
- Volume
- 101
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
Abstract
Longitudinal bone growth occurs by a process called endochondral ossification that includes chondrocyte proliferation, differentiation, and apoptosis. Recent studies have suggested a regulatory role for intracellular Ca^2+^ (Ca) in this process. Indirect studies, using Ca^2+^ channel blockers and measurement of Ca, have provided evidence for the existence of Ca^2+^ channels in growth plate chondrocytes. Furthermore, voltage‐gated Ca^2+^ channels (VGCC), and specifically L‐ and T‐type VGCCs, have been recently described in murine embryonic growth plates. Our aim was to assess the effect of L‐type Ca^2+^ channel blockers on endochondral ossification in an organ culture. We used cultures of fetal rat metatarsal rudiments at 20 days post gestational age, with the addition of the L‐type Ca^2+^ channel blockers verapamil (10–100 µM) or diltiazem (10–200 µM) to the culture medium. Longitudinal bone growth, chondrocyte differentiation (number of hypertrophic chondrocytes), and cell proliferation (incorporation of tritiated thymidine) were measured. Verapamil dose‐dependently decreased growth, the number of hypertrophic chondrocytes, and cell proliferation, at concentrations of 10–100 µM. Growth and the number of hypertrophic chondrocytes decreased significantly with diltiazem at 50–100 µM, and proliferation decreased significantly at concentrations of 10–200 µM. Additionally, there was no increase in apoptosis over physiological levels with either drug. We confirmed the presence of L‐type VGCCs in rat rudiments using immunohistochemistry, and showed that the antagonists did not alter the pattern of VGCC expression. In conclusion, our data suggest that L‐type Ca^2+^ channel activity in growth plate chondrocytes is necessary for normal longitudinal growth, participating in chondrocyte proliferation and differentiation. J. Cell. Biochem. 101: 389–398, 2007. © 2007 Wiley‐Liss, Inc.