L-type calcium channels in growth plate chondrocytes participate in endochondral ossification

• Published in: Journal of cellular biochemistry 2007-05, Vol.101 (2), p.389-398
• Main Authors: Mancilla, Edna E., Galindo, Mario, Fertilio, Barbara, Herrera, Mario, Salas, Karime, Gatica, Hector, Goecke, Annelise
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis - physiology; Bone and Bones - cytology; Bone and Bones - metabolism; Bone and Bones - physiology; bone growth; Calcium Channel Blockers - pharmacology; calcium channels; Calcium Channels, L-Type - metabolism; cartilage; chondrocytes; Chondrocytes - cytology; Chondrocytes - drug effects; Chondrocytes - metabolism; Diltiazem - pharmacology; growth plate; Growth Plate - cytology; Osteogenesis - drug effects; Osteogenesis - physiology; Rats; Rats, Sprague-Dawley; Verapamil - pharmacology
• ISSN: 0730-2312; 1097-4644
• DOI: 10.1002/jcb.21183

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 Ca2+ (Ca i2+) in this process. Indirect studies, using Ca2+ channel blockers and measurement of Ca i2+, have provided evidence for the existence of Ca2+ channels in growth plate chondrocytes. Furthermore, voltage‐gated Ca2+ 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 Ca2+ 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 Ca2+ 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 Ca2+ 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.