Capacitative calcium entry and proliferation of human osteoblast-like MG-63 cells.
Adult bone tissue is continuously being remodelled and bone mass is maintained by a balance between osteoclastic bone resorption and osteoblastic bone formation. Alteration of osteoblastic cell proliferation may account in part for lack of balance between these two processes in bone loss of osteoporosis. There is calcium (Ca2+) control in numerous cellular functions; however, involvement of capacitative Ca2+ entry (CCE) in proliferation of bone cells is less well investigated.


OBJECTIVE
The study described here was aimed to investigate roles of CCE in the proliferation of osteoblast-like MG-63 cells.


METHODS
Pharmacological characterizations of CCE were undertaken in parallel, with evaluation of the expression of transient receptor potential canonical (TRPC) channels and of cell proliferation.


RESULTS
Intracellular Ca2+ store depletion by thapsigargin induced CCE in MG-63 cells; this was characterized by a rapid transient increase of intracellular Ca2+ followed by significant CCE, induced by conditions that stimulated cell proliferation, namely serum and platelet-derived growth factor. Inhibitors of store-operated Ca2+ channels (2-APB and SKF-96365) prevented CCE, while voltage-dependent Ca2+ channel blockers had no effect. Expression of various TRPC channels was shown in the cells, some having been shown to be responsible for CCE. Voltage-dependent Ca2+ channel blockers had no effect on osteoblast proliferation while thapsigargin, 2-APB and SKF-96395, inhibited it. Cell cycle analysis showed that 2-APB and SKF-96395 lengthen the S and G2/M phases, which would account for the reduction in cell proliferation.


CONCLUSIONS
Our results indicate that CCE, likely attributed to the activation of TRPCs, might be the main route for Ca2+ influx involved in osteoblast proliferation.
Labelle
D
D
Laboratoire du métabolisme osseux, Centre BioMed, Université du Québec à Montréal, Québec, Canada.
Jumarie
C
C
Moreau
R
R
D000818:Animals; D000077214:Becaplermin; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D025802:Electric Capacitance; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D051379:Mice; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D044967:Serum; D019284:Thapsigargin / Q000494:pharmacology; D050051:Transient Receptor Potential Channels / Q000235:genetics / Q000378:metabolism
D001896:Boron Compounds; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D007093:Imidazoles; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D050051:Transient Receptor Potential Channels; D000077214:Becaplermin; D019284:Thapsigargin; C109986:2-aminoethoxydiphenyl borate; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium