Apoptosis of osteoclast-like cells induced by alendronate is related to Fas gene expression.
OBJECTIVE
To detect the mechanism of alendronate during inhibition of bone resorption by inducing apoptosis of osteoclasts and its relationship with the Fas gene.


METHODS
The osteoclast-like cells (OCLs) from a giant cell tumor in vitro were used. After treatment with alendronate for 48 hours, the OCLs were identified by fluorescence microscope, transmission electron microscope, in situ end labeling (TUNEL), HE staining, in situ hybridization with Dig-Fas Probe, and immunohistochemistry with anti-Fas antibodies.


RESULTS
The detachment rate of OCLs was 76% after exposure to alendronate, while the control cell detachment rate was only 3%. The nonadherent OCLs showed the features of cell contraction, pyknosis, chromatin condensation connecting with nuclear membrane to form circle or crescent bodies, and occasional nuclear fragmentation. The detached OCLs were positive by in situ end labeling, and the control group was negative. Nonadherent OCLs were ultrastructurally consistent with apoptosis (shrunken cells with pyknotic nuclei, chromatin condensation connecting with nuclear membrane, mitochondria recruitment with intact structure, and loosening of endoplasmic reticulum). The results by in situ hybridization and immunohistochemistry indicated that the Fas gene expression of nonadherent OCLs were positive, but the controls were negative.


CONCLUSIONS
Alendronate promotes apoptosis of the OCLs and it is related with the expression of the Fas gene.
Wang
X M
XM
Department of Oral Pathology, School of Stomatology, BMU, 38 Bai Shi Qiao Road, Haidian District, Beijing 100081, P. R. China.
Yu
S F
SF
Yang
Z P
ZP
D019386:Alendronate / Q000494:pharmacology*; D000911:Antibodies, Monoclonal; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001862:Bone Resorption / Q000473:pathology; D002448:Cell Adhesion / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects; D002843:Chromatin / Q000187:drug effects; D004396:Coloring Agents; D005456:Fluorescent Dyes; D015870:Gene Expression; D018212:Giant Cell Tumor of Bone / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D020287:In Situ Nick-End Labeling; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009685:Nuclear Envelope / Q000187:drug effects; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000187:drug effects / Q000235:genetics*
D000911:Antibodies, Monoclonal; D002843:Chromatin; D004396:Coloring Agents; D005456:Fluorescent Dyes; D019014:fas Receptor; D019386:Alendronate