Characterization of osteoclasts from patients harboring a G215R mutation in ClC-7 causing autosomal dominant osteopetrosis type II

TY - JOUR

T1 - Characterization of osteoclasts from patients harboring a G215R mutation in ClC-7 causing autosomal dominant osteopetrosis type II

AU - Henriksen, Kim

AU - Gram, Jeppe

AU - Schaller, Sophie

AU - Dahl, Bjarne H

AU - Dziegiel, Morten Hanefeld

AU - Bollerslev, Jens

AU - Karsdal, Morten A

PY - 2004/5

Y1 - 2004/5

N2 - Autosomal dominant osteopetrosis II (ADOII) is a relatively benign disorder caused by a missense mutation in the ClCN7 gene. In this study, we characterize the osteoclasts from patients with ADOII, caused by a G215R mutation, and investigate the effect on osteoclast function in vitro. Osteoclasts from ADOII patients and healthy age- and sex-matched controls, were used to evaluate osteoclastogenesis, cell fusion, acidification, and resorptive activity. ADOII osteoclasts in vivo have increased number and size. However, in vitro we observed no significant changes in the osteoclast formation rate, the morphology, and the expression of markers, such as cathepsin K and tartrate-resistant acid phosphatase. When mature ADOII osteoclasts were investigated on mineralized bone, they degraded the bone material, however only to 10 to 20% of the level in controls. We show by acridine orange, that the reduced chloride transport leads to reduced acidification. We show that the residual activity is sensitive to inhibitors of cathepsins and chloride channels, confirming that resorption is reduced but present. In conclusion, this is the first functional in vitro study of human ADOII osteoclasts. We show normal osteoclastogenesis in ADOII osteoclasts. However, the residual activity of the ClC-7 channel in ADOII osteoclasts does not allow sufficient acidification and thereby resorption.

AB - Autosomal dominant osteopetrosis II (ADOII) is a relatively benign disorder caused by a missense mutation in the ClCN7 gene. In this study, we characterize the osteoclasts from patients with ADOII, caused by a G215R mutation, and investigate the effect on osteoclast function in vitro. Osteoclasts from ADOII patients and healthy age- and sex-matched controls, were used to evaluate osteoclastogenesis, cell fusion, acidification, and resorptive activity. ADOII osteoclasts in vivo have increased number and size. However, in vitro we observed no significant changes in the osteoclast formation rate, the morphology, and the expression of markers, such as cathepsin K and tartrate-resistant acid phosphatase. When mature ADOII osteoclasts were investigated on mineralized bone, they degraded the bone material, however only to 10 to 20% of the level in controls. We show by acridine orange, that the reduced chloride transport leads to reduced acidification. We show that the residual activity is sensitive to inhibitors of cathepsins and chloride channels, confirming that resorption is reduced but present. In conclusion, this is the first functional in vitro study of human ADOII osteoclasts. We show normal osteoclastogenesis in ADOII osteoclasts. However, the residual activity of the ClC-7 channel in ADOII osteoclasts does not allow sufficient acidification and thereby resorption.

KW - Acid Phosphatase

KW - Acridine Orange

KW - Age Factors

KW - Antigens, CD14

KW - Biological Transport

KW - Bone Resorption

KW - Calcium Phosphates

KW - Cathepsin K

KW - Cathepsins

KW - Cell Differentiation

KW - Cell Fusion

KW - Chloride Channels

KW - Chlorides

KW - Enzyme Inhibitors

KW - Humans

KW - Immunoblotting

KW - Immunohistochemistry

KW - Isoenzymes

KW - Macrolides

KW - Monocytes

KW - Mutation

KW - Osteoclasts

KW - Osteopetrosis

KW - Sex Factors

KW - Time Factors

U2 - 10.1016/S0002-9440(10)63712-1

DO - 10.1016/S0002-9440(10)63712-1

M3 - Journal article

C2 - 15111300

SN - 0002-9440

VL - 164

SP - 1537

EP - 1545

JO - American Journal of Pathology

JF - American Journal of Pathology

IS - 5

ER -