A specific subtype of osteoclasts secretes factors inducing nodule formation by osteoblasts

TY - JOUR

T1 - A specific subtype of osteoclasts secretes factors inducing nodule formation by osteoblasts

AU - Henriksen, Kim

AU - Andreassen, Kim V

AU - Thudium, Christian S

AU - Gudmann, Karoline Natasja Stæhr

AU - Moscatelli, Ilana

AU - Crüger-Hansen, Catherine E

AU - Schulz, Ansgar S

AU - Dziegiel, Morten Hanefeld

AU - Richter, Johan

AU - Karsdal, Morten A

AU - Neutzsky-Wulff, Anita V

N1 - Copyright © 2012 Elsevier Inc. All rights reserved.

PY - 2012/9

Y1 - 2012/9

N2 - Osteoclasts are known to be important for the coupling process between bone resorption and formation. The aim of this study was to address when osteoclasts are anabolically active. Human monocytes were differentiated into mature osteoclasts by treatment with M-CSF and RANKL. Conditioned medium was collected from macrophages, pre-osteoclasts, and mature functional or non-resorbing osteopetrotic osteoclasts on either bone, plastic, decalcified bone or dentine with or without diphyllin, E64 or GM6001. Osteoclasts numbers were measured by TRACP activity. Bone resorption was evaluated by CTX-I and calcium release. The osteoblastic cell line 2T3 was treated with 50% of CM or non-CM for 12days. Bone formation was assessed by Alizarin Red extraction. CM from mature osteoclasts induced bone formation, while CM from macrophages did not. Non-resorbing osteoclasts generated from osteopetrosis patients showed little resorption, but still an induction of bone formation by osteoblasts. Mimicking the reduction in bone resorption using the V-ATPase inhibitor Diphyllin, the cysteine proteinase inhibitor E64 and the MMP-inhibitor GM6001 showed that CM from diphyllin and E64 treated osteoclasts showed reduced ability to induce bone formation compared to CM from vehicle treated osteoclasts, while CM from GM6001 treated osteoclasts equaled vehicle CM. Osteoclasts on either dentine or decalcified bone showed strongly attenuated anabolic capacities. In conclusion, we present evidence that osteoclasts, both dependent and independent of their resorptive activity, secrete factors stimulating osteoblastic bone formation.

AB - Osteoclasts are known to be important for the coupling process between bone resorption and formation. The aim of this study was to address when osteoclasts are anabolically active. Human monocytes were differentiated into mature osteoclasts by treatment with M-CSF and RANKL. Conditioned medium was collected from macrophages, pre-osteoclasts, and mature functional or non-resorbing osteopetrotic osteoclasts on either bone, plastic, decalcified bone or dentine with or without diphyllin, E64 or GM6001. Osteoclasts numbers were measured by TRACP activity. Bone resorption was evaluated by CTX-I and calcium release. The osteoblastic cell line 2T3 was treated with 50% of CM or non-CM for 12days. Bone formation was assessed by Alizarin Red extraction. CM from mature osteoclasts induced bone formation, while CM from macrophages did not. Non-resorbing osteoclasts generated from osteopetrosis patients showed little resorption, but still an induction of bone formation by osteoblasts. Mimicking the reduction in bone resorption using the V-ATPase inhibitor Diphyllin, the cysteine proteinase inhibitor E64 and the MMP-inhibitor GM6001 showed that CM from diphyllin and E64 treated osteoclasts showed reduced ability to induce bone formation compared to CM from vehicle treated osteoclasts, while CM from GM6001 treated osteoclasts equaled vehicle CM. Osteoclasts on either dentine or decalcified bone showed strongly attenuated anabolic capacities. In conclusion, we present evidence that osteoclasts, both dependent and independent of their resorptive activity, secrete factors stimulating osteoblastic bone formation.

KW - Bone Density Conservation Agents

KW - Bone Matrix

KW - Bone Resorption

KW - Bone and Bones

KW - Cell Differentiation

KW - Cells, Cultured

KW - Dentin

KW - Humans

KW - Osteoblasts

KW - Osteoclasts

KW - Osteogenesis

KW - Time Factors

U2 - 10.1016/j.bone.2012.06.007

DO - 10.1016/j.bone.2012.06.007

M3 - Journal article

C2 - 22722081

SN - 0914-7047

VL - 51

SP - 353

EP - 361

JO - The Bone

JF - The Bone

IS - 3

ER -