Increased Osteoblastic Cxcl9 Contributes to the Uncoupled Bone Formation and Resorption in Postmenopausal Osteoporosis
Received 27 March 2020
Accepted for publication 29 May 2020
Published 20 July 2020 Volume 2020:15 Pages 1201—1212
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 2
Editor who approved publication: Dr Zhi-Ying Wu
Zezheng Liu,1,* Wenquan Liang,1,* Dawei Kang,1 Qingjing Chen,1 Zhicong Ouyang,1 Huibo Yan,1 Bin Huang,1 Dadi Jin,1 Yinkui Chen,2 Qingchu Li1
1Academy of Orthopedics, Guangdong Province, Department of Spine Surgery, The Third Affiliated Hospital of Southern Medical University, Guangzhou, People’s Republic of China; 2Department of Oncology, The Third Affiliated Hospital of Southern Medical University, Guangzhou, People’s Republic of China
*These authors contributed equally to this work
Correspondence: Qingchu Li
Department of Spine Surgery, The Third Affiliated Hospital of Southern Medical University, Guangzhou, People’s Republic of China
Department of Oncology, The Third Affiliated Hospital of Southern Medical University, Guangzhou, People’s Republic of China
Introduction: Estrogen deficiency leads to bone loss in postmenopausal osteoporosis, because bone formation, albeit enhanced, fails to keep pace with the stimulated osteoclastic bone resorption. The mechanism driving this uncoupling is central to the pathogenesis of postmenopausal osteoporosis, which, however, remains poorly understood. We previously found that Cxcl9 secreted by osteoblasts inhibited osteogenesis in bone, while the roles of Cxcl9 on osteoclastic bone resorption and osteoporosis are unclear.
Materials and Methods: Postmenopausal osteoporosis mouse model was established by bilateral surgical ovariectomy (OVX). In situ hybridization was performed to detect Cxcl9 mRNA expression in bone. ELISA assay was conducted to assess Cxcl9 concentrations in bone and serum. Cxcl9 activity was blocked by its neutralizing antibody. Micro-CT was performed to determine the effects of Cxcl9 neutralization on bone structure. Cell Migration and adhesion assay were conducted to evaluate the effects of Cxcl9 on osteoclast activity. TRAP staining and Western blot were performed to assess osteoclast differentiation. CXCR3 antagonist NBI-74,330 or ERK antagonist SCH772984 was administered to osteoclast to study the effects of Cxcl9 on CXCR3/ERK signaling.
Results: Cxcl9 was expressed and secreted increasingly in OVX mice bone. Neutralizing Cxcl9 in bone marrow prevented bone loss in the mice by facilitating bone formation as well as inhibiting bone resorption. In vitro, Cxcl9 secreted from osteoblasts facilitated osteoclast precursors adhesion, migration and their differentiation into mature osteoclasts. The positive role of osteoblastic Cxcl9 on osteoclasts was eliminated by blocking CXCR3/ERK signaling in osteoclasts. Estrogen negatively regulated Cxcl9 expression and secretion in osteoblasts, explaining the increased Cxcl9 concentration in OVX mice bone.
Conclusion: Our study illustrates the roles of Cxcl9 in inhibiting bone formation and stimulating bone resorption in osteoporotic bone, therefore providing a possible therapeutic target to the treatment of postmenopausal osteoporosis.
Keywords: postmenopausal osteoporosis, bone resorption, osteoclast, Cxcl9
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