Topic Highlight
Copyright ©2013 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Orthop. Oct 18, 2013; 4(4): 198-206
Published online Oct 18, 2013. doi: 10.5312/wjo.v4.i4.198
Role of osteoclasts in regulating hematopoietic stem and progenitor cells
Takeshi Miyamoto
Takeshi Miyamoto, Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan
Takeshi Miyamoto, Keio Kanrinmaru Project, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan
Takeshi Miyamoto, Department of Integrated Bone Metabolism and Immunology, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan
Author contributions: Miyamoto T solely contributed to this paper.
Correspondence to: Takeshi Miyamoto, MD, Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan. miyamoto@z5.keio.jp
Telephone: +81-3-53633812 Fax: +81-3-33536597
Received: October 10, 2012
Revised: December 19, 2012
Accepted: January 17, 2013
Published online: October 18, 2013
Abstract

Bone marrow (BM) cavities are utilized for hematopoiesis and to maintain hematopoietic stem cells (HSCs). HSCs have the ability to self-renew as well as to differentiate into multiple different hematopoietic lineage cells. HSCs produce their daughter cells throughout the lifespan of individuals and thus, maintaining HSCs is crucial for individual life. BM cavities provide a specialized microenvironment termed “niche” to support HSCs. Niches are composed of various types of cells such as osteoblasts, endothelial cells and reticular cells. Osteoclasts are unique cells which resorb bones and are required for BM cavity formation. Loss of osteoclast function or differentiation results in inhibition of BM cavity formation, an osteopetrotic phenotype. Osteoclasts are also reportedly required for hematopoietic stem and progenitor cell (HSPC) mobilization to the periphery from BM cavities. Thus, lack of osteoclasts likely results in inhibition of HSC maintenance and HSPC mobilization. However, we found that osteoclasts are dispensable for hematopoietic stem cell maintenance and mobilization by using three independent osteoclast-less animal models. In this review, I will discuss the roles of osteoclasts in hematopoietic stem cell maintenance and mobilization.

Keywords: Osteoclasts, Hematopoietic stem and progenitor cell, Mobilization, Receptor activator of nuclear factor kappa B ligand, Osteomac, Osteopetrosis, op/op, C-Fos, Osteoprotegerin