[Frontiers in Bioscience E4, 2302-2321, January 1, 2012]

Bone cells and the mechanisms of bone remodelling

Andrea Del Fattore1, Anna Teti2, Nadia Rucci2

1Unita di Medicina Rigenerativa, Ospedale Pediatrico Bambino Gesu, piazza Sant Onofrio 4, 00165 Rome, 2Department of Experimental Medicine, University of L Aquila, via Vetoio Coppito 2, 67100 L'Aquila, Italy

TABLE OF CONTENTS

1. Abstract
2. Introduction
2.1. The bone tissue
2.2. Bone as a central tissue: cross-talk with other organs
2.2.1. Bone and immune system
2.2.2. Bone and kidney
2.2.3. Bone and adipose tissue
2.2.4. Serotonin-mediated control of bone mass
2.2.5. Bone and glucose metabolism
2.2.6. Bone and male infertility
3. Cells of the bone tissue
3.1. Osteoblasts
3.1.1. Osteoblastogenesis
3.1.2. Osteoblast morphology
3.1.3. Osteoblast functions
3.2. Osteocytes
3.2.1. Osteocyte formation
3.2.2. Osteocyte morphology and markers
3.2.3. Osteocyte functions
3.3. Osteoclasts
3.3.1. Osteoclastogenesis
3.3.2. Osteoclast morphology
3.3.3. Osteoclast functions
4. Osteoblast-osteoclast cross-talk
4.1. How osteoblasts regulate osteoclasts
4.2. How osteoclasts regulate osteoblasts
4.3. Osteoblast-osteoclast bidirectional signalling
5. Bone remodelling
5.1. Physiology of bone remodelling
5.2. Deregulation of bone remodelling and related diseases
6. Summary and perspective
7. References

1. ABSTRACT

Bone is a peculiar connective tissue which functionally interacts with many other organs and tissues, including bone marrow, lymphoid tissue, kidney, adipose tissue, endocrine pancreas, brain and gonads. Bone functions are accomplished by three principal cell types: the osteoblasts, cells of mesenchymal origin having osteogenic functions, the osteoclasts, giant multinucleated cells arising from the monocyte-macrophage line and devoted to resorb bone, and the osteocytes, the latter arising from mature osteoblasts that, once deposited the bone matrix, remain trapped in it, becoming quiescent cells. Osteocytes are known for their role as mechanosensors, however, old and new evidence showed their active contribution to mineral homeostasis. Moreover, the cross-talk between bone cells is crucial, since a correct bone homeostasis relies on a right coupling between osteoblast and osteoclast functions. Any deregulation of this coupling is responsible for bone disease condition, which reflects on other organs with which bone interacts.