title: Reprint of: The Great Beauty of the osteoclast.
abstract: Much has been written recently on osteoclast biology, but this cell type still astonishes scientists with its multifaceted functions and unique properties. The last three decades have seen a change in thinking about the osteoclast, from a cell with a single function, which just destroys the tissue it belongs to, to an "orchestrator" implicated in the concerted regulation of bone turnover. Osteoclasts have unique morphological features, organelle distribution and plasma membrane domain organization. They require polarization to cause extracellular bone breakdown and release of the digested bone matrix products into the circulation. Osteoclasts contribute to the control of skeletal growth and renewal. Alongside other organs, including kidney, gut, thyroid and parathyroid glands, they also affect calcemia and phosphatemia. Osteoclasts are very sensitive to pro-inflammatory stimuli, and studies in the '00s ascertained their tight link with the immune system, bringing about the question why bone needs a cell regulated by the immune system to remove the extracellular matrix components. Recently, osteoclasts have been demonstrated to contribute to the hematopoietic stem cell niche, controlling local calcium concentration and regulating the turnover of factors essential for hematopoietic stem cell mobilization. Finally, osteoclasts are important regulators of osteoblast activity and angiogenesis, both by releasing factors stored in the bone matrix, and secreting "clastokines" that regulate the activity of neighboring cells. All these facets will be discussed in this review article, with the aim of underscoring The Great Beauty of the osteoclast.
authors.affiliation: Regenerative Medicine Unit, Bambino Gesù Children's Hospital, Istituto di Ricovero e Cura a Carattere Scientifico, Rome, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Cappariello
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Maurizi
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy; Anna University KB Chandrasekhar Research Centre (AU-KBC), Chennai, India.
authors.forename: Vimal
authors.initials: V
authors.lastname: Veeriah
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy. Electronic address: teti@univaq.it.
authors.forename: Anna
authors.initials: A
authors.lastname: Teti
mesh_terms: D000818:Animals; D001862:Bone Resorption / Q000473:pathology* / Q000503:physiopathology*; D001842:Bone and Bones / Q000473:pathology* / Q000503:physiopathology*; D002113:Calcification, Physiologic; D006801:Humans; D010010:Osteoclasts / Q000378:metabolism* / Q000473:pathology*
keywords: Angiogenesis; Bone formation; Bone resorption; Hematopoiesis; Immune system; Osteoclast