title: Relaxin stimulates osteoclast differentiation and activation.
abstract: Relaxin is a pleiotropic hormone with actions in reproductive and non-reproductive tissues, and has a role in tumor biology. It can promote growth, differentiation and invasiveness of different tumors, especially those that give bone metastases, and relaxin serum concentrations are increased in patients with bone metastasis. In osteolytic metastasis the destruction of bone is mediated by osteoclasts that are multinucleated cells derived from hematopoietic progenitors. We found that human hematopoietic precursors and mature osteoclasts express the relaxin receptor RXFP1. Then, we investigated the effects of relaxin on the differentiation, activation and gene expression of osteoclasts during in vitro osteoclastogenesis from human hematopoietic progenitor cells. Relaxin alone was able to induce the multistep differentiation process of human osteoclastogenesis with timing similar to that obtained with the classical stimulators of osteoclastogenesis RANKL, M-CSF and PTH. The expression profile of several osteoclast genes was studied with quantitative RT-PCR during the entire process of osteoclastogenesis. This analysis showed that relaxin induced genes that are implicated in the differentiation, survival and activation of osteoclasts. Relaxin-induced osteoclasts were fully differentiated, positive for tartrate resistant acid phosphatase and vitronectin receptor, expressing a typical F-actin ring and able to resorb the bone. Furthermore, relaxin induced the expression of its specific receptor RXFP1 in osteoclasts. This study demonstrates for the first time that relaxin is a potent stimulator of osteoclastogenesis from hematopoietic precursors and regulates the activity of mature osteoclasts, opening new perspectives on the role of this hormone in bone physiology, diseases and metastasis.
authors.affiliation: Section of Clinical Pathology and Center for Male Gamete Cryopreservation, Department of Histology, Microbiology and Medical Biotechnologies, University of Padova, Via Gabelli 63, 35121 Padova, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Ferlin
authors.forename: Anastasia
authors.initials: A
authors.lastname: Pepe
authors.forename: Arianna
authors.initials: A
authors.lastname: Facciolli
authors.forename: Lisa
authors.initials: L
authors.lastname: Gianesello
authors.forename: Carlo
authors.initials: C
authors.lastname: Foresta
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015415:Biomarkers / Q000378:metabolism; D001862:Bone Resorption / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D020287:In Situ Nick-End Labeling; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009928:Organ Specificity / Q000187:drug effects / Q000235:genetics; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism; D018000:Receptors, Peptide / Q000235:genetics / Q000378:metabolism; D012065:Relaxin / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D015415:Biomarkers; C417543:RXFP1 protein, human; D043562:Receptors, G-Protein-Coupled; D018000:Receptors, Peptide; D012065:Relaxin