title: Ghrelin regulates proliferation and differentiation of osteoblastic cells.
abstract: It has previously been reported that growth hormone secretagogues (GHS) may have a role in the regulation of bone metabolism in animals and humans. In this study we evaluated the effect of ghrelin, the endogenous ligand of GHS receptors, on the proliferation rate and on osteoblast activity in primary cultures of rat calvaria osteoblasts. In the same experiments, we compared the effects of ghrelin with those of hexarelin (HEXA) and EP-40737, two synthetic GHS with different characteristics. Both ghrelin and HEXA (10(-11)-10(-8) M) significantly stimulated osteoblast proliferation at low concentrations (10(-10) M). Surprisingly, EP-40737 demonstrated an antiproliferative effect at 10(-9)-10(-8) M, whereas lower concentrations had no effect on cell proliferation. Ghrelin and HEXA significantly increased alkaline phosphatase (ALP) and osteocalcin (OC) production. At variance with these peptides, EP-40737 did not significantly stimulate ALP and OC. The mRNA for GHS-R1a receptors and the corresponding protein were detected in calvarial osteoblasts by RT-PCR and Western blot respectively, indicating that ghrelin and GHS may bind and activate this specific receptor. We conclude that endogenous ghrelin and synthetic GHS modulate proliferation and differentiation of rat osteoblasts, probably by acting on their specific receptor.
authors.affiliation: Department of Biomedical Sciences and Biotechnology, University of Brescia, Brescia, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Maccarinelli
authors.forename: Valeria
authors.initials: V
authors.lastname: Sibilia
authors.forename: Antonio
authors.initials: A
authors.lastname: Torsello
authors.forename: Francesca
authors.initials: F
authors.lastname: Raimondo
authors.forename: Marina
authors.initials: M
authors.lastname: Pitto
authors.forename: Andrea
authors.initials: A
authors.lastname: Giustina
authors.forename: Carmela
authors.initials: C
authors.lastname: Netti
authors.forename: Daniela
authors.initials: D
authors.lastname: Cocchi
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D054439:Ghrelin; D009842:Oligopeptides / Q000494:pharmacology; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects; D015675:Osteocalcin / Q000378:metabolism; D036361:Peptide Hormones / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000235:genetics; D054440:Receptors, Ghrelin; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012886:Skull; D013268:Stimulation, Chemical
chemical_list: C459919:EP40737; D054439:Ghrelin; D009842:Oligopeptides; D036361:Peptide Hormones; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D054440:Receptors, Ghrelin; C086184:hexarelin; D015675:Osteocalcin; D000469:Alkaline Phosphatase