title: A selective EP4 receptor antagonist abrogates the stimulation of osteoblast recruitment from bone marrow stromal cells by prostaglandin E2 in vivo and in vitro.
abstract: Recent evidence indicates that systemic administration of PGE2 increases bone formation and bone mass via activation of the EP4 receptor. Previously, we demonstrated that osteoblastic recruitment from rat bone marrow stromal cells (BMSC) is a major mechanism for the anabolic effect of PGE2. In this study, we used a selective EP4 antagonist to test if the stimulation of osteoblast differentiation from rat BMSC in vitro and in vivo involves the EP4 receptor. In vitro, PGE2 (100 nM) increased nodule formation and alkaline phosphatase (ALP) activity in cultures of rat BMSC 1.5- to 2-fold. These effects were abolished by the EP4 antagonist at 10(-6) M but not 10(-9) M. Furthermore, PGE2 increased the number of surviving adherent BMSC by approximately 225% and the EP4 antagonist prevented this effect as well. The antagonist had no effect on basal levels of nodule formation and adherent cell number. In vivo, daily systemic administration of PGE2 at 6 mg/kg for 2 weeks increased cancellous bone area (by approximately 50%) and increased nodule formation (measured as mineralized area) in ex vivo stromal cultures by approximately 50%. Pre-administration of the EP4 antagonist at 10 mg/kg abrogated both the increase in bone mass as well as the increase in nodule formation. These data indicate that PGE2 stimulates osteoblastic commitment of BMSC via activation of the EP4 receptor.
authors.affiliation: Department of Oral Biology, Maurice and Gabriela Goldschleger School of Dental Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel.
authors.forename: D
authors.initials: D
authors.lastname: Shamir
authors.forename: S
authors.initials: S
authors.lastname: Keila
authors.forename: M
authors.initials: M
authors.lastname: Weinreb
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001853:Bone Marrow / Q000187:drug effects* / Q000378:metabolism; D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D015232:Dinoprostone / Q000008:administration & dosage / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D008297:Male; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018078:Receptors, Prostaglandin E / Q000037:antagonists & inhibitors* / Q000378:metabolism; D058309:Receptors, Prostaglandin E, EP4 Subtype; D017154:Stromal Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism
chemical_list: C545652:Ptger4 protein, rat; D018078:Receptors, Prostaglandin E; D058309:Receptors, Prostaglandin E, EP4 Subtype; D000469:Alkaline Phosphatase; D015232:Dinoprostone