title: Effect of deletion of the prostaglandin EP2 receptor on the anabolic response to prostaglandin E2 and a selective EP2 receptor agonist.
abstract: Studies using prostaglandin E receptor (EP) agonists indicate that prostaglandin (PG) E(2) can have anabolic effects through both EP4 and EP2 receptors. We previously found that the anabolic response to a selective EP4 receptor agonist (EP4A, Ono Pharmaceutical) was substantially greater than to a selective EP2 receptor agonist (EP2A) in cultured murine calvarial osteoblastic cells. To further define the role of the EP2 receptor in PG-mediated effects on bone cells, we examined the effects of EP2A and PGE(2) on both calvarial primary osteoblasts (POB) and marrow stromal cells (MSC) cultured from mice with deletion of one (Het) or both (KO) alleles of the EP2 receptor compared to their wild-type (WT) littermates. Deletion of EP2 receptor was confirmed by quantitative real-time PCR, Western blot and immunohistochemistry. The 1 month-old mice used to provide cells in these studies did not show any significant differences in their femurs by static histomorphometry. EP2A was found to enhance osteoblastic differentiation as measured by alkaline phosphatase mRNA expression and activity as well as osteocalcin mRNA expression and mineralization in the WT cell cultures from both marrow and calvariae. The effects were somewhat diminished in cultures from Het mice and abrogated in cultures from KO mice. PGE(2) effects were greater than those of EP2A, particularly in POB cultures and were only moderately diminished in Het and KO cell cultures. We conclude that activation of the EP2 receptor is able to enhance differentiation of osteoblasts, that EP2A is a true selective agonist for this receptor and that PGE(2) has an additional anabolic effect likely mediated by the EP4 receptor.
authors.affiliation: Musculoskeletal Institute, University of Connecticut Health Center, 263 Farmington Avenue, MC5456, CT 06030, United States.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Choudhary
authors.forename: Cynthia
authors.initials: C
authors.lastname: Alander
authors.forename: Peili
authors.initials: P
authors.lastname: Zhan
authors.forename: Qi
authors.initials: Q
authors.lastname: Gao
authors.forename: Carol
authors.initials: C
authors.lastname: Pilbeam
authors.forename: Lawrence
authors.initials: L
authors.lastname: Raisz
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D018078:Receptors, Prostaglandin E / Q000819:agonists / Q000235:genetics* / Q000502:physiology; D058307:Receptors, Prostaglandin E, EP2 Subtype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
chemical_list: C545645:Ptger2 protein, mouse; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; D015675:Osteocalcin; D000469:Alkaline Phosphatase; D015232:Dinoprostone