title: Human mesenchymal stem cell proliferation is regulated by PGE2 through differential activation of cAMP-dependent protein kinase isoforms.
abstract: The conditions used for in vitro differentiation of hMSCs contain substances that affect the activity and expression of cyclooxygenase enzymes (COX1/COX2) and thereby the synthesis of prostanoids. hMSC constitutively produce PGE2 when cultivated in vitro. In this study we have investigated effects of PGE2 on proliferation of hMSC. We here demonstrate that one of the main control molecules in the Wnt pathway, GSK-3 beta, is phosphorylated at the negative regulatory site ser-9 after treating the cells with PGE2. This phosphorylation is mediated by elevation of cAMP and subsequent activation of PKA. Furthermore, PGE2 treatment leads to enhanced nuclear translocation of beta-catenin, thus influencing cell proliferation. The presence of two PKA isoforms, types I and II, prompted us to investigate their individual contribution in PGE2-mediated regulation of proliferation. Specific activation of PKA type II with synthetic cAMP analogues, resulted in enhancement of proliferation. On the other side, we found that treatment of hMSC with high concentrations of PGE2 inhibited cell proliferation by arresting the cells in G0/G1 phase, an effect we found to be mediated by PKA I. Hence, the two different PKA isoforms seem to have opposing functions in the regulation of proliferation and differentiation in these cells.
authors.affiliation: Institute of Immunology, Rikshospitalet-Radiumhospitalet Medical Center, Oslo, Norway. charlotte.kleiveland@umb.no <charlotte.kleiveland@umb.no>
authors.forename: Charlotte Ramstad
authors.initials: CR
authors.lastname: Kleiveland
authors.forename: Moustapha
authors.initials: M
authors.lastname: Kassem
authors.forename: Tor
authors.initials: T
authors.lastname: Lea
mesh_terms: D021581:Active Transport, Cell Nucleus; D002453:Cell Cycle; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D054743:Cyclic AMP-Dependent Protein Kinase Type I / Q000378:metabolism*; D054746:Cyclic AMP-Dependent Protein Kinase Type II / Q000378:metabolism*; D015232:Dinoprostone / Q000096:biosynthesis / Q000494:pharmacology / Q000502:physiology*; D004789:Enzyme Activation; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D051176:beta Catenin; D000242:Cyclic AMP; D000071679:Glycogen Synthase Kinase 3 beta; D054743:Cyclic AMP-Dependent Protein Kinase Type I; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D038362:Glycogen Synthase Kinase 3; D015232:Dinoprostone