title: Urokinase receptor mediates osteogenic differentiation of mesenchymal stem cells and vascular calcification via the complement C5a receptor.
abstract: Vascular calcification is a severe consequence of several pathological processes with a lack of effective therapy. Recent studies suggest that circulating and resident mesenchymal stem cells (MSC) contribute to the osteogenic program of vascular calcification. Molecular mechanisms underlying MSC osteogenic potential and differentiation remain, however, sparsely explored. We investigated a role for the complement receptor C5aR in these processes. We found that expression of C5aR was upregulated upon differentiation of human MSC to osteoblasts. C5aR inhibition by silencing and specific antagonist impaired osteogenic differentiation. We demonstrate that C5aR expression upon MSC differentiation was regulated by the multifunctional urokinase receptor (uPAR). uPAR targeting by siRNA resulted in complete abrogation of C5aR expression and consequently in the inhibition of MSC-osteoblast differentiation. We elucidated the NFκB pathway as the mechanism utilized by the uPAR-C5aR axis. MSC treatment with the NFκB inhibitor completely blocked the differentiation process. Nuclear translocation of the p65 RelA component of the NFκB complex was induced under osteogenic conditions and impaired by the inhibition of uPAR or C5aR. Dual-luciferase reporter assays demonstrated enhanced NFκB signaling upon MSC differentiation, whereas uPAR and C5aR downregulation lead to inhibition of the NFκB activity. We show involvement of the Erk1/2 kinase in this cascade. In vivo studies in a uPAR/LDLR double knockout mouse model of diet-induced atherosclerosis revealed impaired C5aR expression and calcification in aortic sinus plaques in uPAR(-/-)/LDLR(-/-) versus uPAR(+/+)/LDLR(-/-) control animals. These results suggest that uPAR-C5aR axis via the underlying NFκB transcriptional program controls osteogenic differentiation with functional impact on vascular calcification in vivo.
authors.affiliation: 1 Department of Nephrology and Hypertensiology, Hannover Medical School , Hannover, Germany .
authors.forename: Parnian
authors.initials: P
authors.lastname: Kalbasi Anaraki
authors.forename: Margret
authors.initials: M
authors.lastname: Patecki
authors.forename: Jan
authors.initials: J
authors.lastname: Larmann
authors.forename: Sergey
authors.initials: S
authors.lastname: Tkachuk
authors.forename: Kerstin
authors.initials: K
authors.lastname: Jurk
authors.forename: Hermann
authors.initials: H
authors.lastname: Haller
authors.forename: Gregor
authors.initials: G
authors.lastname: Theilmeier
authors.forename: Inna
authors.initials: I
authors.lastname: Dumler
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D006801:Humans; D020935:MAP Kinase Signaling System; D059630:Mesenchymal Stem Cells / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D010006:Osteoblasts / Q000378:metabolism; D010012:Osteogenesis; D044087:Receptor, Anaphylatoxin C5a / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator / Q000378:metabolism*; D061205:Vascular Calcification / Q000378:metabolism*
chemical_list: C488033:C5AR1 protein, human; D016328:NF-kappa B; D044087:Receptor, Anaphylatoxin C5a; D055293:Receptors, Urokinase Plasminogen Activator