title: Pharmacological Inhibition of Protein Kinase G1 Enhances Bone Formation by Human Skeletal Stem Cells Through Activation of RhoA-Akt Signaling.
abstract: Development of novel approaches to enhance bone regeneration is needed for efficient treatment of bone defects. Protein kinases play a key role in regulation of intracellular signal transduction pathways, and pharmacological targeting of protein kinases has led to development of novel treatments for several malignant and nonmalignant conditions. We screened a library of kinase inhibitors to identify small molecules that enhance bone formation by human skeletal (stromal or mesenchymal) stem cells (hMSC). We identified H-8 (known to inhibit protein kinases A, C, and G) as a potent enhancer of ex vivo osteoblast (OB) differentiation of hMSC, in a stage- and cell type-specific manner, without affecting adipogenesis or osteoclastogenesis. Furthermore, we showed that systemic administration of H-8 enhances in vivo bone formation by hMSC, using a preclinical ectopic bone formation model in mice. Using functional screening of known H-8 targets, we demonstrated that inhibition of protein kinase G1 (PRKG1) and consequent activation of RhoA-Akt signaling is the main mechanism through which H-8 enhances osteogenesis. Our studies revealed PRKG1 as a novel negative regulator of OB differentiation and suggest that pharmacological inhibition of PRKG1 in hMSC implanted at the site of bone defect can enhance bone regeneration. Stem Cells 2015;33:2219-2231.
authors: Department of Endocrinology and Metabolism, Endocrine Research Laboratory (KMEB), Odense University Hospital & University of Southern Denmark, Odense, Denmark.|Danish Stem Cell Center (DanStem), Institute of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark.
authors: Abbas
authors: A
authors: Jafari
authors: Department of Endocrinology and Metabolism, Endocrine Research Laboratory (KMEB), Odense University Hospital & University of Southern Denmark, Odense, Denmark.|Danish Stem Cell Center (DanStem), Institute of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark.
authors: Majken S
authors: MS
authors: Siersbaek
authors: Department of Endocrinology and Metabolism, Endocrine Research Laboratory (KMEB), Odense University Hospital & University of Southern Denmark, Odense, Denmark.
authors: Li
authors: L
authors: Chen
authors: Department of Endocrinology and Metabolism, Endocrine Research Laboratory (KMEB), Odense University Hospital & University of Southern Denmark, Odense, Denmark.
authors: Diyako
authors: D
authors: Qanie
authors: Department of Endocrinology and Metabolism, Endocrine Research Laboratory (KMEB), Odense University Hospital & University of Southern Denmark, Odense, Denmark.
authors: Walid
authors: W
authors: Zaher
authors: Department of Endocrinology and Metabolism, Endocrine Research Laboratory (KMEB), Odense University Hospital & University of Southern Denmark, Odense, Denmark.
authors: Basem M
authors: BM
authors: Abdallah
authors: Department of Endocrinology and Metabolism, Endocrine Research Laboratory (KMEB), Odense University Hospital & University of Southern Denmark, Odense, Denmark.|Danish Stem Cell Center (DanStem), Institute of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark.
authors: Moustapha
authors: M
authors: Kassem
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000378:metabolism*; D002454:Cell Differentiation; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism* / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D020742:rhoA GTP-Binding Protein
keywords: Akt signaling; Bone formation; Human skeletal (mesenchymal) stem cells; Kinase inhibitor; Osteoblast differentiation