title: cAMP/PKA signaling inhibits osteogenic differentiation and bone formation in rodent models.
abstract: We previously demonstrated that cAMP-mediated protein kinase A (PKA) activation induces in vitro osteogenesis and in vivo bone formation by human mesenchymal stem cells (hMSCs). To analyze the species-specific response of this phenomenon and to translate our findings into a clinical trial, suitable animal models and cell lines are desirable. In this report, we assessed whether PKA plays a similar proosteogenic role played by two commonly used PKA activators-N6,2'-O-dibutyryl-cAMP (db-cAMP) and 8-bromo cAMP (8b-cAMP)-in a number of model systems. To this end, we treated MC3T3-E1 cells, mouse calvarial osteoblasts, mouse MSCs, and rat MSCs with cAMP. We demonstrate that cAMP inhibits osteogenesis in rodent cell types, evidenced by inhibition of osteogenic markers such as alkaline phosphatase (ALP), osteocalcin (BGLAP), and collagen type 1 (COL1A1). In support of this, ex vivo-cultured mouse calvaria exposed to db-cAMP showed a reduction in bone volume. Interestingly, cAMP even stimulated adipogenic differentiation in rat MSCs. Taken together, our data demonstrate that cAMP inhibits osteogenesis in vitro and bone formation ex vivo in rodent models in contrast to our earlier findings in hMSCs. The species discrepancy in response to various osteogenic signals is a critical need to be tested in clinically relevant models to translate the fundamental findings in lower species level to clinical applications.
authors.affiliation: Department of Tissue Regeneration, Institute for BioMedical Technology, University of Twente, Enschede , The Netherlands.
authors.forename: Ramakrishnaiah
authors.initials: R
authors.lastname: Siddappa
authors.forename: Winfried
authors.initials: W
authors.lastname: Mulder
authors.forename: Ilse
authors.initials: I
authors.lastname: Steeghs
authors.forename: Christine
authors.initials: C
authors.lastname: van de Klundert
authors.forename: Hugo
authors.initials: H
authors.lastname: Fernandes
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Roel
authors.initials: R
authors.lastname: Arends
authors.forename: Clemens
authors.initials: C
authors.lastname: van Blitterswijk
authors.forename: Jan
authors.initials: J
authors.lastname: de Boer
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D050156:Adipogenesis / Q000187:drug effects; D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors; D000818:Animals; D001921:Brain / Q000166:cytology / Q000187:drug effects; D003994:Bucladesine / Q000494:pharmacology; D002113:Calcification, Physiologic / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D023421:Models, Animal; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D015124:8-Bromo Cyclic Adenosine Monophosphate; D003994:Bucladesine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000469:Alkaline Phosphatase