title: Mechanical strain inhibits adipogenesis in mesenchymal stem cells by stimulating a durable beta-catenin signal.
abstract: The ability of exercise to decrease fat mass and increase bone mass may occur through mechanical biasing of mesenchymal stem cells (MSCs) away from adipogenesis and toward osteoblastogenesis. C3H10T1/2 MSCs cultured in highly adipogenic medium express peroxisome proliferator-activated receptor gamma and adiponectin mRNA and protein, and accumulate intracellular lipid. Mechanical strain applied for 6 h daily inhibited expression of peroxisome proliferator-activated receptor gamma and adiponectin mRNA by up to 35 and 50%, respectively, after 5 d. A decrease in active and total beta-catenin levels during adipogenic differentiation was entirely prevented by daily application of mechanical strain; furthermore, strain induced beta-catenin nuclear translocation. Inhibition of glycogen synthase kinase-3beta by lithium chloride or SB415286 also prevented adipogenesis, suggesting that preservation of beta-catenin levels was important to strain inhibition of adipogenesis. Indeed, mechanical strain inactivated glycogen synthase kinase-3beta, which was preceded by Akt activation, indicating that strain transmits antiadipogenic signals through this pathway. Cells grown under adipogenic conditions showed no increase in osteogenic markers runt-related transcription factor (Runx) 2 and osterix (Osx); subsequent addition of bone morphogenetic protein 2 for 2 d increased Runx2 but not Osx expression in unstrained cultures. When cultures were strained for 5 d before bone morphogenetic protein 2 addition, Runx2 mRNA increased more than in unstrained cultures, and Osx expression more than doubled. As such, mechanical strain enhanced MSC potential to enter the osteoblast lineage despite exposure to adipogenic conditions. Our results indicate that MSC commitment to adipogenesis can be suppressed by mechanical signals, allowing other signals to promote osteoblastogenesis. These data suggest that positive effects of exercise on both fat and bone may occur during mesenchymal lineage selection.
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors.forename: Buer
authors.initials: B
authors.lastname: Sen
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Xie
authors.forename: Natasha
authors.initials: N
authors.lastname: Case
authors.forename: Meiyun
authors.initials: M
authors.lastname: Ma
authors.forename: Clinton
authors.initials: C
authors.lastname: Rubin
authors.forename: Janet
authors.initials: J
authors.lastname: Rubin
mesh_terms: D050156:Adipogenesis / Q000187:drug effects / Q000502:physiology*; D052242:Adiponectin / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism; D003470:Culture Media / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D015870:Gene Expression / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D018021:Lithium Chloride / Q000494:pharmacology; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D047495:PPAR gamma / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000076182:Sp7 Transcription Factor; D013314:Stress, Mechanical; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D052242:Adiponectin; D055396:Bone Morphogenetic Protein 2; D050659:Core Binding Factor Alpha 1 Subunit; D003470:Culture Media; D047495:PPAR gamma; C493716:Runx2 protein, mouse; D000076182:Sp7 Transcription Factor; C479466:Sp7 protein, mouse; D014157:Transcription Factors; D051176:beta Catenin; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3; D018021:Lithium Chloride