title: Orchestrating osteogenic differentiation of mesenchymal stem cells--identification of placental growth factor as a mechanosensitive gene with a pro-osteogenic role.
abstract: Skeletogenesis is initiated during fetal development and persists through adult life as either a remodeling process in response to homeostatic regulation or as a regenerative process in response to physical injury. Mesenchymal stem cells (MSCs) play a crucial role providing progenitor cells from which osteoblasts, bone matrix forming cells are differentiated. The mechanical environment plays an important role in regulating stem cell differentiation into osteoblasts, however, the mechanisms by which MSCs respond to mechanical stimuli are yet to be fully elucidated. To increase understanding of MSC mechanotransuction and osteogenic differentiation, this study aimed to identify novel, mechanically augmented genes and pathways with pro-osteogenic functionality. Using collagen glycoaminoglycan scaffolds as mimics of native extracellular matrix, to create a 3D environment more representative of that found in bone, MSC-seeded constructs were mechanically stimulated in a flow-perfusion bioreactor. Global gene expression profiling techniques were used to identify potential candidates warranting further investigation. Of these, placental growth factor (PGF) was selected and expression levels were shown to strongly correlate to both the magnitude and duration of mechanical stimulation. We demonstrated that PGF gene expression was modulated through an actin polymerization-mediated mechanism. The functional role of PGF in modulating MSC osteogenic differentiation was interrogated, and we showed a concentration-dependent response whereby low concentrations exhibited the strongest pro-osteogenic effect. Furthermore, pre-osteoclast migration and differentiation, as well as endothelial cell tubule formation also maintained concentration-dependent responses to PGF, suggesting a potential role for PGF in bone resorption and angiogenesis, processes key to bone remodeling and fracture repair.
authors.affiliation: Tissue Engineering Research Group, Dept. of Anatomy, Royal College of Surgeons in Ireland (RCSI), Dublin, Ireland; Trinity Centre for Bioengineering, Trinity College Dublin (TCD), Dublin 2, Ireland; Advanced Materials and Bioengineering Research (AMBER) Centre, RCSI & TCD, Ireland.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: McCoy
authors.forename: Amro
authors.initials: A
authors.lastname: Widaa
authors.forename: Karen M
authors.initials: KM
authors.lastname: Watters
authors.forename: Maximilian
authors.initials: M
authors.lastname: Wuerstle
authors.forename: Ray L
authors.initials: RL
authors.lastname: Stallings
authors.forename: Garry P
authors.initials: GP
authors.lastname: Duffy
authors.forename: Fergal J
authors.initials: FJ
authors.lastname: O'Brien
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D048708:Cell Growth Processes / Q000502:physiology; D017102:Fracture Healing / Q000502:physiology; D015870:Gene Expression; D006801:Humans; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D010012:Osteogenesis / Q000235:genetics / Q000502:physiology*; D000072483:Placenta Growth Factor; D011257:Pregnancy Proteins / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: C000608036:PGF protein, human; C000608037:Pgf protein, mouse; C000608038:Pgf protein, rat; D011257:Pregnancy Proteins; D000072483:Placenta Growth Factor
keywords: Bioreactors; Cellular mechanotransduction; Fracture healing; Osteogenesis; Placental growth factor