title: Notch signaling in mesenchymal stem cells harvested from geriatric mice.
abstract: OBJECTIVE
  Morbidity associated with geriatric fractures may be attributed, in part, to compromised mesenchymal stem cell (MSC) function within the fracture callus. The Notch signaling pathway is important for the healing of nonskeletal tissues in an age-dependent manner, but the effect of Notch on age-dependent fracture healing and MSC dysfunction has not been substantiated. The objective of this study was to examine Notch signaling in MSCs obtained from young and geriatric mice.
  
  
  METHODS
  Marrow-derived MSCs were harvested from the femora of 5- and 25-month-old C57BL/6 mice. We assessed in vivo MSC number using CFU-F, proliferation using an Alamar Blue assay, osteoblast differentiation by Alizarin Red S staining, and adipogenic differentiation using Oil Red O staining. Notch receptor and ligand expression was assessed using quantitative PCR, and Notch signaling was assessed by evaluating Notch target gene expression (Hey and HES) under basal conditions and when cells were plated to Jagged-1 ligand.
  
  
  RESULTS
  MSC from geriatric mice exhibit reduced MSC number (CFU-F), proliferation, adipogenesis, and inconsistent osteogenesis. The highest expressed Notch receptor is Notch 2, and the highest expressed ligand is Jagged-1, but there were no differences in ligand and receptor gene expression between young and old MSCs. Interestingly, geriatric MSCs show decreased basal Notch signaling activity but are fully responsive to Jagged-1 stimulation.
  
  
  CONCLUSIONS
  These data suggest that therapeutic targeting of Notch signaling should be explored in clinical therapies to improve geriatric fracture healing.
authors.affiliation: *Department of Orthopaedic Surgery, Perelman School of Medicine, and †Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA.
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Mutyaba
authors.forename: Nicole S
authors.initials: NS
authors.lastname: Belkin
authors.forename: Luke
authors.initials: L
authors.lastname: Lopas
authors.forename: Chancellor F
authors.initials: CF
authors.lastname: Gray
authors.forename: Derek
authors.initials: D
authors.lastname: Dopkin
authors.forename: Kurt D
authors.initials: KD
authors.lastname: Hankenson
authors.forename: Jaimo
authors.initials: J
authors.lastname: Ahn
mesh_terms: D000367:Age Factors; D000818:Animals; D002146:Bony Callus / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002452:Cell Count; D002454:Cell Differentiation; D049109:Cell Proliferation; D017102:Fracture Healing / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D000072100:Jagged-1 Protein; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D051883:Receptor, Notch2 / Q000096:biosynthesis*; D000072099:Serrate-Jagged Proteins; D015398:Signal Transduction
chemical_list: D002135:Calcium-Binding Proteins; D036341:Intercellular Signaling Peptides and Proteins; C000606274:Jag1 protein, mouse; D000072100:Jagged-1 Protein; D008565:Membrane Proteins; C497765:Notch2 protein, mouse; D051883:Receptor, Notch2; D000072099:Serrate-Jagged Proteins