Notch Signaling in Mesenchymal Stem Cells Harvested From Geriatric Mice

• DOI: 10.1097/bot.0000000000000064
• Publication Date: 2014-01-01T08:17:40Z
• Authors: Patricia L. Mutyaba; Nicole S. Belkin; Luke Lopas; Chancellor F. Gray; Derek Dopkin; Kurt D. Hankenson; Jaimo Ahn
• Keywords: Fracture Healing; Male; 0301 basic medicine; Calcium-Binding Proteins; Age Factors; Membrane Proteins; Cell Count; Cell Differentiation; Mesenchymal Stem Cells; Mice, Inbred C57BL; Mice; 03 medical and health sciences; Animals; Intercellular Signaling Peptides and Proteins; Serrate-Jagged Proteins; Receptor, Notch2; Bony Callus; Jagged-1 Protein; Cell Proliferation; Signal Transduction

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.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.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.These data suggest that therapeutic targeting of Notch signaling should be explored in clinical therapies to improve geriatric fracture healing.