Mesenchymal stem cells (MSC) have attracted considerable attention in the fields of cell and gene therapy due to their intrinsic ability to differentiate into multiple lineages. The various therapeutic applications involving MSC require initial expansion and/or differentiation in vitro prior to clinical use. However, serial passages of MSC in culture lead to decreased differentiation potential and stem cell characteristics, eventually inducing cellular aging which will limit the success of cell-based therapeutic interventions. Here we review the age-related changes that occur in MSC with a special focus on the shift of differentiation potential from osteogenic to adipogenic lineage during the MSC aging processes and how aging causes this preferential shift by oxidative stress and/or energy metabolism defect. Oxidative stress-related signals and some microRNAs affect the differentiation potential shift of MSC by directly targeting key regulatory factors such as Runx-2 or PPAR-γ, and energy metabolism pathway is involved as well. All information described here including transcription factors, microRNAs and FoxOs could be used towards development of treatment regimens for age-related bone diseases and related defects based on mutually exclusive lineage fate determination of MSC.