Sestrin 2 (SESN2) is a member of the sestrin family of stress-induced proteins that negatively regulate agingassociated biological processes. This study aims to investigate the role of SESN2 in regulating the differentiation potential and senescence of mesenchymal stem cells (MSCs) derived from young and elderly donors. Bulk RNA sequencing revealed a common decline in the SESN2 mRNA levels in MSCs from elderly individuals, which was confirmed via reverse transcription-polymerase chain reaction and western blot analyses. SESN2 knockdown in MSCs from young donors resulted in phenotypic changes similar to those in MSCs from elderly donors, including an enhanced expression of senescence and adipogenic markers and diminished expression of osteogenic markers. To confirm the effect of decreased SESN2 expression on osteogenic and adipogenic differentiation, we induced Sesn2 knockdown in mouse bone marrow-derived MSCs. Sesn2 knockdown suppressed the mRNA expression of osteogenic marker genes, alkaline phosphatase activity, and matrix mineralization. Furthermore, Sesn2 knockdown enhanced mRNA expression of the adipogenic marker genes and intracellular lipid accumulation. These results suggest that a decline in SESN2 expression during aging contributes to the shift of MSC differentiation from osteogenic to adipogenic lineage.

Two piglets and one juvenile pig were used to investigate closely what types of cells express green fluorescent protein (GFP) and if any, whether the GFP-tagged cells could be used for stem cell transplantation research as a middle-sized animal model in bone marrow cells of recloned GFP pigs. Bone marrow cells were recovered from the tibia, and further analyzed with various cell lineage markers to determine which cell lineage is concurrently expressing visible GFP in each individual animal. In the three animals, visible GFP were observed only in proportions of the plated cells immediately after collection, showing 41, 2 and 91% of bone marrow cells in clones #1, 2 and 3, respectively. The intensity of the visible GFP expression was variable even in an individual clone depending on cell sizes and types. The overall intensities of GFP expression were also different among the individual clones from very weak, weak to strong. Upon culture for 14 days in vitro (14DIV), some cell types showed intensive GFP expression throughout the cells; in particular, in cytoskeletons and the nucleus, on the other hand. Others are shown to be diffused GFP expression patterns only in the cytoplasm. Finally, characterization of stem cell lineage markers was carried out only in the clone #3 who showed intensive GFP expression. SSEA-1, SSEA-3, CD34, nestin and GFAP were expressed in proportions of the GFP expressing cells, but not all of them, suggesting that GFP expression occur in various cell lineages. These results indicate that targeted insertion of GFP gene should be pursued as in mouse approach to be useful for stem cell research. Furthermore, cell- or tissue-specific promoter should also be used if GFP pig is going to be meaningful for a model for stem cell transplantation.