Cytokine priming of mesenchymal stromal cells enhances features of cellular senescence and function. Mus musculus strain:c57bl/6

Mesenchymal stromal cells (MSC) are increasingly being trialled in a variety of disorders, albeit with mixed effectiveness, which may reflect heterogeneity consequent on method of isolation and injudicious use of priming cytokines. A well-defined population of bone marrow MSC was isolated using the specific cell surface markers PDGFRalpha and Sca-1 (PalphaS), which was capable of robust culture expansion with a full repertoire of MSC actions including senescence and loss of function over time. To ascertain if these MSC properties could be favourably altered, the effect of single cytokine priming was studied. Whilst all factors (PDGF-BB, TGF-beta1 and FGF2) facilitated cell expansion, there were markedly different functional outcomes - FGF2-priming enhanced chondrogenesis and compromised immunomodulatory efficacy, whereas TGF-beta1 priming delayed cellular senescence (without adverse karyotypic changes) and prolonged immunomodulatory efficacy. Microarray and transcriptomic analyses identified gene and secretome signatures associated with cytokine-primed functionality with late passage TGF-beta1 primed cells showing increases in growth factors including IGFBP2 and osteoprotegenerin as well as greater secretion of immune regulatory cytokines including Il-2, Il-17 and Il-22. This provides insights into mechanism of action of MSC and optimal cytokine regimens for therapeutic application.