Physical activity plays an important role against pathological degenerative conditions and metabolic diseases. In particular, it works as a modulator of the mutually exclusive osteogenic or adipogenic fates of mesenchymal stem cells through a direct action on differentiation-related gene expression. On the other hand, it has also been reported that oxidative stress generated by strenous physical efforts (e.g. marathon running) can affect cell functions. The purpose of this study was to investigate the effects induced by a half marathon in male amateur runners. In particular the investigation focused on: i) serum proteins modulation in response to the oxidative environment, ii) the modulation of circulating progenitor cells commitment, monitored in terms of gene expression; iii) progenitor cells proliferation and homeostasis, monitored through the expression levels of genes related to telomerase activity and autophagic induction, respectively; iv) the effects of soluble factors present in runners\u2019 sera on differentiation process in an in vitro cellular model. The shotgun proteomic approach applied to runners\u2019 sera confirmed the production of reactive oxygen species, counteracted by an increased production of detoxifying and scavenger proteins. Overall, the proteome modulation profile suggests a consequent positive effect of the trained condition. Gene expression analyses showed an upregulation of osteogenesis related genes in Circulating Progenitor cells (CPs) after training, in particular RUNX2 and BMPs. In addition, chondrogenesis related genes such as SOX9, COMP and COL2A1 were upregulated after the run. At the same time, the higher expression of BMP3 suggests a stimulation of CPs proliferation which justifies as well the increased expression of telomerase-related genes, TERT and TERF1. The enhanced expression of autophagyrelated genes (ATG3 and ULK1) correlates positively with the induction of MSCs differentition. Data based on an in vitro model (i.e. Bone Marrow-derived MSCs supplemented with pre- and post-run sera), suggest that intense physical exercise enhances BM-MSC potential for osteo-chondrogenic commitment at the expense of the mutually exclusive adipogenesis. The in vitro deposition of calcium salts demonstrates mineralization, i.e. complete maturation of osteoblasts promoted by soluble factors in runners\u2019 sera. In conclusion, changes induced by physical activity may be considered positive in terms of: i) oxidative stress management during oxigen reactive species production; ii) progenitor cells proliferation, under autophagy-mediated positive selection; iii) osteochondrogenic induction of CPs; iv) production of circulating soluble factors which support complete maturation of committed osteoblasts. All data seem to suggest that physical activity has positive effects on overall health
