Adipose tissue‑derived stem cells (ASCs) are beneficial for myocardial regeneration. The physiological oxygen content of human organs is estimated to range between 1 and 11%. However, in the majority of previous in vitro studies with cultured ASCs, the O2 concentration was artificially set to 21%. The present study aimed to compare the protective effects of rat ASCs on neonatal rat ventricular myocytes (NRVMs) under normoxic (21% O2) and physioxic (5% O2) conditions. Rat NRVMs cultured under

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... moxia or physioxia were treated with H2O2 or left untreated, and further co‑cultured with ASCs in 21% or 5% O2. The apoptosis of NRVMs was evaluated by Annexin V staining and quantitating the protein levels of Bcl‑2 and Bax by western blotting. The oxidative stress of NRVMs was determined by a glutathione/oxidized glutathione assay kit. The concentrations of secreted vascular endothelium growth factor (VEGF), insulin like growth factor‑1 (IGF‑1) and basic fibroblast growth factor (bFGF) in the culture medium were quantified by enzyme‑linked immunosorbent assay. Under both normoxia and physioxia, co‑culture with ASCs protected H2O2‑exposed NRVMs from apoptosis and significantly alleviated the oxidative stress in NRVMs. The protective effects of ASCs were associated with increased secretion of VEGF, IGF‑1 and bFGF. ASCs cultured in 5% O2 exhibited certain cardioprotective effects against H2O2 stress. The results of the present study suggested that O2 concentrations influenced the cardioprotective effects of ASCs. VEGF, IGF‑1 and bFGF may serve a role in the myocardial regeneration mediated by transplanted ASCs.