Abstract
Mesenchymal stromal cell (MSC) implantation is a promising option for liver repair, but their poor retention in the injured liver milieu critically blunts therapeutic effects. The aim is to clarify the mechanisms underlying massive MSC loss post-implantation and establish corresponding improvement strategies. MSC loss primarily occurs within the initial hours after implantation into the injured liver milieu or under reactive oxygen species (ROS) stress. Surprisingly, ferroptosis is identified as the culprit for rapid depletion. In ferroptosis- or ROS-provoking MSCs, branched-chain amino acid transaminase-1 (BCAT1) is dramatically decreased, and its downregulation renders MSC susceptible to ferroptosis via suppressing the transcription of glutathione peroxidase-4 (GPX4), a vital ferroptosis defensing enzyme. BCAT1 downregulation impedes GPX4 transcription via a rapid-responsive metabolism-epigenetics coordinating mechanism, involving α-ketoglutarate accumulation, histone 3 lysine 9 trimethylation loss, and early growth response protein-1 upregulation. Approaches to suppress ferroptosis (e.g., incorporating ferroptosis inhibitors in injection solvent and overexpressing BCAT1) significantly improve MSC retention and liver-protective effects post-implantation. This study provides the first evidence indicating that excessive MSC ferroptosis is the nonnegligible culprit for their rapid depletion and insufficient therapeutic efficacy after implantation into the injured liver milieu. Strategies suppressing MSC ferroptosis are conducive to optimizing MSC-based therapy.