Immortalized mesenchymal stromal cells overexpressing alpha-1 antitrypsin protect acinar cells from apoptotic and ferroptotic cell death.

Chronic pancreatitis (CP) is a progressive inflammatory disorder that impairs endocrine and exocrine function. Our previous work showed that mesenchymal stem/stromal cells (MSCs) and MSCs overexpressing alpha-1 antitrypsin (AAT-MSCs) could be therapeutic tools for CP. However, primary MSCs are predisposed to undergo senescence during culture expansion, which limits their therapeutic applications. We generated and characterized immortalized human MSCs (iMSCs) and AAT-MSCs (iAAT-MSCs) and tested their protective effect on 2,4,6-Trinitrobenzenesulfonic acid (TNBS)-induced acinar cell death in an in vitro cell culture system. Primary MSCs were immortalized by transduction with simian virus 40 large T antigen (SV40LT), and the resulting iMSC and iAAT-MSC lines were analysed for proliferation, senescence, phenotype and multi-differentiation potential. Subsequently, apoptosis and ferroptosis pathways were investigated by assessing changes before and after TNBS treatment. Coculture of iMSCs and iAAT-MSCs with acinar cell lines inhibited early cell death induced by TNBS, reduced ER stress and reversed TNBS-induced protein reduction at tight junctions. Additionally, iMSCs and iAAT-MSCs exerted such protection by regulating mitochondrial respiration, ATP content and ROS production in TNBS-induced acinar cells. Furthermore, iMSCs and iAAT-MSCs ameliorated TNBS-induced ferroptosis by modulating iron generation and ROS production and regulating the ferritin heavy chain 1 (FTH1)/protein disulfide isomerase (PDI)/glutathione peroxide 4 (GPX4) signalling pathways in acinar cells. These findings identify ferroptosis as an unrecognized mechanism that leads to TNBS-induced cell death and offer mechanistic insights relevant to using stem cell therapy to treat acinar cell death associated with CP.