Session: 701. Experimental Transplantation: Basic Biology, Pre-Clinical Models
Hematology Disease Topics & Pathways:
apoptosis, Biological, Therapies, cellular interactions, Biological Processes, hematopoiesis, transplantation, immune mechanism, molecular interactions, senescence, signal transduction
Consistent with this hypothesis, our preliminary data shows increased levels of cl-caspase 1 (pyroptotic caspase) and a decrease in cl-caspase 3 (apoptotic caspase) in DPs after SL-TBI (550 cGy), demonstrating a preferential induction of pyroptotic cell death in DPs after damage (Fig. 1B). Furthermore, we demonstrated an increase in extracellular lactate dehydrogenase (LDH) levels, HMGB-1 and TNF⍺[canonical damage-associated molecular patterns (DAMPs) released during ICD] acutely after damage caused by SL-TBI (Fig. 1C).Given our previous findings that stromal cells are more radio-resistant than DP thymocytes (Wertheimer 2018 Sci Immunol3:19), and evidence for mitochondrial-induced pyroptosis, we identified hyperpolarization of the mitochondrial membrane potential accompanied by increased levels of ROS in DPs, an effect not observed in TECs, suggesting metabolic stability confers protection against acute damage (Fig. 1D). Furthermore, co-culture of pyroptotic thymocytes results in increased IL12p40+ DCs and increased Foxn1 expression in TECs (Fig. 1E), strengthening our hypothesis that cell-cell communication drives thymic regeneration after damage by inducing regenerative factors as well as directly promoting TEC function via secreted factors from pyroptotic DPs. One way in which DAMPs, such as ATP, can initiate cell signaling is by the activation of cell surface purinergic receptors, including P2Y2 which is widely expressed on TECs, and here we demonstrate that in vitro treatment with ATP or P2Y2 agonist increases Foxn1 in cTECs, and P2Y2 antagonism reverses this effect (Fig 1F). As P2Y2 activation promotes Ca2+efflux from the ER, we have further demonstrated that stimulating the intracellular release of Ca2+, using tunicamycin, induced Foxn1 expression in cTECs, which was reversed upon inhibition of Ca2+release (Fig. 1G). Importantly, we demonstrate here that this pathway can be therapeutically targeted by activating P2Y2 signaling in vivo with MRS2568 or ATP enhances thymus cellularity and expands cTECs in models of acute injury (Fig. 1H&I).
These findings not only reveal a novel metabolic-mediated molecular mechanism governing tissue regeneration; but also by targeting FOXN1 directly offers a potentially superior therapeutic strategy for boosting thymic regeneration and T cell reconstitution after damage such as that caused by HCT, infection or cytoreductive therapy.
Disclosures: No relevant conflicts of interest to declare.
See more of: Oral and Poster Abstracts