Cell penetrating caspase substrates promote survival of the transplanted cells

OBJECTIVE: Cell survival in critical post-transplantation period is challenged by inflammation, lack of vascularization, and insufficient cell attachment anchoring. Temporally blocking cell death may increase cell survival, but it is important to possess no risks of sustained cell death signal blocking and possible malignant transformations. Regarding apoptotic cell death, multi-micromolar overloading the cell with competitive caspase substrates delays the effects of actual downstream enzyme activation processing. Later, when introduced substrate is consumed, and the caspase activation stimuli may still be present, the apoptotic cell death can proceed normally. RESULTS: Here we studied several synthetic peptides comprising from effector caspase activational cleavage sequences fused with various internalization motifs. Designed peptides showed rapid and efficient internalization into cultured neuroblast cells comparing to non-fused cleavage sequences as measured by cytofluorimetry and confirmed by mass spectrometry. Pretreatment with selected peptides protected the cells from several apoptogenic stimuli in vitro, as well as improved survival of syngeneic immortalized Schwann cells during transplantation in vivo.