PARP1 and necrotizing enterocolitis: Upregulated PARP1 and PAR in the intestinal tissues were observed in NEC mice as revealed by immunofluorescent staining, whereas administration of 3-AB strongly attenuated NEC-enhanced PARP1 and PAR expression at the top and bottom of the intestinal villi, as identified by Lgr5 (p < 0.05, p < 0.01 versus NEC mice) (Fig. 4A–D).