Acta Histochemica 122 (2020) 151612 Available online 25 August 2020 0065-1281/© 2020 Elsevier GmbH. All rights reserved. Transdifferentiation of both intra- and extra-islet cells into beta cells in nicotinamide treated neonatal diabetic rats: An in situ hybridization and double immunohistochemical study Fatma Kaya-Dagistanli 1, *, Melek Ozturk 1 Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Medical Biology, 34098, Istanbul, Turkey A R T I C L E INFO Keywords: Nicotinamide β-cell regeneration Centroacinar cell Notch1 In situ hybridization Apoptosis ABSTRACT We aimed to study the effect of nicotinamide (NA) on beta (β)-cell regeneration and apoptosis in streptozotocin induced neonatal rats (n-STZ). Three groups were performed: Control group, n2-STZ group (100 mg/kg STZ on the second day-after birth), n2-STZ + NA group (STZ;100 mg/kg + NA;500 mg/kg/day for 5 days). The pancreatic tissue sections were immunostained with insulin, glucagon, somatostatin, Pdx1, Notch1 and active caspase-3 antibodies, and double immunostained with insulin/PCNA, insulin/glucagon and insulin/somatostatin antibodies. In situ hybridization carried out with insulin probe. Apoptotic β-cell were shown by TUNEL assay, followed by immunostaining. The number of insulin/PCNA, insulin/glucagon and insulin/somatostatin double- positive cells signifcantly increased in n2-STZ + NA group compared with the other groups (p < 0.001). n2- STZ group had lower number of insulin and Pdx1 positive cells in islets, compared to NA treated diabetics. The insulin and Pdx1 immun positive cells were located in the small clusters or scattered through the exocrine tissue and around to ducts in n2-STZ + NA group. Notch1 positive cell numbers were increased, whereas caspase-3 and TUNEL positive β-cell numbers were decreased in n2-STZ + NA group. NA treatment induces the neogenic insulin positive islets orginated from the differentiation of ductal progenitor cells, transdifferentiation of acinar cells into β cells, and transformation of potent precursor cells and centroacinar cells via the activated Notch expression into β-cells in n-STZ rats. 1. Introduction DiabetesMellitusis a chronic metabolic disease characterized by loss of pancreatic β-cell, impaired insulin secretion and hyperglycemia. β-cell regeneration and stimulatory mechanisms of new β-cell formation have importance in the treatment of β-cell deffciency in diabetes (Bouwens and Rooman, 2005; Desgraz et al., 2011). Understanding the molecular mechanisms of islet cells regeneration may contribute to improve the therapies for Diabetes Mellitus (Waguri et al., 1997; Li et al., 2004; Argun- Kurum et al., 2019). Pancreatic and duodenal homeobox factor-1 (Pdx1) plays a crucial role in pancreas formation in embryonic development as well as necessary for β-cell maturation. Pdx1 expression is limited to β-cells (Guz et al., 1995; Fernandes et al., 1997; Kaya-Dagistanli and Ozturk, 2013; Argun- Kurum et al., 2019), and in a very limited number of delta cells in adult pancreas (Guz et al., 1995; Fernandes et al., 1997). Pdx1 plays a role in the regulation of insulin, glucokinase, islet amyloid polypeptide, and glucose transporter type2 (GLUT2) in mature β-cells. It also involves in regulating β-cell mass, during the transdifferentiation of non-β-cell to gain the insulin-producing phenotypes following a pancreatic injury (Kim and Lee, 2016). The Notch genes are expressed in a variety of tissues in both the embryonic and adult organism, suggesting that the genes are involved in multiple signaling pathways. Notch signaling plays key roles in regu- lating proliferation, differentiation and apoptosis of cells (Yuan et al., 2015). Notch receptors belong to a transmembrane heterodimeric re- ceptor family with four distinct members (Notch1–4). Several research Abbreviations: β cell, Beta cell; CACs, Centroacinar cells; GLUT2, Glucose transporter type 2; TUNEL, In situ DNA end labeling method; NA, Nicotinamide; NAD + , Nicotinamide adenine dinucleotide; Pdx1, Pancreatic and duodenal homeobox factor-1; PARP, Poly (ADP-ribose) polymerase; STZ, Streptozotocin; n-STZ, Strep- tozotocin induced neonatal rats. * Corresponding author. E-mail addresses: fkaya@istanbul.edu.tr (F. Kaya-Dagistanli), mozturk@istanbul.edu.tr (M. Ozturk). 1 Fatma Kaya-Dagistanli and Melek Ozturk have equally contributed to this study Contents lists available at ScienceDirect Acta Histochemica journal homepage: www.elsevier.com/locate/acthis https://doi.org/10.1016/j.acthis.2020.151612 Received 10 May 2020; Received in revised form 6 August 2020; Accepted 6 August 2020