Interestingly, these molecular impediments can be overcome in physiological scenarios such as pregnancy in both rodents and humans (45,C48). is usually adult beta cells themselves; thus acquiring a working knowledge of the molecular mechanisms governing the proliferative behavior of adult beta cells and their progenitors is usually central to the success of all replacement strategies. However, as adult beta cells proliferate infrequently, and the precise molecular events involved in deriving mature beta cells from precursors is complex, generating an alternative adult source of human pancreatic beta cells for replacement strategies has not yet been achieved (16,C20). An additional impediment has been the lack of glucose-responsive human beta cell lines, limiting our understanding of the signaling mechanisms involved in beta cell proliferation in cell lines derived from rodent beta cell tumors (insulinomas) and animals (16). However, recent work has indicated that species differences in the cell cycle proteome may invalidate the use of rodents to understand human beta cell biology (21,C25). Taken together, there is now a critical need for approaches that elicit proliferative behavior of mature human beta cells and their progenitors and to establish a working understanding of the underlying mechanisms for precise intervention so as to avoid the risk of unrestricted growth. Here, we address these issues and describe the development and implementation of an HTS approach Rabbit polyclonal to ZNF483 Optovin using RNA interference to analyze proliferation following gene silencing in a mixed population of primary human pancreatic islet cells, and we report that the cell cycle-dependent kinase (CDK) inhibitors CDKN2C/p18 or CDKN1A/p21 are critical negative regulators of human beta cell proliferation. Experimental Procedures Antibodies/Reagents Antibodies for Western blotting were as follows: -actin (Sigma, 1:20,000); p53 (Santa Cruz Biotechnology, 1:1000); pRb (Pharmingen, 1:500) and p21 (Pharmingen 1:500); p27 (Cell Signaling, 1:500); PTEN (Santa Cruz Biotechnology, 1:200); pAKT (Cell Signaling, 1:1000) and AKT (Cell Signaling, 1:1000); LKB1 (Santa Cruz Biotechnology, 1:1000), p18 (Cell Signaling 1:200), and HSP90 (Santa Cruz Biotechnology, 1:1000). Antibodies for immunofluorescence were as follows: insulin (Dako, 1:1000), somatostatin (Dako, 1:1000), and glucagon (Dako, 1:1000). Click-it EdU imaging kit (Life Technologies, Inc.) was used according to the manufacturer’s recommendations. The following vectors were from Addgene: pLKO.1-TRC (catalog no. 10878) (26) and pHCMV-LCMV-WE (catalog no. 15793) (27). Islet Culture We used two sources of human pancreatic islets, the NIDDK (National Institutes of Health)-funded Integrated Islet Distribution Program (IIDP islets) at City of Hope and the J. Shapiro laboratory, University of Alberta, Edmonton, Canada (Edmonton islets). Male and female deceased donors were used, ranging in age from 16 to 79 years and body mass index from 20.1C35.7 kg/m2, none of which had a prior diagnosis of diabetes. The average purity of the Integrated Islet Distribution Program and Edmonton islets were 91.3 and 42.7%, viability of 94 and 80% respectively. When islet purity was under 85%, islets were picked manually and cultured for up to 30 days at 37 C in a 5% CO2 atmosphere in non-tissue culture-treated Petri dishes in PIM(S) media supplemented with 5% Optovin human AB serum, glutamine/glutathione mixture, and penicillin/streptomycin (all reagents from Prodo Laboratories Inc.). Medium was changed every 2C3 days. Islet Dissociation and Seeding Islets were washed in PBS and dissociated with Accutase (1 ml/1000 islets) for 20C30 min at 37 C, triturating every 5 min for 10 s. Dissociated islets were counted and seeded at a density of 15,000C20,000 cells/well in a 384-well plate for fluorescence or 60,000 cells/well in a 96-well plate to generate protein extracts. With the exception of the initial plate coating experiment, islets were always seeded on a PDL-coated plate (described below) to facilitate attachment of dissociated cells. Coated Plate Assay Six different matrices/surfaces were compared to determine the optimal surface to promote dissociated islet adherence. 384-Well plates were left untreated (tissue culture polystyrene) as a control surface. Matrigel (BD Biosciences), collagen type 1 (Sigma), applied cell Optovin extracellular matrix (Applied Biological Materials Inc.), and poly-d-lysine (Sigma) were coated onto the.