Purification of replicating pancreatic β-cells for gene expression studies

Induction of ß Cell Replication by Small Molecule-Mediated Menin Inhibition and Combined PKC Activation and TGF‑ß Inhibition as Revealed by A Refined Primary Culture Screening

OBJECTIVE

Pancreatic β cells are recognized as central players in the pathogenesis of types 1 and 2 diabetes. Efficient and robust primary culture methods are required to interrogate β cell biology and screen potential anti-diabetic therapeutics. The aim of this study was to refine monolayer culture of beta cells and to investigate potential inducers of beta cell proliferation.

MATERIALS AND METHODS

In this experimental study, we compared different culture methods to optimize conditions required for a monolayer culture of rat pancreatic islet cells in order to facilitate image analysis-based assays. We also used the refined culture method to screen a group of rationally selected candidate small molecules and their combinations to determine their potential proliferative effects on the β cells.

RESULTS

Ham's F10 medium supplemented with 2% foetal bovine serum (FBS) in the absence of any surface coating provided a superior monolayer β cell culture, while other conditions induced fibroblast-like cell growth or multilayer cell aggregation over two weeks. Evaluation of candidate small molecules showed that a menin inhibitor MI-2 and a combination of transforming growth factor-β (TGF-β) inhibitor SB481542 and protein kinase C (PKC) activator indolactam V (IndV) significantly induced replication of pancreatic β cells.

CONCLUSION

Overall, our optimized culture condition provided a convenient approach to study the cultured pancreatic islet cells and enabled us to detect the proliferative effect of menin inhibition and combined TGF-β inhibition and PKC activation, which could be considered as potential strategies for inducing β cell proliferation and regeneration.

Protocol for determining zinc-dependent β cell-selective small-molecule delivery in mouse pancreas

Targeted drug delivery to pancreatic islet β cells is an unmet clinical need. β cells possess a uniquely high Zn2+ concentration, and integrating Zn2+-binding activity into a small molecule can bias drug accumulation and activity toward β cells. This protocol can be used to evaluate a molecule's capacity to chelate islet Zn2+, accumulate in islets, and stimulate β cell-selective replication in mouse pancreas. One obstacle is establishing an LC-MS/MS-based method for compound measurement. Limitations include target compound ionizability and the time-sensitive nature of some experimental assay steps. For complete details on the use and execution of this protocol, please refer to Horton et al. (2019).

Determining Beta Cell Mass, Apoptosis, Proliferation, and Individual Beta Cell Size in Pancreatic Sections

Pancreatic beta cells have a significant remodeling capacity which plays an essential role in the maintenance of glucose homeostasis. Beta cell apoptosis, replication, size, dedifferentiation, and (neo)generation contribute to the beta cell mass regulation. However, the extent of their respective contribution varies significantly depending on the specific condition, and it is the balance among them that determines the eventual change in beta cell mass. Thus, the study of the pancreatic beta cell mass regulation requires the determination of all these factors. In this chapter, we describe the quantification of beta cell replication based on the incorporation of thymidine analogs into replicated DNA strands and on the expression of Ki67 antigen and phosphorylation of histone H3. Beta cell apoptosis is analyzed by the TUNEL technique, and beta cell mass and cross-sectional area of individual beta cells are determined by computerized image processing methods.