A multi-parametric high throughput assay for detecting beta-cell proliferation in dispersed primary islets

Identification of novel compounds to selectively induce pancreatic beta-cell proliferation has the potential to restore functional beta-cell mass and insulin secretory demand in type 2 diabetes. The rarity of islet cell clusters (comprising of only 1% of the total pancreas mass) makes such a discovery a challenge. To address this obstacle a high throughput, 384 well, plate-based multi-parametric imaging assay was developed to capture ex vivo primary islet proliferation, allowing positive identification of compounds that can selectively enhance islet beta-cell proliferation. The use of microscopy-based, high-content imaging technology enables acquisition of additional multi-parametric information such as proliferating populations in the islet beta and non beta-cells, insulin intensity, and cell counts, improving understanding of on and off target effects in primary tissue. The protocol requires access to a high-throughput microscopy platform for automated image acquisition of treated islet cells in assay plates. High content image analysis software is required to extract multiparametric cellular features and aid identification of therapeutically relevant small molecules and perturbants. Several putative beta-cell proliferative compounds have validated in this high throughput assay format, including the pleiotropic hormone prolactin [1] and the small molecule DYRK1A inhibitor harmine [2]. It is recommended to include one, or both, as positive controls to provide a reference for image analysis, give confidence in assay performance and capture potential assay variability during experimental runs. The protocol outlined specifically focuses on the multiparametric assessment of betacell proliferation in mouse and rat ex vivo islets and provides the methodology required for the collection of high quality cellular material. The high throughput, plate based assay can additionally be adapted to evaluate and quantify other disease relevant endpoints by high content microscopy and be applied to other downstream measurements. One of the caveats of a high-throughput, 384 microplate beta-cell proliferative assay is its limitations to facilitate human beta-cell proliferation detection, especially for weak activators. Adult human beta-cell proliferation is an extremely rare biological event and assessment experimentally can be donor dependent. In addition lower human islet beta-cell subpopulations require large numbers of cells for accurate rare event measurement.