Characterisation of Ppy-lineage cells clarifies the functional heterogeneity of pancreatic beta cells in mice

Abstract

Aims/hypothesis Pancreatic polypeptide (PP) cells, which secrete PP (encoded by the Ppy gene), are a minor population of pancreatic endocrine cells. Although it has been reported that the loss of beta cell identity might be associated with beta-to-PP cell-fate conversion, at present, little is known regarding the characteristics of Ppy-lineage cells. Methods We used Ppy-Cre driver mice and a PP-specific monoclonal antibody to investigate the association between Ppy-lineage cells and beta cells. The molecular profiles of endocrine cells were investigated by single-cell transcriptome analysis and the glucose responsiveness of beta cells was assessed by Ca2+ imaging. Diabetic conditions were experimentally induced in mice by either streptozotocin or diphtheria toxin. Results Ppy-lineage cells were found to contribute to the four major types of endocrine cells, including beta cells. Ppy-lineage beta cells are a minor subpopulation, accounting for 12–15% of total beta cells, and are mostly (81.2%) localised at the islet periphery. Unbiased single-cell analysis with a Ppy-lineage tracer demonstrated that beta cells are composed of seven clusters, which are categorised into two groups (i.e. Ppy-lineage and non-Ppy-lineage beta cells). These subpopulations of beta cells demonstrated distinct characteristics regarding their functionality and gene expression profiles. Ppy-lineage beta cells had a reduced glucose-stimulated Ca2+ signalling response and were increased in number in experimental diabetes models. Conclusions/interpretation Our results indicate that an unexpected degree of beta cell heterogeneity is defined by Ppy gene activation, providing valuable insight into the homeostatic regulation of pancreatic islets and future therapeutic strategies against diabetes. Data availability The single-cell RNA sequence (scRNA-seq) analysis datasets generated in this study have been deposited in the Gene Expression Omnibus (GEO) under the accession number GSE166164 (www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE166164). Graphical abstract

Pancreatic polypeptide revisited: Potential therapeutic effects in obesity-diabetes

“…Although PP was discovered some 45 years ago [47] and is known to be largely secreted from the endocrine pancreas, a putative role for the hormone in islet cell function has been largely overlooked. However, recent knowledge that PP can protect against beta-cell destruction [44], as well as exerting probable important beneficial effects on islet cell transdifferentiation [31] and beta-cell rest [44], should bring about a resurgence of interest in the anti-diabetic properties of PP compounds and Y4 receptor activation. Future advances in our understanding of PP biology, coupled with appropriate therapeutic application likely linked to the development of enzyme-resistant, long-acting bioactive PP analogues, may well lead to the generation new and effective therapeutic agents for obesity and diabetes.…”

“…Furthermore, the role of beta-cell dedifferentiation and alterations in islet cell lineage have recently emerged as significant events in the development and progression of T2DM [91]. In this regard, lineaging tracing of the Ppy gene, that encodes for PP, has uncovered important beta-cell heterogeneity that is dependent on Ppy gene activation [31]. Indeed, Ppy-positive cells have long been identified as essential for normal islet differentiation during development [35].…”

“…Indeed, Ppy-positive cells have long been identified as essential for normal islet differentiation during development [35]. Moreover, it is now suggested that in the initial stages of diabetes development, where total beta-cell mass remains unchanged, an increase in the transdifferentaition of Ppy-positive cells towards insulin-positive beta-cells is a likely protective mechanism to preserve islet structure and function [31]. In full agreement, it has also been revealed that up to 40% of Ppy-positive islet cells can be reprogrammed to produce secretable insulin [73], demonstrating important plasticity of these cells for beta-cell regeneration.…”

Therapeutic effects of acylated ghrelin-specific receptor GHS-R1a antagonist in islet transplantation

“…Recently, Fukaishi and colleagues elucidated that PP cells may get converted to β cells when β cells are impaired. They concluded that PP cells served as progenitors of β cells and contributed to the maintenance of homeostasis of pancreatic islets 26 . However, the correlation between PP and other endocrine cells has not been fully discussed.…”

Establishment of an enzyme-linked immunosorbent assay for mouse pancreatic polypeptide clarifies the regulatory mechanism of its secretion from pancreatic γ cells

“…Islets were isolated from Ppy-Clover-PEST heterozygote mice (Ppy Clover-PEST/+ ) as described above, dispersed them into single cells and cultured overnight. Calcium flow parameters of the isolated islet cells were measured by Fura-2-acetoxymethyl (Fura 2-AM; Dojindo Molecular Technologies), and sodium flow parameters were measured by sodium-binding benzofuran isophthalate-acetoxymethyl (SBFI-AM; Thermo Fisher Scientific), as previously described [31][32][33]. To identify γ cells, green-fluorescent cells were specifically selected under the PLOS ONE fluorescence microscope.…”