PTPN2 deficiency amplifies inflammatory signalling and impairs functional maturation of human stem cell-derived islets

Abstract

Background Protein tyrosine phosphatases (PTPs) play key roles in β-cell function and diabetes development. PTPN2 is a candidate gene for type 1 diabetes (T1D) that negatively regulates JAK/STAT signalling. However, the impact of PTPN2 deficiency on the differentiation and functionality of human stem cell-derived somatic metabolic cells remains unclear. Methods PTPN2 expression in β cells from T1D organ donors and during the differentiation of human stem cell-derived islets (SC-islets) was evaluated using single-cell RNA-Sequencing (scRNA-Seq) datasets. We differentiated CRISPR-Cas12a genome-edited PTPN2-deficient H1 human embryonic stem cells (H1-hESCs) into SC-islets, and scRNA-Seq was performed. The maturation and functionality of PTPN2-deficient SC-islets were assessed by implantation under the kidney capsule of NOD-SCID mice. Results scRNA-Seq analysis showed that PTPN2 expression was increased in β cells from recently diagnosed T1D and decreased in long-standing T1D organ donors compared with controls. Conversely, we found that PTPN2 expression was decreased at the early stages of SC-islet differentiation and reconstituted at the later stages, suggesting a developmental dynamic. PTPN2 deficiency exacerbated interferon-induced inflammatory signalling in stem cells and differentiated somatic metabolic cells. Interestingly, PTPN2 deficiency increased hedgehog signalling and reduced SC-islet differentiation efficiency in vitro. In addition, PTPN2-knockout SC-islets exhibited reduced glycaemic control after implantation in vivo, mediated by reduced endocrine cell identity and enhanced interferon signalling. Conclusions Our study postulates a key role of PTPN2 in preserving β-cell function during inflammatory and metabolic stress in SC-islets.

1. Introduction

Inflammation-mediated pancreatic β-cell destruction is a hallmark of type 1 diabetes (T1D), resulting in diminished β-cell mass and insulin production [1–3]. During insulitis, type I and type II interferons activate the JAK/STAT signalling pathway in β cells via a cascade of tyrosine phosphorylation, exacerbating cytokine production, immune cell infiltration in the pancreas, and β-cell dysfunction [4]. Baricitinib is a pharmacological inhibitor of JAK proteins 1 and 2 used to treat rheumatoid arthritis. Repurposing the drug in a phase 2 clinical trial with recently diagnosed T1D patients showed that baricitinib improved human C-peptide levels during mixed meal insulin secretion [5]. This indicates that the pharmacological inhibition of JAK/STAT signalling preserves β-cell function in patients with T1D.

The superfamily of protein tyrosine phosphatases (PTPs) regulates tyrosine phosphorylation implicated in several pathways, including JAK/STAT signalling. Classical PTPs share highly similar catalytic mechanisms conserved in receptor- and non-receptor-types [6]. PTPN2 and PTPN22 are non-receptor PTPs and known risk genes for T1D [7, 8]. Lack of PTPN2 function caused by single-nucleotide polymorphisms (SNPs) rs2542151 and rs1893217 results in a higher risk of developing T1D and earlier disease development [9]. Complete depletion of PTPN2 in mice results in severe autoimmunity and premature lethality [10]. Furthermore, specific PTPN2 deletion in T cells of non-obese diabetic (NOD) mice causes earlier insulitis and increased diabetes incidence [11], suggesting the importance of PTPN2 in autoimmune diabetes.

We and others previously demonstrated that PTPN2 decreases JAK/STAT signalling in human and rodent β cells [12–15]. PTPN2 deficiency enhances calcium-dependent ER stress response in human β cells [12]. Recent studies have shown that PTPN2 deficiency reduces mitochondrial respiration, and the expression of genes involved in insulin secretion in cytokine-treated murine islets [16]. These results indicate that PTPN2 regulates key pathways involved in β-cell function under inflammatory and ER stress. Here, we show that PTPN2 deficiency amplifies inflammatory signalling and impairs functional maturation of human stem cell-derived islets.