Islet cell death is central to the development of T1D, and is also a common feature of both islet transplantation and T2D. It is well established that islet death commences several years prior to the clinical onset of T1D. However, we lack tools to quantify islet death or lack thereof, especially during early stages of beta-cell death. The development of a biomarker signature to quantify islet cell loss would help in identifying children at risk of developing T1D and allow preventative treatments to minimise islet loss.
Non-coding RNAs (ncRNAs), including microRNAs, show incredible potential as biomarkers for beta-cell death. During beta-cell death, islet-specific ncRNAs are released into the extracellular milieu and can be detected in circulation. Unlike mRNAs, ncRNAs are stable in circulation; they are protected from nucleases by protein complexes and exosomes. ncRNAs also have a long half-life in serum and are highly resistant to freeze-thawing.
Next Generation Sequencing (NGS) studies on developing human pancreases have led to the identification of specific ncRNAs that are found to be expressed specifically within human pancreatic islets. We combined FISH and immunostaining to confirm the localisation of each miRNA in human islets. Plasma from a longitudinal study of children at risk of developing T1D, and their age / gender matched controls, have been used to confirm this signature via TaqMan-based qPCR. An ultra-high-throughput qPCR platform was selected (after careful analysis of reproducibility) to validate this signature in patient samples from several clinical studies, including longitudinal and cross-sectional intervention studies.
The RAPID (RNA-based Analysis for the Prediction of Islet Death) study promises to offer a validated assay for quantitative estimation of islet death in diabetes, thereby opening the possibility to use alternative therapies designed to protect the islet mass, delaying the onset of diabetes and, in turn, decrease diabetic complications later in life.