# Integrated transcriptome profiling of plasma exosomes reveals molecular stratification of exocrine and endocrine disorders and S100A8-mediated cell interactions in chronic pancreatitis

## TL;DR

This study uses plasma exosome RNA to classify chronic pancreatitis severity and identifies key molecules involved in disease progression.

## Contribution

A novel 3-stage exosome-based classification system and the role of miR-24-3p and S100A8 in chronic pancreatitis progression are introduced.

## Key findings

- A 3-stage classification system based on 12 miRNAs in plasma exosomes predicts steatorrhea and diabetes in CP patients.
- Exosome-derived miR-24-3p and neutrophil S100A8 are pivotal in CP progression and fibrosis.
- Downregulated miR-24-3p leads to S100A8 upregulation, promoting pancreatic β-cell apoptosis and inflammation.

## Abstract

Exocrine and endocrine disorders and insufficiency are two major harmful pathological processes in chronic pancreatitis (CP) and can lead to steatorrhea and diabetes. However, there is a lack of reliable clinical classification schemes for evaluating the severity of exocrine and endocrine disorders in CP, and the underlying mechanisms are also unclear. In particular, exosome-based liquid biopsy and classification in CP are lacking. Here, we performed transcriptome sequencing on plasma exosomes from CP patients with different degrees of CP severity. Additionally, we analyzed single-cell sequencing data from pancreatic lesions in CP patients to interpret the classification, and an external cohort was established to verify the classification. Ultimately, we established and preliminarily verified a 3-stage classification system to predict steatorrhea and diabetes onset in CP patients based on the expression of 12 miRNAs in plasma exosomes. A publicly-available online tool implementing this classification system was also developed. Further analysis, in combination with single-cell sequencing data from CP mice, identified exosome-derived miR-24-3p and neutrophil S100A8 as pivotal factors in CP progression. Mechanistically, our findings suggest that downregulated exosome-derived miR-24-3p in CP may lead to the upregulation of its target gene, S100A8, in neutrophils, thus promoting CP-related exocrine and endocrine disorders by activating the fibrotic phenotype of pancreatic stellate cells and inducing inflammation in macrophages, leading to the apoptosis of pancreatic β cells. Together, our work provides a novel exosome-based 3-stage classification system for CP and highlights the role of exosomal miR-24-3p and S100A8 in fibrosis and pancreatic β-cell apoptosis.