MDK promotes the mast cell activation and pancreatic fibrosis in mice with chronic pancreatitis via MDK-NCL signaling pathway.

Chronic pancreatitis (CP) is characterized by persistent inflammation and fibrosis in the pancreas, but its exact pathogenesis remains unclear. To investigate the underlying mechanisms, human CP single-cell RNA sequencing (scRNA-seq) data (GSE208536) were analyzed for clustering and cell communication, while a dibutyltin dichloride (DBTC)-induced CP mouse model was established. Flow cytometry was used to analyze cell phenotypes and sort cells. Bioinformatics analysis revealed that pancreatic stellate cells (PSCs) and mast cells play a pivotal role in CP progression, with a significant enrichment in the midkine (MDK)-nucleolin (NCL) ligand-receptor pair. In CP mice, we confirmed concurrent upregulation of fibrotic markers (α-SMA, Collagen I, FN1) and mast cell mediators (HIS, MCT, NGF, C-kit, IL-18), alongside elevated MDK/NCL expression and infiltration of both PSCs and mast cells. Functional validation showed that MDK knockdown in PSCs reduced activation and fibrosis, and suppressed proliferation and degranulation in mast cells. These effects were reversed by recombinant MDK. Additionally, NCL neutralization blocked mast cell activation in wild-type co-cultures. Crucially, in vivo knockdown of MDK or NCL reduced cell infiltration and activation, thus alleviating pancreatic damage and fibrosis. In conclusion, the MDK-NCL axis contributes to interactions between PSCs and mast cells, thereby exacerbating fibrosis and inflammation in CP. These findings provide a mechanistic insight into CP pathogenesis and identify the MDK-NCL axis as a candidate for future functional studies.