Identification of Oxidative Stress-Associated Macrophages in Acute Pancreatitis and Podoplanin as a Candidate Biomarker

Background/Objectives: Acute pancreatitis (AP) is a severe inflammatory disorder driven by complex immune responses and oxidative stress. While macrophages are central to AP pathogenesis, the subsets associated with oxidative stress remain poorly defined. This study aims to identify oxidative stress-associated macrophages and explore novel biomarkers for AP. Methods: We integrated time-resolved single-cell RNA sequencing (scRNA-seq) of a murine AP model with computational analyses, including pathway scoring and cell–cell communication inference. Findings were validated using LPS-stimulated bone marrow-derived macrophages (BMDMs), immunofluorescence of murine AP tissues, and peripheral blood mononuclear cells (PBMCs) from AP patients. Results: scRNA-seq analysis revealed a distinct oxidative stress-associated macrophage (OxMφ) subset that expanded significantly during early AP (12–36 h). Cell–cell communication analysis predicted prominent OxMφ-associated inflammatory and tissue-remodeling interactions. Transcriptomic intersection identified Podoplanin (PDPN) as a candidate marker associated with OxMφ. In vitro, LPS stimulation induced time-dependent PDPN expression in BMDMs, which strongly correlated with reactive oxygen species (ROS) and pro-inflammatory cytokine (TNF-α, IL-1β) production. In vivo, PDPN+ macrophages accumulated prominently in the injured murine pancreas. Clinically, PDPN mRNA was significantly upregulated in the PBMCs of AP patients and positively correlated with IL1B mRNA levels, white blood cell counts, and systemic inflammation. Conclusions: We identified an oxidative stress-associated macrophage state in murine AP and established PDPN as a candidate marker of this state, offering a potential cellular target for early immunomodulation.