The role of blood podoplanin in patients with viral myocarditis

Podoplanin (PDPN), a small mucin-like glycoprotein, was recently found to promote the generation of cardiac ectopic lymphoid follicles and anti-heart autoantibodies (AHA) in viral myocarditis (VMC) mice. Herein, we investigated the blood PDPN expression and its potential clinical value in VMC patients. Overall, 40 VMC patients were enrolled among 112 hospitalized patients with suspected myocarditis. Their serum PDPN levels were higher than those in controlled acute myocardial infarction (AMI) patients (n = 40) and healthy individuals (n = 30) (both p < 0.01) and positively correlated with CRP, IL-17, and IL-4 (all p < 0.01). Elevation of serum PDPN discriminated VMC from AMI (OR = 4.061, p < 0.01) and PDPN addition to the basic model (age, CRP, and peak cTNI) increased AUC values (from 0.822 to 0.933, p = 0.04). Additionally, the serum levels of PDPN ligand CCL21 were also increased and correlated with PDPN (R = 0.59, p < 0.01) in VMC patients, accompanied by AHA production. Moreover, the anti-MHC antibody was closely related to PDPN levels (R = 0.53, p < 0.01), and antiMHC-positive patients with VMC displayed higher percentages of CD4(+)IL-17A(+)PDPN(+)T cells and CD19(+)CCR7(+)B cells (both p < 0.05). Noticeably, VMC patients complicated by ventricular arrhythmias (27.50%) presented with AHA production and higher PDPN levels (p < 0.05). Finally, we screened out and verified that miR-182-5p directly targeted PDPN and negatively regulated its expression (all p < 0.01). These data suggested that blood PDPN might be a novel inflammation-associated biomarker for the early diagnosis of VMC and may contribute to AHA production by binding CCL-21 to recruit Th17 and B cells, which were regulated by miR-182-5p.