NP is characterized by pseudocysts derived from stromal tissue edema and cause persistent infections in CRS patients. However, the mechanism regulating PLAT gene expression levels is still unclear. The epigenetic mechanism regulating the PLAT gene expression has been studied in other tissues.

We aimed to investigate the methylation levels in the proximal PLAT promoter and their effects on NP tissue gene expression.

We investigated the methylation levels at 3 CpG sites in the proximal PLAT promoter regions by bisulfite pyrosequencing and their effects on the gene expression by quantitative real-time polymerase chain reaction (qPCR) in 20 paired samples of NP and IT from patients with CRS.

The DNA methylation levels at all CpG sites were higher, and the PLAT expression was lower in NP than IT. The methylation changes at the −618 site negatively correlated with the gene expression change between NP and IT.

The PLAT promoter’s hypermethylation may downregulate the NP’s gene expression, leading to excessive fibrin deposition by aberrant coagulation cascade. DNA methylation of the proximal PLAT promoter may contribute to NP growth and e potential as a new therapeutic target.