Prostaglandin D₂ (PGD₂) is released from mast cells during the allergic response. Since PGD₂ has been shown to induce nasal congestion in humans, we investigated the distribution of hematopoietic Prostaglandin D synthase (PGDS) and the two PGD₂ receptors, DP and CRTH2 in human nasal mucosa from healthy subjects and subjects suffering from polyposis, a severe form of chronic rhinosinusitis.

DP mRNA expression was detected by in situ hybridization while PGDS, CRTH2 and various leukocyte markers expression was revealed by immunohistochemistry.

In the normal mucosa, PGDS was only detected in few resident mast cells while CRTH2 was undetectable. In contrast, DP receptor mRNA was detected in epithelial goblet cells, serous glands and in the vasculature. In the nasal mucosa of subjects suffering from polyposis: 1) PGDS was detected in mast cells and other large infiltrating inflammatory cells, 2) both DP mRNA and CRTH2 were detected in eosinophils and 3) CRTH2 was detected on a subset of infiltrating T-cells. Although DP mRNA could not be detected in the T-cells invading the nasal mucosa, it was found to be expressed in the T-cells present in the lymph node and the thymus from normal individuals.

This study indicates that cells capable of producing PGD₂ are present in the nasal mucosa and that both PGD₂ receptors, DP and CRTH2, might play a role in inflammatory disease of the upper airways.