Background

Hyaluronan is a large, nonsulfated glycosaminoglycan that is a major component of many extracellular matrices. Secretion of hyaluronan has been associated with inflammation in the lungs and other tissues. The purpose of the present study was to determine the distribution of hyaluronan in human respiratory tissues and to determine if hyaluronan was present in human nasal secretions.

Method

Hyaluronan was localized in histological sections of human nasal and tracheobronchial mucosa using a biotinlabeled affinity-purified hyaluronan binding probe derived from cartilage proteoglycan (b-PG)(Green et al. Exp Cell Res 1988; 178: 224-32). Subjects had saline nasal provocation to collect baseline nasal secretions, then ate chili peppers to provoke parasympathetic cholinergic nasal glandular secretion (gustatory provocation). Total protein and hyaluronan concentrations were measured in the lavage fluids.

Results

Staining for hyaluronan was intense in basement membranes of epithelium, glands and vessels, and perivascular adventitia. Many epithelial cells contained hyaluronan, but the staining intensity was less than that on the basolateral aspects of these cells. Submucosal gland serous cells contained variable amounts of hyaluronan. Hyaluronan was not present in goblet cells, submucosal gland mucous cells, or sub-basement membrane collagen deposits. The gustatory, parasympathetic stimulus induced a 4-fold increase in hyaluronan secretion (P< 0.01) and a 3.5-fold increase in total protein release (P< 0.0010). Hyaluronan accounted for 75% to 80% of the polymeric uronic acids in human nasal secretions.

Conclusion

Hyaluronan was present human respiratory epithelial cells and submucosal gland serous cells and was exocytosed in response to parasympathetic stimulation. This distribution suggests roles in packaging cationic proteins in serous cells, cellular adhesion to basement membranes, and activation of macrophages in airway lumens.