Up-regulation of surfactant protein A in chronic sialadenitis.

OBJECTIVES Salivary secretions play a critical role in maintaining the health of the oral cavity, which is the first gate of entry to the airways and thus is exposed to a variety of environmental insults. Surfactant protein A (SP-A) is a member of the collectin family and plays an important role in first-line airway defense. The objectives of this study were to examine the expression of SP-A messenger RNA and protein in human salivary glands and to investigate its up-regulation during inflammatory conditions. DESIGN Reverse transcription-polymerase chain reaction was performed on salivary gland tissues from patients and a control group. The expression levels of SP-A to GAPDH (glyceraldehyde-3-phosphate dehydrogenase) transcripts were semiquantified by densitometry. We also characterized the cellular localizations of SP-A protein immunohistochemically. SETTING Tertiary academic institution. PATIENTS Ten patients with chronic sialadenitis and 10 patients with healthy salivary glands. RESULTS Surfactant protein A messenger RNA and protein were detected in glands of patients who were healthy and in those with chronic sialadenitis. The expression levels of SP-A messenger RNA in the salivary glands of patients with chronic sialadenitis was significantly increased compared with those in healthy salivary glands. Immunohistochemical staining revealed SP-A immunoreactivity in the ductal epithelia of healthy salivary glands and in the salivary glands of those with chronic sialadenitis, and stronger immunoreactivity was observed in those with chronic sialadenitis tissues. CONCLUSIONS Surfactant protein A is present in the salivary gland epithelium and is up-regulated in individuals with chronic sialadenitis. These results suggest that salivary gland SP-A may play an important role in the innate host defense of human salivary glands.