Background: The oral cavity along with the teeth and the surrounding gingival epithelium is open to the oral environment and is thus exposed to multiple microbiological and pathogenic influences. To prevent permanent inflammatory processes such as gingivitis or parodontitis, an efficient defense system is necessary to sustain the physiological function of the oral cavity. Surfactant proteins (SPs), originally known from pulmonary tissue, are important players of the immune system and, beyond this, support the stability and rheology of gas or fluid interphases.
Methods: Here we evaluate the expression and presence of SPs (SP-A, SP-B, SP-C, and SP-D) in human gingiva and saliva. Messenger RNA expression of SP-A, SP-B, SP-C, and SP-D was analyzed by reverse transcriptase-polymerase chain reaction in healthy gingiva. The distribution of all four SPs was further determined with monoclonal antibodies using Western blot analyses and immunohistochemistry in healthy and pathologically changed tissues samples obtained during biopsies and in saliva of volunteers.
Results: Our results indicate that SP-A, SP-B, SP-C, and SP-D are peptides produced by healthy gingiva that reveal a changed expression pattern in cases of gingival disease.
Conclusion: Based on the known direct and indirect antimicrobial effects, SP-A and SP-D appear to be involved in immune defense within the oral cavity especially in direct proximity of teeth. Gingiva affected by bacterial inflammation (gingivitis) seems to increase expression of SPs. As a result, the rheology of saliva may be changed especially at the crest of the gingival epithelium to support the function of antimicrobial substances present in saliva. Furthermore, SPs could assist in pellicle formation on teeth, which needs to be determined in further experiments.