Glycosylation pattern and cell attachment-inhibiting property of human salivary mucins

Whole human saliva (WHS) and its high molecular weight mucin constituent (Muc) inhibit fibroblast attachment and might influence periodontal and peri-implant wound healing. The aim of this work was to study the potential role of glycosylation of Muc in fibroblast attachment-inhibiting property and to examine in vitro the effect of WHS and Muc on epithelial cell attachment.

Muc was isolated from WHS by CsCl density gradient ultracentrifugation; covalently immobilized on polystyrene; and subjected to enzymic digestion by N-glycanase, O-glycanase, and sialidase, or chemical desulfation and periodate treatment. Wells of tissue culture microtiter plates were incubated with WHS, Muc, or buffer as control; suspensions of normal human oral keratinocytes, spontaneously immortalized human keratinocytes, or human gingival fibroblasts were applied; and cell attachment determined using methylene blue assay.

While enzymic cleavage of N-linked carbohydrates showed no effect, selective removal of O-linked residues and sialic acid as well as desulfation and periodate oxidation resulted in statistically significant reduction of cell attachment-inhibiting property of immobilized Muc. Significantly lower numbers of attached cells of each cell type were found in wells pretreated with WHS or Muc.

Inhibition of cell attachment may be mediated by the carbohydrate residues suggesting specific interactions between the salivary constituent and the cell surface. Exposure of root and implant surfaces to saliva during early wound healing events might influence healing by inhibiting surface colonization by oral keratinocytes and fibroblasts, and enhancing wound repair in the form of long junctional epithelium rather than regeneration.