Selective bacterial degradation of the extracellular matrix attaching the gingiva to the tooth

The junctional epithelium (JE) is a specialized portion of the gingiva that seals off

the tooth-supporting tissues from the oral environment. This relationship is

achieved via a unique adhesive extracellular matrix that is, in fact, a specialized

basal lamina (sBL). Three unique proteins – amelotin (AMTN), odontogenic

ameloblast-associated (ODAM), and secretory calcium-binding phosphoprotein

proline-glutamine rich 1 (SCPPPQ1) – together with laminin-332 structure the

supramolecular organization of this sBL and determine its adhesive capacity.

Despite the constant challenge of the JE by the oral microbiome, little is known of

the susceptibility of the sBL to bacterial degradation. Assays with trypsin-like proteases,

as well as incubation with Porphyromonas gingivalis, Prevotella intermedia,

and Treponema denticola, revealed that all constituents, except SCPPPQ1, were

rapidly degraded. Porphyromonas gingivalis was also shown to alter the supramolecular

network of reconstituted and native sBLs. These results provide evidence that

proteolytic enzymes and selected gram-negative periodontopathogenic bacteria can

attack this adhesive extracellular matrix, intimating that its degradation could contribute

to progression of periodontal diseases.