Abundance of MMPs and Cysteine Cathepsins in Caries-affected Dentin

Abstract

Degradation of dentin matrix components within caries dentin has been correlated with the activity of host-derived proteases, such as matrix metalloproteases (MMPs) and cysteine cathepsins (CTs). Since this relationship has not been fully established, we hypothesized that the abundance of MMPs and CTs in caries-affected dentin must be higher than in intact dentin. To test this premise, we obtained 5 slices (200 µm) from 5 intact teeth and from 5 caries-affected teeth (1 slice/tooth) and individually incubated them with primary antibodies for CT-B, CT-K, MMP-2, or MMP-9. Negative controls were incubated with pre-immune serum. Specimens were washed and re-incubated with the respective fluorescent secondary antibody. Collagen identification, attained by the autofluorescence capture technique, and protease localization were evaluated by multi-photon confocal microscopy. The images were analyzed with ZEN software, which also quantitatively measured the percentages of collagen and protease distribution in dentin compartments. The abundance of the test enzymes was markedly higher in caries-affected than in intact dentin. CT-B exhibited the highest percentage of co-localization with collagen, followed by MMP-9, MMP-2, and CT-K. The high expression of CTs and MMPs in caries-affected teeth indicates that those host-derived enzymes are intensely involved with caries progression.

Role of Dentin MMPs in Caries Progression and Bond Stability

“…However, true remineralization requires that nanometer-sized apatite crystals regrow in the gap zones of collagen fibrils, which has proven to be a difficult task (Bertassoni et al 2009). Recent evidence indicates that the dentin collagen matrix may not necessarily remain as intact as believed during caries demineralization (Suppa et al 2006;Tjäderhane et al 2013a;Vidal et al 2014). A significant reduction in immunohistological detection of intact type I collagen and proteoglycans (Suppa et al 2006) and almost complete loss of autofluorescent signal emitted by well-structured collagen Figure 3.…”

“…Also, cysteine cathepsins may participate in dentinal caries development. Cysteine cathepsin activity is different in the various compartments of the caries, depending on the localization and lesion activity (Nascimento et al 2011;Vidal et al 2014). The significant increase of cysteine cathepsin activity in carious dentin with increasing depth toward the pulp (Nascimento et al 2011) indicates that odontoblast or pulp-derived cysteine cathepsins may be important in expediting active caries lesions.…”

“…While salivary enzymes may readily access outer, caries-infected dentin, it is unlikely that they would contribute to destruction of caries-affected dentin (Toledano et al 2010;Vidal et al 2014), in which dentinal fluid rather than saliva (due to the hydrostatic pressure working in favor of an outward flow of dentinal fluid) may be the source of increased activities. Alternatively, dentin matrix-bound enzymes may not necessarily be readily activated after simple in vitro demineralization.…”

“…2). Within the oral cavity, cathepsins have also been associated with caries progression and failure of adhesive restorations over time (Breschi et al 2008;Liu et al 2011;Nascimento et al 2011;Tjäderhane et al 2013a;Vidal et al 2014).…”

Role of matrix metalloproteinases in dental caries, pulp and periapical inflammation: An overview

“…26 Higher abundance of cathepsin B and K in cariesaffected dentine as compared to intact dentine has been found in a recent study. 27 Salivary MMPs also tend to have a significant contribution towards dentine matrix degradation during the carious process. Endogenous MMP-2 contained in sound dentine is activated during the carious process.…”