Extracts of irradiated mature human tooth crowns contain MMP-20 protein and activity

Abstract

Objectives We recently demonstrated a significant correlation between enamel delamination and tooth-level radiation dose in oral cancer patients. Since radiation can induce the synthesis and activation of matrix metalloproteinases, we hypothesized that irradiated teeth may contain active matrix metalloproteinases. Materials and Methods Extracted teeth from oral cancer patients treated with radiotherapy and from healthy subjects were compared. Extracted mature third molars from healthy subjects were irradiated in vitro and/or incubated for 0 to 6 months at 37°C. All teeth were then pulverized, extracted, and extracts subjected to proteomic and enzymatic analyses. Results Screening of irradiated crown extracts using mass spectrometry identified MMP-20 (enamelysin) which is expressed developmentally in dentin and enamel but believed to be removed prior to tooth eruption. MMP-20 was composed of catalytically active forms at Mr=43, 41, 24 and 22 kDa and was immunolocalized predominantly to the morphological dentin enamel junction. The proportion of different sized MMP-20 forms changed with incubation and irradiation. While the pattern was not altered directly by irradiation of healthy teeth with 70 G, subsequent incubation at 37°C for 3–6 months with or without prior irradiation caused the proportion of Mr=24–22 kDa MMP-20 bands to increase dramatically. Extracts of teeth from oral cancer patients who received >70 Gy radiation also contained relatively more 24 and 22 kDa MMP-20 than those of healthy age-related teeth. Conclusion MMP-20 is a radiation-resistant component of mature tooth crowns enriched in the dentin-enamel. We speculate that MMP-20 catalyzed degradation of organic matrix at this site could lead to enamel delamination associated with oral cancer radiotherapy.

Structural Analysis of Enamel in Teeth from Head-and-Neck Cancer Patients Who Underwent Radiotherapy

“…In this context, a recently published study demonstrated a higher expression of matrix metalloproteinase-20, also called enamelysin, in the dentin-enamel junction surroundings of in vitro irradiated teeth. The proteolytic activity of matrix metalloproteinase-20 could also degrade the complex structure of noncollagenous proteins such as amelogenin and ameloblastin located in the enamel organic matrix in interprismatic enamel, leading to enamel delamination and contributing to the etiology of radiation-related caries [McGuire et al, 2014b].…”

Type IV Collagen is a Novel DEJ Biomarker that is Reduced by Radiotherapy

“…In vitro radiation exposure was done at a cancer treatment center (Kansas City Cancer Center, Kansas City, KS, USA) using a linear accelerator 2100iX (Varian Medical Systems, Palo Alto, CA, USA) with an energy of 6 MV photons. Additionally, another group of extracted teeth (n = 5; in vivo-irradiated; IRB13-143), described previously in detail, was also collected (McGuire et al, 2014a). Briefly, the tooth-level radiation dose was > 60 Gy during treatment for oral cancer from donors > 40 yr old, and the teeth were extracted ≥ 2 yr post-radiotherapy.…”

“…These findings suggest a radiogenic effect on tooth structure with increasing radiation dose to the tooth. To better understand radiotherapy-induced DEJ instability leading to dentition breakdown, our group is focused on characterizing the structure, properties, and biochemical composition (Dusevich et al, 2012;Xu et al, 2012;McGuire et al, 2014b) of the DEJ, as well as postradiation changes (McGuire et al, 2014a).…”

ATR-FTIR Assessment of the Biochemical Composition and Micro Hardness of the Hard Tissues of Oral Cavity Submitted to Gamma Irradiation

“…For root dentin, with higher organic content than enamel, it was the most affected by gamma radiation compared to enamel ad coronary dentin, as demonstrated in the literature [6][7][8].…”