Reduced Dental Caries Susceptibility in Chromosome 2-Substituted Consomic Mice

Abstract

In this study, to clarify the effects on dental caries susceptibility of mouse chromosome 2 in vivo, we used chromosome 2 substitution mice (termed consomic mice), B6-Chr2^C3H. The consomic mice used in this study were based on high dental caries susceptibility strain C57BL/6CrSlc (B6), and only chromosome 2 from the low dental caries susceptibility strain C3H/HeSlc (C3H) was substituted. We induced dental caries in three inbred mice strains : B6, C3H and B6-Chr2^C3H. All mice were weaned at 21 days, were fed on Diet#2000, and were infected with Streptococcus mutans JC-2 to induce dental caries. The mandible bones were extracted at 49 days and observed by microscope and Micro-focus X-ray computed tomography images. The caries status was evaluated by calculating the dental caries score using the modified Keyes method. Mean dental caries scores of B6-Chr2^C3H, B6 and C3H were 8.1±3.4 (mean±S.D.), 46.5±1.3 and 2.2±1.0, respectively. Statistical analysis revealed that the dental caries score of B6-Chr2^C3H was significantly low compared with the score of B6 and there was no difference in dental caries score between C3H and B6-Chr2^C3H. The first fissures of the first molar in B6 and B6-Chr2^C3H were similar having a slight fossa at center area and which were differ from that of C3H. However, there was no significant difference in dental caries score at the fissure among B6-Chr2^C3H, B6 and C3H. And, the amount of saliva of B6-Chr2^C3H was significantly low than C3H, and significantly high than B6. These results suggested that the major genetic factor responsible for dental caries susceptibility is located on mouse chromosome 2.