The effect of aging on the functions of epithelial rest cells of Malassez in vitro: immunofluorescence, DNA microarray and RT-PCR analyses

Analysis of the cells isolated from epithelial cell rests of Malassez through single-cell limiting dilution

The epithelial cell rests of Malassez (ERM) are essential in preventing ankylosis between the alveolar bone and the tooth (dentoalveolar ankylosis). Despite extensive research, the mechanism by which ERM cells suppress ankylosis remains uncertain; perhaps its varied population is to reason. Therefore, in this study, eighteen unique clones of ERM (CRUDE) were isolated using the single-cell limiting dilution and designated as ERM 1-18. qRT-PCR, ELISA, and western blot analyses revealed that ERM-2 and -3 had the highest and lowest amelogenin expression, respectively. Mineralization of human periodontal ligament fibroblasts (HPDLF) was reduced in vitro co-culture with CRUDE ERM, ERM-2, and -3 cells, but recovered when an anti-amelogenin antibody was introduced. Transplanted rat molars grown in ERM-2 cell supernatants produced substantially less bone than those cultured in other cell supernatants; inhibition was rescued when an anti-amelogenin antibody was added to the supernatants. Anti-Osterix antibody staining was used to confirm the development of new bones. In addition, next-generation sequencing (NGS) data were analysed to discover genes related to the distinct roles of CRUDE ERM, ERM-2, and ERM-3. According to this study, amelogenin produced by ERM cells helps to prevent dentoalveolar ankylosis and maintain periodontal ligament (PDL) space, depending on their clonal diversity.

Promotion of mouse ameloblast proliferation by Lgr5 mediated integrin signaling

Rodent incisors grow throughout the animal's lives, and the tooth-forming cells are provided from proximal ends of the incisors where the tooth epithelium forms a stem cell niche called cervical loop. The committing cells in a cervical loop actively begin to proliferate (pre-ameloblasts), and differentiating into ameloblasts. This study showed that the lower incisors of mice null for CD61 (CD61(-/-) ), also known as integrin β3, were significantly shorter than those of the wild-type mice at 8-week-old. The protein and mRNA expressions levels of Fgfr2, Lgr5, and Notch1, which are known to be involved in pre-ameloblastic cell proliferation and stem cell maintenance, were reduced in the cervical loop of 2-week-old CD61(-/-) mice. The proliferation of pre-ameloblasts was reduced in CD61(-/-) ameloblasts. The siRNA-mediated suppression of CD61 (siCD61) reduced the proliferation of pre-ameloblastic cell line ALC, and the expression levels of Lgr5 and Notch1 were reduced by the transfection with siCD61. The suppression of Lgr5 by transfection with siLgr5 suppressed the proliferation of the ALC cells. These results suggested that CD61 signaling is required for the proper growth of the cervical loop and for the promotion of the proliferation of pre-ameloblastic cells through Lgr5.