HERTWIG’S EPITHELIAL ROOT SHEATH PROTEINS AND PERIODONTAL LIGAMENT CELL DIFFERENTIATION

Objective:  In order to achieve complete regeneration of the attachment apparatus it is necessary to recapitulate the developmental process involved in the formation of the periodontium. Hertwig’s epithelial root sheath (HERS) initiate this process, therefore we propose that proteins secreted by HERS induce PDL to differentiate into periodontium. In this study we tested if, and which type of proteins secreted by these cells have the ability to induce changes in PDL cells maintained in vitro.

Method:  HERS cells were grown in differentiation conditions, the media was collected (HERS-CM), passed through a Heparin column and proteins eluted (NB) or retained in the column (B) were collected. PDL cells were grown for 28 days under differentiating conditions in the presence of HERS-CM-NB, HERS-CM-B or alone (control). The effect of the HERS-CMs on the phenotype of these cells was determined using RT-PCR DNA Microarrays (SABiosciences, CA).

Result: Results indicate that there were major changes in the phenotype of cells grown alone or in the presence of HERS-CM- NB or B. Amongst the most significant changes were the reduced expression of MSX1, MMP10, TGB-1, -2, -3 and VEGFa in PDL cells treated with either HERS-CM fractions. In contrast, marked increased in expression of BMPr1b, BMP2, FGF3, TNF, DSPP and several collagens was seen in cells grown in the presence of HERS-CM-B. Addition of HERS-CM-NB resulted in decreased expression of several genes in particular, BGN and CDH11.

Conclusion:  Our studies suggest that HERS can modulate PDL cell differentiation resulting in formation of the periodontium in normal tooth development. Further characterization of these modulators can result in new therapeutics to regenerate the periodontium. This study was supported by NIDCR grants DE12346 and DE19792.