Evaluation of Discoidin domain receptor 1 (DDR1) in junctional epithelial permeability and wound healing

Epithelium is the periodontal first line of defense against microbial attacks. Discoidin domain receptor 1 (DDR1) is a collagen receptor expressed at the epithelium. Mice not expressing the receptor (Ddr1^-/- mice) develop defects consistent with periodontitis, including epithelium downgrowth and bone loss. In this study, we investigated periodontal epithelial permeability by applying a fluorescent dye in the mouth of Ddr1^+/+ and Ddr1^-/- mice. Additionally, we used histological methods to reveal differences in the localization of gingival proteins between Ddr1^+/+ and Ddr1^-/-. Finally, we investigated the role of DDR1 in wound healing in human sections and in a live animal model. No differences in junctional epithelium (JE) permeability were observed between Ddr1^+/+ and Ddr1^-/- mice, as expressed by the comparable presence of dye in the periodontal tissues of both types of mice. There were no differences in the localization of E-cadherin or collagens IV, VIII, and XVII between Ddr1^+/+ and Ddr1^-/-. In human gingiva, DDR1 was expressed at the epithelial front, migrating to cover palatal wounds. The animal wound healing study revealed higher healing of skin wounds in Ddr1^-/- than Ddr1^+/+ mice at 5 dpw. In conclusion, this study has elucidated a role for DDR1 in epithelial cell migration during skin wound healing.