The role of CD44 in periodontal ligament organization and repair

Abstract

Periodontal ligament development and adaptation is fundamental for the proper function of dentition. The periodontal ligament (PDL) provides structural support for the teeth within the alveolar bone. Derived embryonically from the ectomesenchyme of the dental follicle, the PDL is a complex connective tissue composed of many cells including fibroblasts, macrophages, cementum cells, bone cells, as well as vascular and neural elements. The PDL is capable of high turnover rates as seen in orthodontic tooth movement. CD44, a multifunctional cell surface glycoprotein that is involved in cellular interactions, is thought to play an important role in the cellular organization of the PDL as well as in the migration of reparative cells after PDL injury. The purpose of this study was to determine the significance of CD44 during normal PDL adaptation and during PDL repair in response to orthodontic injury. At 41 days postnatal (dpn) four wild-type and four CD44 knockout mice were sacrificed and prepped for histological analysis. Histological sections were prepared and analyzed using Canvas software. Fibroblast cell angles were measured with respect to the root surface 20 µm below the cementoenamel junction (CEJ). A previous study found a significant difference between the PDL fibroblast angle measurements of CD44 knockout and wild-type mice at day 26 dpn; however, no significant difference was noted at day 41 dpn. This finding suggests that the lost function of CD44 is capable of correcting itself in the CD44 knockout mice, or that there are other receptors found in the PDL, such as RHAMM, that compensate for the function of the CD44 receptor. In order to explore the significance of CD44 in PDL repair after orthodontic tooth movement an orthodontic wire was placed unilaterally on the maxilla of 21 wild-type and five CD44 knockout mice at day 31 dpn. Wires were activated for 5 days before being cut to allow for recovery. Mice were sacrificed at day 41 dpn and prepped for histological analysis. Results of this study are to be determined.