CO₂ laser therapy accelerates the healing of ulcers in the oral mucosa by inducing the expressions of heat shock protein-70 and tenascin C

The treatment of ulceration or stomatitis with laser therapy is known to accelerate healing and relieve pain, but the underlying biological mechanism is not fully understood. The present study used a mouse model of ulceration to investigate the molecular mechanisms by which CO₂ laser therapy accelerated the wound healing process. An ulcer was experimentally created in the palatal mucosa of the mouse and irradiated with light from a CO₂ laser. Compared with controls (no irradiation), laser irradiation induced the proliferation of epithelial cells and faster re-epithelialization of the wound area. Immunohistochemistry experiments showed that heat shock protein-70 (HSP70) was expressed mainly in the epithelium of normal palatal tissue, whereas there was little tenascin C (TnC) expression in the epithelium and mesenchyme under normal conditions. Laser irradiation induced HSP70 mRNA and protein expression in the lamina propria as well as TnC expression in the mesenchyme underlying the renewing epithelium. Epithelial cells and fibroblasts were exposed to heated culture medium or laser irradiation to establish whether hyperthermia mimicked the effect of laser irradiation. Culture of fibroblasts in heated medium increased the expressions of both TnC and TGF-β1, whereas laser irradiation induced only TnC expression. The present study indicates that CO₂ laser irradiation exerts a photobiogenic effect to up-regulate TnC expression without inducing TGF-β1 expression. We suggest that CO₂ laser therapy has an advantage over thermal stimulation.

Immunohistochemical expression of fibrillin-1 and fibrillin-2 during tooth development

BACKGROUND AND OBJECTIVE

Oxytalan fibers are categorized as a microfibril assembly without elastin deposition, and are unique components in the periodontal ligament (PDL). However, little is known about their formation during PDL development. To clarify the mechanisms of oxytalan fiber formation in developing PDL, we performed immunohistochemical analysis to detect the direct expression of fibrillin-1 and fibrillin-2, which are major components of microfibrils.

MATERIAL AND METHODS

Frozen sections of lower molars from mice at several stages of growth were prepared without chemical fixation and decalcification using the film transfer method. Immunostaining was performed with anti-fibrillin-1 and -2, and anticytokeratin antibodies.

RESULTS

Fibrillin-1 was not expressed in the dental follicle during the crown forming stage. At postneonatal day 9, fibrillin-1 expression started with meshwork appearance between the epithelial cells from Hertwig's epithelial root sheath at the root dentin surface. Fibirillin-2 was detected much earlier than fibrillin-1 expression. Fibrillin-2 was expressed with a liner appearance, running parallel to the root axis in PDL, and was partially co-expressed with cytokeratin 14 expression in Hertwig's epithelial root sheath. Furthermore, we detected both fibrillin-1 and fibrillin-2 expression in human PDL. Fibrillin-1 was detected in fibers with a vertically oriented root axis in PDL. Fibrillin-2 was widely expressed in PDL, including around the epithelial cell rests of Malassez. Fibrillin-1 and fibrillin-2 were clearly co-expressed in thick fiber structures in human PDL.

CONCLUSION

Our results suggest that both fibrillin-1 and fibrillin-2 expression is required to form thick oxytalan fibers in PDL. Based on the expression patterns for fibrillin-1 and fibrillin-2, they have different functions during tooth root and PDL development. Early expression of fibrillin-2 may regulate dental epithelial cell behavior during root and PDL development.