Dynamics of Myofibroblasts and Transforming Growth Factor-beta 1 in CO2 Laser-enhanced Healing Process of Rat Tooth Sockets

: Objective: The usefulness of laser irradiation for socket preservation in clinical cases has recently been reported, and the effective laser irradiation conditions for healing of the extraction wound have also been investigated. It was reported by our laboratory that HLLT and LLLT therapies using a CO 2 laser for extraction sockets resulted in characteristic new bone formation and the maintenance of a high alveolar crest in rats. However, the mechanism of healing promotion by CO 2 laser irradiation remains unclear, so we investigated the emergence of myofibroblasts （ α -smooth muscle actin （ α -SMA）） involved in granulation tissue scar contracture in extraction wounds and changes in the expression of transforming growth factor-beta 1 （TGF- β 1） associated with myofibroblast differentiation and apoptosis. Subjects and Methods: Seventy-two 5-week-old male Wistar rats were used. The first molar was extracted to prepare an extraction socket model. The rats were divided into CO 2 laser-irradiated and non-irradiated （control） groups and pathological-ly compared. In the CO 2 laser-irradiated group, HLLT was performed immediately after tooth extraction, followed by LLLT after one day, corresponding to clinical cases. The irradiated tissue including the extraction socket was excised 6 hours and 3, 5, 7, 10, and 21 days after treatment, fixed in 4％ paraformaldehyde, decalcified in 10％ EDTA solution, and paraffin-embedded employing the standard method, and serial sagittal sections were prepared. Granulation tissue of the superficial layer of the extraction socket was immunohistologically investigated using anti- α -SMA and anti-TGF- β 1 antibodies. The number of α -SMA-positive cells and TGF- β 1-positive area were measured, and the significance of differences was tested. Results: On immunostaining with anti- α -SMA antibody, there were many α -SMA-positive cells in the non-irradiated group at 3 and 7 days, whereas significantly fewer positive cells were noted in the CO 2 laser-irradiated group （p ＜ 0.05）. On immunostaining with anti-TGF- β 1 antibody, TGF- β 1-positivity was not marked the CO 2 laser-irradiated group, compared to that in the non-irradiated group, significant difference was noted 5 days treatment Conclusion: The combination of CO 2 HLLT and LLLT for the extraction sockets inhibited scar formation in the sockets, and the involvement of TGF- β 1 suggested.