Background: Low-intensity pulsed ultrasound (LIPUS) has been used in fracture treatment to shorten the time needed for biologic wound healing. Clinical trials applying LIPUS in implant dentistry have reported accelerated soft-tissue healing and osseointegration. However, details of the clinical effects of LIPUS have not been well characterized. Connective tissue growth factor (CCN2/CTGF) plays an important role in wound healing and angiogenesis in periodontal tissue. In this study, we focus on the effect of LIPUS on gingival epithelial cells and the role of CCN2/CTGF therein.
Methods: Gingival epithelial cells (GE1) were cultured in six-well cell-culture plates for 24 hours at 37°C with 5% CO(2), and then exposed to LIPUS for 15 minutes at 3-MHz frequency and 40-mW/cm(2) power. Total RNA was extracted after LIPUS exposure and analyzed by real-time polymerase chain reaction to detect CCN2/CTGF. Additionally, total protein from each sample after LIPUS exposure was immunoblotted with anti-CCN2/CTGF antibody.
Results: LIPUS exposure increased the mRNA level of CCN2/CTGF on exposure, and the level was significantly greater at 0 and 15 minutes after LIPUS exposure compared to the control. Western blotting analysis showed intense staining of CCN2/CTGF for 60 minutes after LIPUS exposure. The results demonstrate that LIPUS exposure accelerates soft-tissue healing by increasing CCN2/CTGF on exposure, in addition to its effects on bone formation.
Conclusion: Our findings demonstrate that LIPUS exposure accelerates soft-tissue healing by increasing connective tissue growth factors via a mitogen-activated protein kinase signaling pathway on exposure.