Bioeffects of low-intensity continuous ultrasound (LICUS) on wound healing in corneal stromal cells in vitro

Corneal wound induced by traumatic injury to the cornea has developed as a clinical problem. Corneal stromal cells (keratocytes) play an important role in corneal injury occurred. Low-intensity ultrasound (US) is a noninvasive and safe technique therapeutic application. Low-intensity continuous ultrasound (LICUS), a form of low-intensity US is a fast-growing topic in tissue regeneration and treatment for diseases. However, the underlying cellular and molecular mechanisms of biological effects of LICUS on corneal wound healing, which are potentially related to the upregulation of cell proliferation and migration have rarely been reported. The current study aimed to determine whether LICUS had effective bioeffects on cellular wound healing and to determine the optimal LICUS intensity for accelerating the wound healing process in keratocytes in vitro. In the experiment, a linear scratch was introduced on the monolayer of keratocytes. The scratched regions are parallelly treated with several LICUS spatial-average intensities (no power, 15, 30, 50 mW/cm2) for 5 min per day. The wound healing assays were based on microscopic images (100 ×) after scratch introduced and following 24 h, 48 h, 72h. The area of the scratched region was quantitatively measured. The results showed that the initial area of scratch in all groups was 1.77 ± 0.04 mm2, LICUS intensity of 30 mW/cm2 displayed the most effective rate of treatment than other groups in the scratched regions, with the area of 1.2609 ± 0.08 mm2 at 24 h and the wound closed up at 48h. The intensity of 15 mW/cm2 and 50 mW/cm2 had comparable bioeffects on keratocytes, which totally healed at 72 h. These findings indicate that LICUS at 30 mW/cm2 intensity has the potential to be a treatment technique for traumatic corneal injuries.