Can therapeutic ultrasound influence the integration of skin grafts?

Therapeutic ultrasound (TUS) is a widely used coadjuvant physical means to promote biological tissue repair. In the present investigation, the influence of TUS on the integration of full-thickness skin graft was studied in rabbits. Twenty female adult rabbits were used and two 2x2-cm square full-thickness skin grafts were obtained from both scapular regions and swapped, the one cut out on the right being placed on the left and vice versa. The graft on the right was irradiated with TUS (3 MHz, 0.5 W/cm2, 5-min duration) once a day for seven consecutive days, beginning on the third postoperative day; the graft on the left was submitted to simulated irradiation. The animals were killed on the 11th day and the grafted areas were resected (graft+safety margin) for histological examination. Five-mum-thick sections were alternatively stained with Gomori's trichrome, proliferating cell nuclear antigen (PCNA) and picrosirius red and examined under the light microscope, and the epidermal and dermal areas were measured and proliferating cells and new blood vessels counted. The results showed a significant increase (p=0.007) in the number of proliferating epidermal cells (12.18% and 7.34% of the total number of cells in the irradiated and control grafts, respectively) and new blood vessels per field (p=0.0001) in the irradiated grafts (6.27 compared with 3.07). Despite the increased number of proliferating cells and blood vessels, there was no significant difference between the epidermis (246,392 microm2 and 200,626 microm2 in groups 1 and 2, respectively; p=0.07) and dermis (2,157,730 microm2 and 2,109,150 microm2 in groups 1 and 2, respectively; p=0.21) areas as a function of thickness for both groups. We conclude that TUS induces morphological alterations in biological processes, such as epidermic germinative layer cell proliferation and neoangiogenesis, which are involved in the integration of full-thickness skin grafts. This has a potential for clinical use in humans.