Healing tissue response with ITU (Intense Therapy Ultrasound) in musculoskeletal tissue, feasibility study

Background/ Objective: ITU effectively creates thermal injury zones inside soft tissue, initiating a tissue repair cascade in the skin, promoting collagen generation. It may be feasible to promote a robust healing response in musculoskeletal tissue accelerating healing from injury. The objective of the study is to establish feasibility of generating healing response via ITU thermal injuries in live rabbit Achilles tendon model. Protocol/Methods: The rabbit studies were performed under protocol approved by IACUC, University of Arizona. Anesthetized animals were imaged with conventional ultrasound (Spark, Ardent Sound, AZ, USA). The Achilles tendon of one limb was exposed and partially transected, the other tendon exposed only and served as an operative control. 24 hours post-surgery Achilles tendons were treated with ITU (Gen 2, GTS, AZ, USA). One set of 2 rabbits, 4 tendons represented 4 groups (cut or not, treated or not). At time points of 4, 14 and 21 days post-treatment the tendons were explanted and subjected to PCR to examine growth factors, cytokine and collagen gene expression. At time points 14 and 21 days tendons were mechanically tested to measure stress-strain curves and rupture strength. Five sets of rabbits (20 tendons) were sacrificed: 1 at 4 days, 2 each at 14 days and 21 days. At all time points the limbs were ultrasonically imaged and recorded. Results and Conclusions: Results of PCR showed significant increase of the growth factors (TGFβ1), inflammation related interleukin-1 beta (IL-1β) and expected time related reduction and increase Collagen 1A1 and Collagen 1A2. Ultrasound images showed complete tendons´ recovery at time points of 21 days when treated with ITU. Mechanical testing for stress-strain and rupture showed no compromise in ITU treated tendons vs. control: uncut/untreated tendons. In conclusion, feasibility of initiating a healing cascade in musculoskeletal tissue in live animal model was demonstrated utilizing ITU.