I–4 The Effect of Low-Intensity Pulsed Ultrasound (LIPUS) on Human Rotator Cuff Derived Cells

Abstract

Objective: A re-tear after rotator cuff repair is one of the most common complications. Insufficient healing of the tendon-to-bone junction has been reported in re-tear cases. LIPUS has been shown to stimulate soft tissue healing. Therefore, we investigated the effect of LIPUS on human rotator cuff-derived cells, hypothesizing that their differentiation potential would be increased by LIPUS exposure. Methods: (Osteogenesis) Cells were divided into 2 groups; LIPUS-treated cells and non-treated control cells. After both cell media were replaced with osteogenic medium, LIPUS-treated cells were exposed for 20 minutes a day for 5 or 10 days; control cells were unexposed. Number of cells was counted at day 10, and cells were analyzed by Alizarin Red staining. Real time PCR analyses of ALP and Runx2 were also performed at day 5 and day 10. (Tenogenesis) Cells were divided into 2 groups, and treated as above. Real time PCR analyses of type I collagen, type III collagen, and Scleraxis were performed at day 5 and day 10. Results: There was no significant difference in total number of cells between the 2 groups at day 10, but LIPUS-treated cells were well stained by Alizarin Red, compared to the control group. In LIPUS-treated cells, expression of ALP and Runx2 was higher than in control cells. In LIPUS-treated cells, expression of type I and type III collagen, and scleraxis was also higher than in the control group at day 5. Discussion: It is important to regenerate the tendon-to-bone junction after surgery. Healing this junction in the early repair phase consists of forming scar tissue that is weaker than the native insertion. LIPUS exposure increased osteogenesis and tenogenesis of human rotator cuff-derived cells. LIPUS exposure may accelerate healing of the tendon-to-bone interface in vivo after rotator cuff repair.