Original article
Expression of growth factors in the early phase of supraspinatus tendon healing in rabbits

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Growth factors are known to appear during wound healing. We hypothesized that growth factors would also appear during the healing process of a rotator cuff tear. We determined the expression of various growth factors during healing of acute rotator cuff tears in the rabbit. We made a full-thickness defect in the supraspinatus tendon of 27 Japanese white rabbits. The shoulders were harvested on days 1, 3, 5, 7, 9, 11, 14, 21, and 28 postoperatively (n = 3 at each time point). We assessed the expression of basic fibroblast growth factor, insulin-like growth factor 1, platelet-derived growth factor, and transforming growth factor β. Basic fibroblast growth factor appeared with its peak on days 7 and 9, insulin-like growth factor 1 appeared with its peak on day 5, platelet-derived growth factor appeared with a mild expression between days 7 and 14, and transforming growth factor β appeared with constant mild expression throughout the observation period. It is likely that each of these growth factors plays a role in the early phase of healing of the supraspinatus tendon in rabbits.

Section snippets

Animal model

The Animal Research Committee of Akita University, Akita, Japan, approved the protocols for animal experimentation described in this study; all subsequent animal experiments adhered to the “Guidelines for Animal Experimentation” of the university.

Twenty-seven Japanese white rabbits (body weight, 2.2-4.0 kg; mean, 2.8 kg) were used in this study. Rabbits seemed to be an appropriate animal model in which to perform our study, because there had been many studies conducted in the literature using

Macroscopic findings

On day 1 and day 3, the defect was mainly filled with blood clot. On day 5, a synovium-like tissue started to cover the defect, which gradually became a tendon-like tissue. The border of the defect became indistinct on day 21 and unidentifiable on day 28 (Figure 2). These findings were more or less the same in all of the rabbits observed in each time point.

Histologic findings

There was synovium-like tissue with blood cells in the defect on day 1. This thin, synovium-like tissue started to extend proximally and

Discussion

The poor healing capacity of the torn rotator cuff is well known. Once torn, the rotator cuff tear either remains the same size or expands in size with time.16, 33 Currently, no therapeutic agents are available in terms of healing the torn tendon. Thus, surgical repair is the only treatment option when conservative treatment fails. Therefore, any agent that has the ability to promote tendon healing of the torn rotator cuff would appear to be beneficial.

Significant proliferation of reparative

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