Article Text

OP0027 Mechanical stress with silicon rod altered cartilaginous differentiatiation in pseudo-tendon sheath
1. Y Yutani,
2. Y Yamano
1. Department of Orthopaedic Surgery, Osaka City University Medical School, Osaka, Japan

## Abstract

Background In a joint-like sliding surface, undifferentiated mesenchymal cells have been reported to show expression of cartilage-specific genes and cartilage-specific matrix production.

Objectives In flexor tendon injury, tendon grafting is performed. When primary repair is impossible, a tendon sheath is constructed using a silicon rod. This area forms a sliding surface between the rod and the surrounding tissue, and cartilaginous differentiation is expected.

Methods The subjects were 22- and 46-year-old male patients. The mean interval between the injuries and insertion of the silicon rod was 13 months, and the mean interval until the second operation after insertion of the silicon rod was 4 months. Tissue was obtained from the inner and outer layer of the newly formed tendon sheath tissue. Total RNA was extracted directly from each tissue. For quantitative RT-PCR, the non-radioisotope method was used.

Results Although aggrecan was absent at the outer layer, the ratio of the expression of this gene to the expression of GAPDH was 0.15 at the inner layer of the newly formed tendon sheath. Gene expression of type II collagen was seen at a ratio of 0.28 at the inner layer, although it was also absent at the outer layer. On examining the gene expression of type I collagen and TGF-?A were 0.49 and 0.17, respectively. CD44 and HAS-2 gene expression were also confirmed.

Conclusion In the tissue evaluated in this study, the original tendon sheath had been destroyed, and new tissue formation was observed around the site of artificial tendon insertion. Generally, tissues in this region were considered just connective tissues. However, the newly synthsized tendon sheath showed expression of genes for aggrecan and type II collagen that were not observed in the surrounding tissue. These findings together with expression of TGF-?A suggest alterations in the tissue differentiation function in this area. In the tissue of this area, mechanical stimulation may have played an important role in the differentiation of mesenchymal tissue.

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