[Experimental study on the tracheal allografts with decreased antigenicity]

To investigate effect of the removal of epithelium and mixed glands from the tracheal allografts on the graft-immunosuppression.

Fresh untreated tracheal allografts, cryopreserved tracheal allografts, and 10 off-epithelium tracheal allografts were obtained from 25 male SD rats. Fresh untreated tracheal allografts (40) were divided into 4 groups and dipped respectively in the solution of protease XIV in 0, 0. 1, 0.3 and 0.5 mg/ml at 4 C for 12 hours. Thirty recipient male SD rats were randomly and equally divided into group A (fresh untreated tracheal allografts), group B (cryopreserved tracheal allografts), and group C (off-epithelium tracheal allografts). The transplanted allografts were implanted into the abdominal cavity of other rats by being embedded in the greater omentum. Twenty-one days after transplantation, the tracheal graft segments were surgically removed, and then were initially fixed in cold 10% neutral buffered formalin solution for hematoxylineosin staining. Histological observation and lymphocyte infiltration were performed on the grafts to evaluate rejection.

The 0.3 mg/ml protease XIV could remove the epithelium and mixed glands of the grafts completely, but did no damage to cartilage. The cartilages of each group all survived and were revascularized. The lumens of group A were filled with granulation and necrosis tissue. In contrast, group B was filled with a few granulation tissues and group C was not at all. The number of lymphocyte infiltration in group A, B, and C was 29.16 +/- 2.69/HP, 15.17 +/- 2.19/HP, and 11.56 +/- 0.87/HP respectively. There was significant difference between group A and both group B and group C (P < 0.05), and there was significant difference between group B and group C (P < 0.05). Therefore, the grade of graft-rejection was group A > group B > group C.

The 0.3 mg/ml protease XIV can completely remove the epithelium and mixed glands of grafts at 4 C for 12 hours, and it preserves the normal structure of cartilage. The antigenicity of tracheal grafts can be greatly reduced by removing the epithelium and by the cryopreservation. The prior tracheal allograft in the omentum is feasible for the revascularization of the grafts.