Significance of changes in transforming growth factor-beta mRNA levels in autogenous vein grafts

This study was designed to investigate changes in mRNA levels of transforming growth factor-beta (TGF-beta), collagen I, and collagen III in autogenous vein grafts.

Twenty-four New Zealand rabbits were randomly divided into 4 groups with 6 rabbits each. The external jugular veins of the New Zealand rabbits were harvested and grafted into the ipsilateral carotid artery. All rabbits were fed with a standard diet. After the operation, the rabbits were sacrificed at 1, 2, 3, or 4 weeks. TGF-beta, collagen I, and collagen III mRNA levels in the venous grafts were measured by semiquantitative methods at every time point. The contralateral external jugular veins were also harvested and analyzed as controls. Glyceraldehyde-3-phosphate dehydrogenase was used as an internal standard to normalize all samples for potential variations in mRNA content. In order to observe the expression of TGF-beta protein, immunohistochemical SABC methods were used.

One week postoperation, the mRNA level of TGF-beta was upregulated to 1.73 +/- 0.19 in the vein graft and 1.21 +/- 0.16 in the control vein (P < 0.01). High mRNA levels were maintained until week 4 postoperation. The mRNA levels of collagen I and collagen III were also significantly increased to 2.18 +/- 0.21 versus 1.12 +/- 0.24 and 1.08 +/- 0.13 versus 0.83 +/- 0.12, respectively (P < 0.05). Immunohistochemical staining revealed a higher density of TGF-beta expression in the vein grafts.

An uninterrupted increase in mRNA levels of TGF-beta, collagen I, and collagen III is observed in autogenous vein grafts. This increase may be the major cause of intimal hyperplasia, sclerosis, and even graft failure.