Repair of arterial injury produced by balloon angioplasty leads to the formation of a neointima and a narrowing of the vascular lumen. In this study, we examined the possibility that smooth muscle cells (SMC) in injured rat carotid arteries are stimulated to produce type-1 transforming growth factor-beta (TGF-beta 1) during neointima formation in vivo. Levels of TGF-beta 1 transcripts (2.4 kb) were significantly increased within 6 h after carotid injury and reached a maximum (five to sevenfold) by 24 h. Regenerating left carotids had sustained increases in TGF-beta 1 mRNA levels (about fivefold) over the next 2 wk, during which time a substantial neointimal thickening was formed. No changes in basal TGF-beta 1 mRNA levels were found in contralateral uninjured carotids at any of the times examined. Immunohistochemical studies showed that a large majority of neointimal SMC were stained for TGF-beta 1 protein in an intracellular pattern, consistent with active TGF-beta 1 synthesis in this tissue. Neointima formation and TGF-beta 1 immunoreactivity were correlated with increases in fibronectin, collagen alpha 2(I), and collagen alpha 1(III) gene expression. Infusion of purified, recombinant TGF-beta 1 into rats with a preexisting neointima produced a significant stimulation of carotid neointimal SMC DNA synthesis. These results suggest that TGF-beta 1 plays an important role as an endogenous growth regulatory factor produced by neointimal SMC themselves during progressive neointimal thickening after balloon angioplasty.
M W Majesky, V Lindner, D R Twardzik, S M Schwartz, M A Reidy
The Editorial Board will only consider comments that are deemed relevant and of interest to readers. The Journal will not post data that have not been subjected to peer review; or a comment that is essentially a reiteration of another comment.