The MI model was created by
ligation of the left anterior descending coronary artery in rats. We detected cardiac
integrins beta1 and beta3 gene expression (quantitative in situ hybridization) and
protein production (Western blot and immunohistochemistry) and potential regulation by
tumor necrosis factor (TNF) using neonatal ventricular myocytes and TNF-/- knockout mice.
Integrins beta1 and beta3 gene expression and
protein production were low in
sham-operated hearts. After MI, the beta1 and beta3
mRNA and
proteins were significantly increased at the site of MI at day 3, reached a peak at day 7, and gradually declined thereafter.
Integrin beta1A localized primarily in fibroblasts and inflammatory cells, beta1D localized in myocytes, and
integrin beta3 was associated primarily with endothelial and smooth muscle cells in peri-
infarct vessels. In cultured myocytes, there was
isoform transition from the adult beta1D to the fetal beta1A on exposure to
TNF-alpha. This was confirmed in vivo in the peri-
infarct myocytes, but the transition was voided in TNF-/--knockout mice.
CONCLUSIONS: