cDNA cloning of human allograft inflammatory factor-1: Tissue distribution, mRNA induction, and expression in vascular restenosis

The resultant neointima formation associated with balloon angioplasty is a dynamic process actively involving several different cell types. The principle cellular component of the restenotic lesion, the vascular smooth muscle cell (VSMC), responds to vascular trauma by production of soluble growth and chemotactic factors. We have previously identified a partial cDNA fragment obtained from mRNA differential display of rat carotid arteries subject to balloon angioplasty, which is undetectable in naive vessels, detected at low levels 6 hours, peaks at 3 days, and declines 14 days post surgery. Using a PCR fragment of this clone to screen a human cDNA library, we now report the isolation and characterization of a full length clone, which is 98% homologous at the amino acid level to the rat Allograft Inflammatory Factor-1 (AIF-1), which has previously been reported to be expressed hi rat macrophages. This human AIF-1 homologue presents the same mRNA expression pattern in balloon angioplasty-damaged rat carotid arteries, and is inducable in stimulated human smooth muscle cells. Interestingly, human tissue distribution indicates constituative expression in lymphoid tissue, and is inducable hi activated lymphocytes. In summary, human AIF represents an indueible, tissue-specific transcript transiently expressed in response to vascular trauma.