Differential Expression of the α1 Type VIII Collagen Gene by Smooth Muscle Cells from Atherosclerotic Plaques of Apolipoprotein-E-Deficient Mice
We have investigated the morphology, growth and gene expression of smooth muscle cell (SMC) cultures derived from advanced atherosclerotic plaques and from non-plaque-containing aorta of individual apolipoprotein-E-deficient mice. The initial outgrowth of cells was faster from plaques (P) than from non-plaque segments (NP), but the cells in P cultures divided more slowly than NP cells in subcultures. By the 6th passage, the general growth pattern, morphology, ploidy and response to mitogenic factors of the cells were no longer consistently different in P and NP cultures. However, by the use of differential display, several transcripts were identified that were differentially expressed in three independent pairs of P and NP cultures. One of the transcripts, from a type VIII collagen gene, was elevated in all the P cultures compared to their NP counterparts even at the 40th passage. The α1 type VIII collagen transcripts were also readily detectable by RT-PCR in freshly dissected plaques, but not in the normal parts of aortas from the apolipoprotein-E-deficient mice. In situ hybridization showed that the transcripts were limited to the fibrous cap of plaques. Thus, SMCs from atherosclerotic plaques produce type VIII collagen and this differential expression continues when the cells are maintained in tissue culture.