Transforming growth factor-2 is associated with atherosclerotic plaque stability and lower risk for cardiovascular events

Aims Transforming growth factor-beta (TGF-beta) exists in three isoforms TGF-beta 1, -beta 2, and -beta 3. TGF-beta 1 has been suggested to be important for maintaining plaque stability, yet the role of TGF-beta 2 and -beta 3 in atherosclerosis remains to be investigated. This study explores the association of the three isoforms of TGF-beta with plaque stability in the human atherosclerotic disease. Methods and results TGF-beta 1, -beta 2, and -beta 3 proteins were quantified in 223 human carotid plaques by immunoassays. Indications for the endarterectomy were: symptomatic carotid plaque with stenosis >70% or without symptoms and >80% stenosis. Plaque mRNA levels were assessed by RNA sequencing. Plaque components and extracellular matrix were measured histologically and biochemically. Matrix metalloproteinases and monocyte chemoattractant protein-1 (MCP-1) was measured with immunoassays. The effect of TGF-beta 2 on inflammation and protease activity was investigated in vitro using THP-1 and RAW264.7 macrophages. Patients were followed longitudinally for cardiovascular (CV) events. TGF-beta 2 was the most abundant isoform and was increased at both protein and mRNA levels in asymptomatic plaques. TGF-beta 2 was the main determinant separating asymptomatic plaques in an Orthogonal Projections to Latent Structures Discriminant Analysis. TGF-beta 2 correlated positively to features of plaque stability and inversely to markers of plaque vulnerability. TGF-beta 2 was the only isoform inversely correlated to the matrix-degrading matrix metalloproteinase-9 and inflammation in the plaque tissue. In vitro, TGF-beta 2 pre-treatment reduced MCP-1 gene and protein levels as well as matrix metalloproteinase-9 gene levels and activity. Patients with plaques with high TGF-beta 2 levels had a lower risk to suffer from future CV events. Conclusions TGF-beta 2 is the most abundant TGF-beta isoform in human plaques and may maintain plaque stability by decreasing inflammation and matrix degradation.