Cardiotrophin-1 (CT-1) is a cytokine belonging to the interleukin-6 superfamily that exhibits trophic and survival properties in a number of cell types. CT-1 protein expression has recently been identified within the media of atherosclerotic arteries, but its role in the vessel is still unknown. The present study was designed to investigate the effects of CT-1 in vascular smooth muscle cells (VSMC) and its involvement in the arterial phenotype of CT-1-null mice.

Rat aorta primary cultured VSMC were stimulated with CT-1 (10-11-10-9M) and/or antibodies against CT-1 receptors (LIFR or gp130), and/or chemical inhibitors against CT-1-activated intracellular pathways, for up to 48 hours. Cell proliferation was determined by MTT assay and ki67 immunodetection. The expression of collagen type I and III, elastin and fibronectin was quantified by RT-PCR and Western blot. Matrix metalloproteinases (MMPs) activities were assessed by gelatin and casein zymographies. Arterial mechanical properties were evaluated in 2 years-old WT (n=8) and CT-1-null mice (n=3) by echo-tracking device. Circumferential wall stress, incremental elastic modulus (Einc), media cross-sectional area and collagen and elastin content were recorded.

CT-1 induced VSMC proliferation in a dose-dependent manner (p<0.01). CT-1 also increased mRNA and protein expression of collagen type I (p<0.01), collagen type III (p<0.01), fibronectin (p<0.05) and elastin (p<0.05), with a parallel and dose-dependent increase in active MMP-2 (p<0.01), MMP-3 (p<0.05) and MMP- 9 (p<0.01). All these effects were reversed in the presence of antibodies against CT-1 receptors and intracellular chemical inhibitors. CT-1-null mice presented an increased wall stress (p<0.05) and Einc (p<0.05) as compared with WT mice. Media cross sectional area and collagen content were reduced (p<0.05) in mice lacking CT-1.

In summary, CT-1 induced cell proliferation and a secretory phenotype in VSMC. Moreover, mice lacking CT-1 presented a reduced carotid stiffness accompanied by a reduced media thickness and collagen content. Data here presented suggest that CT-1 actions in VSMC facilitate extracellular matrix deposition and arterial stiffness.