Cholesterol loading in vivo and in vitro alters extracellular matrix proteins production in smooth muscle cells

Abstract

This study supports the SMC dedifferentiation in vitro model and increases our fundamental knowledge of plaque formation and remodeling. With this purpose, we isolated smooth muscle cells form aortic arch of chicks either fed under control or high cholesterol diets. From the former we obtained control SMCs (SMC−C) that were then loaded with cholesterol using cholesterol:methyl‐β‐cyclodextrin (CS) complexes, thus producing cholesterol loaded SMCs in vitro (SMC−C+CS).tained in vivo cholesterol loaded SMC cell cultures (SMC−Ch). We compared the effect of both cholesterol loading processes on extracellular matrix (ECM) production. The proline incorporation showed that collagen synthesis was higher in SMC−Ch and SMC−C+CS than in SMC−C cultures. Quantitative real‐time PCR revealed that expression of extracellular matrix protein‐related genes increased after in vitro and in vivo cholesterol loading with respect to unloaded cells, demonstrating a regulation at mRNA level. In addition, the expression of col3a1 and fibronectin genes was significantly higher in SMC−Ch than in SMC−Ch+CS cultures. We demonstrated that SMC can switch from contractile to synthetic state not only by cholesterol in vivo but also by cholesterol SMC loading in vitro. Practical applications: Alteration of the differentiated, contractile phenotype of SMCs is known to play an integral role in the formation of atherosclerotic lesions. Although SMCs have previously been induced to accumulate cholesterol in vitro, for either in vitro or in vivo foam cell like SMC cells, there is little information about phenotypic changes at the protein or RNA level. We have characterized the phenotypic changes associated with chicken aortic cholesterol loaded SMCs formation at the protein and molecular level. The results of the present study support the SMC dedifferentiation in vitro model and increase our fundamental knowledge of plaque formation and remodeling. Diet cholesterol is a risk factor in the atherosclerotic process. Proliferation, apoptosis, migration and the ECM synthesis in SMC contribute to the development of the disease. Both, a cholesterol‐rich diet and exogenous cholesterol loading in vitro yield the overexpression of ECM genes, specifically collagen types I and II and fibronectin. This leads to the dedifferentiation of the SMC to a synthetic phenotype which is one of the main reasons of the vascular hypertrophy.