Phenotype modulation in primary cultures of aortic smooth muscle cells from streptozotocin-diabetic rats

Differentiation. 1998 Aug;63(4):225-36. doi: 10.1111/j.1432-0436.1998.00225.x.

Abstract

Diabetes mellitus is a major risk factor for atherosclerosis. In atherosclerotic lesions, arterial smooth muscle cells (SMC) change from a contractile to a synthetic phenotype characterized by active proliferation. A similar phenotype modulation occurs in vitro when isolated arterial SMC are grown in culture and is characterized by both changes in cell morphology and a typical switch in actin isoform expression. In this study, we examined the influence of streptozotocin (STZ)-induced diabetes on the differentiation state and the phenotype modulation of cultured rat aortic SMC. We used transmission electron microscopy to study the fine structure of STZ-diabetic and non-diabetic SMC in primary culture and immunological methods for the determination of the proportions of alpha-smooth muscle actin (alpha-SM) and nonmuscle beta-actin (beta-NM) isoforms. Cultured STZ-diabetic SMC exhibited a large cytoplasmic volume, rich in rough endoplasmic reticulum, when compared with cultured non-diabetic SMC. alpha-SM, organized in stress fibers, was less homogeneously and abundantly distributed and by contrast, beta-NM was more abundant in STZ-diabetic than in non-diabetic SMC. Cytofluorimetric analyses demonstrated that the alpha-SM content was reduced in freshly STZ-diabetic SMC. Furthermore, during logarithmic growth of cultured SMC, the decrease of alpha-SM was more important in STZ-diabetic than in non-diabetic SMC. Immunoblotting of actin isoforms confirmed that expression of beta-NM was more important in STZ-diabetic than in non-diabetic SMC even in freshly isolated cells. The results suggest that SMC from STZ-diabetic rats express a more dedifferentiated state and undergo a more rapid phenotypic modulation in primary cultures than SMC from non-diabetic rats. Therefore, diabetes could induce changes in the phenotype of arterial SMC which might be associated with the onset or progression of the atherogenic process.

MeSH terms

  • Actins / analysis
  • Actins / biosynthesis
  • Animals
  • Aorta, Thoracic / cytology
  • Aorta, Thoracic / pathology*
  • Aorta, Thoracic / ultrastructure
  • Cell Differentiation
  • Cell Division
  • Cells, Cultured
  • Diabetes Mellitus, Experimental / pathology*
  • Flow Cytometry
  • Kinetics
  • Male
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / pathology*
  • Muscle, Smooth, Vascular / ultrastructure
  • Phenotype
  • Rats
  • Rats, Wistar
  • Reference Values
  • Time Factors

Substances

  • Actins