Effect of beta-amyloid Peptide on Fine Structure of Cardiac Myocytes in Culture

Sung, Eon Ki; Lee, Yoon Sik; Sung, Hoon Ki; Park, Jeong Hyun; Kim, Joo Young; Song, In Hwan; Lee, Yung Chang

Abstract

Several predetermined concentrations of beta-amyloid peptide, (betaA) were administered to the rat cardiac myocyte cultures for three days to determine the effects of betaA. Stainings with congo red and crystal violet were used to evaluate the deposition of betaA in the cardiac myocytes and MTT assay was used to elucidate the cytotoxic effects of betaA by anlaysis of cell viability. Beating rates and morphological changes were investigated with inverted microscope and TEM was used to study the fine structures. Administration of 0.5 microgram/ml of betaA to cardiac myocytes induced the reduction of beating rate, however, it did neither affect the viability nor fine structures. No significant differences in cell viability or fine structures were noted in the experimental groups which were exposed to 5 microgram/ml or higher concentration of betaA. Deposition of betaA was confirmed in the cytoplasm of betaA treated cardiac myocytes with congo red and crystal violet amyloid stains. The viability of cardiac myocytes exposed to betaA was found to be reduced significantly (19%) compared to control cultures with the MTT assay. Cardiac myocytes treated with betaA presented a reduced cytoplasmic area that appeared very condensed under inverted microscope. Mitochondrial abnormalities in betaA treated cardiac myocytes included their significant enlargement, vacuolization, disorganization or paucity of cristae, paracrystalline inclusion, and accumulation of amorphous material in mitochondrial space. Mitochondrial abnormalities were present sometimes in betaA treated cardiac myocytes without disorganization of myofibils or degeneration of other cell organelles. To understand the mechanism involved in amyloid deposit and its role in pathogenesis of the diseases such as Alzheimer and inclusion body myositis (IBM), a need for in vitro model is imperative. This model of betaA treated cultured cardiac myocytes represent a amyloidosis model, and it offers several advantages for future studies of betaA to help elucidate the pathogenesis of amyloid diseases. For example, cardiac myocytes can be easily accessible, and since cardiac myocytes can be cultured for quite a long time, it is possible to study morphological and physiological changes consequent to amyloid deposits.