The Role Of Smydl In Cardiomyocyte Hypertrophy

Cardiac hypertrophy is an accumulation of heart disease. It’s the general reaction of myocardium, which occurs in different cardiovascular diseases, such as hypertension, myocardial infarction, atrioventricular valve diseases, as well as different cardiac disease caused by genes, viruses, or metabolic disease. Up to 50% of patients with cardiac hypertrophy will lead to death within 5 years due to heart failure. Despite progress has been made in decades of research on cardiac hypertrophy, the molecular mechanism remains to be elucidated.To elucidate the molecular mechanisms of cardiac hypertrophy, our laboratory cloned a human heart-and muscle-specific expression gene Smydl (also known as muscle-specific genes Bop) and found that the gene might be related to cardiac hypertrophy. This research continues to study the role of Smydl in cardiomyocyte hypertrophy. First, the expression pattern of Smydl protein in adult mouse is analyzed by Western blot. The results show that Smydl protein abundantly expresses in heart tissue. Second, it is confirmed that pathologic cardiac hypertrophic mice (BALBc) were obtained by injecting isoprenaline. We extracted RNA and protein for further analyses by RT-PCR and Western blot and the results show that Smydl is up-regulated, like cardiac hypertrophic markers, includingβ-MHC, SK-a-actin and ANF in cardiac hypertrophic mice. We established the physiological cardiac hypertrophy mouse model by training mice to swim. The results show that there is no obvious difference for Smydl expression in mice between the physiological hypertrophy mice heart and normal controls. We obtained the result that Smydl is up-regulated in RNA level in primary cardiomyocytes of neonatal rat stimulated by FBS. All these results support the idea that Smydl may play an important role in regulation of pathologic cardiac hypertrophy but not in regulation of physiological cardiac hypertrophy.Meanwhile, H9C2 cells derived from rat cadiocyte were transiently transfected with the Smyd1 constructs to obtain Smyd1-overexpressing cells line and Smyd1-RNAi cell lines for further studies on the molecular mechanism. Western blots are performed on proteins extracted from Smydl-overexpressing H9C2 cells line to detect the expression of Smydl and hypertrophic marker genes, ANF, (3-MHC and SK-a-actin. Apparently, the protein expression of Smydl is up-regulated and the same for hypertrophic cardiac genes in Smydl-overexpressing H9C2 cells line, but the protein expression of Smydl is down-regulated in Smydl-RNAi cell lines. This result reveals that Smydl can be involved in cardiomyocyte hypertrophy.Finally, we use a set of pathological hypertrophic cardiomyopathy patients heart samples to analysis whether Smyd1 is related to pathological myocardial hypertrophy. Western results show that Smyd1 protein is also up-regulated in the heart tissueses of the patients with pathological hypertrophic cardiomyopathy that is the same as those observed with mouse model and cells. These results indicate that Smyd1 is involved both in cardiac hypertrophy of mice and in the human heart. These results provide a basis for further studying the mechanism of cardiac hypertrophy.