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Role of myofibrillogenesis regulator-1 in myocardial hypertrophy

¹Department of Pathophysiology, PLA General Hospital, and ²Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China

Submitted 15 March 2005 ; accepted in final form 4 August 2005

Myofibrillogenesis regulator-1 (MR-1) is a novel homologous gene, identified from a human skeletal muscle cDNA library, that interacts with contractile proteins and exists in human myocardial myofibrils. The present study investigated MR-1 protein expression in hypertrophied myocardium and MR-1 involvement in cardiac hypertrophy. Cardiac hypertrophy was induced by abdominal aortic stenosis (AAS) in Sprague-Dawley rats. Left ventricular (LV) hypertrophy was assessed by the ratio of LV wet weight to whole heart weight (LV/HW) or LV weight to body weight (LV/BW). Rat MR-1 (rMR-1) expression in the myocardium was detected by immunohistochemical and Western blotting analysis. Hypertrophy was induced by ANG II incubation in cultured neonatal rat cardiomyocytes. The effect of rMR-1 RNA interference on ANG II-induced hypertrophy was studied by transfection of cardiomyocytes with an RNA interference plasmid, pSi-1, which targets rMR-1. Hypertrophy in cardiomyocytes was assessed by [³H]Leu incorporation and myocyte size. rMR-1 protein expression in cardiomyocytes was detected by Western blotting. We found that AAS resulted in a significant increase in LV/HW and LV/BW: 89% and 86%, respectively (P < 0.01). Immunohistochemistry and Western blot analysis demonstrated upregulated rMR-1 protein expression in hypertrophic myocardium. ANG II induced a 24% increase in [³H]Leu incorporation and a 65.8% increase in cell size compared with control cardiomyocytes (P < 0.01), which was prevented by treatment with losartan, an angiotensin (AT₁) receptor inhibitor, or transfection with pSi-1. rMR-1 expression increased in ANG II-induced hypertrophied cardiomyocytes, and pSi-1 transfection abolished the upregulation. These findings suggest that MR-1 is associated with cardiac hypertrophy in rats in vivo and in vitro.

RNA interference; left ventricle; cardiac hypertrophy; cardiac remodeling

This article has been cited by other articles:

				H.-L. Li, Z.-G. She, T.-B. Li, A.-B. Wang, Q. Yang, Y.-S. Wei, Y.-G. Wang, and D.-P. Liu Overexpression of Myofibrillogenesis Regulator-1 Aggravates Cardiac Hypertrophy Induced by Angiotensin II in Mice Hypertension, June 1, 2007; 49(6): 1399 - 1408. [Abstract] [Full Text] [PDF]