Impairment of myocardial mitochondria in viral myocardial disease and its reflective window in peripheral cells

Abstract

Background: Viral myocardial disease (VMD) is a common disease inducing heart failure. It has not been clear the roles of mitochondrial damage in the pathological changes of cardiomyocytes in VMD.

Methods: Myocardial tissues and lymphocytes were collected from 83 VMD patients. Control groups included 12 cases of healthy accidental death with myocardial autopsy and 23 healthy blood donors. The mouse model of viral myocarditis (VMC) was established by Coxsackie virus B3 infection and myocardial tissues and skeletal muscle were collected. Mitochondrial DNA (mtDNA) deletion rate was quantitatively determined using polymerase chain reaction.

Results: There was significantly difference of myocardial mitochondrial DNA deletion rate between VMD or VMC group and control group (P<0.05). Moreover, the loss of mitochondrial membrane phospholipids was significantly different between VMD or VMC group and control group. In VMC mice, there were negative correlations between myocardial mtDNA3867 deletion rate and left ventricular peak systolic pressure (LVPSP) (r = -0.66, P<0.05), and between myocardial mtDNA3867 deletion rate and +dp/dtmax (r = -0.79, P<0.05), while there was positive correlation between myocardial mtDNA3867 deletion rate and -dp/dtmax (r = 0.80, P<0.05).

Conclusion: Mitochondrial damage is an important pathophysiological mechanism leading to myocardial injury and cardiac dysfunction. The mitochondrial damage in the skeletal muscle and lymphocytes reflect a "window" of myocardial mitochondrial damage.

Figure 1. The correlation curve of summation mtDNA deletion rate between myocardium and lymphocytes in VMD patients.

Figure 2. PCR result of myocardial mtDNA in VMC mice.

Lane 1: myocardial mtDNA of 3 days after viral injection; lane 2: myocardial mtDNA of 11 days after viral injection; lane 3: myocardial mtDNA of 24 days after viral injection; lane 4: myocardial mtDNA of control mouse. M: DNA marker; N: negative control.

Figure 3. The correlation curves of mtDNA deletion rate between myocardium and skeletal muscle, and mitochondrial membrane phospholipids loss rate between myocardium and skeletal muscle in VMC mice.

The correlation of mitochondrial membrane phospholipids normal localization between myocardium and skeletal muscle in VMC mice was described in part b, R = 0.959, p<0.001; the correlation of partial loss of mitochondrial membrane phospholipids was described in part c, R = 0.886, p = 0.03; the correlation of most or complete loss was described in part d, R = 0.951, p = 0.001.

Figure 4. The structure of lymphocytes in control group (a) and VMD patients showing swelling of mitochondria and deletion mitochondrial membrane phospholipids (b, c, d).

(magnification 10,000X).

Figure 5. The structure of mitochondria in cardiomyocyte of VMC mice (magnification 10,000X).

(a) Cardiomyocyte of normal mouse. The mitochondria were circle or elliptical with legible and densely packed cristae. There were also sporadic glycogen granules between the myofibrils. (b) Cardiomyocyte of mice 3 days after virus infection. The mitochondria proliferated and swelled, with pyknosis, vesicle and the decreased matrix; glycogen granule decreased or disappeared. (c) Cardiomyocyte of mice 11 days after virus infection. The mitochondria proliferated and swelled, with the fusion of mitochondrial membrane and merged to huge mitochondria; glycogen granule decreased; inhomogeneous myofibril dissolved, and the sarcomere disappeared. (d) Cardiomyocyte of mice 24 days after virus infection. The mitochondria significantly proliferated and swelled, the cristae became vague; glycogen granule decreased, and sarcoplasmic reticulum dilated.

Figure 6. The structure of mitochondria in skeletal muscle of VMC mice (magnification 10,000×).

(a) Skeletal muscle of normal mouse. The mitochondria were circle or elliptical with legible and densely packed cristae. There were also abundant glycogen granule, legible sarcoplasmic reticulum and T tube near Z line. (b) Skeletal muscle in mice 3 days after virus infection. The mitochondria swelled, the number of mitochondrial cristae decreased or disappeared, sarcoplasmic reticulum dilated, and glycogen granule decreased. (c) Skeletal muscle in mice 11 days after virus infection. The mitochondria proliferated and swelled; glycogen granule decreased. (d) Skeletal muscle in mice 24 days after virus infection. The mitochondria proliferated and swelled; sarcoplasmic reticulum dilated.