| Stress cardiomyopathy is a cardiac syndrome precipitated mainly by the effect of intense emotional stress on the heart. It has been listed as a possible cause of sudden death. Stress cardiomyopathy has also been known as'takotsubo cardiomyopathy','broken-heart syndrome','left ventricular apical ballooning'. Diagnosing this cardiac syndrome in the clinical setting relies on ischemic changes on the ECG, elevated blood levels of catecholamines, left ventricular ballooning on ultrasound, a prior history of stressful events and normal coronaries. However, cases of sudden death often occur outside hospital settings and these present a challenge to forensic pathologists who rely mostly on case history, gross autopsy findings and histomorphological changes to assess such cases. The markers and parameters used in the clinical settings for diagnosing stress cardiomyopathy may not be completely useful in postmortem investigations. Hence, there is a need to find other markers which are involved in both stress reaction and cardiomyopathies and which can be easily analyzed from heart tissue postmortem.In this study, a rat model of stress cardiomyopathy was designed as previously described by other researchers. Histological examination of heart tissue was performed; immunofluorescence staining followed by computer-image analysis was used to assess the distribution and levels of Neuropeptide Y (NPY) released in the hearts and semi-quantitative RT-PCR analysis was used to investigate the expression of peroxisome proliferator-activated receptorγcoactivator-1α(PGC-1α) mRNA. The changes in expression of these two molecules may prove useful to determine the presence of stress-induced cardiomyopathy and this study may provide a basis for further research dealing with the pathomechanism of this cardiac syndrome.ObjectivesReproduce the typical histopathological findings of stress-induced cardiomyopathy and investigate the expression of Neuropeptide Y and PGC-1αmRNA in the heart tissue of rats .Methods30 male Sprague-Drowley rats (~250g mean body weight) were used in this experiment. The rats were randomly distributed into two groups, stress-test group and control group. Psychological stressors were applied to the rats daily as: immobilization into aerated glass box for 30 minutes, followed by electric foot shock (2mA) through a cage fitted with metallic grid floor (model DTT-2?, China). Electric foot shock was given for 10s each time with a lapse of 2min in between and this stress stimuli lasted for 30 minutes. Rats were sacrificed by decapitation at the end of fifteen days and twenty-five days respectively, 10 rats from stress-test group and 5 from control group on each days.The hearts were removed, washed and placed in either formaldehyde solution or frozen in liquid nitrogen and kept at -70℃. Hematoxylin and eosin staining (H&E) was performed on slices of the rats'hearts. Immunofluoro- histochemistry was applied to visualize NPY and quantification was done by computer software analysis (Image Pro Plus?). Semi-quantitative reverse transcriptase polymerase chain reaction analysis (RT-PCR) was used to analyse the expression of PGC-1αmRNA expression the rats heart. Hearts measurements were also taken.ResultsHistological findings was consistent with the presence of stress cardiomyopathy in the test group including contraction band necrosis, inflammatory cell infiltrates, interstitial and focal myocardial fibrosis. Contraction band necrosis was more pronounced in the hearts removed on day 25 compared with those removed on day 15. On both days, significantly higher levels of expression of NPY and PGC-1αmRNA was observed in the stressed rats compared with the controls. Comparing the two stress-test groups, a higher level of NPY was observed after 25 days of stress stimuli, but no statistically significant difference was found for PGC-1αmRNA expression ( P<0.01 for NPY, P > 0.05 for PGC-1α).ConclusionThe histological findings confirm the pathomorphological hallmark of stress cardiomyopathy.The results suggest that NPY and PGC-1αare overexpressed in chronic stress-induced cardiomyopathy in rats as compared with normal non-stressed subjects..These molecules could be applied to cases of human stress cardiomyopathy to confirm if they can be used as markers of this cardiac syndrome postmortem.
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