CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 5, September/October 2022 230 AFRICA over-expression groups compared to that in the MI mice, and that of the sh-PRELP group was down-regulated compared to that in the MI mice. The Western blot and quantitative real-time PCR analysis also showed that the PRELP expression in the cardiac fibroblasts was increased post MI compared to the control cells. The PRELP expression in the cardiac fibroblasts was upregulated in the PRELP over-expression groups compared to that in the MI groups, and that of the sh-PRELP group was down-regulated compared to that in the MI groups. Echocardiography results showed that over-expression of PRELP reduced cardiac function following AMI, as assessed by the significantly decreased percentages of LVFS and LVEF, compared to the MI mice group. On the contrary, in the sh-PRELP groups, there was a significant increase in both LVFS and LVEF of the heart following AMI, compared to the MI mice group (Fig. 2A, B). The results indicate that PRELP can promote cardiac dysfunction following AMI. Over-expression of PRELP significantly increased the infarct size of the heart compared to the MI groups, and in the sh-PRELP groups, there was a significant decrease in infarct size of the heart following AMI, as assessed by TTC staining (Fig. 2C, 2D). These findings showed that PRELP increased adverse myocardial fibrosis and collagen deposition after AMI. HE and SR staining revealed a clear increase in infarct size, interstitial fibrotic area, and collagen accumulation in PRELP overexpression groups following MI. In contrast, in the sh-PRELP groups, there was a significant decrease in the infarct size and interstitial fibrotic area compared to the MI group and fibroblasts (Fig. 2E–G), indicating that PRELP can increase collagen deposition, promote adverse myocardial fibrosis and lead to ventricular re-modelling, which can cause heart failure post MI. Next, we investigated the effect of PRELP on activation of the wnt/β–catenin signalling pathway. As is already known, the downstream members of this pathway are β-catenin, GSK3β, MMP9, c-myc and TIMP-1. In our experiments, we used Western blotting and immunohistochemical staining analysis to Fig. 1. PRELP expression was upregulated in myocardial tissue and cardiac fibroblasts post MI. The PRELP protein levels in the myocardial tissues from mice were assessed using ELISA (A), Western blot (B and C) and immunohistochemical staining analysis (D). C. Quantification result from B. The PRELP protein levels in the fibroblasts were assessed using Western blot (E and F) and quantitative real-time PCR assays (G). F. Quantification result from E. *p < 0.05, **p < 0.01, ***p < 0.001 versus the control group; #p < 0.05; ##p < 0.01; ###p < 0.001 versus the MI group.
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