With Masson’s trichrome staining, collagen fibers in both the left and right ventricular wall were noted in the perivascular zone and interstitial space, arranged chaotically and disorderly (Table 1). Thick and twisted dark-blue collagen fibers in the myocardial interstitial space formed complex anastomoses. A minimal degree of perivascular fibrosis was found in one animal, and a mild degree was found in two of the animals (Figure 7). Mild interstitial fibrosis was observed in all the animals in this group (Figure 7, Table 1).