Fig. 1. Increased collagen deposition in the myocardium of human METH-user heart autopsy tissue.

a Picro Sirius Red (PSR) staining was conducted in non-METH and METH user human LV heart sections to assess the extent of collagen deposition. Formalin-fixed, paraffin-embedded LV sections (5 µm) from non-METH (n = 7), and METH users (n = 34) were stained with PSR. The METH user group consists of heart samples from patients who died from acute METH intoxication/overdose and patients positive for METH following toxicology studies carried out in the case of accidental causes of death. Representative images shown in the left panel images demonstrate collagen deposition (in red) in the perivascular region. Those in the right panel images demonstrate the extent of collagen deposition (in red) in the interstitial spaces in the same non-METH and METH users heart tissue. Scale bar: 100 µm. b Dot plot represents individual values of quantified percent collagen content in PSR-stained LV sections from the non-METH (n = 7) and METH (n = 34) user groups. The collagen content (red-stained area) relative to the total area of the myocardium was measured in 10–15 high-magnification microscopic fields (×10) for each heart section and averaged for analysis. P values were determined between non-METH and METH groups by constructing multiple linear regression analysis with models adjusted for age, sex, race, heart weight, body weight, height, and body mass index. Data are expressed as mean ± SEM. A P < 0.05 between groups was considered statistically significant. c–e Heart weight c, age d, and body mass index (BMI) e data were tested for normality by analysis using the Kolmogorov–Smirnov test followed by the Kruskal–Wallis test for P value determination. Boxes depict interquartile ranges, lines represent medians, and whiskers represent ranges. P < 0.05 between groups was considered statistically significant. NS not significant.