The application of autophagy to thrombus age estimation in murine deep vein thrombosis model

We immunohistochemically examined the intrathrombotic dynamics of autophagy during thrombogenesis using murine deep vein thrombosis (DVT) models. To perform the immunohistochemical analyses, we used anti-LC3 antibody and anti-p62 antibody for detecting the intrathrombotic autophagic functions. We estimated dynamics of the intrathrombotic autophagy as LC3⁺ cell number (×1000, five fields) with the thrombus ages (each group n = 5). The number of LC3⁺ cells was once decreased at 3 days, and then increased until 10 days. On the contrary, the number of p62⁺ cells progressively increased until 10 days after the inferior vena cava (IVC) ligation, and then gradually decreased. Especially, in all of thrombus samples with the postligation intervals of 5-10 days, both numbers were larger than 10. Subsequently, we compared the number of LC3⁺ cells to that of p62⁺ cells. Although, at 1 day after the IVC ligation, LC3⁺ cell number significantly exceeded p62⁺ cell number, the former was significantly or relatively less than the latter at 3 days or more after the IVC ligation. Thus, positive cells of > 10 in both LC3 and p62 indicated the thrombus age of 5-10 days. Upon comparison of immunopositive cells in LC3 and p62, the p62/LC3 ratio was > 1.0 in 29 out of 30 thrombus samples aged 3-21 days, and all of 1-day-old thrombus had the p62/LC3 ratio of < 0.5. Thus, the ratio of > 1.0 and that of < 0.5 could indicate thrombus age of 3 days or more and that of 1 day, respectively. Collectively, our study implied that the detection of autophagy-related molecules such as LC3 and p62 would be useful for the determination of thrombus age.