Time-dependent organic changes of intravenous thrombi in stasis-induced deep vein thrombosis model and its application to thrombus age determination

Using histochemical and immunohistochemical techniques, we examined the intrathrombotic collagen contents and the appearance of hemosiderin-positive cells, neovessels, and myofibroblasts in a stasis-induced venous thrombosis model. The intrathrombotic collagen deposition area occupied about 20% at 5 days, and exceeded 80% at 21 days after ligation of the inferior vena cava (IVC). Hemosiderin-positive cells in the thrombus first appeared at 3 days in only one of the five samples, and positive cells were constantly detected in all thrombi at 5 days or later. CD31-positive neovessels in the thrombus first appeared at 5 days in one of five samples and were detected in all samples after 10 days. At 7 days, αSMA-positive myofibroblasts at the periphery of the thrombus first appeared in three of five samples, and were detected and enhanced time-dependently in all samples after 10 days. These observations demonstrated that these markers would be applicable for thrombus age determination.