Inhibition of fibrinolysis with TXA attenuates fibrin clot retraction in vivo. Fibrin-dependent clot retraction was visualized over 120 minutes in vivo, in the absence or presence of TXA, as described in “Methods.” (A) Confocal maximum-intensity projection of platelets (Dylight 649 anti-mouse GP1bα antibody; red) and fibrin (Alexa Fluor 546 anti-fibrin antibody; white) within the same thrombus after 20 minutes (left column) or 120 minutes (middle column) in the absence/presence of TXA. The right column depicts the size of the fibrin network after 20 and 120 minutes. The direction of blood flow (arrow) and a scale bar (20 μm) are shown. (B) Collated quantification of the decrease in fibrin network size (red bars; left y-axis) and increase in fibrin amount (blue bars; right y-axis) over 120 minutes of thrombus maturation, with data expressed as a percentage change from the fibrin size/amount at 5 minutes. Results depict the mean ± SEM (saline control, n = 7; TXA, n = 4), where **P < .01 by the unpaired 2-tailed Student t test.