Inhibition of APC anticoagulant activity with MAPC1591 reduces joint bleed–induced chondrocyte apoptosis in hemophilia A mice. FVIII^−/− mice were administered with control IgG, MPC1609, or MAPC1591 (1 mg/kg, ip). Twenty-four hours later, joint bleeding was induced by a needle puncture. Fourteen days following the injury, the knee joint was excised, sectioned, and stained with TUNEL. Red staining of chondrocytes, pointed out by arrows, indicates apoptotic chondrocytes. Top panel images were captured at ×4 magnification. The squared area was imaged at ×60 magnification (bottom panel). (B) The number of apoptotic chondrocytes was counted per high magnification field and quantified. The data shown are ± SEM. ns, not statistically significant difference. **P < .01; ****P < .0001.