Platelet TGF-β1 contributes to VEC-mesenchymal transition. (A) Whole-mount aortic valve staining with isolectinB4 (green), vimentin (red), α-SMA (gray), and DAPI (blue) in littermate TGF-β1^flox-LDLR control mice (top) and TGF-β1^platelet-KO-LDLR mice (lower) at 6 months on HFD. (B) Higher-magnification images showing colocalization (yellow arrows) of isolectinB4, vimentin, and α-SMA in aortic valves from the 2 groups of mice. Quantification of α-SMA–positive area fraction in whole-mount images of aortic valves from TGF-β1^flox-LDLR control mice and TGF-β1^platelet-KO-LDLR mice after 6 months on HFD (right).