HSV-1 R7020 mutant blocks flow and mechanically induced apoptosis. Immunohistochemical analysis of the left CCA at 3 days in sham (a, d, and g), control (b, e, and h), and HSV-1 R7020-treated (c, f, and i) groups. Detection of apoptosis was performed by TUNEL assay (a–c) using the VasoTACS in situ apoptosis detection kit per the manufacturer's instructions. Detection of cleaved caspase 3 (d–f), one of the key executioners of apoptosis, was performed by using a SignalStain IHC detection kit. Cell proliferation was assessed by PCNA staining (g–i).