Cryopreserved heart valve allografts can have a normal endothelium.

@article{Mohan1994CryopreservedHV,
  title={Cryopreserved heart valve allografts can have a normal endothelium.},
  author={Rajeev Mohan and Xiangfen Feng and Paul J Walter and Arnold G. Herman},
  journal={The Journal of thoracic and cardiovascular surgery},
  year={1994},
  volume={108 5},
  pages={985-8}
}