Historically, tissue transplantation, especially of refrigerated tissue (after Filatov). It was theorized that nonspecific substances, capable of initiating restorative processes, formed in tissues when refrigerated. Cell therapy (after Niehans) refers to implantation of tissue by injection. Originally this involved fresh cells but later frozen or lyophilized cells
Cell Engineering -- standards : Navigating the manufacturing process and ensuring the quality of regenerative medicine therapies : proceedings of a workshop / Ariel Markowitz-Shulman, Sioghan Addie, Meredith Hackmann, Joe Alper, and Sarah H. Beachy, rapporteurs ; Forum on Regenerative Medicine, Board on Health Sciences Policy, Health and Medicine Division, the National Academies of Sciences, Engineering, Medicine
