The procedure was performed by Dr. Charles Vacanti at the University of Massachusetts in 1997, to demonstrate a method of creating cartilage structures for transplantation into human patients. The cartilage cells used in the Vacanti mouse came from a cow, but a patient's own cartilage cells could be used in the same way, to produce a replacement ear or other cartilage part that could be transplanted without risk of rejection by the patient's immune system. The Mouse itself had suffered from a genetic mutation which, apart from causing baldness, inhibited the mouse's immune system, preventing a transplant rejection.
The first photos of the mouse were released in a 1997 journal, Plastic and Reconstructive Surgery. Sometimes colloquially referred to as the "earmouse" was quickly seized upon by animal rights and advocacy groups and anti-genetics groups to protest the use of the mouse for the experiment. Then in the October 11, 1999 New York Times, the anti-genetics group, Turning Point Project, placed a full page ad and used this picture with an inaccurate caption which read, "This is an actual photo of a genetically engineered mouse with a human ear on its back". In truth, the genes of the mouse were never altered. The mold for the ear was implanted beneath the skin of the mouse and cartilage was made to grow on the mold.
The photo of the mouse was passed around the internet, mainly via email, sometimes with little to no text accompanying it leading many people to speculate whether the photo was real.