Gene-editing technology has been used to restore partial vision to blind rats, paving the way for revolutionary new treatments that alter DNA in damaged parts of the body.
It is the first time scientists have precisely modified DNA in non-dividing cells of the sort that make up most adult organs and tissues.
Until now the pioneering gene-editing technique known as Crispr-Cas9 has been most effective in dividing cells such as those in the skin or gut.
The US team targeted a natural repair pathway in cells called NHEJ (non-homologous end-joining) that re-joins strands of broken DNA.
This process was paired with gene-editing technology to swap out a section of DNA in the eyes of three-week-old rats affected by retinitis pigmentosa (RP), an inherited condition that causes blindness in humans.
The replacement DNA provided a functional copy of Mertk, one of the genes damaged in RP.
Tests conducted when the rats were eight weeks old showed they were able to respond to light and their retinal cells were healing.
Lead scientist Professor Juan Carlos Izpisua Belmonte, from the Salk Institute in La Jolla, California, said: "We are very excited by the technology we discovered because it's something that could not be done before.
"For the first time, we can enter into cells that do not divide and modify the DNA at will. The possible applications of this discovery are vast.
"We now have the technology that allows us to modify the DNA of non-dividing cells, to fix broken genes in the brain, heart and liver. It allows us for the first time to be able to dream of curing diseases that we couldn't before."
The research is reported in the latest edition of the journal Nature.
British expert Professor Robert McLaren, from Oxford University, said: "This is a significant advance.
"Retinitis pigmentosa (RP) is a genetic disease that causes blindness - it affects about one in 4,000 people in the UK. In this study, the researchers used a bacterial protein to cut and repair defective DNA in a rat that has retinitis pigmentosa.
"Clinical trials are a long way off because the Crisper proteins may cut DNA at other sites that may have untoward effects.
"Nevertheless, since ageing is defined as picking up DNA mutations, the ability to correct these mutations may in future provide us with a means of extending our lifespan as well as treating many diseases that relate to ageing."