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Peter Aldhous is Nature's chief News and Features editor.
The idea of therapeutic cloning, which offers the potential of growing replacement tissues perfectly matched to their recipients, is falling from favour. But there are alternatives, as Peter Aldhous found out.
Take two of the biological breakthroughs of the late 1990s and combine them to produce a medical miracle — that is the thinking behind therapeutic cloning. The achievements are the cloning technology that in February 1997 gave us Dolly the sheep1, and the successful creation the following year of cultures of human embryonic stem (ES) cells2. The promised miracle is the generation of 'personalized' replacement tissues to combat the ravages of ageing and disease. Genetically matched to the patient, these tissues would avoid the rejection problems that have always plagued transplant medicine.
ES cells come from blastocysts — tiny embryos, just a few days old, that consist of a hollow ball of cells. ES cells can develop into any type of cell, and so could be cultured to grow replacement tissues, such as cardiac muscle to graft onto a weakened...