A decision by one of the biggest names in stem cell research to throw in the towel will not stop other pioneering work that could yet produce cures for blindness and help mend broken hearts.
Scientists were shocked by U.S. biotech company Geron Corp's decision on Monday to quit embryonic stem cell research -- a move it blamed on a lack of money and the complexities of getting regulatory approval.
Yet, at the same time, teams working with adult stem cells -- a less ambitious area -- are making good progress.
This is not the end of an era, said Dusko Ilic, senior lecturer in stem cell science at King's College London.
Shortly before Geron told the world it was ending further development of its embryonic stem cell projects, Australia's Mesoblast Ltd reported its adult stem treatment slashed the rate of further heart problems in heart failure patients.
It's a tale of two ends of the market. I believe the adult stem cell space was always more attractive anyway, said Navid Malik, a biotechnology analyst at Merchant Securities.
Stem cells potentially offer a new way of treating diseases for which there are currently no treatments -- including heart disease, Parkinson's and stroke -- by regenerating tissue.
Embryonic stem cells are harvested from embryos and have the potential to become almost any type of tissue. Adult stem cells are less controversial, but are also less flexible.
Like Malik, scientists agreed Geron had started in a difficult place in testing economic times.
In its most advanced project, Geron was testing an embryonic stem cell treatment aimed at helping patients with spinal cord injuries like the late Superman actor Christopher Reeves, who was paralysed in a horse-riding accident.
Making superman walk would have been great for business but was an ambitious target for a serious problem and maybe not the best start scientifically or clinically for stem cell therapies, said Alison Murdoch, head of the fertility centre at Britain's Newcastle University.
The first patient was treated in October 2010 with Geron's product called GRNOPC1, containing cells that had been manipulated to become precursors to nerve cells.
Other research teams are focussing on eye disorders such as age-related macular degeneration (AMD) or on ways to repair damaged heart tissue -- areas where experts say progress and, crucially, return on investment is likely to be quicker.
Pfizer Inc, for example, is working with University College of London's Institute of Ophthalmology on an embryonic stem cell treatment for AMD and is now awaiting a green light to commence clinical trials in Britain.
Advanced Cell Technology (ACT) is starting early-stage human trials in the United States and Britain using embryonic stem cells in patients with a progressive form of blindness called Stargardt's macular dystrophy.
Getting the business case right is as important as getting the science right for each stem cell therapy that we develop, said Anthony Hollander, a professor of Rheumatology and Tissue Engineering at the University of Bristol.
The ethical controversy surrounding embryonic stem cells can also have hard commercial implications, as highlighted by a ruling from Europe's top court last month that has left the business case for embryonic stem cells in limbo.
The European Court of Justice decided to ban the patenting of any stem-cell process that involves destroying a human embryo, in a move described by scientists as a major blow to the emerging field of research.
That court decision will have given pause for companies looking into embryonic stem cells but it will not affect adult stem cells derived from bone marrow, fat or skin.
The adult stem cell space is moving forward very fast, said Malik. We're going to see filings for regulatory approval in the next three to five years for a series of products.
Robert Lanza, chief scientific officer of ACT, is not giving up hope on the embryonic front but said Geron's exit put more pressure on his firm to succeed.
Of course, it's the second mouse that often gets the cheese, he said.
(Additional reporting by Julie Steenhuysen in Chicago; Editing by David Cowell)