Tag Archives: hESC

Human embryonic stem cells restore hearing in deaf gerbils

Ever since human embryonic stem cells (hESCs) were first cultivated by Dr. James Thompson at the University of Wisconsin, Madison in 1998, they have been at the centre of one of the most promising, and at times controversial, areas of modern medicine.  Recently hESCs have begun to live up to their early promise, as I discussed in a recent post on the launch of a clinical trial of hESC-dericed retinal cells in restoring vision in Stargart’s Macular Dystrophy.

Now a study from the University of Sheffield – published this week in the prestigious scientific journal Nature (1) – indicates that hESCs may be able to restore hearing as well as vision, by showing that auditory nerve cells derived from hESCs could restore hearing in deaf gerbils.  While this is not the first time that auditory nerve cells have been created from hESCs, it is the first time that it has been demonstrated that they can restore the connection between the sensory hair cells that convert sound vibration into electrical signals and the brain, and demonstrated improvements to hearing. A commentary in Nature News discusses the work led by Dr. Marcelo Rivolta:

Rivolta has spent the past decade developing ways to differentiate human embryonic stem cells into the two cell types that are essential for hearing: auditory neurons, and the inner-ear hair cells that translate sound into electrical signals.

He treated human embryonic stem cells with two types of fibroblast growth factor (FGF) — FGF3 and FGF10 — to produce two, visually distinct, groups of primordial sensory cell. Those that had characteristics similar to hair cells were dubbed otic epithelial progenitors (OEPs), and those that looked more like neurons were dubbed otic neural progenitors (ONPs).

His team then transplanted ONPs into the ears of gerbils that had been treated with ouabain, a chemical that damages auditory nerves, but not hair cells. Ten weeks after the procedure, some of the transplanted cells had grown projections that formed connections to the brain stem. Subsequent testing showed that many of the animals could hear much fainter sounds after transplantation, with an overall improvement in hearing of 46%”

Gerbils were used in this study rather than the more usual mice because they hear sounds in the same frequency range as humans, whereas the hearing of mice functions best at higher frequencies.

Human ESC derived optic nerve cells (yellow) repopulate the gerbil cochlea. Credit: Marcelo Rivolta, University of Sheffield.

You can read more about the work on the University of Sheffield website, where Dr. Rivolta has published a discussion of his groups work.

It will be some time before this approach can be evaluated in human trials, as further animal studies will need to be undertaken to both improve the efficiency of the procedure so that greater improvement to hearing results, and to demonstrate efficacy and safety over longer periods of time (this study lasted only 10 weeks). It is also clear that this technique will need to be adapted to address the different causes of deafness, for example deafness may be due to damage to sensory cells, or to the auditory nerve that passes the message to the brain, or to both.

Insertion of the stem cells into the cochlea will require surgery, and the techniques required for this in human patients will need to be developed over the coming years, but over 200,000 people worldwide have now been fitted with cochlear implants, so the technical challenges involved are not insurmountable.  Cochlear implants are used to restore hearing to many deaf people, but require a functioning auditory nerve, so hESC derived auditory neurons could be used alongside cochlear implants to restore hearing to many people who cannot currently benefit from these implants. Indeed the potential of combining cochlear implants with stem cell therapy was a major motivation for concentrating on the auditory nerve in this initial study, as Dr. Rivolta noted in a statement to ScienceNow:

Obviously the ultimate aim is to replace both cell types, but we already have cochlear implants to replace hair cells, so we decided the first priority was to start by targeting the neurons.”

There’s no doubt that this is an exciting piece of research in its own right, and of course another example of how the field of stem cell research is maturing, but what’s also been very refreshing is how Dr. Rivolta and his colleagues at the University of Sheffield have been will to discuss their use of animals in research with the press, with reports appearing in numerous outlets including the BBC, Guardian, ABC news, Times of India, Fox and  Montreal Gazette. It is further evidence – if any is still needed – that when scientists are open about their use of animals in biomedical research they will find that there are many journalists and news editors do understand the value of such work, but it is equally certain that in order to report animal research accurately journalists need scientists and scientific institutes to engage with them and provide the detailed information to inform their articles. The message to the scientific community could not be any clearer; if you wish the public to understand your work, take the time to explain it to them.

Paul Browne

1)      Chen W, Jongkamonwiwat N, Abbas L, Eshtan SJ, Johnson SL, Kuhn S, Milo M, Thurlow JK, Andrews PW, Marcotti W, Moore HD, Rivolta MN. “Restoration of auditory evoked responses by human ES-cell-derived otic progenitors.” Nature. 2012 Sep 12. doi: 10.1038/nature11415. [Epub ahead of print] Pubmed: 22972191

Animal research unleashes the power of human embryonic stem cells

For more than a decade now embryonic stem cell research has been one of the most high profile – and indeed controversial – areas of medical science, and it is an emerging field that owes a lot to animal studies performed by pioneers like Gail Martin of UCSF.

Recently the field has begun to live up to its promise with the announcement last year that the first patient had been enrolled in the first ever clinical trial of a human embryonic stem cells (hESCs), a trial that seeks to evaluate the safety of the hESC-derived oligodentrocyte progenitor cells in patients with spinal cord injury.  We discussed the role of animal research in the development of this therapy by Geron Corp in a post on this blog back in 2009.

In September of this year embryonic stem cells were in the news again with the announcement that clinical trials of retinal pigment epithelial cells (RPEs) derived from hESCs for the treatment of an inherited form of blindness known as Stargart’s Macular Dystrophy, are taking place at Moorfields Eye Hospital in London and the Jules Stein Eye Institute at UCLA. The development of this therapy was led by Professor Robert Lanza, Chief Scientific Officer at Advanced Cell Technology, and Adjunct Professor at Wake Forest University School of Medicine, and rests on animal studies which showed that RPE cells derived from hESCs were safe and could restore vision in rodent models of Stargart’s Macular Dystrophy, as a study publishes in the Journal Stem Cells in 2009 makes clear:

Assessments of safety and efficacy are crucial before human ESC (hESC) therapies can move into the clinic. Two important early potential hESC applications are the use of retinal pigment epithelium (RPE) for the treatment of age-related macular degeneration and Stargardt disease, an untreatable form of macular dystrophy that leads to early-onset blindness. Here we show long-term functional rescue using hESC-derived RPE in both the RCS rat and Elov14 mouse, which are animal models of retinal degeneration and Stargardt, respectively. Good Manufacturing Practice-compliant hESC-RPE survived subretinal transplantation in RCS rats for prolonged periods (>220 days). The cells sustained visual function and photoreceptor integrity in a dose-dependent fashion without teratoma formation or untoward pathological reactions. Near-normal functional measurements were recorded at >60 days survival in RCS rats. To further address safety concerns, a Good Laboratory Practice-compliant study was carried out in the NIH III immune-deficient mouse model. Long-term data (spanning the life of the animals) showed no gross or microscopic evidence of teratoma/tumor formation after subretinal hESC-RPE transplantation. These results suggest that hESCs could serve as a potentially safe and inexhaustible source of RPE for the efficacious treatment of a range of retinal degenerative diseases.”

Spinal Injury and Stargart’s Macular Dystrophy are only two of many diseases where hESC based treatments are offering hope of improvement, for more than a decade scientists have been investigating in animal models the use of embryonic stem cells to treat Parkinson’s disease, a degenerative disorder caused by the loss of nerve cells in the brain that produce the neurotransmitter dopamine and results in severe movement impairment. Now, a report in the Guardian newspaper describes how, after years of dedicated research, scientists have overcome a major of technical hurdle and paved the way for the evaluation of hESC therapy for Parkinson’s disease in human clinical trials. The Guardian report stresses the importance of studies in mice, rats and monkeys to evaluating the efficacy and safety of hESC-derived dopamine producing cells:

In a series of experiments, the team gave animals six injections of more than a million cells each, to parts of the brain affected by Parkinson’s. The neurons survived, formed new connections and restored lost movement in mouse, rat and monkey models of the disease, with no sign of tumour development. The improvement in monkeys was crucial, as the rodent brains required fewer working neurons to overcome their symptoms”

The study, which those with a subscription to Nature can read here, is very promising, and hopefully it won’t be very long until we are reading about the start of another clinical trial of hESC derived cells.

It is worth noting that despite fierce opposition from its opponents, public support for human embryonic stem cell research remains very high, a level of support that owes much to the willingness of scientists and research charities such as the Michael J. Fox Foundation for Parkinson’s Research to speak out in support of this important work.  While polls indicate that a clear majority of Americans support animal research, that majority could be larger, and the lesson from the stem cell debate is that the public are willing to listen to the arguments put forward by scientist. It is up to all of us who value animal research to do our bit to ensure that the majority in favor of animal research grows; after all, it can’t be right that more Americans support hESC medicine than support the animal research on which it depends!

Paul Browne

A new era for embryonic stem cells

As the new president takes office and the scientific community eagerly awaits the announcement of the reversal of the ban on federal funding of most research involving human embryonic stem cells (hESC’s), there’s news that the FDA has approved the first ever trial of a treatment based on hESC’s for severe spinal cord injury.

This is a very welcome development; for a decade now hopes have been raised about the potential for hESC’s to treat a range of serious illnesses, particularly brain and spinal injuries,  but despite excellent work by organizations such as the Christopher and Dana Reeve Foundation no treatments have yet reached clinical trials in patients.  This is not a criticism of hESC’s, underneath the hype is the reality that hESC research is a very new science. After all the first hESC’s were produced by Professor James Thomson and colleagues at the University of Wisconsin-Madison a mere ten years ago, and a lot of work has been necessary to ensure that hESC therapies are safe and effective enough to justify human trials.

The treatment developed by Geron uses a type of cell known as an oligodendrocyte progenitor cell (OPC) that was derived by growing  hESC’s  under carefully controlled conditions. OPC’s  in their turn develop into oligodendrocytes, cells that forms a sheath around the nerve cells and are vital to the proper function of the nervous system.  In rat studies the scientists at Geron showed that OPC treatment could restore the ability to move after severe spinal injury.  Subsequent safety studies in rodents indicated that the injected cells remained within the nervous system and did not produce teratomas, a type of tumour produced by stem cells that have not been adequately processed to ensure they have differentiated into a more mature cell type suitable for transplantation. An important observation made during Geron’s animal studies of OPC therapy was that the therapy worked when the cells were injected 7 days after injury but not when treatment was delayed until 10 months after injury (1) indication that early treatment was vital, and leading to the decision to treat patients 7-14 days after injury in this phase I clinical trial.

If you take a look through the Geron and Christopher and Dana Reeve Foundation websites you will see that there are many other hESC based treatments under development, and appreciate the undeniable importance of animal research to this work. With a new president who appreciates the importance of hESC research we will no doubt see more announcements of this sort, but it’s also worth remembering that animal research is crucial to other types of stem cell research, including the iPS approach we’ve discussed here and other methods we discussed earlier this week on our sister blog in the UK.

Could this be the dawn of a new era in medicine?

Update 21 February 2011: After being put on hold for over a year due to potential problems with cyst formation identified in an animal study, additional animal studies have proved reassuring and the FDA gave its approval for the trial to go ahead. Geron recently announced the enrollment of  the first patient into their phase I study of hESC based therapy for spinal injury.

Regards

Paul Browne

1) Keirstead H.S. et al. “Human embryonic stem cell-derived oligodendrocyte progenitor cell transplants remyelinate and restore locomotion after spinal cord injury” J Neurosci., Volume 25(19), Pages 4694-4705 (2005) doi:10.1523/JNEUROSCI.0311-05.

2005