Tag Archives: Embryonic stem cell

Reprogrammed frog and mouse cells win the 2012 Nobel Prize

This morning the Nobel Assembly announced that the 2012 Nobel Prize in Physiology or Medicine will be shared by John B. Gurdon and Shinya Yamanaka for their “discovery that mature cells can be reprogrammed to become pluripotent”.  Animal research played a key role in the research honoured by the prize, specifically the studies of frogs undertaken by Professor Gurdon and studies of mice performed by Professor Yamanaka.

Sir John Gurdon. Image: Nobel foundation.

Professor Gurdon’s key work showed in a series of studies undertaken at the University of Oxford in the late 1950’s and 1960’s that if the nucleus of a specialised cell from a frog of the species Xenopus laevis - initially from late embryonic cells and subsequently adult intestinal and skin cells – was transferred into an egg whose nucleus had been removed, it could give rise to normal frog that could themselves produce offspring. This demonstrated for the first time that the nucleus of an adult cell is totipotent, and that in under certain conditions it could give rise to all cell types, including eggs and sperm, that are required in a healthy adult.

The very first Xenopus frog produced by somatic nuclear transfer to reach sexual maturity. Image: J.B. Gurdon

In 2009 Sir John wrote an account of his research on nuclear transfer in Xenopus for Nature Medicine, which can be read online without subscription, after he and Professor Yamanaka were presented with the  Albert Lasker Basic Medical Research Award in 2009.

Professor Shinya Yamanaka. Image: Nobel foundation

Almost 4 decades later Professor Yamanaka, then at the Kyoto University Institute for Frontier Medical Sciences, made another great step forward by proving that it was possible to transform adult mouse cells into a pluripotent stem cells without nuclear transfer. By inserting 4 genes whose expression is associated with the embryonic state into the adult cell, his team were able to create the first induced pluripotent stem (iPS) cells, cells that could give rise to any tissue in the body.

Earlier this year in a post congratulating Professor Yamanaka’s on winning the 2012 Millenium Technology Prize I noted that:

The work briefly described above was a technological tour-de-force where Prof. Yamanaka and his colleagues selected 24 genes which had previously been identified as having key roles in mouse embryonic stem cells, and developed a screening method using skin fibroblast cells derived from mice that had be genetically modified with an antibiotic resistance gene that was only expressed in embryonic cells, so that only cells that were in an embryonic state would survive in a culture containing the antibiotic. Different combinations of these 24 genes were screened for their ability to induce to the production of colonies of embryonic -like cells from adult fibroblasts.  They eventually identified just 4 genes – Oct3/, Sox2, Klf4 and c-Myc – that together could reprogram adult mouse fibroblast cells to a pluripotent embryonic-like state (1), and subsequently demonstrated that these iPS cells could give rise to a wide variety of  tissue types when incorporated into mice, either by subcutaneous injection into adult mice or incorporation into early mouse embryos. By modifying their method slightly to also include expression of an important developmental gene named Nanog  they were then able to generate chimeric mice (mice whose tissues are made up of a mixture of cells derived from their own embryonic stem cells, and cells derived from iPS cells) which were capable of transmitting the iPS cells to the next generation of mice (2).

Soon after this Prof. Yamanaka succeeded in generating iPS cells from human fibroblasts, using the same techniques used for the mouse cells, and a whole new and exciting field of biomedical research was born.

1)      Takahashi K, Yamanaka S. “Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors.” Cell 2006 Vol. 126(4):663-76. PubMed: 16904174

2)      Okita K., Ichisaka T., Yamanaka S. “Generation of germline-competent induced pluripotent stem cells.” Nature Vol. 448:313-317 (2007). PubMed:17554338””

It’s worth remembering that this breakthrough did not come out of thin air, and built on years of research that followed the pioneering work of Martin Evans and Gail Martin who demonstrated that cells derived from mouse embryos could be cultured and give rise to all tissue types…the first embryonic stem cells.

The field of iPS cell research has progressed swiftly since the first mouse iPS cells were produced just 6 years ago, and the techniques used to produce the cells have been refined to address early concerns that the inserted genes might give rise to tumors, but as Prof Yamanaka outlined in a recent review of progress in the field there is still a lot of scope for improvement.  Nevertheless iPS cells are already showing promise in a variety of medical research applications – for example to create nerve cell lines from Parkinson’s disease patients in order to study the processes that trigger the degeneration, or  to evaluate the toxicity of new drugs – and are expected to join  human embryonic stem cells as key components of regenerative medicine.

This year’s Nobel Prize in Physiology or Medicine highlights once again the key role played by animal research in making groundbreaking discoveries that give rise to new fields of medicine, and we offer our heart-felt congratulations to John Gurdon and Shinya Yamanaka.

 

Addendum: In a statement to Reuters on the problem of the unproven stem cell therapies being offered for a myriad of disorders by private health clinics around the world – and widely touted on the internet -Professor Yamanaka highlighted the key role played by animal research in ensuring that real stem cell therapies are safe and effective:

Yamanaka, who shared the Nobel Prize for Medicine on Monday with John Gurdon of the Gurdon Institute in Cambridge, Britain, called for caution [on stem cell therapies - PB].

“This type of practice is an enormous problem, it is a threat. Many so-called stem cell therapies are being conducted without any data using animals, preclinical safety checks,” said Yamanaka of Kyoto University in Japan.

“Patients should understand that if there are no preclinical data in the efficiency and safety of the procedure that he or she is undergoing … it could be very dangerous,” he told Reuters in a telephone interview.

Yamanaka and Gurdon shared the Nobel Prize for the discovery that adult cells can be transformed back into embryo-like stem cells that may one day regrow tissue in damaged brains, hearts or other organs.

“I hope patients and lay people can understand there are two kinds of stem cell therapies. One is what we are trying to establish. It is solely based on scientific data. We have been conducting preclinical work, experiments with animals, like rats and monkeys,” Yamanaka said.”

 

Paul Browne

 

 

 

Restoring vision in night blindness: Mice point way to stem cell therapy

Impaired vision and blindness are leading causes of disability, affecting over 3 million people in the USA today, so it’s no surprise that biomedical scientists are working hard to develop therapies to improve and restore vision.  Over the past few years we have discussed several therapies that have been developed to treat different types of vision loss, including anti-angiogenic therapies to treat wet age related macular degeneration, a leading cause of severe, irreversible vision loss in the elderly,  and gene therapy to treat Leber congenital amaurosis, an inherited disease characterised by progressive degeneration of the retina. Speaking of Research committee member Dario Ringach has also written on the Opposing Views website on the very promising research now underway to develop electronic prosthesis to restore vision in blind people.

In another important development in this field Professor Robin Ali* and his team at the UCL Institute of Ophthalmology have announced the first demonstration that transplanted retinal rod cells can improve vision in mice with night-blindness, publishing the results of their study in the prestigious science journal Nature1. Rod cells are photoreceptor cells in the retina of the eye that function well in low light conditions, and an absence of rod cells leads to night blindness. Mutations in the gene GNAT1 cause congenital night blindness in humans, and mice in which the Gnat1 gene has been knocked out are night blind.  In the video below Professor Ali show that by transplanting rod cell precursors into the retina of Gnat1 knockout mice his team was able to restore vision – albeit  not fully.

It’s a fascinating piece of work, though as Professor Ali makes clear in comments to the Guardian newspaper last week there is still a lot of work to do before this can be evaluated in humans.

Now we’ve discovered we can restore vision, it gives us impetus to go on and make the process better”

As both the video and Guardian article indicate an important step will be identifying suitable sources of cells for transplantation, with both embryonic stem cells and induced pluripotent stem (iPS) cells under consideration.  This may not take as long as one might think, as we discussed last November a clinical trial was recently launched to assess the potential for transplantation of another retinal cell type, retinal epithelial cells derived from human embryonic stem cells , to improve vision in patients with  Stargart’s Macular Dystrophy, an inherited form of blindness.

The work of Professor Ali and his colleagues at UCL is moving us closer to an effective treatment – and perhaps it is not unrealistic to talk about a cure – for night blindness. Their work will also no doubt drive research on protoreceptor cell transplantation in other forms of blindness, such as dry age related macular degeneration – the most common cause of vision loss in people aged over 50 – which is characterised by loss of both rod and cone photoreceptor cells.

Paul Browne

*        Professor Ali also played a leading role in the development of gene therapy for Leber congenital amaurosis, and led the first clinical trial of this technique.

1)      Pearson RA, Barber AC, Rizzi M, Hippert C, Xue T, West EL, Duran Y, Smith AJ, Chuang JZ, Azam SA, Luhmann UF, Benucci A, Sung CH, Bainbridge JW, Carandini M, Yau KW, Sowden JC, Ali RR. “Restoration of vision after transplantation of photoreceptors.Nature. 2012 Apr 18. doi: 10.1038/nature10997.

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

FASEB Excellence in Science Award for Stem Cell Pioneer

The Federation of American Societies for Experimental Biology (FASEB) is one of the world’s largest and most influential scientific organizations, representing 23 independent scientific societies and over 90,000 individual scientists. Regular readers of this blog will be aware that FASEB also takes a keen interest in educating and informing the public about the value and achievements of biomedical research. Every year FASEB presents the Excellence in Science Award to ‘recognize outstanding achievement by women in biological science’, and this year the award has been given to Professor Gail Martin of the University of California, San Fransisco, principally for discoveries she made in mice.

Professor Gail Martin, stem cell pioneer and winner of the FASEB Excellence in Science award. Image courtesy of UCSF.

Gail Martin was the first scientist to isolate embryonic stem cells, a term she coined, from the mouse embryo and culture them in vitro in 1981, and demonstrated that when injected into a mouse these cells formed a type of tumor known as a teratoma (1).  The production of a teratoma was very significant since these tumors contain normal cells from all three of the germ layers that give rise to every tissue in our bodies, so their presence confirmed that the cells were pluripotent. This seminal study, along with the nearly simultaneous discovery by Martin Evans and Matthew Kaufman that pluripotent stem cells derived from the mouse embryo could be grown in the  mouse uterus, paved the way for the whole field of embryonic stem cell research and more recently the development of induced pluripotent stem (iPS) cells.

Gail Martin’s research continues to focus on the mechanisms that control early embryonic development in mice, chickens and zebrafish, with a particular focus on the role of the Fibroblast Growth Factor (FGF) family of signaling molecules. Her work is an example of basic research at its best. Mutations in FGF receptors are associated with more than a dozen congenital bone disorders (2), and it is through understanding of the fundamental processes involved in controlling development that we will be able to design effective treatments for these disorders.

We congratulate Professor Martin on this award, an award that highlights a career that has contributed a great deal to our understanding of life.

Gail Martin was not the only one to be honored last week, on Sunday our own Professor David Jentsch received the Joseph Cochin Young Investigator award by the College on Problems of Drug Dependence (CPDD). The CPDD is the largest and oldest organization for the scientific study of drug dependence and addictions in the US, whose members have made great contributions to the treatment of drug dependence, and is a World Health Organization collaborating centre for research and training.  Every year the CPDD awards the Joseph Cochin Young Investigator award to an investigator under the age of 40 in recognition of their research contributions to the field of drug abuse, and this award emphasises the importance of the David’s work to future progress in treating drug addictions.

J. David Jentsch, Professor of Psychology and Psychiatry & Biobehavioral Sciences at UCLA.

Well done to David from all your friends at Speaking of Research!

Paul Browne

  1. Martin G.R. “Isolation of a pluripotent cell line from early mouse embryos cultured in medium conditioned by teratocarcinoma stem cells.” Proc Natl Acad Sci U S A. Volume 78(12), Pages 7634-7638 (1981). PubMed Central: PMC349323
  2. Chen L. and Deng C.X. “Roles of FGF signaling in skeletal development and human genetic diseases” Front Biosci. Volume 1;10, Pages 1961-1976 (2005). PubMed: 15769677