Not Exactly Rocket Science

Blogging on Peer-Reviewed ResearchIt’s a good time to be a stem cell researcher. Legal and political wrangling aside, the discoveries are starting to come thick and fast now and new breakthroughs seem constantly around the corner. Last November, I was writing about two groups of scientists who had managed to turn adult human cells into embryonic stem cells for the first time. Now, after less than a year, John Dimos and Kit Rodolfa from the Harvard Stem Cell Institute have given us two more surpassed milestones for the price of one.

As before, they have transformed adult skin cells have been into embryonic stem cells but this time, there are two important differences. Firstly, the cells that came not from a young, healthy individual, but from an 82-year old woman with amyotrophic lateral sclerosis (ALS), the same condition that has paralysed Stephen Hawking. Even after a lifetime of chronic disease, the adult cells could still be reverted to a stem-like state.

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It’s more of an expansion on a theme than an isolated breakthrough but it’s nonetheless important. Many of the diseases behind the stem cell hype are chronic conditions that affect the elderly – Alzheimer’s, Parkinson’s and the like. The ultimate goal of this research is to use the cells of patients with these conditions to generate personalised embryonic stem cells. These can then be used to grow cells-of-choice to replace those lost through disease, without fear of reprisals from the patient’s immune system. The new study shows that the first of these steps is possible, even for very old people suffering from advanced disease.

More importantly, Dimos and Rodolfa have achieved the second step too; they converted the reprogrammed stem cells into motor neurons, the same cells that are affected by the donor’s disease. This double-whammy of transformations is exactly the type of thing we need to realise the potential of stem cell therapies.

Skin to stem to nerve

The woman in question is named only as A29. Dimos and Rodolfa took skin cells from her arm and exposed them to the same quartet of transformative genes used by the Japanese researchers who pioneered the technique.

After two weeks, they found what they were looking for – small colonies of ‘induced pluripotent stem cells’, or IPS cells, that were very much like embryonic stem cells. They had the same, the same activated genes and the same proteins on their surface. Unlike their skin cells forefathers, they were actively dividing and divided into all the types of cells expected of embryos.

For their next trick, the team converted the IPS cells into a variety of different nerve cells, by using small molecules to stimulate two molecular signalling pathways. These triggered a programme of development that coaxed the IPS cells into becoming neurons. Dimos and Rodolfa confirmed the nature of their new cells by checking their shape under the microscope and staining them with a dye designed to only stick to neurons. About 20% of the cells had activated genes that singled them out as motor neurons, and mature ones at that.

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It’s an important step, but it’s not time to hang up the lab coats yet. The team still need to work out how similar these cells-formerly-known-as-skin-cells are to motor neurons that actually come from normal embryonic stem cells.

There are safety issues too – the reprogramming technique relies on using viruses to insert the four essential genes into the DNA of the adult cells. If the genes are shoved into places that disrupt other genes, it could set the cells down the road to cancer. That risk makes the viruses a big no-no; before stem cell therapies hit the big time, we need better methods for importing the relevant genes.  

Motoring on

So there’s still a way to go, but for the moment, there are more immediate benefits. As important as the study is for stem cell research, it’s a veritable godsend for ALS research. The disease caused by the gradual death of the body’s motor neurons – the cells that carry signals from the central nervous system to the muscles. Without these signals, the muscles of ALS sufferers gradually weaken and waste away. Voluntary movements become impossible, and in most cases, people lose the ability to swallow or breathe. It’s a horrible disease that usually kills within 3 to 5 years.

So far, progress in understanding the disease has been relatively slow, mainly because it has been nigh impossible to obtain a decent supply of living motor neurons affected by the condition. But Dimos and Rodolfa’s work changes all of that.

Now, researchers can culture large colonies of both motor neurons and glia that carry genetic defects associated with ALS. That gives them free reign to investigate the genetic defects that underlie the disorder, the environmental conditions that interact with these genes, and the way the affected neurons interact with other types of cell. It also provides them with neurons to use for screening and testing potential drugs. It’s a starting pistol, and a loud one at that.

And just one more thing…

i-2227d50bb97e26a47fce3338e88beb9f-Stemcell1.jpgAnother study published this week adds another twist to the stem cell tale and I’m going to touch on it briefly. Stem cells are notable for their ability to produce any type of cell in the body and it’s this unique mass of potential that underlies their future in treating diseases. Other cells must settle for becoming more and more specialised as options for development become increasingly closed to them. It has always been thought that there was no going back for these cells, no way to regain their lost potential without the type of genetic manipulation I wrote about above.

But Molly Weaver and Mark Krasnow from Stanford University have proved otherwise. They have found that some cells in the fruit fly Drosophila are entirely capable of reversing the hands of fate and regaining their lost potential of their own accord.

During metamorphosis, when Drosophila transforms from squirming maggot to buzzing fly, most of its cells die. Its adult body is grown anew from stem cells in clusters of tissue called ‘imaginal discs’ clustered around its body. Or so people thought.

Using a jellyfish protein that makes cells grow a fluorescent green, Weaver and Krasnow followed the destinies of individual cells as the changing grew its new network of adult breathing tubes – their trachea. They found that many of these new cells come from the stem cells of the imaginal discs but others arose from a completely unexpected source – the larva’s own trachea.

These fully specialised cells had reverted back to an earlier stage where they were capable to producing any of the myriad cell types that make up the trachea. Similar turnarounds have been seen in mammals, where so-called ‘facultative stem cells’ have been seen to revert to a more ‘stemmy’ state to replenish lost cells.

This discovery in a humble fly might seem irrelevant in the face of all the bold, headline-grabbing research with human cells but it could turn out to be very useful. In Drosophila, scientists can now have a model in which to study this phenomenon, and one that can be genetically manipulated with ease. The discovery could also be harnessed to develop ways of transforming adult cells into stem cells without the use of viruses and the cancer-causing potential that accompanies them.  

References: Science doi: 10.1126/science.1158799 and 10.1126/science.1158712

Comments

  1. #1 KAS
    August 1, 2008

    Solidifying, comprehensible and interesting, Thanks!

    KAS

  2. #2 tguy
    August 1, 2008

    Wow, just wow.

    Great stuff.

  3. #3 McDawg
    August 2, 2008

    Nice review Ed. We were already discussing this Manuscript over at the ALSTDI Forum http://www.als.net/forum/topic.asp?TOPIC_ID=3186 and I’ve just placed a link back to this blog post.

    BTW – look forward to meeting you and the other attendees at Science Blogging 2008 in London.

  4. #4 Dr. Roeder
    August 2, 2008

    Two very imported steps. The next seems to be the targeted transfer to a default location of the genome.
    The known techniques of gene transfer to plant cells lack of the wished pinpoint accuracy the same way.
    Good luck to Dimos and Rodolfa and all the others!

  5. #5 Daniel D. Brown
    August 6, 2008

    Truly excellent summary – I kept thinking of things I wanted to comment on only to find that you already covered it in the next sentence.

    It seems clear now that these iPS cells are THE revolution in biology and medicine that we’ve been waiting for. Now if we could only figure out how to turn this “quartet” of genes on rather than having to shove new transgenes into the genome, or perhaps use some other targeted delivery, or perhaps transgenic method that could reverse itself after differentiation or something, we would be golden. Assuming we could then get the cells differentiated and integrated long term within the correct tissues.

    Great work, great article!

  6. #6 JeepnDave
    January 29, 2009

    Thanks for the breakdown on some of the stem cell breakthroughs that are happening rather quickly now. Hopefully 2009 will see the US finally lift the federal band on funding

  7. #7 Dan
    March 28, 2009

    Excellent post with stem cell potential to cure and relieve suffering.

    The apex of cellular therapy and regenerative/reparative medicine has been reborn after an 8 year moratorium that basically halted federal funding for stem cell research with most states in the U.S.

    Now the NIH can award grants to scientists involved with biomedical research involving stem cell therapy.

    While never banned, stem cell research had limited funding during this time. And this was unfortunate, because there are several likely uses of stem cells.

    These uses include the replacement of tissues in the human body, as well as repairing cell types that are defective. Also, stem cells can deliver genetic therapies that are needed.

    ESCs are totiplotent if obtained from the morula which is a pre-blastocyst stage. Normally, the stem cells are acquired from the blastocyst itself. From this source, the stem cells can be any cell in the human body except for the placenta.

    Embryonic stem cells are obtained from a 4 day old embryo called a blastocyst, and are pluripotent from this source. The blastocyst contains about 100 cells, and is not suitable at this stage for implantation into the uterine wall.

    The inner core of the blastocyst has about 20 cells, and this is where stem cells are obtained.

    These cells are unspecialized cells that can be developed or morphed into the over 200 cells available in the human body through differentiation, as ESCs are undifferentiated by nature.

    As such, they can become any human cell, as long as they are prevented from clumping or crowding together when explanted into cultures as they are propagated.After stem cells are cultured, they are moved to what are called stem lines.

    Positive results from stem cell therapy are seen usually within a month, and patients can request another treatment about 6 months after the first treatment presently. This stem cell paradigm of therapy addresses the etiology of a disease state, instead of focusing on the symptoms only.

    Until recently, ESCs were believed to be most beneficial instead of the adult stem cell alternative (ASC). However ASCs (somatic stem cells) now can be coerced into differentiation through plasticity (trans-differentiation).

    Thanks to molecular biology, four transcription factors control the transfer of genetic information from DNA to RNAS to regulate gene expression. So ASCs can have the same beneficial qualities as ESCs.

    In the past, viral vectors and exotic genes interfered with the purity of ASCs. Now ASCs are re-programmed using plasmids instead of viruses and oncogenes that can become detrimental for the patient treated.

    So now, ASCs can safely become induced pluripotent cells with the same potential as ESCs. As a result, the ASCs are free of genetic artifacts that potentially can interfere with transgene sequences.

    They are capable of, and are able to renew and reproduce with minimal effort. Human blood can be reproduced with stem cells under the right conditions.

    SCT can also be used to investigate disease states for better treatment options. Disease-specific stem cell lines, which are those cells that are pluripotent and are created with the same genetic errors of certain diseases, are studied for this reason.

    So there clearly is a huge potential for stem cell-based therapies. The first FDA approved clinical trial occurred early in 2009. This human trial will involve evaluating primarily the safety of escs designed to be used as treatment for spinal cord injury patients. The trial was submitted by Geron Corp.

    Pfizer, the largest drug company, has implemented stem cell research, as they are an asset to drug discovery by creating within the organization a regenerative medicine unit. Other large pharma companies are implemented similar research protocols for the same reasons.

    Geron Corp. in California is the world’s leading esc developer, and financed researchers at univ. of Wisconsin, who isolated the first human esc in 1998.

    Some believe ethical restraints are needed regarding the use of ESCs for therapeutic reasons. Yet they improve the quality of life of those with devastating diseases which involves suffering without any relief.

    So stem cell therapy and research may be the most right and ethical thing to do for such patients.

    Embryos are acquired from fertility clinics (IVFs) that have thousands routinely stored and are abnormally fertilized. This means that they could never go on to become a human, and would be destroyed otherwise.

    Ironically, one could argue it is inappropriate to discard what may be valuable and ethical for others, potentially.

    Most couples with frozen embryos would gladly give them to such research, surveys have concluded.

    These embryos are believed by many to not be morally equivalent to human life, but only have the potential for life. And they are used for therapeutic cloning, known as somatic cell nuclear transfer, and not reproductive cloning.

    Ten states have banned this cloning out of ignorance, it seems. Bioethic principles, which are beneficience, or physician-centered decisions, as well as non-maleficence, which is first do no harm, are not corrupted.

    Furthermore, autonomy, which is the patient’s right to determine their health, and justice or fairness remain intact.

    Stem cells should be utilized for those terminally ill as well, many believe. Many are seeking stem cell therapy overseas due to restrictions in the U.S. presently.

    Dan Abshear