Posts tagged regenerative medicine
Articles and news from the latest research reports.
(Image caption: An undated handout picture released by Japan’s Riken research institute and Foundation for Biomedical Research and Innovation, shows a retina sheet prepared from iPS cells of a woman for transplant surgery. Japanese researchers on Friday conducted the world’s first surgery to implant “iPS” stem cells in a human body in a major boost to regenerative medicine, two institutions involved said. — PHOTO: AFP/RIKEN AND FOUNDATION FOR BIOMEDICAL RESEARCH AND INNOVATION. Adapted from: The Straits Times)
Japanese doctors test method for restoring impaired vision
Japanese doctors have successfully carried out the first ever implantation of a retina grown from induced pluripotent stem cells (iPS).
The recipient was a 70-year-old woman suffering from macular degeneration.
The procedure took place Friday at the Institute of Biomedical Research and Innovation in the southern city of Kobe, under the direction of a group of scientists from the Riken Institute.
Researchers extracted skin samples from women to grow iPS cells capable of serving as retinal tissue, which then were used to surgically replace part of the macula, the main photo-receptor layer of the retina.
The scientists said that their priority was not to attempt to restore the patient’s sight, but to determine if there are any unforeseen side effects, such as tumours, arising from the procedure.
According to the researchers, who will study the patient’s evolution over the next four years, since the patient will have already lost most of the cells responsible for vision, a transplant may bring only slight improvement or merely slow down the rate of degeneration.
Macular degeneration is an age-related disease that currently affects about 700,000 people in Japan and is the principal cause of blindness in the world.
Limb regeneration: do salamanders hold the key?
For the first time, researchers have found that the ‘ERK pathway’ must be constantly active for salamander cells to be reprogrammed, and hence able to contribute to the regeneration of different body parts.
The team identified a key difference between the activity of this pathway in salamanders and mammals, which helps us to understand why humans can’t regrow limbs and sheds light on how regeneration of human cells can be improved.
The study published in Stem Cell Reports, demonstrates that the ERK pathway is not fully active in mammalian cells, but when forced to be constantly active, gives the cells more potential for reprogramming and regeneration. This could help researchers better understand diseases and design new therapies.
Lead researcher on the study, Dr Max Yun (UCL Institute of Structural & Molecular Biology) said: “While humans have limited regenerative abilities, other organisms, such as the salamander, are able to regenerate an impressive repertoire of complex structures including parts of their hearts, eyes, spinal cord, tails, and they are the only adult vertebrates able to regenerate full limbs.
We’re thrilled to have found a critical molecular pathway, the ERK pathway, that determines whether an adult cell is able to be reprogrammed and help the regeneration processes. Manipulating this mechanism could contribute to therapies directed at enhancing regenerative potential of human cells.”
The ERK pathway is a way for proteins to communicate a signal from the surface of a cell to the nucleus which contains the cell’s genetic material. Further research will focus on understanding how this important pathway is regulated during limb regeneration, and which other molecules are involved in the process.
(Source: ucl.ac.uk)
In a cloning first, scientists create stem cells from adults
Scientists have moved a step closer to the goal of creating stem cells perfectly matched to a patient’s DNA in order to treat diseases, they announced on Thursday, creating patient-specific cell lines out of the skin cells of two adult men.
The advance, described online in the journal Cell Stem Cell, is the first time researchers have achieved “therapeutic cloning” of adults. Technically called somatic-cell nuclear transfer, therapeutic cloning means producing embryonic cells genetically identical to a donor, usually for the purpose of using those cells to treat disease.
Stress gives cells a ‘second childhood’
What doesn’t kill cells may make them stronger—or considerably more flexible, at least. New findings from Haruko Obokata of the RIKEN Center for Developmental Biology in Kobe and Charles Vacanti at Brigham and Women’s Hospital in the United States suggest that exposing mouse cells to acidic stress can make them regress to an extremely developmentally immature state, transcending even that of embryonic stem (ES) cells (1, 2).
ES cells have the developmental capacity to form any tissue type in the body and this ‘pluripotency’ makes them of great interest to both scientists and clinicians. As these cells must be harvested from early-stage embryos, however, human ES cell research remains a politically and ethically fraught issue. As an alternative, researchers can ‘reprogram’ adult cells into ES cell-like induced pluripotent stem (iPS) cells, which offer the advantage of being genetically matched to their donor—an important consideration for regenerative medicine. However, the generation of iPS cells typically requires the introduction of reprogramming genes, which may affect their function or risk of cancerous transformation.
Obokata and colleagues have now discovered an alternative route to pluripotency, drawing on inspiration from the plant world. “Plants [such as] carrots can produce stem cells from totally differentiated cells when they are exposed to strong external stresses like dissection,” Obokata said in a recent interview with Nature. “I instinctively felt that we may have a similar mechanism to plants.”
Switching brain development on, and off
The possibility of nerve cell regeneration is a step closer after neuroscientists identified the genetic signals that play a crucial role in normal development - driving stem cells to produce neurons that are correctly positioned and connected neurons within the brain.
Published in Cerebral Cortex, a study led by Dr Julian Heng of the Australian Regenerative Medicine Institute (ARMI) at Monash University, has identified a transcription factor, RP58, which is an important “off switch” for the process of nerve cell formation.
“Known as RP58, this gene switches off Rnd2 expression to control the proper positioning of neurons within the fetal brain - a crucial process,” Dr Heng said.
Absence of RP58 has been linked to a rare brain developmental disorder known as Terminal 1q deletion syndrome, where patients suffer reduced brain growth, experience epileptic seizures and are intellectually disabled.
Dr Heng’s work, on pre-clinical models, builds on previous research in which another transcription factor, Neurog2, operated as the “on-switch” for the crucial process of early brain development whereby stem cells become neurons.
Neurog2 switches on the expression of another gene, Rnd2, to control how new nerve cells of the developing brain find their appropriate location and go on to establish their proper connections. However, too much Rnd2 can impair the path-finding of new neurons, and so the researchers theorised that an “off-switch” controlled the process.
Dr Heng said that the discovery of RP58 was the proof needed to demonstrate that genes such as Rnd2 must be switched on, and then off in order for brain cells to assemble properly.
“Together with a collaborative study we published with our colleagues earlier in the year, this research demonstrates that loss of RP58 impairs the development of new nerve cells in the embryonic mouse brain, including their path-finding,” Dr Heng said.
“Since the early steps of nerve cell production during brain development are comparable between mice and humans, we believe that RP58 carries out similar functions in the foetal human brain as well. This strengthens the notion that disruptions to this gene can cause brain developmental disease.”
Recently, a study led by researchers at Stanford University in the United States provided evidence showing that RP58 (also known as ZFP238) is crucial for the maturation of new human nerve cells.
Dr Heng believes his discoveries could be used in the context of regenerative medicine.
“Ultimately, the goal of our research is to understand the fundamental properties which control the production and maturation of new nerve cells in the brain. Understanding the function of switches like RP58 is crucial to this process,” Dr Heng said.
"In the future, we will use this knowledge to develop novel cell-based therapies to treat neurodegenerative disorders and brain injury.”
Stem cells reprogrammed using chemicals alone
Scientists have demonstrated a new way to reprogram adult tissue to become cells as versatile as embryonic stem cells — without the addition of extra genes that could increase the risk of dangerous mutations or cancer.
Researchers have been striving to achieve this since 2006, when the creation of so-called induced pluripotent (iPS) cells was first reported. Previously, they had managed to reduce the number of genes needed using small-molecule chemical compounds (1, 2), but those attempts always required at least one gene, Oct4.
Now, writing in Science, researchers report success in creating iPS cells using chemical compounds only — what they call CiPS cells.
Hongkui Deng, a stem-cell biologist at Peking University in Beijing, and his team screened 10,000 small molecules to find chemical substitutes for the gene. Whereas other groups looked for compounds that would directly stand in for Oct4, Deng’s team took an indirect approach: searching for small-molecule compounds that could reprogram the cells in the presence of all the usual genes except Oct4.
Then came the most difficult part. When the group teamed the Oct4 replacements with replacements for the other three genes, the adult cells did not become pluripotent, or able to turn into any cell type, says Deng.
Fine-tuning
The researchers tinkered with the combinations of chemicals for more than a year, until they finally found one that produced some cells that were in an early stage of reprogramming. But the cells still lacked the hallmark genes indicating pluripotency. By adding DZNep, a compound known to catalyse late reprogramming stages, they finally got fully reprogrammed cells, but in only very small numbers. One further chemical increased efficiency by 40 times. Finally, using a cocktail of seven compounds, the group was able to get 0.2% of cells to convert — results comparable to those from standard iPS production techniques.
The team proved that the cells were pluripotent by introducing them into developing mouse embryos. In the resulting animals, the CiPS cells had contributed to all major cell types, including liver, heart, brain, skin and muscle.
“People have always wondered whether all factors can be replaced by small molecules. The paper shows they can,” says Rudolf Jaenisch, a cell biologist at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, who was among the first researchers to produce iPS cells. Studies of CiPS cells could give insight into the mechanisms of reprogramming, says Jaenisch.
The frog’s secret
The achievement could even help regenerative biologists to work out how amphibians grow new limbs. Deng’s group found that one gene indicative of pluripotency, Sall4, was expressed much earlier in the CiPS-cell reprogramming process than in iPS-cell reprogramming. The same Sall4 involvement is seen in frogs that regenerate a lost a limb: before the regeneration, cells in the limb de-differentiate, a process akin to reprogramming, and Sall4 is active early in that process.
The discovery “provides an important framework to decipher the signalling pathways leading to Sall4 expression” in regulating limb regeneration, says Anton Neff, who studies organ regeneration at Indiana University in Bloomington.
Sheng Ding, a reprogramming researcher at the Gladstone Institutes in San Francisco, California, says that the study marks “significant progress” in the field, but notes that chemical reprogramming is unlikely to be used widely until the team can show that it can work for human cells, not just mouse ones. Other strategies, including one that uses RNA, can complete reprogramming with less risk of disturbing the genes than the original iPS-generation method, and are already in use in humans. Indeed, clinical trials with iPS cells derived through such means are already being planned.
Deng has made some progress towards using his method in human cells, but it will require tweaks. ”Maybe some additional small molecules are needed,” he says.
If it the technique is found to be safe and effective in humans, it could be useful for the clinic. It does not risk causing mutations, and the compounds themselves seem to be safe — four of them are in fact already in clinical use. The small molecules can easily pass through cell membranes, so they can be washed away after they have initiated the reprogramming.
Dream of regenerating human body parts gets a little closer
Damage to vital organs, the spinal cord, or limbs can have an enormous impact on our ability to move, function – and even live. But imagine if you could restore these tissues back to their original condition and go on with life as normal.
Well, this is the dream for regenerative medicine. And while humans missed out on these abilities in the evolutionary lottery, a recent study in mice shows we’re making small progress to achieving this dream.
Learning from animals
Nature has provided the animal kingdom with many different ways to achieve perfect regeneration. Some amphibians – such as salamanders – are famous for their superhero-like ability to regenerate heart, brain, spinal cord, tail and can even whole limb tissue throughout their life.
Although organ and spinal cord regeneration are clinically important and worthy of intense research investment, regrowing whole limbs provides a flagship example of perfect regeneration in the salamander.
It has been known for more than a hundred years that if a salamander loses a limb, it grows right back. This process is extremely precise and removal of the limb at the shoulder regrows a full limb, but removal at the wrist only regrows the missing hand portion.
Interestingly, there does not seem to be a limit on how many times they can perform this clever trick and each time the limb comes back perfect.
But mammals (including humans and mice) seem to have missed out on this important skill. The question of how to enhance the regenerative capabilities in humans, either by adding the missing ingredients, or activating these latent abilities currently lies wide open.
Extending regeneration to mammals
Mammals currently only have the capacity to regenerate the very tip of their finger. But the result is far from perfect. A range of studies in mice have shown the digit-tip regrowth is severely restricted. Removal of the very tip of the mouse digit will be replaced, but removal of the tissue a small distance further up the digit and closer to nail bed (the equivalent to a human cuticle), will fail to regrow.
Last week, a group of researchers from the United States and Japan published work extending our understanding of the mechanism by which a resident stem cell population within the mouse digit tip nail bed can be activated to induce digit tip regeneration. In other words, we can now grow more of the digit back in mice and possibly more of the human finger.
Resident stem cells are specialised cells found at various locations within the body. When activated, these cells multiply and then transform into other cell types required to replace worn out cells under conditions of normal tissue maintenance.
This work builds on previous studies identifying the stem cell population in the nail bed by unveiling a signalling mechanism that could be exploited to enhance the amount of tissue that could be regrown. The potential for repair after injury appears very limited in many tissues and organs. Understanding how to enhance stem cell activation in these tissues may stimulate repair not previously thought possible.
The ability to switch on and mobilise resident stem cells in regeneration will be important in a wide range of new therapies, particularity for organs affected by injury or disease. On a world stage, momentum is currently growing for these types of strategies. It is clear that once refined, these approaches are sure to have a profound influence on many different aspects of clinical medicine, opening up the possibility of replacing diseased or injured tissues.
We may be some way off from the dream of replacing whole limbs in humans but recent progress confirms that by deepening our understanding of stem cell activation, we can directly unlock more regeneration in mammals than normally possible.
Do salamanders hold the solution to regeneration?
Salamanders’ immune systems are key to their remarkable ability to regrow limbs, and could also underpin their ability to regenerate spinal cords, brain tissue and even parts of their hearts, scientists have found.
In research published today in the Proceedings of the National Academy of Sciences researchers from the Australian Regenerative Medicine Institute (ARMI) at Monash University found that when immune cells known as macrophages were systemically removed, salamanders lost their ability to regenerate a limb and instead formed scar tissue.
Lead researcher, Dr James Godwin, a Fellow in the laboratory of ARMI Director Professor Nadia Rosenthal, said the findings brought researchers a step closer to understanding what conditions were needed for regeneration.
"Previously, we thought that macrophages were negative for regeneration, and this research shows that that’s not the case - if the macrophages are not present in the early phases of healing, regeneration does not occur," Dr Godwin said.
"Now, we need to find out exactly how these macrophages are contributing to regeneration. Down the road, this could lead to therapies that tweak the human immune system down a more regenerative pathway."
Salamanders deal with injury in a remarkable way. The end result is the complete functional restoration of any tissue, on any part of the body including organs. The regenerated tissue is scar free and almost perfectly replicates the injury site before damage occurred.
"We can look to salamanders as a template of what perfect regeneration looks like," Dr Godwin said.
Aside from “holy grail” applications, such as healing spinal cord and brain injuries, Dr Godwin believes that studying the healing processes of salamanders could lead to new treatments for a number of common conditions, such as heart and liver diseases, which are linked to fibrosis or scarring. Promotion of scar-free healing would also dramatically improve patients’ recovery following surgery.
There are indications that there is the capacity for regeneration in a range of animal species, but it has, in most cases been turned off by evolution.
"Some of these regenerative pathways may still be open to us. We may be able to turn up the volume on some of these processes," Dr Godwin said.
"We need to know exactly what salamanders do and how they do it well, so we can reverse-engineer that into human therapies."
(Source: monash.edu)
In a paper published in Cell yesterday, scientists from the US and Thailand have, for the first time, successfully produced embryonic stem cells from human skin cells.
That sounds interesting, but what are stem cells and where do they come from?
If you take a limb from a rose tree, and put it in soil, it will grow into a thriving bush.
But you might say: “Plants are special. This won’t work with animals.” Or will it? If you cut off a lizard’s tail, a new tail may grow. A lobster can grow back a lost claw.
There is a special type of flatworm that can be cut in half, again and again hundreds of times, and each half grows back into a full worm.
Similarly, if you cut out half a human liver, it will grow back. The story of Prometheus, whose liver was eaten away by eagles and regrew each day, suggests that the Greeks of ancient times knew about regeneration of organs.
This sort of regeneration is attributed to special cells called “stem cells”.
Reprogramming the workers
Most of our cells are like many professional workers – they are hardened in their ways and can’t manage career changes.
Blood cells carry oxygen or fight disease, muscle cells expand and contract to move us around, nerve cells carry signals, skin cells form a protective layer over our bodies, and structures made up of kidney cells filter our blood.
The cells of most organs or tissues are referred to as “terminally differentiated” cells. They have specialised, and many won’t divide again. If they are damaged or die they will disappear. This is very important.
Although we feel like we grow a lot after we are born, we really only double in size two or three times and most of our cells don’t divide much.
If they did we would be at great risk from cancer – the uncontrolled doubling of cells at the wrong time.
We have a lot of cells and it is important that none of them run out of control.
But some cells can double to renew themselves and can also differentiate and give rise to specialised progeny.
These are the stem cells. We need them to produce new skin to replace damaged skin cells. Similarly, we need them in our guts to replace damaged cells on the surface of our intestines.
Our blood cells also get worn out as they race around our bodies so we have blood stem cells that divide and replace themselves. They also differentiate to form the different types of white and red blood cells we need.
Australian researchers identified stem cells in the breast that can proliferate and form a complete functioning breast. There are also stem cells in the brain and in the heart.
While stem cells tend to be very rare, they exist in many of our organs.
Types of stem cells
The ultimate stem cells are embryonic stem cells.
These cells are found in the inner cell mass of the early embryo and are referred to as “totipotent” since they have the ability to form every cell that is needed in the growing embryo.
They can be extracted from the early embryo and grown in culture dishes.
They can also be genetically modified by the addition of DNA, then injected back into other embryos or into adult animals where find their way into localities that suit them and replace themselves by duplication or differentiate into other cell types that may be needed. For a long time this type of work had been done primarily in laboratory mice.
The techniques in yesterday’s Cell paper involved injecting the nucleus from a human skin cell into a human egg (the nucleus of which has been destroyed) then growing the resulting embryo until the inner cell mass cells could be harvested.
The method may still be controversial because it uses unfertilised eggs, but many people will regard it as preferable to using human embryos. And there are other interesting methods for making stem cells.
Somatic cells to stem cells
It is also possible to convert skin cells, and indeed many different terminally differentiated cells, back into what are called “induced pluripotent stem cells” or iPS cells.
One uses the “magic four” or “OKSM” set of DNA-binding proteins that govern normal stem cell biology:
- Octamer-binding transcription factor 4 (OCT4)
- Kruppel-like factor 4 (KLF4)
- SRY (sex determining region Y)-box 2 (SOX2)
- cellular myelocytomatosis virus-like gene (MYC)
In 2012 Shinya Yamanaka won the Nobel Prize for discovering how to convert normal cells into iPS cells using the OKSM regulators to turn on and off the right genes and convert skin cells into stem cells.
Researchers are continuing to investigate whether iPS cells have the same therapeutic potential as embryo derived stem cells.
It is hoped that stem cells may provide therapies for people suffering from degenerative diseases.
Skin cells could be taken from a patient, converted to stem cells, and then these could be injected back into the damaged organ.
Ideally, they would repopulate the damaged organ with new cells.
So why doesn’t this happen in normal biology? Why aren’t our own heart stem cells busy trying to repair broken hearts?
They may be but our natural supply of stem cells is limited and presumably insufficient to tackle severe disease.
So why don’t we just have more stem cells in our bodies?
The down side of having too many stem cells may be cancer.
Stem cells share a number of features with cancer cells – both are able to self-renew and double without limit.
One theory about cancer holds that the disease most often originates not from terminally differentiated cells but from one of the small number of stem cells in the relevant tissues.
The obvious concern about using stem cells for therapy is that injecting too many could increase the chances that some of these cells would proliferate beyond control, and ultimately give rise to cancer.
Stem cell therapy for regenerative medicine is an exciting idea.
Every day we are learning more about stem cells – how to purify or make them, and how to grow them in culture and direct them down particular pathways to repopulate different organs.
Future research will assess the risks and how effective they can be in experimental systems and ultimately in human patients.
Human stem cells successfully cloned for the first time
A working process for cloning stem cells from existing human cells has finally been discovered by a team at Oregon Health & Science University.
These stem cells were created by reprogramming healthy skin cells, a goal that has eluded researchers around the world for years. It’s the first key step in developing medical procedures for replacing dying or injured cells with new ones to stave off disease and age. That could mean growing a new liver, or kidney or heart, in the lab for an organ transplant, or even repairing the brains of those suffering with diseases like Parkinson’s.
The team was led by Shoukhrat Mitalipov from the reproductive and developmental sciences department of the Oregon National Primate Research Centre. He said: “A thorough examination of the stem cells derived through this technique demonstrated their ability to convert just like normal embryonic stem cells into several different cell types, including nerve cells, liver cells and heart cells. Furthermore, because these reprogrammed cells can be generated with nuclear genetic material from a patient, there is no concern of transplant rejection.”
"While there is much work to be done in developing safe and effective stem cell treatments, we believe this is a significant step forward in developing the cells that could be used in regenerative medicine."
The technique Mitalipov and his team used is called “somatic cell nuclear transfer” — as you can see in the video, it essentially involves sucking out the DNA from an adult cell and inserting it into the empty nucleus of a donor egg. This creates a clone of the original cell, and is in fact the first step in the cloning method used to create animal clones like Dolly the sheep.
However, in its therapeutic mode, the new cells can be grown as replacements for the original type of cell. That objective hasn’t been reached until now as human eggs are extremely fragile compared to many of the animals which we have cloned. That Mitalipov and team have succeeded is down to research on primates, and adapting primate stem cell research to humans.
As a cell divides after fertilisation, it undergoes several transformations as it prepares to split and multiply. The metaphase is the moment just before a cell splits, as the chromosomes align alongside each other in the very centre of the cell so that, when it splits, one goes one way as another goes the other, each taking the full copy of the genetic code. The researchers managed to stall the metaphase while the cell underwent nuclear transfer, effectively giving the new chromosomes time to get settled before the metaphase finished and cell division proceeded.
An added bonus is that the eggs used have not been fertilised, so there won’t be any debates over the ethics of embryonic stem cells as we have seen in the US in the past. While the researchers placed skin cell nuclei into the receptor egg cells, the method is conceivably similar for any other kind of cell.
And, while it may sounds like the first step towards a practical method for cloning humans, the Mitalipov has made it clear that’s not the aim. “Our research is directed toward generating stem cells for use in future treatments to combat disease. While nuclear transfer breakthroughs often lead to a public discussion about the ethics of human cloning, this is not our focus, nor do we believe our findings might be used by others to advance the possibility of human reproductive cloning.”
The research has been published in the journal Cell.