Starving stem cells of oxygen can help build stronger bones

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J. Kent Leach: Photo courtesy UC Davis

We usually think that starving something of oxygen is going to make it weaker and maybe even kill it. But a new study by J. Kent Leach at UC Davis shows that instead of weakening bone defects, depriving them of oxygen might help boost their ability to create new bone or repair existing bone.

Leach says in the past the use of stem cells to repair damaged or defective bone had limited success because the stem cells often didn’t engraft in the bone or survive long if they did. That was because the cells were being placed in an environment that lacked oxygen (concentration levels in bone range from 3% to 8%) so the cells found it hard to survive.

However, studies in the lab had shown that if you preconditioned mesenchymal stem cells (MSCs), by exposing them to low oxygen levels before you placed them on the injury site, you helped prolong their viability. That was further enhanced by forming the MSCs into three dimensional clumps called spheroids.

Lightbulb goes off

In the  current study, published in Stem Cells, Leach says the earlier spheroid results  gave him an idea:

“We hypothesized that preconditioning MSCs in hypoxic (low oxygen) culture before spheroid formation would increase cell viability, proangiogenic potential (ability to create new blood vessels), and resultant bone repair compared with that of individual MSCs.”

So, the researchers placed one group of human MSCs, taken from bone marrow, in a dish with just 1% oxygen, and another identical group of MSCs in a dish with normal oxygen levels. After three days both groups were formed into spheroids and placed in an alginate hydrogel, a biopolymer derived from brown seaweed that is often used to build cellular cultures.

Seaweed

Brown seaweed

The team found that the oxygen-starved cells lasted longer than the ones left in normal oxygen, and the longer those cells were deprived of oxygen the better they did.

Theory is great, how does it work in practice?

Next was to see how those two groups did in actually repairing bones in rats. Leach says the results were encouraging:

“Once again, the oxygen-deprived, spheroid-containing gels induced significantly more bone healing than did gels containing either preconditioned individual MSCs or acellular gels.”

The team say this shows the use of these oxygen-starved cells could be an effective approach to repairing hard-to-heal bone injuries in people.

“Short‐term exposure to low oxygen primes MSCs for survival and initiates angiogenesis (the development of new blood vessels). Furthermore, these pathways are sustained through cell‐cell signaling following spheroid formation. Hypoxic (low oxygen) preconditioning of MSCs, in synergy with transplantation of cells as spheroids, should be considered for cell‐based therapies to promote cell survival, angiogenesis, and bone formation.”

CIRM & Dr. Leach

While CIRM did not fund this study we have invested more than $1.8 million in another study Dr. Leach is doing to develop a new kind of imaging technology that will help us see more clearly what is happening in bone and cartilage-targeted therapies.

In addition, back in March of 2012, Dr. Leach spoke to the CIRM Board about his work developing new approaches to growing bone.

 

Stem cell agency funds Phase 3 clinical trial for Lou Gehrig’s disease

ALS

At CIRM we don’t have a disease hierarchy list that we use to guide where our funding goes. We don’t rank a disease by how many people suffer from it, if it affects children or adults, or how painful it is. But if we did have that kind of hierarchy you can be sure that Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig’s disease, would be high on that list.

ALS is a truly nasty disease. It attacks the neurons, the cells in our brain and spinal cord that tell our muscles what to do. As those cells are destroyed we lose our ability to walk, to swallow, to talk, and ultimately to breathe.

As Dr. Maria Millan, CIRM’s interim President and CEO, said in a news release, it’s a fast-moving disease:

“ALS is a devastating disease with an average life expectancy of less than five years, and individuals afflicted with this condition suffer an extreme loss in quality of life. CIRM’s mission is to accelerate stem cell treatments to patients with unmet medical needs and, in keeping with this mission, our objective is to find a treatment for patients ravaged by this neurological condition for which there is currently no cure.”

Having given several talks to ALS support groups around the state, I have had the privilege of meeting many people with ALS and their families. I have seen how quickly the disease works and the devastation it brings. I’m always left in awe by the courage and dignity with which people bear it.

BrainStorm

I thought of those people, those families, today, when our governing Board voted to invest $15.9 million in a Phase 3 clinical trial for ALS run by BrainStorm Cell Therapeutics. BrainStorm is using mesenchymal stem cells (MSCs) that are taken from the patient’s own bone marrow. This reduces the risk of the patient’s immune system fighting the therapy.

After being removed, the MSCs are then modified in the laboratory to  boost their production of neurotrophic factors, proteins which are known to help support and protect the cells destroyed by ALS. The therapy, called NurOwn, is then re-infused back into the patient.

In an earlier Phase 2 clinical trial, NurOwn showed that it was safe and well tolerated by patients. It also showed evidence that it can help stop, or even reverse  the progression of the disease over a six month period, compared to a placebo.

CIRM is already funding one clinical trial program focused on treating ALS – that’s the work of Dr. Clive Svendsen and his team at Cedars Sinai, you can read about that here. Being able to add a second project, one that is in a Phase 3 clinical trial – the last stage before, hopefully, getting approval from the Food and Drug Administration (FDA) for wider use – means we are one step closer to being able to offer people with ALS a treatment that can help them.

Diane Winokur, the CIRM Board Patient Advocate member for ALS, says this is something that has been a long time coming:

CIRM Board member and ALS Patient Advocate Diane Winokur

“I lost two sons to ALS.  When my youngest son was diagnosed, he was confident that I would find something to save him.  There was very little research being done for ALS and most of that was very limited in scope.  There was one drug that had been developed.  It was being released for compassionate use and was scheduled to be reviewed by the FDA in the near future.  I was able to get the drug for Douglas.  It didn’t really help him and it was ultimately not approved by the FDA.

When my older son was diagnosed five years later, he too was convinced I would find a therapy.  Again, I talked to everyone in the field, searched every related study, but could find nothing promising.

I am tenacious by nature, and after Hugh’s death, though tempted to give up, I renewed my search.  There were more people, labs, companies looking at neurodegenerative diseases.

These two trials that CIRM is now funding represent breakthrough moments for me and for everyone touched by ALS.  I feel that they are a promising beginning.  I wish it had happened sooner.  In a way, though, they have validated Douglas and Hugh’s faith in me.”

These therapies are not a cure for ALS. At least not yet. But what they will do is hopefully help buy people time, and give them a sense of hope. For a disease that leaves people desperately short of both time and hope, that would be a precious gift. And for people like Diane Winokur, who have fought so hard to find something to help their loved ones, it’s a vindication that those efforts have not been in vain.

A TWIST in mesenchymal stem cell trials: protein predicts therapy’s potential

Mesenchymal stem cells are adult stem cells with the potential to specialize into a somewhat limited number of cell types – those responsible for making fat, bone and cartilage. But MSCs are also known for their anti-inflammatory properties which are carried out via the release of protein factors.  This ability to dampen the immune system makes the MSC an extremely attractive source material for cell therapies. In fact, there are over 500  mesenchymal stem cell-based clinical trials testing treatments for diseases that target a wide range of tissues including spinal cord injury, diabetes, multiple sclerosis, respiratory disorders and graft versus host disease, just to name a few.

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Human mesenchymal stem cells grown in a single layer on the bottom of a flask; 4x magnification Image source: EuroStemCell

 MSCs and the Variability Problem
While some MSC-based human trials have had promising results in patients, other studies haven’t been as successful. A key culprit of these mixed results is the lack of standardization on what exactly is a MSC. It’s well documented that preparations of MSC vary significantly from one patient to the next. Even the composition of MSCs from one patient is far from a pure population of cells. And few of the cell surface markers used to define MSCs provide a measure of the cells’ function. This is a real problem for demonstrating the effectiveness and the marketability of MSC-based cell therapies which rely on the delivery of cell product with a consistent, well-defined composition and functional activity.

Help is now on the way based on research reported this week in EBioMedicine by a research team led by Professor Donald Phinney at the Florida campus of The Scripps Research Institute. In the study, the team found that the amount of TWIST1, a protein that regulates gene activity, in a given batch of MSCs could reliably predict the therapeutic effectiveness of those cells.

Meet TWIST1: predictor of a MSC therapy’s potential
They set their sights on TWIST1 because previous research described its important role in driving a MSC fate during human development. The team examined the natural variability of TWIST1 levels in human MSCs from several donors. They showed that lower levels of TWIST1 correlated to MSCs with stronger anti-inflammatory properties. Higher levels of TWIST1, on the other hand, were consistent with MSCs that induced angiogenesis, or blood vessel growth, another known ability of this versatile cell type. In another set of experiments, TWIST1 production was silenced using genetic tools. As predicted by the earlier results, these MSCs showed increased anti-inflammatory properties.

Move over Ritcher, Say Hello to the CLIP Scale

CLIPscale

The Clinical Indication Prediction (CLIP) scale. Image: Boregowda et al. EBioMedicine, Volume 4 , 62-73

Putting this data together, the team devised a scale they call Clinical Indication Prediction, or CLIP for short. The scale gives a clinical researcher an indication of the therapeutic potential of a given batch of donor MSCs based on the TWIST1 protein levels. This information could have a major impact on a clinical trial’s fate. Depending on the goal of a MSC-based cell therapy, a clinical team could set themselves up for failure before the trial even gets underway if they don’t take TWIST1 levels into account. First author Siddaraju V. Boregowda explains this scenario in a press release:

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Siddaraju V. Boregowda

“There are a number of clinical trials testing mesenchymal stem cells to treat arthritis. Since angiogenesis is a key part of the disease process, stem cells with high levels of TWIST1 (indicating they are more angiogenic) would not be beneficial. These cells might be helpful instead for indications such as peripheral vascular disease where new vascularization is beneficial. The proposed CLIP scale accurately predicts these indications and contra-indications.”

We’ll be keeping our eye on this exciting discovery to see if CLIP becomes an integral step in developing MSC-based cell therapies. If it pans out, the CLIP scale could help accelerate the development of new therapies by providing scientists with more clarity and confidence around classifying the identity of a MSC cell product. Stay tuned!