Making stem cell-derived liver cells to study fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) affects approximately 30% of the population, with that number increasing to 75% in obese individuals. Shockingly, the number of cases is expected to increase 21% by the year 2030 in the United States alone.

liver_fattyliverNAFLD refers to a broad range of liver conditions, which are all characterized by abnormally high levels of fat deposits in the livers of people who do not drink excessive amounts of alcohol. While not always fatal, NAFLD can lead to liver cirrhosis, or extensive scaring of the liver tissue. Cirrhosis, in turn, can cause life-threatening conditions such as liver cancer or liver failure. Whether or not N

AFLD will lead to extensive liver damage is not well understood and the primary therapeutic option is weight loss with no FDA-approved drug options. The projected increase in NALD cases combined with the poor treatment options makes this disease a significant public health burden.

Studying NALD can be quite complicated because the liver is complex organ made up of multiple different cell types. Investigators at the University of Edinburgh have simplified some of this complexity by figuring out a way to generate liver cells in a dish.

In studies published in the Philosophical Transactions of the Royal Society B, these scientists used human embryonic stem cells to generate hepatocyte-like cells (HLCs), or cells that are highly similar to liver cells isolated from humans. When exposed to fatty acids, they saw that the HLCs exhibited hallmarks of NAFLD, such as fat accumulation in liver cells, and changes in gene expression that are indicative of NAFLD.

In a press release, Dr. David Hay, one of the two senior investigators of this study, states:

david hay

Dr. David Hay

“Our ability to generate human hepatocytes from stem cells, using semi-automated procedures, allows us to study the mechanisms of human liver disease in a dish and at scale.”

 

This approach is particularly valuable because it would replace the need to use cancer cell lines for this type of work. While valuable for many reasons, research done in cancer cells lines can be difficult to draw therapeutic conclusions from, because cell lines have significant genetic alternations from normal cells. Generating liver cells from human stem cells provides an important tool for high throughput screening of medically relevant therapies for NALD.

 

Livers skip stem cells, build missing structures from scratch via direct cell identity conversion

Stem cells…eh, who needs them anyway?!

That’s what you might be thinking after today, at least for some forms of liver disease. That’s because a team of researchers from UCSF and Cincinnati Children’s Hospital Medical Center just published results in Nature showing liver cells can directly change identity, or transdifferentiate, in order to build, from scratch, structures missing due to disease.

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The liver contains a network of tubes called bile ducts that carry fat-digesting bile to the small intestine via the gallbladder.
Image: National Cancer Inst.

The extraordinary regenerative power of the liver in animals is well-documented. A human liver, for instance, can fully regrow from just 25% of its original mass. That’s thanks to the hepatocyte, the main type of liver cell, that has the ability to replenish pre-existing tissue lost due to disease or injury. What hasn’t been as clear cut, is whether the hepatocyte has the capacity to change identity and build functional liver structures from scratch that never developed in the first place due to genetic disorders.

To examine that possibility, the study – funded in part by CIRM – focused on an inherited liver disease called Alagille syndrome which is caused by abnormal bile ducts. Produced by the liver, bile helps digest fats in our diet. It travels from the liver via bile ducts – tree branch-like tube structures in the liver – to the gallbladder, where it’s stored before moving on to the small intestine. In Alagille syndrome, the bile ducts are fewer in number, narrower in size or altogether missing. As a result, the bile builds up in the liver causing scarring and severe damage. Nearly half of all those with Alagille syndrome, require a liver transplant, usually in childhood.

The research team mimicked the symptoms of Alagille syndrome in mice by genetically engineering the animals to lack cholangiocytes, the cells that form bile ducts. Sure enough, liver damage from bile buildup was observed in these mice at birth due to the missing bile duct structures, also called the biliary tree. However, 90% of the mice survived and eventually formed a functional biliary tree. The team went on to show, for the first time, that the hepatocytes had converted en masse into cholangiocytes and created the wholly new bile ducts.

liver cell switching

Mice that mimic Alagille syndrome are born without the branches of the biliary tree, an important “plumbing system” in the liver (A), but show a near-normal biliary system as adults (B). To build the missing branches, liver cells switch identity and form tubes, shown in green, that connect to the trunk of the biliary tree, shown in blue (C). Image: Cincinnati Children’s

The underlying molecular mechanisms of this process were further examined. The researchers showed that the lack of a particular gene activity pathway due to the absence of cholangiocytes during development causes a replacement pathway, stimulated by a protein called TGF-beta, to kick into gear. As a result, the hepatocytes convert into cholangiocytes and form bile ducts. To make a direct connection with the human form of the disease, the researchers found evidence that TGF-beta is active in the liver samples of some patients but not in the livers from healthy individuals.

With this Alagille syndrome mouse model in hand, the researchers want to identify which transcription factors – proteins that bind DNA and regulate gene activity – are involved in changing the liver cells into bile duct cells. Holger Willenbring, MD, PhD, a senior author and CIRM grantee, explained the rationale behind this approach in a press release:

willenbring photo

Holger Willenbring

“Using transcription factors to make bile ducts from hepatocytes has potential as a safe and effective therapy. With our finding that an entire biliary system can be ‘retrofitted’ in the mouse liver, I am encouraged that this eventually will work in patients.”

So rather than developing a stem cell-based therapy in the lab which is then transplanted into a patient, this approach would rely on stimulating the regenerative capacity of liver cells that are already inside the body. And if it eventually works in patients with Alagille syndrome, which only affects 1 in 30,000, it’s possible it could be applied to other liver diseases as well.

East Coast Company to Sell Research Products Derived from CIRM’s Stem Cell Bank

With patient-derived induced pluripotent stem cells (iPSCs) in hand, any lab scientist can follow recipes that convert these embryonic-like stem cells into specific cell types for studying human disease in a petri dish. iPSCs derived from a small skin sample from a Alzheimer’s patient, for instance, can be specialized into neurons – the kind of cell affected by the disease – to examine what goes wrong in an Alzheimer’s patient’s brain or screen drugs that may alleviate the problems.

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Neurons created from Alzheimer’s disease patient-derived iPSCs.
Image courtesy Elixirgen Scientific

But not every researcher has easy access to a bank of patient-derived iPSCs and it’s not trivial to coax iPSCs to become a particular cell type. The process is also a time sink and many scientists would rather spend that time doing what they’re good at: uncovering new insights into their disease of interest.

Since the discovery of iPSC technology over a decade ago, countless labs have worked out increasingly efficient variations on the original method. In fact, companies that deliver iPSC-derived products have emerged as an attractive option for the time-strapped stem cell researcher.

One of those companies is Elixirgen Scientific of Baltimore, Maryland. Pardon the pun but Elixirgen has turned the process of making various cell types from iPSCs into a science. Here’s how CEO Bumpei Noda described the company’s value to me:

Bumpei-Noda-200

Bumpei Noda

“Our technology directly changes stem cells into the cells that make up most of your body, such as muscle cells or neural cells, in about one week. Considering that existing technology takes multiple weeks or even months to do the same thing, imagine how much more research can get done than before.”

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With Elixirgen’s technology, different “cocktails” of ingredients can quickly and efficiently turn iPSCs into many different human cell types. Image courtesy Elixirgen Scientific

Their technology is set to become an even greater resource for researchers based on their announcement yesterday that they’ve signed a licensing agreement to sell human disease cells that were generated from CIRM’s iPSC Repository.

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Stephen Lin

“The CIRM Repository holds the largest publicly accessible collection of human iPSCs in the world and is the result of years of coordinated efforts of many groups to create a leading resource for disease modeling and drug discovery using stem cells,” said Stephen Lin, a CIRM Senior Science Officer who oversees the cell bank.

 

The repository currently contains a collection of 1,600 cell lines derived from patients with diseases that are a source of active research, including autism, epilepsy, cerebral palsy, Alzheimer’s disease, heart disease, lung disease, hepatitis C, fatty liver disease, and more (visit our iPSC Repository web page for the complete list).

While this wide variety of patient cells lines certainly played a major role in Elixirgen’s efforts to sign the agreement, Noda also noted that the CIRM Repository “has rich clinical and demographic data and age-matched control cell lines” which is key information to have when interpreting the results of experiments and drug screening.

Lin also points out another advantage to the CIRM cells:

“It’s one of the few collections with a streamlined route to commercialization (i.e. pre-negotiated licenses) that make activities like Elixirgen’s possible. iPSC technology is still under patent and technically cannot be used for drug discovery without those legal safeguards. That’s important because if you do discover a drug using iPSCs without taking care of these licensing agreements, your discovery could be owned by that original intellectual property holder.”

At CIRM, we’re laser-focused on accelerating stem cell treatments to patients with unmet medical needs. That’s why we’re excited that Elixirgen Scientific has licensed access to the our iPSC repository. We’re confident their service will help researchers work more efficiently and, in turn, accelerate the pace of new discoveries.

Using stem cells to take an inside approach to fixing damaged livers

Often on the Stem Cellar we write about work that is in a clinical trial. But getting research to that stage takes years and years of dedicated work. Over the next few months we are going to profile some of the scientists we fund who are doing Discovery, or early stage research, to highlight the importance of this work in developing the treatments that could ultimately save lives.

 This first profile is by Pat Olson, Ph.D., CIRM’s Vice President of Discovery & Translation

liver

Most of us take our liver for granted.  We don’t think about the fact that our liver carries out more than 500 functions in our bodies such as modifying and removing toxins, contributing to digestion and energy production, and making substances that help our blood to clot.  Without a liver we probably wouldn’t live more than a few days.

Our liver typically functions well but certain toxins, viral infections, long-term excess alcohol consumption and metabolic diseases such as obesity and type 2 diabetes can have devastating effects on it.  Under these conditions, functional liver cells, called hepatocytes, die and are replaced with cells called myofibroblasts.  Myofibroblasts are cells that secrete excess collagen leading to fibrosis, a form of scarring, throughout the liver.  Eventually, a liver transplant is required but the number of donor livers available for transplant is small and the number of persons needing a functional liver is large.  Every year in the United States,  around 6,000 patients receive a new liver and more than 35,000 patients die of liver disease.

Searching for options

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Dr. Holger Willenbring

Dr. Holger Willenbring, a physician scientist at UCSF, is one of the CIRM-funded researchers pursuing a stem cell/regenerative medicine approach to discover a treatment for patients with severe liver disease.  There are significant challenges to treating liver disease including getting fully multi-functional hepatocytes and getting them to engraft and/or grow sufficiently to achieve adequate mass for necessary liver functions.

In previous CIRM–funded discovery research, Dr. Willenbring and his team showed that they could partially reprogram human fibroblasts (the most common cell found in connective tissue) and then turn them into immature hepatocytes.  (see our Spotlight on Liver Disease video from 2012 featuring Dr. Willenbring.) These immature hepatocytes, when transplanted into an immune-deficient mouse model of human liver failure, were shown to mature over time into hepatocytes that were comparable to normal human hepatocytes both in their gene expression and their function.

This was an important finding in that it suggested that the liver environment in a living animal (in vivo), rather than in a test tube (in vitro) in the laboratory, is important for full multi-functional maturation of hepatocytes.  The study also showed that these transplanted immature human hepatocytes could proliferate and improve the survival of this mouse model of chronic human liver disease.  But, even though this model was designed to emphasizes the growth of functional human hepatocytes, the number of cells generated was not great enough to suggest that transplantation could be avoided

A new approach

Dr. Willenbring and his team are now taking the novel approach of direct reprogramming inside the mouse.  With this approach, he seeks to avoid the challenge of low engraftment and proliferation of transplanted hepatocytes generated in the lab and transplanted. Instead, they aim to take advantage of the large number of myofibroblasts in the patient’s scarred liver by turning them directly into hepatocytes.

Recently, he and his team have shown proof-of principle that they can deliver genes to myofibroblasts and turn them into hepatocytes in a mouse. In addition these in vivo myofibroblasts-derived hepatocytes are multi-functional, and can multiply in number, and can even reverse fibrosis in a mouse with liver fibrosis.

From mice to men (women too)

Our latest round of funding for Dr. Willenbring has the goal of moving and extending these studies into human cells by improving the specificity and effectiveness of reprogramming of human myofibroblasts into hepatocytes inside the animal, rather than the lab.

He and his team will then conduct studies to test the therapeutic effectiveness and initial safety of this approach in preclinical models. The ultimate goal is to generate a potential therapy that could eventually provide hope for the 35,000 patients who die of liver disease each year in the US.

 

 

Stem cell study shows how smoking attacks the developing liver in unborn babies

smoking mom

It’s no secret that smoking kills. According to the Centers for Disease Control and Prevention (CDC) smoking is responsible for around 480,000 deaths a year in the US, including more than 41,000 due to second hand smoke. Now a new study says that damage can begin in utero long before the child is born.

Previous studies had suggested that smoking could pose a serious risk to a fetus but those studies were done in petri dishes in the lab or using animals so the results were difficult to extrapolate to humans.

Researchers at the University of Edinburgh in Scotland got around that problem by using embryonic stem cells to explore how the chemicals in tobacco can affect the developing fetus. They used the embryonic stem cells to develop fetal liver tissue cells and then exposed those cells to a cocktail of chemicals known to be found in the developing fetus of mothers who smoke.

Dangerous cocktail

They found that this chemical cocktail proved far more potent, and damaged the liver far more, than individual chemicals. They also found it damaged the liver of males and females in different ways.  In males the chemicals caused scarring, in females it was more likely to negatively affect cell metabolism.

There are some 7,000 chemicals found in cigarette smoke including tar, carbon monoxide, hydrogen cyanide, ammonia, and radioactive compounds. Many of these are known to be harmful by themselves. This study highlights the even greater impact they have when combined.

Long term damage

The consequences of exposing a developing fetus to this toxic cocktail can be profound, including impaired growth, premature birth, hormonal imbalances, increased predisposition to metabolic syndrome, liver disease and even death.

The study is published in the Archives of Toxicology.

In a news release Dr. David Hay, one of the lead authors, said this result highlights yet again the dangers posed to the fetus by women smoking while pregnant or being exposed to secondhand smoke :

“Cigarette smoke is known to have damaging effects on the foetus, yet we lack appropriate tools to study this in a very detailed way. This new approach means that we now have sources of renewable tissue that will enable us to understand the cellular effect of cigarettes on the unborn foetus.”

Stem cell stories that caught our eye: functioning liver tissue, making new bone, stem cells and mental health

Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.

Functioning liver tissue. Scientists are looking to stem cells as a potential alternative treatment to liver transplantation for patients with end-stage liver disease. Efforts are still in their early stages but a study published this week in Stem Cells Translational Medicine, shows how a CIRM-funded team at the Children’s Hospital Los Angeles (CHLA) successfully generated partially functional liver tissue from mouse and human stem cells.

Biodegradable scaffold (left) and human tissue-engineered liver (right) (Photo courtesy of The Saban Research Institute at Children’s Hospital Los Angeles)

Biodegradable scaffold (left) and human tissue-engineered liver (right) (Photo courtesy of The Saban Research Institute at Children’s Hospital Los Angeles)

The lab had previously developed a protocol to make intestinal organoids from mouse and human stem cells. They were able to tweak the protocol to generate what they called liver organoid units and transplanted the tissue-engineered livers into mice. The transplants developed cells and structures found in normal healthy livers, but their organization was different – something that the authors said they would address in future experiments.

Impressively, when the tissue-engineered liver was transplanted into mice with liver failure, the transplants had some liver function and the liver cells in these transplants were able to grow and regenerate like in normal livers.

In a USC press release, Dr. Kasper Wang from CHLA and the Keck school of medicine at USC commented:

“A cellular therapy for liver disease would be a game-changer for many patients, particularly children with metabolic disorders. By demonstrating the ability to generate hepatocytes comparable to those in native liver, and to show that these cells are functional and proliferative, we’ve moved one step closer to that goal.”

 

Making new bone. Next up is a story about making new bone from stem cells. A group at UC San Diego published a study this week in the journal Science Advances detailing a new way to make bone forming cells called osteoblasts from human pluripotent stem cells.

Stem cell-derived osteoblasts (bone cells). Image credit Varghese lab/UCSD.

Stem cell-derived osteoblasts (bone cells). Image credit Varghese lab/UCSD.

One way that scientists can turn pluripotent stem cells into mature cells like bone is to culture the stem cells in a growth medium supplemented with small molecules that can influence the fate of the stem cells. The group discovered that by adding a single molecule called adenosine to the growth medium, the stem cells turned into osteoblasts that developed vascularized bone tissue.

When they transplanted the stem cell-derived osteoblasts into mice with bone defects, the transplanted cells developed new bone tissue and importantly didn’t develop tumors.

 In a UC newsroom release, senior author on the study and UC San Diego Bioengineering Professor Shyni Varghese concluded:

“It’s amazing that a single molecule can direct stem cell fate. We don’t need to use a cocktail of small molecules, growth factors or other supplements to create a population of bone cells from human pluripotent stem cells like induced pluripotent stem cells.”

 

Stem cells and mental health. Brad Fikes from the San Diego Union Tribune wrote a great article on a new academic-industry partnership whose goal is to use human stem cells to find new drugs for mental disorders. The project is funded by a $15.4 million grant from the National Institute of Mental Health.

Academic scientists, including Rusty Gage from the Salk Institute and Hongjun Song from Johns Hopkins University, are collaborating with pharmaceutical company Janssen and Cellular Dynamics International to develop induced pluripotent stem cells (iPSCs) from patients with mental disorders like bipolar disorder and schizophrenia. The scientists will generate brain cells from the iPSCs and then work with the companies to test for potential drugs that could be used to treat these disorders.

In the article, Fred Gage explained that the goal of this project will be used to help patients rather than generate data points:

Rusty Gage, Salk Institute.

Rusty Gage, Salk Institute.

“Gage said the stem cell project is focused on getting results that make a difference to patients, not simply piling up research information. Being able to replicate results is critical; Gage said. Recent studies have found that many research findings of potential therapies don’t hold up in clinical testing. This is not only frustrating to patients, but failed clinical trials are expensive, and must be paid for with successful drugs.”

“The future of this will require more patients, replication between labs, and standardization of the procedures used.”

Good from bad: UCSF scientists turn scar-forming cells into healthy liver cells

Most people know that a healthy liver is key for survival. Unfortunately, maintaining a healthy liver isn’t always easy. There are more than 100 different types of liver disease caused by various factors like viral infection, obesity, and genetics. If left untreated, they can progress to end-stage liver disease, also known as cirrhosis, which effects more than 600,000 Americans and has a high mortality rate. While there is a cure in the form of liver transplantation, there aren’t enough healthy donors available to help out the number of patients who desperately need new livers.

Cirrhosis occurs when liver damage accumulates over time causing the development of scar tissue that eventually replaces healthy liver tissue and impairs liver function. The liver is an amazing organ and can function even with the build-up of scar tissue as long as at least 20% of its composition is healthy cells. This impressive nature is actually a problem because most patients with liver disease aren’t aware of their condition until its progressed past the point of no return.

What’s a damaged liver to do?

So what do patients with end-stage liver disease do if they can’t get a liver transplant? One answer comes in the form of regenerative medicine. Scientists can generate new healthy liver cells in a dish from stem cells derived from the skin cells of patients and could eventually transplant these cells into the damaged liver. However, a major roadblock that prevents this type of cell transplantation therapy from helping patients with liver disease is the built-up scar tissue that prevents the integration of these healthy cells into the damaged liver.

Scientists from UC San Francisco (UCSF) have come up with a new solution to this problem. In a CIRM-funded study published today in journal Cell Stem Cell, UCSF professor Holger Willenbring details a new approach to repairing damaged livers in mice – one that generates good, healthy liver cells from bad, scar-tissue forming cells already present in the damaged liver.

The bad cells in this case are called myofibroblasts. Initially, these cells play an important role in repairing injuries in the liver. They secrete proteins called collagen that form a support structure that helps maintain composition of the liver as it repairs itself. However, if liver damage persists as is the case with chronic injury, the excess buildup of collagen secreted by myofibroblasts causes the accumulation of permanent scar tissue or fibrosis, which can negatively impact liver function.

Reducing damage by improving function

Cirrhosis causing myofibroblast cells (red) are converted into healthy liver cells (green) to regenerate the damaged liver. (Willenbring lab)

Cirrhosis causing myofibroblast cells (red) are converted into healthy liver cells (green) to regenerate the damaged liver. (Willenbring lab)

In an “Ah-Ha” moment, Willenbring proposed that they could stop myofibroblasts in the damaged livers of mice from causing more fibrosis by turning them into healthy liver cells. Willenbring and his team used a specific type of virus called an adeno-associated virus that only infects myofibroblasts to deliver a cocktail of liver-specific genes that have the ability to transform cells into liver cells called hepatocytes. When they treated mice with end-stage liver disease with their viral cocktail, they observed that a small percentage of myofibroblasts were converted into hepatocytes that developed into new healthy liver tissue, which improved the overall liver function of these mice. They also tested their viral method on human myofibroblasts and found that it was successful in converting these cells into functional hepatocytes.

Willenbring explained the science behind their new technique in a UCSF news release:

“Part of why this works is that the liver is a naturally regenerative organ, so it can deal with new cells very well. What we see is that the converted cells are not only functionally integrated in the liver tissue, but also divide and expand, leading to patches of new liver tissue.”

Solution to a healthy liver?

It’s important to realize that these studies are still in their early stages. The UCSF team has plans to expand on their human cell studies and to improve their viral delivery method so that it is more specific to myofibroblasts and more efficient at converting these cells into functioning hepatocytes.

They also recognize that their strategy will not be the panacea for liver disease and cirrhosis. Willenbring commented:

“A liver transplant is still the best cure. This is more of a patch. But if it can boost liver function by just a couple percent, that can hopefully keep patients’ liver function over that critical threshold, and that could translate to decades more of life.”

However, their study does offer a number of advantages over cell transplant therapies for liver disease including repairing the liver and improving its function from within the organ itself and also offering a simpler and cheaper form of treatment that would be accessible to more patients.

Willenbring puts it best:

Holger Willenbring, UCSF

Holger Willenbring, UCSF

“The new results suggest that in the fibrotic liver, this approach could produce a more efficient and stable improvement of liver function than cell transplant approaches. Once the viral packaging is optimized, such a treatment could be done cheaply at a broad range of medical facilities, not just in the specialized research hospitals where stem-cell transplants could be conducted.”

What’s the big idea? Or in this case, what’s the 19 big ideas?

supermarket magazineHave you ever stood in line in a supermarket checkout line and browsed through the magazines stacked conveniently at eye level? (of course you have, we all have). They are always filled with attention-grabbing headlines like “5 Ways to a Slimmer You by Christmas” or “Ten Tips for Rock Hard Abs” (that one doesn’t work by the way).

So with those headlines in mind I was tempted to headline our latest Board meeting as: “19 Big Stem Cell Ideas That Could Change Your Life!”. And in truth, some of them might.

The Board voted to invest more than $4 million in funding for 19 big ideas as part of CIRM’s Discovery Inception program. The goal of Inception is to provide seed funding for great, early-stage ideas that may impact the field of human stem cell research but need a little support to test if they work. If they do work out, the money will also enable the researchers to gather the data they’ll need to apply for larger funding opportunities, from CIRM and other institutions, in the future

The applicants were told they didn’t have to have any data to support their belief that the idea would work, but they did have to have a strong scientific rational for why it might

As our President and CEO Randy Mills said in a news release, this is a program that encourages innovative ideas.

Randy Mills, Stem Cell Agency President & CEO

Randy Mills, CIRM President & CEO

“This is a program supporting early stage ideas that have the potential to be ground breaking. We asked scientists to pitch us their best new ideas, things they want to test but that are hard to get funding for. We know not all of these will pan out, but those that do succeed have the potential to advance our understanding of stem cells and hopefully lead to treatments in the future.”

So what are some of these “big” ideas? (Here’s where you can find the full list of those approved for funding and descriptions of what they involve). But here are some highlights.

Alysson Muotri at UC San Diego has identified some anti-retroviral drugs – already approved by the Food and Drug Administration (FDA) – that could help stop inflammation in the brain. This kind of inflammation is an important component in several diseases such as Alzheimer’s, autism, Parkinson’s, Lupus and Multiple Sclerosis. Alysson wants to find out why and how these drugs helps reduce inflammation and how it works. If he is successful it is possible that patients suffering from brain inflammation could immediately benefit from some already available anti-retroviral drugs.

Stanley Carmichael at UC Los Angeles wants to use induced pluripotent stem (iPS) cells – these are adult cells that have been genetically re-programmed so they are capable of becoming any cell in the body – to see if they can help repair the damage caused by a stroke. With stroke the leading cause of adult disability in the US, there is clearly a big need for this kind of big idea.

Holger Willenbring at UC San Francisco wants to use stem cells to create a kind of mini liver, one that can help patients whose own liver is being destroyed by disease. The mini livers could, theoretically, help stabilize a person’s own liver function until a transplant donor becomes available or even help them avoid the need for liver transplantation in the first place. Considering that every year, one in five patients on the US transplant waiting list will die or become too sick for transplantation, this kind of research could have enormous life-saving implications.

We know not all of these ideas will work out. But all of them will help deepen our understanding of how stem cells work and what they can, and can’t, do. Even the best ideas start out small. Our funding gives them a chance to become something truly big.


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Stem cell stories that caught our eye: heart muscle-on-a-chip, your own private microliver, the bloody holy grail and selfish sperm

Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.

Two hearts beat as one, or not
Sorry for the pre-Valentine’s Day buzzkill but stem cell research published this past week points to a very unromantic discovery: two hearts do not beat as one. The study, out of Rockefeller University, and published in the Journal of Cell Biology, sought to understand the limited success of clinical trials in which stem cell-derived heart muscle cells, or cardiomyocytes, are transplanted into the heart to help repair tissue scarred by disease or a heart attack.

If you’re a regular at The Stem Cellar, you’ll recall that just last Friday we summarized published experiments that suggest the cardiomyocytes used in successful trials do not grow new tissue themselves but instead heal the heart indirectly by releasing proteins that stimulate repair.

The research team behind this week’s study instead reasoned that the transplanted cardiomyocytes do indeed integrate into the heart tissue, but they fail to contract properly with the undamaged heart cells. So, the thinking goes, the transplanted cells do nothing to restore the heart’s ability to beat at full strength.

Watch video here: http://medicalxpress.com/news/2016-02-muscles-on-a-chip-insight-cardiac-stem.html

A two-cell “microtissue” contains a mouse embryonic stem cell-derived cardiomyocyte and a mouse neonatal cardiomyocyte. The lower panel shows the traction forces generated as the two cells contract; the stronger, neonatal cardiomyocyte produces more force than the weaker, stem cell-derived cardiomyocyte. Credit: Aratyn-Schause, Y. et al. J Cell Biol. 2016 Watch video here: http://medicalxpress.com/news/2016-02-muscles-on-a-chip-insight-cardiac-stem.html

 

To test this hypothesis, the researchers devised a two-cell micro-tissue made up of a single mouse cardiomyocyte and a single cardiomyocyte derived from either mouse embryonic stem cells or induced pluripotent stem cells (iPS). This “muscle-on-a-chip” showed that the two cells are able to physically connect up and even beat in sync with each other. But, the embryonic and iPS-derived cardiomyocytes beat less strongly than the native cell. Based on computer simulations, this imbalance made the micro-tissue beat less efficiently. A university press release picked up by Newswise includes a short yet fascinating video of the differing strengths of the beating heart cells (click on image above).

With this micro-tissue in hand, the team aims to find a way to fix this imbalance, which hopefully would make cell therapies for heart disease more potent.

Your Own Private Micro-liver
Enough about micro-hearts, let’s talk micro-livers.

In a report published on Monday in PNAS, a multidisciplinary UCSD team of engineers and biomedical researchers described the creation of a bioprinted 3D liver model made from human iPS-derived liver cells, or hepatocytes. The hepatocytes are imprinted on a surface in hexagonal shapes, the kind seen in the complex microarchitecture of the human liver. These structures were also seeded with two other cell types: endothelial cells, which form blood vessels, and fat cells, which support the health of hepatocytes. Including these relevant cell types in the “micro-liver” design resulted in a 3D cell culture that not only mimics structures but also replicates functions found in a natural liver.

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The 3-D-printed parts of the biomimetic liver tissue include: liver cells derived from human induced pluripotent stem cells (left), endothelial and mesenchymal supporing cells (center), and the resulting organized combination of multiple cell types (right). — Chen Laboratory, UC San Diego

This is a really exciting development for improving drug safety. A big concern of any new drug coming on the market is its potential liver toxicity, formally known as DILI (drug induced liver injury), the most common cause of liver failure in the U.S. Although animal studies and clinical trials carefully test for the potential of DILI, that doesn’t guarantee the drug will be safe in all individuals. And because this liver model was designed using human iPS cells – which can be derived from anyone with a simple skin biopsy – it has the potential to serve as a personalized drug screening device as well as a disease-in-a-dish model for studying inherited forms of liver disease.

As Bradley Fikes, San Diego Union Tribune’s biotechnology writer, mentions in an excellent summary of the publication, beyond drug screening and disease-in-dish modeling, this bioprinting process could also one day make it possible for researchers to reach the “holy grail” of tissue engineering: building an entire organ.

Finally! The Bloody Holy Grail
While that holy grail remains on the horizon, Stanford researchers are nearly holding the goblet in their hands. Based on a Nature report published yesterday, a team led by CIRM grantee Irv Weissman have found a long sought after cellular tag that can fish out a very specific type of hematopoietic stem cell (HSC), or blood-forming stem cell, from bone marrow.

Almost thirty years ago, Weissman identified HSCs, which have the ability to form all the cell types of the blood. Since that time, scientists have struggled with fully understanding how HSCs are maintained in the body and, in turn, how to grow them in the laboratory.

The source of this problem is due to the fact that most HSCs are so-called short term HSCs because they eventually lose their “stemness”; that is, their ability to divide indefinitely. Only a small fraction of HSCs are of the long-term variety. To really understand how the body sustains a life-long supply of HSCs, it’s necessary to have a method to pick out just the long term HSCs.

So scientists in Weissman’s lab set out to do just that. Starting with a list of 100 genes that are known to be active in the bone marrow, they looked for genes that are turned on only in long term HSCs. After a painstaking, systematic method that took two years, the team narrowed down the list to just one gene that was unique to long term HSCs.

Co-lead author James Y. Chen, a MD/PHD candidate at Stanford, described the significance of this effort in a university press release:

chen

James Y. Chen

“For nearly 30 years, people have been trying to grow HSCs outside the body and have not been able to do it — it’s arguably the ‘holy grail’ in this field. Now that we have an anchor, a way to look at long-term HSCs, we can look at the cells around them to understand and, ideally, recreate the niche.”

 

 

 

Older Dads and The Selfish Sperm

We wrap up the week with a PNAS publication that got a wide range of coverage by the likes of BBC News, Gizmodo and Cosmos in addition to the usual suspects like Health Canal. Not too surprising given the topic including selfish sperm and chopped up testicles.

Research over the past decade or so has made it increasingly clear that biological clocks not only tick for would-be moms but also dads. At first glance, it makes sense: older fathers have had more time to accumulate random DNA mutations in their spermatogonia, the stem cells that produce sperm. But studies of Apert syndrome, a rare disease causing defects in the skull, fingers and toes, has put this hypothesis in question.

Back in 2003, a research team at Oxford University found the mutation in spermatogonia that causes Apert syndrome occurs 100 to 1000 times more frequently than would be expected if it were merely due to a random mutation (the Apert syndrome is not inherited because males with the disease rarely go on to have children).

So what’s going on? To answer that question the Oxford scientists collaborated with a USC research team who (men: you may not want to read the rest of this sentence, this is your only warning) chopped up human testicles – ones that had been removed for unrelated medical reasons and donated – in order to reconstruct a three-dimensional map of where these Apert syndrome mutations were occurring. If the mutations were merely random, the affected spermatogonia would have been evenly distributed throughout the testicle. Instead, the team found clusters of cells carrying the mutation.

This results confirms a “selfish sperm” hypothesis in which the mutation provides a selective advantage to the affected sperm cells allowing them to out compete other nearby sperm cells, much like a cancer cell that multiples and gradually forms a tumor. The study serves as more sobering news to otherwise healthy older dads that they may have a higher risk of passing on harmful mutations to their offspring.

Like I said, sorry for the buzzkill. Happy Valentine’s Day weekend!

The Stem Cell Bank is open for business

Creating a stem cell bank

Creating a stem cell bank

When you go to a bank and withdraw money you know that the notes you get are all going to look the same and do the same job, namely allow you to buy things. But when you get stem cells for research that’s not necessarily the case. Stem cells bought from different laboratories don’t always look exactly the same or perform the same in research studies.

That’s why CIRM has teamed up with the Coriell Institute and Cellular Dynamics International (CDI) to open what will be the world’s largest publically available stem cell bank. It officially opened today. In September the Bank will have 300 cell lines available for purchase but plans to increase that to 750 by February 2016.

300 lines but no waiting

Now, even if you are not in the market for stem cells this bank could have a big impact on your life because it creates an invaluable resource for researchers looking into the causes of, and potential therapies for, 11 different diseases including autism, epilepsy and other childhood neurological disorders, blinding eye diseases, heart, lung and liver diseases, and Alzheimer’s disease.

The goal of the Bank – which is located at the Buck Institute for Research on Aging in Novato, California – is to collect blood or tissue samples from up to 3,000 volunteer donors. Some of those donors have particular disorders – such as Alzheimer’s – and some are healthy. Those samples will then be turned into high quality iPSCs or induced pluripotent stem cells.

Now, iPSC lines are particularly useful for research because they can be turned into any type of cell in the body such as a brain cell or liver cell. And, because the cells are genetically identical to the people who donated the samples scientists can use the cells to determine how, for example, a brain cell from someone with autism differs from a normal brain cell. That can enable them to study how diseases develop and progress, and also to test new drugs or treatments against defects observed in those cells to see which, if any, might offer some benefits.

Power of iPSCs

In a news release Kaz Hirao, Chairman and CEO of CDI, says these could be game changers:

“iPSCs are proving to be powerful tools for disease modeling, drug discovery and the development of cell therapies, capturing human disease and individual genetic variability in ways that are not possible with other cellular models.”

Equally important is that researchers in different parts of the world will be able to compare their findings because they are using the same cell lines. Right now many researchers use cell lines from different sources so even though they are theoretically the same type of tissue, in practice they often produce very different results.

Improving consistency

CIRM Board Chair, Jonathan Thomas, said he hopes the Bank will lead to greater consistency in results.

“We believe the Bank will be an extraordinarily important resource in helping advance the use of stem cell tools for the study of diseases and finding new ways to treat them. While many stem cell efforts in the past have provided badly needed new tools for studying rare genetic diseases, this Bank represents both rare and common diseases that afflict many Californians. Stem cell technology offers a critical new approach toward developing new treatments and cures for those diseases as well.”

Most banks are focused on enriching your monetary account. This bank hopes to enrich people’s lives, by providing the research tools needed to unlock the secrets of different diseases, and pave the way for new treatments.

For more information on how to buy a cell line go to http://catalog.coriell.org/CIRM or email CIRM@Coriell.org