Stem Cell Roundup: The brain & obesity; iPSCs & sex chromosomes; modeling mental illness

Stem Cell Image of the Week:
Obesity-in-a-dish reveals mutations and abnormal function in nerve cells

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Image shows two types of hypothalamic neurons (in magenta and cyan) that were derived from human induced pluripotent stem cells.
Credit: Cedars-Sinai Board of Governors Regenerative Medicine Institute

Our stem cell image of the week looks like the work of a pre-historic cave dweller who got their hands on some DayGlo paint. But, in fact, it’s a fluorescence microscopy image of stem cell-derived brain cells from the lab of Dhruv Sareen, PhD, at Cedars-Sinai Medical Center. Sareen’s team is investigating the role of the brain in obesity. Since the brain is a not readily accessible organ, the team reprogrammed skin and blood cell samples from severely obese and normal weight individuals into induced pluripotent stem cells (iPSCs). These iPSCs were then matured into nerve cells found in the hypothalamus, an area of the brain that regulates hunger and other functions.

A comparative analysis showed that the nerve cells derived from the obese individuals had several genetic mutations and had an abnormal response to hormones that play a role in telling our brains that we are hungry or full. The Cedars-Sinai team is excited to use this obesity-in-a-dish system to further explore the underlying cellular changes that lead to excessive weight gain. Ultimately, these studies may reveal ways to combat the ever-growing obesity epidemic, as Dr. Sareen states in a press release:

“We are paving the way for personalized medicine, in which drugs could be customized for obese patients with different genetic backgrounds and disease statuses.”

The study was published in Cell Stem Cell

Differences found in stem cells derived from male vs female.

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Microscope picture of a colony of iPS cells. Credit: Vincent Pasque

Scientists at UCLA and KU Leuven University in Belgium carried out a study to better understand the molecular mechanisms that control the process of reprogramming adult cells back into the embryonic stem cell-like state of induced pluripotent stem cells (iPSCs). Previous studies have shown that female vs male embryonic stem cells have different patterns of gene regulation. So, in the current study, male and female cells were analyzed side-by-side during the reprogramming process.  First author Victor Pasquale explained in a press release that the underlying differences stemmed from the sex chromosomes:

In a normal situation, one of the two X chromosomes in female cells is inactive. But when these cells are reprogrammed into iPS cells, the inactive X becomes active. So, the female iPS cells now have two active X chromosomes, while males have only one. Our results show that studying male and female cells separately is key to a better understanding of how iPS cells are made. And we really need to understand the process if we want to create better disease models and to help the millions of patients waiting for more effective treatments.”

The CIRM-funded study was published in Stem Cell Reports.

Using mini-brains and CRISPR to study genetic linkage of schizophrenia, depression and bipolar disorder.

If you haven’t already picked up on a common thread in this week’s stories, this last entry should make it apparent: iPSC cells are the go-to method to gain insight in the underlying mechanisms of a wide range of biology topics. In this case, researchers at Brigham and Women’s Hospital at Harvard Medical School were interested in understanding how mutations in a gene called DISC1 were linked to several mental illnesses including schizophrenia, bipolar disorder and severe depression. While much has been gleaned from animal models, there’s limited knowledge of how DISC1 affects the development of the human brain.

The team used human iPSCs to grow cerebral organoids, also called mini-brains, which are three-dimensional balls of cells that mimic particular parts of the brain’s anatomy. Using CRISPR-Cas9 gene-editing technology – another very popular research tool – the team introduced DISC1 mutations found in families suffering from these mental disorders.

Compared to cells with normal copies of the DISC1 gene, the mutant organoids showed abnormal structure and excessive cell signaling. When an inhibitor of that cell signaling was added to the growing mutant organoids, the irregular structures did not develop.

These studies using human cells provide an important system for gaining a better understanding of, and potentially treating, mental illnesses that victimize generations of families.

The study was published in Translation Psychiatry and picked up by Eureka Alert.

Stories that caught our eye: Spinal cord injury trial milestone, iPS for early cancer diagnosis, and storing videos in DNA

Spinal cord injury clinical trial hits another milestone (Kevin McCormack)
We began the week with good news about our CIRM-funded clinical trial with Asterias for spinal cord injury, and so it’s nice to end the week with more good news from that same trial. On Wednesday, Asterias announced it had completed enrolling and dosing patients in their AIS-B 10 million cell group.

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People with AIS-B spinal cord injuries have some level of sensation and feeling but very little, if any, movement below the site of injury site. So for example, spinal cord injuries at the neck, would lead to very limited movement in their arms and hands. As a result, they face a challenging life and may be dependent on help in performing most daily functions, from getting out of bed to eating.astopc1

In another branch of the Asterias trial, people with even more serious AIS-A injuries – in which no feeling or movement remains below the site of spinal cord injury – experienced improvements after being treated with Asterias’ AST-OPC1 stem cell therapy. In some cases the improvements were quite dramatic. We blogged about those here.

In a news release Dr. Ed Wirth, Asterias’ Chief Medical Officer, said they hope that the five people treated in the AIS-B portion of the trial will experience similar improvements as the AIS-A group.

“Completing enrollment and dosing of the first cohort of AIS-B patients marks another important milestone for our AST-OPC1 program. We have already reported meaningful improvements in arm, hand and finger function for AIS-A patients dosed with 10 million AST-OPC1 cells and we are looking forward to reporting initial efficacy and safety data for this cohort early in 2018.”

Asterias is already treating some AIS-A patients with 20 million cells and hopes to start enrolling AIS-B patients for the 20 million cell therapy later this summer.

Earlier diagnosis of pancreatic cancer using induced pluripotent stem cells Reprogramming adult cells to an embryonic stem cell-like state is as common in research laboratories as hammers and nails are on a construction site. But a research article in this week’s edition of Science Translational Medicine used this induced pluripotent stem cell (iPSC) toolbox in a way I had never read about before. And the results of the study may lead to earlier detection of pancreatic cancer, the fourth leading cause of cancer death in the U.S.

Zaret STM pancreatic cancer tissue July 17

A pancreatic ductal adenocarcinoma
Credit: The lab of Ken Zaret, Perelman School of Medicine, University of Pennsylvania

We’ve summarized countless iPSCs studies over the years. For example, skin or blood samples from people with Parkinson’s disease can be converted to iPSCs and then specialized into brain cells to provide a means to examine the disease in a lab dish. The starting material – the skin or blood sample – typically has no connection to the disease so for all intents and purposes, it’s a healthy cell. It’s only after specializing it into a nerve cell that the disease reveals itself.

But the current study by researchers at the University of Pennsylvania used late stage pancreatic cancer cells as their iPSC cell source. One of the reasons pancreatic cancer is thought to be so deadly is because it’s usually diagnosed very late when standard treatments are less effective. So, this team aimed to reprogram the cancer cells back into an earlier stage of the cancer to hopefully find proteins or molecules that could act as early warning signals, or biomarkers, of pancreatic cancer.

Their “early-stage-cancer-in-a-dish” model strategy was a success. The team identified a protein called thrombospodin-2 (THBS2) as a new candidate biomarker. As team lead, Dr. Ken Zaret, described in a press release, measuring blood levels of THBS2 along with a late-stage cancer biomarker called CA19-9 beat out current detection tests:

“Positive results for THBS2 or CA19-9 concentrations in the blood consistently and correctly identified all stages of the cancer. Notably, THBS2 concentrations combined with CA19-9 identified early stages better than any other known method.”

DNA: the ultimate film archive device?
This last story for the week isn’t directly related to stem cells but is too cool to ignore. For the first time ever, researchers at Harvard report in Nature that they have converted a video into a DNA sequence which was then inserted into bacteria. As Gina Kolata states in her New York Times article about the research, the study represents the ultimate data archive system which can “be retrieved at will and multiplied indefinitely as the host [bacteria] divides and grows.”

A video file is nothing but a collection of “1s” and “0s” of binary code which describe the makeup of each pixel in each frame of a movie. The researchers used the genetic code within DNA to describe each pixel in a short clip of one of the world’s first motion pictures: a galloping horse captured by Eadward Muybridge in 1878.

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The resulting DNA sequence was then inserted into the chromosome of E.Coli., a common bacteria that lives in your intestines, using the CRISPR gene editing method. The video code was still retrievable after the bacteria was allowed to multiply.

The Harvard team envisions applications well beyond a mere biological hard drive. Dr. Seth Shipman, an author of the study, told Paul Rincon of BBC news that he thinks this cell system could be placed in various parts of the body to analyze cell function and “encode information about what’s going on in the cell and what’s going on in the cell environment by writing that information into their own genome”.

Perhaps then it could be used to monitor the real-time activity of stem cell therapies inside the body. For now, I’ll wait to hear about that in some upcoming science fiction film.

Scientists Reach Yet Another Milestone towards Treating Type 1 Diabetes

There was a time when having type 1 diabetes was equivalent to a death sentence. Now, thanks to advances in science and medicine, the disease has shifted from deadly to chronic.

But this shift, doctors argue, is not good enough. The disease still poses significant health risks, such as blindness and loss of limbs, as the patients get older. There has been a renewed effort, therefore, to develop superior therapies—and those based on stem cell technology have shown significant promise.

Human stem cell-derived beta cells that have formed islet like clusters in a mouse. Cells were transplanted to the kidney capsule and photo was taken two weeks later by which time the beta cells are making insulin and have cured the mouse's diabetes. [Credit: Douglas Melton]

Human stem cell-derived beta cells that have formed islet like clusters in a mouse. Cells were transplanted to the kidney capsule and photo was taken two weeks later by which time the beta cells are making insulin and have cured the mouse’s diabetes. [Credit: Douglas Melton]

Indeed, CIRM-funded scientists at San Diego-based Viacyte, Inc. recently received FDA clearance to begin clinical trials of their VC-01 product candidate that delivers insulin via healthy beta cells contained in a permeable, credit card-sized pouch.

And now, scientists at Harvard University have announced a technique for producing mass quantities of mature beta cells from embryonic stem cells in the lab. The findings, published today in the journal Cell, offer additional hope for the millions of patients and their families looking for a better way to treat their condition.

The team’s ability to generate billions of healthy beta cells—cells within the pancreas that produce insulin in order to maintain normal glucose levels—has a particular significance to the study’s senior author and co-scientific director of the Harvard Stem Cell Institute, Dr. Doug Melton. 23 years ago, his infant son Sam was diagnosed with type 1 diabetes and since that time Melton has dedicated his career to finding better therapies for his son and the millions like him. Melton’s daughter, Emma, has also been diagnosed with the disease.

Type 1 diabetes is an autoimmune disorder in which the body’s immune system systematically targets and destroys the pancreas’ insulin-producing beta cells.

In this study, the team took human embryonic stem cells and transformed them into healthy beta cells. They then transplanted them into mice that had been modified to mimic the signs of diabetes. After closely monitoring the mice for several weeks, they found that their diabetes was essentially ‘cured.’ Said Melton:

“You never know for sure that something like this is going to work until you’ve tested it numerous ways. We’ve given these cells three separate challenges with glucose in mice and they’ve responded appropriately; that was really exciting.”

The researchers are undergoing additional pre-clinical studies in animal models, including non-human primates, with the hopes that the 150 million cells required for transplantation are also protected from the body’s immune system, and not destroyed.

Melton’s team is collaborating with Medical Engineer Dr. Daniel G. Anderson at MIT to develop a protective implantation device for transplantation. Said Anderson of Melton’s work:

“There is no question that the ability to generate glucose-responsive, human beta cells through controlled differentiation of stem cells will accelerate the development of new therapeutics. In particular, this advance opens the doors to an essentially limitless supply of tissue for diabetic patients awaiting cell therapy.”