Lab-grown human sperm cells could unlock treatments for infertility

Dr. Miles Wilkinson: Photo courtesy UCSD

Out of 100 couples in the US, around 12 or 13 will have trouble starting a family. In one third of those cases the problem is male infertility (one third is female infertility and the other third is a combination of factors). In the past treatment options for men were often limited. Now a new study out of the University of California San Diego (UCSD) could help lead to treatments to help these previously infertile men have children of their own.

The study, led by Dr. Miles Wilkinson of UCSD School of Medicine, targeted spermatogonial stem cells (SSCs), which are the cells that develop into sperm. In the past it was hard to isolate these SSCs from other cells in the testes. However, using a process called single cell RNA sequencing – which is like taking a photo of all the gene expression happening in one cell at a precise moment – the team were able to identify the SSCs.

In a news release Dr. Wilkinson, the senior author of the study, says this is a big advance on previous methods: “We think our approach — which is backed up by several techniques, including single-cell RNA-sequencing analysis — is a significant step toward bringing SSC therapy into the clinic.”

Identifying the SSCs was just the first step. Next the team wanted to find a way to be able to take those cells and grow and multiply them in the lab, an important step in having enough cells to be able to treat infertility.

So, they tested the cells in the lab and identified something called the AKT pathway, which controls cell division and survival. By blocking the AKT pathway they were able to keep the SSCs alive and growing for a month. Next they hope to build on the knowledge and expand the cells for even longer so they could be used in a clinical setting.

This image has an empty alt attribute; its file name is wilkinson-ssc-graphic_450px.jpg
Illustrations by Vishaala Wilkinson

The hope is that this could ultimately lead to treatments for men whose bodies don’t produce sperm cells, or enough sperms cells to make them fertile. It could also help children going through cancer therapy which can destroy their ability to have children of their own later in life. By taking sperm cells and freezing them, they could later be grown and expanded in the lab and injected back into the testes to restore sperm production.

The study is published in the journal Proceedings of the National Academy of Science.

A recap on last week: two gut wrenching studies

Fluorescent pictures of a human colon organoid
Image credit: Dr Thierry Jarde

With everyone stocking up on food essentials this past week, it brings to mind the vital role that our stomach plays in order to properly digest these foods. This week, we wanted to share two separate studies related to aspects of the gut.

Promising results for a gut-related condition

Gastroparesis is a painful condition in which the stomach is unable to empty itself of food. Symptoms include heartburn, abdominal cramps, nausea, vomiting, and feeling full quickly when eating. In extremely severe cases, patients can experience dehydration, malnutrition and bezoars, a small stone-like matter that forms when food hardens and can block the opening from the stomach into the pylorus (small intestine).

A new study, led by Dr. Prabhash Dadhich and Dr. Khalil N Bitar at Wake Forest School of Medicine showed how a stem cell-combo therapy could bring long-term relief to these patients.

The team of scientists used interstitial cells of Cajal (ICCs), a type of stem cell found in the gastrointestinal tract, in combination with neural stem cells. An animal model similar to gastroparesis was then made using tissue from the small intestine of rats. The combination of stem cells were then injected into the small intestine tissue, where the cells were able to survive and integrate with host muscle layers.

In a news release, Dr. Bitar explains how this approach could potentially restore stomach muscle function and enable normal food digestion.

“Our analysis also confirmed the reinstatement and restoration of the stomach muscles’ functionality, both of which are critical in the treatment of pylorus dysfunctionality. These findings are very promising. We hope this study opens avenues for future cell-based clinical applications.”

The full study was published in Stem Cells Journals.

Superbug can damage stem cells in the gut

Clostridioides difficile (C. diff)
Image courtesy of the Central for Disease Control (CDC) website

A collaboration by the Monash Biomedicine Discovery Institute (BDI) has revealed that a bacterial superbug can prevent stem cells in the gut from regenerating the inner lining of the intestine.

Clostridioides difficile (C. diff) is a bacterial germ that is responsible for more than half of all hospital infections related to the gut and causes severe diarrhea. It usually grows after antibiotic treatment is administered to a patient.

The team of scientists found that C. diff damages stem cells in the colon, which in turn can cause problems with tissue repair and recovery.

In a press release, Professor Helen Abud, an expert in stem cell biology and one of the authors of this study, explains how this discovery can have wider implications.

“Our study provides the first direct evidence that a microbial infection alters the functional capacity of gut stem cells. It adds a layer of understanding about how the gut repairs after infection and why this superbug can cause the severe damage that it does. The reason it’s important to have that understanding is that we’re rapidly running out of antibiotics – we need to find other ways to prevent and treat these infections.”

The full results to this study were published in Proceedings of the National Academy of Sciences (PNAS).

Researchers create “xenobot” – world’s first living, self-healing robots created from frog stem cells

Artificial Intelligence methods automatically design diverse candidate lifeforms in simulation (top row) to perform some desired function, and transferable designs are then created using a cell-based construction toolkit to realize living systems (bottom row) with the predicted behaviors. Image credit: https://cdorgs.github.io/

The thought of microscopic robots brings the image of Hollywood blockbusters such as “Terminator” and other science-fiction movies to mind that are set years into the distant future. But a group of scientists have gotten one step closer to bringing these elements only seen on the big screen to reality.

Researchers at the University of Vermont and Tufts University were able to create what they call “xenobots” – the world’s first living, self healing robots created from frog stem cells. Named after the African clawed frog, Xenopus laevis, they are tiny blobs of moving cells made from stem cells obtained from frog embryos. They are less than a millimeter wide, making them small enough to travel inside the human body. Additionally, they have the ability to walk and swim, survive for weeks without food, and work together in groups.

Here is a brief video showing what these cells look like under the microscope:

The researchers were able take the stem cells from the embryo and increased their numbers by incubating them. After this, the cells were cut and rejoined using tiny forceps under a microscope into specific forms designed by artificial intelligence. These newly created forms are ones not found in nature and what is more remarkable is that they started working together. The skin cells bonded to form a structure while the heart cells worked together to create motion. These cells also displayed the ability to heal themselves after being cut.

In a news release from the University of Vermont, Dr. Josh Bongard, who co-led this research, described the xenobots in more detail.

“These are novel living machines. They’re neither a traditional robot nor a known species of animal. It’s a new class of artifact: a living, programmable organism.”

In the same news release, Dr. Michael Levin, who also co-led this research, talks about the possibilities these xenobots have for real world applications for a wide range of issues.

“We can imagine many useful applications of these living robots that other machines can’t do, like searching out nasty compounds or radioactive contamination, gathering microplastic in the oceans, traveling in arteries to scrape out plaque.”

The full results to this study was published in the Proceedings of the National Academy of Sciences (PNAS).

You can learn more about this work in the video below:

From organs to muscle tissue: how stem cells are being used in 3D

A Sunday Afternoon on the Island of La Grande Jatte by Georges-Pierre Seurat

When most people think of stem cells, they might conjure up an image of small dots under a microscope. It is hard to imagine these small specs being applied to three-dimensional structures. But like a pointillism painting, such as A Sunday Afternoon on the Island of La Grande Jatte by Georges-Pierre Seurat, stem cells can be used to help build things never thought possible. Two studies demonstrate this concept in very different ways.

MIT engineers have designed coiled “nanoyarn,” shown as an artist’s interpretation here. The twisted fibers are lined with living cells and may be used to repair injured muscles and tendons while maintaining their flexibility. Image by Felice Frankel

A study at MIT used nanofiber coated with muscle stem cells and mesenchymal stem cells in an effort to provide a flexible range of motion for these stem cells. Hundreds of thousands of nanofibers were twisted, resembling yarn and rope, in order to mimic the pattern found in tendons and muscle tissue throughout the body. The researchers at MIT found that the yarn like structure of the nanofibers keep the stem cells alive and growing, even as the team stretched and bent the fibers multiple times.

Normally, when a person injures these types of tissues, particularly around a major joint such as the shoulder or knee, it require surgery and weeks of limited mobility to heal properly. The MIT team hopes that their technology could be applied toward treating the site of injury while maintaining range of motion as the newly applied stem cells continue to grow to replace the injured tissue.

In an article, Dr. Ming Guo, assistant professor of mechanical engineering at MIT and one of the authors of the study, was quoted as saying,

“When you repair muscle or tendon, you really have to fix their movement for a period of time, by wearing a boot, for example. With this nanofiber yarn, the hope is, you won’t have to wearing anything like that.”

Their complete findings were published in the Proceedings of the National Academy of Sciences (PNAS).

Researchers in Germany have created transparent human organs using a new technology that could pave the way to print three-dimensional body parts such as kidneys for transplants. Above, Dr. Ali Ertuerk inspects a transparent human brain.
Photo courtesy of Reuters.

In a separate study, researchers in Germany have successfully created transparent human organs, paving the way to print three-dimensional body parts. Dr. Ali Erturk at Ludwig Maximilians University in Munich, with a team of scientists, developed a technique to create a detailed blueprint of organs, including blood vessels and every single cell in its specific location. These directions were then used to print a scaffold of the organ. With the help of a 3D printer, stem cells, acting like ink in a printer, were injected into the correct positions to make the organ functional.

Previously, 3D-printed organs lacked detailed cellular structures because they were based on crude images from computer tomography or MRI machines. This technology has now changed that.

In an article, Dr. Erturk is quoted as saying,

“We can see where every single cell is located in transparent human organs. And then we can actually replicate exactly the same, using 3D bioprinting technology to make a real functional organ. Therefore, I believe we are much closer to a real human organ for the first time now.”

Stem cell stories that caught our eye: update on Capricor’s heart attack trial; lithium on the brain; and how stem cells do math

Capricor ALLSTARToday our partners Capricor Therapeutics announced that its stem cell therapy for patients who have experienced a large heart attack is unlikely to meet one of its key goals, namely reducing the scar size in the heart 12 months after treatment.

The news came after analyzing results from patients at the halfway point of the trial, six months after their treatment in the Phase 2 ALLSTAR clinical trial which CIRM was funding. They found that there was no significant difference in the reduction in scarring on the heart for patients treated with donor heart-derived stem cells, compared to patients given a placebo.

Obviously this is disappointing news for everyone involved, but we know that not all clinical trials are going to be successful. CIRM supported this research because it clearly addressed an unmet medical need and because an earlier Phase 1 study had showed promise in helping prevent decline in heart function after a heart attack.

Yet even with this failure to repeat that promise in this trial,  we learned valuable lessons.

In a news release, Dr. Tim Henry, Director of the Division of Interventional Technologies in the Heart Institute at Cedars-Sinai Medical Center and a Co-Principal Investigator on the trial said:

“We are encouraged to see reductions in left ventricular volume measures in the CAP-1002 treated patients, an important indicator of reverse remodeling of the heart. These findings support the biological activity of CAP-1002.”

Capricor still has a clinical trial using CAP-1002 to treat boys and young men developing heart failure due to Duchenne Muscular Dystrophy (DMD).

Lithium gives up its mood stabilizing secrets

As far back as the late 1800s, doctors have recognized that lithium can help people with mood disorders. For decades, this inexpensive drug has been an effective first line of treatment for bipolar disorder, a condition that causes extreme mood swings. And yet, scientists have never had a good handle on how it works. That is, until this week.

evan snyder

Evan Snyder

Reporting in the Proceedings of the National Academy of Sciences (PNAS), a research team at Sanford Burnham Prebys Medical Discovery Institute have identified the molecular basis of the lithium’s benefit to bipolar patients.  Team lead Dr. Evan Snyder explained in a press release why his group’s discovery is so important for patients:

“Lithium has been used to treat bipolar disorder for generations, but up until now our lack of knowledge about why the therapy does or does not work for a particular patient led to unnecessary dosing and delayed finding an effective treatment. Further, its side effects are intolerable for many patients, limiting its use and creating an urgent need for more targeted drugs with minimal risks.”

The study, funded in part by CIRM, attempted to understand lithium’s beneficial effects by comparing cells from patient who respond to those who don’t (only about a third of patients are responders). Induced pluripotent stem cells (iPSCs) were generated from both groups of patients and then the cells were specialized into nerve cells that play a role in bipolar disorder. The team took an unbiased approach by looking for differences in proteins between the two sets of cells.

The team zeroed in on a protein called CRMP2 that was much less functional in the cells from the lithium-responsive patients. When lithium was added to these cells the disruption in CRMP2’s activity was fixed. Now that the team has identified the molecular location of lithium’s effects, they can now search for new drugs that do the same thing more effectively and with fewer side effects.

The stem cell: a biological calculator?

math

Can stem cells do math?

Stem cells are pretty amazing critters but can they do math? The answer appears to be yes according to a fascinating study published this week in PNAS Proceedings of the National Academy of Sciences.

Stem cells, like all cells, process information from the outside through different receptors that stick out from the cells’ outer membranes like a satellite TV dish. Protein growth factors bind those receptors which trigger a domino effect of protein activity inside the cell, called cell signaling, that transfers the initial receptor signal from one protein to another. Ultimately that cascade leads to the accumulation of specific proteins in the nucleus where they either turn on or off specific genes.

Intuition would tell you that the amount of gene activity in response to the cell signaling should correspond to the amount of protein that gets into the nucleus. And that’s been the prevailing view of scientists. But the current study by a Caltech research team debunks this idea. Using real-time video microscopy filming, the team captured cell signaling in individual cells; in this case they used an immature muscle cell called a myoblast.

goentoro20170508

Behavior of cells over time after they have received a Tgf-beta signal. The brightness of the nuclei (circled in red) indicates how much Smad protein is present. This brightness varies from cell to cell, but the ratio of brightness after the signal to before the signal is about the same. Image: Goentoro lab, CalTech.

To their surprise the same amount of growth factor given to different myoblasts cells led to the accumulation of very different amounts of a protein called Smad3 in the cells’ nuclei, as much as a 40-fold difference across the cells. But after some number crunching, they discovered that dividing the amount of Smad3 after growth factor stimulation by the Smad3 amount before growth stimulation was similar in all the cells.

As team lead Dr. Lea Goentoro mentions in a press release, this result has some very important implications for studying human disease:

“Prior to this work, researchers trying to characterize the properties of a tumor might take a slice from it and measure the total amount of Smad in cells. Our results show that to understand these cells one must instead measure the change in Smad over time.”

Scientists make stem cell-derived nerve cells damaged in spinal cord injury

The human spinal cord is an information highway that relays movement-related instructions from the brain to the rest of the body and sensory information from the body back to the brain. What keeps this highway flowing is a long tube of nerve cells and support cells bundled together within the spine.

When the spinal cord is injured, the nerve cells are damaged and can die – cutting off the flow of information to and from the brain. As a result, patients experience partial or complete paralysis and loss of sensation depending on the extent of their injury.

Unlike lizards which can grow back lost tails, the spinal cord cannot robustly regenerate damaged nerve cells and recreate lost connections. Because of this, scientists are looking to stem cells for potential solutions that can rebuild injured spines.

Making spinal nerve cells from stem cells

Yesterday, scientists from the Gladstone Institutes reported that they used human pluripotent stem cells to create a type of nerve cell that’s damaged in spinal cord injury. Their findings offer a new potential stem cell-based strategy for restoring movement in patients with spinal cord injury. The study was led by Gladstone Senior Investigator Dr. Todd McDevitt, a CIRM Research Leadership awardee, and was published in the journal Proceedings of the National Academy of Sciences.

The type of nerve cell they generated is called a spinal interneuron. These are specialized nerve cells in the spinal cord that act as middlemen – transporting signals between sensory neurons that connect to the brain to the movement-related, or motor, neurons that connect to muscles. Different types of interneurons exist in the brain and spinal cord, but the Gladstone team specifically created V2a interneurons, which are important for controlling movement.

V2a interneurons extend long distances in the spinal cord. Injuries to the spine can damage these important cells, severing the connection between the brain and the body. In a Gladstone news release, Todd McDevitt explained why his lab is particularly interested in making these cells to treat spinal cord injury.

Todd McDevitt, Gladstone Institutes

“Interneurons can reroute after spinal cord injuries, which makes them a promising therapeutic target. Our goal is to rewire the impaired circuitry by replacing damaged interneurons to create new pathways for signal transmission around the site of the injury.”

 

Transplanting nerve cells into the spines of mice

After creating V2a interneurons from human stem cells using a cocktail of chemicals in the lab, the team tested whether these interneurons could be successfully transplanted into the spinal cords of normal mice. Not only did the interneurons survive, they also set up shop by making connections with other nerve cells in the spinal cord. The mice that received the transplanted cells didn’t show differences in their movement suggesting that the transplanted cells don’t cause abnormalities in motor function.

Co-author on the paper, Dylan McCreedy, described how the transplanted stem cell-derived cells behaved like developing V2a interneurons in the spine.

“We were very encouraged to see that the transplanted cells sprouted long distances in both directions—a key characteristic of V2a interneurons—and that they started to connect with the relevant host neurons.”

Todd McDevitt (right), Jessica Butts (center) and Dylan McCreedy (left) created a special type of neuron from human stem cells that could potentially repair spinal cord injuries. (Photo: Chris Goodfellow, Gladstone)

A new clinical strategy?

Looking forward, the Gladstone team plans to test whether these V2a interneurons can improve movement in mice with spinal cord injury. If results look promising in mice, this strategy of transplanting V2a interneurons could be translated into human clinic trials although much more time and research are needed to get there.

Trials testing stem cell-based treatments for spinal cord injury are already ongoing. Many of them involve transplanting progenitor cells that develop into the different types of cells in the spine, including nerve and support cells. These progenitor cells are also thought to secrete important growth factors that help regenerate damaged tissue in the spine.

CIRM is funding one such clinical trial sponsored by Asterias Biotherapeutics. The company is transplanting oligodendrocyte progenitor cells (which make nerve support cells called oligodendrocytes) into patients with severe spinal cord injuries in their neck. The trial has reported encouraging preliminary results in all six patients that received a dose of 10 million cells. You can read more about this trial here.

What the Gladstone study offers is a different stem cell-based strategy for treating spinal cord injury – one that produces a specific type of spinal nerve cell that can reestablish important connections in the spinal cord essential for movement.

For more on this study, watch the Gladstone’s video abstract “Discovery Offers New Hope to Repair Spinal Cord.


Related Links:

Using stem cells to fix bad behavior in the brain

 

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Gladstone Institutes Steven Finkbeiner and Gaia Skibinski: Photo courtesy Chris Goodfellow, Gladstone Institutes

Diseases of the brain have many different names, from Alzheimer’s and Parkinson’s to ALS and Huntington’s, but they often have similar causes. Researchers at the Gladstone Institutes in San Francisco are using that knowledge to try and find an approach that might be effective against all of these diseases. In a new CIRM-funded study, they have identified one protein that could help do just that.

Many neurodegenerative diseases are caused by faulty proteins, which start to pile up and cause damage to neurons, the brain cells that are responsible for processing and transmitting information. Ultimately, the misbehaving proteins cause those cells to die.

The researchers at the Gladstone found a way to counter this destructive process by using a protein called Nrf2. They used neurons from humans (made from induced pluripotent stem cells – iPSCs – hence the stem cell connection here) and rats. They then tested these cells in neurons that were engineered to have two different kinds of mutations found in  Parkinson’s disease (PD) plus the Nrf2 protein.

Using a unique microscope they designed especially for this study, they were able to track those transplanted neurons and monitor what happened to them over the course of a week.

The neurons that expressed Nrf2 were able to render one of those PD-causing proteins harmless, and remove the other two mutant proteins from the brain cells.

In a news release to accompany the study in The Proceedings of the National Academy of Sciences, first author Gaia Skibinski, said Nrf2 acts like a house-cleaner brought in to tidy up a mess:

“Nrf2 coordinates a whole program of gene expression, but we didn’t know how important it was for regulating protein levels until now. Over-expressing Nrf2 in cellular models of Parkinson’s disease resulted in a huge effect. In fact, it protects cells against the disease better than anything else we’ve found.”

Steven Finkbeiner, the senior author on the study and a Gladstone professor, said this model doesn’t just hold out hope for treating Parkinson’s disease but for treating a number of other neurodegenerative problems:

“I am very enthusiastic about this strategy for treating neurodegenerative diseases. We’ve tested Nrf2 in models of Huntington’s disease, Parkinson’s disease, and ALS, and it is the most protective thing we’ve ever found. Based on the magnitude and the breadth of the effect, we really want to understand Nrf2 and its role in protein regulation better.”

The next step is to use this deeper understanding to identify other proteins that interact with Nrf2, and potentially find ways to harness that knowledge for new therapies for neurodegenerative disorders.