100% Reprogramming Rates


For the first time, stem cell scientists have reprogrammed cultured skin cells into induced pluripotent cells (iPSCs) with near-perfect efficiency.

Even several laboratories have examined protocols to increase the efficiency of cellular reprogramming, a research team at the Weizmann Institute of Science in Rehovot, Israel has managed to increase the conversion rate to almost 100%, ten times the rate normally achieved, by removing a single proteins called Mbd3. This discovery can potentially allow scientists to generate large volumes of stem cells on demand, which would accelerate the development of new treatments.

In 2006, scientists from the laboratory of Shinya Yamanaka showed that mature cells could be reprogrammed to act like embryonic stem cells (ESCs). These reprogrammed adult cells could grow in culture indefinitely and differentiate into any type of cell in the body. However the creation of iPSc lines was notoriously inefficient and labor-intensive. Low cell-conversion rates have slowed the study of the reprogramming process itself. It has also discouraged the development of protocols for producing iPSCs under GMP or “Good Manufacturing Practice” conditions for use in human patients.

However, in a series of experiments that were published in the journal Nature, Weizmann Institute stem-cell researcher Jacob Hanna and his team have reprogrammed cells with nearly 100% efficiency. Moreover, Hanna and his group showed that reprogrammed cells transition to pluripotency on a synchronized schedule.

“This is the first report showing that you can make reprogramming as efficient as anyone was hoping for,” says Konrad Hochedlinger, a stem-cell scientist at Harvard Medical School in Boston, Massachusetts. “It is really surprising that manipulating a single molecule is sufficient to make this switch, and make essentially every single cell pluripotent within a week.”

To make iPSCs from adult cells, scientists typically transfect them with a set of four genes. These genes turn on the cells’ own pluripotency program, which converts them into iPSCs. But even established techniques convert less than 1% of cultured cells. Many cells get stuck in a partially reprogrammed state, and some become pluripotent faster than others, which makes the whole reprogramming process difficult to monitor.

Hanna and his team investigated the potential roadblocks to reprogramming by working with a line of genetically-engineered mouse cells. In these cells, the reprogramming genes were already inserted into the genomes of the cells and could be activated with a small molecule. Such cells normally reprogram at rates below 10%. But when a gene responsible for producing the protein Mbd3 was repressed, reprogramming rates soared to nearly 100%.

Hanna says that the precise timing of embryonic development led him to wonder whether it is possible to “reprogram the reprogramming process.” Cells in an embryo do not remain pluripotent indefinitely, explained Hanna. Usually, Mbd3 represses the pluripotency program as an embryo develops, and mature cells maintain their expression of Mbd3. However, during cellular reprogramming, those proteins expressed from the inserted pluripotency genes induce Mbd3 to repress the cells’ own pluripotency genes.

This hamstrings reprogramming, says Hanna. “It creates a clash, and that’s why the process is random and stochastic. It’s trying to have the gas and brakes on at the same time.” Depleting the cells of Mbd3 allows reprogramming to proceed unhindered.

The team also reprogrammed cells from a human, using a method that does not require inserting extra genes. This technique usually requires daily doses of RNA over more than two weeks. With Mbd3 repressed, only two doses were required.

Stem Cells and LDL Play a Role in Atherosclerosis


Researchers at the University at Buffalo have discovered a new understanding of atherosclerosis in humans that include a key role for stem cells that promote inflammation.

Published in the journal PLOS One, this work extends to humans previous findings in lab animals by researchers at Columbia University that showed that high levels of LDL (“bad”) cholesterol promote atherosclerosis by stimulating production of hematopoietic stem/progenitor cells (HSPC’s).

“Our research opens up a potential new approach to preventing heart attack and stroke, by focusing on interactions between cholesterol and the HSPCs,” says Thomas Cimato, lead author on the PLOS One paper and assistant professor in the Department of Medicine in the UB School of Medicine and Biomedical Sciences.

Cimato noted that the role of stem cells in atherosclerosis could lead to the development of a useful therapy in combination with statins or to a novel therapy that could be used in place of statins for those individuals who cannot tolerate them.

In humans, high total cholesterol recruits stem cells from the bone marrow into the bloodstream. The cytokine IL-17, which has been implicated in many chronic inflammatory diseases, including atherosclerosis, is responsible for the recruitment of HSPCs. IL-17 boosts levels of granulocyte colony stimulating factor (GCSF), which induces the release of stem cells from the bone marrow.

According to Cimato, they observed that statins reduce the levels of HSPCs in the blood but not every subject responded similarly. “We’ve extrapolated to humans what other scientists previously found in mice about the interactions between LDL cholesterol and these HSPCs,” explains Cimato.

The fact that a finding in laboratory animals holds true for humans is noteworthy, adds Cimato. “This is especially true with cholesterol studies,” he says, “because mice used for atherosclerosis studies have very low total cholesterol levels at baseline. We feed them very high fat diets in order to study high cholesterol but it isn’t [sic] easy to interpret what the levels in mice will mean in humans and you don’t know if extrapolating to humans will be valid.”

Cimato added that the LDL concentrations in the blood of mice in their studies is much higher than what is found in patients who come to the hospital with a heart attack or stroke.

“The fact that this connection between stem cells and LDL cholesterol in the blood that was found in mice also turns out to be true in humans is quite remarkable,” he says.

Cimato explains that making the jump from rodents with very high LDL cholesterol to humans required some creative steps, such as the manipulation of the LDL cholesterol levels of subjects through the use of three different kinds of statins.

The study involved monitoring for about a year a dozen people without known coronary artery disease who were on the statins for two-week periods separated by one-month intervals when they were off the drugs.

“We modeled the mechanism of how LDL cholesterol affects stem cell mobilization in humans,” says Cimato.

Cimato and his group found that LDL cholesterol modulates the levels of stem cells that form neutrophils, monocytes and macrophages, the primary cell types involved in the formation of plaque and atherosclerosis.

The next step, he says, is to find out if HSPCs, like LDL cholesterol levels, are connected to cardiovascular events, such as heart attack and stroke.

Biphasic Electrical Stimulation Increases Stem Cell Survival


One of the challenges of stem cell-based therapies is cell survival. Once stem cells are implanted into a foreign site, many of them tend to pack up and die before they can do any good. For this reason, many scientists have examined strategies to improve stem cell survival.

A new technique that improves stem cells survival have been discovered by Yubo Fan and his colleagues at Beihang University School of Biological Science and Medical Engineering. This non-chemical technique, biphasic electrical stimulation (BES) might become important for spinal cord injury patients in the near future.

The BES incubation system. (a) Schematic diagram of a longitudinal section of the incubation chamber including: the upper and lower electric conductive glass plates (FTO glass), a closed silicone gasket, the incubation chamber, and a pair of electrode wires; (b) Schematic diagram of a longitudinal section of the entire BES incubation system including the incubation chamber, the fluid inflow-outflow system, the air filter system, a pair of electrode wires, and a fixed cover and base. Conditions of BES: the NPCs were exposed to 12 h of BES at 25mV/mm and 50mV/mm electric field strengths with a pulse-burst pattern and 8ms pulses (20% duty cycle). Cells that were not exposed to BES served as controls. (A color version of this figure is available in the online journal)
The BES incubation system. (a) Schematic diagram of a longitudinal
section of the incubation chamber including: the upper and lower electric  conductive glass plates (FTO glass), a closed silicone gasket, the incubation
chamber, and a pair of electrode wires; (b) Schematic diagram of a longitudinal
section of the entire BES incubation system including the incubation chamber,
the fluid inflow-outflow system, the air filter system, a pair of electrode wires, and
a fixed cover and base. Conditions of BES: the NPCs were exposed to 12 h of
BES at 25mV/mm and 50mV/mm electric field strengths with a pulse-burst
pattern and 8ms pulses (20% duty cycle). Cells that were not exposed to BES
served as controls. 

Spinal cord injury affects approximately 250,000 Americans, with 52% being paraplegic and 47% quadriplegic. There are 11,000 new spinal cord injuries each year and 82% are male.

Stem cell transplantions into the spinal cord to regenerate severed neurons and associated cells provides a potentially powerful treatment. However, once stem cells are implanted into the injured spinal cord, many of them die. Cell death is probably a consequence of several factors such as a local immune response, hypoxia (lack of oxygen), and probably most importantly, limited quantities of growth factors.

Fan said of his work, “We’ve shown for the very first time that BES may provide insight into preventing growth factor deprivation-triggered apoptosis in olfactory bulb precursor cells. These findings suggest that BES may thus be used as a strategy to improve cell survival and prevent cell apoptosis (programmed cell death) in stem cell-based transplantation therapies.”

The olfactory bulb is in green in this mouse brain.
The olfactory bulb is in green in this mouse brain.

Since electrical stimulation dramatically accelerates the speed of axonal regeneration and target innervation and positively modulates the functional recovery of injured nerves, Fan decided to test BES. His results showed that BES upregulated all the sorts of responses in stem cells that you would normally see with growth factors. Thus BES can increase stem cell survival without exogenous chemicals or genetic engineering.

Fan and his team examined the effects of BES on olfactory bulb neural precursor cells and they found that 12 hours of BES exposure protected cells from dying after growth factor deprivation. How did BES do this? Fan and other showed that BES stimulated a growth factor pathway called the PI3K/Akt signaling cascade. BES also increase the output of brain-derived neurotrophic factor.

“What was especially surprising and exciting,” said Fan, “was that a non-chemical procedure can prevent apoptosis in stem cell therapy for spinal cord patients.” Fan continued: “How BES precisely regulates the survival of exogenous stem cells is still unknown but will be an extremely novel area of research on spinal cord injury in the future.”

BES alters the ultrastructure of NPCs. The ultrastructural morphological changes of cells were investigated by TEM. In the control group (unstimulated), cells had a necrotic appearance: most cells lost the normal cellular structure with a consequent release of cell contents. In the 25mV/mm and 50mV/mm BES groups, the NPCs showed an apoptotic morphology with nuclear fragmentation and condensation
BES alters the ultrastructure of NPCs. The ultrastructural morphological changes of cells were investigated by TEM. In the control group (unstimulated), cells had a necrotic appearance: most cells lost the normal cellular structure with a consequent release of cell contents. In the 25mV/mm and 50mV/mm BES groups, the NPCs showed an apoptotic morphology with nuclear fragmentation and condensation

BES can improve the survival of neural precursor cells and will provide the survival of neural precursor cells and will provide the basis or future studies that could lead to novel therapies for patients with spinal cord injury.

Cardiac Muscle Repair with Molecular Beacons


Pure heart muscle cells that are ready for transplantation. This is one of the Holy Grails of regenerative medicine. Of course when working with pluripotent stem cell lines, isolating nothing but beating heart muscle cells is rather difficult. A new technique makes the isolation of pure cultures of beating heart muscle cells that much easier.

Researchers at Emory and Georgia Tech have developed a method that utilizes molecules called “molecular beacons” to isolate heart muscle cells from pluripotent stem cells. Molecular beacons fluoresce when they come into contact with cells that express certain genes. In this case, the beacons target cells that express heart-specific myosin.

Physicians can use these purified cardiac muscle cells to heal damaged areas of the heart in patient that have suffered a heart attack or are suffering heart failure. This molecular beacon technique might also have applications in other fields of regenerative medicine as well.

“Often, we want to generate a particular cell population from stem cells for introduction into patients,” said Young-sup Yoon, professor of medicine and director for stem cell biology at Emory University School of Medicine. “But the desired cells often lack a readily accessible surface marker, or that marker is not specific enough, as is the case for cardiac muscle cells. This technique could allow us to purify almost any type of cell.”

Gang Bao pioneered he use of molecular beacons and was a co-author of this publication. Yoon and is colleagues and collaborators grew mouse and human embryonic stem cells and induced pluripotent stem cells and differentiated them into heart muscle cells (cardiomyocytes). They then used molecular beacons to label only those cells that expressed messenger RNAs with just the right sequences. These molecular beacons hybridized with the mRNAs and fluoresced. Bao and others then used flow cytometry to sort the fluorescent cells from the non- fluorescent cells. The fluorescent cells have differentiated into heart muscle cells and were isolated from all the other cells.

These purified heart muscle cells could engraft into the heart of a mouse that had suffered a heart attack and they improved heart function and formed no tumors. This proof-of-principle experiment shows that this technique is feasible.

“In previous experiments with injected bare cells, investigators at Emory and elsewhere found that a large proportion of the cells are washed away. We need to engineer the cells into compatible biomaterials to enhance engraftment and retention,” said Yoon,

Spiking Stem Cells to Generate Myelin


Regenerating damaged nerve tissue represents a unique challenge for regenerative medicine. Nevertheless, some experiments have shown that it is possible to regenerate the myelin sheath that surrounds particular nerves.

Myelin is a fatty, insulating sheath that surrounds particular nerves and accelerates the transmission of nerve impulses. The myelin sheath also helps neurons survive, and the myelin sheath is attacked and removed in multiple sclerosis, a genetic disease called Charcot-Marie-Tooth disease, and spinal cord injuries. Being able to regenerate the myelin sheath is an essential goal of regenerative medicine.

Fortunately, a new study from a team of UC Davis (my alma mater) scientists have brought this goal one step closer. Wenbig Deng, principal investigator of this study and associate professor of biochemistry and molecular medicine, said, “Our findings represent an important conceptual advance in stem cell research. We have bioengineered the first generation of myelin-producing cells with superior regenerative capacity.”

The brain contains two main cell types; neurons and glial cells. Neurons make and transmit nerve impulses whereas glial cells support, nourish and protect neurons. One particular subtype of glial cells, oligodendrocytes, make the myelin sheath that surrounds the axons of many neurons. Deng and his group developed a novel protocol to induce embryonic stem cells (ESCs) to differentiate into oligodendrocyte precursor cells or OPCs. Even though other researchers have made oligodenrocytes from ESCs, Deng’s method results in purer populations of OPCs than any other available method.

Making OPCs from ESCs is one thing, but can these laboratory OPCs do everything native can do? When Deng and his team tested the electrophysiological properties of their laboratory-made OPCs, they discovered that their cells lacked an important component; they did not express sodium channels. When the lab-made OPCs were genetically engineered to express sodium channels, they generated the characteristic electrical spikes that are common to native OPCs. According to Deng, this is the first time anyone has made OPCs in the laboratory with spiking properties. Is this significant?

Deng and his colleagues compared the spiking OPCs to non-spiking OPCs in the laboratory. Not only did the spiking OPCs communicate with neurons, but they also did a better job of maturing into oligodentrocytes.

Transplantation of these two OPC populations into the spinal cord and brains of mice that are genetically unable to produce myelin also showed differences. Both types of OPCs were able to mature into oligodendrocytes and produce myelin sheaths, but only the spiking OPCs had the ability to produce longer and thicker myelin sheaths.

Said Deng, “We actually developed ‘super cells’ with an even greater capacity to spike than natural cells. This appears to give them an edge for maturing into oligodendrocytes and producing better myelin.

Human neural tissue has a poor capacity to regenerate and even though OPCs are present, they do not regenerate tissue effectively when disease or injury damages the myelin sheath. Deng believes that replacing glial cells with the enhanced spiking OPCs to treat injuries and diseases has the potential to be a better strategy than replacing neurons, since neurons are so problematic to work with in the laboratory. Instead providing the proper structure and environment for neurons to live might be the best approach to regenerate healthy neural tissue. Deng also said that many diverse conditions that have not been traditionally considered to be myelin-based diseases (schizophrenia, epilepsy, and amyotrophic lateral sclerosis) are actually now recognized to involve defective myelin.

On that one, I think Deng is dreaming. ALS is caused by the death of motor neurons due to mechanisms that are intrinsic to the neurons themselves. Giving them all the myelin in the world in not going to help them. Also, OPCs made from ESCs will be rejected out of hand by the immune system if they are used to regenerate myelin in the peripheral nervous system. The only hope is to keep them in the central nervous system, but even there, any immune response in the brain will be fatal to the OPCs. This needs to be tested with iPSCs before it can be considered for clinical purposes.

The Use of Synthetic Messenger RNAs Augment Heart Regeneration and Healing After a Heart Attack


A collaborative effect between researchers at Harvard University and Karolinska Institutet has shown that the application of particular factors to the heart after a heart attack can heal the heart and induce the production of new heart muscle.

Kenneth Chien, who has a dual appointment at the medical university Karolinska Institutet and Harvard University, led this research teams said this about this work: “This is the beginning of using the heart as a factory to produce growth factors for specific families of cardiovascular stem cells, and suggests that it may be possible to generate new heart parts without delivering any new cells to the heart itself.”

This study builds upon previous work by Chien and his colleagues in which the growth factor VEGFA, which is known to activate the growth of endothelial cells in the adult heart (endothelial cells line blood vessels), also serves as a switch that converts heart stem cells away from making heart muscle to forming coronary vessels in the fetal heart.

To drive the expression of VEGFA in the heart, Chien and others made synthetic messenger RNAs that encoded VEGFA and injected them into the heart cells. Injections of these synthetic VEGFA messenger RNAs produced a short burst of VEGFA.

Chien induced a heart attack in mice and then administered the synthetic VEGFA messenger RNAs to some mice and buffer to others 48 hours after the heart attacks. Chien and his crew was sure to inject the synthetic VEGFA mRNAs into the regions of the heart known to harbor the resident cardiac stem cell populations.

Not only did the VEGFA-mRNA-injected mice survive better than the other mice, but their hearts had smaller heart scars, and had clear signs of the growth of new heart muscle that had been made by the resident cardiac stem cell populations. One pulse of VEGFA had long-term benefits and those cells that would have normally made the heart scar ended up making heart muscle instead as a result of one pulse of VEGFA.

Chien said of this experiment, “This moves us very close to clinical studies to regenerate cardiovascular tissue with a single chemical agent without the need for injecting any additional cells into the heart.”

At the same time, Chien also noted that this technology is in the early stages of development. Even though these mice had their chests cracked open and their hearts injected, for human patients, the challenge is to adapt heart catheter technologies to the delivery of synthetic messenger RNAs. Also, to demonstrate the safety and efficacy of this technology to humans, Chien and others will need to repeat these experiments in larger animals that serve as a better model system for the human heart than rodents. Chien’s laboratory is presently in the process of doing that.

To adapt catheter technology to deliver these reagents, Chien had co-founded a company called Moderna Therapeutics to research this problem and develop the proper platform technology for clinical use. Chien is also collaborating with the biotechnology company AstraZeneca to help expedite moving the synthetic RNA technology into a clinical setting.