Cell fusion ‘awakens’ regenerative potential of human retina

Fusing human retinal cells with adult stem cells could be a potential therapeutic strategy to treat retinal damage and visual impairment, according to the findings of a new study published in the journal eBioMedicine. The hybrid cells act by awakening the regenerative potential of human retinal tissue, previously only thought to be the preserve of cold-blood vertebrates.

Cell fusion events -- the combination of two different cells into one single entity -- are known to be a possible mechanism contributing to tissue regeneration. Though rare in humans, the phenomenon has been consistently detected in the liver, brain, and gastrointestinal tract.

A team led by ICREA Research Professor Pia Cosma at the Centre for Genomic Regulation (CRG) in Barcelona and funded by Fundació "la Caixa" has now found that cell fusion events also take place in the human retina.

The researchers tested whether cell fusion events could differentiate into cells that turn into neurons, which would show potential for tissue regeneration. The team fused Müller glia, cells that play a secondary but important role in maintaining the structure and function of the retina, with adult stem cells derived from human adipose tissue or bone marrow.

"We were able to carry out cell fusion in vitro,creating hybrid cells. Importantly, the process was more efficient in the presence of a chemical signal transmitted from the retina in response to damage, resulting in rates of hybridisation increasing twofold. This gave us an important clue for the role of cell fusion in the retina," says Sergi Bonilla, postdoctoral researcher at the CRG at the time of publication and first author of the study.

The hybrid cells were injected into a growing retinal organoid, a model that closely resembles the function of the human retina. The researchers found that the hybrid cells successfully engrafted into the tissue and differentiated into cells that closely resemble ganglion cells, a type of neuron essential for vision.

"Our findings are important because they show that the Müller Glia in the human retina have the potential to regenerate neurons," says Pia Cosma. "Salamanders and fish can repair damage caused to the retina thanks to their Müller glia, which differentiate into neurons that rescue or replace damaged neurons. Mammalian Müller glia have lost this regenerative capacity, which means retinal damage or degradation can lead to visual impairment for life. Our findings bring us one step closer to recovering this ability."

The authors caution that much work remains to be done before the development of any potential treatments. One of the next steps is understanding why hybrid cells -- with four complete sets of chromosomes -- don't result in chromosomal instability and cancer development. The authors of the study believe the retina may have a mechanism regulating chromosome segregation similar to the liver, which contains tetraploid cells that act as a genetic reservoir, undergoing mitosis in response to stress and injury.

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Deep neural network to find hidden turbulent motion on the sun

Scientists developed a neural network deep learning technique to extract hidden turbulent motion information from observations of the Sun. Tests on three different sets of simulation data showed that it is possible to infer the horizontal motion from data for the temperature and vertical motion. This technique will benefit solar astronomy and other fields such as plasma physics, fusion science, and fluid dynamics.

The Sun is important to the Sustainable Development Goal of Affordable and Clean Energy, both as the source of solar power and as a natural example of fusion energy. Our understanding of the Sun is limited by the data we can collect. It is relatively easy to observe the temperature and vertical motion of solar plasma, gas so hot that the component atoms break down into electrons and ions. But it is difficult to determine the horizontal motion.

To tackle this problem, a team of scientists led by the National Astronomical Observatory of Japan and the National Institute for Fusion Science created a neural network model, and fed it data from three different simulations of plasma turbulence. After training, the neural network was able to correctly infer the horizontal motion given only the vertical motion and the temperature.

The team also developed a novel coherence spectrum to evaluate the performance of the output at different size scales. This new analysis showed that the method succeeded at predicting the large-scale patterns in the horizontal turbulent motion, but had trouble with small features. The team is now working to improve the performance at small scales. It is hoped that this method can be applied to future high resolution solar observations, such as those expected from the SUNRISE-3 balloon telescope, as well as to laboratory plasmas, such as those created in fusion science research for new energy.

From Science Daily

JET fusion facility sets a new world energy record

European scientists have achieved a major success on the road to energy production through fusion plasmas: They produced stable plasmas with 59 megajoules of energy output at the world's largest fusion facility, JET, in Culham near Oxford, UK. The team, which also includes researchers from the Max Planck Institute for Plasma Physics (IPP), used the fuel of future fusion power plants. These were the first experiments of their kind in the world in more than 20 years.

Following the example of the sun, fusion power plants aim to fuse the hydrogen isotopes deuterium and tritium and release large amounts of energy in the process. The only plant in the world currently capable of operating with such fuel is the European joint project JET, the Joint European Torus in Culham near Oxford, UK. However, the last experiments with the fuel for future fusion power plants were conducted there in 1997. Because tritium is a very rare raw material that also poses special handling challenges, research teams usually use hydrogen or deuterium for plasma experiments. In future power plants, tritium will be formed from lithium during energy production.

Experiments with deuterium-tritium mixtures in preparation for ITER

"We can explore the physics in fusion plasmas very well by working with hydrogen or deuterium, so this is the standard worldwide," explains IPP's Dr. Athina Kappatou, who with her IPP colleagues Dr. Philip Schneider and Dr. Jörg Hobirk led significant parts of the European collaborative experiments at JET." However, for the transition to the international, large-scale, fusion experiment ITER, it is important that we prepare for the conditions prevailing there." ITER is currently under construction in Cadarache, in southern France, and is expected to be able to release ten times as much energy as is fed into the plasma in terms of heating energy, using deuterium-tritium fuel.

To bring the JET experiment as close as possible to future ITER conditions, the previous carbon lining of the plasma vessel was replaced by a mixture of beryllium and tungsten, as is also planned for ITER, between 2009 and 2011. The metal tungsten is more resistant than carbon, which, moreover, stores too much hydrogen. However, the now metallic wall places new demands on the quality of the plasma control. The current experiments demonstrate the successes of the researchers: At temperatures ten times higher than those at the center of the sun, record levels of generated fusion energy have been achieved.

World record under ITER-like conditions

Prior to the change of the wall material, JET had set the world energy record in 1997 with a plasma that produced 22 megajoules of energy. This record stood until now. "In the latest experiments, we wanted to prove that we could create significantly more energy even under ITER-like conditions," explains IPP physicist Dr. Kappatou. Several hundred scientists and researchers were involved in years of preparation for the experiments. They used theoretical methods to calculate in advance the parameters they needed to obtain to generate the plasma in order to achieve their goals. The experiments confirmed the predictions in late 2021 and delivered a new world record: JET produced stable plasmas with deuterium-tritium fuel that released 59 megajoules of energy.

To produce net energy -- that is, to release more energy than the heatering systems provide -- the experimental facility is too small. This will not be possible until the larger-scale ITER experiment in southern France comes online. "The latest experiments at JET are an important step toward ITER," concludes Prof. Sibylle Günter, Scientific Director of the Max Planck Institute for Plasma Physics. "What we have learned in the past months will make it easier for us to plan experiments with fusion plasmas that generate much more energy than is needed to heat them."

Background information: Megawatts vs. Megajoules

In the recent record-breaking experiment, the fusion reactions in JET released a total of 59 megajoules of energy in the form of neutrons during a five-second phase of a plasma discharge. Expressed in units of power (energy per time), JET achieved a power output of just over 11 megawatts averaged over five seconds. The previous energy record, set in 1997, was just under 22 megajoules of total energy and 4.4 megawatts of power averaged over five seconds.

About JET

JET was jointly designed and built by the members of the European fusion program EUROfusion and has been jointly operated since 1983. The English fusion center "Culham Centre for Fusion Energy" in Culham near Oxford is responsible for the technical operations, while temporarily seconded researchers and technicians from the EUROfusion laboratories work on the facility on a campaign basis. With numerous secondments, IPP is an important participant in the JET program.

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