Injured spinal cord: Regeneration possible with epothilone?

Damage to the spinal cord rarely heals because the injured nerve cells fail to regenerate. The regrowth of their long nerve fibers is hindered by scar tissue and molecular processes inside the nerves. An international team of researchers led by DZNE scientists in Bonn now reports in Science that help might be on the way from an unexpected quarter: in animal studies, the cancer drug epothilone reduced the formation of scar tissue in injuries to the spinal cord and stimulated growth in damaged nerve cells. Both promoted neuronal regeneration and improved the animals' motor skills. 

Cross section rat spinal cord. Immunostaining: axons (red), synapses (green), motor neurons (blue).

Nerve cells are wire-like conductors that transmit and receive signals in the form of electrical impulses. This function can be impaired by accidents or disease. Whether or not the affected nerves can recover largely depends on their location: for instance nerve cells in the limbs, torso and nose can regenerate to some degree and regain some or all of their function.
In contrast, the neurons in the brain and spinal cord do not have this ability. If they are damaged by accident or disease, the patient is likely to suffer long-term paralysis or other disabilities. But why is regeneration of these neurons and their long nerve fibers impeded? It is already known that inhibiting factors in newly formed scar tissue and other cellular processes block axon regrowth.
Seeking the ideal treatment
"The ideal treatment for promoting axon regeneration after spinal cord injury would inhibit the formation of scar tissue," says Professor Frank Bradke, who leads a working group at the DZNE's site in Bonn and who conducted the study. "However, it is also important that the growth-inhibiting factors are neutralized while reactivating the poor axons' regenerative potential." A feasible administration of a potential treatment is also essential for clinical application.
In cooperation with international researchers, Bradke and his team have now managed to take another step towards the development of a future treatment. From their previous research, it was already known that stabilizing microtubules would reduce the formation of scar tissue and promote axonal growth. Microtubules are long, tubular filaments inside the cell that can grow and shrink dynamically. They are part of the cell's supportive skeleton, which also controls cell growth and movement.
The substance epothilone can stabilize microtubules and is already licensed on the American market -- as a cancer treatment. "It all depends on the dose," says Dr. Jörg Ruschel, the study's lead author. "In higher doses, epothilone inhibits the growth of cancer cells, while low doses have been shown to stimulate axonal growth in animals without the severe side-effects of cancer treatment." Epothilone is superior to other cancer drugs with a similar effect because it can penetrate the blood-brain barrier into the central nervous system, thus reaching the damaged axons directly.
One substance -- many effects
Experiments have shown epothilone works on several levels. Epothilone reduces the growth of scar tissue by inhibiting the formation of microtubules in the cells that form the scar tissue. Therefore they cannot migrate to the spinal cord lesion and cause wound scarring. At the same time, epothilone promotes growth and regeneration in the nerve cells by causing microtubules to grow into the damaged axon tips.
In short: through the same effect, namely microtubule stabilization, epothilone is able to inhibit directional movement in scar-forming cells while stimulating active growth in nerve cell axons. The animals treated with epothilone after spinal cord injury walked better than those that received no treatment, due to improved balance and coordination. The next goal of Bradke and his team is to test the effect of epothilone on various types of lesion.

Journal Reference:

1. Jörg Ruschel, Farida Hellal, Kevin C. Flynn, Sebastian Dupraz, David A. Elliott, Andrea Tedeschi, Margaret Bates, Christopher Sliwinski, Gary Brook, Kristina Dobrint, Michael Peitz, Oliver Brüstle, Michael D. Norenberg, Armin Blesch, Norbert Weidner, Mary Bartlett Bunge, John L. Bixby and Frank Bradke. Systemic administration of epothilone B promotes axon regeneration after spinal cord injury. Science, 2015 DOI: 10.1126/science.aaa2958 

Courtesy: ScienceDaily

Molecule-making machine simplifies complex chemistry

A new molecule-making machine could do for chemistry what 3-D printing did for engineering: Make it fast, flexible and accessible to anyone.

 

A machine in University of Illinois chemistry professor Martin Burke's lab assembles complex small molecules out of simple chemical building blocks, like a 3-D printer on the molecular level.

Chemists at the University of Illinois, led by chemistry professor and medical doctor Martin D. Burke, built the machine to assemble complex small molecules at the click of a mouse, like a 3-D printer at the molecular level. The automated process has the potential to greatly speed up and enable new drug development and other technologies that rely on small molecules.

"We wanted to take a very complex process, chemical synthesis, and make it simple," said Burke, a Howard Hughes Medical Institute Early Career Scientist. "Simplicity enables automation, which, in turn, can broadly enable discovery and bring the substantial power of making molecules to nonspecialists."

The researchers described the technology in a paper featured on the cover of the March 13 issue of Science.

"Small molecules" are a specific class of complex, compact chemical structures found throughout nature. They are very important in medicine -- most medications available now are small molecules -- as well as in biology as probes to uncover the inner workings of cells and tissues. Small molecules also are key elements in technologies like solar cells and LEDs.

However, small molecules are notoriously difficult to make in a lab. Traditionally, a highly trained chemist spends years trying to figure out how to make each one before its function can even be explored, a slowdown that hinders development of small-molecule-based medications and technologies.

"Up to now, the bottleneck has been synthesis," Burke said. "There are many areas where progress is being slowed, and many molecules that pharmaceutical companies aren't even working on, because the barrier to synthesis is so high."

The main question that Burke's group seeks to answer: How do you take something very complex and make it as simple as possible?

The group's strategy has been to break down the complex molecules into smaller building blocks that can be easily assembled. The chemical building blocks all have the same connector piece and can be stitched together with one simple reaction, the way that a child's interconnecting plastic blocks can have different shapes but all snap together. Many of the building blocks Burke's lab has developed are available commercially.

To automate the building-block assembly, Burke's group devised a simple catch-and-release method that adds one building block at a time, rinsing the excess away before adding the next one. They demonstrated that their machine could build 14 different classes of small molecules, including ones with difficult-to-manufacture ring structures, all using the same automated building-block assembly.

"Dr. Burke's research has yielded a significant advance that helps make complex small molecule synthesis more efficient, flexible and accessible," said Miles Fabian of the National Institutes of Health's National Institute of General Medical Sciences, which partially funded the research. "It is exciting to think about the impact that continued advances in these directions will have on synthetic chemistry and life science research."

The automated synthesis technology has been licensed to REVOLUTION Medicines, Inc., a company that Burke co-founded that focuses on creating new medicines based on small molecules found in nature. The company initially is focusing on anti-fungal medications, an area where Burke's research has already made strides.

"It is expected that the technology will similarly create new opportunities in other therapeutic areas as well, as the industrialization of the technology will help refine and broaden its scope and scalability," Burke said.

"Perhaps most exciting, this work has opened up an actionable roadmap to a general and automated way to make most small molecules. If that goal can be realized, it will help shift the bottleneck from synthesis to function and bring the power of making small molecules to nonspecialists."

Journal Reference:

1. Junqi Li, Steven G. Ballmer, Eric P. Gillis, Seiko Fujii, Michael J. Schmidt, Andrea M. E. Palazzolo, Jonathan W. Lehmann, Greg F. Morehouse, and Martin D. Burke. Synthesis of many different types of organic small molecules using one automated process. Science, 13 March 2015 DOI: 10.1126/science.aaa5414 

Courtesy: ScienceDaily