Earlier this year researchers at the Helmholtz Zentrum Munchen (HZM), a German Research Center for Environmental Health, succeeded in stimulating the regeneration of injured neurons in a living organism using light. They used the basic principles of optogenetics to stimulate cellular activity (in this case neurons) through photo-activation. The method could be used for future therapeutic approaches in the treatment of neuropathies in humans, and be replicated in other vertebrates. Neuropathy is an abnormality of one or more peripheral nerves, which can cause numbness or weakness. It is a symptom of many underlying medical conditions.

Injury or disease can severely impact the ability of neurons to be repaired, often leading to long-term neural dysfunction. The team of researchers led by Dr. Hernan Lopez-Schier, head of the Sensory Biology and Organogenesis Research team at HZM, succeeded in the repair of injured neurons in zebrafish. The researchers’'success was due in part to the production of a messenger molecule known as cAMP. This molecule triggers the regrowth of axons, which are the connecting extensions of nerves. Using light and a specialized light induced production of adenylyl cyclase researchers controlled the production of cAMP to promote axon regeneration thereby creating new connections in otherwise dysfunctional nerves. The scientists were able to specifically modulate the production of cAMP in cells expressing this enzyme by using blue light.

They applied the system to zebrafish larvae that had interrupted sensory lateralis nerves. These nerves normally communicate external sensory signals to the brain, but cannot self-repair after injury. Once the blue light was applied to the severed nerves expressing the enzyme, their repair was dramatically increased. According to doctoral student Yan Xiao, "While untreated nerve terminals only made synapses again in 5 percent of the cases, about 30 percent did after photo-stimulation." By means of elevating cAMP levels in the nerves, the scientists were able to stimulate neuron repair.

Dr. Lopez-Schier believes that this research is only the beginning: "Our results are a first step. Now we would like to investigate whether these results can be extrapolated beyond single neurons in zebrafish, to more complex neuronal circuits of higher animals."

In conclusion, an optogenetics method has yet again provided researchers with the unparalleled ability to target specific neuron cells to perform an action - in this case, to increase the production of cAMP. It is nearly impossible to repair predefined neurons in a highly selective time period by the use of drugs or other genetics approaches, since their activity cannot be easily targeted to specific cells. We look forward to sharing more research initiatives and applications using this light-controlled optogenetics method in the months to come.

Sources:

1. 'Bright prospects: Repairing neurons with light' - Science Daily, Nov 2015:Online Link-Science Daily

2. 'Repairing Neurons with light'- Helmholtz Zentrum München Press Release: Online Link-HZM Press

3. 'Optogenetic Method Investigated for Neuron Repair'- Photonics.com Jan 2016: Online Link-Photonics.com

Researchers the University of Wisconsin have demonstrated how cerebral hemodynamics are significantly impacted after optogenetic stimulation, as was displayed by use of Spectral Domain Optical Coherence Tomography (SD-OCT) that showed both blood flow and vessel diameter can dramatically increase following stimulation. Laserglow's LabSpec LRS-473 laser was used as the stimulation light source.

Blood flow from the brain's cortex and neuron activation are two fundamentally coupled processes that regulate functions of the nervous system, and hence the body. However, the mechanisms involved in neurovascular coupling, or how blood flow to a tissue or organ changes based on signals from the nervous system, are not easily understood or identified. In this experiment, researchers used SD-OCT combined with optogenetic stimulation in an integrated platform, to optically stimulate certain cells within a field of view while simultaneously monitoring changes in blood velocity and vessel diameter. SD-OCT is used to image semi-transparent biological tissue of a few millmeters thickness, and the wavelengths used for SD-OCT are very different from those used for stimulation, so the 2 processes can be done simultaneously. In response to optical stimulation of neurons in the cortex of transgenic mice expressing channelrhodopsin-2 the researchers were able to record an average of 20% increase in diameter and 100% increase in blood flow inside the middle cerebral artery (MCA) as well as neighboring blood vessels.

The researchers are confident that further studies combining optogenetics with SD-OCT will enable cell-specific analysis of neurovascular coupling. They also propose combining this procedure with blood-oxygenation imaging, to study the brain's Blood Oxygenation Level Dependent (BOLD) signal to and from organs. This could potentially afford solutions for understanding and treating several cardiovascular diseases. To learn more about the experimental setup and read the full paper, go to: Pubmed Full Paper

In 2018 NASA will launch a system equipped with LIDAR technology for the specific purpose of mapping the world's forests in 3D, from trunk to canopy. The Global Ecosystem Dynamics Investigation (GEDI) LIDAR mission aims to assess the amount of wood-stored carbon in forests around the globe. This will provide valuable data on the impact of deforestation caused by manmade activity as well as global warming, providing clues on what actions countries may need to take in order to control this.

As trees grow they absorb carbon dioxide from the atmosphere and store this carbon in their trunks, branches and roots. Because they store more carbon than they release forests are the world's most important carbon 'sinks'. Globally, forests are estimated to suck up between 10 and 14 percent of current gross carbon emissions. By storing this material forests slow the rate at which carbon dioxide accumulates or lingers in the atmosphere. One way to reduce or reverse the buildup of CO₂ in the Earth's atmosphere is to increase the amount of carbon stored in forests. The simplest method of doing this may be to reduce deforestation rates. All forests are different and so are their varied abilities to store carbon. This NASA GEDI mission provides scientists with specific measurements relating to forest-stored carbon to help countries reach their climate change goals.

GEDI will spend at least two years on the International Space Station. Three lasers developed by NASA's Goddard Space Flight Center will spread across 14 paths and be able to collect data on the land between 50 degrees north latitude and 50 degrees south latitude, including nearly all of the tropical and temperate forests on Earth. To read more, go to: SciAm full article