Spinal cord injuries can leave a person paralysed for life. Our bodies have an incredible capacity for healing, but when it comes to regenerating a damaged spinal cord we don’t have what it takes to fix ourselves. However, there is still hope for those suffering from a debilitating break in their spinal cord. Sachdeva et al., American researchers in the field of neuroscience, have provided results suggesting that perhaps we aren’t too far off from being able to repair a complete spinal cord breakage, using a few tricks.

These researchers hypothesized that it is possible to force the cells that make up the spinal cord, known as neurons, to repair themselves. Spinal cord injuries usually affect the axons of these cells, which are long finger-like extensions from the main body of the cell that connect one neuron to the next. These axons don’t usually heal when damaged because they are hindered by other aspects of the injury and because they lack the necessary proteins to completely fix themselves. Evidence suggests, however, that it is possible to heal a damaged neuron by facilitating its growth with a graft, and by signalling the cell to produce more protein synthesizing machinery (molecules inside the cell that produce proteins) in response to the stimulus of the breakage. The protein synthesizing machinery can then be brought to the site of the break in the axon, the researchers suggested, so that the proteins can be produced locally in order to extend the length of the axon and repair the break.

The researchers decided to test and see if they can coax neurons with damaged axons into regenerating themselves. They did this by removing 8-10mm segments of axons in the spinal cords of donor rats, and using them as grafts in recipient rats who had similar length segments of their spinal axons removed. They knew that it would probably take 4 weeks for the axon to grow to the end of the graft, so the researchers observed some rats after 3 weeks (while the axon was still growing), some after 7 weeks (after the axon stopped growing), and then some at the 9 week mark .This third group, however, had their axons reinjured at 7 weeks by snipping off the tip of the repaired axon in the graft, and then they were allowed to heal for 2 weeks in order to observe any changes in protein quantities. The results of the experiment were very exciting; after 3 weeks, the rats showed the presence of many proteins associated with axon repair and regeneration in their axons. After 7 weeks,  the rats showed a marked decrease in the levels of each protein, some significantly. After 9 weeks (the rats who had their axons reinjured), they showed a marked increase in protein levels, with some also being significant.

To put it plainly, the axons contained the machinery to synthesize proteins while the axon was regenerating, and it was using them for self repair by making the necessary proteins. The axon then lost them when regeneration stopped, indicating the cell was no longer making protein synthesizing machinery for the axon to produce the proteins . The machinery was, however, present again after the axon was reinjured near the end of the graft (an extracellular stimulus). These findings suggest the neuron was gearing up to build more axon even after the initial reparation. This is extremely promising, as it shows that axons in adults can be potentially made to fix themselves with a little coaxing. Understanding how the cellular machinery works in central nervous system neurons can allow us to prod these cells in such ways that make them work for us how we want them to. In other words, we can potentially find certain ways to put cells in particular conditions that make them want to fix themselves for us, where naturally they would do no such thing. That prospect shows a bright future in the field of neuroscience with hopefully many breakthroughs in methods of neuron repair.

Source:

Sachdeva R., Farrell K., McMullen M.K., Twiss J.L., Houle J.D. Dynamic changes in local protein synthetic machinery in regenerating central nervous system axons after spinal cord injury. Neural Plasticity 2016 4087254 1-11. https://www.hindawi.com/journals/np/2016/4087254/