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I think Fibrinogen has been mentioned before, but here is a new report about how it prevents neurons from regrowing after damage:

Public release date: 3-Jul-2007
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Contact: Debra Kain
ddkain@ucsd.edu
619-543-6163
University of California - San Diego

Blood clotting protein may inhibit spinal cord regeneration
Fibrinogen, a blood-clotting protein found in circulating blood, has been found to inhibit the growth of central nervous system neuronal cells, a process that is necessary for the regeneration of the spinal cord after traumatic injury. The findings by researchers at the University of California, San Diego (UCSD) School of Medicine, may explain why the human body is unable to repair itself after most spinal cord injuries.

The study, led by Katerina Akassoglou, Ph.D., assistant professor in UCSD’s Department of Pharmacology, is the first evidence that when blood leaks into the nervous system, the blood protein contributes to the neurons’ inability to repair themselves. The findings, which show the molecular link between vascular and neuronal damage during injury to the central nervous system, was published in the online issue of the Proceedings of the National Academy of Sciences on July 2.

The research team studied three types of spinal cord injuries in mice and rats which resulted in cellular and vascular damage, and leakage of fibrinogen from the blood vessels. Once injured, neurons cannot be repaired because of various inhibitors that are present in the brain and the spinal cord after damage, which results in a patient’s paralysis. The researchers were surprised at the massive deposits of fibrinogen found at the sites of injury. That discovery led them to investigate the protein’s effect on neuronal cells’ ability to regenerate.

“Our study shows that fibrinogen directly affects neurons by inhibiting their ability for repair,” said Akassoglou. Fibrinogen – contained in the blood which leaks at the site of injury – begins the process of inhibiting axonal growth by binding to the beta 3 integrin receptor. This binding, in turn, induces the activation of another receptor on the neuronal cells, called the epidermal growth factor receptor. When the second receptor is activated, it inhibits the axonal growth. Other inhibitors have been identified that use the same epidermal growth factor receptor, but this is the first blood-derived inhibitor that has been found.

The discovery may open the door to a possible strategy to improving recovery after spinal cord injury by discovering a way to block activation of neuronal receptors by fibrinogen. Identifying the specific inhibitors that impede the repair process could provide ways to regenerate and connect the damaged nerves and initiate recovery from paralysis after spinal cord injury.

“Inhibiting the damaging effects of fibrinogen on neurons may potentially facilitate repair in the nervous system after injury” said Akassoglou. A similar mechanism could be at work in other neurological diseases that result in paralysis, such as multiple sclerosis or hemorrhagic stroke, where blood vessels break and bleed into the brain. She added that such a therapeutic approach wouldn’t interfere with fibrinogen’s essential role in coagulation, because its blood-clotting mechanism depends on binding with a different receptor.

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Additional contributors to the paper include first author Christian Schachtrup, Jerry Lu and Ben D. Sachs of UCSD’s Department of Pharmacology, and Paul Lu, Jae K. Lee and Binhai Zheng of UCSD’s Department of Neurosciences. The research was funded in part by grants from the German Research Foundation, National Multiple Sclerosis Society, National Institute of Neurologic Diseases and Stroke (NIH/NINDS) and the Christopher Reeve and Sam Schmidt Paralysis Foundation.



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So, during my MS diagnosis 7.5 years ago I had a spinal tap and from that I had a disabling headache for about a week (if I stood up too long it felt like someone was trying to pull my brains out of my head through the back of my neck). The doctors stated that this sometimes happens with younger patients (I was in my early 30's at the time) and is due to spinal fluid continuing to leak from where the dura was punctured (hoping I got the anatomy correct). As a result, I had to go back to the hospital where they took some blood out of my arm and put it into my back so it would clot and seal up the spinal fluid leak. This worked and I was headache free after about 20-30 minutes! However, after reading this article about fibrinogen, I suspect that this might not be the best practice especially in someone with enhancing lesions on their spinal chord (which I had at that time). Could the above practice potentially be making MS worse by inhibiting any healing of MS lesions?

NHE

Hi NHE,
I've never heard of either of those two things before: either a spinal tap continuing to leak or blood being used to plug the gap, (kind of sounds like that stuff you use to repair a slow puncture in a tyre). I had my first lumbar puncture when I was eleven, and I had to lay flat for an hour while the fluid was replaced to prevent a headache.
This is a complete guess, but I should think that IF you had some nerve damage at the time of your spinal tap, and especially if it was close to the site, then it's not inconceivable that the blood could have impeded repair. I would imagine that minute quantities of blood products can enter the CSF even during a normal procedure, but that the effects are generally limited.
It's a bit worrying though, to think that a routine procedure just MIGHT be introducing things to this CNS which shouldn't be there – I wonder if anyone has ever monitored what happens in the days and weeks following a spinal tap?