This is how amazing your brain is…
This is how amazing your brain is…
The other day, I saw a quote shared on Facebook that read,“The human brain is awesome. It functions 24 hours a day from the day we are born and only stops when we are taking an exam or fall in love”. (“Or when you die” as was quickly pointed out.) It’s true that brains are pretty awesome, but what’s the brain doing after a head injury or a stroke, or during illnesses such as Parkinson’s disease? If a person is in a coma, is their brain working? And if your brain isn’t working properly, can we fix it?
Neuroscientists have been trying to find answers to these questions for decades. They quickly discovered that when it comes to healing, the brain is different from other organs. Once our nerve cells (neurons) have formed, they don’t usually replace themselves. That’s the opposite of your skin, where cells are constantly dying off and being replaced with new ones, meaning any damaged skin also disappears and is quickly replenished. Other organs are also quite good at regenerating, such as the liver – so long as it’s not abused too often. So if nerve cells don’t regenerate, that implies the brain cells we’re born with are all we’ve got, for life.
But here’s another difference between your brain and the rest of your body. It doesn’t just function, it learns. Not just learning information, but also learning to control movements and to interpret everything we perceive through our various senses. Importantly, it can continue learning into old age, if you keep using it and trying new things. Part of this learning and relearning process involves wiring and rewiring of neurons within the brain. Similarly, scientists realised that parts of the brain can sometimes rewire themselves after injury or disease, effectively bypassing the diseased area – and giving us hope that neurons do have capacity for new growth after all.
So scientists asked, what if a nerve cell is injured, but not dead, can it repair? Apparently, yes – in the right conditions, and with a bit of help. In general neurons don’t regrow (regenerate) very well, for several reasons. One important reason is that the adult brain and spinal cord seems to be a very hostile environment for growth, yet neurons in the peripheral nervous system can grow relatively well. For example, if a child injures a nerve in its arm, that nerve should be able to repair itself and has a good chance of functional recovery. By contrast, if nerve fibres in the adult spinal cord are severed, the patient is likely to remain permanently paralysed from that point down to their toes – until scientists find a cure.
Several decades ago, researchers started using grafts from nerves in other, less hostile areas of the body, to provide growth-friendly bridges for injured neurons to grow across and rejoin on the other side. While this helped achieve some growth and sometimes recovery of function in the paralysed limbs, the early lab research never progressed into clinical trials.
Recently, Prof Geoff Raisman at University College London created a very successful bridge by grafting cells from a patient’s own olfactory bulb into the damaged spine. The olfactory bulb is part of the nervous system involved in the sense of smell, and some years ago Prof Raisman discovered that it contains special types of cells that neurons really love to grow on: olfactory ensheathing cells (OECs) and olfactory nerve fibroblasts (ONFs). Furthermore, these cells are continually produced by the olfactory bulb, meaning there is a readily available supply of cells to make the graft, with relatively low risk of rejection by the immune system.
Prof Raisman successfully transplanted OECs and ONFs into the patient’s injured spine, and that patient can now walk with the aid of a frame and has even recovered some sensation in his legs, four years after being paralyzed by a stab wound. This significant scientific development builds on many previous studies, and it is hoped that further trials with more patients will be conducted in the near future.
Darek Fidyka learns to walk again following OEC transplantation. (Image BBC News.)
Treatments using replacement cell therapies are a logical choice when brain cells can’t replace or regenerate themselves. In recent years, there have been lots of news reports of scientific breakthroughs using stem cell-based therapies to treat all kinds of brain injuries and diseases. Introducing stem cells has the advantage that true stem cells have the potential to develop into any kind of cell, but also a number of disadvantages. These usually relate to where the stem cells are going to come from, potential immune reactions, and what will happen to those cells in the patient’s body in the long term.
A few weeks ago, researchers at Lund University in Sweden successfully transplanted stem cells that the had converted to treat Parkinson’s disease. This common disorder involves patients losing a particular set of nerve cells in an area of the brain that’s important for controlling movement. The researchers were able to artificially convert stem cells into replacement dopamine-transmitting neurons for the brain area that’s damaged by Parkinsons. When they transplanted them into the brains of rats with Parkinsons-like disease, the rats’ brains appeared to show signs of recovery.
Elsewhere, however, stem cell therapies are being used not to replace malfunctional cells but to kill tumour cells. Scientists at Harvard Medical School have engineered stem cells so that they will produce toxins specifically to kill brain tumours, without having harmful effects on normal cells (or themselves). When these genetically engineered stem cells were transplanted into mice brains at the site of brain tumours, cancerous cells were successfully killed, with no adverse effects on normal cells.
So not only do our brains keep working round the clock when things are running smoothly, but they can also find ways to bypass damage and resume function when communication breaks down. As for exams, we know that repetition and practice are the key to optimal performance, but it could be many more centuries before we unlock the mysteries of love.
Are you looking after your brain cells? Let me know @kateatnotch