Written by Sara Bozyel
Our brain is like a conductor of an orchestra. It controls and directs every command for our muscles to act out. It is the center of our body and the interactions within itself and the physical body. Our brain provides the control and interaction that our body establishes over it with brain cells (1). When it gets physically damaged, like getting hit with a rock, damage caused by a stroke can kill neurons outright or slowly starve them of the oxygen and nutrients they need to survive. Spinal cord injury can disrupt communication between the brain and muscles when neurons lose their connection to axons (2). Well, can a brain cell regenerate after damage?
(Image Credit: https://today.ucsd.edu/story/why_are_neuron_axons_long_and_spindly.)
In the brain, the damaged cells are nerve cells, known as neurons, and they cannot regenerate (4). The damaged area gets necrosed (tissue death) and it is never the same as it was before. When the brain gets injured, you are often left with disabilities that persist for the rest of your life (4). Since the brain cannot repair itself, to prevent a lifetime injury, it requires outside help. Our brain can make thousands of new neurons per day, but when it comes to repairing, it gets tricky. Repairing the human brain remains a challenge. After brain injury, the hostile microenvironment and the lack of structural support for neural cell repopulation, anchoring, and synapse formation reduce successful repair chances (3). However, a variety of natural and synthetic materials are available and have been used to replace damaged tissue, and bioscaffolds (3). Bioscaffolds can assume different shapes and may or may not carry a diversity of content, such as stem cells, growth factors, exosomes, and si/miRNA that promote specific therapeutic effects and stimulate brain repair (3). The use of these external bioscaffolds and the creation of cell platforms provide the basis for tissue engineering. More recently, researchers were able to engineer brain organoids, neural networks, and even 3D-printed neural tissue (3). The challenge in neural tissue engineering remains in the fabrication of scaffolds with precisely controlled topography and biochemical cues capable of directing and controlling neuronal cell fate (3).
(Image Credit: https://www.researchgate.net/figure/The-steps-of-the-tissue-engineering-process-In-the-red-circle-the-part-of-the-tissue_fig2_349646663.)
As with most tissues in the body, the brain has mechanisms to regenerate itself, such as endogenous neurogenesis and neuroplasticity (3). However, these processes are limited after injury (3). One of the main reasons explaining the limitation is the hostile microenvironment formed by brain injuries or diseases. The lack of a healthy ECM and the presence of the glial scar impairs neuronal survival, axonal sprouting, and synaptogenesis (3).
Tissue engineering is a newly emerging field that combines biomaterials, stem cells, and chemical and physical cues to produce engineered tissue-like structures with the ultimate goal of replacing in vivo tissues and organs (3). Biomaterials refer to a class of materials that have been engineered to integrate with a biological system and provide beneficial effects by directing or controlling cell interaction (3). In brain injuries, biomaterials are mainly used for two purposes: as bioscaffolds, to provide mechanical support to the injured brain while providing cues for new neural circuits formation, or as carriers, to deliver content such as stem cells, growth factors, exosomes, and gene vectors to the site of injury (3). By replacing the virtual cavity formed after a brain injury, bioscaffolds can provide a tissue−appropriate physical and trophic environment for new neural cells and circuitry to survive and integrate into the host tissue (3).
The human brain is complex and mysterious, it is incredibly resilient and possesses the ability to repair itself through the process of neuroplasticity. It can adapt itself to the ability of the brain to form and reorganize synaptic connections, especially in response to learning or experience or following injury. There still is a lot to see under the deep mystery of the human brain.
References:
Alban, P., & DC. (2021, November 17). Do brain cells regenerate? Yes, and you can help. Be Brain Fit. https://bebrainfit.com/brain-cells-regenerate.
Brain basics: The life and death of a Neuron. (n.d.). National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-life-and-death-neuron.
Neurorepair and regeneration of the brain: A decade of Bioscaffolds and engineered Microtissue. (n.d.). Frontiers. https://www.frontiersin.org/articles/10.3389/fcell.2021.649891/full.
Shaikh, J. (n.d.). Can you heal a damaged brain? MedicineNet. https://www.medicinenet.com/can_you_heal_a_damaged_brain/article.htm.