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International Journal of Bioprinting 3D printing technology in neurotrauma

In terms of cellular composition, the nervous system Peripheral nerve injury (PNI) is one of the most
is characterized by functionally specialized neurons and common neuropathies, which is often caused by diseases,
unique glial cell types. Neurons act to conduct electrical accidents, and natural disasters. It has been reported
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signals, and glial cells are mainly responsible for the that there are more than 20 million patients diagnosed
stability and development of the nervous system, which with PNI every year in the United States and more
are arranged alongside neurons. In addition, glial cells than 300,000 patients diagnosed with PNI every year in
can provide metabolic support to neurons and promote Europe. 21,22 PNI often affects neural signal transduction,
the survival, differentiation, and outgrowth of neurons. leading to the loss of sensory and motor function and
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Furthermore, the extracellular matrix (ECM), synthesized even causing disability in patients. Unlike the CNS, the
and secreted by cells, is indispensable in the nervous PNS has an intrinsic ability of regeneration. 23,24 After
system. The ECM of the nervous system is made up of an injury, Wallerian degeneration occurred at the distal
three parts: the basement, a diffuse interstitial portion, and end of the injured sites, and the debris was cleared by
perineuronal net (PNN). PNN is a special component of Schwann cells and phagocytes. 25,26 Meanwhile, Schwann
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ECM in the nervous system, contributing to maintaining cells would proliferate and migrate rapidly to form the
the newly appointed neuronal connections and neuronal Bungner band, and the growth cone could advance
protection while concurrently inhibiting synaptic plasticity toward the distal end. However, in severe cases of PNI,
and neural regeneration with certain components like especially long-segmental PNI, the self-regeneration
CSPGs. Besides, there are other crucial components, of the peripheral nerves is unable to realize the re-
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such as chemotropic and neurotrophic factors, in the ECM connection of the injured nerves. 27,28 At present, the
of the nervous system. functional recovery of long-segmental PNI remains
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1.2. Neurotrauma challenging in regenerative medicine. Autografts have
Neurotrauma is an emergency situation and refers to injuries been considered the gold standard for the clinical
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that involve the CNS and PNS. CNS injuries mainly include treatment of PNI, but this strategy is still restricted
traumatic brain injury (TBI) and spinal cord injury (SCI). by inadequate nerve donors, donor site morbidity, and
TBI is defined as an alteration in brain function, or other secondary trauma. Recently, nerve guide conduits derived
evidence of brain pathology, caused by an external force. It from synthetic and/or natural materials have been
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can be divided into mild, moderate, and severe injuries. developed as promising alternatives for PNI treatment.
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With 50 million new cases of mild TBI and 2 million new With a tube-like structure, a conduit can provide physical
cases of moderate and severe TBI being reported every support and directional guidance for nerve regeneration.
year worldwide, TBI has emerged as a global public health Currently, several conduits have been approved by the
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problem. The absence of effective treatments poses a Food and Drug Administration (FDA) for PNI repair. 21,30
challenge to the management of TBI. Despite advances in However, the therapeutic efficacy of these conduits for
preoperative measures and intensive care, TBI still results long-segmental PNI is still unsatisfactory and needs to
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in high mortality and long-term neurological deficits. In be improved.
addition to the primary injury, secondary injuries such as Recently, some new treatment approaches, including
inflammatory reaction, reduction of neural cells, and glial gene therapy, electrical stimulation, electrochemical
scar formation may occur after TBI. In recent years, the neuromodulation therapy, and stem cell therapy, have
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emergence of stem cell therapy and tissue engineering has been used for neurotrauma treatment. However, these
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provided new strategies for neural network reconstruction strategies can still not provide an ideal microenvironment
after TBI. 14,15 However, the delivery and survival of stem for repairing nervous system injuries, which can resemble
cells to the injured sites still face significant challenges. the physical and biological characteristics of natural
SCI is characterized by damage to the spinal cord, which tissues, such as the anatomical structure, the diversities of
breaks nerve contact between the brain and the rest of cells and bioactive substances, and the spatial distribution
the body, leading to temporary or permanent functional of the bioactive components.
impairment. Approximately 500,000 individuals suffer
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from SCI worldwide every year, resulting in a huge 1.3. 3D printing and 3D bioprinting technology
socioeconomic burden. Currently, treatment options for 3D printing is an additive manufacturing process that
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SCI encompass surgical interventions, pharmaceutical creates unique 3D constructs by building 3D structures
approaches, hypothermia, and rehabilitative medical care. layer by layer from computer-aided design (CAD)
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Nevertheless, the effectiveness of these treatments is limited, models. 3D printing combined with 3D imaging
and the prognosis for individuals with SCI is poor. technology and robot-based precision biofabrication
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Volume 10 Issue 3 (2024) 62 doi: 10.36922/ijb.2311