Tissue engineering for the repair of peripheral nerve injury

Peripheral nerve injury is a common clinical problem and affects the quality of life of patients. Traditional restoration methods are not satisfactory. Researchers increasingly focus on the field of tissue engineering. The three key points in establishing a tissue engineering material are the biological scaffold material, the seed cells and various growth factors. Understanding the type of nerve injury, the construction of scaffold and the process of repair are necessary to solve peripheral nerve injury and promote its regeneration. This review describes the categories of peripheral nerve injury, fundamental research of peripheral nervous tissue engineering and clinical research on peripheral nerve scaffold material, and paves a way for related research and the use of conduits in clinical practice.

Local administration of icariin contributes to peripheral nerve regeneration and functional recovery

Our previous study showed that systemic administration of the traditional Chinese medicine Epimedium extract promotes peripheral nerve regeneration. Here, we sought to explore the ther- apeutic effects of local administration of icariin, a major component of Epimedium extract, on peripheral nerve regeneration. A poly（lactic-co-glycolic acid） biological conduit sleeve was used to bridge a 5 mm right sciatic nerve defect in rats, and physiological saline, nerve growth factor, icariin suspension, or nerve growth factor-releasing microsphere suspension was injected into the defect. Twelve weeks later, sciatic nerve conduction velocity and the number of myelinated fibers were notably greater in the rats treated with icariin suspension or nerve growth factor-releasing microspheres than those that had received nerve growth factor or physiological saline. The effects of icariin suspension were similar to those of nerve growth factor-releasing microspheres. These data suggest that icariin acts as a nerve growth factor-releasing agent, and indicate that local ap- plication of icariin after spinal injury can promote peripheral nerve regeneration.

Biological conduit small gap sleeve bridging method for peripheral nerve injury: regeneration law of nerve fibers in the conduit

The clinical effects of 2-mm small gap sleeve bridging of the biological conduit to repair periph- eral nerve injury are better than in the traditional epineurium suture, so it is possible to replace the epineurium suture in the treatment of peripheral nerve injury. This study sought to identify the regeneration law of nerve fibers in the biological conduit. A nerve regeneration chamber was constructed in models of sciatic nerve injury using 2-mm small gap sleeve bridging of a biodegradable biological conduit. The results showed that the biological conduit had good his- tocompatibility. Tissue and cell apoptosis in the conduit apparently lessened, and regenerating nerve fibers were common. The degeneration regeneration law of Schwann cells and axons in the conduit was quite different from that in traditional epineurium suture. During the prime period for nerve fiber regeneration （2-8 weeks）, the number of Schwann cells and nerve fibers was higher in both proximal and distal ends, and the effects of the small gap sleeve bridging method were better than those of the traditional epineurium suture. The above results provide an objec- tive and reliable theoretical basis for the clinical application of the biological conduit small gap sleeve bridging method to repair peripheral nerve injury.

Autologous transplantation with fewer fibers repairs large peripheral nerve defects

Peripheral nerve injury is a serious disease and its repair is challenging. A cable-style autologous graft is the gold standard for repairing long peripheral nerve defects; however, ensuring that the minimum number of transplanted nerve attains maximum therapeutic effect remains poorly understood. In this study, a rat model of common peroneal nerve defect was established by resecting a 10-mm long right common peroneal nerve. Rats receiving transplantation of the common peroneal nerve in situ were designated as the in situ graft group. Ipsilateral sural nerves（10–30 mm long） were resected to establish the one sural nerve graft group, two sural nerves cable-style nerve graft group and three sural nerves cable-style nerve graft group. Each bundle of the peroneal nerve was 10 mm long. To reduce the barrier effect due to invasion by surrounding tissue and connective-tissue overgrowth between neural stumps, small gap sleeve suture was used in both proximal and distal terminals to allow repair of the injured common peroneal nerve. At three months postoperatively, recovery of nerve function and morphology was observed using osmium tetroxide staining and functional detection. The results showed that the number of regenerated nerve fibers, common peroneal nerve function index, motor nerve conduction velocity, recovery of myodynamia, and wet weight ratios of tibialis anterior muscle were not significantly different among the one sural nerve graft group, two sural nerves cable-style nerve graft group, and three sural nerves cable-style nerve graft group. These data suggest that the repair effect achieved using one sural nerve graft with a lower number of nerve fibers is the same as that achieved using the two sural nerves cable-style nerve graft and three sural nerves cable-style nerve graft. This indicates that according to the ‘multiple amplification＇ phenomenon, one small nerve graft can provide a good therapeutic effect for a large peripheral nerve defect.

Biodegradable chitin conduit tubulation combined with bone marrow mesenchymal stem cell transplantation for treatment of spinal cord injury by reducing glial scar and cavity formation

We examined the restorative effect of modified biodegradable chitin conduits in combination with bone marrow mesenchymal stem cell transplantation after right spinal cord hemisection injury. Immunohistochemical staining revealed that biological conduit sleeve bridging reduced glial scar formation and spinal muscular atrophy after spinal cord hemisection. Bone marrow mesenchymal stem cells survived and proliferated after transplantation in vivo, and differentiated into cells double-positive for S100 （Schwann cell marker） and glial fibrillary acidic protein （glial cell marker） at 8 weeks. Retrograde tracing showed that more nerve fibers had grown through the injured spinal cord at 14 weeks after combination therapy than either treatment alone. Our findings indicate that a biological conduit combined with bone marrow mesenchymal stem cell transplantation effectively prevented scar formation and provided a favorable local microenvi- ronment for the proliferation, migration and differentiation of bone marrow mesenchymal stem cells in the spinal cord, thus promoting restoration following spinal cord hemisection injury.

Electrical stimulation does not enhance nerve regeneration if delayed after sciatic nerve injury: the role of fibrosis

Electrical stimulation has been shown to accelerate and enhance nerve regeneration in sensory and motor neurons after injury, but there is little evidence that focuses on the varying degrees of fibrosis in the delayed repair of peripheral nerve tissue. In this study, a rat model of sciatic nerve transec- tion injury was repaired with a biodegradable conduit at 1 day, 1 week, 1 month and 2 months after injury, when the rats were divided into two subgroups. In the experimental group, rats were treated with electrical stimuli of frequency of 20 Hz, pulse width 100 ms and direct current voltage of 3 V; while rats in the control group received no electrical stimulation after the conduit operation. His- tological results showed that stained collagen fibers comprised less than 20% of the total operated area in the two groups after delayed repair at both 1 day and 1 week but after longer delays, the collagen fiber area increased with the time after injury. Immunohistochemical staining revealed that the expression level of transforming growth factor ~ （an indicator of tissue fibrosis） decreased at both 1 day and 1 week after delayed repair but increased at both 1 and 2 months after delayed repair. These findings indicate that if the biodegradable conduit repair combined with electrical stimulation is delayed, it results in a poor outcome following sciatic nerve injury. One month after injury, tissue degeneration and distal fibrosis are apparent and are probably the main reason why electrical stimulation fails to promote nerve regeneration after delayed repair.

Intraoperative single administration of neutrophil peptide 1 accelerates the early functional recovery of peripheral nerves after crush injury

Neutrophil peptide 1 belongs to a family of peptides involved in innate immunity. Continuous intramuscular injection of neutrophil peptide 1 can promote the regeneration of peripheral nerves, but clinical application in this manner is not convenient. To this end, the effects of a single intraoperative administration of neutrophil peptide 1 on peripheral nerve regeneration were experimentally observed. A rat model of sciatic nerve crush injury was established using the clamp method. After model establishment, a normal saline group and a neutrophil peptide 1 group were injected with a single dose of normal saline or 10 μg/mL neutrophil peptide 1, respectively. A sham group, without sciatic nerve crush was also prepared as a control. Sciatic nerve function tests, neuroelectrophysiological tests, and hematoxylin-eosin staining showed that the nerve conduction velocity, sciatic functional index, and tibialis anterior muscle fiber cross-sectional area were better in the neutrophil peptide 1 group than in the normal saline group at 4 weeks after surgery. At 4 and 8 weeks after surgery, there were no differences in the wet weight of the tibialis anterior muscle between the neutrophil peptide 1 and saline groups. Histological staining of the sciatic nerve showed no significant differences in the number of myelinated nerve fibers or the axon cross-sectional area between the neutrophil peptide 1 and normal saline groups. The above data confirmed that a single dose of neutrophil peptide 1 during surgery can promote the recovery of neurological function 4 weeks after sciatic nerve injury. All the experiments were approved by the Medical Ethics Committee of Peking University People's Hospital, China(approval No. 2015-50) on December 9, 2015.

Changes in proteins related to early nerve repair in a rat model of sciatic nerve injury

Peripheral nerves have a limited capacity for self-repair and those that are severely damaged or have significant defects are challenging to repair. Investigating the pathophysiology of peripheral nerve repair is important for the clinical treatment of peripheral nerve repair and regeneration. In this study, rat models of right sciatic nerve injury were established by a clamping method. Protein chip assay was performed to quantify the levels of neurotrophic, inflammation-related, chemotaxis-related and cell generation-related factors in the sciatic nerve within 7 days after injury. The results revealed that the expression levels of neurotrophic factors(ciliary neurotrophic factor) and inflammationrelated factors(intercellular cell adhesion molecule-1, interferon γ, interleukin-1α, interleukin-2, interleukin-4, interleukin-6, monocyte chemoattractant protein-1, prolactin R, receptor of advanced glycation end products and tumor necrosis factor-α), chemotaxis-related factors(cytokine-induced neutrophil chemoattractant-1, L-selectin and platelet-derived growth factor-AA) and cell generation-related factors(granulocyte-macrophage colony-stimulating factor) followed different trajectories. These findings will help clarify the pathophysiology of sciatic nerve injury repair and develop clinical treatments of peripheral nerve injury. This study was approved by the Ethics Committee of Peking University People's Hospital of China(approval No. 2015-50) on December 9, 2015.

Sleeve bridging of the rhesus monkey ulnar nerve with muscular branches of the pronator teres: multiple amplification of axonal regeneration

Multiple-bud regeneration, i.e., multiple amplification, has been shown to exist in peripheral nerve regeneration. Multiple buds grow towards the distal nerve stump during proximal nerve fiber regeneration. Our previous studies have verified the limit and validity of multiple ampli- fication of peripheral nerve regeneration using small gap sleeve bridging of small donor nerves to repair large receptor nerves in rodents. The present study sought to observe multiple ampli- fication of myelinated nerve fiber regeneration in the primate peripheral nerve. Rhesus monkey models of distal ulnar nerve defects were established and repaired using muscular branches of the right forearm pronator teres. Proximal muscular branches of the pronator teres were su- tured into the distal ulnar nerve using the small gap sleeve bridging method. At 6 months after suture, two-finger flexion and mild wrist flexion were restored in the ulnar-sided injured limbs of rhesus monkey. Neurophysiological examination showed that motor nerve conduction veloc- ity reached 22.63 _＋ 6.34 m/s on the affected side of rhesus monkey. Osmium tetroxide staining demonstrated that the number of myelinated nerve fibers was 1,657 ＋ 652 in the branches of pronator teres of donor, and 2,661 ~ 843 in the repaired ulnar nerve. The rate of multiple amplification of regenerating myelinated nerve fibers was 1.61. These data showed that when muscular branches of the pronator teres were used to repair ulnar nerve in primates, effective regeneration was observed in regenerating nerve fibers, and functions of the injured ulnar nerve were restored to a certain extent. Moreover, multiple amplification was subsequently detected in ulnar nerve axons.

Neural regeneration after peripheral nerve injury repair is a system remodelling process of interaction between nerves and terminal effector

In China, there are approximately 20 million people suffering from peripheral nerve injury and this number is increasing at a rate of 2 million per year. These patients cannot live or work independently and are a heavy responsibility on both family and society because of extreme disability and dysfunction caused by peripheral nerve injury （PNI）. Thus, repair of PNI has become a major public health issue in China.

Reinnervation of spinal cord anterior horn cells after median nerve repair using transposition with other nerves

Our previous studies have confirmed that during nerve transposition repair to injured peripheral nerves, the regenerated nerve fibers of motor neurons in the anterior horn of the spinal cord can effectively repair distal nerve and target muscle tissue and restore muscle motor function. To observe the effect of nerve regeneration and motor function recovery after several types of nerve transposition for median nerve defect(2 mm), 30 Sprague-Dawley rats were randomly divided into sham operation group, epineurial neurorrhaphy group, musculocutaneous nerve transposition group, medial pectoral nerve transposition group, and radial nerve muscular branch transposition group. Three months after nerve repair, the wrist flexion test was used to evaluate the recovery of wrist flexion after regeneration of median nerve in the affected limbs of rats. The number of myelinated nerve fibers, the thickness of myelin sheath, the diameter of axons and the cross-sectional area of axons in the proximal and distal segments of the repaired nerves were measured by osmic acid staining. The ratio of newly produced distal myelinated nerve fibers to the number of proximal myelinated nerve fibers was calculated. Wet weights of the flexor digitorum superficialis muscles were measured. Muscle fiber morphology was detected using hematoxylin-eosin staining. The cross-sectional area of muscle fibers was calculated to assess the recovery of muscles. Results showed that wrist flexion function was restored, and the nerve grew into the distal effector in all three nerve transposition groups and the epineurial neurorrhaphy group. There were differences in the number of myelinated nerve fibers in each group. The magnification of proximal to distal nerves was 1.80, 3.00, 2.50, and 3.12 in epineurial neurorrhaphy group, musculocutaneous nerve transposition group, medial pectoral nerve transposition group, and radial nerve muscular branch transposition group, respectively. Nevertheless, axon diameters of new nerve fibers, cross-sectional areas of axons, thicknesses of myelin sheath, wet weights of flexor digitorum superficialis muscle and cross-sectional areas of muscle fibers of all three groups of donor nerves from different anterior horn motor neurons after nerve transposition were similar to those in the epineurial neurorrhaphy group. Our findings indicate that donor nerve translocation from different anterior horn motor neurons can effectively repair the target organs innervated by the median nerve. The corresponding spinal anterior horn motor neurons obtain functional reinnervation and achieve some degree of motor function in the affected limbs.

Repair of peripheral nerve defects by nerve transposition using small gap bio-sleeve suture with different inner diameters at both ends

During peripheral nerve transposition repair, if the diameter difference between transposed nerves is large or multiple distal nerves must be repaired at the same time, traditional epineurial neurorrhaphy has the problem of high tension at the suture site, which may even lead to the failure of nerve suture. We investigated whether a small gap bio-sleeve suture with different inner diameters at both ends can be used to repair a 2-mm tibial nerve defect by proximal transposition of the common peroneal nerve in rats and compared the results with the repair seen after epineurial neurorrhaphy. Three months after surgery, neurological function, nerve regeneration, and recovery of nerve innervation muscle were assessed using the tibial nerve function index, neuroelectrophysiological testing, muscle biomechanics and wet weight measurement, osmic acid staining, and hematoxylin-eosin staining. There was no obvious inflammatory reaction and neuroma formation in the tibial nerve after repair by the small gap bio-sleeve suture with different inner diameters at both ends. The conduction velocity, muscle strength, wet muscle weight, cross-sectional area of muscle fibers, and the number of new myelinated nerve fibers in the biosleeve suture group were similar to those in the epineurial neurorrhaphy group. Our findings indicate that small gap bio-sleeve suture with different inner diameters at both ends can achieve surgical suture between nerves of different diameters and promote regeneration and functional recovery of injured peripheral nerves.

Short-term observations of the regenerative potential of injured proximal sensory nerves crossed with distal motor nerves

Motor nerves and sensory nerves conduct signals in different directions and function in different ways.In the surgical treatment of peripheral nerve injuries,the best prognosis is obtained by keeping the motor and sensory nerves separated and repairing the nerves using the suture method.However,the clinical consequences of connections between sensory and motor nerves currently remain unknown.In this study,we analyzed the anatomical structure of the rat femoral nerve,and observed the motor and sensory branches of the femoral nerve in the quadriceps femoris.After ligation of the nerves,the proximal end of the sensory nerve was connected with the distal end of the motor nerve,followed by observation of the changes in the newly-formed regenerated nerve fibers.Acetylcholinesterase staining was used to distinguish between the myelinated and unmyelinated motor and sensory nerves.Denervated muscle and newly formed nerves were compared in terms of morphology,electrophysiology and histochemistry.At 8 weeks after connection,no motor nerve fibers were observed on either side of the nerve conduit and the number of nerve fibers increased at the proximal end.The proportion of newly-formed motor and sensory fibers was different on both sides of the conduit.The area occupied by autonomic nerves in the proximal regenerative nerve was limited,but no distinct myelin sheath was visible in the distal nerve.These results confirm that sensory and motor nerves cannot be effectively connected.Moreover,the change of target organ at the distal end affects the type of nerves at the proximal end.

Identification of four differentially expressed genes associated with acute and chronic spinal cord injury based on bioinformatics data

Complex pathological changes occur during the development of spinal cord injury(SCI),and determining the underlying molecular events that occur during SCI is necessary for the development of promising molecular targets and therapeutic strategies.This study was designed to explore differentially expressed genes(DEGs)associated with the acute and chronic stages of SCI using bioinformatics analysis.Gene expression profiles(GSE45006,GSE93249,and GSE45550)were downloaded from the Gene Expression Omnibus database.SCI-associated DEGs from rat samples were identified,and Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed.In addition,a protein-protein interaction network was constructed.Approximately 66 DEGs were identified in GSE45550 between 3–14 days after SCI,whereas 2418 DEGs were identified in GSE450061–56 days after SCI.Moreover,1263,195,and 75 overlapping DEGs were identified between these two expression profiles,3,7/8,and 14 days after SCI,respectively.Additionally,16 overlapping DEGs were obtained in GSE450061–14 days after SCI,including Pank1,Hn1,Tmem150c,Rgd1309676,Lpl,Mdh1,Nnt,Loc100912219,Large1,Baiap2,Slc24a2,Fundc2,Mrps14,Slc16a7,Obfc1,and Alpk3.Importantly,3882 overlapping DEGs were identified in GSE932491–6 months after SCI,including 3316 protein-coding genes and 567 long non-coding RNA genes.A comparative analysis between GSE93249 and GSE45006 resulted in the enrichment of 1135 overlapping DEGs.The significant functions of these 1135 genes were correlated with the response to the immune effector process,the innate immune response,and cytokine production.Moreover,the biological processes and KEGG pathways of the overlapping DEGs were significantly enriched in immune system-related pathways,osteoclast differentiation,the nuclear factor-κB signaling pathway,and the chemokine signaling pathway.Finally,an analysis of the overlapping DEGs associated with both acute and chronic SCI,assessed using the expression profiles GSE93249 and GSE45006,identified four overlapping DEGs:Slc16a7,Alpk3,Lpl and Nnt.These findings may be useful for revealing the biological processes associated with SCI and the development of targeted intervention strategies.

Brain functional remodeling caused by sciatic nerve transposition repair in rats identified by multiplemodel resting-state blood oxygenation level-dependent functional magnetic resonance imaging analysis

Lower extremity nerve transposition repair has become an important treatment strategy for peripheral nerve injury;however, brain changes caused by this surgical procedure remain unclear. In this study, the distal stump of the right sciatic nerve in a rat model of sciatic nerve injury was connected to the proximal end of the left sciatic nerve using a chitin conduit. Neuroelectrophysiological test showed that the right lower limb displayed nerve conduction, and the structure of myelinated nerve fibers recovered greatly. Muscle wet weight of the anterior tibialis and gastrocnemius recovered as well. Multiple-model resting-state blood oxygenation level-dependent functional magnetic resonance imaging analysis revealed functional remodeling in multiple brain regions and the re-establishment of motor and sensory functions through a new reflex arc. These findings suggest that sciatic nerve transposition repair induces brain functional remodeling. The study was approved by the Ethics Committee of Peking University People's Hospital on December 9, 2015(approval No. 2015-50).

Comparison of commonly used retrograde tracers in rat spinal motor neurons

The purpose of this study was to investigate the effect of four fluorescent dyes, True Blue（TB）, Fluoro-Gold（FG）, Fluoro-Ruby（FR）, and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate（Di I）, in retrograde tracing of rat spinal motor neurons. We transected the muscle branch of the rat femoral nerve and applied each tracer to the proximal stump in single labeling experiments, or combinations of tracers（FG-Di I and TB-Di I） in double labeling experiments. In the single labeling experiments, significantly fewer labeled motor neurons were observed after FR labeling than after TB, FG, or Di I, 3 days after tracer application. By 1 week, there were no significant differences in the number of labeled neurons between the four groups. In the double-labeling experiment, the number of double-labeled neurons in the FG-Di I group was not significantly different from that in the TB-Di I group 1 week after tracer application. Our findings indicate that TB, FG, and Di I have similar labeling efficacies in the retrograde labeling of spinal motor neurons in the rat femoral nerve when used alone. Furthermore, combinations of Di I and TB or FG are similarly effective. Therefore, of the dyes studied, TB, FG and Di I, and combinations of Di I with TB or FG, are the most suitable for retrograde labeling studies of motor neurons in the rat femoral nerve.

Repair of long segmental ulnar nerve defects in rats by several different kinds of nerve transposition

Multiple regeneration of axonal buds has been shown to exist during the repair of peripheral nerve injury, which confirms a certain repair potential of the injured peripheral nerve. Therefore, a systematic nerve transposition repair technique has been proposed to treat severe peripheral nerve injury. During nerve transposition repair, the regenerated nerve fibers of motor neurons in the anterior horn of the spinal cord can effectively grow into the repaired distal nerve and target muscle tissues, which is conducive to the recovery of motor function. The aim of this study was to explore regeneration and nerve functional recovery after repairing a long-segment peripheral nerve defect by transposition of different donor nerves. A long-segment(2 mm) ulnar nerve defect in Sprague-Dawley rats was repaired by transposition of the musculocutaneous nerve, medial pectoral nerve, muscular branches of the radial nerve and anterior interosseous nerve(pronator quadratus muscle branch). In situ repair of the ulnar nerve was considered as a control. Three months later, wrist flexion function, nerve regeneration and innervation muscle recovery in rats were assessed using neuroelectrophysiological testing, osmic acid staining and hematoxylin-eosin staining, respectively. Our findings indicate that repair of a long-segment ulnar nerve defect with different donor nerve transpositions can reinnervate axonal function of motor neurons in the anterior horn of spinal cord and restore the function of affected limbs to a certain extent.

Chitin scaffold combined with autologous small nerve repairs sciatic nerve defects

Although autologous nerve transplantation is the gold standard for treating peripheral nerve defects,it has many clinical limitations.As an alternative,various tissue-engineered nerve grafts have been developed to substitute for autologous nerves.In this study,a novel nerve graft composed of chitin scaffolds and a small autologous nerve was used to repair sciatic nerve defects in rats.The novel nerve graft greatly facilitated regeneration of the sciatic nerve and myelin sheath,reduced atrophy of the target muscle,and effectively restored neurological function.When the epineurium of the small autogenous nerve was removed,the degree of nerve regeneration was similar to that which occurs after autogenous nerve transplantation.These findings suggest that our novel nerve graft might eventually be a new option for the construction of tissue-engineered nerve scaffolds.The study was approved by the Research Ethics Committee of Peking University People's Hospital(approval No.2019 PHE27)on October 18,2019.

Combining CUBIC Optical Clearing and Thy1-YFP-16 Mice to Observe Morphological Axon Changes During Wallerian Degeneration

Objective:Wallerian degeneration is a pathological process closely related to peripheral nerve regeneration following injury,and includes the disintegration and phagocytosis of peripheral nervous system cells.Traditionally,morphological changes are observed by performing immunofluorescence staining after sectioning,which results in the loss of some histological information.The purpose of this study was to explore a new,nondestmetive,and systematic method for observing axonal histological changes during Wallerian degeneration.Methods:Thirty male Thy1-YFP-16 mice(SPF grade,6 weeks old,20±5 g)were randomly selected and divided into clear,unobstructed brain imaging cocktails and computational analysis(CUBIC)optical clearing(n=15)and traditional method groups(n=15).Five mice in each group were sacrificed at 1st,3rd,and 5th day following a crush operation.The histological axon changes were observed by CUBIC light optical clearing treatment,direct tissue section imaging,and HE staining.Results:The results revealed that,compared with traditional imaging methods,there was no physical damage to the samples,which allowed for three-dimensional and deep-seated tissue imaging through CUBIC.Local image information could be nicely obtained by direct fluorescence imaging and HE staining,but it was difficult to obtain image information of the entire sample.At the same time,the image information obtained by fluorescence imaging and HE staining was partially lost.Conclusion:The combining of CUBIC and Thy1-YFP transgenic mice allowed for a clear and comprehensive observation of histological changes of axons in Wallerian degeneration.

Territory maximization hypothesis during peripheral nerve regeneration

Territory awareness refers to the notion that an organism lives in a territory, considers this territory its own, and prevents entry of other organisms. Generally, an organism maximizes its territory for best survival advantages, which subsequently allows for species continuation.