Peripheral Nerve Tissue Engineering and Regeneration

Preface
Acknowledgments
Contents
About the Editors
Contributors
The History of Nerve Repair
	1 Introduction
		1.1 The Organization of the Nervous System
			1.1.1 The Structure of a Peripheral Nerve
		1.2 Wallerian Degeneration: An Overview
	2 The History of Nerve Repair
	3 Conclusions
	References
Part I: The Peripheral Nerve Repair Environment
	Blood Supply and Microcirculation of the Peripheral Nerve
		1 Introduction
		2 Historical Overview
		3 Embryology and Anatomy
			3.1 Embryology of the Peripheral Neurovascular System
			3.2 Extrinsic and Intrinsic System
			3.3 The Blood-Nerve Interface
			3.4 The Lymphatic System of the Peripheral Nerve
		4 Physiology of Neural Microcirculation
			4.1 Regulation of Neural Microcirculation
		5 Pathophysiological Aspects of Neural Microcirculation
			5.1 Nerve Compression
			5.2 Nerve Crush
			5.3 Nerve Transection
			5.4 Chronic Constriction Injury
			5.5 Nerve Stretching
			5.6 Neuroma
			5.7 Neuropathies
			5.8 Diabetic Neuropathy
		6 Role of Neural Vascularization and Microcirculation in Peripheral Nerve Regeneration
		7 Studying Neural Vascularity and Microcirculation
		8 Clinical Applications to Improve Vascularization and Microcirculation of Peripheral Nerves
			8.1 Vascularized Nerve Grafts
			8.2 Nerve Guidance Conduits with Implanted Vasculature (See Chapter ``Biomaterials and Scaffolds for Repair of the Peripheral ...
			8.3 Generation of Vascularized Nerve Grafts and Conduits via Arteriovenous Shunting
			8.4 Generation of Vascularized Biogenic Conduits
			8.5 Enhancement of Vascularization by Surgical Angiogenesis
			8.6 Bioengineered Vascularized Neural Tissues
			8.7 Delivery of Stem Cells to Improve Vascularization
		9 Conclusions
		References
	The Immune Response and Implications for Nerve Repair
		1 Introduction
		2 Peripheral Nerve Repair Strategies
		3 Mechanisms of Rejection
			3.1 Innate Immunity
			3.2 Adaptive Immunity
			3.3 The Major Histocompatibility Complex
			3.4 Antigen Processing and Presentation
			3.5 Transplant Rejection
		4 Peripheral Nervous System Immunology
			4.1 The Immune Cell Response to Nerve Injury
			4.2 The Immune Response to Peripheral Nerve Grafts
		5 Strategies for Preventing Rejection of Peripheral Nerve Transplants
			5.1 Pharmacological Immunosuppression
			5.2 Costimulation Blockade
			5.3 Cotransplantation of Regulatory T Cells
			5.4 Modifying the Immunogenicity of Donor Cells
		6 Conclusions
		References
	Autonomic Nervous System Repair and Regeneration
		1 Introduction
		2 Sympathetic Nervous System
		3 Parasympathetic Nervous System
		4 Enteric Nervous System
		5 Peripheral Nerve Injury Classification
		6 Axon Regrowth in the Autonomic Nervous System
		7 Clinical Iatrogenic Damage Affecting Autonomic Nerves
		8 Heart
		9 Prostate
		10 Uterus
		11 Factors Influencing Regeneration of the Autonomic Nervous System
		12 Experimental Models to Study Autonomic Nervous System Regeneration
		13 Postnatal Neurogenesis in the Autonomic Nervous System
		14 Conclusions
		References
Part II: Models and Evaluation of Peripheral Nerve Regeneration
	Appropriate Animal Models for Translational Nerve Research
		1 Introduction
		2 Translational Aspects Should Already Be Considered for In Vitro Studies
		3 The Obstacles in Making Preclinical In Vivo Studies Strong from a Translational Point of View
		4 Well-Thought-Out Rat Studies Provide Important Information After Comprehensive Functional Assessment
		5 The Rat Sciatic Nerve Model
		6 The Rat Median Nerve Model
		7 The Rat as Model Organism for Peripheral Nerve Repair Under Diabetic Conditions
		8 Other Species as Model Organism for Peripheral Nerve Repair: Addressing the Long Gap
		9 Final Consideration of Appropriate Control Groups, Sex, Age, and Rat Strain of Choice
		10 Conclusions
		References
	Basic Nerve Histology and Histological Analyses Following Peripheral Nerve Repair and Regeneration
		1 Introduction
		2 Basic Histology, Degeneration, and Nerve Tissue Regeneration
			2.1 Basic Histology
				2.1.1 The Parenchyma
				2.1.2 The Stroma
			2.2 Degeneration and Regeneration of Peripheral Nerves
				2.2.1 Neuron Body Response to Peripheral Nerve Injury
				2.2.2 Changes from the Proximal to the Distal Nerve Stumps
		3 Histological Techniques
			3.1 Histological Techniques for Light Microscopy
				3.1.1 Tissue Fixation and Paraffin Embedding
				3.1.2 Cryosectioning
			3.2 Technical Consideration for Electron Microscopy Analyses
		4 Histological Assessment of Peripheral Nerve Tissue Regeneration
			4.1 Staining Methods for Light Microscopy
				4.1.1 Assessment of Nerve Tissue Regeneration
				4.1.2 Assessment of Stromal Regeneration and Remodeling
				4.1.3 Assessment of Host Response
				4.1.4 Quantitative Approaches in Light Microscopy
			4.2 Assessment of Nerve Regeneration by Semithin and Transmission Electron Microscopy
		5 Conclusions
		6 Cross-References
		References
	Mathematical Modeling for Nerve Repair Research
		1 Introduction
			1.1 Background
			1.2 The Role of Mathematical Modeling
		2 Mathematical Frameworks
			2.1 Continuum Frameworks
			2.2 Discrete Models
			2.3 Comparing Discrete and Continuum Frameworks
			2.4 Parameter Optimization and Sensitivity Analyses
		3 Case Studies on the Use of Mathematical Models in PNI Repair
			3.1 The Role of Cell-Seeding in Producing Pro-Angiogenic Factors: A Continuum Approach
				3.1.1 Introduction
				3.1.2 Mathematical Model
				3.1.3 Model Parameterization
				3.1.4 Optimization of Seeding Parameters in an In Vivo Repair Scenario
				3.1.5 Sensitivity Analysis to Inform NRC Design Parameters
				3.1.6 Conclusion
			3.2 The Role of Material Cues in Accelerating Neurite Regrowth: A Discrete Approach
				3.2.1 Introduction
				3.2.2 Computational Model
				3.2.3 Model Parameterization
				3.2.4 Optimization of PGF Number and Radius to Accelerate Neurite Regrowth
				3.2.5 Sensitivity Analysis to Inform Design Features
				3.2.6 Conclusions
		References
Part III: Biomaterials for Peripheral Nerve Regeneration
	Biomaterials and Scaffolds for Repair of the Peripheral Nervous System
		1 Introduction
		2 Peripheral Nerve Injuries, Regeneration, and Current Treatments
			2.1 Peripheral Nerve Injuries and Nerve Regeneration
			2.2 Current Treatments
			2.3 Nerve Guide Conduits Manufactured from Natural Materials
			2.4 Nerve Guide Conduits Manufactured from Synthetic Materials
		3 Natural Materials
			3.1 Collagen
			3.2 Chitosan
			3.3 Silk Fibroin
			3.4 Alginate
			3.5 Hyaluronic Acid
		4 Synthetic Materials
			4.1 Polyhydroxyalkanoates (PHAs)
			4.2 Polycaprolactone (PCL)
			4.3 Poly(L-lactic acid) (PLLA)
			4.4 Polyglycolic Acid (PGA)
			4.5 Poly Lactic-co-Glycolic Acid (PLGA)
			4.6 Poly(glycerol sebacate) (PGS)
		5 Improving Existing Hollow Nerve Guide Conduits
			5.1 Changing the Material of the Hollow Tube
			5.2 Changing the Conduit Design
			5.3 Addition of Channels and Microchannels
			5.4 Addition of Grooves
			5.5 Incorporation of Porosity
			5.6 Intraluminal Guidance
			5.7 Coatings and Surface Chemical Modification
			5.8 Incorporation of Growth Factors
			5.9 Use of Supporting Cells
		6 Conclusions
		References
	Fibrin in Nerve Tissue Engineering
		1 Introduction
		2 What Is Fibrin?
			2.1 Fibrin, the End-Product of Blood Coagulation
			2.2 The Central Role of Fibrin in Wound Healing
			2.3 From Wound Healing to Nerve Regeneration
		3 Mechanisms of Fibrin Formation and Degradation
			3.1 Fibrinogenesis and Fibrin Network Formation
				3.1.1 Fibrinogen, Thrombin, and FXIII
				3.1.2 Fibrinogenesis
			3.2 Fibrinolysis
				3.2.1 Regulation of the Fibrinolytic System
				3.2.2 The Fibrinolytic and Nonfibrinolytic Actions of Plasmin
		4 Characterization of Fibrin as a Matrix for Nerve Repair
			4.1 The Intrinsic Biological Properties of Fibrin
			4.2 Factors Affecting Fibrin Clot Structure and Mechanical Properties
			4.3 Fibrin as a Delivery Matrix for Neuronal and Glial Cells
				4.3.1 Factors Affecting Neuronal and Glial Cell Behavior in Fibrin-Based Culture Systems
				4.3.2 Functionalization Strategies for Neurotrophic Fibrin Matrices
				4.3.3 Fibrin-Based Interpenetrating Polymer Networks
		5 Fibrin in Nerve Regeneration: In Vivo Applications
			5.1 Fibrin Sealant for Sutureless Nerve Repair
			5.2 Fibrin Sealant for Enhancement of Neurorrhaphy Sites
			5.3 Fibrin as a Carrier Matrix: In Vivo
			5.4 Fibrin as a Filler for Nerve Guidance Conduits
			5.5 Conduits and Scaffolds
		6 Conclusions
		References
	Silk Biomaterials in Peripheral Nerve Tissue Engineering
		1 Introduction
		2 Peripheral Nerve Injuries
		3 Strategies for Peripheral Nerve Repair
			3.1 Surgical Intervention
			3.2 Nerve Grafts
			3.3 Artificial Nerve Conduits
		4 Advantages of Silks as Biomaterial in Tissue Engineering
			4.1 Silk
				4.1.1 Silk from Insects
				4.1.2 Silk from Spiders
				4.1.3 Artificially Produced Silk
				4.1.4 Silk Modification
		5 Silk as Biomaterial in Peripheral Nerve Repair
			5.1 Biocompatibility of Silk with Neural Cells
			5.2 Silk-Based Nerve Grafts in Nerve Regeneration
				5.2.1 Silk-Based Conduits
			5.3 Filling Material for Nerve Conduits
				5.3.1 Natural Silk Fibers
				5.3.2 Processed Silk Fibroin Fibers
				5.3.3 Silk-Based Hydrogels
				5.3.4 Biofunctionalization of Silk-Based Conduits
				5.3.5 Cellular Support
				5.3.6 Growth Factors/Neurotrophic Factors
				5.3.7 ECM-Binding Proteins
				5.3.8 Peptide Sequences
		6 Ongoing Preclinical Studies Using Silk-Based Nerve Conduits
		7 Conclusions
		References
	Collagen Biomaterials for Nerve Tissue Engineering
		1 Introduction
			1.1 Collagen in Native Tissues: Function and Diversity
			1.2 Structure and Biosynthesis
			1.3 Collagen as a Biomaterial
			1.4 Collagen Fabrication and Functionalization for Tissue Engineering Applications
				1.4.1 Decellularized Collagen Biomaterials
				1.4.2 Reconstituted Collagen Biomaterials
		2 Collagen in Nerve Tissue Engineering
			2.1 Collagen in Healthy and Diseased Peripheral Nerves
			2.2 Collagen-Based Nerve Guidance Conduits: Preclinical Studies
				2.2.1 First-Generation Collagen NGCs: Hollow Conduits
				2.2.2 Second-Generation Collagen NGCs
					Intraluminal Fillers
					Anisotropy and Guidance Structures
					Multichannel NGCs
					NGC Modifications and Synergy with Other Nerve Regeneration Therapies
			2.3 Clinically Approved Engineered Collagen Grafts for Nerve Regeneration
		3 Conclusions
		References
Part IV: Therapeutic Options for Peripheral Nerve Regeneration
	Schwann Cells in Nerve Repair and Regeneration
		1 Introduction: The Basics of Regeneration
		2 Schwann Cell Reprogramming Is Related to Injury Responses in Other Tissues
		3 The Repair Schwann Cell Phenotype Emerges Gradually and Fades with Time
		4 Repair Cell Failure and the Underlying Molecular Mechanisms
		5 The Injured Nerve
		6 The Nerve Protective Tissues Are Organized by Developing Schwann Cells
		7 The Schwann Cell Injury Response Is Controlled by Special Signalling Mechanisms
		8 Conclusions
		References
	Therapeutic Cells and Stem Cells for Nerve Regeneration
		1 Introduction
		2 Bone Marrow Stromal Cells for Repair of Peripheral Nerve Lesion
		3 Induced Pluripotent Stem Cells and Their Derivatives
		4 Adipose-Derived Stem Cells as an Alternative Source
		5 Dental Pulp Stem Cells
		6 Hair Follicle-Associated Stem Cells
		7 Conclusions
		References
	Extracellular Vesicles for Nerve Regeneration
		1 Introduction
		2 Biogenesis and Uptake Mechanisms of EVs
		3 EVs Isolation
		4 Preclinical Research on EVs for Nerve Regeneration
			4.1 EVs for Axon Regeneration and Neuroprotection
			4.2 EVs and Schwann Cells
			4.3 EVs and Neuroimmune Modulation
			4.4 EVs and the Neurovascular Reaction
		5 Characterization of EVs
		6 Administering EVs
		7 Engineered EVs
		8 Conclusions
		References
	Drug Therapies for Peripheral Nerve Injuries
		1 Introduction
		2 Potential Cellular Targets for Drug Therapy
			2.1 Neurons
			2.2 Schwann Cells
			2.3 Macrophages
		3 Molecular Signaling Pathways
			3.1 Rho/ROCK Signaling Pathway
		4 Drugs Currently in Research Targeting Commonly Studied Pathways
		5 Drug Screening
		6 Repurposing Drugs for PNI
		7 Drug Delivery
		8 Clinical Trials
		9 Conclusions
		References
Part V: Clinical Aspects
	Surgical Techniques in Nerve Repair
		1 Introduction
		2 Basics of Nerve and Muscle Regeneration
		3 Surgical Treatment According to the Type of Peripheral Nerve Lesion
			3.1 Partial or Complete Transection of a Peripheral Nerve
			3.2 Nerve Defects
				3.2.1 Interfascicular Autologous Nerve Grafting
				3.2.2 Nerve Allografts
				3.2.3 Nerve Conduits
			3.3 Loss of the Proximal Nerve Stump
				3.3.1 Nerve Transfers
				3.3.2 End-to-Side Coaptation
			3.4 Loss of the Distal Nerve Stump
				3.4.1 Direct Nerve-Muscle Neurotization
				3.4.2 Muscle-Tendon Transfer and Joint Fusion
			3.5 Late Reconstruction of Far Proximal Nerve Lesions
				3.5.1 Peripheral Nerve Transfers
				3.5.2 Muscle-Tendon Transfer
				3.5.3 Joint Fusion
			3.6 Nerve Compression Syndromes
				3.6.1 Simple Nerve Compression Syndromes
				3.6.2 Neurolysis
				3.6.3 Direct Epineurial Suture and Nerve Grafting
				3.6.4 Reconstruction of the Gliding Tissue
			3.7 Painful Neuroma Formation
			3.8 Reconstruction of the Brachial Plexus
				3.8.1 Functional Free Muscle Transfer
			3.9 Peripheral Nerve Surgery in Spinal Cord Injuries
		4 Conclusions
		References
	Clinical Outcome Measures Following Peripheral Nerve Repair
		1 Introduction
		2 Peripheral Nerve Anatomy
		3 Classifications of Peripheral Nerve Injuries
		4 Neurobiology of Peripheral Nerve Regeneration
			4.1 Neurapraxia (Grade I Injury)
			4.2 Biological Processes that Underpin Neural Regeneration (Grade II-V Injuries)
			4.3 Changes at the Central Nervous System
			4.4 Changes at the Cell Body and Proximal Stump
			4.5 Changes at the Distal Stump
			4.6 Changes at the Neuromuscular Junction and Within the Muscle
		5 Clinical Measurements of Nerve Injury and Regeneration
			5.1 Sensibility
			5.2 Pain
			5.3 Motor Function
		6 Neurophysiological Investigation of Peripheral Nerve Injuries
			6.1 Nerve Conduction Studies
			6.2 Electromyography
			6.3 Timing of Neurophysiological Assessment
			6.4 Localizing the Lesion
			6.5 Determining the Extent of Neural Injury Using Electro-Diagnostic Testing
			6.6 Conduction Block/Neurapraxia
			6.7 Axonotmesis
			6.8 Neurotmesis
			6.9 Intraoperative Neurophysiology
			6.10 Electrophysiological Correlates of the Recovery of Motor Units
			6.11 Quantitative MUAP Analysis
			6.12 Motor Unit Number Estimation (MUNE)
			6.13 Electrophysiological Correlates of Sensory Function
			6.14 Quantitative Sensory Testing
			6.15 Electrophysiological Correlates of the Response of the CNS to PNI
		7 Imaging of Peripheral Nerve Injuries
			7.1 MRI Findings in Injured Nerves
			7.2 MRI Findings in Denervated Muscle
			7.3 Muscle Volume Changes in Denervated Muscle and the Application of MRI
			7.4 MR Neurography
			7.5 MR Contrast Agents
			7.6 MRN to Quantify Axonal Diameter
			7.7 Tractography
			7.8 Ultrasound
		8 Conclusions
		References
	Regenerative Therapies for Acquired Axonal Neuropathies
		1 Introduction
		2 Innervation of the Skin
		3 Clinical Overview of Acquired Axonal Neuropathies
			3.1 Diabetes
			3.2 Chemotherapy-Induced Peripheral Neurotoxicity
				3.2.1 Neuropathy Secondary to Human Immunodeficiency Virus
				3.2.2 Toxicity of Antiretroviral Drugs
				3.2.3 Hepatitis-C-Virus-Associated Neuropathy
				3.2.4 Campylobacter-Jejuni-Associated Neuropathy
		4 New Insights into Cellular and Molecular Mechanisms of Axonal Degeneration
		5 Outcome Measures to Evaluate Regeneration in Acquired Axonal Neuropathies
		6 Therapeutic Candidates for Regeneration in Acquired Axonal Neuropathies
			6.1 Growth Factors
			6.2 Immunosuppressants
			6.3 Hormones
			6.4 Other Drugs
			6.5 Vitamins
			6.6 Traditional Chinese Medicine
			6.7 Miscellaneous Drugs
		7 Strategies to Deliver Regenerative Therapies for Acquired Axonal Neuropathies
		8 Transdermal Drug Delivery
			8.1 Cell-Penetrating Carrier Peptides
			8.2 Iontopheresis
			8.3 Nanopatch
			8.4 Ultrasound
			8.5 Skin Permeability Considerations
		9 Gene Therapy
		10 Conclusions
		References
	Rehabilitation of Nerve Injuries
		1 Introduction
		2 Personal Factors
			2.1 Biological Factors
			2.2 Psychosocial Factors
		3 Environmental Factors
		4 Body Structure and Function
			4.1 Motor
			4.2 Rehabilitation of the Motor System Following Peripheral Nerve Surgery
				4.2.1 Preoperative
				4.2.2 Postoperative Protective Phase
				4.2.3 Post Protection
				4.2.4 Muscle Activation
			4.3 Adjuncts to Rehabilitation
				4.3.1 Enhancing Cortical Representation Training
				4.3.2 Splinting
				4.3.3 Electrical Stimulation
				4.3.4 Biofeedback
				4.3.5 Hydrotherapy
			4.4 Sensory
			4.5 Sensory Re-education
				4.5.1 Early Stages: Complete Sensory Loss
				4.5.2 Later Stages: Intact Sensory Pathways
				4.5.3 Desensitization
			4.6 Pain
				4.6.1 Transcutaneous Electrical Nerve Stimulation
			4.7 Cold Intolerance
			4.8 Scar Tissue Formation
		5 Activity and Participation
			5.1 Patient Reported Outcomes
			5.2 Clinician Reported Outcomes
			5.3 Splinting/Supports/Orthoses
				5.3.1 Radial Nerve
				5.3.2 Median Nerve
				5.3.3 Ulnar Nerve
				5.3.4 Brachial Plexus
		6 Conclusions
		References
Index