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Zhang M, Li C, Zhou LP, Pi W, Zhang PX. Polymer Scaffolds for Biomedical Applications in Peripheral Nerve Reconstruction. Molecules 2021; 26:molecules26092712. [PMID: 34063072 PMCID: PMC8124340 DOI: 10.3390/molecules26092712] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 04/25/2021] [Accepted: 04/27/2021] [Indexed: 11/20/2022] Open
Abstract
The nervous system is a significant part of the human body, and peripheral nerve injury caused by trauma can cause various functional disorders. When the broken end defect is large and cannot be repaired by direct suture, small gap sutures of nerve conduits can effectively replace nerve transplantation and avoid the side effect of donor area disorders. There are many choices for nerve conduits, and natural materials and synthetic polymers have their advantages. Among them, the nerve scaffold should meet the requirements of good degradability, biocompatibility, promoting axon growth, supporting axon expansion and regeneration, and higher cell adhesion. Polymer biological scaffolds can change some shortcomings of raw materials by using electrospinning filling technology and surface modification technology to make them more suitable for nerve regeneration. Therefore, polymer scaffolds have a substantial prospect in the field of biomedicine in future. This paper reviews the application of nerve conduits in the field of repairing peripheral nerve injury, and we discuss the latest progress of materials and fabrication techniques of these polymer scaffolds.
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Affiliation(s)
- Meng Zhang
- Department of Orthopedics and Trauma, Peking University People’s Hospital, Beijing 100083, China; (M.Z.); (C.L.); (W.P.)
- Key Laboratory of Trauma and Neural Regeneration, Peking University, Beijing 100083, China
| | - Ci Li
- Department of Orthopedics and Trauma, Peking University People’s Hospital, Beijing 100083, China; (M.Z.); (C.L.); (W.P.)
- Key Laboratory of Trauma and Neural Regeneration, Peking University, Beijing 100083, China
| | - Li-Ping Zhou
- Beijing Key Laboratory for Bioengineering and Sensing Technology, Daxing Research Institute, School of Chemistry & Biological Engineering, University of Science & Technology Beijing, Beijing 100083, China;
| | - Wei Pi
- Department of Orthopedics and Trauma, Peking University People’s Hospital, Beijing 100083, China; (M.Z.); (C.L.); (W.P.)
- Key Laboratory of Trauma and Neural Regeneration, Peking University, Beijing 100083, China
| | - Pei-Xun Zhang
- Department of Orthopedics and Trauma, Peking University People’s Hospital, Beijing 100083, China; (M.Z.); (C.L.); (W.P.)
- Key Laboratory of Trauma and Neural Regeneration, Peking University, Beijing 100083, China
- National Center for Trauma Medicine, Beijing 100083, China
- Correspondence:
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Palombella S, Guiotto M, Higgins GC, Applegate LL, Raffoul W, Cherubino M, Hart A, Riehle MO, di Summa PG. Human platelet lysate as a potential clinical-translatable supplement to support the neurotrophic properties of human adipose-derived stem cells. Stem Cell Res Ther 2020; 11:432. [PMID: 33023632 PMCID: PMC7537973 DOI: 10.1186/s13287-020-01949-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Accepted: 09/24/2020] [Indexed: 02/06/2023] Open
Abstract
Background The autologous nerve graft, despite its donor site morbidity and unpredictable functional recovery, continues to be the gold standard in peripheral nerve repair. Rodent research studies have shown promising results with cell transplantation of human adipose-derived stem cells (hADSC) in a bioengineered conduit, as an alternative strategy for nerve regeneration. To achieve meaningful clinical translation, cell therapy must comply with biosafety. Cell extraction and expansion methods that use animal-derived products, including enzymatic adipose tissue dissociation and the use of fetal bovine serum (FBS) as a culture medium supplement, have the potential for transmission of zoonotic infectious and immunogenicity. Human-platelet-lysate (hPL) serum has been used in recent years in human cell expansion, showing reliability in clinical applications. Methods We investigated whether hADSC can be routinely isolated and cultured in a completely xenogeneic-free way (using hPL culture medium supplement and avoiding collagenase digestion) without altering their physiology and stem properties. Outcomes in terms of stem marker expression (CD105, CD90, CD73) and the osteocyte/adipocyte differentiation capacity were compared with classical collagenase digestion and FBS-supplemented hADSC expansion. Results We found no significant differences between the two examined extraction and culture protocols in terms of cluster differentiation (CD) marker expression and stem cell plasticity, while hADSC in hPL showed a significantly higher proliferation rate when compared with the usual FBS-added medium. Considering the important key growth factors (particularly brain-derived growth factor (BDNF)) present in hPL, we investigated a possible neurogenic commitment of hADSC when cultured with hPL. Interestingly, hADSC cultured in hPL showed a statistically higher secretion of neurotrophic factors BDNF, glial cell-derived growth factor (GDNF), and nerve-derived growth factor (NFG) than FBS-cultured cells. When cocultured in the presence of primary neurons, hADSC which had been grown under hPL supplementation, showed significantly enhanced neurotrophic properties. Conclusions The hPL-supplement medium could improve cell proliferation and neurotropism while maintaining stable cell properties, showing effectiveness in clinical translation and significant potential in peripheral nerve research.
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Affiliation(s)
- Silvia Palombella
- Unit of Regenerative Therapy, Service of Plastic, Reconstructive and Hand Surgery, Department of Musculoskeletal Medicine, Lausanne University Hospital, Lausanne, Switzerland. .,Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy.
| | - Martino Guiotto
- Department of Plastic, Reconstructive and Hand Surgery, Centre Hospitalier Universitaire Vaudois (CHUV), Rue du Bugnon, 21, 1011, Lausanne, Switzerland.,Centre for Cellular Microenvironment (CeMi), University of Glasgow, Glasgow, UK
| | - Gillian C Higgins
- Centre for Cellular Microenvironment (CeMi), University of Glasgow, Glasgow, UK.,Canniesburn Plastic Surgery Unit, Glasgow Royal Infirmary, Glasgow, UK
| | - Laurent L Applegate
- Unit of Regenerative Therapy, Service of Plastic, Reconstructive and Hand Surgery, Department of Musculoskeletal Medicine, Lausanne University Hospital, Lausanne, Switzerland
| | - Wassim Raffoul
- Department of Plastic, Reconstructive and Hand Surgery, Centre Hospitalier Universitaire Vaudois (CHUV), Rue du Bugnon, 21, 1011, Lausanne, Switzerland
| | - Mario Cherubino
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
| | - Andrew Hart
- Centre for Cellular Microenvironment (CeMi), University of Glasgow, Glasgow, UK.,Canniesburn Plastic Surgery Unit, Glasgow Royal Infirmary, Glasgow, UK
| | - Mathis O Riehle
- Centre for Cellular Microenvironment (CeMi), University of Glasgow, Glasgow, UK
| | - Pietro G di Summa
- Department of Plastic, Reconstructive and Hand Surgery, Centre Hospitalier Universitaire Vaudois (CHUV), Rue du Bugnon, 21, 1011, Lausanne, Switzerland.
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Du Z, Yin S, Song X, Zhang L, Yue S, Jia X, Zhang Y. Identification of Differentially Expressed Genes and Key Pathways in the Dorsal Root Ganglion After Chronic Compression. Front Mol Neurosci 2020; 13:71. [PMID: 32431596 PMCID: PMC7214750 DOI: 10.3389/fnmol.2020.00071] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 04/14/2020] [Indexed: 12/31/2022] Open
Abstract
Neuropathic pain (NP) is caused by primary or secondary impairment of the peripheral or central nervous systems. Its etiology is complex and involves abnormal patterns of gene expression and pathway activation. Using bioinformatics analysis, we aimed to identify NP-associated changes in genes and pathways in L4 and L5 dorsal root ganglia (DRG) in a rat model of NP induced by chronic compression of the DRG (CCD). Genome-wide transcriptional analyses were used to elucidate the molecular mechanisms underlying NP. We screened differentially expressed genes (DEGs) 7 days after CCD in comparison with sham-operated controls. Quantitative real-time polymerase chain reaction (RT-qPCR) and western blotting were used to confirm the presence of key DEGs. Kyoto Encyclopedia of Genes and Genomes (KEGG)-pathway analysis of DEGs and global signal transduction network analysis of DEGs were also conducted. The CCD group developed clear mechanical and thermal allodynia in the ipsilateral hind paw compared with the sham group. This comparison identified 1,887 DEGs, with 1156 upregulated and 731 downregulated DEGs, and 123 DEG-enriched pathways. We identified the key candidate genes that might play a role in the development of NP, namely syndecan 1 (Sdc1), phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit gamma (Pi3k), Janus kinase 2 (Jak2), jun proto-oncogene, AP-1 transcription factor subunit (Jun), and interleukin 6 (IL-6) by analyzing the global signal transduction network. RT-qPCR and western blot analysis confirmed the microarray results. The DEGs Sdc1, Pi3k, Jak2, Jun, and IL-6, and the cytokine signaling pathway, the neuroactive ligand-receptor interaction, the toll-like receptor signaling pathway, and the PI3K-Akt signaling pathway may have decisive modulatory roles in both nerve regeneration and NP. These results provide deeper insight into the mechanism underlying NP and promising therapeutic targets for its treatment.
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Affiliation(s)
- Zhanhui Du
- Department of Physical Medicine & Rehabilitation, Qilu Hospital, Shandong University, Jinan, China.,Heart Center, Qingdao Women and Children's Hospital, Qingdao, China
| | - Sen Yin
- Department of Neurology, Qilu Hospital, Shandong University, Jinan, China
| | - Xiuhui Song
- Department of Neurosurgery, The People's Hospital of Jimo City, Qingdao, China
| | - Lechi Zhang
- Department of Physical Medicine & Rehabilitation, Suzhou Hospital Affiliated to Nanjing Medical University, Suzhou, China
| | - Shouwei Yue
- Department of Physical Medicine & Rehabilitation, Qilu Hospital, Shandong University, Jinan, China
| | - Xiaofeng Jia
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD, United States.,Department of Orthopaedics, Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, MD, United States.,Departments of Biomedical Engineering, Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Yang Zhang
- Department of Physical Medicine & Rehabilitation, Qilu Hospital, Shandong University, Jinan, China.,Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD, United States
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Li S, Tian X, Fan J, Tong H, Ao Q, Wang X. Chitosans for Tissue Repair and Organ Three-Dimensional (3D) Bioprinting. MICROMACHINES 2019; 10:E765. [PMID: 31717955 PMCID: PMC6915415 DOI: 10.3390/mi10110765] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 11/04/2019] [Accepted: 11/05/2019] [Indexed: 12/17/2022]
Abstract
Chitosan is a unique natural resourced polysaccharide derived from chitin with special biocompatibility, biodegradability, and antimicrobial activity. During the past three decades, chitosan has gradually become an excellent candidate for various biomedical applications with prominent characteristics. Chitosan molecules can be chemically modified, adapting to all kinds of cells in the body, and endowed with specific biochemical and physiological functions. In this review, the intrinsic/extrinsic properties of chitosan molecules in skin, bone, cartilage, liver tissue repair, and organ three-dimensional (3D) bioprinting have been outlined. Several successful models for large scale-up vascularized and innervated organ 3D bioprinting have been demonstrated. Challenges and perspectives in future complex organ 3D bioprinting areas have been analyzed.
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Affiliation(s)
- Shenglong Li
- Center of 3D Printing & Organ Manufacturing, School of Fundamental Sciences, China Medical University (CMU), No. 77 Puhe Road, Shenyang North New Area, Shenyang 110122, China; (S.L.); (X.T.); (J.F.); (H.T.); (Q.A.)
| | - Xiaohong Tian
- Center of 3D Printing & Organ Manufacturing, School of Fundamental Sciences, China Medical University (CMU), No. 77 Puhe Road, Shenyang North New Area, Shenyang 110122, China; (S.L.); (X.T.); (J.F.); (H.T.); (Q.A.)
| | - Jun Fan
- Center of 3D Printing & Organ Manufacturing, School of Fundamental Sciences, China Medical University (CMU), No. 77 Puhe Road, Shenyang North New Area, Shenyang 110122, China; (S.L.); (X.T.); (J.F.); (H.T.); (Q.A.)
| | - Hao Tong
- Center of 3D Printing & Organ Manufacturing, School of Fundamental Sciences, China Medical University (CMU), No. 77 Puhe Road, Shenyang North New Area, Shenyang 110122, China; (S.L.); (X.T.); (J.F.); (H.T.); (Q.A.)
| | - Qiang Ao
- Center of 3D Printing & Organ Manufacturing, School of Fundamental Sciences, China Medical University (CMU), No. 77 Puhe Road, Shenyang North New Area, Shenyang 110122, China; (S.L.); (X.T.); (J.F.); (H.T.); (Q.A.)
| | - Xiaohong Wang
- Center of 3D Printing & Organ Manufacturing, School of Fundamental Sciences, China Medical University (CMU), No. 77 Puhe Road, Shenyang North New Area, Shenyang 110122, China; (S.L.); (X.T.); (J.F.); (H.T.); (Q.A.)
- Center of Organ Manufacturing, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
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Boecker A, Daeschler SC, Kneser U, Harhaus L. Relevance and Recent Developments of Chitosan in Peripheral Nerve Surgery. Front Cell Neurosci 2019; 13:104. [PMID: 31019452 PMCID: PMC6458244 DOI: 10.3389/fncel.2019.00104] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Accepted: 02/28/2019] [Indexed: 12/20/2022] Open
Abstract
Developments in tissue engineering yield biomaterials with different supporting strategies to promote nerve regeneration. One promising material is the naturally occurring chitin derivate chitosan. Chitosan has become increasingly important in various tissue engineering approaches for peripheral nerve reconstruction, as it has demonstrated its potential to interact with regeneration associated cells and the neural microenvironment, leading to improved axonal regeneration and less neuroma formation. Moreover, the physiological properties of its polysaccharide structure provide safe biodegradation behavior in the absence of negative side effects or toxic metabolites. Beneficial interactions with Schwann cells (SC), inducing differentiation of mesenchymal stromal cells to SC-like cells or creating supportive conditions during axonal recovery are only a small part of the effects of chitosan. As a result, an extensive body of literature addresses a variety of experimental strategies for the different types of nerve lesions. The different concepts include chitosan nanofibers, hydrogels, hollow nerve tubes, nerve conduits with an inner chitosan layer as well as hybrid architectures containing collagen or polyglycolic acid nerve conduits. Furthermore, various cell seeding concepts have been introduced in the preclinical setting. First translational concepts with hollow tubes following nerve surgery already transferred the promising experimental approach into clinical practice. However, conclusive analyses of the available data and the proposed impact on the recovery process following nerve surgery are currently lacking. This review aims to give an overview on the physiologic properties of chitosan, to evaluate its effect on peripheral nerve regeneration and discuss the future translation into clinical practice.
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Affiliation(s)
- A Boecker
- Department of Hand, Plastic and Reconstructive Surgery, Burn Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, Germany
| | - S C Daeschler
- Department of Hand, Plastic and Reconstructive Surgery, Burn Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, Germany
| | - U Kneser
- Department of Hand, Plastic and Reconstructive Surgery, Burn Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, Germany
| | - L Harhaus
- Department of Hand, Plastic and Reconstructive Surgery, Burn Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, Germany
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Yi S, Xu L, Gu X. Scaffolds for peripheral nerve repair and reconstruction. Exp Neurol 2018; 319:112761. [PMID: 29772248 DOI: 10.1016/j.expneurol.2018.05.016] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 05/05/2018] [Accepted: 05/13/2018] [Indexed: 12/22/2022]
Abstract
Trauma-associated peripheral nerve defect is a widespread clinical problem. Autologous nerve grafting, the current gold standard technique for the treatment of peripheral nerve injury, has many internal disadvantages. Emerging studies showed that tissue engineered nerve graft is an effective substitute to autologous nerves. Tissue engineered nerve graft is generally composed of neural scaffolds and incorporating cells and molecules. A variety of biomaterials have been used to construct neural scaffolds, the main component of tissue engineered nerve graft. Synthetic polymers (e.g. silicone, polyglycolic acid, and poly(lactic-co-glycolic acid)) and natural materials (e.g. chitosan, silk fibroin, and extracellular matrix components) are commonly used along or together to build neural scaffolds. Many other materials, including the extracellular matrix, glass fabrics, ceramics, and metallic materials, have also been used to construct neural scaffolds. These biomaterials are fabricated to create specific structures and surface features. Seeding supporting cells and/or incorporating neurotrophic factors to neural scaffolds further improve restoration effects. Preliminary studies demonstrate that clinical applications of these neural scaffolds achieve satisfactory functional recovery. Therefore, tissue engineered nerve graft provides a good alternative to autologous nerve graft and represents a promising frontier in neural tissue engineering.
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Affiliation(s)
- Sheng Yi
- Key laboratory of neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Lai Xu
- Key laboratory of neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China
| | - Xiaosong Gu
- Key laboratory of neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu, China.
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Zhao H, Duan LJ, Sun QL, Gao YS, Yang YD, Tang XS, Zhao DY, Xiong Y, Hu ZG, Li CH, Chen SX, Liu T, Yu X. Identification of Key Pathways and Genes in L4 Dorsal Root Ganglion (DRG) After Sciatic Nerve Injury via Microarray Analysis. J INVEST SURG 2018; 33:172-180. [PMID: 29672183 DOI: 10.1080/08941939.2018.1452996] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Background: Peripheral nerve injury (PNI) has devastating consequences. Dorsal root ganglion as a pivotal locus participates in the process of neuropathic pain and nerve regeneration. In recent years, gene sequencing technology has seen rapid rise in the biomedicine field. So, we attempt to gain insight into in the mechanism of neuropathic pain and nerve regeneration in the transcriptional level and to explore novel genes through bioinformatics analysis. Methods: The gene expression profiles of GSE96051 were downloaded from GEO database. The gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were performed, and protein-protein interaction (PPI) network of the differentially expressed genes (DEGs) was constructed by Cytoscape software. Results: Our results showed that both IL-6 and Jun genes and the signaling pathway of MAPK, apoptosis, P53 present their vital modulatory role in nerve regeneration and neuropathic pain. Noteworthy, 13 hub genes associated with neuropathic pain and nerve regeneration, including Ccl12, Ppp1r15a, Cdkn1a, Atf3, Nts, Dusp1, Ccl7, Csf, Gadd45a, Serpine1, Timp1 were rarely reported in PubMed database, these genes may provide us the new orientation in experimental research and clinical study. Conclusions: Our results may provide more deep insight into the mechanism and a promising therapeutic target. The next step is to put our emphasis on an experiment level and to verify the novel genes from 13 hub genes.
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Affiliation(s)
- He Zhao
- Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Li-Jun Duan
- Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China.,Department of Orthopedics, Bayannaoer City Hospital, Bayannaoer City, Inner Mongolia, China
| | - Qing-Ling Sun
- Department of Geriatric, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Yu-Shan Gao
- Department of Basic Medical Sciences, Beijing University of Chinese Medicine, Beijing, China
| | - Yong-Dong Yang
- Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Xiang-Sheng Tang
- Department of Orthopedics, China-Japan Friendship Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Ding-Yan Zhao
- Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Yang Xiong
- Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Zhen-Guo Hu
- Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Chuan-Hong Li
- Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Si-Xue Chen
- Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Tao Liu
- Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Xing Yu
- Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
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Past, Present, and Future of Nerve Conduits in the Treatment of Peripheral Nerve Injury. BIOMED RESEARCH INTERNATIONAL 2015; 2015:237507. [PMID: 26491662 PMCID: PMC4600484 DOI: 10.1155/2015/237507] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 05/12/2015] [Accepted: 05/19/2015] [Indexed: 01/03/2023]
Abstract
With significant advances in the research and application of nerve conduits, they have been used to repair peripheral nerve injury for several decades. Nerve conduits range from biological tubes to synthetic tubes, and from nondegradable tubes to biodegradable tubes. Researchers have explored hollow tubes, tubes filled with scaffolds containing neurotrophic factors, and those seeded with Schwann cells or stem cells. The therapeutic effect of nerve conduits is improving with increasing choice of conduit material, new construction of conduits, and the inclusion of neurotrophic factors and support cells in the conduits. Improvements in functional outcomes are expected when these are optimized for use in clinical practice.
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