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The Role of Tissue Geometry in Spinal Cord Regeneration. MEDICINA (KAUNAS, LITHUANIA) 2022; 58:medicina58040542. [PMID: 35454380 PMCID: PMC9028021 DOI: 10.3390/medicina58040542] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 04/11/2022] [Indexed: 11/17/2022]
Abstract
Unlike peripheral nerves, axonal regeneration is limited following injury to the spinal cord. While there may be reduced regenerative potential of injured neurons, the central nervous system (CNS) white matter environment appears to be more significant in limiting regrowth. Several factors may inhibit regeneration, and their neutralization can modestly enhance regrowth. However, most investigations have not considered the cytoarchitecture of spinal cord white matter. Several lines of investigation demonstrate that axonal regeneration is enhanced by maintaining, repairing, or reconstituting the parallel geometry of the spinal cord white matter. In this review, we focus on environmental factors that have been implicated as putative inhibitors of axonal regeneration and the evidence that their organization may be an important determinant in whether they inhibit or promote regeneration. Consideration of tissue geometry may be important for developing successful strategies to promote spinal cord regeneration.
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2
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Peressotti S, Koehl GE, Goding JA, Green RA. Self-Assembling Hydrogel Structures for Neural Tissue Repair. ACS Biomater Sci Eng 2021; 7:4136-4163. [PMID: 33780230 PMCID: PMC8441975 DOI: 10.1021/acsbiomaterials.1c00030] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/10/2021] [Indexed: 12/12/2022]
Abstract
Hydrogel materials have been employed as biological scaffolds for tissue regeneration across a wide range of applications. Their versatility and biomimetic properties make them an optimal choice for treating the complex and delicate milieu of neural tissue damage. Aside from finely tailored hydrogel properties, which aim to mimic healthy physiological tissue, a minimally invasive delivery method is essential to prevent off-target and surgery-related complications. The specific class of injectable hydrogels termed self-assembling peptides (SAPs), provide an ideal combination of in situ polymerization combined with versatility for biofunctionlization, tunable physicochemical properties, and high cytocompatibility. This review identifies design criteria for neural scaffolds based upon key cellular interactions with the neural extracellular matrix (ECM), with emphasis on aspects that are reproducible in a biomaterial environment. Examples of the most recent SAPs and modification methods are presented, with a focus on biological, mechanical, and topographical cues. Furthermore, SAP electrical properties and methods to provide appropriate electrical and electrochemical cues are widely discussed, in light of the endogenous electrical activity of neural tissue as well as the clinical effectiveness of stimulation treatments. Recent applications of SAP materials in neural repair and electrical stimulation therapies are highlighted, identifying research gaps in the field of hydrogels for neural regeneration.
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Affiliation(s)
- Sofia Peressotti
- Department
of Bioengineering and Centre for Neurotechnology, Imperial College London, London SW72AS, United Kingdom
| | - Gillian E. Koehl
- Department
of Bioengineering and Centre for Neurotechnology, Imperial College London, London SW72AS, United Kingdom
| | - Josef A. Goding
- Department
of Bioengineering and Centre for Neurotechnology, Imperial College London, London SW72AS, United Kingdom
| | - Rylie A. Green
- Department
of Bioengineering and Centre for Neurotechnology, Imperial College London, London SW72AS, United Kingdom
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3
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Kelly A, Farid N, Krukiewicz K, Belisle N, Groarke J, Waters EM, Trotier A, Laffir F, Kilcoyne M, O'Connor GM, Biggs MJ. Laser-Induced Periodic Surface Structure Enhances Neuroelectrode Charge Transfer Capabilities and Modulates Astrocyte Function. ACS Biomater Sci Eng 2020; 6:1449-1461. [PMID: 33455378 DOI: 10.1021/acsbiomaterials.9b01321] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The brain machine interface (BMI) describes a group of technologies capable of communicating with excitable nervous tissue within the central nervous system (CNS). BMIs have seen major advances in recent years, but these advances have been impeded because of a temporal deterioration in the signal to noise ratio of recording electrodes following insertion into the CNS. This deterioration has been attributed to an intrinsic host tissue response, namely, reactive gliosis, which involves a complex series of immune mediators, resulting in implant encapsulation via the synthesis of pro-inflammatory signaling molecules and the recruitment of glial cells. There is a clinical need to reduce tissue encapsulation in situ and improve long-term neuroelectrode functionality. Physical modification of the electrode surface at the nanoscale could satisfy these requirements by integrating electrochemical and topographical signals to modulate neural cell behavior. In this study, commercially available platinum iridium (Pt/Ir) microelectrode probes were nanotopographically functionalized using femto/picosecond laser processing to generate laser-induced periodic surface structures (LIPSS). Three different topographies and their physical properties were assessed by scanning electron microscopy and atomic force microscopy. The electrochemical properties of these interfaces were investigated using electrochemical impedance spectroscopy and cyclic voltammetry. The in vitro response of mixed cortical cultures (embryonic rat E14/E17) was subsequently assessed by confocal microscopy, ELISA, and multiplex protein array analysis. Overall LIPSS features improved the electrochemical properties of the electrodes, promoted cell alignment, and modulated the expression of multiple ion channels involved in key neuronal functions.
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Affiliation(s)
- Adriona Kelly
- Centre for Research in Medical Devices, National University of Ireland, Galway H91 TK33, Ireland
| | - Nazar Farid
- National Centre for Laser Applications, School of Physics, National University of Ireland, Galway H91 TK33, Ireland
| | - Katarzyna Krukiewicz
- Centre for Research in Medical Devices, National University of Ireland, Galway H91 TK33, Ireland.,Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, Gliwice 44-100, Poland
| | - Nicole Belisle
- Centre for Research in Medical Devices, National University of Ireland, Galway H91 TK33, Ireland
| | - John Groarke
- Centre for Research in Medical Devices, National University of Ireland, Galway H91 TK33, Ireland
| | - Elaine M Waters
- Glycosciences School of Natural Sciences, National University of Ireland, Galway H91 TK33, Ireland
| | - Alexandre Trotier
- Centre for Research in Medical Devices, National University of Ireland, Galway H91 TK33, Ireland
| | - Fathima Laffir
- Bernal Institute, Materials and Surface Science Institute, University of Limerick, Limerick V94 T9PX, Ireland
| | - Michelle Kilcoyne
- Glycosciences School of Natural Sciences, National University of Ireland, Galway H91 TK33, Ireland
| | - Gerard M O'Connor
- Centre for Research in Medical Devices, National University of Ireland, Galway H91 TK33, Ireland.,National Centre for Laser Applications, School of Physics, National University of Ireland, Galway H91 TK33, Ireland
| | - Manus J Biggs
- Centre for Research in Medical Devices, National University of Ireland, Galway H91 TK33, Ireland
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4
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Ayad NME, Kaushik S, Weaver VM. Tissue mechanics, an important regulator of development and disease. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180215. [PMID: 31431174 DOI: 10.1098/rstb.2018.0215] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A growing body of work describes how physical forces in and around cells affect their growth, proliferation, migration, function and differentiation into specialized types. How cells receive and respond biochemically to mechanical signals is a process termed mechanotransduction. Disease may arise if a disruption occurs within this mechanism of sensing and interpreting mechanics. Cancer, cardiovascular diseases and developmental defects, such as during the process of neural tube formation, are linked to changes in cell and tissue mechanics. A breakdown in normal tissue and cellular forces activates mechanosignalling pathways that affect their function and can promote disease progression. The recent advent of high-resolution techniques enables quantitative measurements of mechanical properties of the cell and its extracellular matrix, providing insight into how mechanotransduction is regulated. In this review, we will address the standard methods and new technologies available to properly measure mechanical properties, highlighting the challenges and limitations of probing different length-scales. We will focus on the unique environment present throughout the development and maintenance of the central nervous system and discuss cases where disease, such as brain cancer, arises in response to changes in the mechanical properties of the microenvironment that disrupt homeostasis. This article is part of a discussion meeting issue 'Forces in cancer: interdisciplinary approaches in tumour mechanobiology'.
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Affiliation(s)
- Nadia M E Ayad
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco, San Francisco, CA, USA.,UC Berkeley-UCSF Graduate Program in Bioengineering, San Francisco, CA, USA
| | - Shelly Kaushik
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Valerie M Weaver
- Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco, San Francisco, CA, USA.,Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California San Francisco, San Francisco, CA, USA.,UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA, USA.,Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA.,Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
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5
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Zhang L, Chen S, Liang R, Chen Y, Li S, Li S, Sun Z, Wang Y, Li G, Ming A, Yang Y. Fabrication of alignment polycaprolactone scaffolds by combining use of electrospinning and micromolding for regulating Schwann cells behavior. J Biomed Mater Res A 2018; 106:3123-3134. [PMID: 30260557 DOI: 10.1002/jbm.a.36507] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2018] [Revised: 06/29/2018] [Accepted: 07/12/2018] [Indexed: 12/20/2022]
Abstract
In the present study, a new approach for fabricating micropatterned polycaprolactone (PCL) scaffolds with ridge/groove structure on the surface was developed by combining use of electrospinning and micromolding method. A series of physicochemical properties, including morphology, wettability, component, crystal pattern and mechanical properties, of prepared PCL scaffolds were characterization, respectively. Stability of the micropatterned PCL scaffolds was measured using phosphate buffer solution immersion for a certain period. Then, the regulating effects of the micropatterned PCL scaffolds on attachment, orientation and normal biological function of Schwann cells were evaluated. And the protein adsorption behavior in various PCL scaffolds was also detected. The results showed that the micropatterned PCL scaffolds demonstrated a porous micro/nano complex structure with enhanced hydrophobicity and mechanical properties as a function of electrospun flow-rate of PCL solution. The micropatterned PCL scaffolds possessed good stability and could effectively regulate the attachment and orientation of Schwann cells at the early stage after cell culture. Importantly, the electrospun flow-rate of PCL solution was found to play an important role in scaffold properties, cell behavior and protein adsorption. The micropatterned scaffolds with a flow-rate of PCL solution at 0.12 mL h-1 demonstrated the better regulation on Schwann cells attachment and alignment without negatively affect the normal biological function of the cells. To the best of our knowledge, this is the first report of combining use of electrospinning and micromolding method for preparing artificial nerve implants. The study is anticipated to have potential application in peripheral nerve and other tissue engineering. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3123-3134, 2018.
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Affiliation(s)
- Luzhong Zhang
- Key laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Nantong University, 226001, Nantong, People's Republic of China.,Coinnovation Center of Neuroregeneration, Nantong University, Nantong, People's Republic of China
| | - Shiyu Chen
- Key laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Nantong University, 226001, Nantong, People's Republic of China.,Coinnovation Center of Neuroregeneration, Nantong University, Nantong, People's Republic of China
| | - Ruyu Liang
- School of Life Science, Nantong University, Nantong, People's Republic of China
| | - Yi Chen
- School of Life Science, Nantong University, Nantong, People's Republic of China
| | - Shenjie Li
- School of Medical, Nantong University, Nantong, People's Republic of China
| | - Siqi Li
- School of Medical, Nantong University, Nantong, People's Republic of China
| | - Zedong Sun
- School of Medical, Nantong University, Nantong, People's Republic of China
| | - Yaling Wang
- School of Chemical and Chemistry Engineering, Nantong University, Nantong, People's Republic of China
| | - Guicai Li
- Key laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Nantong University, 226001, Nantong, People's Republic of China.,Coinnovation Center of Neuroregeneration, Nantong University, Nantong, People's Republic of China
| | - Anjie Ming
- Smart Sensing R&D Center, Institute of Microelectronics, Chinese Academy of Sciences, Beijing, 100029, People's Republic of China
| | - Yumin Yang
- Key laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Nantong University, 226001, Nantong, People's Republic of China.,Coinnovation Center of Neuroregeneration, Nantong University, Nantong, People's Republic of China
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Thomson SE, Charalambous C, Smith CA, Tsimbouri PM, Déjardin T, Kingham PJ, Hart AM, Riehle MO. Microtopographical cues promote peripheral nerve regeneration via transient mTORC2 activation. Acta Biomater 2017; 60:220-231. [PMID: 28754648 PMCID: PMC5593812 DOI: 10.1016/j.actbio.2017.07.031] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 07/04/2017] [Accepted: 07/20/2017] [Indexed: 12/16/2022]
Abstract
Despite microsurgical repair, recovery of function following peripheral nerve injury is slow and often incomplete. Outcomes could be improved by an increased understanding of the molecular biology of regeneration and by translation of experimental bioengineering strategies. Topographical cues have been shown to be powerful regulators of the rate and directionality of neurite regeneration, and in this study we investigated the downstream molecular effects of linear micropatterned structures in an organotypic explant model. Linear topographical cues enhanced neurite outgrowth and our results demonstrated that the mTOR pathway is important in regulating these responses. mTOR gene expression peaked between 48 and 72 h, coincident with the onset of rapid neurite outgrowth and glial migration, and correlated with neurite length at 48 h. mTOR protein was located to glia and in a punctate distribution along neurites. mTOR levels peaked at 72 h and were significantly increased by patterned topography (p < 0.05). Furthermore, the topographical cues could override pharmacological inhibition. Downstream phosphorylation assays and inhibition of mTORC1 using rapamycin highlighted mTORC2 as an important mediator, and more specific therapeutic target. Quantitative immunohistochemistry confirmed the presence of the mTORC2 component rictor at the regenerating front where it co-localised with F-actin and vinculin. Collectively, these results provide a deeper understanding of the mechanism of action of topography on neural regeneration, and support the incorporation of topographical patterning in combination with pharmacological mTORC2 potentiation within biomaterial constructs used to repair peripheral nerves. Statement of Significance Peripheral nerve injury is common and functionally devastating. Despite microsurgical repair, healing is slow and incomplete, with lasting functional deficit. There is a clear need to translate bioengineering approaches and increase our knowledge of the molecular processes controlling nerve regeneration to improve the rate and success of healing. Topographical cues are powerful determinants of neurite outgrowth and represent a highly translatable engineering strategy. Here we demonstrate, for the first time, that microtopography potentiates neurite outgrowth via the mTOR pathway, with the mTORC2 subtype being of particular importance. These results give further evidence for the incorporation of microtopographical cues into peripheral nerve regeneration conduits and indicate that mTORC2 may be a suitable therapeutic target to potentiate nerve regeneration.
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7
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Li S, Tuft B, Xu L, Polacco M, Clarke JC, Guymon CA, Hansen MR. Intracellular calcium and cyclic nucleotide levels modulate neurite guidance by microtopographical substrate features. J Biomed Mater Res A 2016; 104:2037-48. [PMID: 27062708 DOI: 10.1002/jbm.a.35738] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 03/29/2016] [Accepted: 04/05/2016] [Indexed: 02/06/2023]
Abstract
Micro- and nanoscale surface features have emerged as potential tools to direct neurite growth into close proximity with next generation neural prosthesis electrodes. However, the signaling events underlying the ability of growth cones to respond to topographical features remain largely unknown. Accordingly, this study probes the influence of [Ca(2+) ]i and cyclic nucleotide levels on the ability of neurites from spiral ganglion neurons (SGNs) to precisely track topographical micropatterns. Photopolymerization and photomasking were used to generate micropatterned methacrylate polymer substrates. Dissociated SGN cultures were plated on the micropatterned surfaces. Calcium influx and release from internal stores were manipulated by elevating extracellular K(+) , maintenance in calcium-free media, or bath application of various calcium channel blockers. Cyclic nucleotide activity was increased by application of cpt-cAMP or 8-Br-cGMP. Elevation of [Ca(2+) ]i by treatment of cultures with elevated potassium reduced neurite alignment to physical microfeatures. Maintenance of cultures in Ca(2+) -free medium or treatment with the non-selective voltage-gated calcium channel blocker cadmium or L-type Ca(2+) channel blocker nifedipine did not signficantly alter SGN neurite alignment. By contrast, ryanodine or xestospongin C, which block release of internal calcium stores via ryanodine-sensitive channels or inositol-1,4,5-trisphosphate receptors respectively, each significantly decreased neurite alignment. Cpt-cAMP significantly reduced neurite alignment while 8-Br-cGMP significantly enhanced neurite alignment. Manipulation of [Ca(2+) ]i or cAMP levels significantly disrupts neurite guidance while elevation of cGMP levels increases neurite alignment. The results suggest intracellular signaling pathways similar to those recruited by chemotactic cues are involved in neurite guidance by topographical features. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2037-2048, 2016.
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Affiliation(s)
- Shufeng Li
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa, 52242.,Department of Otolaryngology, Eye & ENT Hospital of Fudan University, Shanghai, 200031, China
| | - Bradley Tuft
- Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa, 52242
| | - Linjing Xu
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa, 52242
| | - Marc Polacco
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa, 52242
| | - Joseph C Clarke
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa, 52242
| | - C Allan Guymon
- Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa, 52242
| | - Marlan R Hansen
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa, 52242.,Department of Neurosurgery, University of Iowa, Iowa City, Iowa, 52242
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8
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Stukel JM, Willits RK. Mechanotransduction of Neural Cells Through Cell-Substrate Interactions. TISSUE ENGINEERING PART B-REVIEWS 2016; 22:173-82. [PMID: 26669274 DOI: 10.1089/ten.teb.2015.0380] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Neurons and neural stem cells are sensitive to their mechanical and topographical environment, and cell-substrate binding contributes to this sensitivity to activate signaling pathways for basic cell functions. Many transmembrane proteins transmit signals into and out of the cell, including integrins, growth factor receptors, G-protein-coupled receptors, cadherins, cell adhesion molecules, and ion channels. Specifically, integrins are one of the main transmembrane proteins that transmit force across the cell membrane between a cell and its extracellular matrix, making them critical in the study of cell-material interactions. This review focuses on mechanotransduction, defined as the conversion of force a cell generates through cell-substrate bonds to a chemical signal, of neural cells. The chemical signals relay information via pathways through the cellular cytoplasm to the nucleus, where signaling events can affect gene expression. Pathways and the cellular response initiated by substrate binding are explored to better understand their effect on neural cells mechanotransduction. As the results of mechanotransduction affect cell adhesion, cell shape, and differentiation, knowledge regarding neural mechanotransduction is critical for most regenerative strategies in tissue engineering, where novel environments are developed to improve conduit design for central and peripheral nervous system repair in vivo.
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Affiliation(s)
- Jessica M Stukel
- Department of Biomedical Engineering, The University of Akron , Akron, Ohio
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9
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Sweet L, Kang Y, Czisch C, Witek L, Shi Y, Smay J, Plant GW, Yang Y. Geometrical versus Random β-TCP Scaffolds: Exploring the Effects on Schwann Cell Growth and Behavior. PLoS One 2015; 10:e0139820. [PMID: 26444999 PMCID: PMC4596809 DOI: 10.1371/journal.pone.0139820] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Accepted: 09/17/2015] [Indexed: 12/22/2022] Open
Abstract
Numerous studies have demonstrated that Schwann cells (SCs) play a role in nerve regeneration; however, their role in innervating a bioceramic scaffold for potential application in bone regeneration is still unknown. Here we report the cell growth and functional behavior of SCs on β-tricalcium phosphate (β-TCP) scaffolds arranged in 3D printed-lattice (P-β-TCP) and randomly-porous, template-casted (N-β-TCP) structures. Our results indicate that SCs proliferated well and expressed the phenotypic markers p75LNGFR and the S100-β subunit of SCs as well as displayed growth morphology on both scaffolds, but SCs showed spindle-shaped morphology with a significant degree of SCs alignment on the P-β-TCP scaffolds, seen to a lesser degree in the N-β-TCP scaffold. The gene expressions of nerve growth factor (β-ngf), neutrophin–3 (nt–3), platelet-derived growth factor (pdgf-bb), and vascular endothelial growth factor (vegf-a) were higher at day 7 than at day 14. While no significant differences in protein secretion were measured between these last two time points, the scaffolds promoted the protein secretion at day 3 compared to that on the cell culture plates. These results together imply that the β-TCP scaffolds can support SC cell growth and that the 3D-printed scaffold appeared to significantly promote the alignment of SCs along the struts. Further studies are needed to investigate the early and late stage relationship between gene expression and protein secretion of SCs on the scaffolds with refined characteristics, thus better exploring the potential of SCs to support vascularization and innervation in synthetic bone grafts.
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Affiliation(s)
- Lauren Sweet
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, United States of America
- Department of Biology, Stanford University, Stanford, California, United States of America
| | - Yunqing Kang
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, United States of America
- Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, Florida, United States of America
| | - Christopher Czisch
- Department of Neurosurgery, Stanford University, Stanford, California, United States of America
| | - Lukasz Witek
- School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma, United States of America
| | - Yang Shi
- School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma, United States of America
| | - Jim Smay
- School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma, United States of America
| | - Giles W. Plant
- Department of Neurosurgery, Stanford University, Stanford, California, United States of America
| | - Yunzhi Yang
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, United States of America
- Department of Materials Science and Engineering, Stanford University, Stanford, California, United States of America
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
- * E-mail:
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