1
|
Smith TA, Zhou L, Ghergherehchi CL, Mikesh M, Yang CZ, Tucker HO, Allgood J, Bushman JS, Bittner GD. Polyethylene glycol has immunoprotective effects on sciatic allografts, but behavioral recovery and graft tolerance require neurorrhaphy and axonal fusion. Neural Regen Res 2025; 20:1192-1206. [PMID: 38989956 DOI: 10.4103/nrr.nrr-d-23-01220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 02/29/2024] [Indexed: 07/12/2024] Open
Abstract
JOURNAL/nrgr/04.03/01300535-202504000-00033/figure1/v/2024-07-06T104127Z/r/image-tiff Behavioral recovery using (viable) peripheral nerve allografts to repair ablation-type (segmental-loss) peripheral nerve injuries is delayed or poor due to slow and inaccurate axonal regeneration. Furthermore, such peripheral nerve allografts undergo immunological rejection by the host immune system. In contrast, peripheral nerve injuries repaired by polyethylene glycol fusion of peripheral nerve allografts exhibit excellent behavioral recovery within weeks, reduced immune responses, and many axons do not undergo Wallerian degeneration. The relative contribution of neurorrhaphy and polyethylene glycol-fusion of axons versus the effects of polyethylene glycol per se was unknown prior to this study. We hypothesized that polyethylene glycol might have some immune-protective effects, but polyethylene glycol-fusion was necessary to prevent Wallerian degeneration and functional/behavioral recovery. We examined how polyethylene glycol solutions per se affect functional and behavioral recovery and peripheral nerve allograft morphological and immunological responses in the absence of polyethylene glycol-induced axonal fusion. Ablation-type sciatic nerve injuries in outbred Sprague-Dawley rats were repaired according to a modified protocol using the same solutions as polyethylene glycol-fused peripheral nerve allografts, but peripheral nerve allografts were loose-sutured (loose-sutured polyethylene glycol) with an intentional gap of 1-2 mm to prevent fusion by polyethylene glycol of peripheral nerve allograft axons with host axons. Similar to negative control peripheral nerve allografts not treated by polyethylene glycol and in contrast to polyethylene glycol-fused peripheral nerve allografts, animals with loose-sutured polyethylene glycol peripheral nerve allografts exhibited Wallerian degeneration for all axons and myelin degeneration by 7 days postoperatively and did not recover sciatic-mediated behavioral functions by 42 days postoperatively. Other morphological signs of rejection, such as collapsed Schwann cell basal lamina tubes, were absent in polyethylene glycol-fused peripheral nerve allografts but commonly observed in negative control and loose-sutured polyethylene glycol peripheral nerve allografts at 21 days postoperatively. Loose-sutured polyethylene glycol peripheral nerve allografts had more pro-inflammatory and less anti-inflammatory macrophages than negative control peripheral nerve allografts. While T cell counts were similarly high in loose-sutured-polyethylene glycol and negative control peripheral nerve allografts, loose-sutured polyethylene glycol peripheral nerve allografts expressed some cytokines/chemokines important for T cell activation at much lower levels at 14 days postoperatively. MHCI expression was elevated in loose-sutured polyethylene glycol peripheral nerve allografts, but MHCII expression was modestly lower compared to negative control at 21 days postoperatively. We conclude that, while polyethylene glycol per se reduces some immune responses of peripheral nerve allografts, successful polyethylene glycol-fusion repair of some axons is necessary to prevent Wallerian degeneration of those axons and immune rejection of peripheral nerve allografts, and produce recovery of sensory/motor functions and voluntary behaviors. Translation of polyethylene glycol-fusion technologies would produce a paradigm shift from the current clinical practice of waiting days to months to repair ablation peripheral nerve injuries.
Collapse
Affiliation(s)
- Tyler A Smith
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
| | - Liwen Zhou
- Department of Neuroscience, University of Texas at Austin, Austin, TX, USA
| | | | - Michelle Mikesh
- Department of Neuroscience, University of Texas at Austin, Austin, TX, USA
| | - Cathy Z Yang
- Department of Neuroscience, University of Texas at Austin, Austin, TX, USA
| | - Haley O Tucker
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
| | - JuliAnne Allgood
- Division of Pharmaceutical Sciences, University of Wyoming, Laramie, WY, USA
| | - Jared S Bushman
- Division of Pharmaceutical Sciences, University of Wyoming, Laramie, WY, USA
| | - George D Bittner
- Department of Neuroscience, University of Texas at Austin, Austin, TX, USA
| |
Collapse
|
2
|
Frost C, Salous A, Ketheeswaran S, Ngaage LM, Hanwright PJ, Ghergherehchi C, Tuffaha S, Vaidya D, Bittner GD, Brandacher G, Shores JT. Polyethylene Glycol Fusion Restores Axonal Continuity and Improves Return of Function in a Rat Median Nerve Denervation Model. Plast Reconstr Surg 2024; 154:563-571. [PMID: 37734115 DOI: 10.1097/prs.0000000000011068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/23/2023]
Abstract
BACKGROUND Polyethylene glycol (PEG) can fuse severed closely apposed axolemmas and restore axonal continuity. The authors evaluated the effects of PEG fusion on functional recovery in a rodent forelimb model of peripheral nerve injury. METHODS The median nerves of male Lewis rats ( n = 5 per group) were transected and repaired with standard suture repair (SR), SR with PEG (PEG), or SR with PEG and 1% methylene blue (PEG+MB); a sham surgery group was also included. Proximal stimulation produced compound nerve and muscle action potentials recorded distally. The contralateral limb of each animal acted as an internal control for grip strength measurements. RESULTS Compound nerve and muscle action potentials immediately returned in all PEG and PEG+MB animals, but not in SR animals. The PEG and PEG+MB groups demonstrated earlier return of function by postoperative day (POD) 7 (62.6 ± 7.3% and 50.9 ± 6.7% of contralateral limb grip strength, respectively) compared with the SR group, in which minimal return of function was not measurable until POD 21. At POD 98, the PEG group grip strength recovered to 77.2 ± 2.8% and the PEG+MB grip strength recovered to 79.9 ± 4.4%, compared with 34.9 ± 1.8% recovery in the SR group ( P < 0.05). The PEG and PEG+MB groups reached 50% of the sham group grip strength on POD 3.8 and POD 6.3, respectively, whereas the SR group did not reach 50% grip strength recovery of the sham group throughout the study period. CONCLUSION PEG fusion plus neurorrhaphy with or without MB reestablished axonal continuity, shortened recovery time, and augmented functional recovery compared with suture neurorrhaphy alone. CLINICAL RELEVANCE STATEMENT PEG fusion with neurorrhaphy may bypass Wallerian degeneration, leading to augmented and shortened functional recovery.
Collapse
Affiliation(s)
- Christopher Frost
- From the Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine
| | - Abdel Salous
- From the Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine
| | | | - Ledibabari M Ngaage
- From the Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine
| | - Philip J Hanwright
- From the Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine
| | - Cameron Ghergherehchi
- From the Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine
- Department of Neuroscience, University of Texas at Austin
| | - Sami Tuffaha
- From the Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine
| | - Dhananjay Vaidya
- From the Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine
| | | | - Gerald Brandacher
- From the Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine
| | - Jaimie T Shores
- From the Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine
| |
Collapse
|
3
|
Bittner GD, Tuffaha S, Shores JT. Polyethylene Glycol-Fusion Repair of Peripheral Nerve Injuries. Hand Clin 2024; 40:389-397. [PMID: 38972683 DOI: 10.1016/j.hcl.2024.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/09/2024]
Abstract
Axons successfully repaired with polyethylene glycol (PEG) fusion tecnology restored axonal continuity thereby preventing their Wallerian degeneration and minimizing muscle atrophy. PEG fusion studies in animal models and preliminary clinical trials involving patients with digital nerve repair have shown promise for this therapeutic approach. PEG fusion is safe to perform, and given the enormous potential benefits, there is no reason not to explore its therapeutic potential.
Collapse
Affiliation(s)
- George D Bittner
- Neuroscience Department, Patterson Laboratories, The University of Texas at Austin, Room 321, 2415 Speedway, Austin, TX 78712, USA.
| | - Sami Tuffaha
- Plastic and Reconstructive Surgery, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Jaimie T Shores
- Plastic & Reconstructive Surgery, Johns Hopkins University School of Medicine, 4940 Eastern Avenue, Suite A513, Baltimore, MD 21224, USA
| |
Collapse
|
4
|
Hey G, Willman M, Patel A, Goutnik M, Willman J, Lucke-Wold B. Stem Cell Scaffolds for the Treatment of Spinal Cord Injury-A Review. BIOMECHANICS (BASEL, SWITZERLAND) 2023; 3:322-342. [PMID: 37664542 PMCID: PMC10469078 DOI: 10.3390/biomechanics3030028] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Spinal cord injury (SCI) is a profoundly debilitating yet common central nervous system condition resulting in significant morbidity and mortality rates. Major causes of SCI encompass traumatic incidences such as motor vehicle accidents, falls, and sports injuries. Present treatment strategies for SCI aim to improve and enhance neurologic functionality. The ability for neural stem cells (NSCs) to differentiate into diverse neural and glial cell precursors has stimulated the investigation of stem cell scaffolds as potential therapeutics for SCI. Various scaffolding modalities including composite materials, natural polymers, synthetic polymers, and hydrogels have been explored. However, most trials remain largely in the preclinical stage, emphasizing the need to further develop and refine these treatment strategies before clinical implementation. In this review, we delve into the physiological processes that underpin NSC differentiation, including substrates and signaling pathways required for axonal regrowth post-injury, and provide an overview of current and emerging stem cell scaffolding platforms for SCI.
Collapse
Affiliation(s)
- Grace Hey
- College of Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Matthew Willman
- College of Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Aashay Patel
- College of Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Michael Goutnik
- College of Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Jonathan Willman
- College of Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Brandon Lucke-Wold
- Department of Neurosurgery, University of Florida, Gainesville, FL 32611, USA
| |
Collapse
|
5
|
Liang J, Min LQ, Zhu XY, Ma TT, Li Y, Zhang MQ, Zhao L. Fingolimod protects against neurovascular unit injury in a rat model of focal cerebral ischemia/reperfusion injury. Neural Regen Res 2023; 18:869-874. [DOI: 10.4103/1673-5374.353500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
|
6
|
Stem Cell Strategies in Promoting Neuronal Regeneration after Spinal Cord Injury: A Systematic Review. Int J Mol Sci 2022; 23:ijms232112996. [PMID: 36361786 PMCID: PMC9657320 DOI: 10.3390/ijms232112996] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 10/09/2022] [Accepted: 10/25/2022] [Indexed: 11/25/2022] Open
Abstract
Spinal cord injury (SCI) is a devastating condition with a significant medical and socioeconomic impact. To date, no effective treatment is available that can enable neuronal regeneration and recovery of function at the damaged level. This is thought to be due to scar formation, axonal degeneration and a strong inflammatory response inducing a loss of neurons followed by a cascade of events that leads to further spinal cord damage. Many experimental studies demonstrate the therapeutic effect of stem cells in SCI due to their ability to differentiate into neuronal cells and release neurotrophic factors. Therefore, it appears to be a valid strategy to use in the field of regenerative medicine. This review aims to provide an up-to-date summary of the current research status, challenges, and future directions for stem cell therapy in SCI models, providing an overview of this constantly evolving and promising field.
Collapse
|
7
|
Petrov D, Burrell JC, Browne KD, Laimo FA, Roberts SE, Ali ZS, Cullen DK. Neurorrhaphy in Presence of Polyethylene Glycol Enables Immediate Electrophysiological Conduction in Porcine Model of Facial Nerve Injury. Front Surg 2022; 9:811544. [PMID: 35341161 PMCID: PMC8948462 DOI: 10.3389/fsurg.2022.811544] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 01/24/2022] [Indexed: 01/09/2023] Open
Abstract
Facial nerve trauma often leads to disfiguring facial muscle paralysis. Despite several promising advancements, facial nerve repair procedures often do not lead to complete functional recovery. Development of novel repair strategies requires testing in relevant preclinical models that replicate key clinical features. Several studies have reported that fusogens, such as polyethylene glycol (PEG), can improve functional recovery by enabling immediate reconnection of injured axons; however, these findings have yet to be demonstrated in a large animal model. We first describe a porcine model of facial nerve injury and repair, including the relevant anatomy, surgical approach, and naive nerve morphometry. Next, we report positive findings from a proof-of-concept experiment testing whether a neurorrhaphy performed in conjunction with a PEG solution maintained electrophysiological nerve conduction at an acute time point in a large animal model. The buccal branch of the facial nerve was transected and then immediately repaired by direct anastomosis and PEG application. Immediate electrical conduction was recorded in the PEG-fused nerves (n = 9/9), whereas no signal was obtained in a control cohort lacking calcium chelating agent in one step (n = 0/3) and in the no PEG control group (n = 0/5). Nerve histology revealed putative-fused axons across the repair site, whereas no positive signal was observed in the controls. Rapid electrophysiological recovery following nerve fusion in a highly translatable porcine model of nerve injury supports previous studies suggesting neurorrhaphy supplemented with PEG may be a promising strategy for severe nerve injury. While acute PEG-mediated axon conduction is promising, additional work is necessary to determine if physical axon fusion occurs and the longer-term fate of distal axon segments as related to functional recovery.
Collapse
Affiliation(s)
- Dmitriy Petrov
- Center for Brain Injury and Repair, Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
- Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, United States
| | - Justin C. Burrell
- Center for Brain Injury and Repair, Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
- Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, United States
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA, United States
| | - Kevin D. Browne
- Center for Brain Injury and Repair, Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
- Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, United States
| | - Franco A. Laimo
- Center for Brain Injury and Repair, Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
- Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, United States
| | - Sanford E. Roberts
- Center for Brain Injury and Repair, Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
- Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, United States
| | - Zarina S. Ali
- Center for Brain Injury and Repair, Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - D. Kacy Cullen
- Center for Brain Injury and Repair, Department of Neurosurgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
- Center for Neurotrauma, Neurodegeneration and Restoration, Corporal Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, United States
- Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA, United States
- *Correspondence: D. Kacy Cullen
| |
Collapse
|
8
|
Bittner GD, Bushman JS, Ghergherehchi CL, Roballo KCS, Shores JT, Smith TA. Typical and atypical properties of peripheral nerve allografts enable novel strategies to repair segmental-loss injuries. J Neuroinflammation 2022; 19:60. [PMID: 35227261 PMCID: PMC8886977 DOI: 10.1186/s12974-022-02395-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 01/19/2022] [Indexed: 12/20/2022] Open
Abstract
We review data showing that peripheral nerve injuries (PNIs) that involve the loss of a nerve segment are the most common type of traumatic injury to nervous systems. Segmental-loss PNIs have a poor prognosis compared to other injuries, especially when one or more mixed motor/sensory nerves are involved and are typically the major source of disability associated with extremities that have sustained other injuries. Relatively little progress has been made, since the treatment of segmental loss PNIs with cable autografts that are currently the gold standard for repair has slow and incomplete (often non-existent) functional recovery. Viable peripheral nerve allografts (PNAs) to repair segmental-loss PNIs have not been experimentally or clinically useful due to their immunological rejection, Wallerian degeneration (WD) of anucleate donor graft and distal host axons, and slow regeneration of host axons, leading to delayed re-innervation and producing atrophy or degeneration of distal target tissues. However, two significant advances have recently been made using viable PNAs to repair segmental-loss PNIs: (1) hydrogel release of Treg cells that reduce the immunological response and (2) PEG-fusion of donor PNAs that reduce the immune response, reduce and/or suppress much WD, immediately restore axonal conduction across the donor graft and re-innervate many target tissues, and restore much voluntary behavioral functions within weeks, sometimes to levels approaching that of uninjured nerves. We review the rather sparse cellular/biochemical data for rejection of conventional PNAs and their acceptance following Treg hydrogel and PEG-fusion of PNAs, as well as cellular and systemic data for their acceptance and remarkable behavioral recovery in the absence of tissue matching or immune suppression. We also review typical and atypical characteristics of PNAs compared with other types of tissue or organ allografts, problems and potential solutions for PNA use and storage, clinical implications and commercial availability of PNAs, and future possibilities for PNAs to repair segmental-loss PNIs.
Collapse
Affiliation(s)
- George D Bittner
- Department of Neuroscience, University of Texas at Austin, Austin, TX, 78712, USA.
| | - Jared S Bushman
- School of Pharmacy, University of Wyoming, Laramie, WY, 82072, USA
| | - Cameron L Ghergherehchi
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, 78712, USA
| | | | - Jaimie T Shores
- Department of Plastic and Reconstructive Surgery, Vascularized Composite Allotransplantation Laboratory, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Tyler A Smith
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, 78712, USA
| |
Collapse
|