The "Gemini" spinal cord fusion protocol: Reloaded

Developing preclinical dog models for reconstructive severed spinal cord continuity via spinal cord fusion technique

Background

Spinal cord injury (SCI) is a severe impairment of the central nervous system, leading to motor, sensory, and autonomic dysfunction. The present study investigates the efficacy of the polyethylene glycol (PEG)-mediated spinal cord fusion (SCF) techniques, demonstrating efficacious in various animal models with complete spinal cord transection at the T10 level. This research focuses on a comparative analysis of three SCF treatment models in beagles: spinal cord transection (SCT), vascular pedicle hemisected spinal cord transplantation (vSCT), and vascularized allograft spinal cord transplantation (vASCT) surgical model.

Methods

Seven female beagles were included in the SCT surgical model, while four female dogs were enrolled in the vSCT surgical model. Additionally, twelve female dogs underwent vASCT in a paired donor-recipient setup. Three surgical model were evaluated and compared through electrophysiology, imaging and behavioral recovery.

Results

The results showed a progressive recovery in the SCT, vSCT and vASCT surgical models, with no statistically significant differences observed in cBBB scores at both 2-month and 6-month post-operation (both P>0.05). Neuroimaging analysis across the SCT, vSCT and vASCT surgical models revealed spinal cord graft survival and fiber regrowth across transection sites at 6 months postoperatively. Also, positive MEP waveforms were recorded in all three surgical models at 6-month post-surgery.

Conclusion

The study underscores the clinical relevance of PEG-mediated SCF techniques in promoting nerve fusion, repair, and motor functional recovery in SCI. SCT, vSCT, and vASCT, tailored to specific clinical characteristics, demonstrated similar effective therapeutic outcomes.

Application of"Spinal cord fusion" in spinal cord injury repair and its neurological mechanism

Spinal cord injury (SCI) is a severely disabling and catastrophic condition that poses significant global clinical challenges. The difficulty of SCI repair results from the distinctive pathophysiological mechanisms, which are characterised by limited regenerative capacity and inadequate neuroplasticity of the spinal cord. Additionally, the formation of cystic cavities and astrocytic scars after SCI further obstructs both the ascending and descending neural conduction pathways. Consequently, the urgent challenge in post-SCI recovery lies in repairing the damaged spinal cord to reconstruct a functional and intact neural conduction circuit. In recent years, significant advancements in biological tissue engineering technology and novel therapies have resulted in a transformative shift in the field of SCI repair. Currently, SCI treatment primarily involves drug therapy, stem cell therapy, the use of biological materials, growth factors, and other approaches. This paper comprehensively reviews the progress in SCI research over the years, with a particular focus on the concept of "Spinal Cord Fusion" as a promising technique for SCI reconstruction. By discussing this important research progress and the neurological mechanisms involved, our aim is to help solve the problem of SCI repair as soon as possible and to bring new breakthroughs in the treatment of paraplegia after SCI.

PEG-chitosan (Neuro-PEG) induced restoration of motor function after complete transection of the dorsal spinal cord in swine. A pilot study

Background

Spinal cord injury (SCI) remains an unmet medical need. Recently, fusogens, such as polyethylene glycol (PEG), have been proven effective in restoring sensorimotor function after complete transection of the spinal cord at different levels and in different species. Here, we report on the use of a PEG-chitosan combo in a different animal model (swine).

Methods

Five Hungarian Mangalica pigs were subjected to complete transection of the thoracic cord (T7-9). Three animals were treated with locally injected PEG-chitosan (Neuro-PEG) gel; two acted as controls. PEG-600 was also injected intra- and post-operatively intravenously. Animals were submitted to rehabilitation, including electrical myostimulation. Results were assessed after 60 days using the Individual Limb Motor Score, the Porcine Thoracic Spinal Cord Injured Behavioral Scale, and the modified motor Basso, Beattie, and Bresnahan scale; sensory and sphincter functions were also assessed. Animals underwent in vivo spinal cord tracing with DiI. Immunofluorescence histology included NF-200, DAPI, and a fluorochrome-conjugated secondary antibody.

Results

Starting on postoperative day (POD) 2, neuro-PEG-treated animals evinced the first signs of recovery, and on POD 60, they could all support their weight and were mobile. Controls never recovered any useful function. Fluorescence microscopy in the experimental group revealed axons passing through the site of injury, while degenerative post-traumatic changes were noted in controls.

Conclusion

Neuro-PEG affords sensorimotor recovery after complete spinal cord transection. This opens the door to human experimentation, including trials of spinal cord transplantation.

Partial restoration of spinal cord neural continuity via vascular pedicle hemisected spinal cord transplantation using spinal cord fusion technique

Aims

Our team tested spinal cord fusion (SCF) using the neuroprotective agent polyethylene glycol (PEG) in different animal (mice, rats, and beagles) models with complete spinal cord transection. To further explore the application of SCF for the treatment of paraplegic patients, we developed a new clinical procedure for SCF called vascular pedicle hemisected spinal cord transplantation (vSCT) and tested this procedure in eight paraplegic participants.

Methods

Eight paraplegic participants (American Spinal Injury Association, ASIA: A) were enrolled and treated with vSCT (PEG was applied to the sites of spinal cord transplantation). Pre‐ and postoperative pain intensities, neurologic assessments, electrophysiologic monitoring, and neuroimaging examinations were recorded.

Results

Of the eight paraplegic participants who completed vSCT, objective improvements occurred in motor function for one participant, in electrophysiologic motor‐evoked potentials for another participant, in re‐establishment of white matter continuity in three participants, in autonomic nerve function in seven participants, and in symptoms of cord central pain for seven participants.

Conclusions

The postoperative recovery of paraplegic participants demonstrated the clinical feasibility and efficacy of vSCT in re‐establishing the continuity of spinal nerve fibers. vSCT could provide the anatomic, morphologic, and histologic foundations to potentially restore the motor, sensory, and autonomic nervous functions in paraplegic patients. More future clinical trials are warranted.

Partial Restoration of Spinal Cord Neural Continuity via Sural Nerve Transplantation Using a Technique of Spinal Cord Fusion

Background

Spinal cord injury (SCI) can cause paralysis and serious chronic morbidity, and there is no effective treatment. Based on our previous experimental results of spinal cord fusion (SCF) in mice, rats, beagles, and monkeys, we developed a surgical protocol of SCF for paraplegic human patients. We designed a novel surgical procedure of SCF, called sural nerve transplantation (SNT), for human patients with lower thoracic SCI and distal cord dysfunction.

Methods

We conducted a clinical trial (ChiCTR2000030788) and performed SNT in 12 fully paraplegic patients due to SCI between T1 and T12. We assessed pre- and postoperative central nerve pain, motor function, sensory function, and autonomic nerve function. Conduction of action potentials across the sural nerve transplant was evaluated. Neural continuity was also examined by diffusion tensor imaging (DTI).

Results

Among the 12 paraplegic patients enrolled in this clinical trial, seven patients demonstrated improved autonomic nerve functions. Seven patients had clinically significant relief of their symptoms of cord central pain. One patient, however, developed postoperative cord central pain (VAS: 4). Five patients had varying degrees of recovered sensory and/or motor functions below the single neurologic level 1 month after surgery. One patient showed recovery of electrophysiologic, motor-evoked potentials 6 months after the operation. At 6 months after surgery, DTI indicated fusion and nerve connections of white cord and sural nerves in seven patients.

Conclusion

SNT was able to fuse the axonal stumps of white cord and sural nerve and at least partially improve the cord central pain in most patients. Although SNT did not restore the spinal cord continuity in white matter in some patients, SNT could restore spinal cord continuity in the cortico-trunco-reticulo-propriospinal pathway, thereby restoring in part some motor and sensory functions. SNT may therefore be a safe, feasible, and effective method to treat paraplegic patients with SCI. Future clinical trials should be performed to optimize the type/technique of nerve transplantation, reduce surgical damage, and minimize postoperative scar formation and adhesion, to avoid postoperative cord central pain.

Clinical Trial Registration

[http://www.chictr.org.cn/showproj.aspx?proj=50526], identifier [ChiCTR2000030788].

Transplantation of a vascularized pedicle of hemisected spinal cord to establish spinal cord continuity after removal of a segment of the thoracic spinal cord: A proof-of-principle study in dogs

Introduction

Glial scar formation impedes nerve regeneration/reinnervation after spinal cord injury (SCI); therefore, removal of scar tissue is essential for SCI treatment.

Aims

To investigate whether removing a spinal cord and transplanting a vascularized pedicle of hemisected spinal cord from the spinal cord caudal to the transection can restore motor function, to aid in the treatment of future clinical spinal cord injuries. We developed a canine model. After removal of a 1‐cm segment of the thoracic (T10–T11) spinal cord in eight beagles, a vascularized pedicle of hemisected spinal cord from the first 1.5 cm of the spinal cord caudal to the transection (cut along the posterior median sulcus of the spinal cord) was transplanted to bridge the transected spinal cord in the presence of a fusogen (polyethylene glycol, PEG) in four of the eight dogs. We used various forms of imaging, electron microscopy, and histologic data to determine that after our transplantation of a vascular pedicled hemisection to bridge the transected spinal cord, electrical continuity across the spinal bridge was restored.

Results

Motor function was restored following our transplantation, as confirmed by the re‐establishment of anatomic continuity along with interfacial axonal sprouting.

Conclusion

Taken together, our findings suggest that SCI patients—who have previously been thought to have irreversible damage and/or paralysis—may be treated effectively with similar operative techniques to re‐establish electrical and functional continuity following SCI.

Bridging the gap: Spinal cord fusion as a treatment of chronic spinal cord injury

Despite decades of animal experimentation, human translation with cell grafts, conduits, and other strategies has failed to cure patients with chronic spinal cord injury (SCI). Recent data show that motor deficits due to spinal cord transection in animal models can be reversed by local application of fusogens, such as Polyethylene glycol (PEG). Results proved superior at short term over all other treatments deployed in animal studies, opening the way to human trials. In particular, removal of the injured spinal cord segment followed by PEG fusion of the two ends along with vertebral osteotomy to shorten the spine holds the promise for a cure in many cases.

From Hypothermia to Cephalosomatic Anastomoses: The Legacy of Robert White (1926-2010) at Case Western Reserve University of Cleveland

Dr. Robert J. White (1926-2010) was an eminent neurosurgeon and bioethicist, renowned for his classic work in hypothermia and pioneering mammalian head transplant experiments. He founded the Division of Neurosurgery at the Cleveland Metropolitan General Hospital (currently MetroHealth Medical Center, a level 1 trauma county hospital) and became the youngest full professor at the Case Western Reserve University in Cleveland, Ohio. With over 500 research articles to his credit, he founded the Brain Research Laboratory at what was then the Cleveland Metropolitan General Hospital, which was also home to future leaders in neurosurgery, neurosciences, and allied specialties. He transferred a healthy monkey head onto a surgically beheaded monkey body under deep hypothermic conditions drawing both laurels and criticisms alike. Despite a largely controversial neurosurgical research career, his original contributions to deep hypothermia have found profound clinical applications in modern trauma and vascular neurosurgery. The new fusogens and myelorrhaphy methods being tried in Europe hold promise for a future of reanastomosing 2 homologous or heterologous tracts in the neuraxis.

Effect of Graphene Nanoribbons (TexasPEG) on locomotor function recovery in a rat model of lumbar spinal cord transection

A sharply transected spinal cord has been shown to be fused under the accelerating influence of membrane fusogens such as polyethylene glycol (PEG) (GEMINI protocol). Previous work provided evidence that this is in fact possible. Other fusogens might improve current results. In this study, we aimed to assess the effects of PEGylated graphene nanoribons (PEG-GNR, and called “TexasPEG” when prepared as 1wt% dispersion in PEG600) versus placebo (saline) on locomotor function recovery and cellular level in a rat model of spinal cord transection at lumbar segment 1 (L₁) level. In vivo and in vitro experiments (n = 10 per experiment) were designed. In the in vivo experiment, all rats were submitted to full spinal cord transection at L₁ level. Five weeks later, behavioral assessment was performed using the Basso Beattie Bresnahan (BBB) locomotor rating scale. Immunohistochemical staining with neuron marker neurofilament 200 (NF200) antibody and astrocytic scar marker glial fibrillary acidic protein (GFAP) was also performed in the injured spinal cord. In the in vitro experiment, the effects of TexasPEG application for 72 hours on the neurite outgrowth of SH-SY5Y cells were observed under the inverted microscope. Results of both in vivo and in vitro experiments suggest that TexasPEG reduces the formation of glial scars, promotes the regeneration of neurites, and thereby contributes to the recovery of locomotor function of a rat model of spinal cord transfection.

Restoration of motor function after operative reconstruction of the acutely transected spinal cord in the canine model

BACKGROUND

Cephalosomatic anastomosis or what has been called a "head transplantation" requires full reconnection of the respective transected ends of the spinal cords. The GEMINI spinal cord fusion protocol has been developed for this reason. Here, we report the first randomized, controlled study of the GEMINI protocol in large animals.

METHODS

We conducted a randomized, controlled study of a complete transection of the spinal cord at the level of T10 in dogs at Harbin Medical University, Harbin, China. These dogs were followed for up to 8 weeks postoperatively by assessments of recovery of motor function, somato-sensory evoked potentials, and diffusion tensor imaging using magnetic resonance imaging.

RESULTS

A total of 12 dogs were subjected to operative exposure of the dorsal aspect of the spinal cord after laminectomy and longitudinal durotomy followed by a very sharp, controlled, full-thickness, complete transection of the spinal cord at T10. The fusogen, polyethylene glycol, was applied topically to the site of the spinal cord transection in 7 of 12 dogs; 0.9% NaCl saline was applied to the site of transection in the remaining 5 control dogs. Dogs were selected randomly to receive polyethylene glycol or saline. All polyethylene glycol-treated dogs reacquired a substantial amount of motor function versus none in controls over these first 2 months as assessed on the 20-point (0-19), canine, Basso-Beattie-Bresnahan rating scale (P<.006). Somatosensory evoked potentials confirmed restoration of electrical conduction cranially across the site of spinal cord transection which improved over time. Diffusion tensor imaging, a magnetic resonance permutation that assesses the integrity of nerve fibers and cells, showed restitution of the transected spinal cord with polyethylene glycol treatment (at-injury level difference: P<.02).

CONCLUSION

A sharply and fully transected spinal cord at the level of T10 can be reconstructed with restoration of many aspects of electrical continuity in large animals following the GEMINI spinal cord fusion protocol, with objective evidence of motor recovery and of electrical continuity across the site of transection, opening the way to the first cephalosomatic anastomosis. (Surgery 2017;160:XXX-XXX.).

Polyethylene glycol-induced motor recovery after total spinal transection in rats

AIMS

Despite more than a century of research, spinal paralysis remains untreatable via biological means. A new understanding of spinal cord physiology and the introduction of membrane fusogens have provided new hope that a biological cure may soon become available. However, proof is needed from adequately powered animal studies.

METHODS AND RESULTS

Two groups of rats (n=9, study group, n=6 controls) were submitted to complete transection of the dorsal cord at T10. The animals were randomized to receive either saline or polyethylene glycol (PEG) in situ. After 4 weeks, the treated group had recovered ambulation vs none in the control group (BBB scores; P=.0145). One control died. All animals were studied with somatosensory-evoked potentials (SSEP) and diffusion tensor imaging (DTI). SSEP recovered postoperatively only in PEG-treated rats. At study end, DTI showed disappearance of the transection gap in the treated animals vs an enduring gap in controls (fractional anisotropy/FA at level: P=.0008).

CONCLUSIONS

We show for the first time in an adequately powered study that the paralysis attendant to a complete transection of the spinal cord can be reversed. This opens the path to a severance-reapposition cure of spinal paralysis, in which the injured segment is excised and the two stumps approximated after vertebrectomy/diskectomies.

Physical and electrical characterization of TexasPEG: An electrically conductive neuronal scaffold

BACKGROUND

Graphene and its derivatives have been shown to be biocompatible and electrically active materials upon which neurons readily grow. The fusogen poly(ethylene glycol) (PEG) has been shown to improve outcomes after cervical and dorsal spinal cord transection. The long and narrow PEGylated graphene nanoribbon stacks (PEG-GNRs) with their 5 μm × 200 nm × 10 nm dimensions can provide a scaffold upon which neurons can grow and fuse. We disclose here the extensive characterization data for the PEG-GNRs.

METHODS

PEG-GNRs were chemically synthesized and chemically and electrically characterized.

RESULTS

The average aspect ratio of the PEG-GNRs was determined to be ~85, which corresponds to a critical percolation value (the point where insulating material becomes conductive by addition of conductive particles) of 1%. However, there was not a sharp increase in AC conductivity at frequencies relevant to action potentials.

CONCLUSION

A robust characterization of PEG-GNRs is discussed, though the precise origin of efficacy in improving outcomes following spinal cord transection is not known.

HEAVEN: The Frankenstein effect

The HEAVEN head transplant initiative needs human data concerning the acute restoration of motor transmission after application of fusogens to the severed cord in man. Data from two centuries ago prove that a fresh cadaver, after hanging or decapitation, can be mobilized by electrical stimulation for up to 3 hours. By administering spinal cord stimulation by applied paddles to the cord or transcranial magnetic stimulation to M1 and recording motor evoked potentials, it should be possible to test fusogens in fresh cadavers. Delayed neuronal death might be the neuropathological reason.

Spinal cord fusion with PEG-GNRs (TexasPEG): Neurophysiological recovery in 24 hours in rats

BACKGROUND

The GEMINI spinal cord fusion protocol has been developed to achieve a successful cephalosomatic anastomosis. Here, for the first time, we report the effects of locally applied water-soluble, conductive PEG(polyethylene glycol)ylated graphene nanoribbons (PEG-GNRs) on neurophysiologic conduction after sharp cervical cord transection in rats. PEG-GNRs were produced by the polymerization of ethylene oxide from anion-edged graphene nanoribbons. These combine the fusogenic potential of PEG with the electrical conducting properties of the graphene nanoribbons.

METHODS

Laminectomy and transection of cervical spinal cord (C5) was performed on Female Sprague-Dawley (SD) rats. After applying PEG-GNR on the severed part, electrophysiological recovery of the reconstructed cervical spinal cord was confirmed by somatosensory evoked potentials (SSEPs) at 24 h after surgery.

RESULTS

While no SSEPs were detected in the control group, PEG-GNR treated group showed fast recovery of SSEPs at 24 h after the surgery.

CONCLUSION

In this preliminary dataset, for the first time, we report the effect of a novel form of PEG with the goal of rapid reconstruction of a sharply severed spinal cord.

Neurologic foundations of spinal cord fusion (GEMINI)

Cephalosomatic anastomosis has been carried out in both monkeys and mice with preservation of brain function. Nonetheless the spinal cord was not reconstructed, leaving the animals unable to move voluntarily. Here we review the details of the GEMINI spinal cord fusion protocol, which aims at restoring electrophysiologic conduction across an acutely transected spinal cord. The existence of the cortico-truncoreticulo-propriospinal pathway, a little-known anatomic entity, is described, and its importance concerning spinal cord fusion emphasized. The use of fusogens and electrical stimulation as adjuvants for nerve fusion is addressed. The possibility of achieving cephalosomatic anastomosis in humans has become reality in principle.

Fusogen-assisted rapid reconstitution of anatomophysiologic continuity of the transected spinal cord

The GEMINI spinal cord fusion protocol exploits the ability of so-called fusogens, such as polyethylene glycol (PEG), to achieve rapid neural restoration of electrical continuity across the ends of a transected spinal cord. Experimental evidence suggests that motor recovery can occur after complete transection of the cervical and dorsal spinal cord in mice and rats following application of PEG. This allows for the possibility of spinal cord "reconstruction" in humans and even the possibility of head transplantation in the future.

Central Pain Following Cord Severance for Cephalosomatic Anastomosis

One of the key obstacles to a successful head transplant is the possible onset of central pain, a chronic pain condition that would impair the quality of life of the transplantee. In this review, we provide the reader with a knowledge of this neglected aspect of the head transplant initiative and outline the management should this eventuality occur.

Head Transplantation in Mouse Model

AIMS

The mouse model of allo-head and body reconstruction (AHBR) has recently been established to further the clinical development of this strategy for patients who are suffering from mortal bodily trauma or disease, yet whose mind remains healthy. Animal model studies are indispensable for developing such novel surgical practices. The goal of this work was to establish head transplant mouse model, then the next step through the feasible biological model to investigate immune rejection and brain function in next step, thereby promoting the goal of translation of AHBR to the clinic in the future.

METHODS AND RESULTS

Our approach involves retaining adequate blood perfusion in the transplanted head throughout the surgical procedure by establishing donor-to-recipient cross-circulation by cannulating and anastomosing the carotid artery on one side of the body and the jugular vein on the other side. Neurological function was preserved by this strategy as indicated by electroencephalogram and intact cranial nerve reflexes.

CONCLUSIONS

The results of this study support the feasibility of this method for avoiding brain ischemia during transplantation, thereby allowing for the possibility of long-term studies of head transplantation.