Polyethylene glycol fusion associated with antioxidants: A new promise in the treatment of traumatic facial paralysis

Research status of facial nerve repair

The facial nerve, also known as the seventh cranial nerve, is critical in controlling the movement of the facial muscles. It is responsible for all facial expressions, such as smiling, frowning, and moving the eyebrows. However, damage to this nerve can occur for a variety of reasons, including maxillofacial surgery, trauma, tumors, and infections. Facial nerve injuries can cause severe functional impairment and can lead to different degrees of facial paralysis, significantly affecting the quality of life of patients. Over the past ten years, significant progress has been made in the field of facial nerve repair. Different approaches, including direct suture, autologous nerve grafts, and tissue engineering, have been utilized for the repair of facial nerve injury. This article mainly summarizes the clinical methods and basic research progress of facial nerve repair in the past ten years.

Polyethylene Glycol Fusion of Nerve Injuries: Review of the Technique and Clinical Applicability

Traumatic peripheral nerve injuries present a particular challenge to hand surgeons as mechanisms of nerve-healing pose serious limitations to achieving complete functional recovery. The loss of distal axonal segments through Wallerian degeneration results in the loss of neuromuscular junctions and irreversible muscle atrophy. Current methods of repair depend on the outgrowth of proximal nerve fibers following direct end-to-end repair or gap repair techniques. Investigational techniques in nerve repair using polyethylene glycol (PEG) nerve fusion have been shown to bypass Wallerian degeneration by immediately restoring nerve axonal continuity, thus resulting in a rapid and more complete functional recovery. The purpose of this article is to review the current literature surrounding this novel technique for traumatic nerve repair, paying particular attention to the underlying physiology of nerve healing and the current applications of PEG fusion in the laboratory and clinical setting. This article also serves to identify areas of future investigation to further establish validity and feasibility and encourage the translation of PEG fusion into clinical use.

Polyethylene glycol-fusion repair of sciatic allografts in female rats achieves immunotolerance via attenuated innate and adaptive responses

Ablation/segmental loss peripheral nerve injuries (PNIs) exhibit poor functional recovery due to slow and inaccurate outgrowth of regenerating axons. Viable peripheral nerve allografts (PNAs) as growth-guide conduits are immunologically rejected and all anucleated donor/host axonal segments undergo Wallerian degeneration. In contrast, we report that ablation-type sciatic PNIs repaired by neurorrhaphy of viable sciatic PNAs and a polyethylene glycol (PEG)-fusion protocol using PEG immediately restored axonal continuity for many axons, reinnervated/maintained their neuromuscular junctions, and prevented much Wallerian degeneration. PEG-fused PNAs permanently restored many sciatic-mediated behaviors within 2-6 weeks. PEG-fused PNAs were not rejected even though host/donors were neither immunosuppressed nor tissue-matched in outbred female Sprague Dawley rats. Innate and adaptive immune responses to PEG-fused sciatic PNAs were analyzed using electron microscopy, immunohistochemistry, and quantitative reverse transcription polymerase chain reaction for morphological features, T cell and macrophage infiltration, major histocompatibility complex (MHC) expression, apoptosis, expression of cytokines, chemokines, and cytotoxic effectors. PEG-fused PNAs exhibited attenuated innate and adaptive immune responses by 14-21 days postoperatively, as evidenced by (a) many axons and cells remaining viable, (b) significantly reduced infiltration of cytotoxic and total T cells and macrophages, (c) significantly reduced expression of inflammatory cytokines, chemokines, and MHC proteins, (d) consistently low apoptotic response. Morphologically and/or biochemically, PEG-fused sciatic PNAs often resembled sciatic autografts or intact sciatic nerves. In brief, PEG-fused PNAs are an unstudied, perhaps unique, example of immune tolerance of viable allograft tissue in a nonimmune-privileged environment and could greatly improve the clinical outcomes for PNIs relative to current protocols.

Facial nerve repair utilizing intraoperative repair strategies

OBJECTIVES

To determine whether functional and anatomical outcomes following suture neurorrhaphy are improved by the addition of electrical stimulation with or without the addition of polyethylene glycol (PEG).

METHODS

In a rat model of facial nerve injury, complete facial nerve transection and repair was performed via (a) suture neurorrhaphy alone, (b) neurorrhaphy with the addition of brief (30 minutes) intraoperative electrical stimulation, or (c) neurorrhaphy with the addition electrical stimulation and PEG. Functional recovery was assessed weekly for 16 weeks. At 16 weeks postoperatively, motoneuron survival, amount of regrowth, and specificity of regrowth were assessed by branch labeling and tissue analysis.

RESULTS

The addition of brief intraoperative electrical stimulation improved all functional outcomes compared to suturing alone. The addition of PEG to electrical stimulation impaired this benefit. Motoneuron survival, amount of regrowth, and specificity of regrowth were unaltered at 16 weeks postoperative in all treatment groups.

CONCLUSION

The addition of brief intraoperative electrical stimulation to neurorrhaphy in this rodent model shows promising neurological benefit in the surgical repair of facial nerve injury.

LEVEL OF EVIDENCE

Animal study.

Peg-Enhanced Behavioral Recovery After Sciatic Nerve Transection and Either Suturing Or Sleeve Conduit Deployment in Rats

Polyethylene glycol (PEG) has previously been reported to improve outcomes of peripheral nerve microsuturing. However, recent studies have challenged this finding. Given its clinical importance, we investigated the potential of PEG as a facilitator of peripheral nerve restoration. The sciatic nerve of 144 rats was transected and submitted either to simple suturing (Group A), PEG-enhanced suturing (Group B), and insertion in an arterial sleeve conduit without PEG (Group C), or with PEG (Group D) in equal numbers. Behavioral recovery was assessed with the sciatic function index (SFI). Nerve impulse conduction was assessed with compound muscle action potentials (CMAPs). Histology comprised standard hematoxylin/eosin staining, electron microscopy and glial cell line-derived neurotrophic factor (GDNF) immunohistochemistry. Expression of GDNF was also assessed with western blotting. Results were evaluated at weeks 1, 4, and 8. PEG treatment significantly improved behavioral recovery and morphology of nerve restoration, particularly in the sleeve conduit group, relative to that of controls. In conclusion, PEG may improve outcomes of peripheral nerve reconstruction.

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.

Polyethylene Glycol: The Future of Posttraumatic Nerve Repair? Systemic Review

Peripheral nerve injury is a common posttraumatic complication. The precise surgical repair of nerve lesion does not always guarantee satisfactory motor and sensory function recovery. Therefore, enhancement of the regeneration process is a subject of many research strategies. It is believed that polyethylene glycol (PEG) mediates axolemmal fusion, thus enabling the direct restoration of axon continuity. It also inhibits Wallerian degeneration and recovers nerve conduction. This systemic review, performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, describes and summarizes published studies on PEG treatment efficiency in various nerve injury types and repair techniques. Sixteen original experimental studies in animal models and one in humans were analyzed. PEG treatment superiority was reported in almost all experiments (based on favorable electrophysiological, histological, or behavioral results). To date, only one study attempted to transfer the procedure into the clinical phase. However, some technical aspects, e.g., the maximal delay between trauma and successful treatment, await determination. PEG therapy is a promising prospect that may improve the surgical treatment of peripheral nerve injuries in the clinical practice.