The histopathological and electrophysiological effects of thymoquinone and methylprednisolone in a rabbit traumatic facial nerve paralysis model

Electrophysiological and histopathological evaluation of the effectiveness of melatonin and glatiramer acetate for traumatic facial nerve injuries

AIM

This study aimed to evaluate the effect of systemic/local use of melatonin and glatiramer acetate on regeneration in traumatic nerve injury models.

MATERIALS AND METHODS

A total of 42 male Wistar albino rats were randomly divided into 6 groups: healthy control (Group 1), injured control (Group 2), local melatonin (Group 3), systemic melatonin (Group 4), local glatiramer acetate (Group 5), and systemic glatiramer acetate (Group 6). In all groups, electromyography recordings of the facial nerve were obtained after surgery and before sacrifice, and the damaged nerve region was histopathologically examined after sacrifice.

RESULTS

In the electrophysiological evaluation, the control group had the greatest decrease in amplitude and extension in latency time following surgery than the treatment groups. Furthermore, a significant decrease in the degenerative axon count, edematous areas, and fibrotic areas as well as a significant increase in axonal surface areas was observed in all the treatment groups compared with the damage control group.

CONCLUSIONS

Although both glatiramer acetate and melatonin are beneficial in regeneration in traumatic facial nerve injuries, it can be concluded that systemic use of melatonin can yield more positive results than glatiramer acetate and local use of both two drugs.

Potential Therapeutic Strategies and Substances for Facial Nerve Regeneration Based on Preclinical Studies

Despite advances in microsurgical technology and an improved understanding of nerve regeneration, obtaining satisfactory results after facial nerve injury remains a difficult clinical problem. Among existing peripheral nerve regeneration studies, relatively few have focused on the facial nerve, particularly how experimental studies of the facial nerve using animal models play an essential role in understanding functional outcomes and how such studies can lead to improved axon regeneration after nerve injury. The purpose of this article is to review current perspectives on strategies for applying potential therapeutic methods for facial nerve regeneration. To this end, we searched Embase, PubMed, and the Cochrane library using keywords, and after applying exclusion criteria, obtained a total of 31 qualifying experimental studies. We then summarize the fundamental experimental studies on facial nerve regeneration, highlighting recent bioengineering studies employing various strategies for supporting facial nerve regeneration, including nerve conduits with stem cells, neurotrophic factors, and/or other therapeutics. Our summary of the methods and results of these previous reports reveal a common feature among studies, showing that various neurotrophic factors arising from injured nerves contribute to a microenvironment that plays an important role in functional recovery. In most cases, histological examinations showed that this microenvironmental influence increased axonal diameter as well as myelination thickness. Such an analysis of available research on facial nerve injury and regeneration represents the first step toward future therapeutic strategies.

Effects of chitosan and platelet-rich plasma on facial nerve regeneration in an animal model

PURPOSE

There is still no widely-accepted local agent proven to be effective in nerve regeneration. We aimed to investigate the effects of chitosan gel and platelet-rich plasma MATERIALS AND METHODS: Electrophysiological measurements were performed before and immediately after injury. The injured nerves were covered with spongostan impregnated with the following agents: Group 1 (Control Group): Saline at a dose of 50 µl; Group 2: Chitosan (CHT) at a dose of 50 µl; Group 3: PRP at a dose of 50 ml; and Group 4: a solution of CHT with PRP (1:1). The final measurements were performed after 3 weeks and the injured nerve of each rat was removed.

RESULTS

There were statistically-significant differences between the groups regarding the measurements of the after-treatment values of stimulus threshold (p < 0.05). The best improvement in electrophysiological measurement and histopathological evaluation was found in Group 4 (CHT-PRP).

CONCLUSION

Chitosan gel has a positive effect on nerve healing and applying it along with PRP can enhance the effect of chitosan.

Safety and feasibility of fat injection therapy with adipose-derived stem cells in a rabbit hypoglossal nerve paralysis model: A pilot study

OBJECTIVE

The aim of this study is to establish a unilateral tongue atrophy model by cutting the hypoglossal nerve and to evaluate the safety and feasibility of a fat injection of adipose-derived stem cells (ADSCs) to restore swallowing function.

METHODS

A total of 12 rabbits were randomized to three groups; the ADSCs+fat group (n=4), the fat group (n=4) and the control group (n=4). All rabbits were treated with denervation of the left hypoglossal nerve and their conditions including body weight and food intake were checked during follow-up periods (8 weeks). At 4 weeks after the transection of the nerve, rabbits received the injection therapy into the denervated side of the tongue with 1.0mL fat tissue premixed with 0.5mL ADSCs in the ADSCs+fat group, 1.0mL fat tissue premixed with 0.5mL PBS in the fat group and 1.5mL PBS in the control group. Rabbits were euthanized 8 weeks post-treatment and resected tongues were collected, formalin-fixed and paraffin embedded. To evaluate the change of the intrinsic muscles of the tongue, muscle fibers around the treatment area was analyzed by evaluating 5 consecutive hematoxylin-eosin slides per rabbit.

RESULTS

Food intake did not decrease upon nerve denervation, and none of the rabbits displayed adverse effect such as aspiration, surgical wound dehiscence or infection. No significant body weight changes were found between the three groups at 4 and 8 weeks after nerve transection (p>0.05). In the control group, the denervated side of tongue had significantly smaller muscle fiber areas and diameters compared to the non-denervated side (p<0.05). The ADSCs+fat group demonstrated a larger area of inferior longitudinal muscle fibers compared to the control and the fat groups (582±312µm² vs. 405±220µm² and 413±226µm²; p<0.05). A significant thicker lesser diameter of inferior longitudinal muscle fibers was found in the ADSCs+fat group compared to the control and the fat groups (24±8µm vs. 20±6µm and 20±7µm; p<0.05).

CONCLUSION

The rabbit tongue atrophy model was found suitable for the assessment of muscle change after nerve transection. Fat injection therapy with ADSCs demonstrated great potential to prevent the muscle atrophy after denervation and to promote the muscle regeneration around the injection area.

Thymoquinone protects DRG neurons from axotomy-induced cell death

OBJECTIVE

Peripheral nerve injury (PNI) is a significant health problem that is linked to sensory, motor, and autonomic deficits. This pathological condition leads to a reduced quality of life in most affected individuals. Schwann cells (SCs) play a crucial role in the repair of PNI. Effective agents that promote SC activation may facilitate and accelerate peripheral nerve repair. Thymoquinone (TQ), a bioactive component of Nigella sativa seeds, has an antioxidant, anti-inflammatory, immunomodulatory, and neuroprotective properties. In the present study, the neuroprotective efficacy of TQ was investigated by using a laser microdissection technique in a mouse PNI model.

METHODS

Single cells were isolated from dorsal root ganglions (DRGs) of 6-8-week-old mice, maintained in defined culture conditions and treated with or without TQ at different concentrations. Axons were cut (axotomy) using a controllable laser microbeam to model axonal injury in vitro. Under fluorescence microscopy, cell viability was evaluated using the fluorescent dyes. The behavior of the cells was continuously monitored with time-lapse video microscopy.

RESULTS

TQ significantly increased neuronal survival by promoting the survival and proliferation of SCs and fibroblasts, as well as the migration of SCs. Furthermore, TQ improved the ability to extend neurites of axotomized neurons. The regenerative effect of TQ was dose-dependent suggesting a target specificity. Our studies warrant further preclinical and clinical investigations of TQ as a potential regenerative agent to treat peripheral nerve injuries.

CONCLUSION

TQ exhibits a regenerative potential for the treatment of damaged peripheral nerves.