End-to-side neurorrhaphy for nerve repair and function rehabilitation

Fast Blue and Cholera Toxin-B Survival Guide for Alpha-Motoneurons Labeling: Less Is Better in Young B6SJL Mice, but More Is Better in Aged C57Bl/J Mice

Fast Blue (FB) and Cholera Toxin-B (CTB) are two retrograde tracers extensively used to label alpha-motoneurons (α-MNs). The overall goals of the present study were to (1) assess the effectiveness of different FB and CTB protocols in labeling α-MNs, (2) compare the labeling quality of these tracers at standard concentrations reported in the literature (FB 2% and CTB 0.1%) versus lower concentrations to overcome tracer leakage, and (3) determine an optimal protocol for labeling α-MNs in young B6SJL and aged C57Bl/J mice (when axonal transport is disrupted by aging). Hindlimb muscles of young B6SJL and aged C57Bl/J mice were intramuscularly injected with different FB or CTB concentrations and then euthanized at either 3 or 5 days after injection. Measurements were performed to assess labeling quality via seven different parameters. Our results show that tracer protocols of lower concentration and shorter labeling durations were generally better in labeling young α-MNs, whereas tracer protocols of higher tracer concentration and longer labeling durations were generally better in labeling aged α-MNs. A 0.2%, 3-day FB protocol provided optimal labeling of young α-MNs without tracer leakage, whereas a 2%, 5-day FB protocol or 0.1% CTB protocol provided optimal labeling of aged α-MNs. These results inform future studies on the selection of optimal FB and CTB protocols for α-MNs labeling in normal, aging, and neurodegenerative disease conditions.

The TGF-β1 pathway is early involved in neurogenic bladder fibrosis of juvenile rats

BACKGROUND

This study investigated whole neurogenic bladder's progression changes, as well as the expression of TGF-β1 fibrosis pathway-related proteins in bilateral spinal nerve-amputated juvenile rats.

METHODS

Sixty-four 8-week-old rats (32 bilateral L6 + S1 spinal nerve amputated and 32 sham operated) were selected. Cystometry was performed. General assessments, Masson, Sirius red, immunohistochemical staining, and western blotting of fibrosis and TGF-β1 pathway-related proteins were conducted using bladder tissues.

RESULTS

Cystometry results showed that the basal intravesical pressures and bladder capacities in nerve-amputated rats were significantly higher than those in sham-operated ones. Compared to the sham-operated groups, the bladder size and wall thickness in the nerve-amputated groups increased initially but then decreased over time. However, bladder weight continuously increased over time. Disintegration, thickening, and hypertrophy of the bladder wall were found over time in the amputated rats. Moreover, there was a significant increase in collagen III, and the ratio of collagen III/I was higher in amputated rats (P < 0.01). Finally, the expression of TGF-β1, TGF-βRI, Smad2, and collagen III and I increased in amputated bladder tissues, while Smad6 decreased over time.

CONCLUSIONS

The main clinical features of pediatric neurogenic bladder (PNB) were detrusor paralysis and continuous intravesical pressure. Biological molecular findings are earlier than the pathophysiological findings. Therefore, early preventing bladder fibrosis by targeting TGF-β1/Smad pathway-related proteins once knowing the PNB diagnosis might be an alternative treatment for PNB.

IMPACT

The study found that the main clinical features of PNB were detrusor paralysis, continuous intravesical pressure, and increased TGF-beta/Smad signal proteins over time. The study makes contributions to the literature because it suggests biological molecular findings are earlier than the pathophysiological findings by various staining in PNB. The study investigated whole neurogenic bladder's progression changes, as well as the expression of TGF-β1 fibrosis pathway-related proteins in the spinal nerve-injured PNB juvenile rat models, which suggests that early prevention of bladder fibrosis by targeting TGF-β1/Smad pathway-related proteins once knowing the PNB diagnosis might be an alternative treatment for pediatric neurogenic bladder.

The Neurotrophic Effects and Mechanism of Action for FK1706 in Neurorrhaphy Rat Models and SH-SY5Y Cells

FK1706 is a novel non-immunosuppressive immunophilin ligand with neurotrophic activity and exerts its neurotrophic effect through NGF. The present study aimed to elaborate on the neurotrophic activity and the mechanism of action of FK1706 in end-to-side neurorrhaphy rats and SH-SY5Y cells. In the regenerating nerves of neurorrhaphy rats, FK1706 increased the thickness of myelin sheath and the level of nerve regeneration-related proteins. The mechanism of action of FK1706 on neurite regrowth was elucidated in vitro by incubating SH-SY5Y cells in different conditions (Control, NGF, FK1706, NGF + FK1706, NGF + FK1706 + geldanamycin). Under the conditions where NGF was used, the phosphorylation level of major proteins (Raf-1 and ERK) in the Ras/Raf/MAPK/ERK signaling pathway related to SH-SY5Y cell proliferation was significantly enhanced following the application of FK1706. The number of viable cells, cell viability and neurite length of SH-SY5Y cells was maximal when NGF and FK1706 were used simultaneously. The binding level of HSP90 and Raf-1 in FK1706 group was the highest. These results indicated that FK1706 could significantly promote nerve regeneration after neurorrhaphy. The putative mechanism of action stated that FK1706 could promote the binding of HSP90 and Raf-1, make Raf-1 continue to be activated, thereby affecting key proteins in the Ras/Raf/MAPK/ERK signaling pathway related to the neurotrophic effects of NGF to promote the proliferation and neurite regrowth of nerve cells.

Corneal neurotization for neurotrophic keratopathy: Review of surgical techniques and outcomes

Neurotrophic keratopathy is a degenerative disease in which damage to the corneal nerves leads to corneal hypoesthesia. Injuries to neurotrophic corneas are notoriously difficult to treat and have traditionally been approached with supportive management. However, recent progress in the field of corneal neurotization has given new direction for addressing nerve loss directly by stimulating new nerve growth onto the cornea from nearby sensory nerves transferred to the perilimbal region. Herein, we review the surgical techniques utilized in corneal neurotization, including direct transfers and the use of nerve grafts. Considerations in surgical approach, as well as factors that influence prognosis and outcomes of the surgical intervention are also discussed.

Electromyography as an intraoperative test to assess the quality of nerve anastomosis - experimental study on rats

Background

Many factors contribute to successful nerve reconstruction. The correct technique of anastomosis is one of the key elements that determine the final result of a surgery. The aim of this study is to examine how useful an electromyography (EMG) can be as an objective intraoperative anastomosis assessment method.

Methods

The study material included 12 rats. Before the surgery, the function of the sciatic nerve was tested using hind paw prints. Then, both nerves were cut. The left nerve was sutured side-to-side, and the right nerve was sutured end-to-end. Intraoperative electromyography was performed. After 4 weeks, the rats were reassessed using the hind paw print analysis and electromyography.

Results

An analysis of left and right hind paw prints did not reveal any significant differences between the length of the steps, the spread of the digits in the paws, or the deviation of a paw. The width of the steps also did not change.Electromyography revealed that immediately after a nerve anastomosis (as well as 4 weeks after the surgery), better nerve conduction was observed through an end-to-end anastomosis. Four weeks after the surgery, better nerve conduction was seen distally to the end-to-end anastomosis.

Conclusions

The results indicate that in acute nerve injuries intraoperative electromyography may be useful to obtain unbiased information on whether the nerve anastomosis has been performed correctly - for example, in limb replantation.When assessing a nerve during a procedure, EMG should be first performed distally to the anastomosis (the part of the nerve leading to muscle fibers) and then proximally to the anastomosis (the proximal part of the nerve). Similar EMG results can be interpreted as a correct nerve anastomosis.The function of the distal part of the nerve and the muscle remains intact if the neuromuscular transmission is sustained.

Prevention of denervated muscle atrophy with accelerated nerve-regeneration by babysitter procedure in rat facial nerve paralysis model

PURPOSE

The "babysitter" procedure is a reconstruction technique for facial nerve complete paralysis and uses the movement source from the healthy facial nerve with a cross-nerve graft. First, an end-to-side neurorrhaphy is performed between the affected facial nerve trunk and hypoglossal nerve for continuously delivering stimuli to the mimetic muscles for preventing the atrophy of mimetic muscles. Despite favorable clinical results, histological and physiological mechanisms remain unknown. This study attempted to establish a model for the "babysitter" procedure and find its efficacy in rats with facial nerve complete paralysis.

MATERIALS AND METHODS

A total of 16 Lewis rats were used and divided into 2 groups; cross nerve graft (n = 8) and babysitter groups (n = 8). The facial nerve trunk was transected in both groups. Babysitter group underwent a two-stage procedure. Cross nerve graft group underwent only the transfer of nerve graft from the healthy side to affected side. The animals were assessed physiologically by compound muscle action potential (CMAP), and the regenerated nerve tissues were evaluated histopathologically at 13 weeks after surgery.

RESULTS

Facial nucleus stained with retrograde tracers proved the re-innervation of affected facial muscle by the babysitter procedure. In CMAP, the amplitude of babysitter group was significantly higher than that of the cross-facial nerve graft group (p < .05). Histological examination found a significant difference in myelin g-ratio between two groups (p < .05).

CONCLUSION

This study investigated the "babysitter" procedure for rat facial nerve palsy. Babysitter procedure shortened the denervation period without mimic muscle atrophy.

The effects of FK1706 on nerve regeneration and bladder function recovery following an end-to-side neurorrhaphy in rats

BACKGROUND

Immunophilin ligands are neuroregenerative agents binding to FK506 binding proteins, by which stimulate recovery of neurons in a variety of injury nerves. FK1706 is a novel immunophilin ligand which has neuroprotective and neuroregenerative effects but without immunosuppressive activity. At present, most reports about FK1706 in ameliorating nerve injury and functional recovery are limited to cavernous nerve injury and erectile function recovery. This study aimed to demonstrate the effects of FK1706 on nerve regeneration and bladder function recovery following an end-to-side neurorrhaphy in rat models.

METHOD

The numbers of regenerated myelinated axons of the pelvic parasympathetic nerve (PPN) in the three groups' rats (FK1706 + ETS, ETS and control groups) were evaluated. Their intravesical pressure (IVP), S100β and growth associated protein 43 (GAP43) expressions were also compared.

RESULTS

In FK1706 + ETS group, 90% the rats showed that the frequency of FG labeled neurons was larger than the 3.5 cutoff value, 100% the rats showed that the frequency of FG-FB double-labeled neurons was larger than the 5.5 cutoff value. The average maximum of IVP in FK1706 + ETS group reached 76.3% of the value in control group. Their average number of myelinated axons of regenerated PPN reached 80% of the amount in control group. The nerve regeneration-associated markers data indicated that the expression level of S100β and GAP43 in FK1706 + ETS group was approximately 2-fold higher than that of ETS group (P < 0.05).

CONCLUSIONS

After end-to-side neurorrhaphy, FK1706 effectively enhanced the nerve regeneration and bladder function recovery.

End-to-side neurorrhaphy repairs peripheral nerve injury: sensory nerve induces motor nerve regeneration

End-to-side neurorrhaphy is an option in the treatment of the long segment defects of a nerve. It involves suturing the distal stump of the disconnected nerve (recipient nerve) to the side of the intimate adjacent nerve (donor nerve). However, the motor-sensory specificity after end-to-side neurorrhaphy remains unclear. This study sought to evaluate whether cutaneous sensory nerve regeneration induces motor nerves after end-to-side neurorrhaphy. Thirty rats were randomized into three groups: (1) end-to-side neurorrhaphy using the ulnar nerve (mixed sensory and motor) as the donor nerve and the cutaneous antebrachii medialis nerve as the recipient nerve; (2) the sham group: ulnar nerve and cutaneous antebrachii medialis nerve were just exposed; and (3) the transected nerve group: cutaneous antebrachii medialis nerve was transected and the stumps were turned over and tied. At 5 months, acetylcholinesterase staining results showed that 34% ± 16% of the myelinated axons were stained in the end-to-side group, and none of the myelinated axons were stained in either the sham or transected nerve groups. Retrograde fluorescent tracing of spinal motor neurons and dorsal root ganglion showed the proportion of motor neurons from the cutaneous antebrachii medialis nerve of the end-to-side group was 21% ± 5%. In contrast, no motor neurons from the cutaneous antebrachii medialis nerve of the sham group and transected nerve group were found in the spinal cord segment. These results confirmed that motor neuron regeneration occurred after cutaneous nerve end-to-side neurorrhaphy.

Effect of Collateral Sprouting on Donor Nerve Function After Nerve Coaptation: A Study of the Brachial Plexus

Background

The aim of the present study was to evaluate the donor nerve from the C7 spinal nerve of the rabbit brachial plexus after a coaptation procedure. Assessment was performed of avulsion of the C5 and C6 spinal nerves treated by coaptation of these nerves to the C7 spinal nerve.

Material/Methods

After nerve injury, fourteen rabbits were treated by end-to-side coaptation (ETS), and fourteen animals were treated by side-to-side coaptation (STS) on the right brachial plexus. Electrophysiological and histomorphometric analyses and the skin pinch test were used to evaluate the outcomes.

Results

There was no statistically significant difference in the G-ratio proximal and distal to the coaptation in the ETS group, but the differences in the axon, myelin sheath and fiber diameters were statistically significant. The comparison of the ETS and STS groups distal to the coaptation with the controls demonstrated statistically significant differences in the fiber, axon, and myelin sheath diameters. With respect to the G-ratio, the ETS group exhibited no significant differences relative to the control, whereas the G-ratio in the STS group and the controls differed significantly. In the electrophysiological study, the ETS and STS groups exhibited major changes in the biceps and subscapularis muscles.

Conclusions

The coaptation procedure affects the histological structure of the nerve donor, but it does not translate into changes in nerve conduction or the sensory function of the limb. The donor nerve lesion in the ETS group is transient and has minimal clinical relevance.