Surgical Procedure for Transplanting Artificial Nerve Conduits for Peripheral Nerve Regeneration:

Corrigendum to "Dedifferentiated fat cells in polyglycolic acid-collagen nerve conduits promote rat facial nerve regeneration" [Regen Ther 11 (2019) 240-248]

[This corrects the article DOI: 10.1016/j.reth.2019.08.004.].

Dedifferentiated fat cells in polyglycolic acid-collagen nerve conduits promote rat facial nerve regeneration

Introduction

Polyglycolic acid (PGA) nerve conduits, an artificial biodegradable nerve regeneration-inducing tube currently used in clinical practice, are effective in regenerating peripheral nerves. Dedifferentiated fat (DFAT) cells differentiate into various cells including adipocytes, osteoblasts, chondrocytes, skeletal muscle cells, and myofibroblasts, when cultured in appropriate differentiation-inducing conditioned culture medium. This study made a hybrid artificial nerve conduit by filling a PGA conduit with DFAT cells, applied the conduit to a rat facial nerve defect model, and investigated the facial nerve regenerative ability of the conduit.

Methods

Under inhalational anesthesia, the buccal branch of the facial nerve in Lewis rats was exposed, and a 7-mm nerve defect was created. PGA nerve conduits were filled with DFAT cells, which were prepared from rat subcutaneous adipose tissue with type I collagen as a scaffold, and then grafted into the nerve defect sites in rats with a microscope (DFAT group) (n = 10). In other rats, PGA artificial nerve conduits alone were similarly grafted into the nerve defect sites (the control group) (n = 10). Reinnervation was confirmed at 13 weeks postoperatively by a retrograde tracer, followed by histological and physiological comparative studies.

Results

The mean number of myelinated fibers was significantly higher in DFAT group (1605 ± 806.23) than in the control group (543.6 ± 478.66). Myelin thickness was also significantly lager in DFAT group (0.57 ± 0.17 μm) than in the control group.

(0.46 ± 0.14 μm). Although no significant difference was found in the amplitude of compound muscle action potential (CMAP) between DFAT group (2.84 ± 2.47 mV) and the control group (0.88 ± 0.56 mV), whisker motion was lager in DFAT group (9.22° ± 0.65°) than in the control group (1.9° ± 0.84°).

Conclusions

DFAT cell-filled PGA conduits were found to promote nerve regeneration in an experimental rat facial nerve defect model.

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PGA artificial conduits containing DFAT cells were made in this study.

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The facial nerve regenerative ability of conduits was evaluated in a rat model.

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Reinnervation was confirmed at 13 weeks postoperatively.

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The nerve regeneration promoting effect of DFAT cells was found in the model.

Adipose-derived stem cells and the stromal vascular fraction in polyglycolic acid-collagen nerve conduits promote rat facial nerve regeneration

Adipose-derived stem cells (ADSCs) and the stromal vascular fraction (SVF) promote nerve regeneration. Biodegradable nerve conduits are used to treat peripheral nerve injuries, but their efficiencies are lower than those of autologous nerve grafts. This study developed biodegradable nerve conduits containing ADSCs and SVF and evaluated their facial nerve regenerating abilities in a rat model with a 7-mm nerve defect. SVF and ADSCs were individually poured into nerve conduits with polyglycolic acid-type I collagen as a scaffold (ADSCs and SVF groups). The conduits were grafted on to the nerve defects. As the control, the defect was bridged with polyglycolic acid-collagen nerve conduits without cells. At 13 weeks, after transplantation, the regenerated nerves were evaluated physiologically and histologically. The compound muscle action potential of the SVF group was significantly higher in amplitude than that of the control group. Electron microscopy showed that the axon diameter of the SVF group was the largest, followed by the ADSC group and control group with significant differences among them. The SVF group had the largest fiber diameter, followed by the ADSC group and control group with significant differences among them. The ADSC group had the highest myelin thickness, followed by the SVF group and control group with significant differences among them. Identical excellent promoting effects on nerve regeneration were observed in both the ADSC and SVF groups. Using SVF in conduits was more practical than using ADSCs because only the enzymatic process was required to prepare SVF, indicating that SVF could be more suitable to induce nerve regeneration.

A method package for electrophysiological evaluation of reconstructed or regenerated facial nerves in rodents

Compound muscle action potential (CMAP) recording via reconstructed or regenerated motor axons is a critical examination to evaluate newly developed surgical and regeneration techniques. However, there is currently no documentation on technical aspects of CMAP recordings via reconstructed or regenerated facial nerves. We have studied new techniques of plastic surgery and nerve regeneration using a rat facial nerve defect model for years, standardizing an evaluation pipeline using CMAP recordings. Here we describe our CMAP recording procedure in detail as a package including surgical preparation, data acquisition, analysis and troubleshooting. Each resource is available in public repositories and is maintained as a version control system. In addition, we demonstrate that our analytical pipeline can not only be applied to rats, but also mice. Finally, we show that CMAP recordings can be practically combined with other behavioral and anatomical examinations. For example, retrograde motor neuron labeling provides anatomical evidence for physical routes between the facial motor nucleus and its periphery through reconstructed or regenerated facial nerves, in addition to electrophysiological evidence by CMAP recordings from the same animal. •Standardized surgical, recording and analytical procedures for the functional evaluation of reconstructed or regenerated facial nerves of rats, extended to mice.•The functional evaluation can be combined with anatomical evaluations.•The methods described here are maintained in public repositories as version control systems.

Facial-nerve regeneration ability of a hybrid artificial nerve conduit containing uncultured adipose-derived stromal vascular fraction: An experimental study

PURPOSE

This study investigated the potential of uncultured-stromal-vascular-fraction (SVF) cells in promoting facial nerve regeneration in a rat model.

MATERIALS AND METHODS

A 7-mm nerve defect was created in the buccal branch of facial nerve in five groups of Lewis rats (total n = 30, n = 6 per group). A silicone tube, infused with syngeneic uncultured-SVF was implanted into the facial nerve defect. Groups 1-3 received 1 × 10³ , 1 × 10⁵ , and 1 × 10⁷ cells, and regenerated nerves were examined at 13 weeks after the surgery. The findings were compared to the autograft and collagen-alone groups with facial palsy score (FPS), the number of myelinated fibers, fiber diameter, axon diameter, myelin thickness, and g ratio.

RESULTS

There was no significant difference in FPS between the autograft and 1 × 10⁵ -cell groups at 13 weeks after surgery, and FPS values of these two groups were significantly higher than those of the other three groups (P < 0.01). Axon diameter significantly increased in the 1 × 10⁵ -cell group compared with the 1 × 10³ - (P < 0.05) and 1 × 10⁷ -cell groups (P < 0.01). Myelin thickness was found to be the highest in the autograft group, followed by the 1 × 10⁵ -, 1 × 10³ -, 1 × 10⁷ -cell, and negative control groups, and there were significant differences among all groups (P < 0.01).

CONCLUSION

The infusion of uncultured-SVF into the artificial nerve conduit promoted optimal nerve regeneration that was significantly better than nerve conduit alone. © 2016 Wiley Periodicals, Inc. Microsurgery 37:808-818, 2017.

Effectively Axonal-supercharged Interpositional Jump-Graft with an Artificial Nerve Conduit for Rat Facial Nerve Paralysis

BACKGROUND

Interpositional jump graft (IPJG) is a nerve graft axonally supercharged from the hypoglossal nerve. However, for using the technique, an autologous nerve, which should contain the great auricular and sural nerves, must be obtained. Depending on the donor site, unavoidable issues such as nerve disorders and postoperative scarring may appear. To reduce the issues, in this study, the authors developed an end-to-side neurorrhaphy technique with the recipient nerve and an artificial nerve conduit and investigated the efficacy of an IPJG with an artificial nerve conduit in a rat facial nerve paresis model.

METHODS

A ligature clip was used to crush the facial nerve trunk, thereby creating a partial facial nerve paresis model. An artificial nerve conduit was then prepared with a 10-mm-long silicone tube containing 10 μL type I collagen and used to create an IPJG between the facial nerve trunk and the hypoglossal nerve (the silicone tube group). Thirteen weeks after the surgery, the outcome was histologically and physiologically compared with conventional IPJG with autograft using the great auricular nerve.

RESULTS

Retrograde tracer test confirmed a double innervation by the facial and hypoglossal nerve nuclei. In the autograft and silicone tube groups, the regeneration of myelinated axons was observed.

CONCLUSION

In this study, the authors successfully developed an end-to-side neurorrhaphy technique with the recipient nerve and an artificial nerve conduit, and revealed that an IPJG in the conduit was effective in the rat facial nerve paresis model.

Adipocyte-derived and dedifferentiated fat cells promoting facial nerve regeneration in a rat model

BACKGROUND

Dedifferentiated fat cells, obtained from the ex vivo ceiling culture of mature adipocytes of mammals, have a high proliferative potential and pluripotency. The authors transplanted dedifferentiated fat cells into a nerve defect created in rat facial nerve and evaluated nerve regeneration ability.

METHODS

The buccal branch of the facial nerve of rats was exposed, and a 7-mm nerve defect was created. Green fluorescent protein-positive dedifferentiated fat cells prepared from adipocytes were mixed with type 1 collagen scaffold and infused into a silicone tube, which was then transplanted into the nerve defect in a green fluorescent protein-negative rat (the dedifferentiated fat group). Regenerated nerves were excised at 13 weeks after transplantation and examined histologically and physiologically. The findings were compared with those of autografts and silicone tubes loaded with collagen gel alone (the control group) transplanted similarly.

RESULTS

Axon diameter of regenerated nerve increased significantly in the dedifferentiated fat group compared with the control group, whereas no significant difference was found between the dedifferentiated fat and autograft groups. Myelin thickness was found to be largest in the autograft group, followed by the dedifferentiated fat and the control groups, showing significant differences between all pairs of groups. Evaluation of physiologic function of nerves by compound muscle action potential revealed a significantly better result in the dedifferentiated fat group than in the control group. The regenerated nerves in the dedifferentiated fat group had S100 and green fluorescent protein-double-positive Schwann-like supportive cells.

CONCLUSION

After being transplanted into a facial nerve defect, dedifferentiated fat cells promoted the maturation of the regenerated nerve.

Facial nerve regeneration using basic fibroblast growth factor-impregnated gelatin microspheres in a rat model

Basic fibroblast growth factor (bFGF) plays a crucial role in the regeneration of peripheral nerve defects by affecting nerve cells, Schwann cells and fibroblasts, and by promoting axon outgrowth from the proximal nerve stump. However, the use of exogenous bFGF for in vivo regeneration of the peripheral nerves is limited by its short in vivo half-life. In this study, a drug delivery system for bFGF was developed that uses acidic gelatin hydrogel, which sustainably released bFGF in vivo over several weeks; its ability to promote peripheral nerve regeneration was also examined. In 8-week-old Lewis rats, 7-mm gaps were made in the buccal branch of the left facial nerve. Acidic gelatin hydrogel microspheres (10 µl) with or without bFGF (50 µg) were infused into a 10 mm silicone tube using a micropipette, and the silicone tube was then implanted into the gap. A 1-mm long nerve stump was inserted into each end of the tube. Histological examination at 7 weeks after implantation revealed (1) a significantly increased rate of nerve regeneration, (2) inducement of a number of regenerating nerve axons, and (3) a better degree of maturation of nerve axons in the bFGF microsphere group than that in the bFGF-free microsphere group. Copyright © 2014 John Wiley & Sons, Ltd.