Research Article: Mechanical properties of the sciatic nerve following combined transplantation of analytically extracted acellular allogeneic nerve and adipose-derived mesenchymal stem cells1

Date Published: June 12, 2020

Publisher: Sociedade Brasileira para o Desenvolvimento da Pesquisa em Cirurgia

Author(s): Chengdong Piao, Zhengwei Li, Jie Ding, Daliang Kong.

http://doi.org/10.1590/s0102-865020200040000005

Abstract

To investigate the effects of Chemically Extracted Acellular Nerves (CEANs) when combined with Adipose-Derived mesenchymal Stem Cell (ADSC) transplantation on the repair of sciatic nerve defects in rabbits.

A total of 71 six-month-old Japanese rabbit were used in this study. Twenty rabbits served as sciatic nerve donors, while the other 51 rabbits were randomly divided into Autologous Nerve Transplantation Group (ANT, n=17), CEAN group (n=17) and CEAN-ADSCs group (n=17). In all these groups, the rabbit’s left sciatic nerves were injured before the experiment, and the uninjured sciatic nerves on their right side were used as the control (CON). Electrophysiological tests were carried out and sciatic nerves were prepared for histomorphology and stretch testing at 24 weeks post-transplant.

There were significant differences between ANT and Con groups in amplitude (AMP): P=0.031; motor nerve conduction velocity (MNCV): P=0.029; Maximum stress: P=0.029; and Maximum strain P=0.027. There were also differences between the CEAN and CEAN+ADSCs groups in AMP: P=0.026, MNCV: P=0.024; Maximum stress: P=0.025 and Maximum strain: P=0.030. No significant differences in these parameters were observed when comparing the ANT and CEAN+SACN groups (MNCV: P=0.071) or the CEAN and ANT groups (Maximum stress: P=0.069; Maximum strain P=0.077).

Addition of ADSCs has a significant impact on the recovery of nerve function, morphology, and tensile mechanical properties following sciatic nerve injury.

Partial Text

Peripheral nerve injury is very common in trauma, and accounts for 2.8% of all trauma patients every year. Nerve injury regeneration and repair has always been an important field of research1. Sciatic nerve injury is one of the most common peripheral nerve injuries, and is usually caused by trauma or severe pull injury. The repair and regeneration of injured sciatic nerves can be difficult because of micro environment changes2,3. The development of tissue engineering technology has provided new avenues for repair using “suitable scaffold material, ideal seed cells, and appropriate induction of differentiation”4-6. In recent years, some researchers have investigated combining acellular nerve scaffolds with mesenchymal stem cells or Schwann cells in tissue engineering applications to repair nerve defects7,8. Adipose-derived mesenchymal stem cells (ADSCs) are of great importance since they play an important role in immunoregulation and tissue repair, especially in nerve repair processes9. Chemically extracted acellular allogeneic nerves retain their natural structure but do not incorporate the myelin sheath or Schwann cells (SCs) reducing immunogenicity10. Kingham et al.11 transplanted differentiated Adipose-derived stem cells (ADSCs) into rat sciatic nerve transections and found that the length of the regenerated axons in the sciatic nerve of the transplanted rats was longer than the same nerve in the control group 2 weeks after treatment. Masgutov et al.12studied the effect of allogeneic adipose-derived stem cell (ADSCs) transplantation on sciatic nerve regeneration in rats after trauma. Here they proposed a novel method for evaluating sciatic nerve reconstruction in rats, which used the nerve from the other leg as a graft, which allowed them to compare the 10 mm nerve defect repaired by autologous nerve graft and that of the opposite side. It was found that there were obvious destructive changes in the sciatic nerve tissue following the operation, which resulted in joint contracture in both the knees and ankles, and neurotrophic ulceration in the right limb. ADSCs stimulated regeneration increased the survival of L5 ganglion neurons by 26.4%, the vascularization of sciatic nerves by 35.68%, and the myelin sheath fibers of distal nerves by 41.87%. It was also reported that the expression levels of the S100, PMP2 and PPM22 genes were inhibited in traumatic responses when compared to systems without trauma, supporting their conclusion that ADSCs treatment could significantly improve nerve regeneration.

All experiments were carried out at the Mechanical Experimental Center of Jilin University and the Experimental Center of the Second Hospital of Jilin University.

The results showed that there was no significant difference in the electrophysiological parameters between the CEAN-ADSCs group and the ANT group, but CEAN-ADSCs group’s were better than those of the CEA group with statistical significance. Compared with the CEAN group, the nerve conduction speed was accelerated, the latency was shortened, and the amplitude of action potential was increased in the CEAN-ADSCs group and the ANT group. The morphology of the injured sciatic nerve tissue in the CEAN-ADSCs group had better restoration than the CEAN group, suggesting that ADSCs effect repair of the histomorphological characteristics of injured sciatic nerves in animal models, but the tissue morphology changes in the CEAN group may be the result of the chemical treatment. The tensile test results showed that there were no statistically significant differences in the tensile mechanical properties of the CEAN-ADSCs and ANT groups. There were, however, some statistically significant changes in these properties when comparing these groups to the CEAN group. These results suggest that chemical acellular nerve allograft combined with ADSCs can restore the elasticity and strength of sciatic nerves in animal models of sciatic nerve defects, which is consistent with the expected results. CEAN is a novel tissue engineering material with low immunogenicity and three-dimensional spatial structure17, making it an ideal substitute for autologous nerve transplantation. However, studies have shown that18,19 the process of nerve decellularization may remove one or more of the vital collagen components, resulting in changes in neuromechanical properties. Studies19,20 have also shown that although a single therapy treatment is helpful for axonal regeneration and functional recovery, the effects are not ideal. Only combination therapy can overcome the multiple factors that inhibit the regeneration of peripheral axons. Snow et al.21 pointed out that the most effective way to strengthen nerve regeneration is to use a combination of seed cell transplantation so as to provide a microenvironment suitable for nerve growth. In this study, the rabbit acellular sciatic nerve transplantation provided a microenvironment suitable for nerve growth, which showed significant improvement when combined with the transplantation of ADSCs into the decellularized sciatic nerve, where they secrete neurotrophic and adhesion factors, which aid the neural cells to bridge the nerve defects. The results of this experiment support Reference23 that suggests that the most effective way to strengthen nerve regeneration is to use a combination of seed cell transplantation to improve the microenvironment of the regenerating nerve and promote its growth.

Sciatic nerve injury interventions which include ADSCs can improve the neurological function indexes of an animal model with sciatic nerve injury, which also helped to return the electrophysiological indexes, tissue morphology and tensile mechanical properties of the sciatic nerve to normal.

 

Source:

http://doi.org/10.1590/s0102-865020200040000005

 

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