Elsevier

Brain Research Bulletin

Volume 139, May 2018, Pages 211-223
Brain Research Bulletin

Research report
Reactivation of denervated Schwann cells by neurons induced from bone marrow-derived mesenchymal stem cells

https://doi.org/10.1016/j.brainresbull.2018.03.005Get rights and content

Highlights

  • ā€¢

    Neurons were induced from bone marrow-derived mesenchymal stem cells.

  • ā€¢

    Co-culturing neurons reactivated denervated Schwann cells in vitro.

  • ā€¢

    Grafted neurons reactivated native denervated Schwann cells in vivo.

  • ā€¢

    Grafted neurons promoted sciatic nerve regeneration in vivo.

Abstract

The use of neurons induced from stem cells has been introduced as an effective strategy for promoting peripheral nerve regeneration (PNR). The evolution and role of native denervated Schwann cells (SCs) were often ignored when exploring the mechanisms underlying neural transplantation therapy for PNR. The aim of this study was to understand if following injury, native denervated SCs could be reactivated by transplanting of neurons induced from bone marrow-derived mesenchymal stem cells (NI-BMSCs) to promote PNR. We co-cultured denervated SCs with NI-BMSCs in vitro, tested the proliferation of denervated SCs, and measured the expression and secretion of neurotrophic factors and neural adhesion molecules of the denervated SCs. Concurrently, 48 adult male Sprague-Dawley rats were randomly divided into 4 even groups of 12 rats each: normal group, phosphate-buffered saline (PBS) injection group, BMSCs transplantation group and NI-BMSCs transplantation group. PBS injection and cells transplantation were performed 4 weeks post-injury. After 4 weeks of NI-BMSCs transplantation, the survival of seeded NI-BMSCs was examined, proliferation and ultrastructure of native denervated SCs were detected, and myelination, axonal regeneration and the sciatic functional index measurements were also determinated. Our results demonstrated that NI-BMSCs reactivated denervated SCs both in vitro and in vivo and promoted sciatic nerve regeneration.

Introduction

Peripheral nerve injury (PNI) is a significant source of long-term morbidity, disability and economic burden (Jones et al., 2016). The peripheral nervous system (PNS) differs from the central nervous system in that it shows a certain capacity for axonal regeneration, though spontaneous regeneration is always incomplete and often has poor outcomes (Du et al., 2017). In recent decades, cell-based therapy, including embryonic (Cui et al., 2008) and mesenchymal stem cells (Pan et al., 2017; Zheng et al., 2017a), as well as Schwann cells (SCs) (Levi et al., 2016) have been proven promising for promoting neuroregeneration. Moreover, our group and others have introduced neurons induced from stem cells as an effective strategy for promoting peripheral nerve regeneration (PNR) (Lin et al., 2009; Kurimoto et al., 2016; Ullah et al., 2017; Zhang et al., 2017).

Previous studies have demonstrated that grafted neurons can survive in peripheral nerves, express neuronal marker, and even form neuromuscular junctions and delay muscle atrophy after PNI (MacDonald et al., 2003; Lin et al., 2009; Gu et al., 2010). However, the mechanisms underlying neural transplantation therapy for PNR after injury are still not fully understood. Furthermore, the evolution and role of native denervated SCs in neural transplantation therapy were often neglected and thus are still unknown. SCs play a significant role in PNR; they switch into acute denervated SCs post-injury and then proliferate quickly, form the Bungnerā€™s bands, and promote nerve regeneration. All of these functions for promoting regeneration of acute denervated SCs depends on axon-SCs interactions (Corfas et al., 2004). Based on the axon-SCs interactions, we hypothesized that transplantation of neurons could form axon-SCs interactions to reactivate denervated SCs and promote PNR.

In the present study, we co-cultured denervated SCs with NI-BMSCs that were induced from bone marrow-derived mesenchymal stem cells (BMSCs) by our own methods (Zhang and Alexanian, 2014; Zheng et al., 2017b) and then examined the proliferation of denervated SCs and the expression of neurotrophic factors and adhesion molecules from these cells in vitro. NI-BMSCs were transplanted into the distal stump in a sciatic nerve injury model, the survival of the grafted NI-BMSCs; the morphology, arrangement and quantity of native denervated SCs were examined, myelination, axonal regeneration and sciatic nerve functional recovery were also determinated. Our data indicated that transplanted NI-BMSCs reactivated denervated SCs and promoted sciatic nerve regeneration.

Section snippets

Animals and sciatic nerve injury model

Male Sprague-Dawley (SD) rats and transgenic green fluorescent protein (GFP) SD rats were purchased from the Animal Center of the Second Military Medical University (Shanghai, China). All animal experiments were approved by the Animal Care and Use Committee of the Second Military Medical University (permit number SYXK-2002-042).

Forty-eight adult male SD rats, weighing 180ā€“220ā€Æg, were randomly divided into 4 groups of 12 rats each: normal group (Normal, without injury), phosphate-buffered saline

Characteristics of SCs

After 48ā€Æh incubation, cells began to grow from the nerve segments, and many cells climbed out after 5ā€Ædays, forming a classical parallel swirling alignment of dendritic processes (Fig. 1Aā€“D). After purification by cytarabine and passed to the fourth generation, SCs were growing homogeneously and displayed a long bipolar or tripolar elongated shape with a small oval-shaped nucleus (Fig. 1Eā€“F).

To further explore the characteristics of the cells which had grown from nerve segments, S100Ī² which

Discussion

In this study, we demonstrated that NI-BMSCs triggered the proliferation of denervated SCs as well as the expression and secretion of neurotrophic factors and neural adhesion molecules in vitro. We also found that grafted NI-BMSCs accelerated the proliferation of native denervated SCs, enhanced myelination and axonal regeneration, and promoted regeneration of sciatic nerves in rats. And compared to BMSCs, NI-BMSCs had more effective promotion for sciatic nerves regeneration.

Conclusion

In current study, NI-BMSCs were co-cultured with denervated SCs in vitro and transplanted in a rat sciatic nerve injury model. It was demonstrated that co-culturing SCs with NI-BMSCs accelerated the proliferation of denervated SCs and promoted the expression and secretion of neurotrophic factors and neural adhesion molecules in vitro. In addition, it was also revealed that NI-BMSCs reactivated native denervated SCs, facilitated their proliferation as well as enhancing myelination, axonal

Conflict of interests

The authors declare no conflict of interests.

Acknowledgement

This work was supported by the Funds of the National Natural Science Foundation of China (81271396).

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