Study on Peripheral Nerve Regeneration Based on Multi-Gradient MgO/MgCO₃/PCL Nanofiber Membranes

Academic Background

Peripheral nerve defects are a common and complex orthopedic issue in clinical practice, with limited efficacy of current treatments. The insufficient proliferation and dysfunction of Schwann cells within nerve scaffolds are key factors affecting nerve repair outcomes. Magnesium ions (Mg²⁺) play an important role in peripheral nerve regeneration, but traditional magnesium-based biomaterials suffer from the rapid release of magnesium ions, making it difficult to sustain their effects during the intermediate and late stages of nerve regeneration. Additionally, the molecular mechanisms by which magnesium-based nerve scaffolds modulate peripheral nerve regeneration remain unclear. Therefore, developing a nerve scaffold material capable of sustained release of magnesium ions and elucidating its mechanisms is of great significance for improving peripheral nerve repair outcomes.

Source of the Paper

This paper was co-authored by Zhi Yao, Ziyu Chen, Xuan He, and others, affiliated with institutions such as Peking University Shenzhen Hospital and The Chinese University of Hong Kong. The paper was published online on November 8, 2024, in the journal Advanced Fiber Materials (Volume 7, 2025, pages 315–337), titled “Bioactive MgO/MgCO₃/Polycaprolactone Multi-Gradient Fibers Facilitate Peripheral Nerve Regeneration by Regulating Schwann Cell Function and Activating Wingless/Integrase-1 Signaling.”

Research Process and Results

1. Study Design

This study utilized electrospinning technology to fabricate MgO/MgCO₃/polycaprolactone (PCL) multi-gradient nanofiber membranes, aiming to achieve sustained release of magnesium ions by adjusting the proportions and concentrations of MgO and MgCO₃. The research was divided into several steps:
- Material Preparation: PCL was mixed with different proportions of MgO and MgCO₃, and a three-layered nanofiber membrane was prepared using electrospinning technology.
- In Vitro Experiments: The fiber structure was analyzed using scanning electron microscopy (SEM), magnesium ion release curves were determined, and cell culture experiments were conducted to evaluate the material’s effects on Schwann cell proliferation and migration.
- Animal Experiments: The prepared multi-gradient fibers were combined with 3D-printed PCL nerve conduits and implanted into a 10 mm sciatic nerve defect model in rats to assess nerve regeneration outcomes.

2. Material Preparation and Characterization

By adjusting the proportions of MgO and MgCO₃, the study successfully prepared three multi-gradient nanofiber membranes with different concentrations (10%, 20%, and 30% MgO/MgCO₃/PCL). Experimental results showed that the 10% MgO/MgCO₃/PCL group exhibited the most stable and effective magnesium ion release over six weeks. SEM analysis revealed fiber diameters ranging from 126.8 nm to 253.6 nm, with MgO/MgCO₃ nanoparticles distributed on the fiber surfaces. Contact angle tests indicated no significant differences in surface wettability among the groups, suggesting that magnesium ion release was the primary mechanism promoting nerve regeneration.

3. In Vitro Experiments

In vitro experiments first evaluated the promoting effect of magnesium ions on neurite outgrowth using dorsal root ganglion (DRG) cultures. The results showed that 10 mM and 20 mM magnesium ions significantly promoted DRG neurite extension. Additionally, primary Schwann cell cultures demonstrated that magnesium ions could enhance Schwann cell proliferation and phenotypic transition, shifting them toward a reparative Schwann cell (RSC) phenotype. Gene expression analysis revealed that magnesium ions upregulated the expression of various axon guidance molecules (e.g., Netrins, Ephrins) and neurotrophic factors (e.g., NGF, BDNF).

4. Animal Experiments

In a rat sciatic nerve defect model, the multi-gradient fibers were combined with PCL nerve conduits and implanted into the defect site. Evaluations at 6 and 12 weeks post-surgery showed that the 10% MgO/MgCO₃/PCL group exhibited the best nerve regeneration outcomes, characterized by significant improvements in axonal regeneration, remyelination, and muscle reinnervation. Histological staining and transmission electron microscopy (TEM) analysis further confirmed that the 10% MgO/MgCO₃/PCL group outperformed other groups in terms of myelin sheath thickness and axon count.

5. Molecular Mechanism Research

Through transcriptome sequencing and Western blot analysis, the study found that magnesium ions regulate Schwann cell function by activating the Wnt signaling pathway. Specifically, magnesium ions upregulated the expression of Wnt5a, β-catenin, and CREB, promoting Schwann cell proliferation and migration. Furthermore, magnesium ions inhibited calcium ion (Ca²⁺) influx, attenuating Wnt/Ca²⁺ pathway activity and enhancing the role of the Wnt/β-catenin signaling pathway.

Conclusions and Significance

This study successfully developed a nerve scaffold material based on MgO/MgCO₃/PCL multi-gradient nanofiber membranes, capable of controlled magnesium ion release. The material significantly promoted nerve regeneration in a rat sciatic nerve defect model. The research elucidated the molecular mechanisms by which magnesium ions regulate Schwann cell function through the Wnt signaling pathway, providing a solid theoretical foundation for the clinical application of magnesium-based nerve scaffolds. This material offers advantages such as low preparation cost, high efficiency, and broad adaptability, demonstrating the immense potential of magnesium-based biomaterials in the treatment of nervous system diseases.

Research Highlights

1. Innovative Material Design: By adjusting the proportions of MgO and MgCO₃, controlled release of magnesium ions was achieved, addressing the issue of rapid release in traditional magnesium-based materials.
   
2. Comprehensive Mechanism Research: For the first time, the molecular mechanisms by which magnesium ions regulate Schwann cell function through the Wnt signaling pathway were elucidated.
   
3. Significant Nerve Regeneration Outcomes: In the animal model, the 10% MgO/MgCO₃/PCL group demonstrated the best nerve regeneration outcomes, providing strong support for clinical applications.

Other Valuable Information

The limitations of this study include the inability to detect the actual magnesium ion concentration in the local nerve regeneration microenvironment. Future research could further optimize material design and incorporate drugs, cells, and other active ingredients to enhance the therapeutic efficacy of magnesium-based nerve scaffolds.