Reactivation of Denervated Schwann Cells by Embryonic Spinal Cord Neurons to Promote Axon Regeneration and Remyelination

Engineering the Future of Restorative Clinical Peripheral Nerve Surgery

Peripheral nerve injury is a significant clinical challenge, often leading to permanent functional deficits. Standard interventions, such as autologous nerve grafts or distal nerve transfers, require sacrificing healthy nerve tissue and typically result in limited motor or sensory recovery. Nerve regeneration is complex and influenced by several factors: 1) the regenerative capacity of proximal neurons, 2) the ability of axons and support cells to bridge the injury, 3) the capacity of Schwann cells to maintain a supportive environment, and 4) the readiness of target muscles or sensory organs for reinnervation. Emerging bioengineering solutions, including biomaterials, drug delivery systems, fusogens, electrical stimulation devices, and tissue-engineered products, aim to address these challenges. Effective translation of these therapies requires a deep understanding of the physiology and pathology of nerve injury. This article proposes a comprehensive framework for developing restorative strategies that address all four major physiological responses in nerve repair. By implementing this framework, we envision a paradigm shift that could potentially enable full functional recovery for patients, where current approaches offer minimal hope.

The GDNF-gel/HA-Mg conduit promotes the repair of peripheral nerve defects by regulating PPAR-γ/RhoA/ROCK signaling pathway

Magnesium (Mg)-based conduits have gained more attention in repairing peripheral nerve defects. However, they are limited due to poor corrosion resistance and rapid degradation rate. To tackle this issue, glial cell line-derived neurotrophic factor (GDNF)- Gelatin methacryloyl (Gel)/hydroxylapatite (HA)-Mg nerve conduit was developed and implanted in sciatic nerve defect model in Sprague-Dawley (SD) rats. The sciatic functional index measurement showed that the GDNF-Gel/HA-Mg nerve conduit effectively promoted the recovery of sciatic nerve function. The pathological examination results showed that there were more regenerated nerve tissues in GDNF-Gel/HA-Mg group, with a higher number of regenerating axons, and the thickness of the myelin sheath was significantly larger than that of control group (NC group). Immunofluorescence results revealed that the GDNF-Gel/HA-Mg conduit significantly promoted the expression of genes associated with nerve repair. RNA-seq and molecular test results indicated that GDNF-Gel/HA-Mg might be involved in the repair of peripheral nerve defects by regulating PPAR-γ/RhoA/ROCK signaling pathway. Biological sciences; Neuroscience; Molecular neuroscience; Techniques in neuroscience.

Motor neurons transplantation alleviates neurofibrogenesis during chronic degeneration by reversibly regulating Schwann cells epithelial-mesenchymal transition

A novel understanding of peripheral nerve injury is epithelial-mesenchymal transition (EMT), which characterizes the process of dedifferentiation and transformation of Schwann cells after nerve injury. Despite being regarded as an important mechanism for healing nerve injuries, long-term EMT is the primary cause of fibrosis in other tissue organs. The potential mechanism promoting neurofibrosis in the process of chronic degeneration of nerve injury and the effects of motor neurons (MNs) transplantation on neurofibrosis and repair of nerve injury were studied by transcriptome sequencing and bioinformatics analysis, which were confirmed by in vivo and in vitro experiments. Even 3 months after nerve injury, the distal nerve maintained high levels of transforming growth factor β-1 (TGFβ-1) and Snail family transcriptional repressor 2 (Snai2). The microenvironment TGFβ-1, Snai2 and endogenous TGFβ-1 formed a positive feedback loop in vivo and in vitro, which may contribute to the sustained EMT state and neurofibrogenesis in the distal injured nerve. Inhibiting TGFβ-1 and Snai2 expression and reversing EMT can be achieved by transferring MNs to distal nerves, and the removal of transplanted MNs is capable of reactivating EMT and promoting the growth of proximal axons. In conclusion, EMT persisting can be an explanation for distal neurofibrosis and a potential therapeutic target. By reversibly regulating EMT, MNs transplantation can alleviate neurofibrogenesis of distal nerve in chronic degeneration.

Aloperine: A Potent Modulator of Crucial Biological Mechanisms in Multiple Diseases

Aloperine is an alkaloid found in the seeds and leaves of the medicinal plant Sophora alopecuroides L. It has been used as herbal medicine in China for centuries due to its potent anti-inflammatory, antioxidant, antibacterial, and antiviral properties. Recently, aloperine has been widely investigated for its therapeutic activities. Aloperine is proven to be an effective therapeutic agent against many human pathological conditions, including cancer, viral diseases, and cardiovascular and inflammatory disorders. Aloperine is reported to exert therapeutic effects through triggering various biological processes, including cell cycle arrest, apoptosis, autophagy, suppressing cell migration, and invasion. It has also been found to be associated with the modulation of various signaling pathways in different diseases. In this review, we summarize the most recent knowledge on the modulatory effects of aloperine on various critical biological processes and signaling mechanisms, including the PI3K, Akt, NF-κB, Ras, and Nrf2 pathways. These data demonstrate that aloperine is a promising therapeutic candidate. Being a potent modulator of signaling mechanisms, aloperine can be employed in clinical settings to treat various human disorders in the future.

Microvesicles from Schwann-Like Cells as a New Biomaterial Promote Axonal Growth

Schwann cells promote axonal regeneration following peripheral nerve injury. However, in terms of clinical treatment, the therapeutic effects of Schwann cells are limited by their source. The transmission of microvesicles from neuroglia cells to axons is a novel communication mechanism in axon regeneration.To evaluate the effect of microvesicles released from Schwann-like cells on axonal regeneration, neural stem cells derived from human embryonic stem cells differentiated into Schwann-like cells, which presented a typical morphology and characteristics similar to those of schwann cells. The glial markers like MBP, P0, P75^NTR, PMP-22, GFAP, HNK-1 and S100 were upregulated, whereas the neural stem markers like NESTIN, SOX1 and SOX2 were significantly downregulated in schwann-like cells. Microvesicles enhanced axonal growth in dorsal root ganglia neurons and regulated GAP43 expression in neuron-like cells (N2A and PC12) through the PTEN/PI3 K/Akt signaling pathway. A 5 mm section of sciatic nerve was transected in Sprague-Dawley rats. With microvesicles transplantation, regenerative nerves were evaluated after 6 weeks. Microvesicles increased sciatic function index scores, delayed gastrocnemius muscle atrophy and elevated βIII-tubulin-labeled axons in vivo. Schwann-like cells serve as a convenient source and promote axonal growth by secreting microvesicles, which may potentially be used as bioengineering materials for nerve tissue repair.

Polymer-Based Scaffold Strategies for Spinal Cord Repair and Regeneration

The injury to the spinal cord is among the most complex fields of medical development. Spinal cord injury (SCI) leads to acute loss of motor and sensory function beneath the injury level and is linked to a dismal prognosis. Currently, while a strategy that could heal the injured spinal cord remains unforeseen, the latest advancements in polymer-mediated approaches demonstrate promising treatment forms to remyelinate or regenerate the axons and to integrate new neural cells in the SCI. Moreover, they possess the capacity to locally deliver synergistic cells, growth factors (GFs) therapies and bioactive substances, which play a critical role in neuroprotection and neuroregeneration. Here, we provide an extensive overview of the SCI characteristics, the pathophysiology of SCI, and strategies and challenges for the treatment of SCI in a review. This review highlights the recent encouraging applications of polymer-based scaffolds in developing the novel SCI therapy.