Schwann cell‑derived exosomes induce bone marrow‑derived mesenchymal stem cells to express Schwann cell markers in vitro

Preliminary study on the preparation of lyophilized acellular nerve scaffold complexes from rabbit sciatic nerves with human umbilical cord mesenchymal stem cells

BACKGROUND

The gold standard of care for patients with severe peripheral nerve injury is autologous nerve grafting; however, autologous nerve grafts are usually limited for patients because of the limited number of autologous nerve sources and the loss of neurosensory sensation in the donor area, whereas allogeneic or xenografts are even more limited by immune rejection. Tissue-engineered peripheral nerve scaffolds, with the morphology and structure of natural nerves and complex biological signals, hold the most promise as ideal peripheral nerve "replacements".

AIM

To prepare allogenic peripheral nerve scaffolds using a low-toxicity decellularization method, and use human umbilical cord mesenchymal stem cells (hUC-MSCs) as seed cells to cultivate scaffold-cell complexes for the repair of injured peripheral nerves.

METHODS

After obtaining sciatic nerves from New Zealand rabbits, an optimal acellular scaffold preparation scheme was established by mechanical separation, varying lyophilization cycles, and trypsin and DNase digestion at different times. The scaffolds were evaluated by hematoxylin and eosin (HE) and luxol fast blue (LFB) staining. The maximum load, durability, and elastic modulus of the acellular scaffolds were assessed using a universal material testing machine. The acellular scaffolds were implanted into the dorsal erector spinae muscle of SD rats and the scaffold degradation and systemic inflammatory reactions were observed at 3 days, 1 week, 3 weeks, and 6 weeks following surgery to determine the histocompatibility between xenografts. The effect of acellular scaffold extracts on fibroblast proliferation was assessed using an MTT assay to measure the cytotoxicity of the scaffold residual reagents. In addition, the umbilical cord from cesarean section fetuses was collected, and the Wharton's jelly (WJ) was separated into culture cells and confirm the osteogenic and adipogenic differentiation of mesenchymal stem cells (MSCs) and hUC-MSCs. The cultured cells were induced to differentiate into Schwann cells by the antioxidant-growth factor induction method, and the differentiated cells and the myelinogenic properties were identified.

RESULTS

The experiments effectively decellularized the sciatic nerve of the New Zealand rabbits. After comparing the completed acellular scaffolds among the groups, the optimal decellularization preparation steps were established as follows: Mechanical separation of the epineurium, two cycles of lyophilization-rewarming, trypsin digestion for 5 hours, and DNase digestion for 10 hours. After HE staining, no residual nuclear components were evident on the scaffold, whereas the extracellular matrix remained intact. LFB staining showed a significant decrease in myelin sheath composition of the scaffold compared with that before preparation. Biomechanical testing revealed that the maximum tensile strength, elastic modulus, and durability of the acellular scaffold were reduced compared with normal peripheral nerves. Based on the histocompatibility test, the immune response of the recipient SD rats to the scaffold New Zealand rabbits began to decline3 weeks following surgery, and there was no significant rejection after 6 weeks. The MTT assay revealed that the acellular reagent extract had no obvious effects on cell proliferation. The cells were successfully isolated, cultured, and passaged from human umbilical cord WJ by MSC medium, and their ability to differentiate into Schwann-like cells was demonstrated by morphological and immunohistochemical identification. The differentiated cells could also myelinate in vitro.

CONCLUSION

The acellular peripheral nerve scaffold with complete cell removal and intact matrix may be prepared by combining lyophilization and enzyme digestion. The resulting scaffold exhibited good histocompatibility and low cytotoxicity. In addition, hUC-MSCs have the potential to differentiate into Schwann-like cells with myelinogenic ability following in vitro induction.

Recent perspectives on the synergy of mesenchymal stem cells with micro/nano strategies in peripheral nerve regeneration-a review

Despite the intrinsic repair of peripheral nerve injury (PNI), it is important to carefully monitor the process of peripheral nerve repair, as peripheral nerve regeneration is slow and incomplete in large traumatic lesions. Hence, mesenchymal stem cells (MSCs) with protective and regenerative functions are utilized in synergy with innovative micro/nano technologies to enhance the regeneration process of peripheral nerves. Nonetheless, as MSCs are assessed using standard regenerative criteria including sensory-motor indices, structural features, and morphology, it is challenging to differentiate between the protective and regenerative impacts of MSCs on neural tissue. This study aims to analyze the process of nerve regeneration, particularly the performance of MSCs with and without synergistic approaches. It also focuses on the paracrine secretions of MSCs and their conversion into neurons with functional properties that influence nerve regeneration after PNI. Furthermore, the study explores new ideas for nerve regeneration after PNI by considering the synergistic effect of MSCs and therapeutic compounds, neuronal cell derivatives, biological or polymeric conduits, organic/inorganic nanoparticles, and electrical stimulation. Finally, the study highlights the main obstacles to developing synergy in nerve regeneration after PNI and aims to open new windows based on recent advances in neural tissue regeneration.

Mesenchymal Stem Cell-Derived Extracellular Vesicles in Bone-Related Diseases: Intercellular Communication Messengers and Therapeutic Engineering Protagonists

Extracellular vesicles (EVs) can deliver various bioactive molecules among cells, making them promising diagnostic and therapeutic alternatives in diseases. Mesenchymal stem cell-derived EVs (MSC-EVs) have shown therapeutic potential similar to MSCs but with drawbacks such as lower yield, reduced biological activities, off-target effects, and shorter half-lives. Improving strategies utilizing biotechniques to pretreat MSCs and enhance the properties of released EVs, as well as modifying MSC-EVs to enhance targeting abilities and achieve controlled release, shows potential for overcoming application limitations and enhancing therapeutic effects in treating bone-related diseases. This review focuses on recent advances in functionalizing MSC-EVs to treat bone-related diseases. Firstly, we underscore the significance of MSC-EVs in facilitating crosstalk between cells within the skeletal environment. Secondly, we highlight strategies of functional-modified EVs for treating bone-related diseases. We explore the pretreatment of stem cells using various biotechniques to enhance the properties of resulting EVs, as well as diverse approaches to modify MSC-EVs for targeted delivery and controlled release. Finally, we address the challenges and opportunities for further research on MSC-EVs in bone-related diseases.

The Therapeutic Potential of Exosomes in Soft Tissue Repair and Regeneration

Soft tissue defects are common following trauma and tumor extirpation. These injuries can result in poor functional recovery and lead to a diminished quality of life. The healing of skin and muscle is a complex process that, at present, leads to incomplete recovery and scarring. Regenerative medicine may offer the opportunity to improve the healing process and functional outcomes. Barriers to regenerative strategies have included cost, regulatory hurdles, and the need for cell-based therapies. In recent years, exosomes, or extracellular vesicles, have gained tremendous attention in the field of soft tissue repair and regeneration. These nanosized extracellular particles (30-140 nm) can break the cellular boundaries, as well as facilitate intracellular signal delivery in various regenerative physiologic and pathologic processes. Existing studies have established the potential of exosomes in regenerating tendons, skeletal muscles, and peripheral nerves through different mechanisms, including promoting myogenesis, increasing tenocyte differentiation and enhancing neurite outgrowth, and the proliferation of Schwann cells. These exosomes can be stored for immediate use in the operating room, and can be produced cost efficiently. In this article, we critically review the current advances of exosomes in soft tissue (tendons, skeletal muscles, and peripheral nerves) healing. Additionally, new directions for clinical applications in the future will be discussed.

Effect of treadmill exercise combined with bone marrow stromal cell transplantation on atrophy-related signaling pathway in the denervated soleus muscle

The purpose of this study was to investigate whether combination of low-intensity exercise with bone marrow stromal cell (BMSC) transplantation could regulate protein kinas B (Akt)-mammalian target of rapamycin (mTOR) and Wnt3a-β-catenin signaling pathways for prevention of soleus muscle atrophy after sciatic nerve injury (SNI). The experimental rats divided into 5 groups (n=10): normal control group, SNI+sedentary group (SED), SNI+low-intensity treadmill exercise group (TEX), SNI+BMSC transplantation group (BMSC), SNI+TEX+BMSC transplantation group (TEX+BMSC). Sciatic nerve crush injury was applied into the middle of thigh twice for 1 min and 30 sec at interval. Low-intensity treadmill exercise was comprised of walking at a speed of 4 to 8 m/min for 30 min once a day. cultured BMSC at a density of 5×10⁶ in 50-μL phosphate-buffered saline was injected into the distal portion of the injured sciatic nerves. TEX+BMSC group dramatically up-regulated expression levels of growth-associated protein-43 in the injured sciatic nerve at 2 weeks postinjury. Also, although Akt and mTOR signaling pathway significantly increased in TEX and BMSC groups than SED group, TEX+BMSC group showed more potent increment on this signaling in soleus muscle after SNI. Lastly, Wnt3a and the nuclear translocation of β-catenin and nuclear factor-kappa B in soleus were increased by SNI, but TEX+BMSC group significantly downregulated activity of this signaling pathway in the nuclear cell lysate of soleus muscle. Present findings provide new information that combination of low-intensity treadmill exercise might be effective therapeutic approach on restriction of soleus muscle atrophy after peripheral nerve injury.