Hypocapnia Stimuli-Responsive Engineered Exosomes Delivering miR-218 Facilitate Sciatic Nerve Regeneration

The Application of Stem Cells and Exosomes in Promoting Nerve Conduits for Peripheral Nerve Repair

The repair of peripheral nerve injury (PNI) presents a multifaceted and protracted challenge, with current therapeutic approaches failing to achieve optimal repair outcomes, thereby not satisfying the considerable clinical demand. The advent of tissue engineering has led to a growing body of experimental evidence indicating that the synergistic application of nerve conduits, which provide structural guidance, alongside the biological signals derived from exosomes and stem cells, yields superior therapeutic results for PNI compared to isolated interventions. This combined approach holds great promise for clinical application. In this review, we present the latest advancements in the treatment of PNI through the integration of stem cells or exosomes with nerve conduits. We have addressed the inadequate efficiency of exosomes or stem cells in conjunction with nerve conduits from 3 perspectives: enhancing stem cells or exosomes, improving nerve conduits, and incorporating physical stimulation.

Optimizing Conditions of Polyethylene Glycol Precipitation for Exosomes Isolation From MSCs Culture Media for Regenerative Treatment

Mesenchymal stem cell (MSC)-derived exosomes, as a cell-free alternative to MSCs, offer enhanced safety and significant potential in regenerative medicine. However, isolating these exosomes poses a challenge, complicating their broader application. Commonly used methods like ultracentrifugation (UC) and tangential flow filtration are often impractical due to the requirement for costly instruments and ultrafiltration membranes. Additionally, the high cost of commercial kits limits their use in processing large sample volumes. Polyethylene glycol (PEG) precipitation offers a more convenient and cost-effective alternative, but there is a critical need for optimized and standardized isolation protocols using PEG precipitation across different cell types and fluids to ensure consistent quality and yield. In this work, we optimized the PEG precipitation method for exosomes isolation and compared its effectiveness to two commonly used methods: UC and commercial exosome isolation kits (ExoQuick). The recovery rate of the optimized PEG method (about 61.74%) was comparable to that of the commercial ExoQuick kit (about 62.19%), which was significantly higher than UC (about 45.80%). Exosome cargo analysis validated no significant differences in miRNA and protein profiles associated with the proliferation and migration of exosomes isolated by UC and PEG precipitation, which was confirmed by gap closure and CCK8 assays. These findings suggest that PEG-based exosomes isolation could be a highly efficient and high-quality method and may facilitate the development of exosome-based therapies for regenerative medicine.

Engineered exosomes as a prospective therapy for diabetic foot ulcers

Diabetic foot ulcer (DFU), characterized by high recurrence rate, amputations and mortality, poses a significant challenge in diabetes management. The complex pathology involves dysregulated glucose homeostasis leading to systemic and local microenvironmental complications, including peripheral neuropathy, micro- and macro-angiopathy, recurrent infection, persistent inflammation and dysregulated re-epithelialization. Novel approaches to accelerate DFU healing are actively pursued, with a focus on utilizing exosomes. Exosomes are natural nanovesicles mediating cellular communication and containing diverse functional molecular cargos, including DNA, mRNA, microRNA (miRNA), lncRNA, proteins, lipids and metabolites. While some exosomes show promise in modulating cellular function and promoting ulcer healing, their efficacy is limited by low yield, impurities, low loading content and inadequate targeting. Engineering exosomes to enhance their curative activity represents a potentially more efficient approach for DFUs. This could facilitate focused repair and regeneration of nerves, blood vessels and soft tissue after ulcer development. This review provides an overview of DFU pathogenesis, strategies for exosome engineering and the targeted therapeutic application of engineered exosomes in addressing critical pathological changes associated with DFUs.

Exosomes repairment for sciatic nerve injury: a cell-free therapy

Sciatic nerve injury (SNI) is a common type of peripheral nerve injury typically resulting from trauma, such as contusion, sharp force injuries, drug injections, pelvic fractures, or hip dislocations. It leads to both sensory and motor dysfunctions, characterized by pain, numbness, loss of sensation, muscle atrophy, reduced muscle tone, and limb paralysis. These symptoms can significantly diminish a patient's quality of life. Following SNI, Wallerian degeneration occurs, which activates various signaling pathways, inflammatory factors, and epigenetic regulators. Despite the availability of several surgical and nonsurgical treatments, their effectiveness remains suboptimal. Exosomes are extracellular vesicles with diameters ranging from 30 to 150 nm, originating from the endoplasmic reticulum. They play a crucial role in facilitating intercellular communication and have emerged as highly promising vehicles for drug delivery. Increasing evidence supports the significant potential of exosomes in repairing SNI. This review delves into the pathological progression of SNI, techniques for generating exosomes, the molecular mechanisms behind SNI recovery with exosomes, the effectiveness of combining exosomes with other approaches for SNI repair, and the changes and future outlook for utilizing exosomes in SNI recovery.

Therapeutic Potential of Mesenchymal Stem Cell-Derived Exosomes as Nanomedicine for Peripheral Nerve Injury

Peripheral nerve injury (PNI) is a complex and protracted process, and existing therapeutic approaches struggle to achieve effective nerve regeneration. Recent studies have shown that mesenchymal stem cells (MSCs) may be a pivotal choice for treating peripheral nerve injury. MSCs possess robust paracrine capabilities, and exosomes, as the primary secretome of MSCs, are considered crucial regulatory mediators involved in peripheral nerve regeneration. Exosomes, as nanocarriers, can transport various endogenous or exogenous bioactive substances to recipient cells, thereby promoting vascular and axonal regeneration while suppressing inflammation and pain. In this review, we summarize the mechanistic roles of exosomes derived from MSCs in peripheral nerve regeneration, discuss the engineering strategies for MSC-derived exosomes to improve therapeutic potential, and explore the combined effects of MSC-derived exosomes with biomaterials (nerve conduits, hydrogels) in peripheral nerve regeneration.

ADSC-Exos outperform BMSC-Exos in alleviating hydrostatic pressure-induced injury to retinal ganglion cells by upregulating nerve growth factors

BACKGROUND

Mesenchymal stem cells (MSCs) have protective effects on the cornea, lacrimal gland, retina, and photoreceptor cell damage, which may be mediated by exosomes (exos) released by MSCs.

AIM

To investigate the ameliorating effect of exos derived from different MSCs on retinal ganglion cell (RGC) injury induced by hydrostatic pressure.

METHODS

The RGC injury model was constructed by RGC damage under different hydrostatic pressures (40, 80, 120 mmHg). Then RGCs were cultured with adipose-derived stem cell (ADSC)-Exos and bone marrow-derived stem cell (BMSC)-Exos. Cell Counting Kit-8, transmission electron microscopy, flow cytometry, immunofluorescence, real-time quantitative polymerase chain reaction, and western blotting were performed to detect the ameliorating effect of exos on pressure-induced RGC injury.

RESULTS

ADSC-Exos and BMSC-Exos were successfully isolated and obtained. The gibbosity of RGCs was lower, the cells were irregularly ellipsoidal under pressure, and the addition of ADSC-Exos and BMSC-Exos significantly restored RGC morphology. Furthermore, the proliferative activity of RGCs was increased and the apoptosis of RGCs was inhibited. Moreover, the levels of lactate dehydrogenase and apoptosis-related proteins were increased, and the concentrations of antiapoptotic proteins and neurotrophic factors were decreased in damaged RGCs. However, the above indicators were significantly improved after ADSC-Exos and BMSC-Exos treatment.

CONCLUSION

These findings indicated that ADSC-Exos and BMSC-Exos could ameliorate RGC injury caused by hydrostatic pressure by inhibiting apoptosis and increasing the secretion of neurotrophic factors.

Adipose stem cells in tissue regeneration and repair: From bench to bedside

ADSCs are a large number of mesenchymal stem cells in Adipose tissue, which can be applied to tissue engineering. ADSCs have the potential of multi-directional differentiation, and can differentiate into bone tissue, cardiac tissue, urothelial cells, skin tissue, etc. Compared with other mesenchymal stem cells, ADSCs have a multitude of promising advantages, such as abundant number, accessibility in cell culture, stable function, and less immune rejection. There are two main methods to use ADSCs for tissue repair and regeneration. One is to implant the "ADSCs-scaffold composite" into the injured site to promote tissue regeneration. The other is cell-free therapy: using ADSC-exos or ADSC-CM alone to release a large number of miRNAs, cytokines and other bioactive substances to promote tissue regeneration. The tissue regeneration potential of ADSCs is regulated by a variety of cytokines, signaling molecules, and external environment. The differentiation of ADSCs into different tissues is also induced by growth factors, ions, hormones, scaffold materials, physical stimulation, and other factors. The specific mechanisms are complex, and most of the signaling pathways need to be further explored. This article reviews and summarizes the mechanism and clinical application of ADSCs in tissue injury repair so far, and puts forward further problems that need to be solved in this field, hoping to provide directions for further research in this field.

Emerging technologies for engineering of extracellular vesicles

Extracellular vesicles (EVs) are lipid-bilayer membrane-enclosed vesicles that are secreted by all cell types. Natural EVs contain biological information such as proteins, nucleic acids, and lipids from their parent cells. Therefore, EVs have been extensively studied as diagnostic biomarkers and therapeutic tools under normal and pathological conditions. However, some drawbacks, including low yield, poor therapeutic effects, lack of imaging, and targeting capacity of natural EVs, still need to be improved. Emerging engineering technologies have rendered EVs new properties or functionalities that broadened their applications in the biomedical field. Herein, in this review, we gave a brief overview of advanced strategies for EV engineering. We focused on pre-treatment of parent cells to regulate their released EVs. Meanwhile, we summarized and discussed the direct modification of EVs to achieve drug loading, imaging, and targeting functionalities for downstream applications.

Engineered exosomes for tissue regeneration: from biouptake, functionalization and biosafety to applications

Exosomes are increasingly recognized as important effector molecules that regulate intercellular signaling pathways. Notably, certain types of exosomes can induce therapeutic responses, including cell proliferation, angiogenesis, and tissue repair. The use of exosomes in therapy is a hot spot in current research, especially in regenerative medicine. Despite the therapeutic potential, problems have hindered their success in clinical applications. These shortcomings include low concentration, poor targeting and limited loading capability. To fully realize their therapeutic potential, certain modifications are needed in native exosomes. In the present review, we summarize the exosome modification and functionalization strategies. In addition, we provide an overview of potential clinical applications and highlight the issues associated with the biosafety and biocompatibility of engineered exosomes in applications.

LIPUS-SCs-Exo promotes peripheral nerve regeneration in cavernous nerve crush injury-induced ED rats via PI3K/Akt/FoxO signaling pathway

OBJECTIVE

Clinical treatment of erectile dysfunction (ED) caused by cavernous nerve (CN) injury during pelvic surgery is difficult. Low-intensity pulsed ultrasound (LIPUS) can be a potential strategy for neurogenic ED (NED). However, whether Schwann cells (SCs) can respond to LIPUS stimulation signals is unclear. This study aims to elucidate the signal transmission between SCs paracrine exosome (Exo) and neurons stimulated by LIPUS, as well as to analyze the role and potential mechanisms of exosomes in CN repair after injury.

METHODS

The major pelvic ganglion (MPG) neurons and MPG/CN explants were stimulated with LIPUS of different energy intensities to explore the appropriate LIPUS energy intensity. The exosomes were isolated and purified from LIPUS-stimulated SCs (LIPUS-SCs-Exo) and non-stimulated SCs (SCs-Exo). The effects of LIPUS-SCs-Exo on neurite outgrowth, erectile function, and cavernous penis histology were identified in bilateral cavernous nerve crush injury (BCNI)-induced ED rats.

RESULTS

LIPUS-SCs-Exo group can enhance the axon elongation of MPG/CN and MPG neurons compared to SCs-Exo group in vitro. Then, the LIPUS-SCs-Exo group showed a stronger ability to promote the injured CN regeneration and SCs proliferation compared to the SCs-Exo group in vivo. Furthermore, the LIPUS-SCs-Exo group increased the Max intracavernous pressure (ICP)/mean arterial pressure (MAP), lumen to parenchyma and smooth muscle to collagen ratios compared to the SCs-Exo group in vivo. Additionally, high-throughput sequencing combined with bioinformatics analysis revealed the differential expression of 1689 miRNAs between the SCs-Exo group and the LIPUS-SCs-Exo group. After LIPUS-SCs-Exo treatment, the phosphorylated levels of Phosphatidylinositol 3-kinase (PI3K), protein kinase B (Akt) and forkhead box O (FoxO) in MPG neurons increased significantly compared to negative control (NC) and SCs-Exo groups.

CONCLUSION

Our study revealed that LIPUS stimulation could regulate the gene of MPG neurons by changing miRNAs derived from SCs-Exo, then activating the PI3K-Akt-FoxO signal pathway to enhance nerve regeneration and restore erectile function. This study had important theoretical and practical significance for improving the NED treatment.

Engineering strategies and optimized delivery of exosomes for theranostic application in nerve tissue

Severe injuries or diseases affecting the peripheral and central nervous systems can result in impaired organ function and permanent paralysis. Conventional interventions, such as drug administration and cell-based therapy, exhibit limited effectiveness due to their inability to preserve post-implantation cell survival and impede the deterioration of adjacent tissues. Exosomes have recently emerged as powerful tools for tissue repair owing to their proteins and nucleic acids, as well as their unique phospholipid properties, which facilitate targeted delivery to recipient cells. Engineering exosomes, obtained by manipulating the parental cells or directly functionalizing exosomes, play critical roles in enhancing regenerative repair, reducing inflammation, and maintaining physiological homeostasis. Furthermore, exosomes have been shown to restore neurological function when used in combination with biomaterials. This paper primarily focuses on the engineering strategies and delivery routes of exosomes related to neural research and emphasizes the theranostic application of optimized exosomes in peripheral nerve, traumatic spinal cord, and brain injuries. Finally, the prospects of exosomes development and their combination with other approaches will be discussed to enhance our knowledge on their theranostic effectiveness in neurological diseases.

Potential application of let-7a antagomir in injured peripheral nerve regeneration

Neurotrophic factors, particularly nerve growth factor, enhance neuronal regeneration. However, the in vivo applications of nerve growth factor are largely limited by its intrinsic disadvantages, such as its short biological half-life, its contribution to pain response, and its inability to cross the blood-brain barrier. Considering that let-7 (human miRNA) targets and regulates nerve growth factor, and that let-7 is a core regulator in peripheral nerve regeneration, we evaluated the possibilities of let-7 application in nerve repair. In this study, anti-let-7a was identified as the most suitable let-7 family molecule by analyses of endogenous expression and regulatory relationship, and functional screening. Let-7a antagomir demonstrated biosafety based on the results of in vivo safety assessments and it entered into the main cell types of the sciatic nerve, including Schwann cells, fibroblasts and macrophages. Use of hydrogel effectively achieved controlled, localized, and sustained delivery of let-7a antagomir. Finally, let-7a antagomir was integrated into chitosan conduit to construct a chitosan-hydrogel scaffold tissue-engineered nerve graft, which promoted nerve regeneration and functional recovery in a rat model of sciatic nerve transection. Our study provides an experimental basis for potential in vivo application of let-7a.

Muscle-derived stem cell exosomes with overexpressed miR-214 promote the regeneration and repair of rat sciatic nerve after crush injury to activate the JAK2/STAT3 pathway by targeting PTEN

Introduction

This study aimed to investigate the effect of muscle-derived stem cell (MDSC) exosomes with overexpressed miR-214 on the regeneration and repair of rat sciatic nerve after crush injury and its molecular mechanism.

Methods

First, primary MDSCs, Schwann cells (SCs) and dorsal root ganglion (DRG) neurons were isolated and cultured, and the characteristics of MDSCs-derived exosomes were identified by molecular biology and immunohistochemistry. NC mimics and miR-214 mimics were transfected to obtain exo-NC and exo-miR-214. An in vitro co-culture system was established to determine the effect of exo-miR-214 on nerve regeneration. The restoration of sciatic nerve function of rats by exo-miR-214 was evaluated by walking track analysis. Immunofluorescence for NF and S100 was used to detect the regeneration of axon and myelin sheath in injured nerve. The Starbase database was used to analyze the downstream target genes of miR-214. QRT-PCR and dual luciferase reporter assays were used to validate the miR-214 and PTEN interaction relationship. And the expression of the JAK2/STAT3 pathway-related proteins in sciatic nerve tissues were detected by western blot.

Results

The above experiments showed that MDSCs-derived exosomes with overexpressed miR-214 was found to promote the proliferation and migration of SCs, increase the expression of neurotrophic factors, promote axon extension of DRG neurons and positively affect the recovery of nerve structure and function. In addition, PTEN was a target gene of miR-214. Exo-miR-214 can significantly inhibit the expression level of PTEN, increase the protein expression levels of p-JAK2 and p-STAT3 and the ratio of p-JAK2/JAK2 and p-STAT3/STAT3, also MDSCs-derived exosomes with overexpressed miR-214 can reduce the occurrence of denervated muscle atrophy.

Conclusion

In summary, the MDSCs-derived exosomes with overexpressed miR-214 is involved in peripheral nerve regeneration and repair in rats after sciatic nerve crush injury to activate the JAK2/ STAT3 pathway by targeting PTEN.

Engineered stem cell exosomes for oral and maxillofacial wound healing

Wound healing of the oral and maxillofacial area affects the quality of life and mental health of the patient; therefore, effective therapies are required to promote wound healing. However, traditional treatment methods have limited efficacy. Exosomes secreted by stem cells used for oral and maxillofacial wound healing have shown outstanding results. Stem cell-derived exosomes possess the regenerative and repair ability of stem cells. Moreover, they are nontumorigenic and have good biosafety. However, the application of natural stem cell exosomes is limited owing to their low yield, impurity, lack of targeting, and low drug delivery rate. Many modification methods have been developed to engineered stem cell exosomes with beneficial properties, such as modifying parent cells and directly processing stem cell exosomes. These methods include coincubation, genetic engineering, electroporation, ultrasound, and artificial synthesis of engineered stem cell exosomes. These engineered stem cell exosomes can cargo nucleic acids, proteins, and small molecules. This gives them anti-inflammatory and cell proliferation regulatory abilities and enables the targeted promotion of efficient soft tissue repair after trauma. Engineered stem cell exosomes can decrease inflammation, promote fibroblast proliferation, and angiogenesis, and decrease scar formation to promote oral and maxillofacial wound healing, including diabetic and burn wounds. Thus, engineered stem cell exosomes are an effective treatment that has the potential for oral and maxillofacial wound healing.