Mitochondrial Transplantation Attenuates Neural Damage and Improves Locomotor Function After Traumatic Spinal Cord Injury in Rats

Mitochondrial transplantation: A promising therapy for mitochondrial disorders

As a vital energy source for cellular metabolism and tissue survival, the mitochondrion can undergo morphological or positional change and even shuttle between cells in response to various stimuli and energy demands. Multiple human diseases are originated from mitochondrial dysfunction, but the curative succusses by traditional treatments are limited. Mitochondrial transplantation therapy (MTT) is an innovative therapeutic approach that is to deliver the healthy mitochondria either derived from normal cells or reassembled through synthetic biology into the cells and tissues suffering from mitochondrial damages and finally replace their defective mitochondria and restore their function. MTT has already been under investigation in clinical trials for cardiac ischemia-reperfusion injury and given an encouraging performance in animal models of numerous fatal critical diseases including central nervous system disorders, cardiovascular diseases, inflammatory conditions, cancer, renal injury, and pulmonary damage. This review article summarizes the mechanisms and strategies of mitochondrial transfer and the MTT application for types of mitochondrial diseases, and discusses the potential challenge in MTT clinical application, aiming to exhibit the good therapeutic prospects of MTTs in clinics.

Mitochondria Transplantation Promotes Corneal Epithelial Wound Healing

Purpose

The integrity of the corneal epithelium is essential in maintaining normal corneal function. Conditions disrupting the corneal epithelial layer range from chemical burns to dry eye disease and may result in impairment of both corneal transparency and sensation. Identifying factors that regulate corneal wound healing is key for the development of new treatment strategies. Here, we investigated a direct role of mitochondria in corneal wound healing via mitochondria transplantation.

Methods

Human corneal epithelial cells (hCECs) were isolated from human corneas and incubated with mitochondria which were isolated from human ARPE-19 cells. We determined the effect of mitochondria transplantation on wound healing and proliferation of hCECs. In vivo, we used a mouse model of corneal chemical injury. Mitochondria were isolated from mouse livers and topically applied to the ocular surface following injury. We evaluated the time of wound repair, corneal re-epithelization, and stromal abnormalities.

Results

Mitochondria transplantation induced the proliferation and wound healing of primary hCECs. Further, mitochondria transplantation promoted wound healing in vivo. Specifically, mice receiving mitochondria recovered twice as fast as control mice following corneal injury, presenting both enhanced and improved repair. Corneas treated with mitochondria demonstrated the re-epithelization of the wound area to a multi-layer appearance, compared to thinning and complete loss of the epithelium in control mice. Mitochondria transplantation also prevented the thickening and disorganization of the corneal stromal lamella, restoring normal corneal dehydration.

Conclusions

Mitochondria promote corneal re-epithelization and wound healing. Augmentation of mitochondria levels via mitochondria transplantation may serve as an effective treatment for inducing the rapid repair of corneal epithelial defects.

Mitochondrial dysfunction: mechanisms and advances in therapy

Mitochondria, with their intricate networks of functions and information processing, are pivotal in both health regulation and disease progression. Particularly, mitochondrial dysfunctions are identified in many common pathologies, including cardiovascular diseases, neurodegeneration, metabolic syndrome, and cancer. However, the multifaceted nature and elusive phenotypic threshold of mitochondrial dysfunction complicate our understanding of their contributions to diseases. Nonetheless, these complexities do not prevent mitochondria from being among the most important therapeutic targets. In recent years, strategies targeting mitochondrial dysfunction have continuously emerged and transitioned to clinical trials. Advanced intervention such as using healthy mitochondria to replenish or replace damaged mitochondria, has shown promise in preclinical trials of various diseases. Mitochondrial components, including mtDNA, mitochondria-located microRNA, and associated proteins can be potential therapeutic agents to augment mitochondrial function in immunometabolic diseases and tissue injuries. Here, we review current knowledge of mitochondrial pathophysiology in concrete examples of common diseases. We also summarize current strategies to treat mitochondrial dysfunction from the perspective of dietary supplements and targeted therapies, as well as the clinical translational situation of related pharmacology agents. Finally, this review discusses the innovations and potential applications of mitochondrial transplantation as an advanced and promising treatment.

Skeletal muscle dysfunction in amyotrophic lateral sclerosis: a mitochondrial perspective and therapeutic approaches

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neuromuscular disease that results in the loss of motor neurons and severe skeletal muscle atrophy. The etiology of ALS is linked to skeletal muscle, which can activate a retrograde signaling cascade that destroys motor neurons. This is why satellite cells and mitochondria play a crucial role in the health and performance of skeletal muscles. This review presents current knowledge on the involvement of mitochondrial dysfunction, skeletal muscle atrophy, muscle satellite cells, and neuromuscular junction (NMJ) in ALS. It also discusses current therapeutic strategies, including exercise, drugs, stem cells, gene therapy, and the prospective use of mitochondrial transplantation as a viable therapeutic strategy.

Considerations for developing mitochondrial transplantation techniques for individualized medicine

Tweetable abstract Mitochondrial transplantation has been used to treat various diseases associated with mitochondrial dysfunction. Here, we highlight the considerations in quality control mechanisms that should be considered in the context of mitochondrial transplantation.

Therapeutic potential of mitochondrial transplantation in modulating immune responses post-cardiac arrest: a narrative review

BACKGROUND

Mitochondrial transplantation (MTx) has emerged as a novel therapeutic strategy, particularly effective in diseases characterized by mitochondrial dysfunction. This review synthesizes current knowledge on MTx, focusing on its role in modulating immune responses and explores its potential in treating post-cardiac arrest syndrome (PCAS).

METHODS

We conducted a comprehensive narrative review of animal and human studies that have investigated the effects of MTx in the context of immunomodulation. This included a review of the immune responses following critical condition such as ischemia reperfusion injury, the impact of MTx on these responses, and the therapeutic potential of MTx in various conditions.

RESULTS

Recent studies indicate that MTx can modulate complex immune responses and reduce ischemia-reperfusion injury post-CA, suggesting MTx as a novel, potentially more effective approach. The review highlights the role of MTx in immune modulation, its potential synergistic effects with existing treatments such as therapeutic hypothermia, and the need for further research to optimize its application in PCAS. The safety and efficacy of autologous versus allogeneic MTx, particularly in the context of immune reactions, are critical areas for future investigation.

CONCLUSION

MTx represents a promising frontier in the treatment of PCAS, offering a novel approach to modulate immune responses and restore cellular energetics. Future research should focus on long-term effects, combination therapies, and personalized medicine approaches to fully harness the potential of MTx in improving patient outcomes in PCAS.

Mitochondria in the Central Nervous System in Health and Disease: The Puzzle of the Therapeutic Potential of Mitochondrial Transplantation

Mitochondria, the energy suppliers of the cells, play a central role in a variety of cellular processes essential for survival or leading to cell death. Consequently, mitochondrial dysfunction is implicated in numerous general and CNS disorders. The clinical manifestations of mitochondrial dysfunction include metabolic disorders, dysfunction of the immune system, tumorigenesis, and neuronal and behavioral abnormalities. In this review, we focus on the mitochondrial role in the CNS, which has unique characteristics and is therefore highly dependent on the mitochondria. First, we review the role of mitochondria in neuronal development, synaptogenesis, plasticity, and behavior as well as their adaptation to the intricate connections between the different cell types in the brain. Then, we review the sparse knowledge of the mechanisms of exogenous mitochondrial uptake and describe attempts to determine their half-life and transplantation long-term effects on neuronal sprouting, cellular proteome, and behavior. We further discuss the potential of mitochondrial transplantation to serve as a tool to study the causal link between mitochondria and neuronal activity and behavior. Next, we describe mitochondrial transplantation's therapeutic potential in various CNS disorders. Finally, we discuss the basic and reverse-translation challenges of this approach that currently hinder the clinical use of mitochondrial transplantation.

Targeted transplantation of engineered mitochondrial compound promotes functional recovery after spinal cord injury by enhancing macrophage phagocytosis

Mitochondria are crucial in sustaining and orchestrating cellular functions. Capitalizing on this, we explored mitochondrial transplantation as an innovative therapeutic strategy for acute spinal cord injury (SCI). In our study, we developed an engineered mitochondrial compound tailored to target macrophages within the SCI region. Sourced from IL-10-induced Mertkhi bone marrow-derived macrophages, we conjugated a peptide sequence, cations-cysteine-alanine-glutamine-lysine (CAQK), with the mitochondria, optimizing its targeting affinity for the injury site. Our data demonstrated that these compounds significantly enhanced macrophage phagocytosis of myelin debris, curtailed lipid buildup, ameliorated mitochondrial dysfunction, and attenuated pro-inflammatory profiles in macrophages, both in vitro and in vivo. The intravenously delivered mitochondrial compounds targeted the SCI epicenter, with macrophages being the primary recipients. Critically, they promoted tissue regeneration and bolstered functional recovery in SCI mice. This study heralds a transformative approach to mitochondrial transplantation in SCI, spotlighting the modulation of macrophage activity, phagocytosis, and phenotype.

Mitochondria as secretory organelles and therapeutic cargos

Mitochondria have been primarily considered intracellular organelles that are responsible for generating energy for cell survival. However, accumulating evidence suggests that mitochondria are secreted into the extracellular space under physiological and pathological conditions, and these secreted mitochondria play diverse roles by regulating metabolism, the immune response, or the differentiation/maturation in target cells. Furthermore, increasing amount of research shows the therapeutic effects of local or systemic administration of mitochondria in various disease models. These findings have led to growing interest in exploring mitochondria as potential therapeutic agents. Here, we discuss the emerging roles of mitochondria as extracellularly secreted organelles to shed light on their functions beyond energy production. Additionally, we provide information on therapeutic outcomes of mitochondrial transplantation in animal models of diseases and an update on ongoing clinical trials, underscoring the potential of using mitochondria as a novel therapeutic intervention.

Mechanism Study of Polydatin in Treating Spinal Cord Injury by Modulating Mitochondrial Membrane Potential Based on Network Pharmacology and Molecular Docking

Spinal cord injury (SCI) is one of the most devastating central lesions, and mitochondrial function plays an important role in secondary injury after SCI. Polydatin (PD) is a natural glycosylated precursor of resveratrol, showing mitochondrial preservation effects in the central nervous system. This study aimed to identify the hub target genes of PD on mitochondrial membrane potential (MMP) in SCI. A comprehensive analysis was performed on SCI-related genes, MMP-related genes, and PD targets screening from public databases. Differential expression analysis was conducted to identify differentially expressed genes (DEGs) in SCI. Gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) were employed to assess pathway enrichment. Protein-protein interaction (PPI) network analysis and molecular docking were conducted to identify key genes and evaluate the binding affinity between PD and hub genes. A total of 16,958 SCI-related genes, 2,786 MMP-related genes, 318 PD-related target genes, and 7229 DEGs were identified. Intersection analysis revealed 46 genes common to all four categories. GSEA and GSVA analysis identified significant enrichment of pathways associated with suppressed and activated SCI biological processes. The PPI network analysis identified seven core hub genes: EGFR, SRC, VEGFA, STAT3, ERBB2, TP53, and RHOA. Molecular docking revealed strong binding affinities between PD and ERBB2, EGFR, and RHOA. The findings based on computational investigation from public databases suggest that PD may have therapeutic potential for SCI by modulating MMP. These results contribute to the understanding of SCI pathogenesis and the development of novel therapeutic strategies.

Research Progress of Antioxidants in Oxidative Stress Therapy after Spinal Cord Injury

Spinal cord injury (SCI) is a serious problem in the central nervous system resulting in high disability and mortality with complex pathophysiological mechanisms. Oxidative stress is one of the main secondary reactions of SCI, and its main pathophysiological marker is the production of excess reactive oxygen species. The overproduction of reactive oxygen species and insufficient antioxidant capacity lead to the occurrence of oxidative stress and neuroinflammation, and the dysregulation of oxidative stress and neuroinflammation leads to further aggravation of damage. Oxidative stress can initiate a variety of inflammatory and apoptotic pathways, and targeted antioxidant therapy can greatly reduce oxidative stress and reduce neuroinflammation, which has a certain positive effect on rehabilitation and prognosis in SCI. This article reviewed the research on different types of antioxidants and related treatments in SCI, focusing on the mechanisms of oxidative stress.

Characterizing the Impact of Compression Duration and Deformation-Related Loss of Closure Force on Clip-Induced Spinal Cord Injury in Rats

The clip-induced spinal cord injury (SCI) rat model is pivotal in preclinical SCI research. However, the literature exhibits variability in compression duration and limited attention to clip deformation-related loss of closure force. We aimed to investigate the impact of compression duration on SCI severity and the influence of clip deformation on closure force. Rats received T10-level clip-induced SCI with durations of 1, 5, 10, 20, and 30 s, and a separate group underwent T10 transection. Outcomes included functional, histological, electrophysiological assessments, and inflammatory cytokine analysis. A tactile pressure mapping system quantified clip closure force after open-close cycles. Our results showed a positive correlation between compression duration and the severity of functional, histological, and electrophysiological deficits. Remarkably, even a brief 1-s compression caused significant deficits comparable to moderate-to-severe SCI. SSEP waveforms were abolished with durations over 20 s. Decreased clip closure force appeared after five open-close cycles. This study offers critical insights into regulating SCI severity in rat models, aiding researchers. Understanding compression duration and clip fatigue is essential for experiment design and interpretation using the clip-induced SCI model.

Mitochondrial transplantation and transfer: The promising method for diseases

Mitochondria are organelles that serve as the powerhouses for cellular bioenergetics in eukaryotic cells. It is responsible for mitochondrial adenosine triphosphate (ATP) generation, cell signaling and activity, calcium balance, cell survival, proliferation, apoptosis, and autophagy. Mitochondrial transplantation is a promising disease therapy that involves the recovery of mitochondrial dysfunction using isolated functioning mitochondria. The objective of the present article is to provide current knowledge on natural mitochondrial transfer processes, in vitro and in vivo applications of mitochondrial transplantation, clinical trials, and challenges associated with mitochondrial transplantation.

Mitochondria as a therapeutic: a potential new frontier in driving the shift from tissue repair to regeneration

Fibrosis, or scar tissue development, is associated with numerous pathologies and is often considered a worst-case scenario in terms of wound healing or the implantation of a biomaterial. All that remains is a disorganized, densely packed and poorly vascularized bundle of connective tissue, which was once functional tissue. This creates a significant obstacle to the restoration of tissue function or integration with any biomaterial. Therefore, it is of paramount importance in tissue engineering and regenerative medicine to emphasize regeneration, the successful recovery of native tissue function, as opposed to repair, the replacement of the native tissue (often with scar tissue). A technique dubbed 'mitochondrial transplantation' is a burgeoning field of research that shows promise in in vitro, in vivo and various clinical applications in preventing cell death, reducing inflammation, restoring cell metabolism and proper oxidative balance, among other reported benefits. However, there is currently a lack of research regarding the potential for mitochondrial therapies within tissue engineering and regenerative biomaterials. Thus, this review explores these promising findings and outlines the potential for mitochondrial transplantation-based therapies as a new frontier of scientific research with respect to driving regeneration in wound healing and host-biomaterial interactions, the current successes of mitochondrial transplantation that warrant this potential and the critical questions and remaining obstacles that remain in the field.

Polymer-Functionalized Mitochondrial Transplantation to Fibroblasts Counteracts a Pro-Fibrotic Phenotype

Fibroblast-to-myofibroblast transition (FMT) leads to excessive extracellular matrix (ECM) deposition-a well-known hallmark of fibrotic disease. Transforming growth factor-β (TGF-β) is the primary cytokine driving FMT, and this phenotypic conversion is associated with mitochondrial dysfunction, notably a metabolic reprogramming towards enhanced glycolysis. The objective of this study was to examine whether the establishment of favorable metabolic phenotypes in TGF-β-stimulated fibroblasts could attenuate FMT. The hypothesis was that mitochondrial replenishment of TGF-β-stimulated fibroblasts would counteract a shift towards glycolytic metabolism, consequently offsetting pro-fibrotic processes. Isolated mitochondria, functionalized with a dextran and triphenylphosphonium (TPP) (Dex-TPP) polymer conjugate, were administered to fibroblasts (MRC-5 cells) stimulated with TGF-β, and effects on bioenergetics and fibrotic programming were subsequently examined. Results demonstrate that TGF-β stimulation of fibroblasts led to FMT, which was associated with enhanced glycolysis. Dex-TPP-coated mitochondria (Dex-TPP/Mt) delivery to TGF-β-stimulated fibroblasts abrogated a metabolic shift towards glycolysis and led to a reduction in reactive oxygen species (ROS) generation. Importantly, TGF-β-stimulated fibroblasts treated with Dex-TPP/Mt had lessened expression of FMT markers and ECM proteins, as well as reduced migration and proliferation. Findings highlight the potential of mitochondrial transfer, as well as other strategies involving functional reinforcement of mitochondria, as viable therapeutic modalities in fibrosis.

Different Ways to Die: Cell Death Pathways and Their Association With Spinal Cord Injury

Cell death is a systematic/nonsystematic process of cessation of normal morphology and functional properties of the cell to replace and recycle old cells with new also promoting inflammation in some cases. It is a complicated process comprising multiple pathways. Some are well-explored, and others have just begun to be. The research on appropriate control of cell death pathways after acute and chronic damage of neuronal cells is being widely researched today due to the lack of regeneration and recovering potential of a neuronal cell after sustaining damage and the inability to control the direction of neuronal growth. In the progression and onset of various neurological diseases, impairments in programmed cell death signaling processes, like necroptosis, apoptosis, ferroptosis, pyroptosis, and pathways directly or indirectly linked, like autophagy as in nonprogrammed necrosis, are observed. Spinal cord injury (SCI) involves the temporary or permanent disruption of motor activities due to the death of a neuronal and glial cell in the spinal cord accompanied by axonal degeneration. Recent years have seen a significant increase in research on the intricate biochemical interactions that occur after a SCI. Different cell death pathways may significantly impact the subsequent damage processes that lead to the eventual neurological deficiency after an injury to the spinal cord. A better knowledge of the molecular basis of the involved cell death pathways might help enhance neuronal and glial survival and neurological deficits, promoting a curative path for SCI.

The role of mitochondrial energy metabolism in neuroprotection and axonal regeneration after spinal cord injury

Mitochondrial dysfunction occurs in the early stage of axonal degeneration after spinal cord injury and involves oxidative stress, energy deficiency, imbalance of mitochondrial dynamics, etc., which play a key role in axonal degeneration and regeneration under physiological and pathological conditions. Failure of axonal regeneration can lead to long-term structural and functional damage. Several recent studies have shown that improved mitochondrial energy metabolism provides conditions for axonal regeneration and central nervous system repair. Here, we describe the role of mitochondrial energy metabolism in neuroprotection and axonal regeneration after spinal cord injury and review recent advances in targeted mitochondrial therapy.

Mitochondrial transplantation ameliorates hippocampal damage following status epilepticus

BACKGROUND

Hippocampal damage caused by status epilepticus (SE) can bring about cognitive decline and emotional disorders, which are common clinical comorbidities in patients with epilepsy. It is therefore imperative to develop a novel therapeutic strategy for protecting hippocampal damage after SE. Mitochondrial dysfunction is one of contributing factors in epilepsy. Given the therapeutic benefits of mitochondrial replenishment by exogenous mitochondria, we hypothesized that transplantation of mitochondria would be capable of ameliorating hippocampal damage following SE.

METHODS

Pilocarpine was used to induced SE in mice. SE-generated cognitive decline and emotional disorders were determined using novel object recognition, the tail suspension test, and the open field test. SE-induced hippocampal pathology was assessed by quantifying loss of neurons and activation of microglia and astrocytes. The metabolites underlying mitochondrial transplantation were determined using metabonomics.

RESULTS

The results showed that peripheral administration of isolated mitochondria could improve cognitive deficits and depressive and anxiety-like behaviors. Exogenous mitochondria blunted the production of reactive oxygen species, proliferation of microglia and astrocytes, and loss of neurons in the hippocampus. The metabonomic profiles showed that mitochondrial transplantation altered multiple metabolic pathways such as sphingolipid signaling pathway and carbon metabolism. Among potential affected metabolites, mitochondrial transplantation decreased levels of sphingolipid (d18:1/18:0) and methylmalonic acid, and elevated levels of D-fructose-1,6-bisphosphate.

CONCLUSION

To the best of our knowledge, these findings provide the first direct experimental evidence that artificial mitochondrial transplantation is capable of ameliorating hippocampal damage following SE. These new findings support mitochondrial transplantation as a promising therapeutic strategy for epilepsy-associated psychiatric and cognitive disorders.

Mitochondrial Transplantation in Mitochondrial Medicine: Current Challenges and Future Perspectives

Mitochondrial diseases (MDs) are inherited genetic conditions characterized by pathogenic mutations in nuclear DNA (nDNA) or mitochondrial DNA (mtDNA). Current therapies are still far from being fully effective and from covering the broad spectrum of mutations in mtDNA. For example, unlike heteroplasmic conditions, MDs caused by homoplasmic mtDNA mutations do not yet benefit from advances in molecular approaches. An attractive method of providing dysfunctional cells and/or tissues with healthy mitochondria is mitochondrial transplantation. In this review, we discuss what is known about intercellular transfer of mitochondria and the methods used to transfer mitochondria both in vitro and in vivo, and we provide an outlook on future therapeutic applications. Overall, the transfer of healthy mitochondria containing wild-type mtDNA copies could induce a heteroplasmic shift even when homoplasmic mtDNA variants are present, with the aim of attenuating or preventing the progression of pathological clinical phenotypes. In summary, mitochondrial transplantation is a challenging but potentially ground-breaking option for the treatment of various mitochondrial pathologies, although several questions remain to be addressed before its application in mitochondrial medicine.

Mitochondrial transplantation attenuates traumatic neuropathic pain, neuroinflammation, and apoptosis in rats with nerve root ligation

Traumatic neuropathic pain (TNP) is caused by traumatic damage to the somatosensory system and induces the presentation of allodynia and hyperalgesia. Mitochondrial dysfunction, neuroinflammation, and apoptosis are hallmarks in the pathogenesis of TNP. Recently, mitochondria-based therapy has emerged as a potential therapeutic intervention for diseases related to mitochondrial dysfunction. However, the therapeutic effectiveness of mitochondrial transplantation (MT) on TNP has rarely been investigated. Here, we validated the efficacy of MT in treating TNP. Both in vivo and in vitro TNP models by conducting an L5 spinal nerve ligation in rats and exposing the primary dorsal root ganglion (DRG) neurons to capsaicin, respectively, were applied in this study. The MT was operated by administrating 100 µg of soleus-derived allogeneic mitochondria into the ipsilateral L5 DRG in vivo and the culture medium in vitro. Results showed that the viable transplanted mitochondria migrated into the rats' spinal cord and sciatic nerve. MT alleviated the nerve ligation-induced mechanical and thermal pain hypersensitivity. The nerve ligation-induced glial activation and the expression of pro-inflammatory cytokines and apoptotic markers in the spinal cord were also repressed by MT. Consistently, exogenous mitochondria reversed the capsaicin-induced reduction of mitochondrial membrane potential and expression of pro-inflammatory cytokines and apoptotic markers in the primary DRG neurons in vitro. Our findings suggest that MT mitigates the spinal nerve ligation-induced apoptosis and neuroinflammation, potentially playing a role in providing neuroprotection against TNP.

Chronic stress-induced apoptosis is mitigated by young mitochondria transplantation in the prefrontal cortex of aged rats

Objectives

Apoptosis is common and often comorbid with aging and stress-related mood disorders. Evidence suggests that fresh mitochondria could reverse age-related dysfunctions in organs, especially in the brain. Therefore, this study investigated the effect of young mitochondria administration on the apoptosis process in the prefrontal cortex (PFC) of aged rats exposed to chronic stress.

Materials and Methods

Aged (22 months old) male rats were randomly assigned into four groups: aged control (AC), aged rats treated with young mitochondria (A+M), aged rats subjected to chronic stress for four weeks (A+St), and aged rats subjected to chronic stress and treated with young mitochondria (A+St+M). A+M and A+St+M groups received a single ICV injection (10 μl) of fresh mitochondria isolated from the brain of young rats for five minutes (2 µl/min). Finally, the levels of Malondialdehyde (MDA), Cytochrome c (Cyt c), Bax, Bcl-2, and Caspase-3 expression were investigated in the PFC.

Results

Young mitochondria administration reduced neuronal apoptosis in the PFC, associated with down-regulation of MDA, Bax, and Caspase-3 and up-regulation of Bcl-2. Moreover, fresh mitochondria partially improved the chronic stress-induced mitochondrial dysfunction in aged rats, as indicated by reduced cytochrome c (Cyt c) release from the mitochondria.

Conclusion

These results suggest mitotherapy could reverse cell viability and mitochondrial dysfunction-induced apoptosis in the PFC tissue of aged rats subjected to stressful stimuli.

A functionalized collagen-I scaffold delivers microRNA 21-loaded exosomes for spinal cord injury repair

MicroRNA (miRNA)-based therapies have shown great potential in the repair of spinal cord injury (SCI). MicroRNA 21 (miR21) has been proven to have an essential protective effect on SCI. However, there are some challenges for miRNAs application due to their easy degradation and ineffective cell penetration. As natural vesicles, exosomes were considered ideal carriers for miRNAs delivery for their advantages of low immunogenicity, inherent stability and tissue/cell penetration. However, poor targeting and the low capacity of specific miRNAs impede their practical applications. This study aims to develop a type of genetically engineered miR21-loaded exosomes that can be entrapped in collagen-I (Col-I) scaffold to repair SCI. The collagen-binding domain (CBD)-fused lysosome-associated membrane glycoprotein 2b (Lamp2b) protein (CBD-LP) and miR21 were overexpressed in host HEK293T (293T) cells that were used to produce engineered miR21-loaded exosomes. The CBD peptide fused in Lamp2b on the exosome surface can stably tether exosomes to Col-I scaffold, facilitate the retention of miR21-loaded exosomes in lesion sites, promote the sustained release of miR21 to cells. Finally, a functionalized Col-I scaffold biomaterial enriched with miR21-loaded exosomes was developed and it could benefit the repair of SCI. STATEMENT OF SIGNIFICANCE: MiRNA-based therapeutics have promising potential in spinal cord injury (SCI) repair. However, easy degradation and ineffective cell penetration impede miRNAs application. Exosomes are natural vehicles for miRNAs delivery but face the challenge of diffusion in vivo. Here, the collagen-binding domain (CBD)-fused Lamp2b and miR21 were overexpressed in HEK293T cells to produce miR21-loaded and CBD-modified exosomes (CBD-LP-miR21-EXOs). The CBD modified on the exosome surface can stably tether exosomes to collagen-I scaffold to form functionalized CBD-LP-miR21-EXO-Col scaffold that can facilitate the retention of miR21-loaded exosomes, promote the sustained release of miR21 to cells and finally benefit SCI repair. Furthermore, this type of functionalized collagen-I materials can be widely applied for other tissue injury repairs by enriching the CBD-LP-EXOs loaded with appropriate miRNAs.

The effect of metformin on ameliorating neurological function deficits and tissue damage in rats following spinal cord injury: A systematic review and network meta-analysis

Spinal cord injury (SCI) is a devastating condition with few treatment options. Metformin, a classical antidiabetic and antioxidant, has extended its application to experimental SCI treatment. Here, we performed a systematic review to evaluate the neurobiological roles of metformin for treating SCI in rats, and to assess the potential for clinical translation. PubMed, Embase, China National Knowledge Infrastructure, WanFang data, SinoMed, and Vip Journal Integration Platform databases were searched from their inception dates to October 2021. Two reviewers independently selected controlled studies evaluating the neurobiological roles of metformin in rats following SCI, extracted data, and assessed the quality of methodology and evidence. Pairwise meta-analyses, subgroup analyses and network analysis were performed to assess the roles of metformin in neurological function and tissue damage in SCI rats. Twelve articles were included in this systematic review. Most of them were of moderate-to-high methodological quality, while the quality of evidence from those studies was not high. Generally, Basso, Beattie, and Bresnahan scores were increased in rats treated with metformin compared with controls, and the weighted mean differences (WMDs) between metformin and control groups exhibited a gradual upward trend from the 3rd (nine studies, n = 164, WMD = 0.42, 95% CI = −0.01 to 0.85, P = 0.06) to the 28th day after treatment (nine studies, n = 136, WMD = 3.48, 95% CI = 2.04 to 4.92, P < 0.00001). Metformin intervention was associated with improved inclined plane scores, tissue preservation ratio and number of anterior horn motor neurons. Subgroup analyses indicated an association between neuroprotection and metformin dose. Network meta-analysis showed that 50 mg/kg metformin exhibited greater protection than 10 and 100 mg/kg metformin. The action mechanisms behind metformin were associated with activating adenosine monophosphate-activated protein kinase signaling, regulating mitochondrial function and relieving endoplasmic reticulum stress. Collectively, this review indicates that metformin has a protective effect on SCI with satisfactory safety and we demonstrate a rational mechanism of action; therefore, metformin is a promising candidate for future clinical trials. However, given the limitations of animal experimental methodological and evidence quality, the findings of this pre-clinical review should be interpreted with caution.