Effects of Different Doses of Mesenchymal Stem Cells on Functional Recovery After Compressive Spinal-Cord Injury in Mice

Brain-derived neurotrophic factor (BDNF) as biomarker in stem cell-based therapies of preclinical spinal cord injury models: A systematic review

Stem cell-based therapies offer promising treatment for spinal cord injury (SCI) by reducing inflammation, restoring plasticity, and supporting neuroprotection and nerve regeneration. Brain-derived neurotrophic factor (BDNF) is crucial in SCI pathophysiology. This study reviews the impact of stem cells on BDNF expression in preclinical SCI models. A thorough search was performed in PubMed, Scopus, and Web of Science until June 2023, identifying studies on the effects of stem cells on BDNF in SCI. Two researchers reviewed and extracted data from relevant studies. This review is registered in the Prospective Register of Systematic Reviews (PROSPERO) with the registration number [CRD42023441466]. Out of 923 records, 51 studies met the inclusion criteria, involving rats (46 studies) and mice (5 studies). The contusion or compression model was used in 40 studies, and the transection model in 11. The most common stem cell types were bone marrow mesenchymal stem cells (BM-MSCs), neural stem cells (NSCs), and adipose-derived stem cells (ADSCs). BM-MSCs increased BDNF expression in 16 studies, NSCs in 9 studies, and ADSCs in only one study. This review highlights that BM-MSCs and NSCs are effective in enhancing BDNF expression in preclinical SCI models, while other stem cell types may not significantly affect BDNF levels. These findings suggest variability in the effectiveness of different stem cell therapies in modulating BDNF production for SCI treatment.

Traumatic brain Injury: Comprehensive overview from pathophysiology to Mesenchymal stem Cell-Based therapies

Traumatic brain injury (TBI) is a disastrous phenomenon which is considered to cause high mortality and morbidity rate. Regarding the importance of TBI due to its prevalence and its effects on the brain and other organs, finding new therapeutic methods and improvement of conventional therapies seems to be vital. TBI involves a complex physiological mechanism, with inflammation being a key component among various contributing factors. After incidence of TBI, inflammation can act as a double-edged sword in the process. Inflammation actually plays its role both as initiator and progressive index during TBI which can accumulate myeloid and lymphoid immune cells and trigger cell death pathways. Through this study we made this concept bold that that besides conventional therapies that could be used for traumatic brain injury, treatments based on mesenchyme stem cells (MSCs) and their derivatives including secretomes and exosomes demonstrate more efficacies particularly in preventing secondary injuries caused by TBI. Of note, we highlighted the valuable features of MSC-based therapies such as self-direction toward inflamed tissues and amplifying neuro-regenerative aspects. We listed possible challenges in the way of reaching this therapy to clinic to provide a clear and updated of the field.

Inosine Improves Functional Recovery and Cell Morphology Following Compressive Spinal Cord Injury in Mice

Spinal cord injury (SCI) is one of the most serious conditions of the central nervous system, causing motor and sensory deficits that lead to a significant impairment in the quality of life. Previous studies have indicated that inosine can promote regeneration after SCI. Here we investigated the effects of inosine on the behavioral and morphological recovery after a compressive injury. Adult female C57BL/6 mice were subjected to laminectomy and spinal cord compression using a vascular clip. Inosine or saline injections were administered intraperitoneally, with the first dose performed 24 h after injury and daily for 7 days after injury. The mice were evaluated using Basso Mouse Scale (BMS), locomotor rating scale, and pinprick test for 8 weeks. At the end, the animals were anesthetized and euthanized, and the spinal cords were collected for morphological evaluation. Inosine-treated animals presented better results in the immunostaining for oligodendrocytes and in the number of myelinated fibers through semithin sections compared to saline-treated animals, showing that there was a greater preservation of the white matter. Analysis of the immunoreactivity of astrocytes and evaluation of the inflammatory profile with macrophage labeling revealed that the animals of the inosine group had a lower immunoreactivity when compared to control, which suggests a reduction of the glial scar and less inflammation, respectively, leading to a more favorable microenvironment for spinal cord regeneration. Indeed, inosine-treated animals scored higher on the BMS scale and presented better results on the pinprick test, indicating that the treatment contributed to motor and sensory recovery. After the animals were sacrificed, we obtained the electroneuromyography, where the inosine group showed a greater amplitude of the compound muscle action potential. These results indicate that inosine contributed to the regeneration process in the spinal cord of mice submitted to compressive injury and should be further investigated as a candidate for SCI therapy.

MSC-Based Cell Therapy in Neurological Diseases: A Concise Review of the Literature in Pre-Clinical and Clinical Research

Mesenchymal stem cells (MSCs) are multipotent stromal cells with the ability to self-renew and multi-directional differentiation potential. Exogenously administered MSCs can migrate to damaged tissue sites and participate in the repair of damaged tissues. A large number of pre-clinical studies and clinical trials have demonstrated that MSCs have the potential to treat the abnormalities of congenital nervous system and neurodegenerative diseases. Therefore, MSCs hold great promise in the treatment of neurological diseases. Here, we summarize and highlight current progress in the understanding of the underlying mechanisms and strategies of MSC application in neurological diseases.

The role and mechanisms of mesenchymal stem cells regulating macrophage plasticity in spinal cord injury

Spinal Cord Injury (SCI) is a devastating neurological disorder comprising primary mechanical injury and secondary inflammatory response-mediated injury for which an effective treatment is still unavailable. It is well known that secondary inflammatory responses are a significant cause of difficulties in neurological recovery. An immune imbalance between M1/M2 macrophages at the sites of injury is involved in developing and progressing the secondary inflammatory response. Recently, Mesenchymal Stem Cells (MSCs) have shown significant therapeutic potential in tissue engineering and regenerative medicine due to their potential multidirectional differentiation and immunomodulatory properties. Accumulating evidence shows that MSCs can regulate the balance of M1/M2 macrophage polarization, suppress downstream inflammatory responses, facilitate tissue repair and regeneration, and improve the prognosis of SCI. This article briefly overviews the impact of macrophages and MSCs on SCI and repair. It discusses the mechanisms by which MSCs regulate macrophage plasticity, including paracrine action, release of exosomes and apoptotic bodies, and metabolic reprogramming. Additionally, the article summarizes the relevant signaling pathways of MSCs that regulate macrophage polarization.

Mesenchymal Stem Cell Therapy: A Potential Treatment Targeting Pathological Manifestations of Traumatic Brain Injury

Traumatic brain injury (TBI) makes up a large proportion of acute brain injuries and is a major cause of disability globally. Its complicated etiology and pathogenesis mainly include primary injury and secondary injury over time, which can cause cognitive deficits, physical disabilities, mood changes, and impaired verbal communication. Recently, mesenchymal stromal cell- (MSC-) based therapy has shown significant therapeutic potential to target TBI-induced pathological processes, such as oxidative stress, neuroinflammation, apoptosis, and mitochondrial dysfunction. In this review, we discuss the main pathological processes of TBI and summarize the underlying mechanisms of MSC-based TBI treatment. We also discuss research progress in the field of MSC therapy in TBI as well as major shortcomings and the great potential shown.

Current Status of Mesenchymal Stem/Stromal Cells for Treatment of Neurological Diseases

Neurological disorders include a wide spectrum of clinical conditions affecting the central and peripheral nervous systems. For these conditions, which affect hundreds of millions of people worldwide, generally limited or no treatments are available, and cell-based therapies have been intensively investigated in preclinical and clinical studies. Among the available cell types, mesenchymal stem/stromal cells (MSCs) have been widely studied but as yet no cell-based treatment exists for neurological disease. We review current knowledge of the therapeutic potential of MSC-based therapies for neurological diseases, as well as possible mechanisms of action that may be explored to hasten the development of new and effective treatments. We also discuss the challenges for culture conditions, quality control, and the development of potency tests, aiming to generate more efficient cell therapy products for neurological disorders.

Dose optimization of intrathecal administration of human umbilical cord mesenchymal stem cells for the treatment of subacute incomplete spinal cord injury

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are a promising candidate for spinal cord injury (SCI) repair owing to their advantages of low immunogenicity and easy accessibility over other MSC sources. However, modest clinical efficacy hampered the progression of these cells to clinical translation. This discrepancy may be due to many variables, such as cell source, timing of implantation, route of administration, and relevant efficacious cell dose, which are critical factors that affect the efficacy of treatment of patients with SCI. Previously, we have evaluated the safety and efficacy of 4 × 10⁶ hUC-MSCs/kg in the treatment of subacute SCI by intrathecal implantation in rat models. To search for a more accurate dose range for clinical translation, we compared the effects of three different doses of hUC-MSCs – low (0.25 × 10⁶ cells/kg), medium (1 × 10⁶ cells/kg) and high (4 × 10⁶ cells/kg) – on subacute SCI repair through an elaborate combination of behavioral analyses, anatomical analyses, magnetic resonance imaging-diffusion tensor imaging (MRI-DTI), biotinylated dextran amine (BDA) tracing, electrophysiology, and quantification of mRNA levels of ion channels and neurotransmitter receptors. Our study demonstrated that the medium dose, but not the low dose, is as efficient as the high dose in producing the desired therapeutic outcomes. Furthermore, partial restoration of the γ-aminobutyric acid type A (GABA_A) receptor expression by the effective doses indicates that GABA_A receptors are possible candidates for therapeutic targeting of dormant relay pathways in injured spinal cord. Overall, this study revealed that intrathecal implantation of 1 × 10⁶ hUC-MSCs/kg is an alternative approach for treating subacute SCI.

Extracellular Vesicles in the Pathogenesis, Treatment, and Diagnosis of Spinal Cord Injury: A Mini-Review

BACKGROUND

Benefiting from in-depth research into stem cells, extracellular vesicles (EVs), which are byproducts of cells and membrane-wrapped microvesicles (30-120 nm) containing lipids, proteins, and nucleic acids, may cast light on the research and development of therapeutics capable of improving the neurological recovery of spinal cord injury (SCI) animals. However, the mechanistic modes of action for EVs in alleviating the lesion size of SCI remain to be solved, thus presenting a tremendous gap existing in translation from the laboratory to the clinic.

OBJECTIVE

The purpose of this minireview was to cover a wide range of basic views on EVs involved in SCI treatment, including the effects of EVs on the pathogenesis, treatment, and diagnosis of spinal cord injury.

METHODS

We searched databases (i.e., PubMed, Web of Science, Scopus, Medline, and EMBASE) and acquired all accessible articles published in the English language within five years. Studies reporting laboratory applications of EVs in the treatment of SCI were included and screened to include studies presenting relevant molecular mechanisms.

RESULTS

This review first summarized the basic role of EVs in cell communication, cell death, inflammatory cascades, scar formation, neuronal regrowth, and angiogenesis after SCI, thereby providing insights into neuroprotection and consolidated theories for future clinical application of EVs.

CONCLUSION

EVs participate in an extremely wide range of cell activities, play a critical role in cell communication centring neurons, and are considered potential therapies and biomarkers for SCI. miRNAs are the most abundant nucleic acids shipped by EVs and effluent cytokines, and they may represent important messengers of EVs and important factors in SCI treatment.

Future Perspectives in Spinal Cord Repair: Brain as Saviour? TSCI with Concurrent TBI: Pathophysiological Interaction and Impact on MSC Treatment

Traumatic spinal cord injury (TSCI), commonly caused by high energy trauma in young active patients, is frequently accompanied by traumatic brain injury (TBI). Although combined trauma results in inferior clinical outcomes and a higher mortality rate, the understanding of the pathophysiological interaction of co-occurring TSCI and TBI remains limited. This review provides a detailed overview of the local and systemic alterations due to TSCI and TBI, which severely affect the autonomic and sensory nervous system, immune response, the blood-brain and spinal cord barrier, local perfusion, endocrine homeostasis, posttraumatic metabolism, and circadian rhythm. Because currently developed mesenchymal stem cell (MSC)-based therapeutic strategies for TSCI provide only mild benefit, this review raises awareness of the impact of TSCI-TBI interaction on TSCI pathophysiology and MSC treatment. Therefore, we propose that unravelling the underlying pathophysiology of TSCI with concomitant TBI will reveal promising pharmacological targets and therapeutic strategies for regenerative therapies, further improving MSC therapy.

Axon Degeneration Is Rescued with Human Umbilical Cord Perivascular Cells: A Potential Candidate for Neuroprotection After Traumatic Brain Injury

Traumatic brain injury (TBI) leads to delayed secondary injury events consisting of cellular and molecular cascades that exacerbate the initial injury. Human umbilical cord perivascular cells (HUCPVCs) secrete neurotrophic and prosurvival factors. In this study, we examined the effects of HUCPVC in sympathetic axon and cortical axon survival models and sought to determine whether HUCPVC provide axonal survival cues. We then examined the effects of the HUCPVC in an in vivo fluid percussion injury model of TBI. Our data indicate that HUCPVCs express neurotrophic and neural survival factors. They also express and secrete relevant growth and survival proteins when cultured alone, or in the presence of injured axons. Coculture experiments indicate that HUCPVCs interact preferentially with axons when cocultured with sympathetic neurons and reduce axonal degeneration. Nerve growth factor withdrawal in axonal compartments resulted in 66 ± 3% axon degeneration, whereas HUCPVC coculture rescued axon degeneration to 35 ± 3%. Inhibition of Akt (LY294002) resulted in a significant increase in degeneration compared with HUCPVC cocultures (48 ± 7% degeneration). Under normoxic conditions, control cultures showed 39 ± 5% degeneration. Oxygen glucose deprivation (OGD) resulted in 58 ± 3% degeneration and OGD HUCPVC cocultures reduced degeneration to 34 ± 5% (p < 0.05). In an in vivo model of TBI, immunohistochemical analysis of NF200 showed improved axon morphology in HUCPVC-treated animals compared with injured animals. These data presented in this study indicate an important role for perivascular cells in protecting axons from injury and a potential cell-based therapy to treat secondary injury after TBI.