FXTAS Neuropathology Includes Widespread Reactive Astrogliosis and White Matter Specific Astrocyte Degeneration

Advances on the Mechanisms and Therapeutic Strategies in Non-coding CGG Repeat Expansion Diseases

Non-coding CGG repeat expansions within the 5' untranslated region are implicated in a range of neurological disorders, including fragile X-associated tremor/ataxia syndrome, oculopharyngeal myopathy with leukodystrophy, and oculopharyngodistal myopathy. This review outlined the general characteristics of diseases associated with non-coding CGG repeat expansions, detailing their clinical manifestations and neuroimaging patterns, which often overlap and indicate shared pathophysiological traits. We summarized the underlying molecular mechanisms of these disorders, providing new insights into the roles that DNA, RNA, and toxic proteins play. Understanding these mechanisms is crucial for the development of targeted therapeutic strategies. These strategies include a range of approaches, such as antisense oligonucleotides, RNA interference, genomic DNA editing, small molecule interventions, and other treatments aimed at correcting the dysregulated processes inherent in these disorders. A deeper understanding of the shared mechanisms among non-coding CGG repeat expansion disorders may hold the potential to catalyze the development of innovative therapies, ultimately offering relief to individuals grappling with these debilitating neurological conditions.

Cell Sheets Formation Enhances Therapeutic Effects of Human Umbilical Cord Mesenchymal Stem Cells on Spinal Cord Injury

BACKGROUND

In recent years, the utilization of stem cell therapy and cell sheet technology has emerged as a promising approach for addressing spinal cord injury (SCI). However, the most appropriate cell type and mechanism of action remain unclear at this time. This study sought to develop an SCI rat model and evaluate the therapeutic effects of human umbilical cord mesenchymal stem cell (hUC-MSC) sheets in this model. Furthermore, the mechanisms underlying the vascular repair effect of hUC-MSC sheets following SCI were investigated.

METHODS

A temperature-responsive cell culture method was employed for the preparation of hUC-MSC sheets. The extracellular matrix (ECM) produced by hUC-MSCs serves two distinct yet interrelated purposes. Firstly, it acts as a biologically active scaffold for transplanted cells, facilitating their attachment and proliferation. Secondly, it provides mechanical support and bridges spinal cord stumps, thereby facilitating the restoration of spinal cord function. The formation of the cavity within the spinal cord was evaluated using the Hematoxylin and Eosin (H&E) staining method. Subsequently, endothelial cells were cultivated with the conditioned medium (CM) obtained from hUC-MSCs or hUC-MSC sheets. The pro-angiogenic impact of the conditioned medium of hUC-MSCs (MSC-CM) and the conditioned medium of hUC-MSC sheets (CS-CM) was evaluated through the utilization of the CCK-8 assay, endothelial wound healing assay, and tube formation assay in an in vitro context. The development of glial scars, blood vessels, neurons, and axons in hUC-MSCs and hUC-MSC sheets was assessed through immunofluorescence staining.

RESULTS

In comparison to hUC-MSCs, hUC-MSC sheets demonstrated a more pronounced capacity to facilitate vascular formation and induce the regeneration of newborn neurons at the SCI site, while also reducing glial scar formation and significantly enhancing motor function in SCI rats. Notably, under identical conditions, the formation of cell sheets has been associated with a paracrine increase in the ability of the cells themselves to secrete pro-angiogenic growth factors. During the course of the experiment, it was observed that the secretion of uPAR was the most pronounced among the pro-angiogenic factors present in MSC-CM and CS-CM. This finding was subsequently corroborated in subsequent experiments, wherein uPAR was demonstrated to promote angiogenesis via the PI3K/Akt signaling pathway.

CONCLUSION

The creation of cell sheets not only significantly enhances the biological function of hUC-MSCs but also effectively retains the cells locally in spinal cord injury. Therefore, the transplantation of hUC-MSC sheets can maximize the function of hUC-MSCs, greatly reducing glial scar formation, enhancing vascular formation, and promoting the regeneration of neurons and axons. Additionally, the research findings prove that hUC-MSC sheets activate the PI3K/Akt signaling pathway through uPAR secretion to enhance angiogenesis. The transfer of the entire extracellular matrix by hUC-MSC sheets, in the absence of the introduction of additional exogenous or synthetic biomaterials, serves to further augment their potential for clinical application.

Intersection of the fragile X-related disorders and the DNA damage response

The Repeat Expansion Diseases (REDs) are a large group of human genetic disorders that result from an increase in the number of repeats in a disease-specific tandem repeat or microsatellite. Emerging evidence suggests that the repeats trigger an error-prone form of DNA repair that causes the expansion mutation by exploiting a limitation in normal mismatch repair. Furthermore, while much remains to be understood about how the mutation causes pathology in different diseases in this group, there is evidence to suggest that some of the downstream consequences of repeat expansion trigger the DNA damage response in ways that contribute to disease pathology. This review will discuss these subjects in the context of the Fragile X-related disorders (aka the FMR1 disorders) that provide a particularly interesting example of the intersection between the repeats and the DNA damage response that may also be relevant for many other diseases in this group.

Role of fragile X messenger ribonucleoprotein 1 in the pathophysiology of brain disorders: a glia perspective

Fragile X messenger ribonucleoprotein 1 (FMRP) is a widely expressed RNA binding protein involved in several steps of mRNA metabolism. Mutations in the FMR1 gene encoding FMRP are responsible for fragile X syndrome (FXS), a leading genetic cause of intellectual disability and autism spectrum disorder, and fragile X-associated tremor-ataxia syndrome (FXTAS), a neurodegenerative disorder in aging men. Although FMRP is mainly expressed in neurons, it is also present in glial cells and its deficiency or altered expression can affect functions of glial cells with implications for the pathophysiology of brain disorders. The present review focuses on recent advances on the role of glial subtypes, astrocytes, oligodendrocytes and microglia, in the pathophysiology of FXS and FXTAS, and describes how the absence or reduced expression of FMRP in these cells can impact on glial and neuronal functions. We will also briefly address the role of FMRP in radial glial cells and its effects on neural development, and gliomas and will speculate on the role of glial FMRP in other brain disorders.