Mesenchymal stem cells alleviate dexamethasone-induced muscle atrophy in mice and the involvement of ERK1/2 signalling pathway

Dexmedetomidine Attenuated Neuron Death, Cognitive Decline, and Anxiety-Like Behavior by Inhibiting CXCL2 in CA1 Region of AD Mice

Purpose

β-amyloid overload-induced neuroinflammation and neuronal loss are key pathological changes that occur during the progression of Alzheimer's disease (AD). Dexmedetomidine (Dex) exhibits neuroprotective and anti-inflammatory effects on the nervous system. However, the effect of Dex in AD mice remains unclear, and its neuroprotective regulatory mechanism requires further investigation. This study aimed to reveal how Dex protects against Aβ induced neuropathological changes and behavior dysfunction in AD mice.

Methods

An AD mouse model was established by the injection of Aβ into the brains of mice, followed by intraperitoneal injection with Dex. CXCL2 overexpression and Yohimbine, a Dex inhibitor, were used to investigate the role of Dex and CXCL2 in the regulation of neuronal loss, cognitive decline, and anxiety-like behavior in AD mice. Behavioral tests were performed to evaluate the cognitive and anxiety status of the mice. Nissl staining and immunofluorescence experiments were conducted to evaluate the status of the hippocampal neurons and astrocytes. qRT-PCR was performed to detect the expression of CXCL2, IL-1β, INOS, SPHK1, Bcl2, IFN-γ, and Caspase 1. The malondialdehyde (MDA) level was detected using an ELISA kit. Terminal TUNEL and Fluoro-Jade C (FJC) staining were used to measure the cell apoptosis rate.

Results

In AD mice, cognitive decline and anxiety-like behaviors were significantly improved by the Dex treatment. The number of neurons was increased in mice in the Dex + AD group compared to those in the AD group, and the number of astrocytes was not significantly different between the two groups. CXCL2, IL-1β, iNOS, and SPHK1 levels were significantly lower in Dex-treated AD mice than those in AD mice. Overloading of CXCL2 or Yohimbine reversed the protective effect of Dex on neuron number and cognitive and anxiety symptoms in AD mice.

Conclusion

Our results suggest that Dex exerts neuroprotective effects by downregulating CXCL2. Dex shows potential as a therapeutic drug for AD.

Human umbilical cord mesenchymal stem cell-derived exosomes ameliorate muscle atrophy via the miR-132-3p/FoxO3 axis

Background

Muscle atrophy or sarcopenia is the loss of muscle mass and strength and leads to an increased risk of disability and death including osteoporotic fractures. Currently, there are no available clinical biologic agents for the treatment of sarcopenia. Since exosomes have become increasingly attractive as a novel therapeutic approach due to their ability to facilitate cell-cell transfer of proteins and RNAs, promoting cell repair and function recovery, we hypothesized that human umbilical cord mesenchymal stem cell-derived exosomes (hucMSC-Exos) might benefit muscle atrophy in age-related and dexamethasone-induced sarcopenia animal models.

Methods

HucMSC-Exos were harvested by ultrafast centrifugation and identified by transmission electron microscopy, particle size analysis, and Western blot analysis. The effects of hucMSC-Exos on muscle atrophy were evaluated using age-related and dexamethasone-induced muscle atrophy mice models. Body weight, grip strength, muscle weight, and muscle histology of these mice were assessed. The expression levels of muscle RING finger 1 (MuRF1) and muscle atrophy F-box (atrogin-1) were measured by Western blot. Dexamethasone-induced C2C12 myotube atrophy was used to establish the cell model of muscle atrophy. Myotube diameter was evaluated by immunofluorescence staining. Bioinformatic analysis, RNA sequencing analysis, and Western blot analysis were performed to explore the underlying mechanisms.

Results

In vivo experiments, hucMSC-Exos demonstrated a remarkable capacity to improve grip strength, increase muscle mass, and muscle fiber cross-sectional area, while concurrently reducing the expression of MuRF1 and atrogin-1 in age-related and dexamethasone-induced muscle atrophy mice. In vitro experiments, hucMSC-Exos can promote the proliferation of C2C12 cells, and rescue the dexamethasone-induced decline in the viability of C2C12 myotubes. In addition, hucMSC-Exos can increase the diameter of C2C12 myotubes, and reduce dexamethasone-induced upregulation of MuRF1 and atrogin-1. Combined with bioinformatics analysis and RNA sequencing analysis, we further showed that miR-132-3p was one of the essential miRNAs in hucMSC-Exos and played an important role by targeting FoxO3.

Conclusion

Our findings suggested that hucMSC-Exos can improve age-related and dexamethasone-induced muscle atrophy in mice models. This study first demonstrated that hucMSC-Exos may ameliorate muscle atrophy via the miR-132-3p/FoxO3 axis. These data may provide novel and valuable insights into the clinical transformation of hucMSC-Exos for the treatment of sarcopenia.

The translational potential of this article

HucMSC-Exos are easily available for clinical application, this study further consolidates the evidence for the clinical transformation potential of hucMSC-Exos for sarcopenia and provides its new target pathway.

Pathogenesis of Sarcopenia in Chronic Kidney Disease-The Role of Inflammation, Metabolic Dysregulation, Gut Dysbiosis, and microRNA

Chronic kidney disease (CKD) is a progressive disorder associated with a decline in kidney function. Consequently, patients with advanced stages of CKD require renal replacement therapies, such as dialysis and kidney transplantation. Various conditions lead to the development of CKD, including diabetes mellitus, hypertension, and glomerulonephritis, among others. The disease is associated with metabolic and hormonal dysregulation, including uraemia and hyperparathyroidism, as well as with low-grade systemic inflammation. Altered homeostasis increases the risk of developing severe comorbidities, such as cardiovascular diseases or sarcopenia, which increase mortality. Sarcopenia is defined as a progressive decline in muscle mass and function. However, the precise mechanisms that link CKD and the development of sarcopenia are poorly understood. Knowledge about these linking mechanisms might lead to the introduction of precise treatment strategies that could prevent muscle wasting. This review discusses inflammatory mediators, metabolic and hormonal dysregulation, gut microbiota dysbiosis, and non-coding RNA alterations that could link CKD and sarcopenia.

Maternal docosahexaenoic acid supplementation during lactation improves exercise performance, enhances intestinal glucose absorption and modulates gut microbiota in weaning offspring mice

Introduction

Intestinal dysfunction induced by weaning stress is common during breastfeeding period. Docosahexaenoic acid (DHA) is well known for promoting visual and brain development, but its effects on early intestinal development remain unknown. This study investigated the impact of maternal DHA supplementation during lactation on intestinal glucose absorption and gut microbiota in weaning offspring mice.

Materials and methods

Dams were supplemented with vehicle (control), 150 mg/(kg body weight · day) DHA (L-DHA), or 450 mg/(kg body weight · day) DHA (H-DHA) throughout lactation by oral administration. After weaning, pups were randomly divided into three groups for athletic analysis, microbial and proteomic analysis, biochemical analysis, 4-deoxy-4-fluoro-D-glucose (4-FDG) absorption test, and gene expression quantitation of glucose transport-associated proteins and mTOR signaling components.

Results

The H-DHA group exhibited enhanced grip strength and prolonged swimming duration compared to the control group. Additionally, there were significant increases in jejunal and ileal villus height, and expanded surface area of jejunal villi in the H-DHA group. Microbial analyses revealed that maternal DHA intake increased the abundance of beneficial gut bacteria and promoted metabolic pathways linked to carbohydrate and energy metabolism. Proteomic studies indicated an increased abundance of nutrient transport proteins and enrichment of pathways involved in absorption and digestion in the H-DHA group. This group also showed higher concentrations of glucose in the jejunum and ileum, as well as elevated glycogen levels in the liver and muscles, in contrast to lower glucose levels in the intestinal contents and feces compared to the control group. The 4-FDG absorption test showed more efficient absorption after oral 4-FDG gavage in the H-DHA group. Moreover, the expressions of glucose transport-associated proteins, GLUT2 and SGLT1, and the activation of mTOR pathway were enhanced in the H-DHA group compared to the control group. The L-DHA group also showed similar but less pronounced improvements in these aspects relative to the H-DHA group.

Conclusion

Our findings suggested that maternal DHA supplementation during lactation improves the exercise performance, enhances the intestinal glucose absorption by increasing the expressions of glucose transporters, and beneficially alters the structure of gut microbiome in weaning offspring mice.

Considerations for enhanced mesenchymal stromal/stem cell myogenic commitment in vitro

The generation of tissue from stem cells is an alluring concept as it holds a number of potential applications in clinical therapeutics and regenerative medicine. Mesenchymal stromal/stem cells (MSCs) can be isolated from a number of different somatic sources, and have the capacity to differentiate into adipogenic, osteogenic, chondrogenic, and myogenic lineages. Although the first three have been extensively investigated, there remains a paucity of literature on the latter. This review looks at the various strategies available in vitro to enhance harvested MSC commitment and differentiation into the myogenic pathway. These include chemical inducers, myogenic-enhancing cell culture substrates, and mechanical and dynamic culturing conditions. Drawing on information from embryonic and postnatal myogenesis from somites, satellite, and myogenic progenitor cells, the mechanisms behind the chemical and mechanical induction strategies can be studied, and the sequential gene and signaling cascades can be used to monitor the progression of myogenic differentiation in the laboratory. Increased understanding of the stimuli and signaling mechanisms in the initial stages of MSC myogenic commitment will provide tools with which we can enhance their differentiation efficacy and advance the process to clinical translation.