Development and Validation of a Multiparametric Semiquantitative Scoring System for the Histopathological Assessment of Ischaemia Severity in Skeletal Muscle

Multitargeted biological actions of polydatin in preventing pseudogout acute attack

Introduction

We have recently shown that polydatin (PD) prevents calcium pyrophosphate (CPP) crystal-induced arthritis in mice. This study aims to explore potential mechanisms of action associated with this anti-inflammatory effect.

Materials and methods

Acute arthritis was induced in Balb/c mice by the injection of crystals into the ankle joint. Animals were randomised to receive PD or colchicine according to a prophylactic protocol. Ankle swelling was measured and both joints and muscles were harvested at sacrifice. Histological evaluations were performed using H&E staining to assess cartilage and muscle damage. Kondziela's inverted test was used to assess muscle strength. An exploratory protein array was performed on joint tissue to identify relevant inflammatory pathways. Human monocytes pretreated with PD were stimulated with CPP crystals. The use of specific inhibitors was instrumental in demonstrating their anti-inflammatory effects and assessing the role of SIRT1. The chemotaxis assay was performed to test the effect of PD and J-113863 on PBMCs migration in response to plasma and synovial fluids. Cytokine levels were measured by ELISA.

Results

CPP crystals injection resulted in swelling, leukocyte infiltration, loss of synovial membrane structure homogeneity. Mice pretreated with PD showed reduced ankle swelling and this was associated with very limited inflammatory damage. Regarding the effect on gastrocnemius muscle, crystals induced leukocyte infiltration and edema. PD and colchicine treatment reduced muscle damage and preserved musculoskeletal structure in mice. The cytokine array revealed the activation of various inflammatory pathways after CPP injection and PD was shown to influence leukocyte migration, angiogenesis and inflammation. In vitro, PD reduced inflammatory cytokines, chemokines and VEGF levels. CCR-1 inhibition was effective in reducing pro-inflammatory mediator levels in CPP treated monocytes and in reducing PBMCs migration. The anti-inflammatory action of PD also involved SIRT-1 activation, and its inhibition reverted the beneficial effects of PD. Finally, PD reduced the PBMCs migration in response to synovial fluids.

Conclusion

PD effectively prevents inflammatory responses to CPP crystals in mice, preserving both articular and muscular structures. Its anti-inflammatory effects are primarily mediated through pathways regulating leukocyte migration and the suppression of pro-inflammatory mediators.

miR-1, miR-133a, miR-29b and skeletal muscle fibrosis in chronic limb-threatening ischaemia

Chronic limb-threatening ischaemia (CLTI), the most severe manifestation of peripheral arterial disease (PAD), is associated with a poor prognosis and high amputation rates. Despite novel therapeutic approaches being investigated, no significant clinical benefits have been observed yet. Understanding the molecular pathways of skeletal muscle dysfunction in CLTI is crucial for designing successful treatments. This study aimed to identify miRNAs dysregulated in muscle biopsies from PAD cohorts. Using MIcroRNA ENrichment TURned NETwork (MIENTURNET) on a publicly accessible RNA-sequencing dataset of PAD cohorts, we identified a list of miRNAs that were over-represented among the upregulated differentially expressed genes (DEGs) in CLTI. Next, we validated the altered expression of these miRNAs and their targets in mice with hindlimb ischaemia (HLI). Our results showed a significant downregulation of miR-1, miR-133a, and miR-29b levels in the ischaemic limbs versus the contralateral non-ischaemic limb. A miRNA target protein-protein interaction network identified extracellular matrix components, including collagen-1a1, -3a1, and -4a1, fibronectin-1, fibrin-1, matrix metalloproteinase-2 and -14, and Sparc, which were upregulated in the ischaemic muscle of mice. This is the first study to identify miR-1, miR-133a, and miR-29b as potential contributors to fibrosis and vascular pathology in CLTI muscle, which supports their potential as novel therapeutic agents for this condition.

Mesenchymal stromal cell transplantation ameliorates fibrosis and microRNA dysregulation in skeletal muscle ischemia

Peripheral arterial disease (PAD) is associated with lower-extremity muscle wasting. Hallmark features of PAD-associated skeletal muscle pathology include loss of skeletal muscle mass, reduced strength and physical performance, increased inflammation, fibrosis, and adipocyte infiltration. At the molecular level, skeletal muscle ischemia has also been associated with gene and microRNA (miRNA) dysregulation. Mesenchymal stromal cells (MSCs) have been shown to enhance muscle regeneration and improve muscle function in various skeletal muscle injuries. This study aimed to evaluate the effects of intramuscularly delivered human umbilical cord-derived MSCs (hUC-MSCs) on skeletal muscle ischemia. Herein, we report an hUC-MSC-mediated amelioration of ischemia-induced skeletal muscle atrophy and function via enhancement of myofiber regeneration, reduction of tissue inflammation, adipocyte accumulation, and tissue fibrosis. These changes were observed in the absence of cell-mediated enhancement of blood flow recovery as measured by laser Doppler imaging. Furthermore, reduced tissue fibrosis in the hUC-MSC-treated group was associated with upregulation of miR-1, miR-133a, and miR-29b and downregulation of targeted pro-fibrotic genes such as Col1a1 and Fn1. Our results support the use of hUC-MSCs as a novel approach to reduce fibrosis and promote skeletal muscle regeneration after ischemic injury in patients with PAD.

Post mortem analysis of hepatic volume and lipid content by magnetic resonance imaging and spectroscopy in fixed murine neonates

Maternal obesity and hyperglycemia are linked to an elevated risk for obesity, diabetes, and steatotic liver disease in the adult offspring. To establish and validate a noninvasive workflow for perinatal metabolic phenotyping, fixed neonates of common mouse strains were analyzed postmortem via magnetic resonance imaging (MRI)/magnetic resonance spectroscopy (MRS) to assess liver volume and hepatic lipid (HL) content. The key advantage of nondestructive MRI/MRS analysis is the possibility of further tissue analyses, such as immunohistochemistry, RNA extraction, and even proteomics, maximizing the data that can be gained per individual and therefore facilitating comprehensive correlation analyses. This study employed an MRI and 1H-MRS workflow to measure liver volume and HL content in 65 paraformaldehyde-fixed murine neonates at 11.7 T. Liver volume was obtained using semiautomatic segmentation of MRI acquired by a RARE sequence with 0.5-mm slice thickness. HL content was measured by a STEAM sequence, applied with and without water suppression. T1 and T2 relaxation times of lipids and water were measured for respective correction of signal intensity. The HL content, given as CH2/(CH2 + H2O), was calculated, and the intrasession repeatability of the method was tested. The established workflow yielded robust results with a variation of ~3% in repeated measurements for HL content determination. HL content measurements were further validated by correlation analysis with biochemically assessed triglyceride contents (R2 = 0.795) that were measured in littermates. In addition, image quality also allowed quantification of subcutaneous adipose tissue and stomach diameter. The highest HL content was measured in C57Bl/6N (4.2%) and the largest liver volume and stomach diameter in CBA (53.1 mm3 and 6.73 mm) and NMRI (51.4 mm3 and 5.96 mm) neonates, which also had the most subcutaneous adipose tissue. The observed effects were independent of sex and litter size. In conclusion, we have successfully tested and validated a robust MRI/MRS workflow that allows assessment of morphology and HL content and further enables paraformaldehyde-fixed tissue-compatible subsequent analyses in murine neonates.