Single‐cell deconstruction of post‐sepsis skeletal muscle and adipose tissue microenvironments

Abstract

Background Persistent loss of skeletal muscle mass and function as well as altered fat metabolism are frequently observed in severe sepsis survivors. Studies examining sepsis-associated tissue dysfunction from the perspective of the tissue microenvironment are scarce. In this study, we comprehensively assessed transcriptional changes in muscle and fat at single-cell resolution following experimental sepsis induction. Methods Skeletal muscle and visceral white adipose tissue from control mice or mice 1 day or 1 month following faecal slurry-induced sepsis were used. Single cells were mechanically and enzymatically prepared from whole tissue, and viable cells were further isolated by fluorescence activated cell sorting. Droplet-based single-cell RNA-sequencing (scRNA-seq; 10× Genomics) was used to generate single-cell gene expression profiles of thousands of muscle and fat-resident cells. Bioinformatics analyses were performed to identify and compare individual cell populations in both tissues. Results In skeletal muscle, scRNA-seq analysis classified 1438 single cells into myocytes, endothelial cells, fibroblasts, mesenchymal stem cells, macrophages, neutrophils, T-cells, B-cells, and dendritic cells. In adipose tissue, scRNA-seq analysis classified 2281 single cells into adipose stem cells, preadipocytes, endothelial cells, fibroblasts, macrophages, dendritic cells, Bcells, T-cells, NK cells, and gamma delta T-cells. One day post-sepsis, the proportion of most non-immune cell populations was decreased, while immune cell populations, particularly neutrophils and macrophages, were highly enriched. Proportional changes of endothelial cells, neutrophils, and macrophages were validated using faecal slurry and cecal ligation and puncture models. At 1 month post-sepsis, we observed persistent enrichment/depletion of cell populations and further uncovered a cell-type and tissue-specific ability to return to a baseline transcriptomic state. Differential gene expression analyses revealed key genes and pathways altered in post-sepsis muscle and fat and highlighted the engagement of infection/inflammation and tissue damage signalling. Finally, regulator analysis identified gonadotropin-releasing hormone and Bay 11-7082 as targets/compounds that we show can reduce sepsis-associated loss of lean or fat mass. Conclusions These data demonstrate persistent post-sepsis muscle and adipose tissue disruption at the single-cell level and highlight opportunities to combat long-term post-sepsis tissue wasting using bioinformatics-guided therapeutic interventions.

The interplay of immunology and cachexia in infection and cancer

“…In a mouse model of peritonitis-induced sepsis with concomitant loss of adipose tissue and muscle mass, single-cell RNA sequencing analysis revealed that macrophage populations increase in muscles and decrease in adipose tissue 1 day after intraperitoneal injection of faecal slurry 76 . This was coupled with an increase in the levels of muscle-infiltrating neutrophils, natural killer cells and T cells that remained elevated in both the muscle and the adipose tissue 1 month after injection.…”

Lithium Chloride Protects against Sepsis-Induced Skeletal Muscle Atrophy and Cancer Cachexia

“…Inflammation-associated skeletal muscle wasting occurs in cancer cachexia and sepsis-induced skeletal muscle atrophy and significantly affects patient morbidity and mortality. Due to a lack of effective treatment options [ 54 , 55 ], this study aimed to investigate the potential of LiCl in treating inflammation-associated skeletal muscle wasting using in vitro and in vivo models of cancer cachexia and sepsis. We found that LiCl increased muscle mass, enhanced muscle strength, and increased fiber cross-sectional area.…”

Anticachectic regulator analysis reveals Perp-dependent antitumorigenic properties of 3-methyladenine in pancreatic cancer

“…These transcripts are associated with cancer-associated muscle wasting in humans (25)(26)(27), but like myofiber rounding, are not typically linked to murine cancer-associated muscle wasting (Figure 2D). We next performed validated pathway and regulator analyses (28)(29)(30)(31) and prioritized several candidate compounds predicted to reverse the aged muscle-specific atrophy signature (Figure 2E). 18 compounds were exclusively identified in the aged dataset (Figure 2F).…”