Thrombospondin-1 promotes fibro-adipogenic stromal expansion and contractile dysfunction of the diaphragm in obesity
Eric D. Buras, Moon-Sook Woo, Romil Kaul Verma, Sri Harshita Kondisetti, Carol S. Davis, Dennis R. Claflin, Kimber Converso-Baran, Daniel E. Michele, Susan V. Brooks, Tae-Hwa Chun
Eric D. Buras, Moon-Sook Woo, Romil Kaul Verma, Sri Harshita Kondisetti, Carol S. Davis, Dennis R. Claflin, Kimber Converso-Baran, Daniel E. Michele, Susan V. Brooks, Tae-Hwa Chun
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Research Article Metabolism Muscle biology

Thrombospondin-1 promotes fibro-adipogenic stromal expansion and contractile dysfunction of the diaphragm in obesity

Abstract

Pulmonary disorders affect 40%–80% of individuals with obesity. Respiratory muscle dysfunction is linked to these conditions; however, its pathophysiology remains largely undefined. Mice subjected to diet-induced obesity (DIO) develop diaphragm muscle weakness. Increased intradiaphragmatic adiposity and extracellular matrix (ECM) content correlate with reductions in contractile force. Thrombospondin-1 (THBS1) is an obesity-associated matricellular protein linked with muscular damage in genetic myopathies. THBS1 induces proliferation of fibro-adipogenic progenitors (FAPs) — mesenchymal cells that differentiate into adipocytes and fibroblasts. We hypothesized that THBS1 drives FAP-mediated diaphragm remodeling and contractile dysfunction in DIO. We tested this by comparing the effects of dietary challenge on diaphragms of wild-type (WT) and Thbs1-knockout (Thbs1–/–) mice. Bulk and single-cell transcriptomics demonstrated DIO-induced stromal expansion in WT diaphragms. Diaphragm FAPs displayed upregulation of ECM and TGF-β–related expression signatures and augmentation of a Thy1-expressing subpopulation previously linked to type 2 diabetes. Despite similar weight gain, Thbs1–/– mice were protected from these transcriptomic changes and from obesity-induced increases in diaphragm adiposity and ECM deposition. Unlike WT controls, Thbs1–/– diaphragms maintained normal contractile force and motion after DIO challenge. THBS1 is therefore a necessary mediator of diaphragm stromal remodeling and contractile dysfunction in overnutrition and a potential therapeutic target in obesity-associated respiratory dysfunction.

Authors

Eric D. Buras, Moon-Sook Woo, Romil Kaul Verma, Sri Harshita Kondisetti, Carol S. Davis, Dennis R. Claflin, Kimber Converso-Baran, Daniel E. Michele, Susan V. Brooks, Tae-Hwa Chun

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Figure 4

Whole tissue transcriptomics highlights enrichment of stromal genes in wild-type versus Thbs1–/– mice subjected to DIO.

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Whole tissue transcriptomics highlights enrichment of stromal genes in w...
(A) Volcano plot of whole costal diaphragm RNA-Seq demonstrating differentially expressed genes between wild-type (WT) and Thbs1–/– (KO) mice fed high-fat diet (HFD) for 6 months (6m HFD). n = 3 mice per group. X axis indicates log fold-change (FC) in KO versus WT. Y axis indicates –log adjusted P value. (B) Heatmap integrating tissue-level RNA-Seq with scRNA-Seq data. Genes indicated are those enriched in WT and KO mice on bulk RNA-Seq (i.e., the points on the volcano plot in A). Cell types are those identified on scRNA-Seq (as shown in Figure 1A). Heatmaps show cell type–specific expression as defined on scRNA-Seq. (C) Enrichment plots demonstrating selected HALLMARK pathways differentially expressed between 6m HFD-fed WT and KO mice: epithelial mesenchymal transition (Hallmark EMT) and inflammatory response (Hallmark Inflamm resp). Heatmaps show the expression of leading-edge genes in individual samples. (D) qPCR analysis of selected genes performed on costal diaphragm tissue of 6m HFD WT and 6m HFD KO mice. n = 3–8 whole hemidiaphragm samples per group. Statistical analysis with t test. Error bars indicate mean ± SD. *P < 0.05, **P < 0.01.