Abstract
BackgroundFibroblasts are the powerhouses responsible for the production and assembly of extracellular matrix (ECM). Their activity needs to be tightly controlled especially within the musculoskeletal system, where changes to ECM composition affect force transmission and mechanical loading that are required for effective movement of the body. Extracellular vesicles (EVs) are a mode of cell-cell communication within and between tissues, which has been largely characterised in cancer. However, it is unclear what the role of healthy fibroblast-derived EVs is during tissue homeostasis.MethodsHere, we performed proteomic analysis of small EVs derived from primary human muscle and tendon cells to identify the potential functions of healthy fibroblast-derived EVs.ResultsMass spectrometry-based proteomics revealed comprehensive profiles for small EVs released from healthy human fibroblasts from different tissues. We found that fibroblast-derived EVs were more similar than EVs from differentiating myoblasts, but there were significant differences between tendon fibroblast and muscle fibroblast EVs. Small EVs from tendon fibroblasts contained higher levels of proteins that support ECM synthesis, including TGFβ1, and muscle fibroblast EVs contained proteins that support myofiber function and components of the skeletal muscle matrix.ConclusionsOur data demonstrates a marked heterogeneity among healthy fibroblast-derived EVs, indicating shared tasks between EVs of skeletal muscle myoblasts and fibroblasts, whereas tendon fibroblast EVs could play a fibrotic role in human tendon tissue. These findings suggest an important role for EVs in tissue homeostasis of both tendon and skeletal muscle in humans.EueS9_TM9G2gnPvs8i76-XVideo abstract
Highlights
Fibroblasts are the powerhouses responsible for the production and assembly of extracellular matrix (ECM)
Small Extracellular vesicle (EV) isolated from conditioned media from tendon fibroblasts (TenX), differentiating myoblasts (MyoX) and muscle fibroblasts (FibX) were analysed by transmission electron microscopy (TEM)
EV preparations were digested with trypsin and the peptides were prepared for Liquid chromatography-mass spectrometry (LC-MS)
Summary
Fibroblasts are the powerhouses responsible for the production and assembly of extracellular matrix (ECM) Their activity needs to be tightly controlled especially within the musculoskeletal system, where changes to ECM composition affect force transmission and mechanical loading that are required for effective movement of the body. The two most studied subtypes of EVs are exosomes, which are 50–150 nm vesicles that are derived from the endosomal pathway and microvesicles (sometimes referred to as ectosomes), which are from 100 nm up to 1 μm in size and are formed by direct budding of the plasma membrane [1, 2] They have different routes to their formation there are no specific protein markers to differentiate them [2, 3]; Many marker proteins for exosomes are present in microvesicles [2], which include tetraspannins (e.g. CD81), heat shock proteins, components of the endosomal sorting complexes required for transport (ESCRT), integrins and regulators of intracellular trafficking (e.g. Ras-associated binding proteins, annexins and clathrins). How exosomes and other EVs from healthy fibroblasts regulate tissue homeostasis is unknown and the lack of biomarkers makes them difficult to study
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