Fatty Acid Fingerprints and Hyaluronic Acid in Extracellular Vesicles from Proliferating Human Fibroblast-like Synoviocytes

Abstract

Extracellular vesicles (EVs) function as conveyors of fatty acids (FAs) and other bioactive lipids and can modulate the gene expression and behavior of target cells. EV lipid composition influences the fluidity and stability of EV membranes and reflects the availability of lipid mediator precursors. Fibroblast-like synoviocytes (FLSs) secrete EVs that transport hyaluronic acid (HA). FLSs play a central role in inflammation, pannus formation, and cartilage degradation in joint diseases, and EVs have recently emerged as potential mediators of these effects. The aim of the present study was to follow temporal changes in HA and EV secretion by normal FLSs, and to characterize the FA profiles of FLSs and EVs during proliferation. The methods used included nanoparticle tracking analysis, confocal laser scanning microscopy, sandwich-type enzyme-linked sorbent assay, quantitative PCR, and gas chromatography. The expression of hyaluronan synthases 1–3 in FLSs and HA concentrations in conditioned media decreased during cell proliferation. This was associated with elevated proportions of 20:4n-6 and total n-6 polyunsaturated FAs (PUFAs) in high-density cells, reductions in n-3/n-6 PUFA ratios, and up-regulation of cluster of differentiation 44, tumor necrosis factor α, peroxisome proliferator-activated receptor (PPAR)-α, and PPAR-γ. Compared to the parent FLSs, 16:0, 18:0, and 18:1n-9 were enriched in the EV fraction. EV counts decreased during cell growth, and 18:2n-6 in EVs correlated with the cell count. To conclude, FLS proliferation was featured by increased 20:4n-6 proportions and reduced n-3/n-6 PUFA ratios, and FAs with a low degree of unsaturation were selectively transferred from FLSs into EVs. These FA modifications have the potential to affect membrane fluidity, biosynthesis of lipid mediators, and inflammatory processes in joints, and could eventually provide tools for translational studies to counteract cartilage degradation in inflammatory joint diseases.

Fatty acid fingerprints in bronchoalveolar lavage fluid and its extracellular vesicles reflect equine asthma severity

“…Due to vesicle interleaflet coupling by acyl chain digitation, an increase in outer leaflet sphingolipids having C20–24 acyl chains also necessitates an elevation in inner leaflet phosphatidylserine 18:0/18:1, thus, also increasing the need for C18 FAs 42 . In our study, the EVs were enriched with 18:1n-9, resembling the findings from earlier studies where MUFAs, especially 18:1, were elevated in the FA profile of EVs from human prostate cancer cells 43 and fibroblast-like synoviocytes 44 . Hough et al 1 also documented increased sphingomyelin species 34:1 (consisting of a 18:1 sphingoid base and 16:0 acyl chain) in BALF EVs of smoke-exposed asthmatic patients.…”

Musculoskeletal Development and Skeletal Pathophysiology’s

“…In addition to inflammatory mediators, synoviocytes also produce small extracellular vesicles (EV) that contain nucleic acids, proteins, lipids and metabolites. Mustonen et al show that human synovial fibroblasts produce EVs containing hyaluronic acid [ 5 ]. Moreover, they show that membrane fluidity, governed by the composition of fatty acids with the EV lipid bilayer, changes with cell proliferation in vitro that is accompanied by diminished EV and HA production [ 5 ].…”

“…Mustonen et al show that human synovial fibroblasts produce EVs containing hyaluronic acid [ 5 ]. Moreover, they show that membrane fluidity, governed by the composition of fatty acids with the EV lipid bilayer, changes with cell proliferation in vitro that is accompanied by diminished EV and HA production [ 5 ].…”