Abstract
WNT signaling plays an important role in fibrotic processes in the heart. Recently, exosomes have been proposed as novel extracellular transporters for WNT proteins. In this study, we analyzed whether WNT3a and WNT5a carried by exosomes could activate downstream molecular pathways in human cardiac fibroblasts. Exosomes were isolated from conditioned medium of control, WNT3a- and WNT5a-producing L cells by differential ultracentrifugations. Obtained exosomes showed size ranging between 20–150 nm and expressed exosomal markers ALG-2-interacting protein X (ALIX) and CD63. Treatment with WNT3a-rich exosomes inhibited activity of glycogen synthase kinase 3β (GSK3β), induced nuclear translocation of β-catenin, and activated T-cell factor (TCF)/lymphoid enhancer factor (LEF) transcription factors as well as expression of WNT/β-catenin responsive genes in cardiac fibroblasts, but did not coactivate extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and activator protein 1 (AP-1) signaling pathways. In contrast, exosomes produced by WNT5a-producing L cells failed to activate β-catenin-dependent response, but successfully triggered phosphorylation of ERK1/2 and JNK and stimulated IL-6 production. In conclusion, exosomes containing WNT proteins can functionally contribute to cardiac fibrosis by activating profibrotic WNT pathways on cardiac fibroblasts and may represent a novel mechanism of spreading profibrotic signals in the heart.
Highlights
Cardiac fibroblasts represent a dominant population of stromal cells in the heart that maintain organ architecture and support its function
Characteristics of Exosome-Like Extracellular Vesicles Secreted by WNT3a- and WNT5a-Producing L Cells
In order to obtain exosomes containing WNT proteins, L-WNT3a, L-WNT5a, and control L cell lines were plated in the exosome-free medium and cultured for 48 h
Summary
Cardiac fibroblasts represent a dominant population of stromal cells in the heart that maintain organ architecture and support its function. During organogenesis and under homeostatic conditions cardiac fibroblasts control extracellular matrix (ECM) turnover by producing ECM components and proteolytic enzymes and their inhibitors [1]. In the injured or failing heart, cardiac fibroblasts play a key role in cardiac tissue remodeling, which often results in fibrotic changes. Activation of cardiac fibroblasts promotes excessive accumulation of stromal cells and ECM proteins in the myocardium. Various signaling molecules or mechanical stress activate cardiac fibroblasts for uncontrolled proliferation and ECM overproduction. Proteins of the WNT family have been implicated in the activation of cardiac fibroblasts in the number of fibrotic cardiac pathologies [2,3,4]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call