Study on the Mechanisms of Antifibrotic Action of Soluble Proteins of Human Mesenchymal Stromal Cell Secretome

Multipotent mesenchymal stromal cells (MSCs) are key regulators of tissue healing after injury. Acting in a paracrine manner, MSCs promote tissue regeneration and prevent the development of fibrosis, a pathological condition in which there is excessive replacement of functional tissue with scar tissue. However, the mechanisms of the antifibrotic action of proteins secreted by MSCs have not yet been established. The authors previously showed that the fraction of soluble protein factors (SF) of the MSC secretome is capable of suppressing the key cellular mechanism of fibrosis development, the differentiation of fibroblasts into myofibroblasts, and also established, using proteomic analysis, that this fraction is enriched in proteins capable of regulating the canonical signaling pathways of transforming growth factor beta, Wnt, and Notch in fibroblasts. This study investigated the effect of the SF fraction on these signaling pathways in human skin fibroblasts and found that this fraction suppresses the canonical Wnt signaling pathway in a model of myofibroblast differentiation of fibroblasts. According to the results of proteomic analysis, SF is enriched in the DKK3 protein, which is able to regulate fibroblast differentiation through interaction with components of the canonical Wnt signaling pathway. It was shown that depletion of DKK3 protein in the SF fraction of MSC secretome by immunoprecipitation results in a significant reduction in the ability of the SF fraction to suppress fibroblast differentiation into myofibroblasts in vitro. The obtained data clarify the mechanism of the antifibrotic action of MSC secretome proteins associated with the suppression of differentiation of fibroblasts into myofibroblasts.