Pressure does not affect fibrotic function of dermal fibroblast through an in vitro 3D hydrogel culture model

Pressure therapy has been used for the prevention and treatment of hypertrophic scars for decades. However, the cellular and molecular mechanisms of this treatment modality have not been fully elaborated, leading to long-lasting controversies regarding its clinical effectiveness. In this current study, we adopted an in vitro 3D culture and compression model to explore the effect of pressure force on fibroblasts, in order to further explain the working mechanism of compression force during pressure treatment. Human dermal fibroblasts were cultured in the 3D culture hydrogel and treated with 1.5 atm of external compression force through a syringe tube device, for 4, 8, and 20 h respectively. RNA-seq identified 437 differentially regulated genes after an 8-h compression intervention compared with control cells, among which 256 genes were up-regulated and 181 genes were down-regulated. Further q-PCR analysis confirmed that early growth response 1(EGR1) and c-fos were down-regulated after an 8-h compression intervention. However, the down-regulation of EGR1 and c-fos at the mRNA level does not lead to altered protein synthesis through western blot, for both 8 and 20-h time points after pressure intervention. Genes closely related to the fibrotic function of fibroblasts including type I collagen (COL1), type III collagen (COL3), transforming growth factor β1(TGF-β1), matrix metallopeptidase 1 (MMP1), matrix metallopeptidase 1 (TIMP1), connective tissue growth factor (CTGF), α smooth muscle actin (α-SMA), and fibronectin 1 (FN1), were also unaffected after pressure treatment for 8 h. The current study indicated that in our 3D hydrogel culture model, pressure does not directly affect the fibrotic function of dermal fibroblast in vitro. Indirect regulation including reducing oedema, blood perfusion, and tension could be a more possible mechanism of pressure therapy.