Downregulation of microRNA-21 contributes to decreased collagen expression in venous malformations via transforming growth factor-β/Smad3/microRNA-21 signaling feedback loop

Objective: Venous malformations (VMs) are the most frequent vascular malformations and are characterized by dilated and tortuous veins with a dysregulated vascular extracellular matrix. The purpose of the present study was to investigate the potential involvement of microRNA-21 (miR-21), a multifunctional microRNA tightly associated with extracellular matrix regulation, in the pathogenesis of VMs. Methods: The expression of miR-21, collagen I, III, and IV, transforming growth factor-beta (TGF-beta), and Smad3 (mothers against decapentaplegic homolog 3) was evaluated in VMs and normal skin tissue using in situ hybridization, immunohistochemistry, Masson trichrome staining, and real-time polymerase chain reaction. Human umbilical vein endothelial cells (HUVECs) were used to explore the underlying mechanisms. Results: miR-21 expression was markedly decreased in the VM specimens compared with normal skin, in parallel with downregulation of collagen I, III, and IV and the TGF-beta/Smad3 pathway in VMs. Moreover, our data demonstrated that miR21 positively regulated the expression of collagens in HUVECs and showed a positive association with the TGF-beta/Smad3 pathway in the VM tissues. In addition, miR-21 was found to mediate TGF-beta-induced upregulation of collagens in HUVECs. Our data have indicated that miR-21 and the TGF-beta/Smad3 pathway could form a positive feedback loop to synergistically regulate endothelial collagen synthesis. In addition, TGF-beta/Smad3/miR-21 feedback loop signaling was upregulated in bleomycin-treated HUVECs and VM specimens, which was accompanied by increased collagen deposition. Conclusions: To the best of our knowledge, the present study has, for the first time, revealed downregulation of miR-21 in VMs, which might contribute to decreased collagen expression via the TGF-beta/Smad3/miR-21 signaling feedback loop. These findings provide new information on the pathogenesis of VMs and might facilitate the development of new therapies for VMs.

Automated summary

This study revealed for the first time the downregulation of miR-21 in venous malformations (VMs), which may contribute to decreased collagen expression through the TGF-beta/Smad3/miR-21 signaling feedback loop. These findings provide new insights into the pathogenesis of VMs and may facilitate the development of new therapeutic approaches.