Myofibroblast activation in synthetic fibrous matrices composed of dextran vinyl sulfone

Mechanical interactions between fibroblasts and their surrounding extracellular matrix (ECM) guide fundamental behaviors such as spreading, migration, and proliferation that underlie disease pathogenesis. The challenges of studying ECM mechanics in vivo have motivated the development of in vitro models of the fibrous ECM in which fibroblasts reside. Natural materials such as collagen hydrogels bear structural and biochemical resemblance to stromal ECM, but mechanistic studies in these settings are often confounded by cell-mediated material degradation and the lack of structural and mechanical tunability. Here, we established a new material system composed of electrospun dextran vinyl sulfone (DexVS) polymeric fibers. These fibrous matrices exhibit mechanical tunability at both the single fiber (80-340 MPa) and bulk matrix (0.77-11.03 kPa) level, as well as long-term stability in mechanical properties over a two-week period. Cell adhesion to these matrices can be either user-defined by functionalizing synthetic fibers with thiolated adhesive peptides or methacrylated heparin to sequester cell-derived ECM proteins. We utilized DexVS fibrous matrices to investigate the role of matrix mechanics on the activation of fibroblasts into myofibroblasts, a key step of the fibrotic progression. In contrast to previous findings with non-fibrous hydrogel substrates, we find that fibroblasts in soft and deformable matrices exhibit increased spreading, focal adhesion formation, proliferation, and myofibroblast activation as compared to cells on stiffer matrices with equivalent starting architecture. STATEMENT OF SIGNIFICANCE: Cellular mechanosensing of fibrillar extracellular matrices plays a critical role in homeostasis and disease progression in stromal connective tissue. Here, we established a new material system composed of electrospun dextran vinyl sulfone polymeric fibers. These matrices exhibit architectural, mechanical, and biochemical tunability to accurately model diverse tissue microenvironments found in the body. In contrast to previous observations with non-fibrous hydrogels, we find that fibroblasts in soft and deformable fibrous matrices exhibit increased spreading and focal adhesion formation as compared to those in stiffer matrices with equivalent architecture. We also investigated the role of matrix stiffness on myofibroblast activation, a critical step in the fibrotic cascade, and find that low stiffness matrices promote increased myofibroblast activation.