Fiber Density Modulates Cell Spreading in 3D Interstitial Matrix Mimetics

Cellular phenotype is heavily influenced by the extracellular matrix (ECM), a complex and tissue-specific three-dimensional structure with distinct biophysical and biochemical properties. As naturally derived cell culture platforms are difficult to controllably modulate, engineered synthetic ECMs have facilitated our understanding of how specific matrix properties direct cell behavior. However, synthetic approaches typically lack fibrous topography, a hallmark of stromal and interstitial ECMs in vivo. To construct tunable biomimetic models with physiologic microstructure, we developed a versatile approach to generate modular fibrous architectures in 3D. Photo-cross-linkable polymers were electrospun, photopatterned into desired lengths, and coencapsulated alongside cells within natural biopolymer, semisynthetic, and synthetic hydrogels. Cells encapsulated within fiber-reinforced hydrogel composites (FHCs) demonstrated accelerated spreading rates compared to in gels lacking such fibrous topography. Furthermore, increases in fiber density at constant bulk hydrogel elastic modulus produced morphologically distinct cell populations and modulated cellular mechanosensing in 3D, as evidenced by increased nuclear localization of the mechanosensitive transcription factor, Yes-associated protein (YAP). This work documents the impact of physical guidance cues in 3D and establishes a novel approach to generating more physiologic tissue- and disease-specific biomimetic models.