Biology subjects

Cassel, S. E.

Publications and source records attributed to Cassel, S. E..

2 recordsLinked to original sources

bioRxiv2026

Matrix stiffening toolbox: dynamic hydrogels for three-dimensional cell culture with real-time cell response

Extracellular matrix (ECM) mechanical properties regulate tissue homeostasis and disease progression, with persistent ECM stiffening serving as a hallmark of fibrosis; yet, the early transition from healthy to diseased tissue remains poorly understood. Dynamic three-dimensional (3D) tissue models that capture early-stage stiffening are needed to investigate cellular responses during disease initiation. This work presents an innovative platform for studying cell responses in 3D environments undergoing active matrix stiffening. A bioinspired synthetic ECM incorporates collagen-mimetic peptides and employs sequential, non-terminal strain-promoted azide-alkyne cycloaddition (SPAAC) reactions to enable controlled increases in matrix stiffness over physiologically relevant timescales. Alternating polymer incubations produce a 2.5-fold increase in storage modulus over 72 hours, modeling the mechanical transition from healthy to early-stage fibrotic lung tissue. Live-cell reporter fibroblasts enable real-time monitoring of alpha-smooth muscle actin (SMA) expression, revealing significant upregulation during matrix stiffening that remains transient and difficult to detect via traditional endpoint assays. Active stiffening also modulates fibroblast motility, transiently increasing migration speed while persistently enhancing directional persistence. Complementary computational reaction-diffusion modeling provides mechanistic insight into modulus gradient formation and reaction kinetics. This versatile toolbox enables investigation of early mechanobiological responses to matrix stiffening and may aid identification of markers of fibrotic disease onset.

bioengineering↗

bioRxiv2025

Probing Critical Injury Thresholds for Maladaptive Epithelial Injury and Repair Processes with Photoresponsive Bioinspired Synthetic Basement Membrane

Microinjuries to the lung epithelium are hypothesized to initiate maladaptive processes that lead to fibrosis. Human in vitro models remain a great need for studying this injury-initiation process for mechanistic understanding and therapeutic development. We established a photoresponsive synthetic extracellular matrix (ECM) inspired by the basement membrane that enables triggered injuries of defined size and frequency for probing cellular responses. The synthetic matrix integrated a photolabile bis-coumarin linker for light-triggered injury and relevant integrin-binding peptides for cell function. Bio-orthogonal chemistry was used to create hydrogel-based ECMs with tunable elasticity in transwells, which are traditionally used for epithelial cell culture. Integrin-binding peptide combinations synergistically promoted model epithelial cell layer formation with increased E-cadherin expression and barrier function. An accessible photomasking approach was established for selectively photodegrading the synthetic matrix with cytocompatible visible light and achieving different injury depths and widths. Following a critical injury size, cell responses recapitulated key features of dysregulated re-epithelialization with decreased E-cadherin, proliferation, and barrier function and increased apoptosis. This work provides a new materials-based tool for probing injury and repair processes with tunable control of both the ECM and injury to it with opportunities for future mechanistic and therapeutic insights to address maladaptive wound healing processes.

bioengineering↗