Mechanical cues in the tissue microenvironment can drive pathological activation of fibroblasts, a process increasingly implicated in inflammatory bowel disease (IBD). The authors used engineered shear platforms to test whether sustained fluid shear stress is sufficient to trigger a durable profibrotic transition in primary normal human intestinal fibroblasts. The stated objective was to compare responses across a microphysiological microfluidic gut-on-a-chip and a mesoscale rotary shear system to determine whether the trigger and resulting phenotypes are platform-dependent or governed by mechanical dose.
Two distinct shear delivery formats were employed: a microfluidic gut-on-a-chip microphysiological system and a mesofluidic rotary shaker. Primary normal human intestinal fibroblasts were derived from small and large intestine. Sustained fluid shear stress was applied, and cellular responses were assessed over time, with key observations reported within 72 hours. The study emphasizes that comparable outcomes across both systems support the concept that shear dose, rather than device geometry, dictates the observed fibroblast remodeling.
Across both platforms, normal intestinal fibroblasts reproducibly self-organized into three-dimensional (3D) multicellular aggregates within 72 hours of sustained shear exposure. This aggregation was observed for cells from both small and large intestine and occurred independently of the specific shear delivery format. The repeatable formation of aggregates under shear led investigators to interpret the response as a mechanoadaptive program that is initiated by mechanical dose.
The 3D aggregates acquired robust expression of α-smooth muscle actin (α-SMA) with aligned stress fibers, a phenotype that contrasted with the α-SMA–negative parental fibroblast population maintained outside of shear conditions. The induction of α-SMA and organized stress fibers indicates acquisition of a contractile, myofibroblast-like phenotype associated with profibrotic behavior. The authors report this transition as irreversible under the tested conditions, supporting the interpretation that sustained shear alone can enact a stable phenotypic switch.
Scanning electron microscopy (SEM) resolved a densely packed cellular microarchitecture within the shear-induced aggregates, embedded in a microfibrillar extracellular network. Complementary ultrastructural analysis using serial block-face three-dimensional electron microscopy revealed several distinctive features of the aggregates: expansive intercellular spaces, stochastic fibrillar extrusions projecting between cells, and electron-dense cytoplasmic material located at cell boundaries. These ultrastructural signatures provide morphological evidence of substantial extracellular matrix (ECM) remodeling and altered cell–cell or cell–matrix interfaces in the mechanoadaptive aggregates.
Proteomic profiling of the shear-induced aggregates confirmed enrichment of core matrisome components, including multiple collagen subtypes and matrix metalloproteinases (MMPs). The reported proteomic signature is consistent with an active ECM remodeling program that accompanies the α-SMA–positive, contractile phenotype. The detection of both structural matrix proteins (collagens) and matrix-remodeling enzymes (MMPs) supports a concerted program of matrix deposition and turnover as part of the mechanoadaptive fibroblast response to sustained shear.
Together, the structural, cytoskeletal, ultrastructural, and proteomic data indicate that sustained fluid shear stress functions as a platform-independent, sufficient mechanical trigger for a fibroblast-to-mechanoadaptive transition. Because this transition yields features characteristic of early fibrogenesis—3D aggregation, α-SMA induction, ECM remodeling enzymes, and altered ultrastructure—the authors position microphysiological shear platforms as tractable tools to model and potentially target early fibrotic processes in IBD. The cross-platform reproducibility suggests these systems could be useful for mechanistic studies and preclinical testing of anti-fibrotic interventions that target mechanically driven pathways.
The source describes key experimental observations and conclusions but does not provide detailed methodological parameters (for example, exact shear magnitudes, flow rates, or durations beyond the 72-hour aggregation timepoint) in the abstract. The authors declare no competing interests. Funding sources listed include NIH NCI IMAT, the Kenneth Rainin Foundation, Crohn's and Colitis Foundation awards, and multiple Korean funding agencies. These acknowledgements are reported in the source but no additional methodological or quantitative details were provided in the abstract.