The mechanical milieu in which cells reside plays a crucial role in regulating their physiological behavior. Native tissue matrices exhibit complex mechanical properties, including viscoelasticity and nonlinear elasticity, which are essential not only for maintaining cellular health but also for directing differentiation and repair. However, aging and disease progressively degrade these mechanical characteristics, contributing to tissue dysfunction and pathologies such as neurodegeneration and cancer. Despite the recognized importance of mechanical cues, prior biomaterial platforms have largely failed to replicate the intricate viscoelastic and nonlinear elastic behavior of living tissues simultaneously, limiting our capacity to interrogate and manipulate cell mechanobiology effectively.

Addressing this critical gap, Professor Yiwei Li and Professor Bi-Feng Liu’s team have engineered an interpenetrating network (IPN) hydrogel composed of alginate and collagen, designed meticulously to mimic the native mechanical environment of soft tissues. This composite hydrogel synergizes collagen’s nonlinear elasticity with alginate’s viscoelastic shear-thinning properties, thereby creating a matrix that faithfully recapitulates the dual mechanical nature of biological tissues. The researchers demonstrated the ability to fine-tune the hydrogel’s initial stiffness via calcium ion crosslinking adjustments without altering the biochemical composition, enabling precise simulation of tissue mechanics across different physiological and pathological states.

A striking observation emerged when fibroblasts were cultured on this tissue-mimicking hydrogel. The cells initially spread on the surface but soon began migrating towards each other, coalescing into mesenchymal aggregates—a behavior absent on matrices comprising only collagen or alginate. This aggregation coincided with significant remodeling of collagen fibers into bundled structures, implying an active matrix-cell mechanical feedback mechanism. Such cell–matrix mechanical crosstalk facilitates long-range cellular interactions transmitted through the remodeled extracellular matrix, revealing novel insights into how collective cell behavior can be directed by the physical microenvironment.

Critical to this phenomenon is cellular contractility, as elucidated by experiments employing contractility inhibitors. When contractile forces were suppressed, mesenchymal aggregates dissipated into lone cells, accompanied by a marked downregulation of reprogramming-associated gene expression and loss of enhanced differentiation capacity. This underscores a positive feedback loop where matrix mechanics enhance cell contractility, which in turn drives reprogramming signals. The feedback mechanism creates a self-reinforcing cycle fundamental for driving the observed cellular phenotypic shifts.

Transcriptomic profiling further validated the profound reprogramming effects induced by the engineered hydrogel. Stemness-associated genes, notably markers emblematic of mesenchymal stem cells such as Id1, Id2, Cd36, and Cd9, were significantly upregulated within these aggregates. Concurrently, key signaling pathways implicated in cell fate determination—including Wnt, Hippo, and PPAR pathways—were robustly activated. Intriguingly, the traditional antagonism between adipogenic and osteogenic differentiation pathways was resolved, with genes corresponding to both lineages being simultaneously elevated, illustrating a nuanced and flexible cellular differentiation landscape fostered by mechanical cues.

Functional assays corroborated these findings, revealing that fibroblasts cultured on the hydrogel exhibited substantially increased lipid droplet accumulation upon adipogenic induction—at 2.5 times the level observed on standard matrices—and pronounced alkaline phosphatase (ALP) expression following osteogenic stimulation. These findings not only confirm the hydrogel’s role in promoting bidirectional differentiation potential but also highlight its utility as a versatile platform for stem cell modulation without biochemical additives.

Extending these discoveries to oncological applications, the team demonstrated that non-small cell lung cancer H1975 cells cultured within the tissue-mimicking hydrogel underwent transdifferentiation into adipocyte-like cells. Morphologically, the cancer cells shifted from a spread mesenchymal phenotype to aggregate formation, coupled with cortical actin reorganization indicative of reduced migratory potential. They expressed hallmark adipogenic markers such as Perilipin and PPARγ, confirming successful lineage conversion. This mechanical reprogramming effectively immobilizes cancer cells by inducing a less proliferative and more differentiated state.

Molecular analysis of cancer cells post-transdifferentiation revealed profound transcriptomic alterations. Genes driving epithelial-mesenchymal transition (EMT), a key contributor to metastasis and malignancy, were suppressed, whilst genes facilitating mesenchymal-epithelial transition (MET) were activated, suggesting a reversion to a more epithelial, less invasive phenotype. Oncogenes including EGFR, BRCA1, and CDC20 were downregulated, while tumor suppressor genes such as ACSL1, GADD45G, and CRB3 were upregulated, indicating a reversal of malignant characteristics. These comprehensive molecular shifts highlight the capacity of mechanical cues delivered by the hydrogel to reprogram cancer cells towards a less aggressive, therapy-sensitive state.

The clinical implications of this mechanical reprogramming approach are both vast and profound. Beyond its promise as a platform for ex vivo expansion and enhancement of autologous stem cells in regenerative medicine, the hydrogel system can be further translated into injectable scaffolds that facilitate in situ tissue repair by promoting aggregation and differentiation of endogenous or transplanted cells. In cancer treatment paradigms, this method offers a disruptive shift—transforming proliferative cancer cells into differentiated, non-proliferative adipocytes could attenuate tumor progression and complement existing chemotherapy and radiotherapy modalities, potentially mitigating drug resistance and relapse.

This mechanically driven reprogramming approach also addresses key limitations inherent in conventional methods. By sidestepping genetic modification and biochemical cocktails, it substantially reduces risks associated with off-target gene effects and tumorigenicity, while providing a stable physical niche that sustains reprogramming signals over extended durations. Its applicability across diverse cell types enhances the versatility of this platform, and its mimicry of native tissue mechanics offers a more physiologically relevant environment for drug screening, enabling precise evaluation of candidate compounds and their effects on cell fate within a biomimetic matrix.

In summary, the work led by Professors Yiwei Li and Bi-Feng Liu represents a landmark achievement in bioengineering and mechanobiology. By elucidating the essential interplay between matrix viscoelasticity, nonlinear elasticity, and cellular contractility, the study unveils a previously uncharted mechanism of long-range mechanical cell–cell interactions that drive potent reprogramming effects. This insight not only advances fundamental understanding of cell microenvironmental regulation but also propels the development of innovative therapeutic strategies aimed at addressing global challenges such as aging-related tissue degeneration and refractory cancers.

As this technology moves towards clinical translation, further refinement and optimization of hydrogel properties and delivery strategies will be pivotal. However, the promise it holds—as a novel, mechanically oriented, and safe means to manipulate cell behavior—positions it at the forefront of future biomedical innovation. The convergence of materials science, cell biology, and clinical medicine embodied by this hydrogel platform heralds a new chapter in harnessing the power of physical forces for human health.

Subject of Research: Not applicable

Article Title: Mechanical Cell Reprogramming on Tissue-Mimicking Hydrogels for Cancer Cell Transdifferentiation

News Publication Date: 18-Aug-2025

Web References: http://dx.doi.org/10.34133/research.0810

Image Credits: Copyright © 2025 Xueqing Ren et al.

Keywords: Tissue-mimicking hydrogel, mechanical cell reprogramming, viscoelasticity, nonlinear elasticity, fibroblast differentiation, cancer transdifferentiation, mechanobiology, extracellular matrix remodeling, cell contractility, regenerative medicine, adipogenesis, osteogenesis, cell aggregation

Epithelial cells, which form protective layers on both the interior and exterior surfaces of the body, serve as a frontline defense against pathogens, physical injury, and dehydration. These cells exhibit remarkable plasticity, adapting their shape and internal machinery in response to physical disruptions, such as wounds. What this study elucidates for the first time is the intimate relationship between the curvature of a gap’s edge and the morphological changes in the ER. Specifically, the ER transforms into either tubular network structures or flattened sheet-like conformations, contingent on whether the cellular gap curves outward (convex) or inward (concave), respectively.

This curvature-dependent transformation is not merely a structural curiosity but forms the mechanistic basis of two distinct cellular movements used by epithelial cells during the migratory process of wound closure. When facing a convex gap, epithelial cells extend broad, flat lamellipodia to crawl over the wound edges. In contrast, concave edges invoke a contractile “purse-string” response, wherein cells constrict actomyosin cables to draw wound margins together. This duality in movement strategies underscores the flexibility of epithelial cells and highlights the active role of ER morphology in coordinating these behaviors.

Delving deeper into the biophysics, the researchers discovered that mechanical forces operate differently at convex and concave interfaces, driving ER reorganization through distinct pathways. Outward-curving edges experience pushing forces, which favor the formation of tubular ER architectures. Conversely, inward-curving edges are subject to pulling forces that induce the ER to flatten into sheet-like domains. Such mechanical modulation of ER structure demonstrates a sophisticated form of cellular mechanotransduction, where physical forces are transduced into functional morphological and biochemical changes.

The experimental framework of this study was particularly innovative. Scientists used advanced microfabrication to generate precisely controlled microscopic gaps in epithelial cell monolayers, enabling unprecedented observation of cellular responses under varying geometrical constraints. Furthermore, cutting-edge imaging techniques, including high-resolution live-cell microscopy, provided real-time visualization of ER dynamics as cells migrated to close these gaps. These empirical observations were complemented by sophisticated mathematical models developed to describe and predict the ER’s morphological adaptations to curvature-induced mechanical stresses.

One of the study’s lead experimentalists, Dr. Simran Rawal from the Tata Institute of Fundamental Research Hyderabad, emphasized the broader implications of these findings. She noted that understanding the mechanics and organelle-driven signaling pathways involved in epithelial gap closure opens new avenues for therapeutic strategies targeting wound healing processes. Beyond immediate tissue repair, these insights might also illuminate pathological conditions where cellular migration is disrupted or hijacked, such as in cancer metastasis.

The mathematical modeling component of the research, led by Dr. Pradeep Keshavanarayana during his tenure at the University of Birmingham, represents a transformative approach to cell biology. By translating empirical data into quantitative frameworks, the models elucidate not only how cells physically change shape to close wounds but also how the ER functions as an internal sensor and mediator of mechanical stress. This modeling could be instrumental in designing synthetic tissues or developing targeted interventions that modulate ER behavior to enhance regenerative outcomes.

Professor Fabian Spill of the University of Birmingham, a corresponding author on the paper, highlighted the interdisciplinary nature of the project. By combining biological experimentation with mathematical rigor, the team unveiled a previously unrecognized connection between organelle morphology and higher-order tissue dynamics. The interplay between ER shape changes and collective epithelial movement underscores a new dimension of cellular mechanobiology, where internal organelle behavior directly influences emergent tissue properties such as barrier integrity and permeability.

Further enriching the scientific narrative, Professor Tamal Das of the Tata Institute discussed the role of the ER in mechanotransduction—the process whereby cells convert mechanical stimuli from their environment into biochemical responses. This fundamental process is integral to many physiological functions, including sensory perception like touch and balance. The study’s finding that ER morphology mediates mechanotransduction in epithelial cells broadens our understanding of how cellular structures integrate physical signals during coordinated migration, suggesting that organelles themselves are active participants in cellular mechanosensation.

Importantly, the ability of the ER to remodel its architecture in response to curvature and mechanical forces may have significant ramifications beyond epithelial wound healing. The strategies employed by cells here could parallel mechanisms in other contexts such as embryonic development, immune responses, and cancer invasion, where cells must navigate and adapt to complex 3D environments. By targeting ER dynamics pharmacologically or genetically, future therapies might be developed to modulate cellular migration and adhesion, offering novel treatments for a wide spectrum of diseases.

The research supports a paradigm shift in the field of cell biology: organelles like the ER are not merely background components supporting cellular metabolism but are active sensors and effectors that dynamically link mechanical environments with intracellular responses. This discovery invites further exploration into other organelles’ roles and how they integrate with the cytoskeleton and membrane systems to regulate cellular behavior.

As wound healing remains a critical physiological process, especially in clinical settings such as surgery, chronic wounds, and tissue engineering, harnessing the insights from this study could lead to breakthroughs in how medical interventions are designed. By promoting efficient gap closure through manipulation of ER morphology or modulating the mechanical microenvironment, clinicians may enhance repair speed and minimize scarring.

In summary, this pioneering work uncovers a fundamental mechanism whereby the curvature of wounds guides epithelial cell migration through ER remodeling, influencing cell mechanics and tissue dynamics. The interplay of experimental observations with mathematical modeling offers a comprehensive framework for understanding the cellular processes underlying tissue repair and regeneration. Such knowledge sets the stage for future innovations in regenerative medicine, cancer biology, and mechanobiology.

Subject of Research: Cells

Article Title: Curvature-dependent morphological reorganization of the endoplasmic reticulum determines the mode of epithelial migration

News Publication Date: 18-Aug-2025

Keywords: Cell biology, Wound healing, Cancer cells, Epithelial cells, Signaling pathways, Mechanotransduction pathways, Mathematics, Mathematical analysis