Tunable 3D Hydrogel Microchannel Networks to Study Confined Mammalian Cell Migration

Multimaterial 3D Laser Printing of Cell-Adhesive and Cell-Repellent Hydrogels

Here, a straightforward method is reported for manufacturing 3D microstructured cell-adhesive and cell-repellent multimaterials using two-photon laser printing. Compared to existing strategies, this approach offers bottom-up molecular control, high customizability, and rapid and precise 3D fabrication. The printable cell-adhesive polyethylene glycol (PEG) based material includes an Arg-Gly-Asp (RGD) containing peptide synthesized through solid-phase peptide synthesis, allowing for precise control of the peptide design. Remarkably, minimal amounts of RGD peptide (< 0.1 wt%) suffice for imparting cell-adhesiveness, while maintaining identical mechanical properties in the 3D printed microstructures to those of the cell-repellent, PEG-based material. Fluorescent labeling of the RGD peptide facilitates visualization of its presence in cell-adhesive areas. To demonstrate the broad applicability of the system, the fabrication of cell-adhesive 2.5D and 3D structures is shown, fostering the adhesion of fibroblast cells within these architectures. Thus, this approach allows for the printing of high-resolution, true 3D structures suitable for diverse applications, including cellular studies in complex environments.

Toward morphologically relevant extracellular matrix: nanofiber-hydrogel composites for tumor cell culture

The natural extracellular matrix (ECM) consists of a continuous integrated fibrin network and a negatively charged proteoglycan-based matrix. In this work, we report a novel three-dimensional nanofiber hydrogel composite that mimics the natural ECM structure, exhibiting both degradability and mechanical characteristics comparable to that of tumor tissue. The embedded nanofiber improves the hydrogel mechanical properties, and varying the fiber density can match the elastic modulus of different tumor tissues (1.51-10.77 kPa). The degradability of the scaffold gives sufficient space for tumor cells to secrete and remodel the ECM. The expression levels of cancer stem cell markers confirmed the development of aggressive and metastatic phenotypes of prostate cancer cells in the 3D scaffold. Similar results were obtained in terms of anticancer resistance of prostate cancer cells in 3D scaffolds showing stem cell-like properties, suggesting that the current bionic 3D scaffold tumor model has broad potential in the development of effective targeted agents.

Trends in confinement-induced cell migration and multi-omics analysis

Cell migration is an essential manner of different cell lines that are involved in embryological development, immune responses, tumorigenesis, and metastasis in vivo. Physical confinement derived from crowded tissue microenvironments has pivotal effects on migratory behaviors. Distinct migration modes under a heterogeneous extracellular matrix (ECM) have been extensively studied, uncovering potential molecular mechanisms involving a series of biological processes. Significantly, multi-omics strategies have been launched to provide multi-angle views of complex biological phenomena, facilitating comprehensive insights into molecular regulatory networks during cell migration. In this review, we describe biomimetic devices developed to explore the migratory behaviors of cells induced by different types of confined microenvironments in vitro. We also discuss the results of multi-omics analysis of intrinsic molecular alterations and critical pathway dysregulations of cell migration under heterogeneous microenvironments, highlighting the significance of physical confinement-triggered intracellular signal transduction in order to regulate cellular behaviors. Finally, we discuss both the challenges and promise of mechanistic analysis in confinement-induced cell migration, promoting the development of early diagnosis and precision therapeutics.

Liquid-liquid interfaces enable tunable cell confinement to recapitulate surrounding tissue deformations during neutrophil interstitial migration in vivo

Cell migration is regulated by an interplay between both chemical and mechanical cues. Immune cells navigate through interstitial spaces and generate forces to deform surrounding cells, which in turn exert opposing pressures that regulate cell morphology and motility mechanisms. Current in vitro systems to study confined cell migration largely utilize rigid materials orders of magnitude stiffer than surrounding cells, limiting insights into how these local physical interactions regulate interstitial cell motility. Here, we first characterize mechanical interactions between neutrophils and surrounding cells in larval zebrafish and subsequently engineer in vitro migration channels bound by a deformable liquid-liquid interface that responds to cell generated pressures yielding a gradient of confinement across the length of a single cell. Tuning confining pressure gradients replicates mechanical interactions with surrounding cells during interstitial migration in vivo . We find that neutrophils favor a bleb-based mechanism of force generation to deform a barrier applying cell-scale confining forces. This work introduces a biomimetic material interface that enables new avenues of exploring the influence of mechanical forces on cell migration.

Lysyl hydroxylase LH1 promotes confined migration and metastasis of cancer cells by stabilizing Septin2 to enhance actin network

BACKGROUND

Excessive extracellular matrix deposition and increased stiffness are typical features of solid tumors such as hepatocellular carcinoma (HCC) and pancreatic ductal adenocarcinoma (PDAC). These conditions create confined spaces for tumor cell migration and metastasis. The regulatory mechanism of confined migration remains unclear.

METHODS

LC-MS was applied to determine the differentially expressed proteins between HCC tissues and corresponding adjacent tissue. Collective migration and single cell migration microfluidic devices with 6 μm-high confined channels were designed and fabricated to mimic the in vivo confined space. 3D invasion assay was created by Matrigel and Collagen I mixture treat to adherent cells. 3D spheroid formation under various stiffness environment was developed by different substitution percentage GelMA. Immunoprecipitation was performed to pull down the LH1-binding proteins, which were identified by LC-MS. Immunofluorescent staining, FRET, RT-PCR, Western blotting, FRAP, CCK-8, transwell cell migration, wound healing, orthotopic liver injection mouse model and in vivo imaging were used to evaluate the target expression and cellular phenotype.

RESULTS

Lysyl hydroxylase 1 (LH1) promoted the confined migration of cancer cells at both collective and single cell levels. In addition, LH1 enhanced cell invasion in a 3D biomimetic model and spheroid formation in stiffer environments. High LH1 expression correlated with poor prognosis of both HCC and PDAC patients, while it also promoted in vivo metastasis. Mechanistically, LH1 bound and stabilized Septin2 (SEPT2) to enhance actin polymerization, depending on the hydroxylase domain. Finally, the subpopulation with high expression of both LH1 and SEPT2 had the poorest prognosis.

CONCLUSIONS

LH1 promotes the confined migration and metastasis of cancer cells by stabilizing SEPT2 and thus facilitating actin polymerization.

A Beginner’s Guide to the Characterization of Hydrogel Microarchitecture for Cellular Applications

The extracellular matrix (ECM) is a three-dimensional, acellular scaffold of living tissues. Incorporating the ECM into cell culture models is a goal of cell biology studies and requires biocompatible materials that can mimic the ECM. Among such materials are hydrogels: polymeric networks that derive most of their mass from water. With the tuning of their properties, these polymer networks can resemble living tissues. The microarchitectural properties of hydrogels, such as porosity, pore size, fiber length, and surface topology can determine cell plasticity. The adequate characterization of these parameters requires reliable and reproducible methods. However, most methods were historically standardized using other biological specimens, such as 2D cell cultures, biopsies, or even animal models. Therefore, their translation comes with technical limitations when applied to hydrogel-based cell culture systems. In our current work, we have reviewed the most common techniques employed in the characterization of hydrogel microarchitectures. Our review provides a concise description of the underlying principles of each method and summarizes the collective data obtained from cell-free and cell-loaded hydrogels. The advantages and limitations of each technique are discussed, and comparisons are made. The information presented in our current work will be of interest to researchers who employ hydrogels as platforms for cell culture, 3D bioprinting, and other fields within hydrogel-based research.

A Co-Polymerizable Linker for the Covalent Attachment of Fibronectin Makes pHEMA Hydrogels Cell-Adhesive

Hydrogels are attractive biomaterials because their chemical and mechanical properties can be tailored to mimic those of biological tissues. However, many hydrogels do not allow cell or protein attachment. Therefore, they are post-synthetically functionalized by adding functional groups for protein binding, which then allows cell adhesion in cell culture substrates. However, the degree of functionalization and covalent binding is difficult to analyze in these cases. Moreover, the density of the functional groups and the homogeneity of their distribution is hard to control. This work introduces another strategy for the biofunctionalization of hydrogels: we synthesized a polymerizable linker that serves as a direct junction between the polymeric structure and cell adhesion proteins. This maleimide-containing, polymerizable bio-linker was copolymerized with non-functionalized monomers to produce a bioactive hydrogel based on poly(2-hydroxyethyl methacrylate) (pHEMA). Therefore, the attachment site was only controlled by the polymerization process and was thus uniformly distributed throughout the hydrogel. In this way, the bio-conjugation by a protein-binding thiol-maleimide Michael-type reaction was possible in the entire hydrogel matrix. This approach enabled a straightforward and highly effective biofunctionalization of pHEMA with the adhesion protein fibronectin. The bioactivity of the materials was demonstrated by the successful adhesion of fibroblast cells.