bims-ecemfi 2024-12-15 papers

Elife. 2024 Dec 13. pii: RP96821. [Epub ahead of print]13

Amoeboid cells undergo durotaxis with soft end polarized NMIIA.

Chenlu Kang, Pengcheng Chen, Xin Yi, Dong Li, Yiping Hu, Yihong Yang, Huaqing Cai, Bo Li, Congying Wu.

Cell migration towards stiff substrates has been coined as durotaxis and implicated in development, wound healing, and cancer, where complex interplays between immune and non-immune cells are present. Compared to the emerging mechanisms underlying the strongly adhesive mesenchymal durotaxis, little is known about whether immune cells - migrating in amoeboid mode - could follow mechanical cues. Here, we develop an imaging-based confined migration device with a stiffness gradient. By tracking live cell trajectory and analyzing the directionality of T cells and neutrophils, we observe that amoeboid cells can durotax. We further delineate the underlying mechanism to involve non-muscle myosin IIA (NMIIA) polarization towards the soft-matrix-side but may not require differential actin flow up- or down-stiffness gradient. Using the protista Dictyostelium, we demonstrate the evolutionary conservation of amoeboid durotaxis. Finally, these experimental phenomena are theoretically captured by an active gel model capable of mechanosensing. Collectively, these results may shed new lights on immune surveillance and recently identified confined migration of cancer cells, within the mechanically inhomogeneous tumor microenvironment or the inflamed fibrotic tissues.

Keywords: T cell; cell biology; cell migration; cytoskeleton; dictyostelium; durotaxis; mechanobiology; neutrophil

DOI: https://doi.org/10.7554/eLife.96821

J Mater Chem B. 2024 Dec 09.

Photodegradable polyacrylamide tanglemers enable spatiotemporal control over chain lengthening in high-strength and low-hysteresis hydrogels.

Joshua S Lee, Bruce E Kirkpatrick, Abhishek P Dhand, Lea Pearl Hibbard, Benjamin R Nelson, Nathaniel P Skillin, Makayla C Johnson, Dilara Batan, Benjamin D Fairbanks, Timothy J White, Christopher N Bowman, Jason A Burdick, Kristi S Anseth.

Covalent hydrogel networks suffer from a stiffness-toughness conflict, where increased crosslinking density enhances the modulus of the material but also leads to embrittlement and diminished extensibility. Recently, strategies have been developed to form highly entangled hydrogels, colloquially referred to as tanglemers, by optimizing polymerization conditions to maximize the density and length of polymer chains and minimize the crosslinker concentration. It is challenging to assess entanglements in crosslinked networks beyond approximating their theoretical contribution to mechanical properties; thus, in this work, we synthesize and characterize polyacrylamide tanglemers using a photolabile crosslinker, which allows for direct assessment of covalent trapping of entanglements under tension. Further, this chemistry allows tuning of the modulus in situ by crosslink photocleavage (from tensile modulus (ET) = 100 kPa to <25 kPa). Beyond cleavage of crosslinks, we demonstrate that even non-degradable tanglemer formulations can be photo-softened and completely degraded through Fe3+-mediated oxidation of the polyacrylamide backbone. While both photodegradation methods are useful for spatial patterning and result in softer gels with reduced fracture strength, only crosslink photocleavage improves gel extensibility via light-induced chain lengthening (εF = 700% to >1500%). Crosslink photocleavage in tanglemers also affords significant control over localized swelling and diffusivity. In sum, we introduce a simple and user-directed approach for probing entanglements and asserting spatiotemporal control over stress-strain responses and small molecule diffusivity in polyacrylamide tanglemers, suggesting a multitude of potential soft matter applications including controlled release and tunable bioadhesive interfaces.

DOI: https://doi.org/10.1039/d4tb02149e

Placenta. 2024 Dec 05. pii: S0143-4004(24)00791-4. [Epub ahead of print]

Organoid generation from trophoblast stem cells highlights distinct roles for cytotrophoblasts and stem cells in organoid formation and expansion.

Cherry Sun, Lawrence W Chamley, Joanna L James.

BACKGROUND: Organoids are stem-cell derived, self-organised, three-dimensional cultures that improve in vitro recapitulation of tissue structure. The generation of trophoblast organoids using primary placental villous digests (containing cytotrophoblasts and trophoblast stem cells (TSC)) improved high-throughput assessment of early trophoblast differentiation. However, the relative contributions of cytotrophoblasts and TSCs to trophoblast organoid growth and differentiation remain unclear, with implications for model interpretation. Here we sought to generate organoids from side-population trophoblasts (SpTSCs) to better understand the contribution of TSC to trophoblast organoid formation.
METHODS: Methods were adapted from Haider et al., 2018 to generate organoids from Okae TSCs (OkTSCs) or SpTSCs. Organoid growth was compared with primary villous trophoblast organoids and cellular composition interrogated by immunohistochemistry.
RESULTS: Organoids can be derived from first-trimester SpTSCs that exhibit similar architecture to those from primary villous trophoblast. However, organoids established from pure TSC populations (OkTSC or SpTSC) have different growth dynamics to primary placental villous digest-derived organoids - with OkTSCs developing faster and spontaneously generating migratory cells, whilst SpTSC organoids grow more slowly. Importantly, depletion of SpTSC from first-trimester villous digests ablates organoid formation. Finally, the capacity of the side-population technique to isolate late-gestation TSC enabled the generation of trophoblast organoids from term placentae, although these were significantly smaller than their first-trimester SpTSC counterparts.
DISCUSSION: Together, this work highlights the requirement of TSC for organoid formation, and the functional distinction between TSC and cytotrophoblasts. Proof-of-principle data demonstrating organoid generation from late gestation TSC isolated directly from the placenta lays the groundwork for future disease models.

Keywords: 3D culture; Organoid; Placenta; Side-population trophoblasts; Transit amplifying cell; Trophoblast stem cell

DOI: https://doi.org/10.1016/j.placenta.2024.12.003

Nature. 2024 Dec 09.

A framework for neural organoids, assembloids and transplantation studies.

As the field of neural organoids and assembloids rapidly expands, there is an emergent need for guidance and advice on designing, conducting and reporting experiments to increase the reproducibility and utility of these models. Here, our consortium- representing specialized laboratories from around the world- presents a framework for the experimental process that ranges from ensuring the quality and integrity of human pluripotent stem cells to characterizing and manipulating neural cells in vitro, and from transplantation techniques to considerations for modeling human development, evolution, and disease. As with all scientific endeavors, we advocate for rigorous experimental designs tailored to explicit scientific questions, and transparent methodologies and data sharing, to provide useful knowledge for both current research practices and for developing regulatory standards.

DOI: https://doi.org/10.1038/s41586-024-08487-6

Nature. 2024 Dec;636(8042): 361-367

Sacrificial capillary pumps to engineer multiscalar biological forms.

Subramanian Sundaram, Joshua H Lee, Isabel M Bjørge, Christos Michas, Sudong Kim, Alex Lammers, João F Mano, Jeroen Eyckmans, Alice E White, Christopher S Chen.

Natural tissues are composed of diverse cells and extracellular materials whose arrangements across several length scales-from subcellular lengths1 (micrometre) to the organ scale2 (centimetre)-regulate biological functions. Tissue-fabrication methods have progressed to large constructs, for example, through stereolithography3 and nozzle-based bioprinting4,5, and subcellular resolution through subtractive photoablation6-8. However, additive bioprinting struggles with sub-nozzle/voxel features9 and photoablation is restricted to small volumes by prohibitive heat generation and time10. Building across several length scales with temperature-sensitive, water-based soft biological matter has emerged as a critical challenge, leaving large classes of biological motifs-such as multiscalar vascular trees with varying calibres-inaccessible with present technologies11,12. Here we use gallium-based engineered sacrificial capillary pumps for evacuation (ESCAPE) during moulding to generate multiscalar structures in soft natural hydrogels, achieving both cellular-scale (<10 µm) and millimetre-scale features. Decoupling the biomaterial of interest from the process of constructing the geometry allows non-biocompatible tools to create the initial geometry. As an exemplar, we fabricated branched, cell-laden vascular trees in collagen, spanning approximately 300-µm arterioles down to the microvasculature (roughly ten times smaller). The same approach can micropattern the inner surface of vascular walls with topographical cues to orient cells in 3D and engineer fine structures such as vascular malformations. ESCAPE moulding enables the fabrication of multiscalar forms in soft biomaterials, paving the way for a wide range of tissue architectures that were previously inaccessible in vitro.

DOI: https://doi.org/10.1038/s41586-024-08175-5