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1. Vascular and nonvascular transmission of systemic reactive oxygen signals during wounding and heat stress

   https://doi.org/10.1093/plphys/kiab157  

   Zandalinas, Sara I; Mittler, Ron (April 2021, Plant Physiology)

   null (Ed.)

   Abstract Sensing of heat, high light (HL), or mechanical injury by a single leaf of a plant results in the activation of different systemic signals that reach systemic tissues within minutes and trigger systemic acquired acclimation (SAA) or systemic wound responses (SWRs), resulting in a heightened state of stress readiness of the entire plant. Among the different signals associated with rapid systemic responses to stress in plants are electric, calcium, and reactive oxygen species (ROS) waves. These signals propagate from the stressed or injured leaf to the rest of the plant through the plant vascular bundles, and trigger SWRs and SAA in systemic tissues. However, whether they can propagate through other cell types, and whether or not they are interlinked, remain open questions. Here we report that in response to wounding or heat stress (HS), but not HL stress, the ROS wave can propagate through mesophyll cells of Arabidopsis (Arabidopsis thaliana). Moreover, we show that ROS production by mesophyll cells during these stresses is sufficient to restore SWR and SAA transcript accumulation in systemic leaves, as well as SAA to HS (but not HL). We further show that propagation of the ROS wave through mesophyll cells could contribute to systemic signal integration during HL and HS stress combination. Our findings reveal that the ROS wave can propagate through tissues other than the vascular bundles of plants, and that different stresses can trigger different types of systemic signals that propagate through different cell layers and induce stress-specific systemic responses. 

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2. Construction of 3D-Engineered Glioma Tissues Using the Acoustic Patterning Device

   https://doi.org/10.1115/DETC2024-141907  

   Du, Yingshan; Li, Jiali; Shen, Liang; Pei, Zhe; Cai, Bowen; Li, Teng; Qiu, Chongpeng; Tian, Zhenhua (August 2024, American Society of Mechanical Engineers)

   Abstract Cell patterning techniques play a pivotal role in the development of three-dimensional (3D) engineered tissues, holding significant promise in regenerative medicine, drug screening, and disease research. Current techniques encompass various mechanisms, such as nanoscale topographic patterning, mechanical loading, chemical coating, 3D inkjet printing, electromagnetic fields, and acoustic waves. In this study, we introduce a unique standing bulk waves-based acoustic cell patterning device designed for constructing anisotropic-engineered glioma tissues containing acoustically patterned human glioblastoma cell U251. Our device features two orthogonal pairs of piezoelectric transducers securely mounted on a customized holder. The energy of standing bulk waves generated from these transducers can be transmitted into the medium in a Petri dish through its bottom wall. Cells in the medium can be directed to the local minima of Gor’kov potential fields and trapped by the resultant acoustic radiation force. Through proof-of-concept experiments, we validate the functionality of our acoustic patterning device and assess the morphology and differentiation of U251 cells within the engineered glioma tissues. Our findings reveal that cells can be arranged in different distributions, such as parallel-line-like and lattice-like patterns. Moreover, the aligned cells exhibit more obvious elongation along the cell alignment orientation compared to the result of a control group. We anticipate that this study will catalyze the advancement in contactless cell patterning technologies within tissue engineering, facilitating the development of engineered tissues for applications in regenerative medicine and disease research. 

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3. Rear cortex contraction aids in nuclear transit during confined migration by increasing pressure in the cell posterior

   https://doi.org/10.1242/jcs.260623  

   Keys, Jeremy; Cheung, Brian_C H; Elpers, Margaret A; Wu, Mingming; Lammerding, Jan (June 2024, Journal of Cell Science)

   ABSTRACT As cells migrate through biological tissues, they must frequently squeeze through micron-sized constrictions in the form of interstitial pores between extracellular matrix fibers and/or other cells. Although it is now well recognized that such confined migration is limited by the nucleus, which is the largest and stiffest organelle, it remains incompletely understood how cells apply sufficient force to move their nucleus through small constrictions. Here, we report a mechanism by which contraction of the cell rear cortex pushes the nucleus forward to mediate nuclear transit through constrictions. Laser ablation of the rear cortex reveals that pushing forces behind the nucleus are the result of increased intracellular pressure in the rear compartment of the cell. The pushing forces behind the nucleus depend on accumulation of actomyosin in the rear cortex and require Rho kinase (ROCK) activity. Collectively, our results suggest a mechanism by which cells generate elevated intracellular pressure in the posterior compartment to facilitate nuclear transit through three-dimensional (3D) constrictions. This mechanism might supplement or even substitute for other mechanisms supporting nuclear transit, ensuring robust cell migrations in confined 3D environments. 

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4. Engineering Tissues of the Central Nervous System: Interfacing Conductive Biomaterials with Neural Stem/Progenitor Cells

   https://doi.org/10.1002/adhm.202101577  

   Bierman‐Duquette, Rebecca_D; Safarians, Gevick; Huang, Joyce; Rajput, Bushra; Chen, Jessica_Y; Wang, Ze_Zhong; Seidlits, Stephanie_K (December 2021, Advanced Healthcare Materials)

   Abstract Conductive biomaterials provide an important control for engineering neural tissues, where electrical stimulation can potentially direct neural stem/progenitor cell (NS/PC) maturation into functional neuronal networks. It is anticipated that stem cell‐based therapies to repair damaged central nervous system (CNS) tissues and ex vivo, “tissue chip” models of the CNS and its pathologies will each benefit from the development of biocompatible, biodegradable, and conductive biomaterials. Here, technological advances in conductive biomaterials are reviewed over the past two decades that may facilitate the development of engineered tissues with integrated physiological and electrical functionalities. First, one briefly introduces NS/PCs of the CNS. Then, the significance of incorporating microenvironmental cues, to which NS/PCs are naturally programmed to respond, into biomaterial scaffolds is discussed with a focus on electrical cues. Next, practical design considerations for conductive biomaterials are discussed followed by a review of studies evaluating how conductive biomaterials can be engineered to control NS/PC behavior by mimicking specific functionalities in the CNS microenvironment. Finally, steps researchers can take to move NS/PC‐interfacing, conductive materials closer to clinical translation are discussed. 

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5. Gene-free methodology for cell fate dynamics during development

   https://doi.org/10.7554/eLife.30743  

   Corson, Francis; Siggia, Eric D (December 2017, eLife)

   At first, embryos are made up of identical cells. Then, as the embryo develops, these cells specialize into different types, such as heart and brain cells. Chemical signals sent and received by the cells are key to forming the right type of cell at the right time and place. The cellular machinery that produces and interprets these signals is exceedingly complex and difficult to understand. In the 1950s, Conrad Waddington presented an alternative way of thinking about how an unspecialized cell progresses to one of many different fates. He suggested visualizing the developing cell as a ball rolling along a hilly landscape. As the ball travels, obstacles in its way guide it along particular paths. Eventually the ball comes to rest in a valley, with each valley in the landscape representing a different cell fate. Although this “landscape model” is an appealing metaphor for how signaling events guide cell specialization, it was not clear whether it could be put to productive use. The egg-laying organ in the worm species Caenorhabditis elegans is called the vulva, and is often studied by researchers who want to learn more about how organs develop. The vulva develops from a small number of identical cells that adopt one of three possible cell fates. Two chemical signals, called epidermal growth factor (EGF) and Notch, control this specialization process. Corson and Siggia have now constructed a simple landscape model that can reproduce the normal arrangement of cell types in the vulva. When adjusted to describe the effect of genetic mutations that affect either EGF or Notch, the model could predict the outcome of mutations that affect both signals at once. The twists and turns of cell paths in the landscape could also account for several non-intuitive cell fate outcomes that had been assumed to result from subtle regulation of EGF and Notch signals. Landscape models should be easy to apply to other developing tissues and organs. By providing an intuitive picture of how signals shape cellular decisions, the models could help researchers to learn how to control cell and tissue development. This could lead to new treatments to repair or replace failing organs, making regenerative medicine a reality. 

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