Tissue-specific compensatory mechanisms maintain tissue architecture and body size independent of cell size in polyploid zebrafish

Genome duplications and ploidy transitions have occurred in nearly every major taxon of eukaryotes, but they are far more common in plants than in animals. Due to the conservation of the nuclear:cytoplasmic volume ratio increased DNA content results in larger cells. In plants, polyploid organisms are larger than diploids as cell number remains relatively constant. Conversely, vertebrate body size does not correlate with cell size and ploidy as vertebrates compensate for increased cell size to maintain tissue architecture and body size. This has historically been explained by a simple reduction in cell number that matches the increase in cell size maintaining body size as ploidy increases, but here we show that the compensatory mechanisms that maintain body size in triploid zebrafish are tissue-specific: A) erythrocytes respond in the classical pattern with a reduced number of larger erythrocytes in circulation, B) muscle, a tissue comprised of polynucleated muscle fibers, compensates by reducing the number of larger nuclei such that myofiber and myotome size in unaffected by ploidy, and C) vascular tissue compensates by thickening blood vessel walls, possibly at the expense of luminal diameter. Understanding the physiological implications of ploidy on tissue function requires a detailed description of the specific mechanisms of morphological compensation occurring in each tissue to understand how ploidy changes affect development and physiology.

The probiotic Lacticaseibacillus rhamnosus HN001 influences the architecture and gene expression of small intestine tissue in a piglet model

This study investigated the effects of Lacticaseibacillus rhamnosus HN001 supplementation on the architecture and gene expression in small intestinal tissues of piglets used as an animal model for infant humans. Twenty-four 10-d-old entire male piglets (4·3 (sd 0·59) kg body weight) were fed an infant formula (IF) (control) or IF supplemented with 1·3 × 105 (low dose) or 7·9 × 106 (high dose) colony-forming units HN001 per ml of reconstituted formula (n 8 piglets/treatment). After 24 d, piglets were euthanised. Samples were collected to analyse the histology and gene expression (RNAseq and qPCR) in the jejunal and ileal tissues, blood cytokine concentrations, and blood and faecal calprotectin concentrations. HN001 consumption altered (false discovery rate < 0·05) gene expression (RNAseq) in jejunal tissues but not in ileal tissues. The number of ileal goblet cells and crypt surface area increased quadratically (P < 0·05) as dietary HN001 levels increased, but no increase was observed in the jejunal tissues. Similarly, blood plasma concentrations of IL-10 and calprotectin increased linearly (P < 0·05) as dietary HN001 levels increased. In conclusion, supplementation of IF with HN001 affected the architecture and gene expression of small intestine tissue, blood cytokine concentration and frequencies, and blood calprotectin concentrations, indicating that HN001 modulated small intestinal tissue maturation and immunity in the piglet model.

Δ133p53 coordinates ECM-driven morphogenesis and gene expression in three-dimensional mammary epithelial acini

Growing evidence indicates that p53 (encoded by TP53) has a crucial role in normal tissue development. The role of the canonical p53 (p53α) and its 12 isoforms in development and homeostasis of healthy tissue remains poorly understood. Here, we demonstrate that the Δ133p53 isoforms, the three short isoforms of p53, respond specifically to laminin-111 and play an important regulatory role in formation of mammary organoids in concert with p53α. We demonstrate that down-modulation of Δ133p53 isoforms leads to changes in gene expression of the extracellular matrix molecules fibronectin (FN), EDA+-FN, laminin α5 and laminin α3 in human breast epithelial cells. These changes resulted in increased actin stress fibers and enhanced migratory behavior of cells in two-dimensional culture. We found that α5β1-integrin coupled with the extracellularly deposited EDA+-FN activates the Akt signaling pathway in three-dimensional (3D) culture when Δ133p53 is dysregulated. Cells that do not express detectable Δ133p53 isoforms or express low levels of these isoforms failed to form polarized structures in 3D. These results uncover that Δ133p53 isoforms coordinate expression and deposition of organ-specific ECM molecules that are critical for maintenance of tissue architecture and function.

Single-cell and spatially resolved analysis uncovers cell heterogeneity of breast cancer

The heterogeneity and the complex cellular architecture have a crucial effect on breast cancer progression and response to treatment. However, deciphering the neoplastic subtypes and their spatial organization is still challenging. Here, we combine single-nucleus RNA sequencing (snRNA-seq) with a microarray-based spatial transcriptomics (ST) to identify cell populations and their spatial distribution in breast cancer tissues. Malignant cells are clustered into distinct subpopulations. These cell clusters not only have diverse features, origins and functions, but also emerge to the crosstalk within subtypes. Furthermore, we find that these subclusters are mapped in distinct tissue regions, where discrepant enrichment of stromal cell types are observed. We also inferred the abundance of these tumorous subpopulations by deconvolution of large breast cancer RNA-seq cohorts, revealing differential association with patient survival and therapeutic response. Our study provides a novel insight for the cellular architecture of breast cancer and potential therapeutic strategies.

Measuring Intercellular Interface Area in Plant Tissues Using Quantitative 3D Image Analysis

The cells which make up plant tissues remain fixed together through shared cell walls. Cell-to-cell communication principally takes place through these shared interfaces through a combination of plasmodesmata, transporters, and the apoplastic space. To better understand the capacity for intercellular communication in plant tissues, this chapter outlines a method which can be used to quantify the surface area of shared intercellular interfaces using whole mount imaging and quantitative 3D image analysis. This method allows the potential for intercellular communication as prescribed by cellular architecture to be measured at single cell resolution.

The suppressive role of nanoencapsulated chia oil against DMBA-induced breast cancer through oxidative stress repression and tumor genes expression modulation in rats

BACKGROUND

Chia oil is high in omega-3 fatty acids, which have been linked to a lower risk of many diseases, including cancer. Oil encapsulation is a method that holds promise for maintaining oil content while enhancing solubility and stability. The purpose of this study is to prepare nanoencapsulated Chia oil and investigate its suppressive effects on rat chemically induced breast cancer.

METHODS

The oil was extracted from commercial Chia seeds and their fatty acids were analyzed using Gas Chromatography-mass spectrometry (GC/MS). Sodium alginate was used as a loading agent to create the Chia oil nanocapsules. The DPPH assay was used to assess the oil nanocapsules' capacity to scavenge free radicals. Breast cancer induction was done by single dose subcutaneously administration of 80 mg/kg dimethylbenz (a) anthracene (DMBA). Models of breast cancer were given Chia oil nanocapsules orally for one month at doses of 100 and 200 mg/kg. Through measuring intracellular reactive oxygen species (ROS) and protein carbonyl, assessing the gene expression of tumor suppressor genes (BRCA 1 & 2, TP53), and conducting histopathological analysis, the suppressive effect of Chia oil nanocapsules was examined.

RESULTS

The increase in ROS and PC levels brought on by DMBA was significantly decreased by the administration of Chia oil nanocapsules. In tumor tissue from rats given Chia oil nanocapsules, the mRNA expression levels of BRCA1, BRCA2, and TP53 were controlled Histopathological analysis clarified that the tissue architecture of breast tumors was improved by nanocapsules management.

CONCLUSIONS

These findings demonstrate the ability of Chia oil nanocapsules to inhibit cancer cells in the rat breast.

Regulation of tissue architecture and stem cell dynamics to sustain homeostasis and repair in the skin epidermis

Stratified epithelia are made up of several layers of cells, which act as a protective barrier for the organ they cover. To ensure their shielding effect, epithelia are naturally able to cope with constant environmental insults. This ability is enabled by their morphology and architecture, as well as the continuous turnover of stem and progenitor cells that constitute their building blocks. Stem cell fate decisions and dynamics are fundamental key biological processes that allow epithelia to exert their functions. By focusing on the skin epidermis, this review discusses how tissue architecture is generated during development, maintained through adult life, and re-established during regeneration.

Assembly of lung progenitors into developmentally-inspired geometry drives differentiation via cellular tension

During organogenesis groups of differentiating cells self-organize into a series of structural intermediates with defined architectural forms. Evidence is emerging that such architectural forms are important in guiding cell fate, yet in vitro methods to guide cell fate have focused primarily on un-patterned exposure of stems cells to developmentally relevant chemical cues. We set out to ask if organizing differentiating lung progenitors into developmentally relevant structures could be used to influence differentiation status. Specifically, we use elastomeric substrates to guide self-assembly of human pluripotent stem cell-derived lung progenitors into developmentally-relevant sized tubes and assess the impact on differentiation. Culture in 100 μm tubes reduced the percentage of SOX2⁺SOX9⁺ cells and reduced proximal fate potential compared to culture in 400 μm tubes or on flat surfaces. Cells in 100 μm tubes curved to conform to the tube surface and experienced increased cellular tension and reduced elongation. Pharmacologic disruption of tension through inhibition of ROCK, myosin II activity and actin polymerization in tubes resulted in maintenance of SOX2⁺SOX9⁺ populations. Furthermore, this effect required canonical WNT signaling. This data suggests that structural forms, when developmentally relevant, can drive fate choice during directed differentiation via a tension-based canonical WNT dependent mechanism.

Multiscale analysis of architecture, cell size and the cell cortex reveals cortical F-actin density and composition are major contributors to mechanical properties during convergent extension

The large-scale movements that construct complex three-dimensional tissues during development are governed by universal physical principles. Fine-grained control of both mechanical properties and force production is crucial to the successful placement of tissues and shaping of organs. Embryos of the frog Xenopus laevis provide a dramatic example of these physical processes, as dorsal tissues increase in Young's modulus by six-fold to 80 Pascal over 8 h as germ layers and the central nervous system are formed. These physical changes coincide with emergence of complex anatomical structures, rounds of cell division, and cytoskeletal remodeling. To understand the contribution of these diverse structures, we adopt the cellular solids model to relate bulk stiffness of a solid foam to the unit size of individual cells, their microstructural organization, and their material properties. Our results indicate that large-scale tissue architecture and cell size are not likely to influence the bulk mechanical properties of early embryonic or progenitor tissues but that F-actin cortical density and composition of the F-actin cortex play major roles in regulating the physical mechanics of embryonic multicellular tissues.

Development of the liver: Insights into organ and tissue morphogenesis

Recent development of improved tools and methods to analyse tissues at the three-dimensional level has expanded our capacity to investigate morphogenesis of foetal liver. Here, we review the key morphogenetic steps during liver development, from the prehepatic endoderm stage to the postnatal period, and consider several model organisms while focussing on the mammalian liver. We first discuss how the liver buds out of the endoderm and gives rise to an asymmetric liver. We next outline the mechanisms driving liver and lobe growth, and review morphogenesis of the intra- and extrahepatic bile ducts; morphogenetic responses of the biliary tract to liver injury are discussed. Finally, we describe the mechanisms driving formation of the vasculature, namely venous and arterial vessels, as well as sinusoids.

Fluorescein Transport Assay to Assess Bulk Flow of Molecules Through the Hypocotyl in Arabidopsis thaliana

The bulk transport of molecules through plant tissues underpins growth and development. The stem acts as a conduit between the upper and low domains of the plant, facilitating transport of solutes and water from the roots to the shoot system, and sugar plus other elaborated metabolites towards the non-photosynthetic organs. In order to perform this function efficiently, the stem needs to be optimized for transport. This is achieved through the formation of vasculature that connects the whole plant but also through connectivity signatures that reduce path length distributions outside the vascular system. This protocol was devised to characterize how cell connectivity affects the bulk flow of molecules traversing the stem. This is achieved by exposing young seedlings to fluorescein, for which no specific transporter is assumed to be present in A. thaliana, and assessing the relative concentration of this fluorescent compound in individual cells of the embryonic stem (hypocotyl) using confocal microscopy and quantitative 3D image analysis after a given exposure time.

Control of signaling molecule range during developmental patterning

Tissue patterning, through the concerted activity of a small number of signaling pathways, is critical to embryonic development. While patterning can involve signaling between neighbouring cells, in other contexts signals act over greater distances by traversing complex cellular landscapes to instruct the fate of distant cells. In this review, we explore different strategies adopted by cells to modulate signaling molecule range to allow correct patterning. We describe mechanisms for restricting signaling range and highlight how such short-range signaling can be exploited to not only control the fate of adjacent cells, but also to generate graded signaling within a field of cells. Other strategies include modulation of signaling molecule action by tissue architectural properties and the use of cellular membranous structures, such as signaling filopodia and exosomes, to actively deliver signaling ligands to target cells. Signaling filopodia can also be deployed to reach out and collect particular signals, thereby precisely controlling their site of action.

3D Cell Culture: An Introduction

3D cell culture is an invaluable tool in developmental, cell, and cancer biology. By mimicking crucial features of in vivo environment, including cell-cell and cell-extracellular matrix interactions, 3D cell culture enables proper structural architecture and differentiated function of normal tissues or tumors in vitro. Thereby 3D cell culture realistically models in vivo tissue conditions and processes, and provides in vivo like responses. Since its early days in the 1970s, 3D cell culture has revealed important insights into mechanisms of tissue homeostasis and cancer, and accelerated translational research in cancer biology and tissue engineering.

α-Spectrin and integrins act together to regulate actomyosin and columnarization, and to maintain a monolayered follicular epithelium

The spectrin cytoskeleton crosslinks actin to the membrane, and although it has been greatly studied in erythrocytes, much is unknown about its function in epithelia. We have studied the role of spectrins during epithelia morphogenesis using the Drosophila follicular epithelium (FE). As previously described, we show that α-Spectrin and β-Spectrin are essential to maintain a monolayered FE, but, contrary to previous work, spectrins are not required to control proliferation. Furthermore, spectrin mutant cells show differentiation and polarity defects only in the ectopic layers of stratified epithelia, similar to integrin mutants. Our results identify α-Spectrin and integrins as novel regulators of apical constriction-independent cell elongation, as α-Spectrin and integrin mutant cells fail to columnarize. Finally, we show that increasing and reducing the activity of the Rho1-Myosin II pathway enhances and decreases multilayering of α-Spectrin cells, respectively. Similarly, higher Myosin II activity enhances the integrin multilayering phenotype. This work identifies a primary role for α-Spectrin in controlling cell shape, perhaps by modulating actomyosin. In summary, we suggest that a functional spectrin-integrin complex is essential to balance adequate forces, in order to maintain a monolayered epithelium.

The unique polarity phenotype of hepatocytes

Hepatocytes, the main epithelial cell type of the liver, function like all epithelial cells to mediate the vectorial flow of macromolecules into and out of the organ they encompass. They do so by establishing polarized surface domains and by restricting paracellular flow via their tight junctions and cell-cell adhesion. Yet, the cell and tissue organization of hepatocytes differs profoundly from that of most other epithelia, including those of the digestive and urinary tracts, the lung or the breast. The latter form monolayered tissues in which the apical domains of individual cells align around a central continuous luminal cavity that constitutes the tubules and acini characteristic of these organs. Hepatocytes, by contrast, form capillary-sized lumina with multiple neighbors resulting in a branched, tree-like bile canaliculi network that spreads across the liver parenchyme. I will discuss some of the key molecular features that distinguish the hepatocyte polarity phenotype from that of monopolar, columnar epithelia.

The need for complex 3D culture models to unravel novel pathways and identify accurate biomarkers in breast cancer

The recent cataloging of the genomic aberrations in breast cancer has revealed the diversity and complexity of the disease at the genetic level. To unravel the functional consequences of specific repertoires of mutations and copy number changes on signaling pathways in breast cancer, it is crucial to develop model systems that truly recapitulate the disease. Here we discuss the three-dimensional culture models currently being used or recently developed for the study of normal mammary epithelial cells and breast cancer, including primary tumors and dormancy. We discuss the insights gained from these models in regards to cell signaling and potential therapeutic strategies, and the challenges that need to be met for the generation of heterotypic breast cancer model systems that are amenable for high-throughput approaches.

Tissue architecture, feedback regulation, and resilience to viral infection

Tissue homeostasis is one of the central requirements for the existence of multicellular organisms, and is maintained by complex feedback regulatory processes. Homeostasis can be disturbed by diseases such as viruses and tumors. Here, we use mathematical models to investigate how tissue architecture influences the ability to maintain tissue homeostasis during viral infections. In particular, two different tissue designs are considered. In the first scenario, stem cells secrete negative feedback factors that influence the balance between stem cell self-renewal and differentiation. In the second scenario, those feedback factors are not produced by stem cells but by differentiated cells. The model shows a tradeoff. If feedback factors are produced by stem cells, then a viral infection will lead to a significant reduction in the number of differentiated cells leading to tissue pathology, but the number of stem cells is not affected at equilibrium. In contrast, if the feedback factors are produced by differentiated cells, a viral infection never reduces the number of tissue cells at equilibrium because the feedback mechanism compensates for virus-induced cells death. The number of stem cells, however, becomes elevated, which could increase the chance of these stem cells to accumulate mutations that can drive cancer. Interestingly, if the virus interferes with feedback factor production by cells, uncontrolled growth can occur in the presence of the virus even in the absence of genetic lesions in cells. Hence, the optimal design would be to produce feedback factors by both stem and differentiated cells in quantities that strike a balance between protecting against tissue destruction and stem cell elevation during infection.

Can cell mortality determine division of labor in tissue organization?

Tissue organization comes from the emergence of cell cooperation where cell homeostasis and function are performed as a trade-off of two excluding proliferative and differentiated cellular states. By introducing function in a population dynamics approach, I study the role of division of labor in tissue optimality when cell turn-over and limitation of space and resources are imposed as natural restrictions of a living tissue. The results indicate that although cell turn-over imposes a inevitable reduction in function abilities, the penalty is smaller when division of labor is at work, especially when a rapid cell-turnover and high cell density is a requirement for the tissue, as occurred in epithelia hierarchical tissues. Analytic results are in agreement with the experimental data available in literature. The study provides an explanation about why homogeneous tissues for which proliferative and functional tasks are performed by a same cell type are unlikely to be observed under high cell-renewal requirements.