Biology subjects

Mendonca, T.

Publications and source records attributed to Mendonca, T..

7 recordsLinked to original sources

bioRxiv2025

Hybrid Scaffolds Decouple Biochemical & Biophysical Regulation of Cell Phenotype

The extracellular matrix changes dramatically during the progression of diseases like cancer. These complex, tissue-specific changes are not adequately replicated by most current biomaterial disease models. Here we demonstrate, for the first time, a biomaterial system allowing combined, independent control over stiffness, composition and 3D collagen architecture. We demonstrate successful perfusion of defined hydrogel formulations into ice-templated collagen scaffolds, controlling the composition of these hybrid scaffolds at constant stiffness. The Youngs moduli of these hybrid scaffolds can also be tuned independently of composition via chemical crosslinking. Encapsulation of human dermal fibroblasts reveals that fibroblast morphology depends on hybrid scaffold composition and on viscoelasticity, highlighting the importance of a system that decouples biophysical from biochemical properties. Finally, we demonstrate application of this system to exert combined control over biochemical and biophysical drivers of cell growth and invasion, focussing on breast cancer as proof-of-concept. We show that collagen fibre patterning enhances breast cancer cell proliferation, also directing the invasion of patient-derived breast cancer cells. These hybrid scaffolds are therefore promising new tools for dissecting the diverse but complementary roles played by the extracellular matrix in regulating cell phenotype, in a range of healthcare applications.

bioengineering↗

bioRxiv2024

The mitotic chromosome periphery: a fluid coat that mediates chromosome mechanics

Mitotic chromosomes are specialised packets of condensed genetic material with dynamic mechanical properties. Each chromosome is coated by a sheath of proteins and RNA, called the mitotic chromosome periphery (MCP). The MCP is widely considered as an essential chromosome compartment where its multiple functions bestow material properties important for successful cell division. However, the details of the micromechanical properties of mitotic chromosomes, and specifically if and how the MCP contributes to these features, remain poorly understood. In this study, we present the most comprehensive characterisation of single-chromosome mechanics to date spanning a broadband frequency range, using optical tweezers and a novel microrheology technique. We extend this analysis to the first direct measurements of MCP micromechanics by manipulating levels of Ki-67, the chief organiser of this compartment, and apply a rheological model to isolate its contribution to chromosome dynamics. We report that the MCP governs high-frequency self-reorganisation dynamics and acts as a structural constraint, providing force-damping properties that mitigate mitotic stress. This work significantly advances our understanding of chromosome micromechanics and how the MCP contributes to the fundamental properties of chromosomes.

biophysics↗

bioRxiv2024

The Chromosome Periphery is an Essential Compartment of Oocyte Chromosomes

Chromosomes and their constituent compartments are core elements of the cell division machinery. In mammalian oocytes, defects in the structure or composition of chromosomes are a leading cause of aberrant or failed meiosis, and by extension, can cause miscarriage and infertility. The underlying mechanisms are poorly understood, but are critical for development of novel diagnostics and treatments. The chromosome periphery, the least understood chromosome compartment, has recently emerged as an essential component of mitotic chromosomes and somatic cell division. However, in female meiosis it remains completely unexplored. This study provides the first comprehensive survey of a meiotic chromosome periphery compartment in both human and mouse oocytes. Using a combination of time-lapse microscopy, super-resolution imaging and 3DCLEM we show that removing the chromosome periphery, via Ki67 depletion, has substantial negative impact on chromosome structure, spatial organization and positional awareness, with many oocytes stalling and arresting in meiosis I. Importantly, we also reveal key differences between the mitotic and oocyte meiotic chromosome periphery compartments, most remarkably in the retention of Ki67 in the oocyte through anaphase I, where unwanted chromosomes are stripped of Ki67 before being ejected from the oocyte. This work presents the discovery of an exciting new pathway operating during female meiosis and a provides a platform for future work exploring the meiotic chromosome periphery for therapeutic vulnerabilities.

cell biology↗

bioRxiv2022

OptoRheo: Simultaneous in situ micro-mechanical sensing and 3D imaging of live cell cultures

Biomechanical cues from the extracellular matrix (ECM) are essential for directing many cellular processes, from normal development and repair, to disease progression. To better understand cell-matrix interactions, we have developed a new instrument named OptoRheo that combines light sheet fluorescence microscopy with particle tracking microrheology. OptoRheo lets us image cells in 3D as they proliferate over several days while simultaneously sensing the mechanical properties of the surrounding extracellular and pericellular matrix at a sub-cellular length scale. OptoRheo can be used in two operational modalities (with and without an optical trap) to extend the dynamic range of microrheology measurements. We corroborated this by characterising the ECM surrounding live breast cancer cells in two distinct culture systems, cell clusters in 3D hydrogels and spheroids in suspension culture. This cutting-edge instrument will transform the exploration of drug transport through complex cell culture matrices and optimise the design of the next-generation of disease models.

bioengineering↗

bioRxiv2021

Origami: Single-cell oriented 3D shape dynamics of folding epithelia from fluorescence microscopy images

A common feature of morphogenesis is the formation of three-dimensional structures from the folding of two-dimensional epithelial sheets aided by spatio-temporal cell shape changes at the cellular-level. Studying cell shape dynamics and polarised processes that underpin them, requires orienting cells within the epithelial sheet. In epithelia with highly curved surfaces, assigning cell orientation can be difficult to automate in silico. We present Origami, a MATLAB-based image analysis pipeline to compute oriented cell shape-features. Our automated method accurately computed cell orientation in regions with opposing curvature in synthetic epithelia and fluorescence images of zebrafish embryos. As proof of concept, we identified different cell shape signatures in the developing zebrafish inner ear, where the epithelium deforms in opposite orientations to form different structures. Origami is designed to be user-friendly and is generally applicable to fluorescence images of curved epithelia.

developmental biology↗

bioRxiv2020

Microrheology reveals microscale viscosity gradients in planktonic systems

Microbial activity in planktonic systems creates a dynamic and heterogeneous microscale seascape that harbours a diverse community of microorganisms and ecological interactions of global significance. In recent decades a great effort has been put into understanding this complex system, particularly focusing on the role of chemical patchiness, while overlooking a physical parameter that governs microbial life and is affected by biological activity: viscosity. Here we use microrheological techniques to measure viscosity at length scales relevant to microorganisms. Our results reveal the viscous nature and the spatial extent of the phycosphere, the microenvironment surrounding phytoplankton cells, and show heterogeneity in viscosity at the microscale. Such heterogeneity affects the distribution of chemicals and microorganisms, with pervasive and profound implications for the functioning of the planktonic ecosystem. One Sentence SummaryMicrorheology measurements unveil the existence of layers of increased viscosity surrounding phytoplankton cells and within aggregates.

ecology↗

bioRxiv2018

Sperm gatekeeping: 3D imaging reveals a constricted entrance to zebra finch sperm storage tubules

Females across many internally fertilising taxa store sperm, often in specialised storage organs in their reproductive tracts. In birds, several hundred sperm storage tubules exist in the utero-vaginal junction of the oviduct and there is growing evidence that sperm storage in these tubules is selective. The mechanisms underlying female sperm storage in birds remain unknown due to our limited ability to make three dimensional, live observations inside the large, muscular avian oviduct. Here, we describe a new application of fluorescence selective plane illumination microscopy to optically section oviduct tissue from zebra finch Taeniopygia guttata females label-free, by harnessing tissue autofluorescence. Our data provide the first description of the 3D structure of sperm storage organs in any vertebrate and reveal the presence of gate-like constricted openings that may play a role in sperm selection.\n\nStatement of SignificanceFemale birds can store sperm in microscopic tubular structures in their reproductive tract for up to several months, depending on species. Studying these sperm storage tubules has been a major challenge due to the muscular and opaque nature of reproductive tracts in birds. We have developed a new method for imaging live reproductive tract tissue using selective plane illumination microscopy, a fluorescence microscopy technique. From these images, we could extract three-dimensional measurements of sperm storage tubules and found these structures to have a gate-like constriction, providing evidence that females can actively select sperm at storage and ultimately influence the paternity of her offspring. Understanding these reproductive adaptations can help improve captive breeding programs and similar conservation strategies.

evolutionary biology↗