Biology subjects

Levenberg, S.

Publications and source records attributed to Levenberg, S..

5 recordsLinked to original sources

bioRxiv2024

Shape that matters: Yolk geometry spatially modulates developing vascular networks within chick chorioallantoic membrane

Controlling the multiscale organization of vasculature within diverse geometries is essential for shaping tissue-specific and organ-specific architectures. Nevertheless, how geometrical characteristics of surrounding tissues influence vessel morphology and blood flow remains unclear. Where the regulation of vascular organization by mechanical signals associated with fluid flow is well known, this study postulates that the organization of developing vasculature can also be regulated by mechanical signals connected to the confinement and thus the deformation of surrounding tissues. To test the Shape-Induced Vascular Adaptation (SIVA) concept, fertilized chicken egg contents containing developing vasculature were cultured within engineered eggshell platforms of different shapes. Our findings demonstrate that the vascularized chick chorioallantoic membrane (CAM) adapts to the shape of engineered eggshell, long before reaching its boundaries. This adaptation affects the organization of the vascular network within the CAM, affecting parameters such as vessel area, branching, orientation, length, diameter and endpoints. Specifically, we observed that sharp corners in the engineered eggshell led to more elongated vascular structures. To further explore the dynamic nature of this phenomenon, a proof-of-concept experiment was performed using a shape-shifting engineered eggshell that deforms the egg content from circle to square shape. Using this shape-shifting prototype, we observed a direct effect of eggshell deformation on the vessel morphology and flow dynamics in a time-dependent manner. Overall, our exovo experimental platform provides a unique opportunity to study how mechanical stimuli such as shape influence the spatial and temporal organization of developing vascularized tissues. By subjecting these tissues to various static and dynamic conditions, we induced both local and global changes in their organization. This class of perturbation provides us with an additional tool which can be used for shaping vascular organization within developing tissues and to engineer tissues with geometrically tunable vessel structures.

bioengineering↗

bioRxiv2024

Quantitative Image Analysis of Tissue Properties: A MATLAB Tool for Measuring Morphology and Co-localization in 2D Images

In recent years, the structural analysis of tissue elements has gained significant importance in biomedical research. Advancements in imaging technologies have created a pressing need to quantify tissue and cell properties accurately. This paper introduces a MATLAB-based analytical tool designed to measure a spectrum of properties from 2D images of tissues and cells. Our software efficiently computes parameters such as eccentricity, orientation, density, co-localization, size, and perimeter. The algorithms precision in evaluating these characteristics has broad implications for enhancing the understanding of various biological processes and diseases. The codes flexibility allows for application across different tissue types and experimental conditions, providing researchers with a robust method for quantitative analysis. This advancement in computational image analysis represents a pivotal step towards more detailed and objective assessment in tissue engineering and cellular biology.

bioengineering↗

bioRxiv2022

Single cell transcriptomic comparison between mouse embryonic pancreas and pancreatic organoids generated from mouse embryonic stem cell-derived mesoderm and pancreatic progenitors

The developing mouse pancreas is surrounded by mesoderm compartments providing signals that induce pancreas formation. Most pancreatic organoid protocols lack this mesoderm niche and only partially capture the pancreatic cell repertoire. This work aimed to generate pancreatic aggregates by differentiating mouse embryonic stem cells (mESCs) into mesoderm progenitors (MPS) and pancreas progenitors (PPs), without using extracellular matrix substitutes. First, mESCs were differentiated into epiblast stem cells (EpiSCs) to enhance the PP differentiation rate. Next, PPs and MPs aggregated together giving rise to various pancreatic cell types, including endocrine, acinar, and ductal cells, and to endothelial cells. Single-cell RNA sequencing analysis revealed a larger endocrine population within the PP+MP aggregates, as compared to PPs alone or PPs in Matrigel aggregates. The PP+MP aggregate gene expression signatures and its endocrine population percentage closely resembled those of the endocrine population found in the mouse embryonic pancreas, which holds promise for studying pancreas development.

developmental biology↗

bioRxiv2021

Development of a 3D atlas of the embryonic pancreas for topological and quantitative analysis of heterologous cell interactions

Generating comprehensive image maps, while preserving spatial 3D context, is essential to quantitatively assess and locate specific cellular features and cell-cell interactions during organ development. Despite the recent advances in 3D imaging approaches, our current knowledge of the spatial organization of distinct cell types in the embryonic pancreatic tissue is still largely based on 2D histological sections. Here, we present a light-sheet fluorescence microscopy approach to image the pancreas in 3D and map tissue interactions at key development time points in the mouse embryo. We used transgenic mouse models and antibodies to visualize the three main cellular components within the developing pancreas, including epithelial, mesenchymal and endothelial cell populations. We demonstrated the utility of the approach by providing volumetric data, 3D distribution of distinct progenitor populations and quantification of relative cellular abundance within the tissue. Lastly, our image data were combined in an open source online repository (referred to as Pancreas Embryonic Cell Atlas). This image dataset will serve the scientific community by enabling further investigation on pancreas organogenesis but also for devising strategies for the in vitro generation of transplantable pancreatic tissue for regenerative therapies.

developmental biology↗

bioRxiv2020

Integrating Engineered Macro Vessels with Self-assembled Capillaries in 3D Implantable Tissue for Promoting Vascular Integration In-vivo

Fabrication of a functional hierarchical vascular network remains an unmet need for cultivation and transplantation of 3D engineered tissues. In this work, an effective approach was developed to fabricate a functional, perfusable and biocompatible, multi-scale vascular network (MSVT) within thick, implantable engineered tissues. Using a templating technique, macro-vessels were patterned in a 3D biodegradable polymeric scaffold seeded with endothelial and support cells within a collagen gel. The lumen of the macro-vessel was lined with endothelial cells, which further sprouted and anastomosed with the surrounding self-assembled capillaries. Anastomoses between the two-scaled vascular systems displayed tightly bonded cell junctions, as indicated by vascular endothelial cadherin expression. Moreover, MSVT functionality and patency were demonstrated by dextran passage through the interconnected hierarchical vasculature. Additionally, physiological flow conditions were applied with home-designed flow bioreactors, to achieve a MSVT with a natural endothelium structure. Finally, implantation of a multi-scale-vascularized graft in a mouse model resulted in a clear beneficial effect, as reflected by extensive host vessel penetration into the graft and an increase in blood perfusion via the engineered vessels as compared to control microscale-vascularized graft. Designing and fabricating such multi-scale vascular architectures within 3D engineered tissues is essential, both for in-vitro models and for therapeutic translation research.

bioengineering↗