Biology subjects

Di Russo, J.

Publications and source records attributed to Di Russo, J..

6 recordsLinked to original sources

bioRxiv2025

Microgels enable iPSCs to assemble, expand, and differentiate into organoids -- from sizable to high throughput

Organoid research holds tremendous potential for personalized medicine and drug development. However, current limitations include reproducibility issues largely due to the use of biologically derived materials, which are prone to batch-to-batch variations. Here, we report a new technology for human induced pluripotent stem cell (iPSC)-based organoid production with iPSC expansion and differentiation in the same construct in a reproducible and scalable manner, compatible with high-throughput automation. Chemically defined poly(ethylene glycol) (PEG)-based microgels are produced via parallelized step-emulsification microfluidics, enabling scalable production. This approach leverages the self-organization of iPSCs with microgels to build three-dimensional constructs, driven by robust cell-material interactions achieved through vitronectin-coated PEG microgels. This technology allows the iPSCs to expand and retain their pluripotency, after which they can be differentiated into the three germ layers, providing a suitable platform for organoid differentiation. This was further extended by differentiation into cardiac organoids and retinal photoreceptors to demonstrate two exemplary tissues.

bioengineering↗

bioRxiv2025

Photodegradable Hydrogels for On-Demand Modeling of Age-Related Spatiotemporal ECM Deformation

The extracellular matrix (ECM) plays a crucial role in regulating tissue behavior through a dynamic interplay of spatial and temporal cues. Dynamic materials capable of modulating these cues at relevant scales are essential for tackling current challenges in tissue engineering and addressing fundamental biological questions. In vision research, there is a notable lack of suitable in vitro systems to study ECM dynamics. To help fill this gap, we developed an easy-to-use, photosensitive poly(ethylene glycol)-based hydrogel that can deform on demand to simulate ECM bulging, known as drusen, associated with the aging of the outer retina. Our findings demonstrate that variations in the size of these artificial drusen during culture impact morphometric parameters of the retinal pigment epithelium, offering new insights into its mechanical resilience to different drusen sizes. Notably, drusen formation in our system does not significantly affect the cellular actin cytoskeleton or polarity, which are often disrupted in conventional acute substrate deformation models, allowing the study of early aging before detectable pathology. In summary, we present a light-tunable hydrogel platform that enables precise spatial mimicry of ECM topographical changes, offering a promising tool for investigating the mechanobiological aspects of dynamic cell-matrix interactions.

bioengineering↗

bioRxiv2025

Age-associated Tissue Organisation Shifts Retinal Pigment Epithelium Actomyosin Plasticity in Phagocytosis

Tissue homeostasis relies on mechanical feedback loops balanced by cell loss and proliferation. However, maintaining this balance becomes particularly challenging in postmitotic tissues, where alternative mechanisms replace compensatory proliferation. In the postmitotic retinal pigment epithelium (RPE), these mechanisms include significant structural adaptations over time. Yet, how these adaptations relate to epithelial mechanical homeostasis and age-associated functional decline remains poorly understood. To establish the relationship between structural changes, mechanical homeostasis and function, we developed an in vitro reductionistic model mimicking age-related reduction in RPE cell density. Inducing large-scale apoptosis in postmitotic stem cell-derived RPE monolayers recapitulates structural hallmarks of aged tissue, such as reduced cell height, shortened microvilli and cytoskeletal reorganisation. This new structure acquires a new mechanical equilibrium, evidenced by tissue stiffening and enhanced junctional contractility. Functionally, the monolayers display impaired vision-supporting phagocytosis of photoreceptor outer segments. Mechanistically, modulation of actin nucleators, Arp2/3 and formins, demonstrates that apicolateral monolayer deformation is critical for phagocytosis and may be compromised in aged RPE. Our findings suggest that a shift in mechanical homeostasis due to cell loss is a major driver of age-related RPE functional decline. Importantly, we show that structural remodelling in ageing alone can compromise tissue function, independent of other stressors.

cell biology↗

bioRxiv2023

Laminin alpha 5 - induced mechanical homeostasis modulates retinal epithelium functionality

Epithelial cells are highly interconnected, whereby they acquire mesoscale mechanical properties to accomplish specific tissue functions. In homeostasis, this mechanical status can be summarised as mechanical homeostasis, regulated by the balance of intercellular tension and extracellular matrix adhesion forces. In the outer retina, the significance of this force balance and its consequences for vision remains poorly understood. We found that the density of basement membrane laminins modulates the level of retinal pigmented epithelium contractility, which directly controls its efficiency in phagocytosing photoreceptor outer segments. In vivo, the density gradient of laminins follows retinal functional demand, supporting the physiological role of laminins in controlling epithelial mechanical homeostasis. Our data suggest that laminin density and isoform heterogeneity can differentially engage integrins {beta}1 and {beta}4, the ratio of which determines the contribution of actin vs keratin cytoskeleton in balancing tissue mechanics. With this work, we suggest that the extracellular matrix-defined mechanical status of retinal pigmented epithelium is a novel parameter for visual function. SignificanceIn the retina, the retinal pigmented epithelium (RPE) is responsible for the daily phagocytosis of photoreceptor cell fragments, a process vital for visual function. Along the visual axis, there is a natural decrease in the ratio of photoreceptors to RPE cells, indicating a decrease in RPE functional demand. This study reveals that the density of laminins in RPE basement membrane also diminishes along this axis, critically influencing RPE function by regulating its contractility. For the first time, we demonstrate the presence of a laminin- defined mechanical gradient within the RPE, which determines its capacity to support photoreceptor cells. Our findings highlight the importance of mechanical properties as a key factor in visual function, offering new insights into retinal health and disease.

biophysics↗

bioRxiv2021

Quantitative Mapping of Keratin Networks in 3D

Mechanobiology requires precise quantitative information on processes taking place in specific 3D microenvironments. Connecting the abundance of microscopical, molecular, biochemical and cell mechanical data with defined topologies has turned out to be extremely difficult. Establishing such structural and functional 3D maps needed for biophysical modeling is a particular challenge for the cytoskeleton, which consists of long and interwoven filamentous polymers coordinating subcellular processes and interactions of cells with their environment. To date, useful tools are available for the segmentation and modeling of actin filaments and microtubules but comprehensive tools for the mapping of intermediate filament organization are still lacking. In this work, we describe a workflow to model and examine the complete 3D arrangement of the keratin intermediate filament cytoskeleton in epithelial cells both in vitro and in vivo. Numerical models are derived from super resolution 3D imaging of fluorescence-tagged keratin filaments. They are interrogated and annotated at different length scales using different modes of visualization including immersive virtual reality. In this way, information is provided on network organization at the subcellular level including mesh arrangement, density and isotropic configuration as well as details on filament morphology such as bundling, curvature and orientation. We show that the comparison of these parameters helps to identify, in quantitative terms, similarities and differences of keratin network organization in epithelial cell types defining subcellular domains, notably basal, apical, lateral and perinuclear systems. The described approach and the presented data are pivotal for generating mechanobiological models that can be experimentally tested.

cell biology↗

bioRxiv2021

Integrin α5β1 nano-presentation regulates collective keratinocyte migration independent of substrate rigidity

Nanometer-scale properties of the extracellular matrix influence many biological processes, including cell motility. While much information is available for single cell migration, to date, no knowledge exists on how the nanoscale presentation of extracellular matrix receptors influences collective cell migration. In wound healing, basal keratinocytes collectively migrate on a fibronectin-rich provisional basement membrane to re-epithelialize the injured skin. Among other receptors, the fibronectin receptor integrin 5{beta}1 plays a pivotal role in this process. Using a highly specific integrin 5{beta}1 peptidomimetic combined with nanopatterned hydrogels, we show that keratinocyte sheets regulate their migration ability at an optimal integrin 5{beta}1 nanospacing. This efficiency relies on the effective propagation of stresses within the cell monolayer independent of substrate stiffness. For the first time, this work highlights the importance of extracellular matrix receptor nanoscale organization required for efficient tissue regeneration.

biophysics↗