Wacker, I. | Search bioRxiv

bioRxiv2026

Enzyme-functionalized microparticles to open the vitreoretinal interface

The transport of therapeutics and gene carriers to their site of action is often hindered by biological barriers, such as cell layers and basement membranes. Among these, the inner limiting membrane (ILM) represents a major barrier within the eye, separating the vitreous body from the retina. The ILM must be crossed, if for instance gene carriers are to reach retinal target cells following intravitreal administration. However, the ILM is a densely cross-linked basement membrane barrier, allowing only the smallest nanoparticles to pass. Here, we demonstrate that active micro-colloids decorated with enzymes can locally open the ILM and thereby facilitate the diffusion of passive carriers into retinal tissue. We utilize an ex vivo porcine eye model to determine the membrane permeability threshold using fluorescent nanoprobes. We further show that collagenase-decorated silica microparticles can facilitate the transport of nanoparticles, while exhibiting excellent biocompatibility with no adverse morphological or functional retinal effects over a six-week in vivo evaluation in a porcine model. Overall, our findings introduce a biocompatible and minimally invasive strategy to facilitate the targeted nanoparticle transport across biological barriers, which we demonstrate for retinal delivery enabled by active colloids.

bioengineering↗

bioRxiv2025

Extrinsic polarity cues control lamination versus cluster-based organisation in vertebrate retinal development

1.Photosensitive organs are essential for most animals to perceive and respond to their environment. While the gene regulatory networks establishing retinal identity are deeply conserved across metazoans (reviewed in Gehring, 2012; Vopalensky & Kozmik, 2009; Hahn et al., 2023), the retinal architecture varies widely--from invertebrate compound eyes to vertebrate camera-type eyes (Lamb et al., 2007; Schwab, 2017; Arendt & Wittbrodt, 2001). Despite this morphological diversity, early eye anlagen in both, invertebrates and vertebrates, share an initial pseudo-stratified epithelial organization (Weasner & Kumar, 2022; Randlett et al., 2010; Das et al., 2003; Kitambi & Malicki, 2008), which is maintained and elaborated into multi-layered retinae in vertebrates. In contrast, the invertebrate neuroepithelium is re-organized as ommatidia develop. Laminar organisation of the vertebrate retina appears to be a consequence of initial polarisation of the retinal neuroepithelium. This is, however, challenging to test in the organismal context. To address the plasticity of retinal architecture and the impact of epithelial polarity on the structuring of retinal tissue, we take advantage of retinal organoids derived from medaka (Oryzias latipes) (Zilova et al., 2021) that allow to modulate polarity cues and test their impact on the level of epithelialization and structural organisation of the forming retina. We show that under specific culture conditions, medaka retinal organoids undergo a striking morphological switch depending on the level of apico-basal polarity imposed. When polarity cues are continuously provided, a laminated retinal epithelium is established in the organoid. The absence of polarity cues results in the formation of horizontal cellular clusters containing the retinal cell types, which form the vertical retinal column in the developing embryo. We demonstrate that the emergence of this alternative retinal architecture is associated with a loss of epithelial polarity, notably the absence of extracellular matrix (ECM) components, such as laminin, which efficiently rescues lamination. Our findings indicate that tissue-level polarization and lamination in vertebrate retinae require specific extrinsic cues, and that in their absence, differentiating retinal cell types self-organize into structurally distinct, retinal units. This reveals an unexpected plasticity in vertebrate retinal development and indicates a potential for alternative modes of retinal patterning. O_FIG O_LINKSMALLFIG WIDTH=155 HEIGHT=200 SRC="FIGDIR/small/688026v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@100bb1eorg.highwire.dtl.DTLVardef@fceb9borg.highwire.dtl.DTLVardef@d036a7org.highwire.dtl.DTLVardef@1b41483_HPS_FORMAT_FIGEXP M_FIG C_FIG Retinal cells in medaka organoids adopt either a continuous layered epithelium when supported by laminin or a unit-based, ommatidia-like organization when epithelial continuity is lost. This dual outcome suggests that epithelial integrity represents a branching point between vertebrate and invertebrate strategies of retinal patterning, providing an experimental system to replay alternative evolutionary trajectories of eye design.

developmental biology↗

bioRxiv2024

Integrative Imaging of Lung Micro Structure: Amplifying Classical Histology by Paraffin Block μCT and same-slide Scanning Electron Microscopy

Classical histopathology of formalin fixed and paraffin embedded (FFPE) tissue using light microscopy (LM) remains the undisputed gold standard in biomedical microstructural lung tissue analysis. To extend this method, we developed an integrative imaging and processing pipeline which adds 3D context and screening capabilities by micro-CT (CT) imaging of the entire paraffin block and adds ultrastructural information by correlative same-slide scanning electron microscopy (SEM). The different modalities are integrated by elastic registration to provide hybrid image datasets. Without compromising standard light microscopic readout, we overcome the limitations of conventional histology by combining and integrating several imaging modalities. The biochemical information contained in histological and immunohistological tissue staining is embedded into the 3D tissue configuration and is amplified by adding ultrastructural visualization of features of interest. By combining CT and conventional histological processing, specimens can be screened, and specifically preselected areas of interest can be targeted in the subsequent sectioning process. While most of the CT data shown in the manuscript was acquired at a Synchrotron, we further demonstrate that our workflow can also by applied using X-ray microscopy.

pathology↗