Biology subjects

Winkel, A.

Publications and source records attributed to Winkel, A..

6 recordsLinked to original sources

bioRxiv2026

Resilience of multispecies biofilm communities: Comparative analysis of a Veillonella dispar-dominant oral biofilm under diverse oxygen conditions in vitro

Oral multispecies biofilms developing on dental implants drive peri-implant mucositis and peri-implantitis. They are shaped by the physicochemical conditions of their surrounding environment, among which oxygen availability is an important influential factor. However, while oxygen tension fluctuates significantly within the peri-implant pocket, whether these environmental shifts are sufficient to influence the structure and composition of an established microbial community remains unclear. For this purpose, we evaluated the structure and composition of a four-species oral biofilm model comprising the species Streptococcus oralis, Actinomyces naeslundii, Veillonella dispar and Porphyromonas gingivalis, which was cultivated under normoxic (21% O2), hypoxic (1% O2) and anoxic (0% O2;) conditions for a period of 21 days. Biofilm 3D architecture, volume and membrane integrity was analyzed by LIVE/DEAD staining combined with confocal laser scanning microscopy. Community composition was assessed by quantitative real-time PCR and complemented by Fluorescence In Situ Hybridization (FISH) to provide structural context. While normoxia transiently promoted higher early biofilm volume and membrane integrity, the community exhibited remarkable long-term resilience, consistently maintaining a V. dispar-dominated structure across all oxygen gradients. Crucially, the obligate anaerobic pathogen P. gingivalis persisted as a viable minority (~1%) even under 21-day normoxic cultivation, sheltered within the deeper layers of the biofilm. These results suggest that clinical oxygen levels alone are not able to drastically modulate established oral biofilm communities and that oxygen-sensitive pathogens persist in a subclinical sanctuary protected by the surrounding non-pathogenic species.

microbiology↗

bioRxiv2024

Hyaluronic Acid and Emergent Tissue Mechanics Orchestrate Digit Tip Regeneration

Tissue regeneration is a dynamic process requiring coordinated cell fate decisions to restore structure and function. For instance, the tips of human and rodent digits fully regrow after amputation, although more proximal injuries fail to regenerate. While biochemical cues have been widely studied in wound healing, the role of the physical microenvironment remains less understood. Here, we discovered that tissue mechanics and extracellular matrix (ECM) composition differ markedly between non-regenerating and regenerating wounds. These differences are due to specific fibroblast sub-types which predominate in the non-regenerating wound and form fibrotic collagen networks. Conversely, bone-forming progenitors in regenerating digits synthesize abundant hyaluronic acid, which mediates collagen fibrillogenesis. By modeling the tissue mechanics of non-regenerative and regenerative wounds using hydrogels, we showed that substrate stiffness regulates the synthesis of fibrotic and regenerative ECM. We further revealed that mimicking the regenerative wound mechanics upregulated bone morphogenic protein signaling and osteogenic differentiation. We ultimately demonstrated that the link protein HAPLN1 promotes hyaluronic acid deposition in vivo, reduces scar formation, and induces bone repair after non-regenerative amputations. These findings emphasize the interplay among the ECM, tissue mechanics, and cell behavior in digit regeneration and point towards ECM modulation as a strategy to improve wound healing. HighlightsO_LINon-regenerating and regenerating digit tips diverge in their cellular and ECM composition C_LIO_LIRegeneration requires hyaluronic acid matrix, which mediates collagen assembly and tissue mechanics C_LIO_LISoft substrates enhance BMP signaling and propagate the synthesis of regenerative ECM C_LIO_LIHAPLN1 overexpression initiates rescue of non-regenerative digit tip amputations C_LI

developmental biology↗

bioRxiv2024

Differential tissue deformability underlies shape divergence of the embryonic brain and spinal cord under fluid pressure

An expanded brain enables the complex behaviours of vertebrates that promote their adaptation in diverse ecological niches1-3. Initial morphological differences between the brain and spinal cord emerge as the antero-posteriorly patterned neural plate folds to form the neural tube4-7 during embryonic development. Following neural tube closure, a dramatic expansion of the brain diverges its shape from the spinal cord8, setting their distinct morphologies for further development9,10. How the brain and the spinal cord expand differentially remains unclear. Here, using the chicken embryo as a model, we show that the hindbrain expands through dorsal tissue thinning under a positive hydrostatic pressure from the neural tube lumen11,12 while the dorsal spinal cord shape resists the same pressure. Using magnetic droplets and atomic force microscopy, we reveal that the dorsal tissue in the hindbrain is more fluid than in the spinal cord. The dorsal hindbrain harbours more migratory neural crest cells13 and exhibits reduced apical actin and a disorganised laminin matrix compared to the dorsal spinal cord. Blocking the activity of neural crest-associated matrix metalloproteinases inhibited dorsal tissue thinning, leading to abnormal brain morphology. Transplanting early dorsal hindbrain cells to the spinal cord was sufficient to create a region with expanded brain-like morphology including a thinned-out roof. Our findings open new questions in vertebrate head evolution and neural tube defects, and suggest a general role of mechanical pre-pattern in creating shape differences in epithelial tubes.

developmental biology↗

bioRxiv2022

Plakoglobin is a mechanoresponsive regulator of naïve pluripotency

Biomechanical cues are instrumental in guiding embryonic development and cell differentiation. Understanding how these physical stimuli translate into transcriptional programs could provide insight into mechanisms underlying mammalian pre-implantation development. Here, we explore this by exerting microenvironmental control over mouse embryonic stem cells (ESCs). Microfluidic encapsulation of ESCs in agarose microgels stabilized the naive pluripotency network and specifically induced expression of Plakoglobin (Jup), a vertebrate homologue of {beta}-catenin. Indeed, overexpression of Plakoglobin was sufficient to fully re-establish the naive pluripotency gene regulatory network under metastable pluripotency conditions, as confirmed by single-cell transcriptome profiling. Finally, we found that in the epiblast, Plakoglobin was exclusively expressed at the blastocyst stage in human and mouse embryos - further strengthening the link between Plakoglobin and naive pluripotency in vivo. Our work reveals Plakoglobin as a mechanosensitive regulator of naive pluripotency and provides a paradigm to interrogate the effects of volumetric confinement on cell-fate transitions. HighlightsO_LI3D agarose spheres stabilize the naive pluripotency network in mouse ESCs. C_LIO_LIVolumetric confinement induces expression of Plakoglobin, a vertebrate homologue of {beta}-catenin. C_LIO_LIPlakoglobin expression in the epiblast is specific to pre-implantation human and mouse embryos. C_LIO_LIPlakoglobin overexpression maintains naive pluripotency independently of {beta}-catenin. C_LI

developmental biology↗

bioRxiv2020

Robust T-cell signaling triggered on soft polydimethylsiloxane-supported lipid-bilayers

The T-cell receptor (TCR) is thought to be triggered either by mechano-transduction or local tyrosine phosphatase exclusion at cell-cell contacts. However, the effects of the mechanical properties of activating surfaces have only been tested for late-stage T-cell activation, and phosphatase segregation has mostly been studied on glass-supported lipid bilayers that favor imaging but are orders-of-magnitude stiffer than typical cells. We developed a method for attaching lipid bilayers to polydimethylsiloxane polymer supports, producing soft bilayers with physiological levels of mechanical resistance (Youngs modulus of 4 kPa). Comparisons of T-cell behavior on soft and glass-supported bilayers revealed that early calcium signaling is unaffected by substrate rigidity, implying that early steps in TCR triggering are not mechanosensitive. Robust phosphatase exclusion was observed on the soft bilayers, however, suggesting it likely occurs at cell-cell contacts. This work sets the stage for an imaging-based exploration of receptor signaling under conditions closely mimicking physiological cell-cell contact.

biophysics↗

bioRxiv2019

StemBond hydrogels optimise the mechanical microenvironment for embryonic stem cells

Studies of mechanical signalling are typically performed by comparing cells cultured on soft and stiff hydrogel-based substrates. However, it is challenging to independently and robustly control both substrate stiffness and tethering of extracellular matrix (ECM) to substrates, making ECM tethering a potentially confounding variable in mechanical signalling investigations. Moreover, poor ECM tethering can lead to weak cell attachment. To address this, we developed StemBond hydrogels, a hydrogel formulation in which ECM tethering is stable and can be varied independently of stiffness. We show that soft StemBond hydrogels provide an optimal format for culturing embryonic stem (ES) cells. We find that soft StemBond substrates improve the homogeneity of ES cell populations, boost their self-renewal, and increase the efficiency of cellular reprogramming. Our findings underline how soft microenvironments impact mechanosensitive signalling pathways regulating self-renewal and differentiation, indicating that optimising the complete mechanical microenvironment will offer greater control over stem cell fate specification.

cell biology↗