Astrocytes are key components in reactive gliosis after brain injury, yet defined in vitro models dissecting the influence of extracellular matrix components enriched after injury, such as fibrin, on human astrocyte behavior and function are still missing. Here, we use fibrinogen-derived fibrin and fibrin-alginate-RGD (FAR) 3D hydrogel substrates to examine their influence on human induced pluripotent stem cell (hiPSC)-derived astrocyte behavior and on their direct conversion into neurons. Astrocytes develop complex morphologies in 3D-FAR hydrogels, while they are more proliferative and migratory in 3D-fibrin hydrogels (3D-fibrin). Interestingly, gene expression analysis revealed different reactive states of astrocytes in 3D-fibrin and 3D-FAR, which persist over time. The highly inflammatory state and stiffness of 3D-FAR are largely incompatible with direct neuronal reprogramming, hampering the direct conversion even at early stages. Conversely, astrocytes in 3D-fibrin hydrogels can convert into neuronal cells, demonstrating a potent influence of how fibrin is presented on distinct astrocyte states, with great relevance for fate conversion.
Glycan atlassing enables functional tracing of cell state
Dijo Moonnukandathil Joseph,
Nazlican Yurekli,
Sarah Fritsche,
Reem Hashem,
Oana-Maria Thoma,
Imen Larafa,
Tina Boric,
Chloé Bielawski,
Karim Almahayni, et al.
The glycocalyx is a complex layer of glycosylated molecules that surrounds all cells in the human body. It is involved in regulating critical cellular processes, including immune response modulation, cell adhesion and host–pathogen interactions. Despite these insights, the functional relationship between the glycocalyx architecture and cellular state has remained elusive, largely due to the structural diversity of glycocalyx constituents and their nanoscale organization. Here we show that DNA-tagged lectin labelling and metabolic oligosaccharide engineering enable multiplexed super-resolution microscopy of the glycocalyx constituents, yielding an atlas of glycocalyx architecture with nanometre resolution. Quantitative analysis of the obtained nanoscale map of glycocalyx constituents facilitates the extraction of characteristic spatial relationships that accurately report on the cellular state. We demonstrate the capacity of our approach, which we term glycan atlassing, across cell and tissue types, ranging from cultured cell lines to primary immune cells, neurons and primary patient tissue. Glycan atlassing establishes a transformative strategy for investigating glycocalyx remodelling in development and disease, potentially enabling the development of glycocalyx-centred targets in diagnosis and therapy.
Hyaluronic acid and tissue mechanics orchestrate mammalian digit tip regeneration
Byron W. H. Mui,
Joseph J. Y. Wong,
Camille E. Dumas,
Jia Hua Wang,
Toni Bray,
Kentaro Hirose,
Lauren Connolly,
Alexander Winkel,
Sebastian Timmler, et al.
Although regenerating complex tissues is a feature of many lower vertebrates, most mammals have traded this capacity for rapid wound healing and fibrotic scarring. In adult humans, this “regenerative window” is almost entirely closed, with the distal digit tip remaining as one of few tissues capable of complete multitissue regeneration that restores its original structure; more proximal amputations scar. Historically, research into this phenomenon has prioritized molecular signaling pathways and cellular origins. However, the role of extrinsic cues—specifically, the physical and mechanical signals from the surrounding microenvironment—has remained poorly understood in the context of whole-tissue regeneration.
Long-range chemical signalling in vivo is regulated by mechanical signals
Eva K. Pillai,
Sudipta Mukherjee,
Niklas Gampl,
Ross J. McGinn,
Katrin A. Mooslehner,
Julia M. Becker,
Alexander K. Winkel,
Amelia J. Thompson,
Kristian Franze
Nature Materials
25
687-697
(2026)
| Journal
| PDF
Biological processes are regulated by chemical and mechanical signals, yet how these signalling modalities interact remains poorly understood. Here we identify a crosstalk between tissue stiffness and long-range chemical signalling in the developing Xenopus laevis brain. Targeted knockdown of the mechanosensitive ion channel Piezo1 in retinal ganglion cells or in the brain tissue surrounding retinal ganglion cells causes pathfinding errors in vivo. In the brain parenchyma, Piezo1 downregulation decreases the expression of the diffusive long-range chemical guidance cues Semaphorin3A (Sema3A) and Slit1, which instruct turning responses in distant cells. Furthermore, Piezo1 knockdown results in tissue softening due to reduced expression of the adhesion proteins NCAM1 and N-cadherin. Targeted depletion of NCAM1 and N-cadherin similarly reduces tissue stiffness and Sema3A expression. Conversely, increasing environmental stiffness ex vivo enhances tissue-level force generation and Slit1 and Sema3A expression. Finally, in vivo stiffening of soft brain regions induces ectopic Sema3A production via a Piezo1-dependent mechanism. Overall, these findings demonstrate that tissue mechanics locally modulates the availability of diffusive, long-range chemical signals, thus influencing cell function at sites distant from the mechanical cue.
Contact
Neuronal Mechanics Division Prof. Kristian Franze Principal Investigator
Max-Planck-Zentrum für Physik und Medizin Kussmaulallee 2 91054 Erlangen, Germany
