Biology subjects

Madl, C. M.

Publications and source records attributed to Madl, C. M..

3 recordsLinked to original sources

bioRxiv2026

Directing Cell Fate via Spatiotemporally Patterned Viscoelasticity Driven by Dynamic Crosslink Exchange

The spatially and temporally varied mechanical and biochemical properties of the extracellular matrix (ECM) are critical regulators of cell function. Despite the emerging importance of ECM viscoelasticity in dictating cell fate, suitable biomaterials systems enabling spatiotemporal control over matrix viscoelasticity to direct cell function in physiologically relevant 3D contexts are lacking. A dynamic covalent hydrogel platform was developed that enables user-defined, in situ modulation of stress relaxation kinetics decoupled from bulk network stiffness via self-contained, radical-free photochemistries. By introducing photocaged alkoxyamines into initially rapidly relaxing hydrazone-based networks, the viscoelasticity of the networks can be tuned on demand by converting the hydrazone crosslinks to more stable oxime crosslinks following light exposure. This hydrazone-to-oxime bond exchange drives a dramatic shift in stress relaxation half time from approximately ~10^2 s to ~10^4 s within a single, continuous matrix, without altering stiffness or introducing cytotoxicity. This platform enabled real-time control over cellular adaptations to spatiotemporally patterned viscoelastic mechanical cues, directing fibroblast morphological transitions in 2D, human neural progenitor cell stemness maintenance in 3D, and neurite outgrowth from encapsulated motor neuron spheroids. This phototunable hydrogel system represents a robust platform for selectively patterning viscoelastic cues to direct mechanosensitive cell fate transitions.

bioengineering↗

bioRxiv2026

Tissue-like Viscoelasticity Drives Muscle Stem Cell Expansion Through Mechanical Memory Formation

Mechanical cues are potent regulators of stem cell fate, with even transient exposure to substrates with varied elastic stiffness driving persistent changes in cell fate. Such elastic mechanical memory contributes to the loss of regenerative potential in skeletal muscle stem cells (MuSCs) when cultured on rigid substrates, hampering the translation of myogenic cell replacement therapies. Beyond elastic mechanical properties, cells also respond to time-dependent, viscoelastic mechanical properties, such as stress relaxation. However, whether tissue-like viscoelasticity can impart a mechanical memory that directs stem cell fate remains an open question. Accordingly, dual-network hydrogel biomaterials with decoupled control of stiffness, stress relaxation, and adhesive ligand presentation were engineered to recapitulate the viscoelastic mechanical properties of native muscle. Muscle-like viscoelastic substrates promote in vitro MuSC activation and accelerate stem cell expansion, matching in vivo activation timescales. Mechanistically, physiological viscoelasticity promotes focal adhesion stabilization and enhances Rac-Akt signaling, establishing a viscoelastic mechanical memory that supports progenitor expansion and persistent maintenance of a stem-like phenotype. These findings identify matrix viscoelasticity as a potent and persistent regulator of MuSC fate and provide a framework for engineering biomaterials that preserve MuSC stemness and expansion ex vivo.

bioengineering↗

bioRxiv2022

Machine learning-based classification of binary dynamic fluorescence signals reveals muscle stem cell fate transitions in response to pro-regenerative niche factors

The proper regulation of muscle stem cell (MuSC) fate by cues from the niche is essential for regeneration of skeletal muscle. How pro-regenerative niche factors control the dynamics of MuSC fate decisions remains unknown due to limitations of population-level endpoint assays. To address this knowledge gap, we developed a novel binary dynamic fluorescence time lapse imaging analysis (BDFA) approach that leverages machine learning classification strategies to track single cell fate decisions with high temporal resolution. Using two fluorescent reporters that read out maintenance of stemness and myogenic commitment, we constructed detailed lineage trees for individual MuSCs and their progeny, classifying each division event as symmetric self-renewing, asymmetric, or symmetric committed. Our analysis reveals that treatment with the lipid metabolite, prostaglandin E2 (PGE2), accelerates the rate of MuSC proliferation over time, while biasing division events toward symmetric self-renewal. In contrast, the IL6 family member, Oncostatin M (OSM) decreases the proliferation rate after the first generation, while blocking myogenic commitment. These insights into the dynamics of MuSC regulation by niche cues were uniquely enabled by our BDFA approach. We anticipate that similar binary live cell readouts derived from BDFA will markedly expand our understanding of how niche factors control tissue regeneration in real time.

cell biology↗