arXiv subjects

Patrick S. Noerr

Publications and source records attributed to Patrick S. Noerr.

3 recordsLinked to original sources

arXiv2026

Mitochondrial mechanics nucleates axonal jamming and swelling

Neuronal function requires precise spatial organization of mitochondria to meet localized energetic demand. However, the physical constraints governing mitochondrial transport in axons remain poorly defined. Bidirectional motor-driven trafficking inherently introduces the potential for collisions, but the implications of these interactions for transport failure and structural damage are not understood. Here, we develop an agent-based model that couples mitochondrial motility, morphology, and lifecycle dynamics to a deformable axonal boundary. We show that mitochondrial traffic jams emerge from a force balance between active propulsion and steric interactions, and that their severity is governed by organelle shape and mechanical properties. Elongated, mechanically rigid mitochondria remain aligned and are transported rapidly, whereas flexible, low-aspect-ratio mitochondria are prone to jamming and accumulation. Incorporating fission and fusion dynamics reveals that fission amplifies transport disruption by generating collision-prone populations, while fusion restores transport by producing anisotropic structures that navigate crowded environments more efficiently. Importantly, we find that sustained jamming generates mechanical stress on the axonal membrane, leading to deformation and swelling. Together, these results establish a physical framework linking mitochondrial dynamics to axonal integrity and provide testable predictions for how dysregulated fission-fusion balance can drive transport failure and structural pathology in neurons.

physics.bio-ph↗

arXiv2023

Optimal mechanical interactions direct multicellular network formation on elastic substrates

Cells self-organize into functional, ordered structures during tissue morphogenesis, a process that is evocative of colloidal self-assembly into engineered soft materials. Understanding how inter-cellular mechanical interactions may drive the formation of ordered and functional multicellular structures is important in developmental biology and tissue engineering. Here, by combining an agent-based model for contractile cells on elastic substrates with endothelial cell culture experiments, we show that substrate deformation-mediated mechanical interactions between cells can cluster and align them into branched networks. Motivated by the structure and function of vasculogenic networks, we predict how measures of network connectivity like percolation and fractal dimension, as well as local morphological features including junctions, branches, and rings depend on cell contractility and density, and on substrate elastic properties including stiffness and compressibility. We predict and confirm with experiments that cell network formation is substrate stiffness-dependent, being optimal at intermediate stiffness. Overall, we show that long-range, mechanical interactions provide an optimal and general strategy for multi-cellular self-organization, leading to more robust and efficient realization of space-spanning networks than through just local inter-cellular interactions.

cond-mat.soft↗

arXiv2022

Collective states of active particles with elastic dipolar interactions

Many types of mammalian cells exert active contractile forces and mechanically deform their elastic substrate, to accomplish biological functions such as cell migration. These substrate deformations provide a mechanism by which cells can sense other cells, leading to long range mechanical intercell interactions and possible self organization. Here, we treat cells as noisy motile particles that exert contractile dipolar stresses on elastic substrates as they move. By combining this minimal model for the motility of individual cells with a linear elastic model that accounts for substrate mediated cell cell interactions, we examine emergent collective states that result from the interplay of cell motility and long range elastic dipolar interactions. In particular, we show that particles self assemble into flexible, motile chains which can cluster to form diverse larger scale compact structures with polar order. By computing key structural and dynamical metrics, we distinguish between the collective states at weak and strong elastic interactions, as well as at low and high motility. We also show how these states are affected by confinement, an important characteristic of the complex mechanical microenvironment inhabited by cells. Our model predictions are generally applicable to active matter with dipolar interactions ranging from biological cells to synthetic colloids endowed with electric or magnetic dipole moments.

cond-mat.soft↗