A Candidate ALS-Associated Astrocytic Morphogeometric Microdomain:From a Continuous Vimentin-Positive Morphology Axis to Local Multicellular Spatial Organization

Abstract

Amyotrophic lateral sclerosis (ALS) is accompanied by astrocytic reactivity, altered glial signaling and changes in astrocyte morphology, but it remains unclear whether disease-associated morphology is organized only at the level of individual cells or can form reproducible local multicellular spatial structures. Here we re-analyzed publicly deposited human patient-derived astrocyte microscopy from the MYC-driven gliosis study of Fioretti et al. and integrated the morphology findings with two independent human spinal-cord single-nucleus RNA-sequencing cohorts. Using DAPI-nucleus-anchored watershed partitioning, we obtained 465 Vimentin-positive cell territories (410 ALS-associated and 55 control-associated) from the available representative fields. We defined a locked multidimensional morphology score combining compactness, solidity, extent, nucleus fraction, eccentricity, aspect ratio, nuclear offset, radial heterogeneity and normalized Vimentin skeleton complexity. ALS fields showed a distribution-wide shift toward the compact morphology axis rather than a discrete unsupervised cell class. We then asked whether high-score cells formed tissue-like local domains. In the strongest sporadic ALS field, 19 of 27 high-score cells formed one k-nearest-neighbour-connected core. The core displayed strong core-to-boundary contrast (median score 2.657 versus 0.949; permutation p=0.0002), greater within-core multivariate morphological coherence than random equal-sized cell sets (distance ratio 0.635; p=0.0002), and radial relaxation of the morphology score with distance from the core (rho=-0.289; p=0.0090). Model comparison favored a boundary-plus-gradient hybrid over a smooth radial model in this field. Smaller C9orf72-associated domains reproduced internal coherence and core elevation but not the complete large-domain radial pattern. We therefore identify a candidate ALS-associated astrocytic morphogeometric microdomain: a localized multicellular morphology structure defined by internal geometric coherence and a measurable core-boundary transition, with radial relaxation in the strongest field. This is not evidence for a new astrocyte cell type or a newly established histological tissue. Independent donor-level imaging is required for confirmation.