Active and passive crowding pathways drive topological and mechanical divergence in myoblasts.

In C2C12 myoblast monolayers, active versus passive crowding yields distinct collective states with different nematic order and junctional coupling, despite strongly suppressed motion.

• Why it matters: Crowding is linked to tissue organization, but crowded organization in intrinsically anisotropic cell collectives is less understood than in polygonal epithelia.
• What they did: The study decoupled crowded-state outcome from crowding pathway by comparing active crowding from proliferation during incubation with passive crowding from high-density seeding.
• The result: The two pathways produce structurally irregular packing without epithelial-like kinetic arrest, and their mechanical coordination preserves sensitivity to topographical cues while promoting efficient, spatially organized myogenic fusion.

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