Dimensionality and confinement reshape competition in cellular renewing active matter

Abstract Cellular renewing active matter—assemblies of proliferating and apoptotic cells—underlies tissue homeostasis, morphogenesis, and clonal competition. Previous work in one-dimensional periodic systems identified a fitness advantage associated with rapid dead-cell clearance, an ‘opportunistic’ competition mechanism. Extending this framework, we study two-dimensional cellular aggregates and show that dimensionality modifies the interplay between competition mechanisms for clones with different clearance rates: in 2D, opportunistic and homeostatic-pressure-based competition jointly shape clonal selection, to varying degrees. We then introduce an explicit circular confinement to probe how physical boundaries modulate this interplay. While opportunistic competition persists, distinct time-dependent behaviors emerge through weakened homeostatic-pressure-based competition near boundaries. Structural analysis reveals that confinement promotes tangential alignment and spatially heterogeneous homeostatic pressure, thereby reshaping competitive outcomes at tissue edges. Partial information decomposition allows us to attribute these differing outcomes to temporally and spatially varying relative contributions of the two mechanisms. Our study connects newly discovered competition mechanisms with more realistic biological contexts, highlighting how dimensionality and spatial constraints influence tissue structures and modulate competition in heterogeneous cell populations across time and space, with implications for tumor growth dynamics and tissue development.