Quantitative imaging of corneal endothelial development reveals dynamic but resilient monolayer.

The formation of functional corneal endothelial cells during development requires tight coordination between tissue-scale growth and cell-scale organization, yet how these processes are integrated in three dimensions remains poorly understood. Here, we combine high-resolution confocal imaging with quantitative analysis to reconstruct the morphogenesis of the chick corneal endothelium across embryonic development. Using a pipeline integrating 3D nuclear segmentation, Voronoi-based topological mapping, and spatial statistics, we link macroscopic globe expansion to single-cell geometry and lattice organization. We identify a multiphasic relationship between tissue growth and cell density, driven by temporal decoupling of organ expansion and proliferation. During early development, rapid globe expansion induces cellular stretching and spatial heterogeneity, followed by a phase of density accumulation and geometric refinement. Despite these dynamic conditions, the endothelial sheet maintains a robust monolayer architecture with minimal z-axis stratification. Quantitative topological analysis reveals that hexagonal packing is preserved from early stages and progressively refined through reduction of area variability and spatial clustering. Nearest-neighbor and Clark-Evans analyses demonstrate a transition from localized clustering to a more uniform spatial distribution, consistent with increasing packing regularity. Transient out-of-plane deviations coincide with key mechanical transitions, suggesting a role for 3D remodeling in accommodating mechanical stress. Concomitantly, junctional and cytoskeletal organization undergo progressive maturation. N-cadherin is established early at cell-cell interfaces, while Zonula Occludens-1 (ZO-1) transitions from diffuse localization to apically enriched tight junctions aligned with cortical actin. In parallel, microtubule organization becomes increasingly polarized to the apical domain, coinciding with the emergence of primary cilia. Together, these changes reflect coordinated establishment of epithelial polarity, barrier function, and mechanical stability. Overall, our study provides a multiscale, imaging-driven framework for understanding how epithelial tissues achieve and maintain geometric order under mechanical strain, establishing the corneal endothelium as an exemplar for linking developmental mechanics, 3D architecture, and epithelial topology.