3D Culture Reverses Limbal Niche Cell Replicative Aging via FOSL1 Upregulation

Limbal niche cells (LNCs) serve as essential regulators of limbal microenvironmental homeostasis and corneal epithelial wound repair, representing a promising therapeutic resource for limbal stem cell deficiency (LSCD). However, their clinical application is constrained by replicative aging during in vitro expansion. In this study, we investigated whether a three-dimensional (3D) Matrigel-based culture system could modulate replicative aging in LNCs. Compared with conventional two-dimensional (2D) culture, 3D-cultured LNCs restored stemness marker expression and enhanced proliferative capacity. Concurrently, these cells displayed reduced senescence-associated β-galactosidase (SA-β-gal) activity and decreased expression of senescence-associated proteins, including p16, p21, p53, and γ-H2AX. Single-cell RNA sequencing (scRNA-seq) analysis revealed prominent upregulation of FOS-like antigen 1 (FOSL1). FOSL1 is a component of the AP-1 transcription factor family and participates in cell proliferation and stress adaptation. Functional assays using an in vitro replicative aging model showed that FOSL1 knockdown in early-passage (P4) LNCs accelerated senescence, whereas FOSL1 overexpression in late-passage (P11) LNCs attenuated senescence. Mechanistically, FOSL1 knockdown induced mitochondrial dysfunction characterized by elevated levels of mitochondrial superoxide and cellular reactive oxygen species (ROS), as well as a decrease in mitochondrial membrane potential, while FOSL1 overexpression preserved mitochondrial integrity and function. Collectively, our findings demonstrate that 3D culture reverses LNC replicative aging through FOSL1-mediated enhancement of mitochondrial function, providing a microenvironment-based strategy to counteract replicative aging in adult stem cells for corneal regenerative therapy.