Abstract
Purpose: :
During corneal wound healing, corneal fibroblasts migrate from the surrounding stroma into a provisional extracellular matrix (ECM). The purpose of this study was to investigate how ECM composition influences the pattern and amount of cell migration using a novel 3D culture model.
Methods: :
Sandwiched, compacted collagen matrices containing corneal fibroblasts were embedded inside cell-free collagen or fibrin matrices (2 mg/ml). These nested constructs were cultured for 1-4 days in serum-free media containing 50 ng/ml PDGF. Time-lapse DIC microscopy was used to record dynamic cell behavior and ECM deformation. Cell counts and cell-matrix interactions were assessed using a combination of fluorescent and reflected light confocal imaging.
Results: :
Cell migration was differentially regulated by different matrix types. Fibroblasts migrating into collagen matrices moved individually, whereas cells migrating into fibrin matrices formed an interconnected network. The number of cells and speed of migration were significantly reduced in fibrin. Confocal reflection and DIC imaging showed that cell-induced matrix remodeling was also more pronounced in collagen than in fibrin. Addition of Fibronectin and Factor XIII to fibrin matrices significantly increased the number of cells that migrated into the outer matrices; however, cells still migrated collectively. In studies using isolated corneal fibroblasts, cells on collagen spread quickly by protruding a network of thin extensions that resulted in a dendritic morphology; whereas cells on fibrin spread more slowly via lamellar extensions that resulted in a more flattened morphology. Spreading was accelerated when fibronectin and factor XIII were added to fibrin matrices, but final morphology was not changed.
Conclusions: :
This nested matrix model provides unique insights into how migrating cells perceive and respond to their 3D physical environment. The data demonstrate significant differences in the mechanism of corneal fibroblast migration in collagen and fibrin. Interestingly, the collective cell migration observed in fibrin matrices is also observed during healing of full thickness corneal wounds in vivo.
Keywords: cornea: stroma and keratocytes • extracellular matrix • cell adhesions/cell junctions