Abstract
Purpose:
Previously we reported that extracellular matrix (ECM) composition modulates the mechanism of corneal fibroblast spreading and migration in 3D culture. Specifically, cells migrating into collagen matrices develop dendritic processes and move independently, whereas cells migrating into fibrin matrices develop stress fibers, move more slowly and form an interconnected meshwork. We and other labs have also shown that stimulating cell contractility can induce clustering of cells on top of collagen matrices. In this study, we investigate the role of cell contractility in mediating collective spreading and migration of cells interacting with fibrin matrices.
Methods:
To analyze 3-D cell migration, compacted cell-populated collagen matrices were embedded inside cell-free collagen or fibrin matrices. These nested constructs were then cultured for 4 days in DMEM media containing 50 ng/ml PDGF, with or without the Rho kinase inhibitor Y-27632 or the myosin II inhibitor blebbistatin. To analyze spreading of cells in 2-D, fibroblasts were plated on top of collagen and fibrin matrices. Time-lapse DIC and phase contrast microscopy was used to record the dynamic pattern of cell migration into the outer matrix. 3-D confocal imaging was used to assess cell connectivity, cytoskeletal organization and cell-induced matrix remodeling.
Results:
Experiments in nested fibrin matrices demonstrated that both Y-27632 and blebbistatin blocked the formation of stress fibers and reduced the rate of 3-D cell migration. However, the pattern of cell migration did not change - cells were interconnected and migrated collectively in fibrin but moved independently in collagen. Y-27632 and blebbistatin also blocked stress fiber formation and matrix reorganization in 2-D culture. However, cells still showed similar differences in cell connectivity - cells remained separated on collagen but coalesced into clusters on fibrin.
Conclusions:
Overall, the data suggest that fibrin-induced corneal fibroblast clustering and collective cell migration is not dependent upon increased cell contractility. We hypothesize that these changes may instead be regulated by differences in cell adhesion, integrin expression and/or protease activity. Collective fibroblast migration patterns have also been observed during in vivo corneal wound healing.
Keywords: 484 cornea: stroma and keratocytes •
519 extracellular matrix •
765 wound healing