haptotaxis

Haptotaxis is the directed migration of cells in response to a gradient of substrate-bound cues, such as extracellular matrix proteins or immobilized signaling ligands. Unlike chemotaxis, which relies on soluble chemical gradients, haptotaxis arises from spatial variation in the density or availability of adhesive ligands on a surface or within the extracellular matrix.

Mechanistically, haptotaxis is mediated by cell-surface receptors such as integrins that bind ECM ligands, triggering signaling that polarizes the cell and organizes focal adhesions and actin cytoskeleton. As cells sense higher ligand density, they form more stable adhesions, extend protrusions toward that side, and generate traction forces that bias movement along the gradient. The response depends on gradient steepness, ligand type, and the overall adhesive level.

Haptotaxis plays roles in development, wound healing, and cancer. Fibroblasts and epithelial cells can migrate along gradients of fibronectin, collagen, or laminin. During development, migrating cells may follow ECM-bound cues. In wound healing, locally remodeled ECM creates adhesive tracks that guide cell repopulation. In cancer, tumor cells can exploit haptotaxis to migrate along ECM tracks created by matrix remodeling and proteolysis, contributing to invasion.

Experimental studies of haptotaxis often use substrates with immobilized ligands arranged in controlled gradients to distinguish adhesive-guided migration from chemotaxis. These models inform biomaterial design for tissue engineering and help interpret cell migration in complex tissues where both soluble signals and ECM-bound cues are present.