1.17.12 Extracellular Matrix Definition

Extracellular Matrix Definition is a description of the network of structural molecules occupying the space surrounding cells within a tissue, secreted and assembled by the resident cells themselves, that provides a physical scaffold to which cells can attach, that determines much of the mechanical and structural character of the tissue as a whole, and that serves as the specific binding partner engaged by cell-matrix adhesion molecules such as integrins.

Conceptual Basis

A Cell-Secreted Structural Scaffold

The extracellular matrix is defined by its composition from molecules secreted by the cells residing within a given tissue, distinguishing it from a passive or externally imposed structure, and reflecting the fact that the specific composition and organization of the matrix in a given location is actively produced and maintained by the local cell population.

Occupying the Space Between Cells

The extracellular matrix occupies the physical space surrounding individual cells within a tissue, situated outside the boundary of any single cell and distinct from the intracellular components located within the cell itself, forming a continuous structural network that spans and connects the space between the cells of a tissue.

Structural Composition

Fibrous Structural Proteins

A major component of the extracellular matrix consists of fibrous structural proteins that assemble into elongated filaments or networks, contributing tensile strength and structural organization to the matrix and providing the primary scaffold to which cell-matrix adhesion molecules bind.

Ground Substance

Beyond its fibrous components, the extracellular matrix also includes a gel-like ground substance filling the space between the fibrous elements, contributing to the matrix's capacity to resist compressive forces and to regulate the movement of molecules and cells through the matrix.

Functional Roles

Providing a Physical Scaffold for Cell Attachment

The extracellular matrix provides the specific structural components recognized and bound by cell-matrix adhesion molecules such as integrins, serving as the physical scaffold to which cells anchor themselves within a tissue and thereby contributing directly to the overall structural organization of that tissue.

Determining Tissue Mechanical Properties

Because the extracellular matrix constitutes a substantial structural component of most tissues, its specific composition and organization are principal determinants of the mechanical properties of the tissue as a whole, including its stiffness, elasticity, and resistance to deformation.

Influencing Cell Behavior Through Matrix Composition

Beyond its purely structural role, the specific composition of the extracellular matrix in a given location can influence the behavior of the cells attached to it, since different matrix components engage different cell-matrix adhesion molecules and thereby trigger different downstream signaling consequences.

Relationship to Cell-Matrix Adhesion and Cancer Cell Biology

The Binding Partner of Cell-Matrix Adhesion

The extracellular matrix constitutes the specific structural counterpart engaged by cell-matrix adhesion molecules, such that the composition and organization of the matrix present in a given location directly determines the particular cell-matrix adhesive interactions that cells at that location are able to form.

Relevance to Altered Cancer Cell Adhesion and Invasion

Because the extracellular matrix provides the physical scaffold through which cells move and to which they attach, alterations in matrix composition or organization, as well as changes in how cancer cells interact with and remodel the surrounding matrix, are closely associated with the altered adhesive and invasive behaviors characteristic of cancer cell adhesion.