grundsubstans

Grundsubstans, or ground substance, is the non-cellular component of the extracellular matrix in connective tissue. It forms a hydrated, gel-like medium that fills the spaces between cells and fibers and supports other matrix components.

Composition and structure include glycosaminoglycans (GAGs) such as hyaluronic acid, chondroitin sulfate and dermatan sulfate; proteoglycans; and adhesive glycoproteins like laminin and fibronectin. The GAGs are highly negatively charged, which attracts water and creates a hydrated matrix that resists compression and enables diffusion of nutrients, waste, and signaling molecules.

Functions of grundsubstans include providing resilience and lubrication for tissues, facilitating the diffusion of nutrients and metabolites between blood vessels and cells, and serving as a reservoir for growth factors and cytokines. It also influences cell behavior, migration, and tissue repair by presenting biochemical cues to resident cells.

Variation exists across tissues. In loose connective tissue the ground substance is relatively abundant and permissive to diffusion, while in cartilage it is dense and highly hydrated with a strong proteoglycan content, contributing to cartilage’s load-bearing properties. In bone, the ground substance is mineralized as part of the larger extracellular matrix.

Cells such as fibroblasts, chondroblasts, and other resident cells synthesize grundsubstans components, and remodeling is mediated by enzymes like matrix metalloproteinases. Changes in its composition or hydration affect tissue mechanics and diffusion properties, and alterations are linked to aging and various diseases.