Staining of the extracellular matrix
The material that lies between the cells – called the extracellular matrix – becomes also stained by the usual histological stains.
The chemical composition of the extracellular matrix varies in the different tissues and regions of the body. If the matrix is composed mainly of proteins, it will probably be stained with eosin. This was already shown on page 1-24, where collagen fibers were stained with eosin.
The image on this page is of a hyaline cartilage.
Its extracellular matrix occupies the space between the cartilage cells, also called chondrocytes or between groups of chondrocytes.
Observe that instead of being acidophilic (pink, stained by eosin) as in the case of a collagen-rich matrix, the cartilage matrix is stained blue-purple by hematoxylin and is, therefore, basophilic.
This happens because the matrix of this type of cartilage contains many molecules with acidic groups (mainly sulfates). These groups have an affinity for hematoxylin.
After moving the mouse or clicking over the image the nuclei of the chondrocytes are seen in dark blue and the extracellular matrix in turquoise blue.
The cartilage is surrounded (at the its left and right edges) by a layer of connective tissue formed by cells and an extracellular matrix that has cells and much collagen. Collagen stains red or pink by eosin and is acidophilic. The connective tissue will be seen in pink after moving the mouse.
Hyaline cartilage. Staining: hematoxylin and eosin. Small magnification.
