Interaction between collagen type I and type III in conditioning bundles organization.

Type I and type III collagen extracted from skin was purified by differential salt precipitation and chromatography. By heating to 37 degrees, type I formed after a lag phase a floppy and opalescent gel of high optical density and type III formed more rapidly a translucent and rigid gel of low optical density. Addition of type III to type I resulted in formation of gels of reduced optical density and lag phase related to the proportion of type III added. Phase contrast and scanning electronmicroscopy demonstrated the formation of thick bundles of type I, thin fibers of type III and bundles of intermediate size related to the proportion of type III. The relationship between collagen type and bundle architecture might prove most significant in conditioning the mechanical properties of the connective tissues in normal and pathological conditions.