In situ detection of gelatinolytic activity in developing craniofacial tissues

Frozen tissue sections of developing and adult rat heads were incubated on a film coated with a gelatin-containing colloidal silver emulsion in order to detect gelatinolytic activity present in the different tissues. The method, termed film in situ zymography, is based on the ability of the thiol group of the propeptide released from the degraded gelatin to induce a structural change in the colloidal silver and thereby a visible change in color. The frozen tissue sections mounted on the coated film were incubated at 37 degrees C overnight. Gelatinolytic activity was detected as a color change from yellow to red. The activity of gelatinase was completely blocked by phenanthroline, which inhibits matrix metalloproteinases. Gelatinolytic activity was widely present in the oral epithelium, tooth buds, tongue, Meckel's cartilage, salivary glands, and other tissues. The intensity of the gelatinolytic activity varied among the different tissue types. The present study demonstrated gelatinolytic activity in both developing and adult craniofacial tissues. These results suggest that gelatinolytic activity plays an important role in normal turn-over in several tissues. Whereas some of the activity also in the developing rats may be related to this turn-over process, some of it is probably directly associated with developmental changes.