Frog skin epithelium interactions with a bovine purified type I collagen gel in culture.

Isolated epithelium of the ventral frog skin was superimposed to purified type I collagen gels and then cultured. The epithelial anchoring process was dependent on the collagenase type used for epithelial isolation. With type I collagenase, lamina densa remained attached to the basal epithelial pole and epithelial anchorage to the gel was effective. But this anchorage could only take place if gels were precoated with culture media supplemented with fetal calf serum. In these fibrillar gels, 2 types of collagen striated fibers assemblies occurred. In the upper zone, striated fibers assembly was cell-dependent. The basal pole of Malpighian cells generated numerous filopodia inserted into the gel. These filopodia polarized the collagenous assembly around and along them. In the inner zone, aggregates with cholesteric texture were assembled without superimposed epithelium. Their shape and width seemed to be related to the acidosoluble collagen concentration.