Keratinocyte differentiation and proliferation are regulated by adhesion to the three-dimensional meshwork structure of type IV collagen.

We examined the behavior of human foreskin keratinocytes (HFKs) on reconstituted type IV collagen gel. HFKs survived for several days and the upper layer cells expressed a differentiation marker, involucrin. Apoptosis was induced after involucrin expression while cell proliferation was suppressed. On molecular type IV collagen, integrins shifted from alpha 2 beta 1 to alpha 3 beta 1 during HFK culture. On type IV collagen gel, HFKs initially expressed integrin alpha 2 beta 1, and later expressed integrin alpha 3 beta 1 in the presence of alpha 2 beta 1 did not disappear. Using synthetic peptides, we examined integrin alpha2-mediated adhesion to type IV collagen gel. Addition of synthetic peptide dose-dependently inhibited cell adhesion both on type IV collagen gel and on molecular type IV collagen. On type IV collagen gel, weaker phosphorylation of focal adhesion kinase, paxillin, and Akt was observed compared with the molecular forms. Based on these observations, we think type IV collagen gel is a novel culture substrate that mimics the physiological environment for HFKs.