Gelatin zymography of MMP-2 and -9 in explant culture conditioned medium. The active form of MMP-2 was only present in explant culture on iAM (A) and dAM (B) conditioned medium, but not in the control with iAM (C) or dAM (D) alone without explants. MMP-2 activities were relatively stable throughout the culture period, but the activity was higher on dAM than on iAM. MMP-9 activities were undetectable at 4 days when the explant was cultured on both iAM (A) and dAM (B), but quickly increased in the second week. A high expression of MMP-9 was maintained in the second and third weeks on both iAM and dAM, but it decreased in the fourth week on iAM, but remained at a high level on dAM. MMP-9 activities were undetectable in the control without explants (C, D).