Long-term functions in 3T3-J2-coated microtissues. 3T3-J2 fibroblasts were coated onto the surface of the polymerized collagen-based PHH microtissues (“coated microtissue”) and cultured for ∼6 weeks. (a) Albumin production, (b) urea production, and the activities of different CYP450 isoenzymes, (c) CYP3A4 activity, (d) CYP2A6, (e) CYP2C9, and (f) CYP1A2 in coated microtissues over time.