Figure 5. Large cartilage nodule formation was localized at the interface of the two cells and only occurred in the absence an acellular intermediate hydrogel layer.

Newly formed cartilage nodules were visualized by immunostaining of type II collagen at day 21 in bi-layered co-culture (A) in the absence of an intermediate acellular hydrogel layer and (B) with a 250 μm acellular layer. Scale bars, 200 μm. Dotted lines in (A) indicate the localization of large cartilage nodules at the bi-layer interface, and in (B), the acellular intermediate layer.