Cartilage-characteristic matrix is produced <i>in vitro</i> in HLA-A2^- and HLA-A2⁺ chondrocyte-agarose constructs then accumulates with time in HLA-A2⁺ hu-mice.

(A, B) Type II collagen immunostaining of HLA-A2- and HLA-A2+ chondrocyte-agarose constructs after 3 weeks of in vitro culture (before implantation) and after 3 weeks of in vitro culture followed by 4 weeks of in vivo implantation (at the end of the implantation period) in HLA-A2- hu-mice. Note that cells exhibit more intense intra- and peri-cellular staining after, rather than before, implantation. (C) Western blot analysis of type II collagen synthesis before and 4 weeks after implantation. Note that type II collagen was more abundant in the cartilage disks after the implantation period, in accord with the immunohistochemical data. This abundant production also explain why bands are smeared. Scale bars are 20 μm.