Cell bricks guided persistent ectopic chondrogenesis of bone marrow-derived mesenchymal stem cells and prevented ossification. Examining osteogenesis of grafts in vivo at 4 weeks (I-A to I-L) and 12 weeks (II-A to II-L). The B-CB-P group did not present ossification of BMSCs through 12 weeks (I-A to D; II-A to D), as confirmed by Von-Kossa, Masson’s trichrome, COL-I and COL-X immunostaining, which is similar to the chondrocyte implantation group (II-I to L). In contrast, BMSCs in the B-C-P group presented slower calcification than the B-P group (I-E to H, I-I to L), whereas final ossification occurred through 12 weeks (II-E to H); bar = 50 μm, magnification × 200 (I-A to L, II-A to L). B-C-P, BMSCs–chondrocytes–PRP; B-CB-P, BMSCs–cell bricks–PRP; B-P, BMSCs–PRP; BMSC, bone marrow-derived mesenchymal stem cell; COL, collagen; PRP, platelet-rich plasma.