Figure 4.

A subset of P58^IPK-null mice reveal a severe degenerative joint phenotype. Coronal sections, stained with toluidine blue, are depicted from the right knee joints of three of the P58^IPK-null mice aged 12–13 months (A) and 23–25 months (F,K) old with the severe phenotype. Significant bone remodeling and cartilage loss can be seen in the MTP and MFC. Magnified views of the heterotopic chondro-osseous tissue observed in the medial capsule of these sections (box) are depicted (B,G,L) showing areas of bone marrow formation (yellow arrows) along with osteophyte formation (red circles) in two of the mice. Coronal radiographs from the contra-lateral legs of each animal depicted in (A,F,K) are shown (C,H,M) highlighting the ectopic radio-dense areas in the medial collateral ligaments and the joint capsule of two of these mice [(C,M); yellow triangles]. High-resolution μCT images of the contra-lateral leg revealed changes in joint shape and osteophyte formation on the tibiae (D,I,N) and femurs (E,J,O). Scale bar = 500 μm except for (A,F,K) = 1 mm.