Figure 1.

Plasminogen deficiency imposes early degeneration and biomechanical incompetency of the axial skeleton. A, Lateral radiographs of 20-week-old control and plasminogen-deficient (PLG^−/−) mice show substantial kyphosis of the axial spine. Bars = 5 mm. B, Serial measurements of kyphotic indices indicate that following proper axial development through 5 weeks, PLG^−/− mice (triangles) show progressive degeneration compared to control mice (squares) (P=0.0003 by two-way repeated-measures analysis of variance [ANOVA]). C, Three-dimensional renderings of micro–computed tomography (micro-CT) data show evidence of rapid bone loss in the L5 vertebrae (asterisk) of PLG^−/− mice. Bars =1 mm. D, Shown are micro-CT–derived bone fraction volumes corresponding to images in C. Triangles represent PLG^−/− mice; squares represent control mice. ** = P<0.01 versus control mice, by Student’s t-test. E, Vertebral body compression ratios of T11, T12, and L1 determined from lateral radiographs demonstrate biomechanical incompetence of the anterior cortex of the vertebral bodies at age 20 weeks in PLG^−/− mice. *= P<0.05; ***= P<0.001 versus control mice, by two-way ANOVA with Bonferroni adjustment for multiple comparisons. F, Shown is premature ossification (asterisks) of the articular end plate of L5/L6 observed in PLG^−/− mice at age 10 weeks and in both control and PLG^−/− mice at age 20 weeks (Safranin O staining). Arrow indicates cartilage. Bars =100 μm. G, Shown is the percentage area of end plate ossification of L5/L6 determined by histologic examination at age 20 weeks (n = 8 wild-type mice; n = 11 PLG^−/− mice). P<0.001 versus control mice, by Student’s t-test. Bars in B, D, E, and G show the mean ±SD. Symbols in E and G represent individual mice. Color figure can be viewed in the online issue, which is available at http://onlinelibrary.wiley.com/doi/10.1002/art.38639/abstract.