Research ArticleOsteoarthritis

Topographic modeling of early human osteoarthritis in sheep

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Science Translational Medicine  04 Sep 2019:
Vol. 11, Issue 508, eaax6775
DOI: 10.1126/scitranslmed.aax6775
  • Fig. 1 Ovine OA changes.

    (A) Schematic of surgical approach. OA was induced by removing the anterior third of the medial meniscus (pMMx). (B) Representative x-ray images (arrowhead, osteophytes; arrows, suspected joint space narrowing) and (C) box plot of the KL scores (dots, individual data points; +, mean values; whiskers, minimum and maximum values of the datasets; upper and lower borders of the boxes, the 75th and 25th percentiles) of the ovine knees. Coverage of OA lesions (D) in the total area of the ROIs and (E to I) within the individual subregions. (J) Area of osteophytes and (K) schematic maps of their localization in the medial tibial plateau (larger images; insets show the entire tibial plateau). (L) Representative 2D micro-CT images showing osteophyte development (arrowheads) and the original margin of the tibial plateau (dashed lines). A schematic diagram of the subregions evaluated in the medial tibial plateau is shown in fig. S1. a, anterior; d, distal; l, lateral; m, medial; p, posterior; pr, proximal. n = 7 to 8 per group. *P < 0.05, **P < 0.01, normal versus pMMx with paired t test or Wilcoxon test.

  • Fig. 2 OA changes of the ovine articular cartilage.

    (A, B, and E) Six weeks and (C, D, and F) 6 months after pMMx. Box plots of histological scoring of (A and C) surface structure and (B and D) chondrocyte density according to subregion. Higher scores indicate more deviation from normal; the color code is identical for all box plots. (E and F) Representative safranin O–stained histological sections and polarized light microscopy images of Masson-Goldner trichrome–stained histological sections (in insets; all panels with identical magnification) from the subregions of normal and pMMx samples, showing the severity of OA (E) 6 weeks and (F) 6 months after pMMx. Dashed lines indicate the alignment of the images according to the cement line. (G to K) Total OARSI histopathological scores (44) determined in the individual subregions, where higher values indicate more severe OA. n = 8 per group. *P < 0.05, **P < 0.01, normal versus pMMx with Wilcoxon test.

  • Fig. 3 Ovine normal and OA osteochondral correlations.

    (A) Schematic representation of differences in subchondral bone plate thickness expressed as the percentage of change in pMMx compared to normal. Scatter plot and linear regression showing the correlation between cartilage thickness and subchondral bone plate thickness in the normal and pMMx samples. (B) Six weeks and (C) 6 months after OA induction. Correlation coefficients of the individual regions are shown in table S1. a, anterior; d, distal; l, lateral; m, medial; p, posterior; pr, proximal. n = 18 to 48 locations per group. *P < 0.05, **P < 0.01, normal versus pMMx with paired t test or Wilcoxon test.

  • Fig. 4 OA structural changes in the ovine subchondral bone.

    Regional analysis of the (A and D) bone surface density (BS/TV) and (B and E) total porosity of the subchondral bone plate (A and B) 6 weeks and (D and E) 6 months after pMMx. (C) 3D reconstructed micro-CT models of the subchondral bone plate porosity showing the spatial distribution of open and closed pores in the anterior central region, with lower magnification view in insets. Progressive trabecular degradation in the subarticular spongiosa (F to M) 6 weeks and (N to U) 6 months after pMMx. (F and N) Representative Masson-Goldner trichrome–stained histological sections, 3D reconstructed micro-CT models, color-coded 2D micro-CT images, and 3D models of trabecular separation of the subarticular spongiosa of the intermediate peripheral region of normal and pMMx (F) 6 weeks and (N) 6 months after surgery. Regional analysis of (G and O) BS/TV, (H and P) bone volume fraction (BV/TV), (I and Q) bone mineral density (BMD), (J and R) trabecular number (Tb.N), (K and S) connectivity density (Conn.Dn), (L and T) trabecular separation (Tb.Sp), and (M and U) trabecular thickness (Tb.Th). Ant, anterior region; Interm, intermediate region; Post, posterior region; centr, central; periph, peripheral. n = 7 to 8 per group. *P < 0.05, **P < 0.01, normal versus pMMx with paired t test or Wilcoxon test.

  • Fig. 5 PCA of ovine OA.

    (A and C) Articular cartilage and (B and D) subchondral bone, (A and B) 6 weeks and (C and D) 6 months postoperatively. All determined cartilage and bone parameters were used as input data to visualize the separation of the samples into groups based on the individual subregions. Data points represent individual normal and pMMx samples. Information content (% of variance) of the axes for principal components 1 (PC1) and 2 (PC2) are shown above the graphs.

  • Fig. 6 Evaluation of human OA.

    (A) Representative x-rays (arrowheads, osteophytes; arrows, joint space narrowing) and box plot of KL scores of human knees. (B) Schematic topographical comparison of ovine subregions (6 weeks, 6 months) and human early and late OA. (C) Localization and area of osteophytes in late human OA (large image, medial tibial plateau; inset, entire tibial plateau). (D) Representative India ink–stained macroscopic images and 3D reconstructed micro-CT models of a normal and late OA tibial plateau: regional analysis of coverage by OA. (E) Structure, (F) chondrocytes, (G) matrix staining subscores, and (H) total Mankin (51) and (I) OARSI scores (52) of human late OA. (J) Schematic map of mean human cartilage thickness. (K) Structural overview and color-coded 2D and 3D micro-CT models of osteochondral thickness of representative human normal and OA samples. (L) Schematic map of mean human subchondral bone plate thickness. (M) Scatter plot and linear regression showing the correlation between cartilage thickness and subchondral bone plate thickness (normal, OA samples). (N) Schematic map of percentage of change of cartilage and subchondral bone plate thicknesses in late OA compared to normal. Ant, anterior; Interm, intermediate; Post, posterior; centr, central; periph, peripheral; a, anterior; l, lateral; m, medial; p, posterior. n = 4 to 13 per group. *P < 0.05, **P < 0.01 with unpaired t test or Mann-Whitney test.

  • Fig. 7 Evaluation of human OA in the subarticular spongiosa.

    Regional analysis of (A) BS/TV, (B) Conn.Dn, (C) Tb.Th, (D) fractal dimension (FD), (E) BV/TV, (F) Tb.N, and (G) Tb.Sp. n = 5 to 8 per group. (H) Representative 3D reconstructed models, color-coded 2D micro-CT images, and 3D models of trabecular separation (intermediate central region, human normal and late OA knees). (I) Representative Masson-Goldner trichrome–stained histological sections and 3D reconstructed micro-CT models (anterior and posterior subregions) in normal sheep knees. Evaluation of the similarity of the anterior and posterior subregions in all normal ovine samples (n = 16) by (J) PCA and (K) plotting the distribution of nonsignificant (n = 17) and significantly different (P < 0.05; n = 5) parameters within all of the evaluated micro-CT parameters (n = 22). (L) PCA and (M) cluster analysis of human normal and late OA subarticular spongiosa (considering all determined micro-CT parameters, all subregions). (N) PCA and (O) cluster analysis with heat-map comparison of human normal and late OA articular cartilage based on Mankin and OARSI scores. Ant, anterior; Interm, intermediate; Post, posterior; centr, central; periph, peripheral. *P < 0.05, **P < 0.01 with unpaired t test or Mann-Whitney test.

Supplementary Materials

  • stm.sciencemag.org/cgi/content/full/11/508/eaax6775/DC1

    Fig. S1. Subregions evaluated in the ovine medial tibial plateau.

    Fig. S2. Correlation between the location of osteophytes and OA lesions in sheep.

    Fig. S3. Histopathological scores of the ovine articular cartilage.

    Fig. S4. OA patterns of ovine articular cartilage and subchondral bone plate thickness.

    Fig. S5. Topographical patterns of the OA changes of the ovine subchondral bone plate.

    Fig. S6. Topographical patterns of the OA changes of the ovine subarticular spongiosa.

    Fig. S7. Cluster analysis of the ovine articular cartilage and the subchondral bone parameters at 6 weeks after pMMx.

    Fig. S8. Cluster analysis of the ovine articular cartilage and the subchondral bone parameters at 6 months after pMMx.

    Fig. S9. Minimally required ovine subchondral bone parameters to clearly separate normal from pMMx with multivariate analysis at 6 months.

    Fig. S10. Human early OA meniscus and cartilage scores.

    Fig. S11. Additional structural parameters of subarticular spongiosa in human late OA.

    Fig. S12. Proposed schematic of the initiation and spatiotemporal progression of OA by a defined meniscal tissue loss.

    Table S1. Pearson correlation analysis between the subchondral bone plate thickness and the articular cartilage thickness within the three main regions.

    Data file S1. Raw data of the figures.

  • The PDF file includes:

    • Fig. S1. Subregions evaluated in the ovine medial tibial plateau.
    • Fig. S2. Correlation between the location of osteophytes and OA lesions in sheep.
    • Fig. S3. Histopathological scores of the ovine articular cartilage.
    • Fig. S4. OA patterns of ovine articular cartilage and subchondral bone plate thickness.
    • Fig. S5. Topographical patterns of the OA changes of the ovine subchondral bone plate.
    • Fig. S6. Topographical patterns of the OA changes of the ovine subarticular spongiosa.
    • Fig. S7. Cluster analysis of the ovine articular cartilage and the subchondral bone parameters at 6 weeks after pMMx.
    • Fig. S8. Cluster analysis of the ovine articular cartilage and the subchondral bone parameters at 6 months after pMMx.
    • Fig. S9. Minimally required ovine subchondral bone parameters to clearly separate normal from pMMx with multivariate analysis at 6 months.
    • Fig. S10. Human early OA meniscus and cartilage scores.
    • Fig. S11. Additional structural parameters of subarticular spongiosa in human late OA.
    • Fig. S12. Proposed schematic of the initiation and spatiotemporal progression of OA by a defined meniscal tissue loss.
    • Table S1. Pearson correlation analysis between the subchondral bone plate thickness and the articular cartilage thickness within the three main regions.
    • Legend for data file S1

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    Other Supplementary Material for this manuscript includes the following:

    • Data file S1 (Microsoft Excel format). Raw data of the figures.

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