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Medicine and Health Sciences


Context: This research may provide insight into human articular cartilage development, repair mechanisms, and diseases such as arthritis. Objective: The purpose of this study is to compare the proximal femur articular cartilage from hypothyroid-induced juvenile miniature swine to control animals. Design: This study is a randomized control trial (RCT). Setting: All procedures and housing were IUCUC approved; n=4. Methods: Two juvenile male, 11-week-old miniature swine were administered 6-Propyl-2-thiouracil (PTU) via drinking water to induce hypothyroidism; two control animals were identical in age and sex. The articular cartilage from proximal femurs harvested from 25-week-old animals were analyzed with histology, immunohistochemistry (IHC), and histomorphometry. Histology analyzed tissue morphology and proteoglycan content, IHC assessed types II and X collagen, and histomorphometry measured articular cartilage tissue height and cell density. Nested mixed effects ANOVA with α = 0.05 examined histomorphometry data. Results: Hypothyroid articular cartilage displays increased proteoglycan and decreased type II collagen staining patterns and intensities, compared to controls. Type X collagen is absent in hypothyroid and control articular cartilage, but it is present in control growth plate cartilage. Mean tissue height is increased (2337.0 ± 132.8 μm vs 1076.1 ± 132.7 μm, p = 0.021) and mean cell density is decreased (27.6 ± 1.0 cells/cm2 vs 31.0 ± 1.0 cells/cm2, p = 0.016) in hypothyroid articular cartilage, compared to controls. Conclusions: Hypothyroidism in juvenile miniature swine yielded histomorphometric changes in articular cartilage mean tissue height and mean cell density, and different proteoglycan and type II collagen staining, compared to controls. These data suggest delayed progression of articular cartilage development in hypothyroid animals and support the theory that thyroid hormones are fundamental to articular cartilage growth and development.


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