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Fig. 5 | Stem Cell Research & Therapy

Fig. 5

From: Human pluripotent stem cell-derived cartilaginous organoids promote scaffold-free healing of critical size long bone defects

Fig. 5

IL-1β priming allows successful fracture repair. Upon IL-1β treatment, a trend towards a decrease in chondromodulin was detected, while IL-1β upregulated VEGF and MMP13 (A). Safranin-O staining prior to implantation further revealed the increase in chondrocyte lacunae size, suggesting progressive maturation towards chondrocyte hypertrophy (B). Following orthotopic implantation, the cartilaginous organoids underwent progressive mineralization with bone bridging being detected in the µCT images after 4 weeks (C). µCT quantification revealed a significant increase (p = 0.0095) in the volume of mineralized tissue in the defect area between BBT3 and BBT3 + IL-1β conditions after 8 weeks (D). Histological analysis using safranin-O further revealed accelerated bone formation with cartilage resorption being detected at week 4 (E). While bone union was detected after 8 weeks, some cartilaginous remnants could be detected, which indicates progressive cartilage resorption. Immunostaining of human collagen type I further revealed that the newly formed bone was host derived, while some hypertrophic chondrocytes expressed low levels of collagen type I (F). Mathematical modelling was used to confirm the cumulative effects of BMP, Wnt, TH and IL-1β in chondrocyte hypertrophy. An increase in hypertrophy chance, along with a decrease in variability, was detected following in vitro stimulation with aforementioned factors. DC: β-catenin Destruction Complex  (G). The presented data have been collected from experiments (n = 6) using CY2 cell line. Statistical significance is represented as follow: *p < 0.05; **p < 0.01; ***p < 0.001, and ****p < 0.0001. The following abbreviations have been used to highlight the tissue composition in the sections: B: bone, C: cartilage, M: bone marrow, T: cartilage-bone turnover site (dotted rectangle) and CR: cartilage remnants

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