Francesco Santini PhD, Abstract Co-Author: Nothing to Disclose

Michele Pansini MD, Abstract Co-Author: Nothing to Disclose

Lukas Daniel Iselin MD, Abstract Co-Author: Nothing to Disclose

Marina Barandun MD, Abstract Co-Author: Nothing to Disclose

Dirk Schaefer, Abstract Co-Author: Nothing to Disclose

Ulrich Studler MD, Presenter: Nothing to Disclose

Ivan Martin, Abstract Co-Author: Nothing to Disclose

Oliver Bieri PhD, Abstract Co-Author: Nothing to Disclose

Andrea Barbero PhD, Abstract Co-Author: Nothing to Disclose

This study aims to investigate whether glycosaminoglycans (GAG) concentration in the cartilage layer of engineered osteochondral (OC) grafts and native cartilage tissues evaluated by the dGEMRIC method correlates with the biochemically measured GAG content in the same specimens.  

Chondrocytes isolated from 5 donors (mean age 36 years) were expanded in monolayer and then seeded onto collagen matrices. The constructs were combined with a processed bone scaffold after 3 days of pre-culture in chondrogenic medium. Combined constructs were further cultured in chondrogenic medium for a total time of 4 weeks. Control samples were generated gluing native articular cartilage tissues on the top of the bone scaffold. The samples were scanned on a whole-body 3T MRI scanner with a 3D variable flip angle gradient echo sequence for T1 quantification [2] (flip angles 4° and 15°, resolution 0.6.0.6x0.6mm3, FOV 150x37x34mm3, NEX 32) in a phosphate-buffered saline bath, before and 4 hours after addition of Gd-DTPA to a concentration of 1mM. Absolute GAG concentration was calculated from the measured T1 values in a middle slice of each sample using Donnan equilibrium theory [1]. The samples were subsequently extracted and the GAG content for each sample was biochemically calculated as mgGAG/mgDNA.  

The dGEMRIC-estimated GAG concentrations averaged 32.7±4.2 mg/ml for native cartilage and 4.9±1.9 mg/ml for the engineered cartilage (p<0.001). The biochemically measured GAG contents averaged 363.3±32.2mg/mg for the native and 22.7±4.4mg/mg for the engineered cartilage. There was a moderate correlation between the two techniques (R2=0.59).  

dGEMRIC was able to successfully differentiate between the native cartilage and the tissue engineered constructs. The correlation could likely be improved on samples of larger volume, as the in vivo implanted tissue would suffer less from partial volume effects from neighboring structures and media. dGEMRIC methods might be used to quantitatively monitor cartilage matrix remodeling/maturation in engineered tissues following implantation in the patients. References [1] Bashir A, et al, Magn Reson Med 1999; 41: 857–865. [2] Deoni S, et al, Magn Reson Med, 49: 515–526.  

Noninvasive radiological assessment of the health status of implanted tissue-engineered cartilage graft is important for patient recovery monitoring and therapeutical decisions.  

Santini, F, Pansini, M, Iselin, L, Barandun, M, Schaefer, D, Studler, U, Martin, I, Bieri, O, Barbero, A, Non Invasive in Vitro Evaluation of Tissue Engineered Cartilage through dGEMRIC.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14017594.html