Introduction

Injury to articular cartilage has a high prevalence in the general population and athletes. Regeneration or repair of chondral tissue would be of vital importance to patients with symptomatic chondral joint injury, which has become an important problem with a high financial cost. Mesenchymal stromal cells (MSC) showed the capacity for expansion and chondrogenic differentiation, proving to be useful for the treatment of chondral lesions. The use of a scaffold-free tissue-engineered compound (TEC) avoided the need for a scaffold and turn the procedure safer. The assessment of the treatment of chondral lesions can be performed non-invasively with magnetic resonance imaging (MRI), which allows the analysis of the morphology and composition of the repair tissue. Magnetic field MRI of 7.0 Tesla provides images with a higher resolution in a shorter acquisition time. This study aims to evaluate cartilage regeneration with TEC using magnetic resonance imaging. METHODS: The TEC was developed in a center for cell therapy with mesenchymal stromal cells cultured at high density and left in suspension to form a three-dimensional structure. A cartilage defect on both knees (hind limbs) was performed on 14 miniature pigs. TEC was applied to one knee of each animal, totalizing 14 knees with TEC (experimental group) and 14 with chondral defect only (defect group). After 6 months, 7.0-T magnetic resonance imaging of the 28 knees was performed to evaluate morphology and repair quality with MOCART 3D score, and compositional characteristics of repair site with T2 mapping. The mean T2 value of two regions of interest (ROI) in each knee were calculate, one region regarded to repair site and the other regarded to healthy cartilage in the weight-bearing zone. RESULTS: The morphological evaluation showed greater filling of the cartilage defect fulfilled with MSC compared to the defect group. The MOCART 3D score value of animals submitted to TEC showed an average value of 62.3 (±12.3). While the group submitted only to defect presented a result with an average of 46.2 (±13.4). The compositional evaluation by T2 mapping showed that the repair tissue of the experimental group has a mean T2 value (53,42 ± 2,1) close to the mean T2 value of healthy cartilage (54,73 ± 2,28). And the mean T2 value of the repair area (50,98 ± 2,48) was significantly different from the mean T2 value of healthy cartilage (54,49 ± 1,72) in the defect group. CONCLUSION: The evaluation of the morphology and composition of the chondral repair with resonance image shows the promising potential of using MSC to treat cartilage injuries using a scaffold-free compound.