ABSTRACT
Background:
The field of
orthopedics seeks effective, safer
methods for evaluating
articular cartilage regeneration. Despite various
treatment innovations, non-invasive, contrast-free full quantitative assessments of
hyaline articular cartilage's regenerative potential using compositional
magnetic resonance (MR) sequences remain challenging. In this context, our aim was to investigate the
effectiveness of different MR sequences for quantitative assessment of
cartilage and to compare them with the current
gold standard delayed
gadolinium-enhanced MR imaging of
cartilage (dGEMRIC) measurements.
Methods:
We employed ex vivo imaging in a preclinical
minipig model to assess
knee cartilage regeneration. Standardized osteochondral defects were drilled in the proximal
femur of the specimens (n=14), which were divided into four groups. Porcine
collagen scaffolds seeded with autologous adipose-derived
stromal cells (ASC), autologous
bone marrow stromal cells (BMSC), and unseeded scaffolds (US) were implanted in femoral defects. Furthermore, there was a defect group which received no
treatment. After 6 months, the specimens were examined using different compositional MR
methods, including the
gold standard dGEMRIC as well as T1, T2, T2*, and T1ρ
techniques. The statistical evaluation involved comparing the defect region with the uninjured
tibia and
femur cartilage layers and all measurements were performed on a clinical 3T MR Scanner.
Results:
In the untreated defect group, we observed significant differences in the defect region, with dGEMRIC values significantly lower (404.86±64.2 ms, P=0.018) and T2 times significantly higher (44.24±2.75 ms, P<0.001). Contrastingly, in all three
treatment groups (ASC, BMSC, US), there were no significant differences among the three regions in the dGEMRIC sequence, suggesting successful
cartilage regeneration. However, T1, T2*, and T1ρ sequences failed to detect such differences, highlighting their lower
sensitivity for
cartilage regeneration.
Conclusions:
As expected, dGEMRIC is well suited for
monitoring cartilage regeneration. Interestingly, T2 imaging also proved to be a reliable
cartilage imaging
technique and thus offers a
contrast agent-free alternative to the former
gold standard for subsequent in vivo studies investigating the
cartilage regeneration potential of different
treatment modalities.