T2 and Apparent Diffusion Coefficient of MRI Reflect Maturation of Tissue-Engineered Auricular Cartilage Subcutaneously Transplanted in Rats

Abstract

In cartilage regenerative medicine, autologous chondrocyte implantation (ACI) has been applied clinically for partial defects of joint cartilage or nasal augmentation. To make treatment with ACI more effective and prevalent, modalities to evaluate the quality of transplanted constructs noninvasively are necessary. In this study, we compared the efficacy of several noninvasive modalities for evaluating the maturation of tissue-engineered auricular cartilage containing a biodegradable polymer scaffold. We first transplanted tissue-engineered cartilage consisting of human auricular chondrocytes, atelocollagen gel, and a poly-l-lactic acid (PLLA) porous scaffold subcutaneously into the back of athymic nude rats. Eight weeks after transplantation, the rats were examined by magnetic resonance imaging (MRI), X-ray, and ultrasound as noninvasive modalities. Then, the excised constructs were examined by histological and biochemical analysis including toluidine blue (TB) staining, glycosaminoglycans content, and enzyme-linked immunosorbent assay of type II collagen. Among the modalities examined, transverse relaxation time (T2) and apparent diffusion coefficient of MRI showed quite a high correlation with histological and biochemical results, suggesting that these can effectively detect the maturation of tissue-engineered auricular cartilage. Since these noninvasive modalities would realize time-course analysis of the maturation of tissue-engineered auricular cartilage, this study provides a substantial insight for improving the quality of tissue-engineered cartilage, leading to improvement of the quality and technique in cartilage regenerative medicine.

Three-dimensional changes of noses after transplantation of implant-type tissue-engineered cartilage for secondary correction of cleft lip–nose patients

“…10 ). The findings resembled those of experimental transplantation in nude rats [18] . However, it appeared different from the morphology of repaired actual articular cartilage reported to show prominently high intensity on fsT2 images of MRI [10] .…”

Quantitative T2 mapping monitoring the maturation of engineered elastic cartilage in a rabbit model

“…Comparing the T2 values among AC, EC, and SF groups, we con rmed that MRI could indicate the difference between normal cartilage, engineered elastic cartilage, and brous tissue. Moreover, the T2 value showed a better correlation with GAG and HYP contents of tissue-engineered cartilage, which was consistent with other studies (14,18,23). Especially, the T2 value showed a high coe cient of more than 0.88 with elastin content, suggesting the feasibility of MRI T2 mapping in evaluating engineered elastic cartilage.…”

“…The ECM of cartilage mainly consists of water (60-85% of wet weight) and macromolecules such as collagen bers and proteoglycan (12). Speci cally, T1 relaxation time was found to be highly correlated with the proteoglycan content, and water apparent diffusion coe cient (ADC) were found to re ect the total amount of collagen and proteoglycans (13,14).…”

Developing quantitative MRI parameters to characterize host response and tissue ingrowth into collagen scaffolds

“…Previous studies have reported changes in T 2 and/or ADC values to be associated with other mechanisms like ECM architecture remodeling, [24][25][26][27] fibrous tissue formation, [28][29][30] tissue hydration, 26,[31][32][33] and inflammation, [34][35][36] which may occur concurrently with cellular infiltration and hence affect the T 2 and ADC values. Moreover, the relationship between total cellularity, T 2 , and ADC values has also been well documented in the cancer literature.…”