【国外标准】 Standard Test Method for Evaluating Growth of Engineered Cartilage Tissue using Magnetic Resonance Imaging

4.1 Tissue-engineered cartilage is prepared by seeding stem cells or chondrocytes in a three-dimensional biodegradable scaffold under controlled growth conditions. It is expected that the cells will differentiate towards chondrogenic lineage and produce an ample amount of cartilage extracellular matrix proteins, proteoglycans, and collagen type-II. Longitudinal assessment is needed weekly for the first few weeks in vitro and monthly at a later stage in vivo to determine the growth rate of tissue-engineered cartilage. Traditional testing methods such as histological staining, mechanical testing, and qPCR are invasive, destructive, and cannot be performed in vivo after the transplantation of engineered tissue as a regenerative treatment. In the regenerative medicine of cartilage, it is important to evaluate whether the implanted tissue regenerates as an articular cartilage over time. MRI is the only available non-invasive imaging modality that is utilized for post-operative monitoring and assessment of cartilage regeneration in clinics. Therefore, it is important to evaluate tissue-engineered cartilage using MRI at the preclinical stage as well.4.7.1 The change in calculated relaxation rate, R2(ECM), using Eq 1 have been found to be positively correlated with tissue growth (3, 6).1.1 This standard is intended as a standard test method for engineered cartilage tissue growth evaluation using MRI.1.2 This standard is intended for use in the development of tissue engineering regenerative medical products for cartilage damages, such as in knee, hip, or shoulder joints.1.3 This standard has been prepared for evaluation of engineered cartilage tissue growth at the preclinical stage and summarizes results from tissue growth evaluation of tissue-engineered cartilage in a few notable cases using water spin-spin relaxation time, T2, in vitro and in vivo in small animal models.1.4 This standard uses the change in mean T2 values as a function of growth time to evaluate the tissue growth of engineered cartilage.1.5 This standard provides a method to remove the scaffold contribution to the tissue growth evaluation.1.6 Information in this standard is intended to be applicable to most porous natural and synthetic polymers used as a scaffold in engineered cartilage, such as alginate, agarose, collagen, chitosan, and poly-lactic-co-glycolic acid (PLGA). However, some materials (both synthetic and natural) may require unique or varied methods of MRI evaluation that are not covered in this test method.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.