基于多模态磁共振成像定量监测KGN/USPIO双标记组织工程水凝胶诱导BMSCs定向分化促进软骨修复的实验研究

Self-repair of damaged articular cartilage remains challenging because the tissue is avascular. In recent decades, many encouraging results for cartilage restoration were obtained in tissue engineering cell therapy and regenerative medicine. However, very few studies were devoted to non-invasively monitor hydrogel degradation and efficiently evaluate cartilage restoration in situ. In our previous studies, a ultrasmall superparamagnetic iron oxide (USPIO)-labeled hydrogel system was developed to track the hydrogel degradation during cartilage regeneration by the quantitative MRI. Following on from those results, we innovatively design a KGN/USPIO labeled and bone marrow-derived mesenchymal stem cells seeded hydrogel theranostic system that allows simultaneously tracking of hydrogel scaffold degradation, KGN release, and neocartilage formed in vivo by multimodal MRI. We will evaluate the physicochemical characterization and biocompatibility of the hydrogel system. The in vitro and in vivo release of KGN will be monitored longitudinally using chemical exchange saturation transfer (CEST) MRI scan sequence, while the degradation of USPIO-labeled hydrogel constructs and cartilage regeneration will be assessed simultaneously with T2 mapping and 3D_WATSc sequences, respectively. Histological analysis will further confirm the multiparametric MRI results in a rabbit cartilage defect model. Independent of cell-therapy regeneration medicine strategies, this tissue-engineered hydrogel scaffold system combined with functional MRI opens the possibility to provide a practical approach to noninvasively monitor and effectively promote chondrogenesis.

关节软骨由于缺乏血液供应，其缺损修复是具有挑战性的临床问题。组织工程支架负载细胞移植治疗是实现软骨再生的优选策略。然而，如何无创监测支架材料降解及软骨再生修复等体内信息是亟待解决的关键科学问题。本研究在前期制备基于超顺磁性氧化铁(USPIO)混合水凝胶体系用于软骨修复的定量MRI评价基础上，提出进一步接枝活性分子Kartogenin（KGN）诱导间充质干细胞定向软骨分化构建双标记水凝胶体系，通过多模态MRI实现支架降解、KGN缓释及软骨再生同步无创监测的科学假说。拟表征水凝胶体系的理化性质和生物相容性，分别使用化学交换饱和转移(CEST)、T2mapping和3D_WATSc序列实施体内外定量评价，并在兔软骨缺损模型上使用病理检查验证多参数MRI结果。区别于以往软骨再生医学单纯治疗策略，本研究从MRI功能成像与组织工程支架体系结合的新视点出发，有望为软骨损伤修复诊治一体的临床转化奠定基础。

软骨损伤后的再生在临床上仍然是一个巨大的挑战，因为软骨缺乏血供且增殖能力差。在本项目资助下，我们设计并构建了一种新型生物相容的纤维素纳米晶体/GelMA（甲基丙烯酸明胶酸酐）/HAMA（甲基丙烯酸透明质酸酸酐）与合成黑色素纳米颗粒（SMNP）和用于治疗目的的生物活性药物kartogenin（KGN）共混水凝胶支架系统。实验结果表明，SMNP-KGN/凝胶显示出良好的机械性能、热稳定性和明显的磁共振成像（MRI）对比增强效果。同时，KGN的持续释放可持续招募骨源性间充质干细胞增殖并分化为软骨细胞，从而促进体外和体内软骨再生。通过12周的多参数MRI同时监测水凝胶降解和软骨修复，并通过组织学分析进一步证实。这些结果证实了多功能水凝胶是无创成像引导精确治疗的具有转化前景的软骨再生组织工程平台。