Institute of Orthopedics, the First Medical Center, Chinese PLA General Hospital, Beijing Key Lab of Regenerative Medicine in Orthopedics, Key Laboratory of Musculoskeletal Trauma & War Injuries PLA, 28 Fuxing Road, Haidian District, Beijing, 100853, China; School of Medicine, Nankai University, Tianjin, 300071, China; Arthritis Clinic & Research Center, Peking University People's Hospital, Peking University, Beijing, 100044, China.
Institute of Orthopedics, the First Medical Center, Chinese PLA General Hospital, Beijing Key Lab of Regenerative Medicine in Orthopedics, Key Laboratory of Musculoskeletal Trauma & War Injuries PLA, 28 Fuxing Road, Haidian District, Beijing, 100853, China; Department of Orthopedics, the First Affiliated Hospital of Zhengzhou University, 1 Jian East Road, Erqi District, Zhengzhou, 450052, China.
Acta Biomater. 2022 Sep 15;150:181-198. doi: 10.1016/j.actbio.2022.07.029. Epub 2022 Jul 25.
Clinically, microfracture is the most commonly applied surgical technique for cartilage defects. However, an increasing number of studies have shown that the clinical improvement remains questionable, and the reason remains unclear. Notably, recent discoveries revealed that signals from regenerated niches play a critical role in determining mesenchymal stem cell fate specification and differentiation. We speculate that a microenvironmentally optimized scaffold that directs mesenchymal stem cell fate will be a good therapeutic strategy for cartilage repair. Therefore, we first explored the deficiency of microfractures in cartilage repair. The microfracture not only induced inflammatory cell aggregation in blood clots but also consisted of loose granulation tissue with increased levels of proteins related to fibrogenesis. We then fabricated a functional cartilage scaffold using two strong bioactive cues, transforming growth factor-β3 and decellularized cartilage extracellular matrix, to modulate the cell fate of mesenchymal stem cells. Additionally, poly(ε-caprolactone) was also coprinted with extracellular matrix-based bioinks to provide early mechanical support. The in vitro studies showed that microenvironmentally optimized scaffolds exert powerful effects on modulating the mesenchymal stem cell fate, such as promoting cell migration, proliferation and chondrogenesis. Importantly, this strategy achieved superior regeneration in sheep via scaffolds with biomechanics (restored well-organized collagen orientation) and antiapoptotic properties (cell death-related genes were also downregulated). In summary, this study provides evidence that microenvironmentally optimized scaffolds improve cartilage regeneration in situ by regulating the microenvironment and support further translation in human cartilage repair. STATEMENT OF SIGNIFICANCE: Although microfracture (MF)-based treatment for chondral defects has been commonly used, critical gaps exist in understanding the biochemistry of MF-induced repaired tissue. More importantly, the clinically unsatisfactory effects of MF treatment have prompted researchers to focus on tissue engineering scaffolds that may have sufficient therapeutic efficacy. In this manuscript, a 3D printing ink containing cartilage tissue-specific extracellular matrix (ECM), methacrylate gelatin (GelMA), and transforming growth factor-β3 (TGF-β3)-embedded polylactic-coglycolic acid (PLGA) microspheres was coprinted with poly(ε-caprolactone) (PCL) to fabricate tissue engineering scaffolds for chondral defect repair. The sustained release of TGF-β3 from scaffolds successfully directed endogenous stem/progenitor cell migration and differentiation. This microenvironmentally optimized scaffold produced improved tissue repair outcomes in the sheep animal model, explicitly guiding more organized neotissue formation and therefore recapitulating the anisotropic structure of native articular cartilage. We hypothesized that the cell-free scaffolds might improve the clinical applicability and become a new therapeutic option for chondral defect repair.
临床上，微骨折术是最常用于治疗软骨缺损的手术技术。然而，越来越多的研究表明，临床改善仍然值得怀疑，其原因尚不清楚。值得注意的是，最近的发现表明，再生龛位的信号在决定间充质干细胞命运特化和分化方面起着关键作用。我们推测，一种能够指导间充质干细胞命运的微环境优化支架将是一种治疗软骨修复的良好策略。因此，我们首先探讨了微骨折术在软骨修复中的缺陷。微骨折不仅在血块中诱导了炎症细胞聚集，而且还包含了富含与纤维化相关蛋白的疏松肉芽组织。然后，我们使用两种强生物活性线索转化生长因子-β3 和去细胞化软骨细胞外基质来制造功能化的软骨支架，以调节间充质干细胞的细胞命运。此外，聚（ε-己内酯）也与基于细胞外基质的生物墨水共打印，以提供早期的机械支撑。体外研究表明，微环境优化支架对调节间充质干细胞命运具有强大的作用，例如促进细胞迁移、增殖和软骨生成。重要的是，通过具有生物力学（恢复了组织有序的胶原取向）和抗细胞凋亡特性（细胞死亡相关基因也下调）的支架，该策略在绵羊中实现了卓越的再生。总之，这项研究提供了证据表明，通过调节微环境，微环境优化支架可以改善原位软骨再生，并支持在人类软骨修复中的进一步转化。
尽管基于微骨折（MF）的软骨缺损治疗已被广泛应用，但在理解 MF 诱导的修复组织的生物化学方面仍存在关键差距。更重要的是，MF 治疗的临床效果不尽如人意，促使研究人员关注可能具有足够治疗效果的组织工程支架。在本文中，一种含有软骨组织特异性细胞外基质（ECM）、甲基丙烯酰化明胶（GelMA）和嵌入聚乳酸-羟基乙酸共聚物（PLGA）微球的转化生长因子-β3（TGF-β3）-嵌段共聚物的 3D 打印墨水与聚（ε-己内酯）（PCL）共打印，用于制造软骨缺损修复的组织工程支架。支架中 TGF-β3 的持续释放成功地引导了内源性干细胞/祖细胞的迁移和分化。这种微环境优化的支架在绵羊动物模型中产生了更好的组织修复效果，明确地引导了更有组织的新生组织形成，从而再现了天然关节软骨的各向异性结构。我们假设无细胞支架可能会提高临床适用性，并成为软骨缺损修复的新治疗选择。
