Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, 450 Technology Drive, Room 217, Pittsburgh, PA 15217, USA; Department of Orthopaedic Surgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.
Xiangya School of Medicine, Central South University, Changsha, Hunan, 410008, China.
Acta Biomater. 2022 Sep 1;149:150-166. doi: 10.1016/j.actbio.2022.06.040. Epub 2022 Jun 30.
Chondrocytic hypertrophy, a phenotype not observed in healthy hyaline cartilage, is often concomitant with the chondrogenesis of human mesenchymal stromal cells (hMSCs). This undesired feature represents one of the major obstacles in applying hMSCs for hyaline cartilage repair. Previously, we developed a method to induce hMSC chondrogenesis within self-generated extracellular matrix (mECM), which formed a cartilage tissue with a lower hypertrophy level than conventional hMSC pellets. In this study, we aimed to test the utility of hypoxia and insulin-like growth factor-1 (IGF1) on further reducing hypertrophy. MSC-mECM constructs were first subjected to chondrogenic culture in normoxic or hypoxic (5%) conditions. The results indicated that hMSC-derived cartilage formed in hypoxic culture displayed a significantly reduced hypertrophy level than normoxic culture. However, hMSC chondrogenesis was also suppressed under hypoxic culture, partially due to the reduced activity of the IGF1 pathway. IGF1 was then supplemented in the chondrogenic medium, which promoted remarkable hMSC chondrogenesis under hypoxic culture. Interestingly, the IGF1-enhanced hMSC chondrogenesis, under hypoxic culture, was not at the expense of promoting significantly increased hypertrophy. Lastly, the cartilage tissues created by hMSCs with different conditions were implanted into osteochondral defect in rats. The results indicated that the tissue formed under hypoxic condition and induced with IGF1-supplemented chondrogenic medium displayed the best reparative results with minimal hypertrophy level. Our results demonstrate a new method to generate hyaline cartilage-like tissue from hMSCs without using exogenous scaffolds, which further pave the road for the clinical application of hMSC-based cartilage tissue engineering. STATEMENT OF SIGNIFICANCE: In this study, hyaline cartilage-like tissues were generated from human mesenchymal stromal cells (hMSCs), which displayed robust capacity in repairing the osteochondral defect in rats. In particular, the extracellular matrix created by hMSCs was used, so no exogenous scaffold was needed. Through a series of optimization, we defined that hypoxic culture and supplementation of insulin-like growth factor-1 (IGF-1) in chondrogenic medium resulted in robust cartilage formation with minimal hypertrophy. We also demonstrated that hypoxic culture suppressed chondrogenesis and hypertrophy through modulating the Wnt/β-catenin and IGF1 pathways, respectively. Our results demonstrate a new method to generate hyaline cartilage-like tissue from hMSCs without using exogenous scaffolds, which will further pave the road for the clinical application of hMSCs-based cartilage tissue engineering.
软骨细胞肥大是一种在健康透明软骨中观察不到的表型，常伴随着人间质基质细胞（hMSC）的软骨生成。这种不理想的特征是应用 hMSC 进行透明软骨修复的主要障碍之一。先前，我们开发了一种在自身生成的细胞外基质（mECM）中诱导 hMSC 软骨生成的方法，该方法形成的软骨组织的肥大程度低于传统的 hMSC 微球。在这项研究中，我们旨在测试低氧和胰岛素样生长因子-1（IGF1）在进一步减少肥大方面的效用。首先将 MSC-mECM 构建体置于常氧或低氧（5%）条件下进行软骨形成培养。结果表明，在低氧培养中形成的 hMSC 来源的软骨显示出比常氧培养显著降低的肥大水平。然而，低氧培养也抑制了 hMSC 的软骨生成，部分原因是 IGF1 途径的活性降低。然后在软骨形成培养基中补充 IGF1，这促进了低氧培养下 hMSC 显著的软骨生成。有趣的是，在低氧培养下，IGF1 增强的 hMSC 软骨生成并没有以促进显著增加肥大为代价。最后，在不同条件下的 hMSC 产生的软骨组织被植入大鼠的骨软骨缺损中。结果表明，在低氧条件下形成并在补充 IGF1 的软骨形成培养基中诱导的组织显示出最佳的修复效果，肥大程度最小。我们的结果表明，无需使用外源性支架即可从 hMSC 生成透明软骨样组织的新方法，为基于 hMSC 的软骨组织工程的临床应用铺平了道路。意义声明：在这项研究中，从人间质基质细胞（hMSC）中生成了透明软骨样组织，其在修复大鼠的骨软骨缺损方面表现出强大的能力。特别是，hMSC 产生的细胞外基质无需使用外源性支架。通过一系列优化，我们确定低氧培养和在软骨形成培养基中补充胰岛素样生长因子-1（IGF-1）可导致肥大最小的强大软骨形成。我们还证明，低氧培养通过调节 Wnt/β-catenin 和 IGF1 途径分别抑制软骨生成和肥大。我们的结果表明，无需使用外源性支架即可从 hMSC 生成透明软骨样组织的新方法，为基于 hMSC 的软骨组织工程的临床应用铺平了道路。
