Carroll Simon F, Buckley Conor T, Kelly Daniel J
Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland.
Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin, Ireland.
Front Bioeng Biotechnol. 2021 May 25;9:591126. doi: 10.3389/fbioe.2021.591126. eCollection 2021.
Understanding how the local cellular environment influences cell metabolism, phenotype and matrix synthesis is crucial to engineering functional tissue grafts of a clinically relevant scale. The objective of this study was to investigate how the local oxygen environment within engineered cartilaginous tissues is influenced by factors such as cell source, environmental oxygen tension and the cell seeding density. Furthermore, the subsequent impact of such factors on both the cellular oxygen consumption rate and cartilage matrix synthesis were also examined. Bone marrow derived stem cells (BMSCs), infrapatellar fat pad derived stem cells (FPSCs) and chondrocytes (CCs) were seeded into agarose hydrogels and stimulated with transforming growth factor-β3 (TGF- β3). The local oxygen concentration was measured within the center of the constructs, and numerical modeling was employed to predict oxygen gradients and the average oxygen consumption rate within the engineered tissues. The cellular oxygen consumption rate of hydrogel encapsulated CCs remained relatively unchanged with time in culture. In contrast, stem cells were found to possess a relatively high initial oxygen consumption rate, but adopted a less oxidative, more chondrocyte-like oxygen consumption profile following chondrogenic differentiation, resulting in net increases in engineered tissue oxygenation. Furthermore, a greater reduction in oxygen uptake was observed when the oxygen concentration of the external cell culture environment was reduced. In general, cartilage matrix deposition was found to be maximal in regions of low oxygen, but collagen synthesis was inhibited in very low (less than 2%) oxygen regions. These findings suggest that promoting an oxygen consumption profile similar to that of chondrocytes might be considered a key determinant to the success of stem cell-based cartilage tissue engineering strategies.
了解局部细胞环境如何影响细胞代谢、表型和基质合成对于构建具有临床相关规模的功能性组织移植物至关重要。本研究的目的是调查工程化软骨组织内的局部氧气环境如何受到细胞来源、环境氧张力和细胞接种密度等因素的影响。此外，还研究了这些因素对细胞耗氧率和软骨基质合成的后续影响。将骨髓来源的干细胞（BMSC）、髌下脂肪垫来源的干细胞（FPSC）和软骨细胞（CC）接种到琼脂糖水凝胶中，并用转化生长因子-β3（TGF-β3）进行刺激。在构建体的中心测量局部氧气浓度，并采用数值模拟来预测工程组织内的氧气梯度和平均耗氧率。水凝胶包裹的CC的细胞耗氧率在培养过程中随时间保持相对不变。相比之下，干细胞具有相对较高的初始耗氧率，但在软骨形成分化后采用了氧化性较低、更类似软骨细胞的耗氧模式，导致工程组织氧合净增加。此外，当外部细胞培养环境的氧气浓度降低时，观察到氧气摄取的更大减少。一般来说，在低氧区域软骨基质沉积最大，但在极低（低于2%）氧区域胶原蛋白合成受到抑制。这些发现表明，促进类似于软骨细胞的耗氧模式可能被认为是基于干细胞的软骨组织工程策略成功的关键决定因素。
