Table_1_Inability of Low Oxygen Tension to Induce Chondrogenesis in Human Infrapatellar Fat Pad Mesenchymal Stem Cells.DOCX

ObjectiveArticular cartilage of the knee joint is avascular, exists under a low oxygen tension microenvironment, and does not self-heal when injured. Human infrapatellar fat pad-sourced mesenchymal stem cells (IFP-MSC) are an arthroscopically accessible source of mesenchymal stem cells (MSC) for the repair of articular cartilage defects. Human IFP-MSC exists physiologically under a low oxygen tension (i.e., 1–5%) microenvironment. Human bone marrow mesenchymal stem cells (BM-MSC) exist physiologically within a similar range of oxygen tension. A low oxygen tension of 2% spontaneously induced chondrogenesis in micromass pellets of human BM-MSC. However, this is yet to be demonstrated in human IFP-MSC or other adipose tissue-sourced MSC. In this study, we explored the potential of low oxygen tension at 2% to drive the in vitro chondrogenesis of IFP-MSC. We hypothesized that 2% O2 will induce stable chondrogenesis in human IFP-MSC without the risk of undergoing endochondral ossification at ectopic sites of implantation.
MethodsMicromass pellets of human IFP-MSC were cultured under 2% O2 or 21% O2 (normal atmosphere O2) in the presence or absence of chondrogenic medium with transforming growth factor-β3 (TGFβ3) for 3 weeks. Following in vitro chondrogenesis, the resulting pellets were implanted in immunodeficient athymic nude mice for 3 weeks.
ResultsA low oxygen tension of 2% was unable to induce chondrogenesis in human IFP-MSC. In contrast, chondrogenic medium with TGFβ3 induced in vitro chondrogenesis. All pellets were devoid of any evidence of undergoing endochondral ossification after subcutaneous implantation in athymic mice.

研究目的：膝关节关节软骨无血管分布，处于低氧张力微环境，损伤后无法自我修复。人髌下脂肪垫来源间充质干细胞（human infrapatellar fat pad-sourced mesenchymal stem cells, IFP-MSC）是一类可通过关节镜获取的间充质干细胞（mesenchymal stem cell, MSC）来源，可用于修复关节软骨缺损。生理状态下，人IFP-MSC所处的氧分压范围为1%~5%，与人骨髓间充质干细胞（human bone marrow mesenchymal stem cells, BM-MSC）的生理氧分压范围相近。已有研究证实，2%低氧张力可自发诱导人BM-MSC微团球发生软骨分化，但该效应尚未在人IFP-MSC或其他脂肪来源MSC中得到验证。本研究旨在探究2%低氧张力驱动人IFP-MSC体外软骨分化的潜能，并提出假说：2% O₂可诱导人IFP-MSC发生稳定的软骨分化，且不会在异位植入部位引发软骨内骨化风险。

研究方法：将人IFP-MSC微团球分别置于2% O₂或21% O₂（常氧环境）中培养，同时添加或不添加含转化生长因子-β3（transforming growth factor-β3, TGFβ3）的软骨分化诱导培养基，培养周期为3周。完成体外软骨分化诱导后，将所得微团球植入免疫缺陷型无胸腺裸小鼠体内，继续培养3周。

研究结果：2%低氧张力无法单独诱导人IFP-MSC发生软骨分化；与之相反，添加TGFβ3的软骨分化诱导培养基可成功诱导其体外软骨分化。所有微团球在裸小鼠皮下植入后，均未观察到软骨内骨化的相关证据。