Institute of Molecular Cardiology, University of Louisville, KY, 40202, Louisville, USA.
Department of Immunology and Nano-Medicine, Florida International University, FL, 33199, Miami, USA.
Stem Cell Rev Rep. 2021 Jun;17(3):900-910. doi: 10.1007/s12015-020-10106-6. Epub 2021 Jan 3.
Cardiac mesenchymal cells (CMCs), a newly-discovered and promising type of progenitor cells, are effective in improving cardiac function in rodents after myocardial infarction. Stem/progenitor cells are usually cultured at atmospheric O tension (21%); however, the physiologic O tension in the heart is ~5%, raising the concern that 21% O may cause toxicity due to oxidative stress. Thus, we compared mouse CMCs cultured at 21% or 5% O beginning at passage 2. At passage 5, CMCs underwent severe hypoxic stress (1% O for 24 h). Compared with CMCs cultured at 21% O, culture at 5% O consistently improved cell morphology throughout 5 passages, markedly decreased cell size, increased cell number, shortened cell doubling time, and dramatically reduced lactate dehydrogenase release from CMCs into culture media after hypoxic stress. Furthermore, culture at 5% O increased telomerase activity and telomere length, implying that 21% O tension impairs telomerase activity, resulting in telomere shortening and decreased cell proliferation. Thus far, almost all preclinical and clinical studies of cell therapy for the heart disease have used atmospheric (21%) O to culture cells. Our data challenge this paradigm. Our results demonstrate that, compared with 21% O, 5% O tension greatly enhances the competence and functional properties of CMCs. The increased proliferation rate at 5% O means that target numbers of CMCs can be achieved with much less time and cost. Furthermore, since this increased proliferation may continue in vivo after CMC transplantation, and since cells grown at 5% O are markedly resistant to severe hypoxic stress, and thus may be better able to survive after transplantation into scarred regions of the heart where O is very low, culture at 5% O may enhance the reparative properties of CMCs (and possibly other cell types). In conclusion, our data support a change in the methods used to culture CMCs and possibly other progenitor cells.
心脏间质细胞（CMCs）是一种新发现的、有前途的祖细胞类型，在心肌梗死后能有效改善啮齿动物的心脏功能。干细胞/祖细胞通常在大气氧张力（21%）下培养；然而，心脏的生理氧张力约为 5%，这让人担心 21%的氧可能由于氧化应激而产生毒性。因此，我们比较了在第 2 代时分别在 21%或 5%氧张力下培养的小鼠 CMCs。在第 5 代时，CMCs 经历了严重的低氧应激（1%氧，24 小时）。与在 21%氧下培养的 CMCs 相比，在 5%氧下培养始终能在 5 代过程中改善细胞形态，显著减小细胞大小，增加细胞数量，缩短细胞倍增时间，并显著减少低氧应激后 CMCs 向培养基中释放乳酸脱氢酶。此外，在 5%氧下培养还能增加端粒酶活性和端粒长度，这意味着 21%的氧张力会损害端粒酶活性，导致端粒缩短和细胞增殖减少。到目前为止，几乎所有用于心脏病的细胞治疗的临床前和临床研究都使用大气（21%）氧来培养细胞。我们的数据对这一范式提出了挑战。我们的结果表明，与 21%的氧相比，5%的氧张力能极大地增强 CMCs 的功能和性能。在 5%的氧中更高的增殖率意味着可以用更少的时间和成本达到目标数量的 CMCs。此外，由于在 CMC 移植后这种增殖可能会继续在体内发生，并且由于在 5%氧下生长的细胞对严重低氧应激具有显著的抵抗力，因此它们可能更能在移植到心脏瘢痕区域（那里的氧非常低）后存活，因此在 5%的氧中培养可能会增强 CMCs（和可能的其他细胞类型）的修复特性。总之，我们的数据支持改变培养 CMCs 和可能的其他祖细胞的方法。
