利用人造血干细胞(human hematopoietic stem cells, hHSCs)治疗一系列疾病所面临的一个主要的障碍就是科学家们很难在体外培养它们.它们在体外要么很快死亡,要么分化为其他类型的细胞.在一项新的研究中,来自美国塔夫斯大学工程学院生物医学工程系的Dean Liang Glettig和David Kaplan通过一系列实验证实含有脂肪细胞的饲养层(feeder layer)能够成功地促进体外培养的hHSCs长期存活.相关研究结果于2013年3月12日在线发表在BioResearch Open Access期刊上,论文标题为"Extending Human Hematopoietic Stem Cell Survival In Vitro with Adipocytes".
为了在体外延长hHSCs的存活时间,研究人员一直试图利用人间充质干细胞(human mesenchymal stem cells, hMSCs)产生模拟造血干细胞微环境(hHSC niche)的饲养层.
在这项新的研究中,研究人员利用这些含有脂肪细胞的饲养层抑制hHSCs分化来开展一系列实验,以便验证hHSCs在体外的存活时间是否得到提高,并且在每项实验中,存活的hHSCs数量通过流式细胞仪进行定量.
在第一项实验中,研究人员比较了含有未分化的hMSCs的饲养层和利用基本培养基让hMSCs已分化为成骨细胞或脂肪细胞的饲养层,结果证实当饲养层含有脂肪细胞时,hHSCs拥有最高的存活率.在第二项实验中,研究人员比较了hMSCs饲养层和利用添加有hHSC生长因子混合物的培养基让hMSCs分化为脂肪细胞的饲养层,他们得出了同样的结论.
在第三项实验中,研究人员证实细胞之间直接接触是这些饲养层发挥支持性作用所必需的.在第四项和第五项实验中,研究人员改变饲养层中的脂肪细胞数量,而且在这两项实验中,他们都证实饲养层中含有较高数量的脂肪细胞让hHSCs数量在随后的时间中更不容易快速下降.
基于这一系列实验,研究人员作出结论：脂肪细胞有助于抑制hHSCs分化,从而有助于提高它们在体外的存活时间.
BioResearch Open Access期刊编辑Jane Taylor博士说,"提高体外培养的hHSCs的存活能力不仅有助于基础性干细胞研究,而且它也是开发先进的细胞疗法用于未来的临床应用所取得的重要一步."（生物谷Bioon.com）
doi:10.1089/biores.2013.0006
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Extending Human Hematopoietic Stem Cell Survival In Vitro with Adipocytes
Dean Liang Glettig and David L. Kaplan
Human hematopoietic stem cells (hHSCs) cannot be maintained in vitro for extended time periods because they rapidly differentiate or die. To extend in vitro culture time, researchers have made attempts to use human mesenchymal stem cells (hMSCs) to create feeder layers that mimic the stem cell niche. We have conducted an array of experiments including adipocytes in these feeder layers that inhibit hHSC differentiation and by that prolong stem cell survival in vitro. The amount of CD34+ cells was quantified using flow cytometry. In a first experiment, feeder layers of undifferentiated hMSCs were compared with feeder layers differentiated toward osteoblasts or adipocytes using minimal medium, showing the highest survival rate where adipocytes were included. The same conclusion was drawn in a second experiment in comparing hMSCs with adipogenic feeder cells, using a culture medium supplemented with a cocktail of hHSC growth factors. In a third experiment, it was shown that direct cell–cell contact is necessary for the supportive effect of the feeder layers. In a fourth and fifth experiment the amount of adipocytes in the feeder layers were varied, and in all experiments a higher amount of adipocytes in the feeder layers showed a less rapid decay of CD34+ cells at later time points. We therefore concluded that adipocytes assist in suppressing hHSC differentiation and aid in prolonging their survival in vitro.
