Pinto do O P, Wandzioch E, Kolterud A, Carlsson L
Department of Microbiology, University of Umeå, Umeå, Sweden.
Exp Hematol. 2001 Aug;29(8):1019-28. doi: 10.1016/s0301-472x(01)00666-x.
Direct molecular and cellular studies of hematopoietic stem cells (HSCs) are hampered by the low levels of HSCs in hematopoietic tissues. To address these issues, we generated immortalized multipotent hematopoietic precursor cell (HPC) lines by expressing the LIM-homeobox gene Lhx2 (previously LH2) in hematopoietic progenitors derived from embryonic stem cells differentiated in vitro.
To validate further the relevance of the HPC lines as a model for normal HSCs, we analyzed in detail the growth requirements of HPC lines in vitro.
Lhx2 immortalized the HPC lines by a putatively novel and cell nonautonomous mechanism. Self-renewal of the HPC lines is dependent on functional Lhx2 expression. Most early-acting hematopoiesis-related growth factors show synergistic effects on the HPC lines, whereas late-acting factors do not induce differentiation by themselves. Transforming growth factor-beta(1) is a potent inhibitor of proliferation of the HPC lines. HPC lines form cobblestone areas with high efficiency when seeded onto stromal cell lines, and the cobblestone area-forming cell can be maintained in these cultures for several months.
Our data show that, in many respects, HPC lines are similar to normal hematopoietic progenitor/stem cells on the cellular level, in contrast to most previously described multipotent hematopoietic cell lines. The cell nonautonomous mechanism for immortalization of the HPC lines suggests that Lhx2 regulates, directly or indirectly, soluble mediators involved in self-renewal of the HPC lines.
造血组织中造血干细胞（HSC）水平较低，阻碍了对其进行直接的分子和细胞研究。为解决这些问题，我们通过在体外分化的胚胎干细胞来源的造血祖细胞中表达LIM同源盒基因Lhx2（先前的LH2），生成了永生化的多能造血前体细胞（HPC）系。
为进一步验证HPC系作为正常HSC模型的相关性，我们详细分析了HPC系在体外的生长需求。
Lhx2通过一种可能新颖的细胞非自主机制使HPC系永生化。HPC系的自我更新依赖于功能性Lhx2表达。大多数早期起作用的造血相关生长因子对HPC系显示出协同作用，而晚期起作用的因子自身不诱导分化。转化生长因子-β(1)是HPC系增殖的有效抑制剂。将HPC系接种到基质细胞系上时能高效形成鹅卵石区域，且形成鹅卵石区域的细胞可在这些培养物中维持数月。
我们的数据表明，在许多方面，HPC系在细胞水平上与正常造血祖细胞/干细胞相似，这与大多数先前描述的多能造血细胞系不同。HPC系永生化的细胞非自主机制表明，Lhx2直接或间接调节参与HPC系自我更新的可溶性介质。
