Gupta P, Oegema T R, Brazil J J, Dudek A Z, Slungaard A, Verfaillie C M
Departments of Medicine, Biochemistry, and Orthopaedic Surgery, VA Medical Center, University of Minnesota Medical School, Minneapolis, MN, USA.
Blood. 1998 Dec 15;92(12):4641-51.
Stem cell localization, conservation, and differentiation is believed to occur in niches in the marrow stromal microenvironment. Our recent observation that long-term in vitro human hematopoiesis requires a stromal heparan sulfate proteoglycan (HSPG) led us to hypothesize that such HSPG may orchestrate the formation of the stem cell niche. We compared the structure and function of HS from M2-10B4, a hematopoiesis-supportive cell line, with HS from a nonsupportive cell line, FHS-173-We. Long-term culture-initiating cell (LTC-IC) maintenance was enhanced by PG from supportive cells but not by PG from nonsupportive cells (P <.005). The supportive HS were significantly larger and more highly sulfated than the nonsupportive HS. Specifically, supportive HS contained higher 6-O-sulfation on the glucosamine residues. In agreement with these observations, purified 6-O-sulfated heparin and highly 6-O-sulfated bovine kidney HS similarly maintained LTC-IC. In contrast, completely desulfated heparin, N-sulfated heparin, and unmodified heparin did not support LTC-IC maintenance. Moreover, the supportive HS promoted LTC-IC maintenance but not differentiation of CD34(+)/HLA-DR- cells into colony-forming cells (CFCs) and mature blood cells. The supportive HS but not the nonsupportive HS bound both cytokines and matrix components critical for hematopoiesis, including interleukin-3 (IL-3), macrophage inflammatory protein-1 (MIP-1), and thrombospondin (TSP). Significantly more CD34(+) cells adhered directly to immobilized O-sulfated heparin than to N-sulfated or desulfated heparin. Thus, hematopoiesis-supportive stromal HSPG possessing large, highly 6-O-sulfated HS mediate the juxtaposition of hematopoietic progenitors with stromal cells, specific growth-promoting (IL-3) and growth-inhibitory (MIP-1 and platelet factor 4 [PF4]) cytokines, and extracellular matrix (ECM) proteins such as TSP. We conclude that the structural specificity of stromal HSPG that determines the selective colocalization of cytokines and ECM components leads to the formation of discrete niches, thereby orchestrating the controlled growth and differentiation of stem cells. These findings may have important implications for ex vivo expansion of and gene transfer into primitive hematopoietic progenitors.
干细胞的定位、维持及分化被认为发生于骨髓基质微环境的特定区域。我们最近观察到，长期体外培养人造血过程需要一种基质硫酸乙酰肝素蛋白聚糖（HSPG），这使我们推测这种HSPG可能参与干细胞特定区域的形成。我们比较了造血支持细胞系M2 - 10B4来源的HS与非支持细胞系FHS - 173 - We来源的HS的结构和功能。支持细胞来源的PG可增强长期培养起始细胞（LTC - IC）的维持，而非支持细胞来源的PG则无此作用（P <.005）。支持性HS比非支持性HS显著更大且硫酸化程度更高。具体而言，支持性HS在葡糖胺残基上含有更高的6 - O - 硫酸化修饰。与这些观察结果一致，纯化的6 - O - 硫酸化肝素和高度6 - O - 硫酸化的牛肾HS同样能维持LTC - IC。相反，完全去硫酸化的肝素、N - 硫酸化肝素和未修饰的肝素则不能支持LTC - IC的维持。此外，支持性HS可促进LTC - IC的维持，但不能促使CD34(+)/HLA - DR - 细胞分化为集落形成细胞（CFC）和成熟血细胞。支持性HS而非非支持性HS能结合对造血至关重要的细胞因子和基质成分，包括白细胞介素 - 3（IL - 3）、巨噬细胞炎性蛋白 - 1（MIP - 1）和血小板反应蛋白（TSP）。与N - 硫酸化或去硫酸化肝素相比，显著更多的CD34(+)细胞直接黏附于固定化的O - 硫酸化肝素。因此，具有大的、高度6 - O - 硫酸化HS的造血支持性基质HSPG介导造血祖细胞与基质细胞、特定的促生长（IL - 3）和生长抑制（MIP - 1和血小板因子4 [PF4]）细胞因子以及细胞外基质（ECM）蛋白（如TSP）的并置。我们得出结论，基质HSPG的结构特异性决定了细胞因子和ECM成分的选择性共定位，从而导致离散特定区域的形成，进而调控干细胞的可控生长和分化。这些发现可能对原始造血祖细胞的体外扩增和基因转移具有重要意义。
