Laboratorio de Patología Celular y Molecular, Centro de Medicina Experimental, Instituto Venezolano de Investigaciones Científicas, Caracas, Miranda, Venezuela.
Stem Cells Dev. 2010 Mar;19(3):341-50. doi: 10.1089/scd.2009.0300.
Although the bone marrow (BM) microenvironment is the main inducer niche of early B lymphopoiesis during the adult life, other extramedullar microenvironments, such as the liver, may also have potential for supporting B-cell development. Previously, we reported that murine liver sinusoidal endothelial cells (LSECs) support in vitro and in vivo hematopoietic stem cell (HSC) proliferation and myeloid differentiation. In the present study, we investigated the capacity of LSEC to promote B lymphopoiesis from BM progenitor lineage-negative (Lin(-)) cells. Murine BM Lin(-) cells were co-cultured with LSEC, in the absence of exogenous cytokines. B cells were characterized by flow cytometry and cytokine expression by RT-PCR. We show that BM Lin(-) cells differentiated to early B-lymphoid progenitors (B220(+)) and subsequently to mature (CD19(+)) B cells. Functional studies showed the presence of a high number of non-adherent cells (NACs), collected from lipopolysaccharide (LPS)-treated Lin(-)/LSEC co-cultures, expressing IgM on their surface (sIgM). Colony formation from NAC was observed in the presence of IL-7 (CFU-IL-7). LSEC constitutively express IL-7, Flt-3L, and SCF at the mRNA level, and VCAM-1 on their surface, which may explain the capacity of these cells to promote B lymphopoiesis. These data demonstrate that LSEC promote all stages of B lymphopoiesis. To our knowledge, this is the first report that LSEC constitute an in vitro microenvironment for B lymphopoiesis. Further studies will establish whether LSEC can serve in vivo as a B-lymphopoietic niche under physiological or pathological condition, or when HSC are mobilized.
尽管骨髓（BM）微环境是成年期早期 B 淋巴发生的主要诱导龛位，但其他骨髓外微环境，如肝脏，也可能具有支持 B 细胞发育的潜力。此前，我们报道了鼠肝窦内皮细胞（LSEC）支持体外和体内造血干细胞（HSC）增殖和髓系分化。在本研究中，我们研究了 LSEC 促进 BM 祖细胞谱系阴性（Lin(-)）细胞向 B 淋巴发生的能力。将鼠 BM Lin(-)细胞与 LSEC 共培养，在没有外源性细胞因子的情况下。通过流式细胞术和 RT-PCR 检测细胞因子表达来鉴定 B 细胞。我们表明，BM Lin(-)细胞分化为早期 B 淋巴样祖细胞（B220(+)），随后分化为成熟（CD19(+)）B 细胞。功能研究表明，从 LPS 处理的 Lin(-)/LSEC 共培养物中收集的非黏附细胞（NAC）数量较多，其表面表达 IgM（sIgM）。在存在 IL-7（CFU-IL-7）的情况下观察到 NAC 的集落形成。LSEC 在 mRNA 水平上持续表达 IL-7、Flt-3L 和 SCF，并在其表面表达 VCAM-1，这可能解释了这些细胞促进 B 淋巴发生的能力。这些数据表明 LSEC 促进 B 淋巴发生的所有阶段。据我们所知，这是第一个报告 LSEC 构成体外 B 淋巴发生微环境的报告。进一步的研究将确定 LSEC 是否可以在生理或病理条件下或在 HSC 动员时在体内作为 B 淋系发生龛位发挥作用。
