Howson K M, Aplin A C, Gelati M, Alessandri G, Parati E A, Nicosia R F
Division of Pathology and Laboratory Medicine (S-113-Lab Veterans Affairs Puget Sound Health Care System, 1660 South Columbian Way, Seattle, WA 98108, USA.
Am J Physiol Cell Physiol. 2005 Dec;289(6):C1396-407. doi: 10.1152/ajpcell.00168.2005. Epub 2005 Aug 3.
Pericytes play an important role in modulating angiogenesis, but the origin of these cells is poorly understood. To evaluate whether the mature vessel wall contains pericyte progenitor cells, nonendothelial mesenchymal cells isolated from the rat aorta were cultured in a serum-free medium optimized for stem cells. This method led to the isolation of anchorage-independent cells that proliferated slowly in suspension, forming spheroidal colonies. This process required basic fibroblast growth factor (bFGF) in the culture medium, because bFGF withdrawal caused the cells to attach to the culture dish and irreversibly lose their capacity to grow in suspension. Immunocytochemistry and RT-PCR analysis revealed the expression of the precursor cell markers CD34 and Tie-2 and the absence of endothelial cell markers (CD31 and endothelial nitric oxide synthase, eNOS) and smooth muscle cell markers (alpha-smooth muscle actin, alpha-SMA). In addition, spheroid-forming cells were positive for NG2, nestin, PDGF receptor (PDGFR)-alpha, and PDGFR-beta. Upon exposure to serum, these cells lost CD34 expression, acquired alpha-SMA, and attached to the culture dish. Returning these cells to serum-free medium failed to restore their original spheroid phenotype, suggesting terminal differentiation. When embedded in collagen gels, spheroid-forming cells rapidly migrated in response to PDGF-BB and became dendritic. Spheroid-forming cells cocultured in collagen with angiogenic outgrowths of rat aorta or isolated endothelial cells transformed into pericytes. These results demonstrate that the rat aorta contains primitive mesenchymal cells capable of pericyte differentiation. These immature cells may represent an important source of pericytes during angiogenesis in physiological and pathological processes. They may also provide a convenient supply of mural cells for vascular bioengineering applications.
周细胞在调节血管生成中发挥着重要作用，但这些细胞的起源却知之甚少。为了评估成熟血管壁是否含有周细胞祖细胞，从大鼠主动脉分离出的非内皮间充质细胞在针对干细胞优化的无血清培养基中培养。该方法导致分离出在悬浮液中缓慢增殖、形成球形集落的非贴壁依赖性细胞。这个过程需要培养基中的碱性成纤维细胞生长因子（bFGF），因为去除bFGF会导致细胞附着在培养皿上，并不可逆转地失去其在悬浮液中生长的能力。免疫细胞化学和RT-PCR分析显示前体细胞标志物CD34和Tie-2的表达，以及内皮细胞标志物（CD31和内皮型一氧化氮合酶，eNOS）和平滑肌细胞标志物（α-平滑肌肌动蛋白，α-SMA）的缺失。此外，形成球体的细胞对NG2、巢蛋白、血小板衍生生长因子受体（PDGFR）-α和PDGFR-β呈阳性。暴露于血清后，这些细胞失去CD34表达，获得α-SMA，并附着在培养皿上。将这些细胞重新置于无血清培养基中未能恢复其原始的球体表型，表明其发生了终末分化。当嵌入胶原凝胶中时，形成球体的细胞对血小板衍生生长因子-BB（PDGF-BB）有快速反应并迁移，变成树突状。与大鼠主动脉的血管生成芽或分离的内皮细胞在胶原中共培养时，形成球体的细胞转变为周细胞。这些结果表明，大鼠主动脉含有能够分化为周细胞的原始间充质细胞。这些未成熟细胞可能是生理和病理过程中血管生成期间周细胞的重要来源。它们也可能为血管生物工程应用提供便利的壁细胞来源。
