Sackstein Robert
Department of Dermatology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Methods Enzymol. 2010;479:93-105. doi: 10.1016/S0076-6879(10)79005-4.
The success of stem-cell-based regenerative therapeutics critically hinges on delivering relevant stem/progenitor cells to sites of tissue injury. To achieve adequate parenchymal infiltration following intravascular administration, it is first necessary that circulating cells bind to target tissue endothelium with sufficient strength to overcome the prevailing forces of hemodynamic shear. The principal mediators of these shear-resistant binding interactions consist of a family of C-type lectins known as "selectins" that bind discrete sialofucosylated glycans on their respective ligands. One member of this family, E-selectin, is an endothelial molecule that is inducibly expressed on postcapillary venules at all sites of tissue injury, but is also constitutively expressed on the luminal surface of bone marrow and dermal microvascular endothelium. Most stem/progenitor cells express high levels of CD44, and, in particular, human hematopoietic stem cells express a specialized sialofucosylated glycoform of CD44 known as "hematopoietic cell E-/L-selectin ligand" (HCELL) that functions as a potent E-selectin ligand. This chapter describes a method called "glycosyltransferase-programmed stereosubstitution" (GPS) for custom-modifying CD44 glycans to create HCELL on the surface of living cells that natively lack HCELL. Ex vivo glycan engineering of HCELL via GPS licenses trafficking of infused cells to endothelial beds that express E-selectin, thereby enabling efficient vascular delivery of stem/progenitor cells to sites where they are needed.
基于干细胞的再生疗法的成功关键在于将相关的干细胞/祖细胞输送到组织损伤部位。为了在血管内给药后实现足够的实质浸润，首先需要循环细胞以足够的强度与靶组织内皮细胞结合，以克服血流动力学剪切的主要力量。这些抗剪切结合相互作用的主要介质是一类称为“选择素”的C型凝集素家族，它们与各自配体上离散的唾液酸化岩藻糖基化聚糖结合。该家族的一个成员E-选择素是一种内皮分子，在所有组织损伤部位的毛细血管后微静脉上可诱导表达，但也在骨髓和真皮微血管内皮的腔表面组成性表达。大多数干细胞/祖细胞表达高水平的CD44，特别是人类造血干细胞表达一种特殊的唾液酸化岩藻糖基化糖型的CD44，称为“造血细胞E-/L-选择素配体”（HCELL），它作为一种有效的E-选择素配体发挥作用。本章描述了一种称为“糖基转移酶编程立体取代”（GPS）的方法，用于定制修饰CD44聚糖，以在天然缺乏HCELL的活细胞表面产生HCELL。通过GPS对HCELL进行体外聚糖工程改造，可使注入的细胞运输到表达E-选择素的内皮床，从而实现将干细胞/祖细胞有效地血管输送到需要它们的部位。
