Institute for Surgical Research in the Walter-Brendel-Centre of Experimental Medicine, University of Munich Medical Center, Marchioninistr, 15, 81377 Munich, Germany.
J Neuroinflammation. 2013 Feb 28;10:32. doi: 10.1186/1742-2094-10-32.
Leukocytes are believed to be involved in delayed cell death following traumatic brain injury (TBI). However, data demonstrating that blood-borne inflammatory cells are present in the injured brain prior to the onset of secondary brain damage have been inconclusive. We therefore investigated both the interaction between leukocytes and the cerebrovascular endothelium using in vivo imaging and the accumulation of leukocytes in the penumbra following experimentally induced TBI.
Experimental TBI was induced in C57/Bl6 mice (n = 42) using the controlled cortical impact (CCI) injury model, and leukocyte-endothelium interactions (LEI) were quantified using both intravital fluorescence microscopy (IVM) of superficial vessels and 2-photon microscopy of cortical vessels for up to 14 h post-CCI. In a separate experimental group, leukocyte accumulation and secondary lesion expansion were analyzed in mice that were sacrificed 15 min, 2, 6, 12, 24, or 48 h after CCI (n = 48). Finally, leukocyte adhesion was blocked with anti-CD18 antibodies, and the effects on LEI and secondary lesion expansion were determined 16 (n = 12) and 24 h (n = 21), respectively, following TBI.
One hour after TBI leukocytes and leukocyte-platelet aggregates started to roll on the endothelium of pial venules, whereas no significant LEI were observed in pial arterioles or in sham-operated mice. With a delay of >4 h, leukocytes and aggregates did also firmly adhere to the venular endothelium. In deep cortical vessels (250 μm) LEIs were much less pronounced. Transmigration of leukocytes into the brain parenchyma only became significant after the tissue became necrotic. Treatment with anti-CD18 antibodies reduced adhesion by 65%; however, this treatment had no effect on secondary lesion expansion.
LEI occurred primarily in pial venules, whereas little or no LEI occurred in arterioles or deep cortical vessels. Inhibiting LEI did not affect secondary lesion expansion. Importantly, the majority of migrating leukocytes entered the injured brain parenchyma only after the tissue became necrotic. Our results therefore suggest that neither intravascular leukocyte adhesion nor the migration of leukocytes into cerebral tissue play a significant role in the development of secondary lesion expansion following TBI.
白细胞被认为参与创伤性脑损伤（TBI）后的延迟性细胞死亡。然而，关于血液来源的炎症细胞在继发性脑损伤发生前存在于损伤大脑中的数据尚无定论。因此，我们使用活体成像技术研究了白细胞与脑血管内皮之间的相互作用，并研究了实验性 TBI 后白细胞在半影区的聚集。
使用皮质撞击（CCI）损伤模型在 C57/Bl6 小鼠（n = 42）中诱导实验性 TBI，并使用活体荧光显微镜（IVM）对浅层血管和皮质血管的 2 光子显微镜对白细胞-内皮相互作用（LEI）进行定量，直至 CCI 后 14 小时。在另一个实验组中，分析了在 CCI 后 15 分钟、2 小时、6 小时、12 小时、24 小时或 48 小时处死的小鼠中的白细胞聚集和继发性病变扩展（n = 48）。最后，用抗 CD18 抗体阻断白细胞黏附，并分别在 TBI 后 16 小时（n = 12）和 24 小时（n = 21）确定其对 LEI 和继发性病变扩展的影响。
TBI 后 1 小时，白细胞和白细胞-血小板聚集体开始在软脑膜静脉内皮上滚动，而在软脑膜动脉或假手术小鼠中未观察到明显的 LEI。延迟 >4 小时后，白细胞和聚集体也牢固地黏附在静脉内皮上。在深部皮质血管（250μm）中，LEI 则不太明显。白细胞穿过血管内皮进入脑实质仅在组织坏死后才变得明显。用抗 CD18 抗体治疗可使黏附减少 65%；然而，这种治疗对继发性病变扩展没有影响。
LEI 主要发生在软脑膜静脉中，而在动脉或深部皮质血管中很少或没有 LEI。抑制 LEI 不会影响继发性病变扩展。重要的是，大多数迁移的白细胞仅在组织坏死后才进入损伤的脑实质。因此，我们的结果表明，血管内白细胞黏附或白细胞进入脑组织都不会在 TBI 后继发性病变扩展的发展中起重要作用。
