Mural cells synthesize and deposit laminin to the basement membrane. To investigate the function of mural cell-derived laminin, we generated a mutant mouse line lacking mural cell-derived laminin (termed PKO). In a previous study, we showed that the PKO mice were grossly normal under homeostatic condition, but developed blood-brain barrier (BBB) breakdown with advanced age (> 8 months), suggesting that these mutants are intrinsically weak. Based on these findings, we hypothesized that PKO mice have exacerbated injuries in pathological conditions. Using collagenase-induced intracerebral hemorrhage (ICH) as an injury model, we examined various stroke outcomes, including hematoma volume, neurological function, neuronal death, BBB integrity, paracellular/transcellular transport, inflammatory cell infiltration, and brain water content, in PKO mice and their wildtype littermates at young age (6–8 weeks). In addition, transmission electron microscopy (TEM) analysis and an in vitro ICH model were used to investigate the underlying molecular mechanisms. Compared to age-matched wildtype littermates, PKO mice display aggravated stroke outcomes, including larger hematoma size, worse neurological function, increased neuronal cell death, enhanced BBB permeability, increased transcytosis, and elevated inflammatory cell infiltration. These mutants also exhibit high baseline brain water content independent of aquaporin-4 (AQP4). In addition, mural cell-derived laminin significantly reduced caveolin-1 without affecting tight junction proteins in the in vitro ICH model. These results suggest that mural cell-derived laminin attenuates BBB damage in ICH via decreasing caveolin-1 and thus transcytosis, regulates brain water homeostasis, and plays a beneficial role in ICH.

中文翻译：

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壁细胞来源的层粘连蛋白的丢失会加重出血性脑损伤


壁细胞合成层粘连蛋白并将其沉积到基底膜上。为了研究壁细胞源性层粘连蛋白的功能，我们产生了缺乏壁细胞源性层粘连蛋白的突变小鼠系（称为 PKO）。在之前的一项研究中，我们发现 PKO 小鼠在稳态条件下基本正常，但随着年龄的增长（> 8 个月），血脑屏障（BBB）发生了破坏，这表明这些突变体本质上很弱。基于这些发现，我们假设 PKO 小鼠在病理条件下加剧了损伤。使用胶原酶诱导的脑出血 (ICH) 作为损伤模型，我们检查了 PKO 小鼠的各种中风结局，包括血肿量、神经功能、神经元死亡、血脑屏障完整性、细胞旁/跨细胞转运、炎症细胞浸润和脑含水量以及它们的野生型同窝幼崽（6-8周）。此外，还使用透射电子显微镜 (TEM) 分析和体外 ICH 模型来研究潜在的分子机制。与年龄匹配的野生型同窝小鼠相比，PKO 小鼠表现出更严重的中风结果，包括血肿更大、神经功能更差、神经元细胞死亡增加、血脑屏障通透性增强、转胞吞作用增加和炎症细胞浸润增加。这些突变体还表现出独立于水通道蛋白 4 (AQP4) 的高基线脑含水量。此外，在体外 ICH 模型中，壁细胞来源的层粘连蛋白显着减少 Caveolin-1，而不影响紧密连接蛋白。这些结果表明，壁细胞来源的层粘连蛋白通过减少caveolin-1从而减弱转胞吞作用，从而减轻ICH中的BBB损伤，调节脑水稳态，并在ICH中发挥有益作用。