Department of Health Science and Technology, Neurobiology Research and Drug Delivery, Aalborg University, Aalborg, Denmark.
PLoS One. 2021 Mar 12;16(3):e0236770. doi: 10.1371/journal.pone.0236770. eCollection 2021.
The blood-brain barrier (BBB) is formed by brain capillary endothelial cells (BECs) supported by pericytes and astrocytes. The BBB maintains homeostasis and protects the brain against toxic substances circulating in the blood, meaning that only a few drugs can pass the BBB. Thus, for drug screening, understanding cell interactions, and pathology, in vitro BBB models have been developed using BECs from various animal sources. When comparing models of different species, differences exist especially in regards to the transendothelial electrical resistance (TEER). Thus, we compared primary mice, rat, and porcine BECs (mBECs, rBECs, and pBECs) cultured in mono- and co-culture with astrocytes, to identify species-dependent differences that could explain the variations in TEER and aid to the selection of models for future BBB studies. The BBB models based on primary mBECs, rBECs, and pBECs were evaluated and compared in regards to major BBB characteristics. The barrier integrity was evaluated by the expression of tight junction proteins and measurements of TEER and apparent permeability (Papp). Additionally, the cell size, the functionality of the P-glycoprotein (P-gp) efflux transporter, and the expression of the transferrin receptor were evaluated and compared. Expression and organization of tight junction proteins were in all three species influenced by co-culturing, supporting the findings, that TEER increases after co-culturing with astrocytes. All models had functional polarised P-gp efflux transporters and expressed the transferrin receptor. The most interesting discovery was that even though the pBECs had higher TEER than rBECs and mBECs, the Papp did not show the same variation between species, which could be explained by a significantly larger cell size of pBECs. In conclusion, our results imply that the choice of species for a given BBB study should be defined from its purpose, instead of aiming to reach the highest TEER, as the models studied here revealed similar BBB properties.
血脑屏障（BBB）由脑毛细血管内皮细胞（BEC）组成，由周细胞和星形胶质细胞支持。BBB 维持脑内环境稳定并保护大脑免受血液中循环的有害物质的侵害，这意味着只有少数药物可以通过 BBB。因此，为了进行药物筛选、了解细胞相互作用和病理学，已经使用来自各种动物来源的 BEC 开发了体外 BBB 模型。在比较不同物种的模型时，特别是在跨内皮电阻（TEER）方面存在差异。因此，我们比较了原代小鼠、大鼠和猪 BEC（mBEC、rBEC 和 pBEC）在与星形胶质细胞进行单核和共培养时的差异，以确定物种依赖性差异，这些差异可以解释 TEER 的变化，并有助于选择未来 BBB 研究的模型。基于原代 mBEC、rBEC 和 pBEC 的 BBB 模型在主要 BBB 特征方面进行了评估和比较。通过紧密连接蛋白的表达以及 TEER 和表观渗透系数（Papp）的测量来评估和比较屏障完整性。此外，还评估和比较了细胞大小、P-糖蛋白（P-gp）外排转运蛋白的功能以及转铁蛋白受体的表达。在所有三种物种中，紧密连接蛋白的表达和组织都受到共培养的影响，这支持了 TEER 在与星形胶质细胞共培养后增加的发现。所有模型都具有功能性极化 P-gp 外排转运蛋白，并表达转铁蛋白受体。最有趣的发现是，尽管 pBEC 的 TEER 高于 rBEC 和 mBEC，但 Papp 并没有显示出物种之间的相同变化，这可以通过 pBEC 细胞尺寸显著增大来解释。总之，我们的结果表明，对于给定的 BBB 研究，应根据其目的选择物种，而不是旨在达到最高的 TEER，因为这里研究的模型显示出相似的 BBB 特性。
