The blood-brain barrier studied in vitro across species

PLoS One. 2021 Mar 12;16(3):e0236770. doi: 10.1371/journal.pone.0236770. eCollection 2021.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B / genetics
  • ATP Binding Cassette Transporter, Subfamily B / metabolism
  • Animals
  • Astrocytes / cytology
  • Astrocytes / metabolism
  • Blood-Brain Barrier / metabolism*
  • Cell Culture Techniques
  • Cell Size
  • Cells, Cultured
  • Endothelial Cells / cytology
  • Endothelial Cells / metabolism
  • Mice
  • Models, Biological
  • Permeability
  • Rats
  • Receptors, Transferrin / genetics
  • Receptors, Transferrin / metabolism
  • Swine
  • Tight Junction Proteins / genetics
  • Tight Junction Proteins / metabolism

Substances

  • ATP Binding Cassette Transporter, Subfamily B
  • Receptors, Transferrin
  • Tight Junction Proteins

Grants and funding

The work was supported by grants from Fonden til Lægevidenskabens Fremme (https://www.apmollerfonde.dk/ansoegning/laegefonden/) (MST, NH, AB, LBT), Kong Christian d. X Fond (http://kongehuset.dk/node/5556) (NH), Fhv. Dir. Leo Nielsen og Hustru Karen Margrethe Nielsens Legat for Lægevidenskabelig Grundforskning (https://www.njordlaw.com/da/om-njord/fonde-og-legater/fhv-dir-leo-nielsen-og-hustru-karen-margrethe-nielsens-legat-for-laegevidenskabelig-grundforskning/) (MST), Augustinus fonden (https://augustinusfonden.dk/) (AB, LBT), Danielsens fond (https://danielsensfond.dk/)(AB, LBT), the Lundbeck Foundation Research Initiative on Brain Barriers and Drug Delivery (Grant no. R155-2013-14113) (https://www.lundbeckfonden.com/) (TM). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.