Air-blood barrier #1

Our collaboration with Alison Elder, et al. in the Dept. of Environmental Medicine has led us to talk about developing a co-culture model of the air-blood barrier.  This barrier is ‘located’ at the alveolar sacs in the lungs, where lung epithelial cells in the alveolar space are exposed to air.  These epithelial cells are separated from a single layer of lung capillary endothelial cells by an interstitial space which is thicker than that of the BBB but still nanoscale (~50-100nm).  Relevant in vitro models of this barrier would allow more detailed exploration of the translocation of various inhaled substances (pollutants, nanoparticles, drugs) from the lungs into the bloodstream.  This post shows the results from the first successful in vitro model of this system.

Here, I used P9 bEnd3 as the endothelial cell component (even though it’s from brain) on the bottom side of transwells and the P11 RLE-6TN line as the epithelial component (Type II epithelium) on the apical side of transwells.  Both were seeded at 50000 cells/cm2.  The TEER data are below:

Interestingly, there was a more rapid increase in TEER on pnc-Si than on PET for both RLE and co-cultures.  This phenomenon was first seen with bEnd3 cells alone.  Also the % increase of TEER is higher on pnc-Si but there is only a transient peak.  It seems like the ABB co-culture TEER values are determined mainly by the RLE cells alone, which suggests that this co-culture system has additive (not synergistic) effects.

Live/Dead Staining showed normal morphologies for both cell types when cultured alone (remember that RLE are on the apical side so we can only image the cells over the free-standing membrane).  The morphology of bEnd on both transwells for the co-culture samples is a bit funky – kind of similar to that with BBB co-cultures.