To follow up on one of Nate’s posts from 2010, hair grows not only on your skin. He describes a glomerular capillary to be hairy. Glycocalyx, a hairy structure attached to the glomerular endothelium, is a mixture of glycosaminoglycans and proteoglycans. The picture of glycocalyx accompanying that post is quite impressive.
Now we know these hairs are coated with another gel matrix called endothelial surface layer (ESL). ESL, together with glycocalyx, is believed to function as a barrier to prevent protein passage from blood to urine. A recent article addressing this topic was published in JASN.
By using an animal model, the authors showed that loss of ESL increases the sieving co-efficient for albumin and that the degree of albuminuria correlates with the degree of ESL loss (by the way their confocal microscopy images of ESL are pretty cool).
The implication of the study is that it’s not just podocyte or GBM that are responsible for the development of proteinuria; ESL, glycocalyx and endothelium appear to play an important role as well. For example, loss of ESL has been reported in patients with diabetes. Maybe it’s not just on the skin where hair loss occurs.
For those who are interested in this topic, there is a nice review article for further reading.
Posted by Tomoki Tsukahara