Size and charge selective permeability defects induced in glomerular basement membrane by a polycation

Area of Science:

• Nephrology
• Biochemistry
• Materials Science

Background:

• The glomerular basement membrane (GBM) acts as a size and charge barrier to filtration.
• Polyethyleneimine (PEI) is a cationic polymer with potential applications in drug delivery and biomaterials.
• Understanding PEI's interaction with the GBM is crucial for assessing its renal safety and efficacy.

Purpose of the Study:

• To investigate the effect of intravenously administered PEI on the permeability of the rat glomerular basement membrane (GBM).
• To determine if PEI alters GBM permeability through charge neutralization or other mechanisms.
• To evaluate the influence of ferritin charge on PEI-mediated changes in GBM permeability.

Main Methods:

• Rats received intravenous PEI followed by native or cationic ferritins.
• Kidney tissue was examined using electron microscopy after 15 minutes.
• PEI-induced permeability was quantified as the ratio of ferritin particles in PEI-treated versus control groups (PEI/C).

Main Results:

• PEI significantly increased native ferritin passage across the GBM (PEI/C ratio of 107).
• PEI enhanced the permeation of cationic ferritins with lower isoelectric points (pI 7.5-8.2 and 8.0-8.7).
• Conversely, PEI decreased the permeation of the most cationic ferritin (pI 8.7-9.0), indicating an inverse relationship with cationic charge.

Conclusions:

• PEI markedly disrupts the GBM's charge barrier, as evidenced by increased native ferritin passage.
• PEI's effect on cationic ferritin permeation is complex, suggesting mechanisms beyond simple charge neutralization.
• The findings highlight PEI's significant impact on renal filtration dynamics and underscore the importance of polymer charge in such interactions.