Due to their positive charge cationic polymers attach to negatively charged surface of the superficial urothelial cells causing the disruption of tight junctions and consequent desquamation of these cells. Because of these properties their use as potential auxiliary therapeutic agents for elimination of infected urothelial cells or cancer urothelial cells has recently been increasing. Polysaccharide chitosan as one of cationic polymers has already been proved as a successful desquamating substance and also as an auxiliary therapeutic substance for treatment of bacterial cystitis in mice.
We used scanning electron microscopy to find out whether poly-L-lysine, which is a cationic polypeptide, causes desquamation of mouse urinary bladder urothelium. The aim of our study was to find out if the effect of poly-L-lysine depended on its concentration and molecular weight and also to determine, at which concentration and molecular weight the effect of poly-L-lysine was optimal.
Our experiments confirmed that poly-L-lysine caused the disruption of tight junctions and desquamation of mouse urinary bladder urothelium in in vivo conditions. We found out that both concentration and molecular weight of poly-L-lysine had influence on the extent of cell desquamation. Treatment with higher molecular weight (70-150 kDa) and higher concentration (0,01%) of poly-L-lysine causes more extensive desquamation of urothelial cells than treatment with lower molecular weight (30-70 kDa) and lower concentration (0,001%) of poly-L-lysine. Based on all our results we can conclude that the optimal desquamating substance is the 0,01% poly-L-lysine with molecular weigh of 70-150 kDa because it causes extensive desquamation of solely superficial cells without damaging the other cell layers of the urothelium.