Lipoprotein was used to study effect of the surface density of nano-segments immobilized on culture dishes on ex vivo expansion of hematopoietic stem and progenitor cells from umbilical cord blood. It was also used in the separation and cultivation of hematopoietic stem cells from umbilical cord blood by permeation through membranes with nano-segments.
Lipoprotein, low density (LDL) is synthesized by lipolysis and lipid transfer steps. They are formed from very low-density lipoprotein (VLDL) after uptake by LDL receptor in hepatocytes. LDL normal level of 130 mg/dL is desirable in human plasma. It is referred as bad cholesterol.
LDL and HDL transport both dietary and endogenous cholesterol in the plasma. LDL is the main transporter of cholesterol and cholesteryl esters and makes up more than half of the total lipoprotein in plasma. LDL is absorbed by the liver and other tissues via receptor mediated endocytosis. The cytoplasmic domain of the LDL receptor facilitates the formation of coated pits; receptor-rich regions of the membrane. The ligand binding domain of the receptor recognizes apo-B100 on LDL, resulting in the formation of a clathrin-coated vesicle. ATP-dependent proton pumps lower the pH inside the vesicle resulting dissociation of LDL from its receptor. After loss of the clathrin coat the vesicles fuse with lysozomes, resulting in peptide and cholesteryl ester enzymatic hydrolysis. The LDL receptor can be recycled to the cell membrane. Insulin, tri-iodothyronine and dexamethasome have shown to be involved with the regulation of LDL receptor mediated uptake.
