title: Polyplex-mediated gene transfer and cell cycle: effect of carrier on cellular uptake and intracellular kinetics, and significance of glycosaminoglycans.
abstract: BACKGROUND
  Here we report on studies that probe whether the intracellular kinetics of plasmid DNA (pDNA) and cell surface glycosaminoglycans (GAGs) are modified during the cell cycle in a way that can be correlated with changes in gene transfer efficiency with poly(ethyleneimine) (PEI) and poly-L-lysine (PLL) polyplexes.
  
  
  METHODS
  Synchronized D407 retinal cells were transfected with PEI and PLL polyplexes using a luciferase reporter. The free and/or loosely complexed nuclear pDNA was determined by real-time PCR, and compared with transgene expression, the rate of pinocytosis by FITC-dextran uptake and the content of cell surface GAGs.
  
  
  RESULTS
  The amount of free and/or loosely complexed nuclear pDNA between cell cycle phases varied approximately 4-20 times (G1 < S < G2/M). Both carriers delivered pDNA in a similar way into the nucleus (PLL vs. PEI < or = 3.5-fold), but PEI was approximately 10-100 times more efficient in gene expression than PLL (G1 < G2/M < S). The rate of pinocytosis increased up to 70-fold from G1 to middle S phase. Cell surface heparan and chondroitin sulfate increased 50-80%, and hyaluronan decreased 50% when the cells went from G1 through S to G2/M.
  
  
  CONCLUSIONS
  The data obtained indicates that no single parameter (pinocytosis, cell surface GAGs, nuclear uptake) solely accounts for the differential pDNA uptake or expression during cell cycle, and that the main difference in PLL- and PEI-mediated transfections seems to be at the nuclear level.
authors.affiliation: Department of Pharmaceutics, University of Kuopio, Kuopio, Finland. marjo.mannisto@helsinki.fi
authors.forename: Marjo
authors.initials: M
authors.lastname: Männistö
authors.forename: Mika
authors.initials: M
authors.lastname: Reinisalo
authors.forename: Marika
authors.initials: M
authors.lastname: Ruponen
authors.forename: Paavo
authors.initials: P
authors.lastname: Honkakoski
authors.forename: Markku
authors.initials: M
authors.lastname: Tammi
authors.forename: Arto
authors.initials: A
authors.lastname: Urtti
mesh_terms: D002453:Cell Cycle / Q000187:drug effects*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D016650:Fluorescein-5-isothiocyanate; D006025:Glycosaminoglycans / Q000378:metabolism*; D007700:Kinetics; D010873:Pinocytosis / Q000187:drug effects; D010957:Plasmids / Q000378:metabolism; D011094:Polyethyleneimine / Q000494:pharmacology*; D011107:Polylysine / Q000494:pharmacology*; D014162:Transfection / Q000379:methods*
chemical_list: D006025:Glycosaminoglycans; D011107:Polylysine; D011094:Polyethyleneimine; D004247:DNA; D016650:Fluorescein-5-isothiocyanate