title: Cell density-dependent proliferation in frequently-fed peripheral blood mononuclear cell cultures.
abstract: BACKGROUND
  Our goal was to produce granulocyte progenitor (CFU-G) and post-progenitor (CD15(+)CD11b(+/-)) cells for subsequent transplantation. We hypothesized that increasing the feeding frequency and maintaining constant densities may overcome inhibitory growth conditions (i.e. low pH) in high-density cultures.
  
  
  METHODS
  To study the effect of cell density on total cell expansion, differentiation and lactate production, 50% daily medium exchanges were used in cultures of peripheral blood mononuclear cells (PB MNC) maintained at constant densities (ranging from 5 x 10(4)cells/mL to 2.5 x 10(6)cells/mL).
  
  
  RESULTS
  We observed a significant increase in total cell expansion when the density was increased from 5 x 10(4) cells/mL to 1 x 10(6) cells/mL, but a further increase to 2.5 x 10(6)cells/mL resulted in a decline in cell expansion. Increasing feeding to 90% daily exchange in cultures with 2.5 x 10(6) cells/mL did not enhance cell expansion; nor did reducing the extent of feeding in cultures with 5 x 10(4) cells/mL to 10% daily exchange. We did not observe a relationship between cell density and the percentage of granulocyte progenitor and post-progenitor (CD15(+)CD11b(-/+)) cells. While specific lactate production (q(lac)) in cultures with 2.5 x 10(6) cells/mL was approximately 60% of those observed in lower density cultures by Day 13, this difference was largely eliminated by increasing the extent of feeding in cultures with 2.5 x 10(6) cells/mL.
  
  
  CONCLUSIONS
  Our results suggest that feeding rates must be adjusted according to cell density to maximize culture performance. They also suggest that cellular crowding on the culture surface can limit expansion in suspension (nonadherent) cultures.
authors.affiliation: Department of Chemical Engineering, Northwestern University, Evanston, IL 60208, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Patel
authors.forename: W M
authors.initials: WM
authors.lastname: Miller
authors.forename: J N
authors.initials: JN
authors.lastname: Winter
authors.forename: E T
authors.initials: ET
authors.lastname: Papoutsakis
mesh_terms: D002452:Cell Count; D018929:Cell Culture Techniques / Q000379:methods*; D002454:Cell Differentiation; D002455:Cell Division; D005434:Flow Cytometry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000096:biosynthesis; D007963:Leukocytes, Mononuclear / Q000166:cytology* / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism
chemical_list: D019344:Lactic Acid