title: Impact of Oxygen Levels on Human Hematopoietic Stem and Progenitor Cell Expansion.
abstract: Oxygen levels are an important variable during the in vitro culture of stem cells. There has been increasing interest in the use of low oxygen to maximize proliferation and, in some cases, effect differentiation of stem cell populations. It is generally assumed that the defined pO2in the incubator reflects the pO2to which the stem cells are being exposed. However, we demonstrate that the pO2experienced by cells in static culture can change dramatically during the course of culture as cell numbers increase and as the oxygen utilization by cells exceeds the diffusion of oxygen through the media. Dynamic culture (whereby the cell culture plate is in constant motion) largely eliminates this effect, and a combination of low ambient oxygen and dynamic culture results in a fourfold increase in reconstituting capacity of human hematopoietic stem cells compared with those cultured in static culture at ambient oxygen tension. Cells cultured dynamically at 5% oxygen exhibited the best expansion: 30-fold increase by flow cytometry, 120-fold increase by colony assay, and 11% of human CD45 engraftment in the bone marrow of NOD/SCID mice. To our knowledge, this is the first study to compare individual and combined effects of oxygen and static or dynamic culture on hematopoietic ex vivo expansion. Understanding and controlling the effective oxygen tension experienced by cells may be important in clinical stem cell expansion systems, and these results may have relevance to the interpretation of low oxygen culture studies.
authors.affiliation: 1 The Ritchie Centre, Hudson Institute of Medical Research , Clayton, Australia .
authors.forename: Abhilasha
authors.initials: A
authors.lastname: Tiwari
authors.affiliation: 2 Deakin University , Geelong, Australia .
authors.forename: Cynthia S
authors.initials: CS
authors.lastname: Wong
authors.affiliation: 1 The Ritchie Centre, Hudson Institute of Medical Research , Clayton, Australia .
authors.forename: Lakshmi P
authors.initials: LP
authors.lastname: Nekkanti
authors.affiliation: 1 The Ritchie Centre, Hudson Institute of Medical Research , Clayton, Australia .|3 Department of Obstetrics and Gynaecology, Southern Clinical School, Monash University , Clayton, Australia .
authors.forename: James A
authors.initials: JA
authors.lastname: Deane
authors.affiliation: 1 The Ritchie Centre, Hudson Institute of Medical Research , Clayton, Australia .
authors.forename: Courtney
authors.initials: C
authors.lastname: McDonald
authors.affiliation: 1 The Ritchie Centre, Hudson Institute of Medical Research , Clayton, Australia .|3 Department of Obstetrics and Gynaecology, Southern Clinical School, Monash University , Clayton, Australia .
authors.forename: Graham
authors.initials: G
authors.lastname: Jenkin
authors.affiliation: 2 Deakin University , Geelong, Australia .
authors.forename: Mark A
authors.initials: MA
authors.lastname: Kirkland