title: Single-cell measurement of red blood cell oxygen affinity.
abstract: Oxygen is transported throughout the body by hemoglobin (Hb) in red blood cells (RBCs). Although the oxygen affinity of blood is well-understood and routinely assessed in patients by pulse oximetry, variability at the single-cell level has not been previously measured. In contrast, single-cell measurements of RBC volume and Hb concentration are taken millions of times per day by clinical hematology analyzers, and they are important factors in determining the health of the hematologic system. To better understand the variability and determinants of oxygen affinity on a cellular level, we have developed a system that quantifies the oxygen saturation, cell volume, and Hb concentration for individual RBCs in high throughput. We find that the variability in single-cell saturation peaks at an oxygen partial pressure of 2.9%, which corresponds to the maximum slope of the oxygen-Hb dissociation curve. In addition, single-cell oxygen affinity is positively correlated with Hb concentration but independent of osmolarity, which suggests variation in the Hb to 2,3-diphosphoglycerate (2-3 DPG) ratio on a cellular level. By quantifying the functional behavior of a cellular population, our system adds a dimension to blood cell analysis and other measurements of single-cell variability.
authors.affiliation: The Rowland Institute, Harvard University, Cambridge, MA 02142; dicaprio@rowland.harvard.edu.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Di Caprio
authors.affiliation: The Rowland Institute, Harvard University, Cambridge, MA 02142;
authors.forename: Chris
authors.initials: C
authors.lastname: Stokes
authors.affiliation: Center for Systems Biology, Massachusetts General Hospital, Boston, MA 02115; Department of Systems Biology, Harvard Medical School, Boston, MA 02115.
authors.forename: John M
authors.initials: JM
authors.lastname: Higgins
authors.affiliation: The Rowland Institute, Harvard University, Cambridge, MA 02142;
authors.forename: Ethan
authors.initials: E
authors.lastname: Schonbrun
mesh_terms: D004912:Erythrocytes / Q000378:metabolism*; D005434:Flow Cytometry; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D010100:Oxygen / Q000097:blood*; D059010:Single-Cell Analysis / Q000295:instrumentation / Q000379:methods*; D013057:Spectrum Analysis
chemical_list: D006454:Hemoglobins; D010100:Oxygen
keywords: flow cytometry; hematology; medical sciences; organ on chip; single-cell variability