EBioMedicine (Jan 2025)

Assessing the kinetics of oxygen-unloading from red cells using FlowScore, a flow-cytometric proxy of the functional quality of bloodResearch in context

  • Julija Rabcuka,
  • Peter A. Smethurst,
  • Katharina Dammert,
  • Jarob Saker,
  • Gemma Aran,
  • Geraldine M. Walsh,
  • Joanne C.G. Tan,
  • Margarita Codinach,
  • Ken McTaggart,
  • Denese C. Marks,
  • Stephan J.L. Bakker,
  • Amy McMahon,
  • Emanuele Di Angelantonio,
  • David J. Roberts,
  • Slawomir Blonski,
  • Piotr M. Korczyk,
  • Atsushi Shirakami,
  • Rebecca Cardigan,
  • Pawel Swietach

Journal volume & issue
Vol. 111
p. 105498

Abstract

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Summary: Background: Metrics evaluating the functional quality of red blood cells (RBCs) must consider their role in oxygen delivery. Whereas oxygen-carrying capacity is routinely reported using haemoglobin assays, the rate of oxygen exchange is not measured, yet also important for tissue oxygenation. Since oxygen-unloading depends on the diffusion pathlength inside RBCs, cell geometry offers a plausible surrogate. Methods: We related the time-constant of oxygen-unloading (τ), measured using single-cell oxygen saturation imaging, with flow-cytometric variables recorded on a haematology analyser. Experiments compared freshly-drawn RBCs with stored RBCs, wherein metabolic run-down and spherical remodelling hinder oxygen unloading. Findings: Multivariable regression related τ to a ratio of side- and forward-scatter, referred to herein as FlowScore. FlowScore was able to distinguish, with sensitivity and specificity >80%, freshly drawn blood from blood that underwent storage-related kinetic attrition in O2-handling. Moreover, FlowScore predicted τ restoration upon biochemical rejuvenation of stored blood. Since RBC geometry and metabolic state are related, variants of FlowScore estimated [ATP] and [2,3-diphosphoglycerate]. The veracity of FlowScore was confirmed by four blood-banking systems (Australia, Canada, England, Spain). Applying FlowScore to data from the COMPARE study revealed a positive association with the time-delay from sample collection to measurement, which was verified experimentally. The LifeLines dataset revealed age, sex, and smoking among factors affecting FlowScore. Interpretation: We establish FlowScore as a widely-accessible and cost-effective surrogate of RBC oxygen-unloading kinetics. As a metric of a cellular process that is sensitive to storage and disease, we propose FlowScore as an RBC quality marker for blood-banking and haematology. Funding: See Acknowledgements.

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