title: Alkaline hemolysis fragility is dependent on cell shape: results from a morphology tracker.
abstract: BACKGROUND
  The morphometric analysis of red blood cells (RBCs) is an important area of study and has been performed previously for fixed samples. We present a novel method for the analysis of morphologic changes of live erythrocytes as a function of time. We use this method to extract information on alkaline hemolysis fragility. Many other toxins lyse cells by membrane poration, which has been studied by averaging over cell populations. However, no quantitative data are available for changes in the morphology of individual cells during membrane poration-driven hemolysis or for the relation between cell shape and fragility.
  
  
  METHODS
  Hydroxide, a porating agent, was generated in a microfluidic enclosure containing RBCs in suspension. Automatic cell recognition, tracking, and morphometric measurements were done by using a custom image analysis program. Cell area and circular shape factor (CSF) were measured over time for individual cells. Implementations were developed in MATLAB and on Kestrel, a parallel computer that affords higher speed that approaches real-time processing.
  
  
  RESULTS
  The average CSF went through a first period of fast increase, corresponding to the conversion of discocytes to spherocytes under internal osmotic pressure, followed by another period of slow increase until the fast lysis event. For individual cells, the initial CSF was shown to be inversely correlated to cell lifetime (linear regression factor R=0.44), with discocytes surviving longer than spherocytes. The inflated cell surface area to volume ratio was also inversely correlated to lifetime (R=0.43) but not correlated to the CSF. Lifetime correlated best to the ratio of cell inflation volume (Vfinal-Vinitial) to surface area (R=0.65).
  
  
  CONCLUSIONS
  RBCs inflate at a rate proportional to their surface area, in agreement with a constant flux model, and lyse after attaining a spherical morphology. Spherical RBCs display increased alkaline hemolysis fragility (shorter lifetimes), providing an explanation for the increased osmotic fragility of RBCs from patients who have spherocytosis.
authors.affiliation: Bioengineering Department, University of California at Berkeley, Berkeley, California 94720, USA.
authors.forename: Cristian
authors.initials: C
authors.lastname: Ionescu-Zanetti
authors.forename: Lee-Ping
authors.initials: LP
authors.lastname: Wang
authors.forename: Dino
authors.initials: D
authors.lastname: Di Carlo
authors.forename: Paul
authors.initials: P
authors.lastname: Hung
authors.forename: Andrea
authors.initials: A
authors.lastname: Di Blas
authors.forename: Richard
authors.initials: R
authors.lastname: Hughey
authors.forename: Luke P
authors.initials: LP
authors.lastname: Lee
mesh_terms: D048430:Cell Shape; D048429:Cell Size; D003201:Computers; D004907:Erythrocyte Deformability; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000166:cytology* / Q000378:metabolism; D006461:Hemolysis; D006801:Humans; D006878:Hydroxides / Q000378:metabolism; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D009996:Osmotic Fragility; D012984:Software; D013102:Spherocytes / Q000166:cytology; D013997:Time Factors
chemical_list: D006878:Hydroxides