title: Enhanced shear-induced platelet aggregation due to low-temperature storage.
abstract: BACKGROUND
  Refrigeration of platelets (PLTs) offers an attractive alternative to the currently practiced storage at room temperature since it may mitigate problems associated with bacterial contamination and extend storage lifetime. Refrigeration causes a number of biophysical and biochemical changes in PLTs and decreases PLT circulation time in vivo. However, the effect of refrigeration on PLT hemostatic functions under physiologic and pathophysiologic shear conditions has not been adequately characterized.
  
  
  METHODS
  Washed PLTs prepared from either fresh PLT-rich plasma (PRP) or PRP stored at 4°C for 2 days was mixed with exogenous von Willebrand factor (VWF) and fibrinogen and sheared in a cone-and-plate viscometer. PLT aggregation, activation, and VWF binding after shear and glycoprotein (GP) Ibα receptor expression and ristocetin-induced PLT agglutination were measured.
  
  
  RESULTS
  PLTs stored at 4°C for 2 days aggregated significantly more than fresh PLTs particularly at high shear rates (10,000/sec), and this increase was independent of PLT concentration or suspension viscosity. Further, refrigerated PLTs showed a greater increase in GP Ibα-dependent PLT activation under shear and also bound more VWF than fresh PLTs. However, the GP Ibα expression levels as measured by three different antibodies were significantly lower in refrigerated PLTs than in fresh PLTs, and refrigeration resulted in a modest decrease in ristocetin-induced PLT agglutination.
  
  
  CONCLUSIONS
  The combined results demonstrate that refrigeration increases PLT aggregation under high shear, but not static, conditions and also increases shear-induced VWF binding and PLT activation. Clinically, enhanced shear-induced PLT aggregation due to low temperature storage may be a beneficial strategy to prevent severe bleeding in trauma.
authors.affiliation: Department of Biomedical Engineering and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, Texas 78249, USA.
authors.forename: Robbie K
authors.initials: RK
authors.lastname: Montgomery
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Reddoch
authors.forename: Shankar J
authors.initials: SJ
authors.lastname: Evani
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Cap
authors.forename: Anand K
authors.initials: AK
authors.lastname: Ramasubramanian
mesh_terms: D001792:Blood Platelets / Q000378:metabolism; D001793:Blood Preservation; D006801:Humans; D008562:Membrane Glycoproteins / Q000097:blood; D010974:Platelet Aggregation; D019038:Platelet Glycoprotein GPIb-IX Complex; D012034:Refrigeration; D012310:Ristocetin / Q000494:pharmacology; D013314:Stress, Mechanical; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D008562:Membrane Glycoproteins; D019038:Platelet Glycoprotein GPIb-IX Complex; C094990:adhesion receptor; D014841:von Willebrand Factor; D012310:Ristocetin