Red blood cell membrane water permeability increases with length of ex vivo storage

Effect of microaggregate filter passage on feline whole blood stored for 35 days

OBJECTIVES

The aim of this study was to compare the characteristics of fresh and stored feline red blood cells (RBCs) after passage through an 18 μm microaggregate filter.

METHODS

Nine cats were recruited for a single blood donation using an open collection system. A simulated transfusion using a syringe driver and microaggregate filter was performed over 2 h with half the blood on the day of donation and the other half after 35 days of storage. Differences in haematological parameters, haemolysis percentage and osmotic fragility (OF) were compared on the day of donation pre-filter passage (D0-) vs day of donation post-filter (D0+) or day 35 storage pre-filter (D35-) and post-filter (D35+). Blood was cultured at D0+ and D35+.

RESULTS

There were no statistically significant differences in the D0- vs D0+ comparisons. There were statistically significant (P <0.05) increases in haemolysis percentage, red cell distribution width (RDW) percentage and mean OF, and decreases in packed cell volume (PCV), RBC count, haemoglobin and haematocrit for D0- vs D35-. The same was found for D0- vs D35+ with the addition of a significant increase in mean cell haemoglobin (MCH). For D35- vs D35+ only MCH significantly increased. At day 35, 6/9 units had haemolysis percentages that exceeded 1%. This increased to 8/9 of stored units post-filter passage. All blood units cultured negative.

CONCLUSIONS AND RELEVANCE

Fresh RBCs exhibited no in vitro evidence of injury following passage through an 18 μm microaggregate filter. Increased MCH was observed in the stored blood and may represent haemolysis induced by the filter. All other changes can be explained by storage lesion rather than filter passage. The findings highlight the importance of blood banking quality controls and the need for further research to assess the effects of transfusion technique, specifically filter passage, on storage lesion-affected feline blood.

Microfluidic measurement of individual cell membrane water permeability

This paper reports a microfluidic lab-on-chip for dynamic particle sizing and real time individual cell membrane permeability measurements. To achieve this, the device measures the impedance change of individual cells or particles at up to ten time points after mixing with different media, e.g. dimethyl sulfoxide or DI water, from separate inlets. These measurements are enabled by ten gold electrode pairs spread across a 20 mm long microchannel. The device measures impedance values within 0.26 s after mixing with other media, has a detection throughput of 150 samples/second, measures impedance values at all ten electrodes at this rate, and allows tracking of individual cell volume changes caused by cell osmosis in anisosmotic fluids over a 1.3 s postmixing timespan, facilitating accurate individual cell estimates of water permeability. The design and testing were performed using yeast cells (Saccharomyces cerevisiae). The relationship between volume and impedance in both polystyrene calibration beads as well as the volume-osmolality relationship in yeast were demonstrated. Moreover, we present the first noninvasive and non-optically-based water permeability measurements in individual cells.

Assessment of transient changes in oxygen diffusion of single red blood cells using a microfluidic analytical platform

Red blood cells (RBCs) capability to deliver oxygen (O₂) has been routinely measured by P50. Although this defines the ability of RBCs to carry O₂ under equilibrium states, it cannot determine the efficacy of O₂ delivery in dynamic blood flow. Here, we developed a microfluidic analytical platform (MAP) that isolates single RBCs for assessing transient changes in their O₂ release rate. We found that in vivo (biological) and in vitro (blood storage) aging of RBC could lead to an increase in the O₂ release rate, despite a decrease in P50. Rejuvenation of stored RBCs (Day 42), though increased the P50, failed to restore the O₂ release rate to basal level (Day 0). The temporal dimension provided at the single-cell level by MAP could shed new insights into the dynamics of O₂ delivery in both physiological and pathological conditions.

Implications of variability in cell membrane permeability for design of methods to remove glycerol from frozen-thawed erythrocytes

In North America, red blood cells (RBCs) are currently cryopreserved in a solution of 40% glycerol. While glycerol is not inherently toxic to humans, it must be removed prior to transfusion to prevent intravascular osmotic hemolysis. The current deglycerolization procedure requires about 45 min per RBC unit. We previously presented predictions suggesting that glycerol could be safely removed from RBCs in less than 1 min. However, experimental evaluation of these methods resulted in much higher hemolysis than expected. Here we extend our previous study by considering both concentration-dependence of permeability and variability in permeability values in the mathematical optimization algorithm. To establish a model for the concentration dependence of glycerol permeability, we combined literature data with new measurements of permeability in the presence of 40% glycerol. To account for cell-dependent variability we scaled the concentration-dependent permeability model to define a permeability range for optimization. Methods designed using a range extending to 50% of the model-predicted glycerol permeability had a duration of less than 3 min and resulted in hemolysis ranging from 34% to 83%; hemolysis values were highly dependent on the blood donor. Extending the permeability range to 5% of the model-predicted value yielded a 30 min method that resulted in an average hemolysis of 12%. Our results suggest high variability in the glycerol permeability between donors and within a population of cells from the same donor. Such variability has broad implications for design of methods for equilibration of cells with cryoprotectants.

Factors Affecting the Membrane Permeability Barrier Function of Cells during Preservation Technologies

Cellular membranes are exposed to extreme conditions during the processing steps involved in cryopreservation (and freeze-drying) of cells. The first processing step involves adding protective agents. Exposing cells to protective agents causes fluxes of both water and solutes (i.e., permeating cryoprotective agents) across the cellular membrane, resulting in cell volume changes and possibly osmotic stress. In addition, protective molecules may interact with lipids, which may lead to membrane structural changes and permeabilization. After loading with protective agents, subsequent freezing exposes cells to severe osmotic and mechanical stresses, caused by extra and/or intracellular ice formation and a drastically increased solute concentration in the unfrozen fraction. Furthermore, cellular membranes undergo thermotropic and lyotropic phase transitions during cooling and freezing, which drastically alter the membrane permeability and its barrier function. In this article, it is shown that membrane permeability to water and solutes is dependent on the temperature, medium osmolality, types of solutes present, cell hydration level, and absence or presence of ice. Freezing most drastically alters the membrane permeability barrier function, which is reflected as a change in the activation energy for water transport. In addition, membranes become temporarily leaky during freezing-induced fluid-to-gel membrane phase transitions, resulting in the uptake of impermeable solutes.

Extending the pre-processing holding time of whole blood beyond 48 h reduces coagulation FVIII activity and immunoglobulin G content of recovered plasma

BACKGROUND

Plasma obtained via whole blood (WB) donation may be used either for transfusion or as recovered plasma (RP) for pooling and fractionation. In Canada, transfusable plasma must be processed within 24 h of phlebotomy, while the limit for RP processing is 72 h. We assessed the quality of RP produced by two WB processing methods and as a function of processing time.

STUDY DESIGN AND METHODS

RP units produced via the buffy coat method (BCM, n = 26) or whole blood filtration (WBF, n = 52) were tested for: the activities of prothrombin, fibrinogen, von Willebrand Factor (VWF), FV, FVII, and FVIII; the prothrombin time (PT); and total protein and IgG concentration. WBF RP units were evenly divided between those processed <48 h of phlebotomy (shorter-processed) or 48-72 h after phlebotomy (longer-processed).

RESULTS

WBF-RP did not differ significantly from BCM-RP in any tested parameter except for FV and FVIII, which exhibited mean reductions of 10.2% and 20%, respectively. Longer-processed WBF-RP did not differ significantly from shorter-processed WBF-RP in any tested parameter except for FVIII activity and IgG concentration, which exhibited mean reductions of 30.1% and 14.3%, respectively.

CONCLUSIONS

Canadian RP is currently fractionated into IgG, albumin, fibrinogen, and FVII/VWF concentrates irrespective of its method or time of processing. Our results supported the current approach of fractionating both BCM- and WBF-derived RP, but suggest that greater yields of immunoglobulin and FVIII/VWF products could be obtained if the maximum processing time was reduced from 72 h to 48 h.

Mechanisms of red blood cell transfusion-related immunomodulation

Red blood cell (RBC) transfusion is common in critically ill, postsurgical, and posttrauma patients in whom both systemic inflammation and immune suppression are associated with adverse outcomes. RBC products contain a multitude of immunomodulatory mediators that interact with and alter immune cell function. These interactions can lead to both proinflammatory and immunosuppressive effects. Defining clinical outcomes related to immunomodulatory effects of RBCs in transfused patients remains a challenge, likely due to complex interactions between individual blood product characteristics and patient-specific risk factors. Unpacking these complexities requires an in-depth understanding of the mechanisms of immunomodulatory effects of RBC products. In this review, we outline and classify potential mediators of RBC transfusion-related immunomodulation and provide suggestions for future research directions.