PB0358 - In-depth analysis of the effects of unsteady flows on platelet release from suspensions of proplatelet-bearing megakaryocytes

Background: Recent research in the field of platelet production has shown that unsteady flow behaviour favours the efficient generation of platelets from their precursors, the megakaryocytes (MK). We obtained yields of ~100 platelets/MK in a custom device presenting a succession of convergent-divergent geometries in which continuous periodic flow conditions are generated. However, these yields still do not reach those obtained in vivo (≈1000-2000). Therefore, a better understanding of the mechanisms of platelet release from suspended MK should allow to promote the development of even more efficient systems.

Aims: The present study proposes to analyse spatio-temporal influence between hydrodynamics and proplatelet-bearing MK processed into our platelet release dev ice in order to identify parameters that influence platelet yield

Methods: Flow conditions in the device were determined by computational fluid dynamics (CFD) simulations for various flow rates. Trajectories of small 1-10µm spherical inert particles dragged into the flow, mimicking either platelets or MK, were inferred from these simulations. Particle histories data through the device were statistically analysed.

Results: We showed that, regardless of diameter, the particles underwent a complex history marked by alternating laminar and turbulent flow conditions. Turbulent regions at high Reynolds numbers (~2700) were observed downstream of the narrowest sections of the geometry where short applications of stresses have occurred. These short stresses, which dominate the hydrodynamic loading of the particles, were found to be essential for efficient platelet release. However, if the flow rate increased, the stresses on the particles increased but the residence time decreased resulting in a decreased platelet release. Detailed analysis of these opposing trends has identified the importance not of stress alone, but of “shear stress accumulation” in combination with turbulence as key elements of the mechanisms underlying platelet release.

Conclusion(s): This study opens new directions for the development of efficient large scale platelet release devices.