New plasma and platelet products : evaluation of hemostatic and functional properties in experimental studies

<p dir="ltr">Blood transfusion plays a vital role in managing major bleeding, preventing mortality, and maintaining hemodynamic stability. Strong evidence indicates that early transfusion significantly improves survival rates. However, access to blood can be challenging in remote hospitals with constrained inventories, during mass casualty events, at the site of injury, or in military operations where proper storage conditions are lacking. Developing new strategies to overcome these challenges is essential to meet transfusion needs. One such strategy involves alternative methods for storing blood components, which can help improve the availability and resilience of the blood supply. Cryopreserved platelets, for example, can be stored frozen for several years, unlike conventional platelets which have a limited shelf life of 5-7 days and are often in short supply. They are intended for use in patients with active bleeding, as they exhibit a pro-coagulant phenotype. Another promising component is dried plasma, which has gained increased attention in the context of emergency preparedness. Although traditionally restricted to military settings, dried plasma is now becoming more widely available, thereby expanding its use in both pre-hospital and in-hospital care. Dried plasma offers logistical advantages, as it does not require a cold chain and remains stable for at least two years at room temperature. With the introduction of new blood components into clinical practice, studies are needed to evaluate not only their individual quality but also their combined hemostatic effects. To address these challenges, this thesis evaluated the hemostatic and functional properties of cryopreserved platelets and dried plasma through a series of experimental studies.</p><p dir="ltr">In <b>Paper I</b>, we investigated the interplay between platelets and plasma components. Various combinations were tested, including conventional platelets with either fresh frozen plasma or pathogen-inactivated plasma, and cryopreserved platelets with the same two plasma types. Additionally, the quality of each plasma and platelet type was assessed individually. The study revealed that both pathogen-inactivated plasma and cryopreserved platelets demonstrated altered characteristics relative to their respective counterparts. However, only the groups containing cryopreserved platelets showed reduced clot strength in ROTEM, suggesting that platelet quality, rather than differences in coagulation factor levels, plays a more significant role in in vitro clot formation.</p><p dir="ltr">In <b>Paper II</b>, we explored the possibility of cryopreserving platelets without using the toxic cryoprotectant DMSO, which is the current standard. Interestingly, DMSO-free freezing resulted in a higher platelet count, although the platelets showed slightly more damage compared to those preserved with DMSO. We further tested controlled-rate freezing, which improved the viability of platelets frozen in the absence of DMSO. These findings suggest that DMSO-free cryopreservation, particularly when combined with controlled-rate freezing, may be a promising alternative that avoids the risk of toxicity.</p><p dir="ltr">In <b>Paper III</b>, we shifted focus to plasma, comparing three differently produced dried plasma products with fresh frozen plasma of respective origin, as controls. The comparison included user evaluations by healthcare professionals from various fields, as well as laboratory tests assessing coagulation factor content and hemostatic function. All dried plasma units could be reconstituted within 10 minutes, with even faster times among experienced users. An advantage deemed important was the ability to deliver the final product in a plastic bag, facilitating transfusion under pressure. Laboratory testing revealed some variation in coagulation factor levels among the plasma types, although all remained within reference ranges. No impairment in clot formation through TEG was observed. Overall, the dried plasma products were feasible for use and supported hemostasis in vitro, highlighting their potential role in emergency preparedness.</p><p dir="ltr">In <b>Study IV</b>, we assessed the use of dried plasma as a reconstitution medium for cryopreserved platelets, in comparison to regular fresh frozen plasma. The study found that dried plasma was comparable to fresh frozen plasma in this application. Interestingly, platelet concentrations were higher when dried plasma was used. However, phenotypic and functional testing of the final component revealed no significant differences between the two groups. Dried plasma thus appears to be a promising alternative reconstitution medium, particularly due to its fast preparation time and logistical advantages, including room temperature storage. These benefits make it especially suitable for emergency preparedness, including use in remote hospitals, prehospital care settings, and military operations.</p><p dir="ltr">In summary, this thesis provides valuable insights into the evaluation of alternative platelet and plasma components that can improve transfusion logistics and availability in resource-limited settings. It also highlights the potential implications of combining these components during transfusions, an important consideration for clinical practice. Overall, this research supports efforts to make blood components more accessible in emergencies where transfusions are crucial, yet access is often limited.</p><h3>List of scientific papers</h3><p dir="ltr">I. Sandgren P, <b>Ehn K,</b> Larsson L, Uhlin M, Wikman A. Cryopreserved platelets and amotosalen-treated plasma in an experimental clot formation set-up. Blood Transfus. 2023;21(2):137-145. <a href="https://doi.org/10.2450/2022.0279-21" target="_blank">https://doi.org/10.2450/2022.0279-21</a></p><p dir="ltr">II. <b>Ehn K,</b> Wikman A, Uhlin M, Sandgren P. Cryopreserved Platelets in a Non-Toxic DMSO-Free Solution Maintain Hemostatic Function In Vitro. Int J Mol Sci. 2023;24(17):13097. <a href="https://doi.org/10.3390/ijms241713097" target="_blank">https://doi.org/10.3390/ijms241713097</a></p><p dir="ltr">III. <b>Ehn K,</b> Skallsjö G, Romlin B, Sandström G, Sandgren P, Wikman A. An experimental comparison and user evaluation of three different dried plasma products. Vox Sang. Published online 2025 Jan 27. <a href="https://doi.org/10.1111/vox.13798" target="_blank">https://doi.org/10.1111/vox.13798</a></p><p dir="ltr">IV. <b>Ehn K,</b> Sandgren P, Asplund Högelin K, Wikman A. Improved Platelet Recovery in Cryopreserved Platelets Reconstituted in Freeze-Dried Plasma. Submitted for publication, 2025-09-10. [Manuscript]</p>