Takafumi Kimura

Objectives: We aimed to investigate the quality of platelets after storage following irradiation with ultraviolet C (UVC) light‐emitting diodes (LED). Background: Controlling transfusion‐related infections, particularly bacterial contamination of platelet concentrates (PCs), is urgently required. UVC‐LEDs have attracted considerable attention as potential solutions to this problem. Methods: PCs (5.5 mL) were irradiated with 265 nm UVC‐LED for up to 60 min and then stored at 22°C with shaking for 3 days. PC quality parameters, such as platelet count, biochemical profiles, including electrolytes and metabolism, activation markers and platelet aggregability, were analysed before and after storage. Prior to the storage study, to validate the appropriateness of the UVC‐LED dose used, the PCs were inoculated with Staphylococcus aureus or Bacillus cereus , and their colony‐forming ability was evaluated after irradiation with the same dose of UVC‐LED. Results: We confirmed that S. aureus and B. cereus colonies decreased with the irradiation dose (by 1.7 log and 1.2 log at 38.7 and 40.4 mJ cm ⁻² , respectively). Platelet count decreased immediately after 60‐minute irradiation to 32.5 mJ cm ⁻² , reaching approximately 80% of the level in the control without irradiation, but no further decrease was recorded after storage. The biochemical profiles and activation markers showed little alterations. Conclusion: These results indicate that UVC‐irradiated platelets maintain sufficient quality for practical use even after storage. Although this was a bench‐scale study, our findings suggest that irradiation of PCs with 265 nm UVC‐LED may enhance the safety of blood transfusions while preserving their efficacy.

The efficacy of hematopoietic stem cell (HSC) therapy for cerebral infarction has been previously demonstrated. However, the lack of response in some patients has hindered its widespread use. To establish HSC therapy as a standard treatment, it is important to examine the causes of non-responsiveness. In this study, we aimed to identify the specifications of transplanted cells based on their therapeutic mechanisms to predict treatment success. We found that HSC therapy activates injured cerebral endothelial cells via gap junctions because cell adhesion between HSCs and the endothelium plays an essential role in cellular communication via gap junctions. The expression of the adhesion molecule integrin β2 (CD18) in CD34-positive (CD34⁺) cells was identified as critical for the therapeutic effect on cerebral infarction in a murine model. Cells with low CD18 expression exhibited a weaker therapeutic effect than cells with high CD18 expression, even when the same number of HSCs was administered. The expression of CD18 in CD34⁺ cells can be used as a specification marker for transplanted HSCs and is useful for identifying non-responders. Furthermore, quantification of CD18 expression is crucial for evaluating the cellular potential of cell-based therapies for diseases where therapeutic effects are mediated through cell adhesion.

Although regenerative therapy with stem cells is believed to be affected by their proliferation and differentiation potential, there is insufficient evidence regarding the molecular and cellular mechanisms underlying this regenerative effect. We recently found that gap junction-mediated cell–cell transfer of small metabolites occurred very rapidly after stem cell treatment in a mouse model of experimental stroke. This study aimed to investigate whether the tissue repair ability of umbilical cord blood cells is affected by X-irradiation at 15 Gy or more, which suppresses their proliferative ability. In this study, X-irradiated mononuclear (XR) cells were prepared from umbilical cord blood. Even though hematopoietic stem/progenitor cell activity was diminished in the XR cells, the regenerative activity was surprisingly conserved and promoted recovery from experimental stroke in mice. Thus, our study provides evidence regarding the possible therapeutic mechanism by which damaged cerebrovascular endothelial cells or perivascular astrocytes may be rescued by low-molecular-weight metabolites supplied by injected XR cells in 10 min as energy sources, resulting in improved blood flow and neurogenesis in the infarction area. Thus, XR cells may exert their tissue repair capabilities by triggering neo-neuro-angiogenesis, rather than via cell-autonomous effects.

Background: Washed platelet concentrates (WPC), prepared with an automated system cell processor (ACP), have recently been approved to be manufactured and marketed in Japan. From the perspective of risk management, it is preferable to secure alternative technologies for ACP. Here, we conducted a study to evaluate the quality of WPC prepared using an automated membrane filtration‐based system, Lovo.Study design and methods: Replaced PCs prepared from apheresis PCs were equally divided into control and test units, and subsequently washed using ACP and Lovo respectively. Work and operational efficiencies were evaluated by in vitro analyses, including total handling time, platelet recovery, and plasma protein removal rate. Product quality, including a set of biochemical and physiological indicators of platelets and supernatants, were assessed before and 3 days after washing.Results: In vitro platelet recovery rates and plasma protein removal rates were >85% and >95%, respectively, in both groups. The pH values on day 0 were significantly high (6.97 vs. 6.86) due to low pCO₂ in the test group, while no significant differences in glucose consumption and lactate production were observed between the two groups. The levels of hypotonic shock responses, aggregation response, platelet shape, CD62P expression, and sCD62P concentration were similar in both groups during the 3‐day storage period.Conclusion: Platelet washing with Lovo provides platelet quality equivalent to, or better than, conventional washing with ACP. Thus, the new automated system, Lovo, can be considered as an alternative to ACP for WPC preparation.