Agitation-dependent biomechanical forces modulate GPVI receptor expression and platelet adhesion capacity during storage

BACKGROUND

Continuous agitation during storage slows down the platelet storage lesions. However, in special circumstances, manual-mixing can be alternatively used to store products for short time periods without compromising platelet quality. Based on this finding, and given the role of shear stress in modulating receptor expression, we were interested in comparing the levels of platelet adhesion receptor, GPVI and platelet adhesion capacity under each storage condition.

METHODS

Platelet concentrates (PCs) were divided into three groups: continuously-agitated PCs (CAG-PCs) with or without PP2 (Src kinase inhibitor) and manually-mixed PCs (MM-PCs). Platelet count/MPV, swirling, GPVI and P-selectin expression, GPVI shedding, platelet adhesion/spreading to collagen were examined during 5 days of storage.

RESULTS

While MM- and CAG-PCs showed similar levels of P-selectin expression, GPVI expression was significantly elevated in MM-PCs with lower GPVI shedding/expression ratios, enhanced platelet adhesion/spreading and swirling in manually-mixed PCs. Of note, CAG-PCs treated with PP2 also demonstrated lower P-selectin expression and GPVI shedding, higher GPVI expression and attenuated swirling and spreading capability.

CONCLUSION

Given the comparable platelet activation state in MM and CAG-PCs as indicated by P-selectin expression, enhanced platelet adhesion/spreading in MM-PCs, along with relatively higher GPVI expression here, supports previous studies demonstrating a role for biomechanical forces in modulating GPVI-dependent function. Thus, lower GPVI expression in CAG-PCs may be due to shear forces induced by agitation, which keeps this receptor down-regulated while also attenuating platelet adhesion/spreading capacities during storage. Low platelet function in PP2-CAG-PCs also highlights the importance of Src-kinases threshold activity in maintaining platelets quality.

Platelets: handle with care

Platelets are delicate cells that require careful handling between collection, preparation and transfusion. This review addresses practical questions relating to platelet concentration, resting time after collection, total time and number of periods without agitation and temperature. The bags in which platelets are stored are made from gas-permeable plastic to allow sufficient oxygen for the platelets to maintain aerobic respiration. Manufacturers have assigned limits for platelet content and concentration, and these must not be exceeded. There is no strong evidence for or against the resting of platelets post-collection and pre-agitation, but platelets should not be over-wrapped during this period as this compromises gas exchange; a short rest period of up to 1 h may allow the separation of minor aggregates. It is necessary to transport platelet concentrates (e.g. from manufacturing site to hospital), but these periods without gas exchange must be limited to avoid excessive damage to the platelets. Current data support a total of 24 h of transportation per component but with no individual period lasting more than 8 h. Platelets need to be stored at 20-24 °C based on evidence that colder storage leads to irreversible changes on the platelet membrane, resulting in phagocytosis of the platelets following transfusion. Storage at warmer temperatures may lead to an increase in bacterial risk. On the basis of this review, the UK Guidelines for Blood Transfusion Services have been updated to ensure that platelets are handled in the most appropriate way to ensure that efficacious components are provided for patients.

The effect of 24 h resting of old PCs at 22-24°С in permeable bags on in vitro platelet parameters

BACKGROUND

During transporting periods, platelet (PLT) concentrates (PCs) usually undergo a long period without agitation. Whether this interruption, improves quality and viability, or has deleterious effect at 72 h stored PCs, is here investigated. The aim of our study is to investigate effect of metabolic resting (24 h interruption of agitation) versus continue agitation of 72 h-stored PCs (old), prior to transfusion in the blood bank of Tehran.

STUDY DESIGN AND METHODS

PCs were prepared using the platelet-rich plasma (PRP) method and stored in the permeable bags in the shaker/incubator, for 72 h at 20-24°C. Then by simply stopping the agitator, PCs remained at stationary condition without agitation for 24 h (WA24h) before sampling. In vitro measurements of PLT quality were carried out just after the termination of interruption period, and the results were compared with continuously agitated platelet within the same day (designated as control group, CA). In vitro variables which are measured were pH, Platelet count, swirling, Ristocetin-induced aggregation (GPIb-related function), LDH, PF4 release and P-selectin expression (activation marker).

RESULTS

Compared with control group, the mean platelets PF4 release and P-selectin expression showed no significant differences (p=0.101, p=0.739 respectively). The mean level of pH was not significant (p=0.156); WA24h (7.12±0.14) and CA (7.17±0.11). Also Ristocetin-induced aggregation study showed significant differences (p=0.0281) between CA (76.6±3.2) and WA24h (62.69±21.43). Other in vitro variables between CA and WA groups including swirling, Platelet count and LDH showed no significant differences after 72 h of storage.

CONCLUSIONS

We observed that 24 h resting of old PCs (WA24h) at 22-24°С in permeable bags preserved pH, swirling, LDH, Ristocetin-induced aggregation and platelet's activation as good as control group after 72 h of storage.