Some processes used to sterilize blood for transfusion are harmful to platelet function and could cause serious health issues in transfusion recipients, researchers say.
They found that some pathogen-reduction treatments impact platelets to the extent that they may be the cause of hemorrhages in recipients.
The pathogen reduction treatments “were developed more than 20 years ago, before we understood the importance of the genetic material contained in platelets,” explained study author Patrick Provost, PhD, of Université Laval and the CHU de Québec Research Center in Canada.
Platelets contain up to a third of the human genome in the form of ribonucleic acid (RNA), which enables them to synthesize over 1,000 proteins essential to the normal functioning of the human body.
The researchers studied the effects of 3 pathogen-reduction strategies—irradiation, riboflavin plus UVB light (Mirasol), and amotosalen plus UVA light (Intercept)—on platelet microRNAs, messenger RNAs (mRNAs), activation, and function.
They reported their findings in the journal Platelets.
The investigators collected 50 single-donor (apheresis) platelet concentrates (PCs) and subjected them to 5 treatments.
The control platelets were stored in donor plasma; additive solution platelets were stored in 65% storage solution and 35% donor plasma; the irradiation platelets were treated with 30Gy gamma irradiation and stored in donor plasma; the platelets treated with Mirasol were stored in donor plasma; and the platelets treated with Intercept were stored in the same solution as the additive solution group.
All treatments followed standard procedures or the manufacturer’s instructions.
After platelet isolation and RNA extraction, the investigators analyzed the levels of microRNA and mRNA levels of the platelets and assessed the impact of those levels on platelet activation and function.
MicroRNA profiles
They learned that platelets stored with additive solution or irradiation had significantly (P<0.05) reduced levels of one microRNA each, and only on day 7 of storage. Additive solution reduced the level of miR-223 and irradiation reduced the level of let-73.
Mirasol did not significantly reduce the level of any of the 11 tested micro RNAs.
And Intercept significantly reduced the level of 6 microRNAs on day 1, 1 microRNA on day 4, and 2 microRNAs on day 7. By day 7, let-7e was reduced by up to 70%.
The microRNA levels remained stable in the control sample for the entire 7-day storage period.
Platelet activation and function
Platelet counts in the Mirasol- and Intercept-treated platelets were significantly lower (P<0.001) on storage days 1, 4, and 7 compared with control platelets.
Pathogen-reduction treatments did not affect platelet microRNA synthesis, platelet microRNA function, nor did they induce the formation of cross-linked RNA adducts.
However, pathogen reduction caused platelet activation, which correlates with the observed reduction in platelet microRNAs.
The investigators measured CD62P expression, a marker of platelet activation, on the platelet surface. The additive solution platelets and Intercept-treated platelets, and to a lesser degree the irradiation group, had greater CD62P surface expression than the control group (P<0.05) on day 1.
The Mirasol group had similar activation to that of the control group.
On day 4, all treatment groups showed more activation than the control group (P<0.05). And on day 7, all groups had about the same activation level as the control group.
Pathogen reduction also impacted the aggregation response of platelets. Mirasol-treated platelets, which had the same aggregation response as that of controls on day 1, had no response on days 4 and 7.
And the aggregation response for Intercept-treated and additive solution platelets was already absent on day 1 and remained so on days 4 and 7.
Additive solution and Intercept also reduced platelet volume on day 1, which the investigators say could be explained by the platelet activation and release of microparticles induced by the treatments.
MicroRNA release
The investigators hypothesized that activated stored platelets could release microRNAs through microparticles in the supernatant. So they collected supernatant from each of the 5 groups and analyzed their total content of miR-223, which is one of the most abundant platelet microRNAs.
They discovered that the total amount of miR-223 was increased 30% to 86% in the microparticles released from additive solution and Intercept-treated platelets. They did not observe this increase in irradiation- or Mirasol-treated platelets compared to controls.
"The platelets end up depleted of RNA so, once transfused, they're unable to do what they normally would," Dr Provost said. Nevertheless, the clinical implications of the reduction in platelet activation and impaired platelet aggregation after Intercept treatment remain to be established.
The pathogen-reduction treatments are already marketed in some European countries, notably Switzerland, France, and Germany, and are under consideration in other countries, including Canada and the United States.
"In light of what we have demonstrated, the potentially harmful effects of these treatments should be carefully evaluated in the countries where they are not yet approved. It should also be re-evaluated in those countries where they are," Dr Provost said.
