Characterization of Surface Markers of Reticulated Young Platelets Compared with Mature Platelets

Adi Lador 1 Dorit Leshem-Lev 2 Galia Spectre 4 Aryeh Abelow 3 Ran Kornowski 1 Eli Lev 1
1Cardiology Department, Rabin Medical Center, Beilinson Campus, Petah-Tikva
2The Felsenstein Medical Research Center, Rabin medical center, Beilinson Campus, Petah-Tikva
3Internal Medicine A, Rabin Medical Center, Beilinson Campus, Petah-Tikva
4Department of Hematology, Rabin Medical Center, Beilinson Campus, Petah-Tikva

Backgrounds: Platelets play a pivotal role in the development of atherothrombotic events. Reticulated platelets (RPs) are "young" platelets with high dense granules content and a residual amount of megakaryocyte-derived mRNA. Increased levels of RPs have been found to be independent predictors of cardiovascular death, and were correlated with impaired response to various anti-platelet drugs. We hypothesized that intrinsic factors of RPs may be responsible for the hyper-reactivity and attenuated response to antiplatelet therapy.

Objective: To characterize the surface markers of RPs compared with mature platelets

Methods: Platelets from healthy individuals and diabetic patients were tested at rest and after activation with 10µl ADP. For each patient we calculated the proportion of RPs among the platelet population, using flow cytometry assay with Thiazole orange staining (for RPs) and CD42b platelet-specific antibody. We also determined platelet activation markers PAC-1binding and P-selectin expression, (double staining flow cytometry) .

Results: A total of 28 subjects were recruited (11 healthy individuals, 19 diabetics). In resting platelets we found that, unexpectedly, mature platelets expressed higher levels of P-selectin and PAC-1 binding compared to RPs (P-selectin: 12.6% vs. 1.95%, P=0.012; PAC-1binding 97.2%vs. 80.5%, P=0.035, respectively). However, following activation, RPs demonstrated a significant increase in the levels of P-selectin and PAC-1 binding (P-selectin – 12% increase, PAC-1– 13% increase from resting state), while mature platelets had no change in platelet activation markers following ADP activation.

Conclusion: At rest mature platelets express a higher level of platelet activation markers, compared to RPs. However, following activation RPs, but not mature platelets, exhibited an increase in P-selectin expression and PAC-1 binding and thus appear to have a higher capacity for platelet activation.









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