PB0662 - CyTOF and microRNAs reveal possible biomarkers for early diagnosis and treatment of Heparin Induced Thrombocytopenia (HIT).

Background: Acute and life-threatening complications are common in 2-5% of heparin administered patients. HIT is well correlated with the danger of arterial or vein thrombosis. Cardiothoracic patients are of high danger for HIT development as they have been repeatedly treated with heparin due to previous angiography. HIT syndrome is due to IgG antibody (Ab) formation against heparin-PF4 complexes causing strong activation and cross-linking of platelets through Fc receptors (FcγRIIa). Only a fragment of these patients develops “functional” Abs that can activate platelets and lead to thrombosis. Platelet microRNAs have been shown to contribute to Ab-mediated activation, the mechanism of platelet recruitment and clot formation, as well as to control immune responses that lead to HIT.

Aims: We investigated the possible implication of microRNAs and CyTOF analysis in HIT as well as the their possible use as early biomarkers for HIT.

Methods: We performed CyTOF analysis and RT-PCR for mir148a in patients with functionally active HIT antibodies and compared it to patients with non-funtional HIT Antibodies and patients with no HIT antibodies that served as controls.

Results: Our findings demonstrate significantly enhanced expression of miR148a in the plasma of patients with functionally active HIT Abs (HIT-pos), when compared with patients with non-active Abs, or patients without HIT-specific Abs which serve as negative controls. Moreover, platelets of HIT-pos patients had increased TULA-2 mRNA expression with a concomitant decrease in FcγRIIa mRNA expression, demonstrating that these genes interrelate and regulate each other. The HIT-pos group had also increased platelet expression of CD40L and plasma levels of pro-inflammatory cytokines TNF-α and IL-6. CyTOF analysis of all patient groups, employing 31 markers, demonstrated B-cells to be the major players in thrombosis induction.

Conclusion(s): Our results indicate that the number of B-cells over-expressing CD40 as well as miR148a could be utilized as a potential biomarkers for HIT prevention and treatment. Research funded by the Onassis Foundation