Evaluation of the Effect of Therapy on the Expression of Platelet Collagen Receptor Glycoprotein VI (GPVI) in Pediatric Patients with Chronic and Persistent Immune Thrombocytopenia

Abstract

Background: GPVI is the predominant platelet receptor for collagen that is essential for platelet adhesion and aggregation. Eltrombopag has been reported as an effective treatment for thrombocytopenia in chronic immune thrombocytopenia (ITP), yet its effect on platelet function in are not fully characterized. Aim: This prospective trial aimed to investigate the efficacy and safety of Eltrombopag therapy in pediatric patients with persistent and chronic ITP and its effect on platelet adhesion through assessment of glycoprotein VI (GPVI) receptor expression and soluble GPVI levels. Methods: Persistent or chronic ITP patients aged 1-18 years were screened, 36 were enrolled and divided equally into 2 groups either to receive eltrombopag therapy or the standard of care. All patients were followed-up for 12 months with assessment of bleeding score &complete blood count (CBC). Evaluation of the quality of life, bone marrow reticulin stain, GPVI expression using flow cytometry and measurement of the soluble form of GPVI by enzyme linked immunosorbent assay (ELISA) at baseline and at 6 months were performed. Results: Among all the studied patients, there were significant negative correlations between bleeding score and each of GPVI expression by flowcytometry and soluble GPVI levels and a positive correlation between platelet count and soluble GPVI levels. ITP patients who were on eltrombopag had significantly lower bleeding score after 6 months of therapy while the quality of life has significantly improved. Platelet count was significantly increased throughout the study. Moreover, GPVI expression by flowcytometry and soluble GPVI level were significantly increased after therapy. Similar results were found when compared with those not on eltrombopag. The number patients who lost complete response (CR) or response (R) was significantly lower among eltrombopag group than those without. Further follow-up of ITP patients who were on eltrombopag till 12 months after therapy showed that they were able to maintain a good quality of life and low bleeding score throughout the period. Conclusions: Our data suggest that Eltrombopag through its role in up-regulation of glycoprotein VI (GPVI) receptor expression and increase soluble GPVI levels, might have an effect on the platelet functions therefore reduce the bleeding manifestations, decrease the bleeding score and improve the quality of life of chronic and persistent ITP children independent of it effect on platelets count.