INDUCED PLURIPOTENT STEM CELLS GENERATED FROM WISKOTT-ALDRICH SYNDROME PATIENTS SHOWED DEFECTS IN PLATELET PRODUCTION IN VITRO

Abstract

Wiskott aldrich syndrome, an x-linked immunodeficiency disorder, caused by the mutation in WASP gene. WASP has been known as a regulator of actin reorganization in hematopoietic cells but its role in microthrombocytopenia, which is the hallmark of WAS, is largely unknown. Available WAS disease models failed to reproduced WAS platelet defects both in vivo and in vitro. In this study, we reported the generation of WAS-iPSCs from 2 patients with WASP mutation. Although, the hematopoietic and megakaryocytic differentiation potential of WAS-iPSC lines were comparable to the wild-type iPSCs, WAS-iPSC derived megakaryocytes exhibited abnormal proplatelet formation with thin proplatelet shaft, less in number of proplatelet branching and platelet swelling. Small size platelet buds at the proplatelet end observed in WAS-iPSCs correlated with their small platelet size. Restoration of WASP expression by lentiviral and isogenic model could rescued the defects in proplatelet formation and platelet size was increased. Our results showed for the first time that WASP play important roles in regulating proplatelet formation and controlling platelet size. Furthermore, xenotransplantation of hematopoietic progenitor cells derived from isogenic model showed multilineage engraftment including lymphoid lineage. Our result illustrated the potential of using iPSCs for modeling the disease mechanism in thrombopoiesis and serving as an unlimited cells source for future cell replacement therapy.