A Human Stem Cell Model of Fabry Disease Implicates LIMP-2 Accumulation in Cardiomyocyte Pathology

摘要

class="head no_bottom_margin" id="sec1title">IntroductionFabry disease (FD) is an inherited lysosomal storage disorder (LSD) caused by mutations in the GLA gene on the X chromosome, leading to the deficiency of α-galactosidase A (α-gal A). FD is rare, but LSDs as a group have an incidence of approximately 1:5,000–1:10,000, and may share overlapping pathological mechanisms (, ). FD is characterized by the progressive intracellular accumulation of globotriaosylceramide (GL-3) throughout the body, particularly in the vascular tree, nervous system, kidney, and heart (). Most patients develop cardiac involvement, with common manifestations including left ventricular hypertrophy, arrhythmias and conduction disturbances (). With disease progression, extensive myocardial fibrosis and impaired left ventricular function can develop, and cardiac disease has become the main cause of mortality in FD (). Enzyme replacement therapy has provided a major therapeutic advance. However, in the heart, clearance of GL-3 from cardiomyocytes (CMs) has not been demonstrated, in contrast to the robust clearance from endothelial cells (, ).A major obstacle for advancing therapy for patients with FD is the knowledge gap between the direct molecular consequences of α-gal A deficiency in CMs and the cascade of events driving disease in the heart; the inaccessibility of CMs from patients precludes adequate investigation of these events, especially at early stages. Whether intrinsic myocardial dysfunction drives disease progression and is a primary cause of the electrophysiological and contractile disturbances remains unclear, but is supported by the following evidence: electrocardiogram abnormalities such as a shorter P wave duration, PR interval, and QRS complex indicate an acceleration in both atrial and ventricular conduction in early-stage FD (), implying that GL-3 accumulation may alter cellular conductive properties; and mechanical defects have been reported in a rare example where patient CMs have been available for in vitro investigation ().Recently, our group reported the generation of induced pluripotent stem cells (iPSCs) from patients with FD carrying non-sense mutations in GLA (). This model presents the possibility, for the first time, to systematically study the consequences of α-gal A deficiency in CMs at the molecular and functional level and to identify new disease biomarkers. Biomarkers could provide valuable direction for mechanistic investigation and help elucidate the pathological cascades in FD; systemic biomarkers could have further utility for monitoring disease status, response to therapy, and for identifying patients at high risk of cardiac complications.Using a carefully standardized iPSC cardiac differentiation model, here we provide quantitative data at proteome scale on the cellular phenotype of CMs carrying GLA mutations (Fabry CMs). We have identified functional differences in these cells that are consistent with clinical data, and discovered several novel cellular and secreted protein biomarkers. The accumulation of LIMP-2, a lysosomal protein with suggested roles in heart disease, was a robust consequence of α-gal A deficiency, and could drive protein secretion, implying a fundamental role in FD pathology. These new data support the exciting potential of this model for delivering translational benefit for patients with FD.