Abstract 21157: Establishing a Model for Congenital Atrioventricular Block using Human Embryonic Stem Cells
Congenital heart block (CHB) is an autoimmune disease caused by transplacental passage of maternal Ro and or La antibodies (Abs), occurring mainly in Lupus, Sjogren's Syndrome and asymptomatic mothers. Prenatal autoimmune injury to fetal cardiac tissue may cause CHB, which carries high mortality and need for pacing. Two theories regarding the pathogenesis of CHB exist: the electrophysiological (in which the Abs are believed to inhibit membrane calcium channels) and the apoptosis hypotheses.
Aims: To establish an in vitro model for CHB using human embryonic stem cells derived cardiomyocyte (hESC-CMs) and to investigate the potential contribution of the electrophysiological theory to disease pathogenesis.
Results: Specific IgG fraction of Abs from 3 mothers of children with CHB reactive to Ro and La antigens were obtained from the Research Registry for Neonatal Lupus. Staining of permibialized hESC-CMs with anti Ro/La revealed intense nuclear and weaker cytoplasmatic staining, confirming the expression of Ro/La antigens by the cells. Whole-cell patch-clamp recordings showed that Abs application (1serum tested) led to severe slowing of the hESC-CMs action potential frequency followed by complete cessation of beating, which was reversible after Abs washout. No effect was observed with normal IgG. Laser confocal calcium imaging was utilized to record Ca2+ transients. Abs application (2 sera) led to complete quiescence of Ca2+ transients in 7/12 of tested hESC-CMs and a decrease in Ca2+ transients' frequency in the rest of the cells, findings that were reversible by Abs washout. The effect of Abs was also tested at a multicellular level using a multielectrode array mapping system. Spontaneous beating frequency was reduced by 64±14% initially and stopped completely in 66% of cases after 7-24h. Beating resumed following washout at a rate of 0.7± 0.1 of baseline. A significant conduction slowing was also noted: tissue activation time increased by 2.6±0.2 fold.
Conclusions: Our study suggests that the hESC-CMs may serve as a unique model to study CHB, and as such it represents the first description for the use of hESC to study acquired diseases. Moreover, our results support the direct electrophysiological hypothesis as an important contributing mechanism to CHB.
- © 2010 by American Heart Association, Inc.