Hemodynamic Analysys in the Homozygous Embryo of the Endothelin-1 Knock-Out Mouse.

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 08671322
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Embryonic/Neonatal medicine
• Research Institution: Tokyo Women's Medical College
• Principal Investigator: MORISHIMA Masae Tokyo Women's Medical College, School of Medicine, Assistant, 医学部, 助手 (00241068)
• Co-Investigator(Kenkyū-buntansha): TOMITA Sachiko Tokyo Women's Medical College, School of Medicine, Assistant, 医学部, 助手 (40231451) ; YASUI Hiroshi Tokyo Women's Medical College, School of Medicine, Assistant, 医学部, 助手 (60210241) ; NAKAZAWA Makoto Tokyo Women's Medical College, School of Medicine, Professor, 医学部, 教授 (10075567)
• Project Period (FY): 1996 – 1997
• Keywords: fargeting disruption / Endothelin-1 / knock out mouse / cardiovascular a nomalies

Research Abstract

Background and Purpose : Kurihara et al.produced the endothelin-1 knockout mouse by gene targeting technique. The homozygotes presented abnormal formation of the cranial neural crest-derivatives, especially that of aortic arch arteries, at a high frequency. Moreover, they showed various degrees of dextroposition of the aorta at 20-30 %. The purpose of this study was to determine whether abnormal aortic arch altered hemodynamic status, inducing the cardiac outflow tract anomalies by down stream effect. Materials and Methods : We applied the whole embryo culture system to our observation method in that the embryos at embryonic days (EDs) 11-12, with the placenta, was put in a plastic bath irrigated with oxygen-saturated Hank's solution warmed up to around 37ﾟC.We observed the cardiac motion of the embryos with a stereo microscope and then recorded it with a high-speed video camera. We traced the border of the ventricles and then calculated the hemodynamic indices such as end-diastolic ve ntricular area and ejection fraction. We also measured ventricular pressure with aservo-null pressure system. The indices were compared between homozygotes and controls (heterozygotes and wild type). The embryos were fixed for morphology following hemodynamic experiment. Results : All homozygotes showed marked enlargement of the atrium and hypoplastic right ventricle (p<0.05) at EDs 11-12. At ED 11, ejection fraction of the right ventricle was higher than controls (p<0.05) but that of the left ventricle was not different between the two groups. However, at ED 12, ejection fraction of the right ventricle was lower than controls (p<0.05)、while that of the left ventricle had atendency to increase (no statistical significance). On the other hand, morphological examination revealed various severity of basic phenotypes : (1) hypoplasia and dysplasia of the proximal outflow tract cushions ; (2) decreased counterclockwise rotation of the distal outflow tract : (3) deviation of the outflow septum. As a result, they showed a spectrum of outflow tract anomalies encompassing dextroposition of the aorta and transposition of the great arteries. Discussion : We recognized the enlarged atrium and hypoplastic right ventricle at the beginning of this study, pointing to the possibility that the distensibility might be decreased. This possibility could not be verified by pressure measurement, however, the evaluation of the area-density ratio enabled us to ascertain the lowered distensibility of the right ventricle at the late phase of a-kick. Area measurement showed increased ejection fraction of the right ventricle at ED 11 while decreased ejection fraction at ED 12, indicating the change of systolic status of the right ventricle between EDs 11-12. Morphologically, the homozygotes exhibited a spectrum of outflow tract anomalies and were shown to be a useful model for studying the morphogenesis of transposition of the great arteries.