Characterization of cell death induced by 2-methoxyethanol in CD-1 mouse embryos on gestation day 8

Cell death was analyzed in neurulating mouse embryos after in vivo doses of 2-methoxyethanol (2-ME) that produce anterior neural tube defects. Charact erization of 2-ME-induced cell death was performed by evaluating: (1)vital fluorochrome staining in whole embryos applying confocal laser scanning mic roscopy; (2) characteristics of cell debris in conventional histological se ctions revealed by light microscopy; and (3) Apoptag(TM) in situ immunohist ochemical staining for apoptosis using light microscopy. Methods for quanti fication of cell death identified by these three techniques were explored u sing computerized image analysis. Physiological cell death in control embry os primarily occurred in the neural crest region during neural fold elevati on. Embryos exposed to 2-ME had expanded areas of cell death in the neural crest and also new areas of cell death in medial regions of the anterior ne ural tube. Both physiological and 2-ME-induced embryonic cell death had mor phological, immunohistochemical, and fluorochrome staining characteristics of apoptosis. When fluorescence data from confocal microscopic analysis of vital fluorochrome-stained embryos were analyzed, a dose-dependent increase was found in embryos exposed to 2-ME. Similar results were obtained when c ell death was analyzed in either conventional histological sections or sect ions prepared for immunohistochemical detection of apoptosis. The cell deat h data obtained in this study correlate with previously observed near-term malformation rates, suggesting that a quantitative relationship exists betw een 2-ME-induced embryonic cell death and neural tube defects. (C) 1998 Wil ey-Liss, Inc.