CYCLOPHOSPHAMIDE-INDUCED TERATOGENESIS IN ICR MICE - THE ROLE OF APOPTOSIS

It is known that programmed cell death (apoptosis) is an important phy siological determinant of embryonic development. In parallel, it may b e one of the major events involved in induced teratogenesis. The prese nt study was designated to evaluate to what extent is apoptosis involv ed in the formation of some final abnormalities induced by cyclophosph amide (CP) in ICR mice. The level of apoptosis in limbs, tail, liver, and whole embryo was assessed 24 h after administration of various dos es of CP (day 12 of pregnancy) by flow cytometric analysis and by DNA fragmentation assay. In parallel, the rate of limb and tail malformati ons, resorptions, and growth retardation induced by various doses of C P was evaluated in animals sacrificed on day 19 of pregnancy using rou tine teratological methods. A striking correlation between the rate of CP-induced apoptosis in limb and rail cells and the severity of limb and tail anomalies was found after administration of CP ranging from 1 0 to 40 mg/kg. Thus, the percent of apoptotic cells collected from lim bs and tails increased from is to 78%. In parallel, the severity of li mb and tail anomalies increased from digit anomalies to amely and from crooked to short or absent tail. CP-induced embryolethality and fetal growth retardation also correlated with the level of apoptosis in cel ls collected from whole embryos but to a lesser extent. These results claim that CP-induced apoptosis is one of the inevitable events in the pathway leading to the formation of CP-induced abnormalities and also suggest that the extent of the involvement of apoptosis in the format ion of different types of final abnormalities, may be different. (C) 1 995 Wiley-Liss, Inc.