Evaluation of vascular effect of arsenic using in vivo assays

Arsenic (As) is an abundant toxicant present in groundwater and soil in various parts of the world including eastern part of India. The epidemiological studies have shown that arsenic exposure is linked to developmental defects and miscarriage. Placenta is known to utilize vasculogenesis to develop its vasculature circulation. The effects of four different doses of sodium meta-arsenite (0, 10, 20, 75, and 150 ppm) were assessed on the vascular structure using two different in vivo models, i.e., Matrigel and chorioallantoic membrane (CAM) assay. For the Matrigel assay, mice were exposed to different doses of arsenic through drinking water for 1 month. Placenta and Matrigel plug (which was inserted on gestational day (GD 0.5)) were removed on GD 14. Similar arsenic concentration was used in CAM assay to observe the effect of vessel development in hen's eggs. The CAM assay outcome evaluated by Angiosys software showed that arsenic exposure reduced the total and mean tubule length in all the arsenic-treated groups. The percentage tubule inhibition was declined significantly in 20, 75, and 150 ppm arsenic-treated groups as evaluated by ImageJ software. Analysis of the CAM outcome by both the image analysis software indicated the adverse effect of arsenic on the tubules. Further, a significant higher blood vessel density in 10 ppm and lower vessel density in 20, 75, and 150 ppm arsenic-exposed mice were also observed in Matrigel plug assay. The placental hypertrophy and dysplasia especially in the labyrinth zone (vasculature) were noted in placenta of arsenic-treated mice. The study indicated that higher arsenic exposures inhibited the angiogenesis which was dose-dependent in both CAM and Matrigel assay and altered structural morphology of placenta. However, no inhibition of blood vessels was noted at lower, i.e., 10 ppm of arsenic-treated group.