In vivo tissue sampling of embryonic resorption sites using ultrasound guided biopsy

In the polytocous European brown hare (Lepus europaeus) more than 23% of all successful implantations undergo embryonic resorption. The objective of the study was to establish a minimally invasive ultrasound guided biopsy technique to collect embryonic resorption tissue in vivo. The sampled material was genetically analysed to determine paternity and the sex of the embryo. Female hares were either mated or artificially inseminated and pregnancy was confirmed by ultrasound on day six post ovulation. Subsequent embryonic development was ultrasonographically monitored on a regular basis to detect embryos undergoing resorption. Cell material of the resorption site was collected under ultrasonographic control via transabdominal biopsy of the placenta or aspiration of resorption fluid. To avoid breathing movements during the biopsy, the animals were intubated and a short apnoea was evoked by assisted ventilation. The presence of embryonic cells in the biopsy material was confirmed by microsatellite analysis in 11 of the fluid samples (n = 28) and six of the placental samples (n = 8). The lower success rate in the fluid samples was attributed to the abundance of maternal cells which was confirmed by the analysis of fluid sample smears. Male sex of the embryos undergoing resorption was detected by SRY analysis for ten of the fluid samples and for one of the placental samples. The two biopsy techniques did not have any negative impact on the prenatal development of the healthy siblings nor did it influence the future breeding performance of the females that were biopsied.