OBJECTIVETo establish a high sensitive and specific method of interphase fluorescence in situ hybridization (IFISH) to detect the low-frequency human cells in human/goat xenogeneic models.

METHODSHuman-specific Y-chromosome satellite DNA CEPY and 17-chromosome satellite DNA p17H8 were used as probes for IFISH. The peripheral blood samples from 2 goats transplanted with human male hematopoietic stem cells (HSC), 1 normal negative goat and 1 normal man were analyzed. The actual FISH efficiency was confirmed by serial dilutions (1/100, 1/500 and 1/1000) of the cell mixture of normal man and normal negative goat. A set of signal scoring criteria was determined to guarantee the stability and reliability of the method.

RESULTSPositive cell (human cell) frequencies were consistent with the established frequencies for the human/goat cell mixture. The average frequencies of positive cells were 98.60% (CEPY) and 100% (p17H8) for normal man, 0 for normal negative goat, 0.23% (CEPY) and 0.11% (p17H8) for human/goat xenogeneic models. The results demonstrated that low-frequency human cells (male cells confirmed by Y-chromosome probe) existed in human/goat xenogeneic models.

CONCLUSIONThe IFISH developed in this study is of high sensitivity and specificity and can identify the actual frequency of human cells, which offers a direct, sensitive and specific approach to the detection of low-frequency human cells in human/goat xenogeneic models.