AUTOMATED PRENATAL SCREENING USING MATERNAL BLOOD

非侵入性产前筛查的概念是由细胞遗传学家在60年代初构思的，并一直在稳步走向现实。科学家已经记录了母体血液中的胎儿细胞现象，并设想将其用于产前筛查。在母体血液中发现的胎儿细胞的微小比例，现在可以浓缩到几千人中有一人，非整倍体可以通过荧光原位杂交(FISH)和聚合酶链式反应(PCR)用染色体特异的DNA探针检测出来。目前医学细胞遗传学研究的最终目标是使低成本、低风险的产前基因筛查得到广泛应用。一个关键的限制因素是胎儿细胞的数量很少，这使得细胞检测工作密集，并限制了准确性。该项目的目标是开发一种复杂的培养方法和自动化系统，使其能够重复、公正和快速地检测母体血液中的少数胎儿细胞。在第一阶段项目中，我们实施了两个方面的方法，包括：(I)优化胎儿细胞培养方法，以及(Ii)开发用于检测胎儿细胞和进行非整倍体筛查的自动化系统。我们的实验结果表明，平均每3000个母体细胞中有1.6个胎儿细胞浓缩。我们构建了一个原型自动成像系统，集成了荧光自动聚焦、载玻片扫描、细胞检测和点计数算法。我们在不同比例(模拟实际胎儿和母体细胞比例)中添加了男性血液的女性血液样本上测试了该系统，以获得有关系统准确性的定量数据。最后，我们估计了系统可以实现的成本和时间节约，并确定了我们方法的可行性。在第二阶段，我们将进一步开发原型并在临床环境中进行测试。具体地说，我们将(1)优化软件以增强性能，(2)使用原型进行系统研究，(3)提高自动化系统检测胎儿细胞的特异性，处理标记FISH并通过免疫荧光染色检测胎儿血红蛋白的样本，(4)在临床环境中测试原型，以及(5)评估该仪器的商业可行性。第三阶段将专注于该系统的商业化，使几乎所有人都能获得胎儿筛查。拟议的商业应用：开发的仪器将被整合到PSI的细胞遗传学自动化设备的Powergene产品线中，用于销售的新系统，以及作为对细胞遗传学实验室已在使用的现有系统的升级。因此，在该项目下开发的技术将很快实现商业化。

The notion of a non-invasive prenatal screening test was conceived by cytogenetists in the early sixties and has been steadily moving toward reality. Scientists have documented the phenomenon of fetal cells in maternal blood, and envisioned their use in prenatal screening. The minute proportion of fetal cells found in maternal blood, can now be enriched to one per few thousand, and aneuploidies can be detected with chromosome specific DNA probes via fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR). The ultimate goal of current research in medical cytogenetics is to make low-cost, low-risk prenatal genetic screening widely available. A key limiting factor is the small number of fetal cells, which makes cell detection labor intensive, and limits accuracy. The goal of this project, is to develop a sophisticated method for enrichment and an automated system that will allow repeatable, unbiased and rapid detection of the few fetal cells in maternal blood. During the Phase I project, we implemented a two fold approach involving; (i) optimization of fetal cell enrichment methods, and (ii) development of an automated system to detect fetal cells and perform aneuploidy screening. Our experimental results indicate a mean enriched fetal cell proportion of 1.6 per 3000 maternal cells. We built a prototype automated imaging system, integrating fluorescence autofocusing, slide scanning, cell detection, and dot counting algorithms. We tested the system on samples of female blood spiked with male blood in varying proportions (mimicking actual fetal to maternal cell ratios), to obtain quantitative data on system accuracy. Finally, we estimated the cost and time savings achievable by the system and established the feasibility of our approach. In Phase II, we will further develop the prototype and test it in a clinical environment. Specifically, we will, (1) optimize the software for enhanced performance, (2) use the prototype to perform systematic studies, (3) increase the specificity of the automated system to detect fetal cells, processing samples both labeled with FISH, and stained via immunofluorescence for fetal hemoglobin, (4) test the prototype in a clinical environment, and (5) evaluate the commercial feasibility of the instrument. Phase III will focus on commercialization of the system, making fetal screening available to virtually the whole population. PROPOSED COMMERCIAL APPLICATIONS: The instrument developed will be incorporated into PSI's PowerGene product line of cytogenetics automation equipment, both in new systems sold and as an upgrade to existing systems already in use in cytogenetic labs. Thus commercialization of the technology developed under this project will occur quickly.