孕妇外周血胎儿游离DNA的检测及应用研究

从1997年首次在孕妇外周血中发现胎儿DNA以来,众多学者致力于将其应用于无创性的产前诊断。荧光定量PCR实现了胎儿游离DNA浓度的检测,目前研究发现,正常孕妇血浆胎儿DNA浓度稳定于某一水平,有望成为产前诊断和孕期检测的一项新指标。有学者认为,子痫前期母循环中胎儿DNA可有异常增高,而且子痫前期的孕妇在有临床症状前,孕妇血浆胎儿DNA水平异常增高,这与较多胎儿DNA释放到母血中,和肝肾功能异常导致胎儿DNA在母血中清除紊乱有关。此外许多妊娠合并症和并发症都伴有母外周血DNA水平的异常增高,例如:性连锁疾病、Rh血型不合、父系遗传性疾病、染色体非整倍体胎儿、早产等。现就孕妇外周血胎儿游离DNA的检测及临床应用作一综述。     

孕妇血浆中游离胎儿DNA测定在产前诊断中的应用

传统的羊膜腔穿刺和绒毛吸取是目前许多医院较为常用的产前诊断技术，因其操作易导致流产、胎儿损伤或死亡、宫内感染、羊膜破裂等，使其在临床上的推广和应用受到了限制。利用孕妇外周血中的胎儿细胞进行遗传学诊断一直是无创性产前诊断的重要探索途径。但由于孕妇外周血中的胎儿细胞数量少，而且存在个体差异，目前很难从外周血中分离出完整的胎儿细胞，这无疑限制了这种方法在临床上的应用。1997年，有学者研究发现，孕妇血液循环中存在较丰富的游离胎儿DNA，这一发现为无创性产前诊断和筛查开辟了新领域。     

孕妇外周血中胎儿DNA水平检测在子痫前期诊断中的应用

目的探讨孕妇外周血中胎儿DNA水平检测在子痫前期诊断中的应用价值。方法选择30例子痫前期孕妇为子痫前期组(其中轻度18例,重度12例),另选择30例正常孕妇作为对照组,两组孕妇分别于孕20周、孕晚期(子痫前期组孕33周+3、对照组孕34周+3)、分娩后1、3、6 h取外周血,采用荧光定量PCR检测外周血中Y染色体上的性别决定基因(SRY基因)胎儿DNA水平(B超确定两组孕妇所妊娠的胎儿均为男性);放射免疫法检测两组孕妇孕晚期内皮素水平。结果(1)子痫前期组孕20周时的胎儿DNA水平为(316±61)copy/m l,其中轻度、重度患者分别为(266±79)、(396±91)copy/m l;对照组孕妇为(165±43)copy/m l,子痫前期组及轻度、重度患者明显高于对照组,两组比较,差异有统计学意义(P<0.01)。(2)子痫前期组孕晚期胎儿DNA水平为(970±413)copy/m l,其中轻度、重度患者分别为(758±357)、(1285±573)copy/m l,对照组孕妇为(319±99)copy/m l,子痫前期组及轻度、重度患者明显高于对照组,两组比较,差异有统计学意义(P<0.01)。(3)子痫前期组产后1、3、6 h胎儿DNA水平分别为(139±45)、(76±31)、(44±13)copy/m l,其中轻度患者分别为(102±42)、(57±25)、(36±12)copy/m l,重度患者分别为(209±51)、(97±40)、(52±17)copy/m l;对照组分别为(33±13)、(9±5)、0 copy/m l。子痫前期组及轻度、重度患者明显高于对照组,两组比较,差异有统计学意义(P<0.01)。(4)子痫前期组内皮素水平为(80±18)ng/L,其中轻度患者为(74±14)ng/L,重度患者为(89±32)ng/L;对照组为(50±11)ng/L,子痫前期组及轻度、重度患者明显高于对照组,两组比较,差异有统计学意义(P<0.01)。(5)子痫前期组胎儿DNA水平与内皮素水平呈正相关关系(r=0.748,P<0.01)。结论孕妇外周血胎儿DNA水平变化可以作为预测和诊断子痫前期发病与疾病程度的一个指标。     

孕妇外周血中ERG基因甲基化状态及定量研究

目的:探讨ERG基因作为孕妇外周血中胎儿特异性标记物的可行性。方法:随机选取健康未妊娠妇女5例、正常妊娠孕妇65例、产后3天妇女20例的外周血样本,以及早期妊娠行人流的绒毛组织样本10例。应用甲基化敏感限制性内切酶PCR(MSRE-PCR)及荧光定量PCR方法检测样本中ERG基因甲基化状态,并进行相对定量分析。结果:(1)健康未妊娠妇女、顺产后3天妇女外周血浆及孕妇血细胞中均未检出甲基化的ERG基因;(2)绒毛组织样本中甲基化的ERG基因检出率100%;(3)正常妊娠孕妇外周血浆中甲基化ERG基因检出率为76.9%,中期、晚期妊娠ERG基因的含量分别是早期妊娠的3.18倍和5.46倍。结论:甲基化的ERG基因是可靠的胎儿特异性标记;正常妊娠孕妇的外周血浆中甲基化的ERG基因的检出量随孕周增加而增加。     

孕妇外周血中胎儿细胞及DNA分离方法的比较

产前非创伤性诊断技术是国内外围生学关注的重要课题。近 10年来 ,由于相关分子生物学、流式细胞学技术的进展 ,人类对研究母亲外周血中胎儿细胞的工作迈进了一大步。但由于母血中胎儿细胞甚微 ,分离及纯化胎儿细胞的技术难点尚未解决 ,使该技术还无法在临床上广泛应用。本研究旨在探索可靠稳定的分离胎儿细胞和ＤＮＡ的方法 ,为产前诊断奠定基础。一、材料和方法1.材料来源 :(1)研究对象 :选择 1997年 10月至 1999年6月在武汉华中科技大学同济医学院附属同济医院妇产科进行产前检查的健康孕妇 15 3例。年龄 2 1～ 35岁 ,孕 5～ 41周 ,血红…     

子痫前期孕妇外周血浆中高甲基化SIM2基因的含量变化

目的:通过检测高甲基化SIM2基因来分析游离胎儿DNA在正常妊娠孕妇及子痫前期孕妇外周血浆中含量的变化。方法:共收集114例外周血浆样本(包括健康未妊娠女性志愿者10例,产后48小时健康女性10例,正常妊娠孕妇57例,子痫前期孕妇37例),利用HpaⅡ、MspⅠ分别对提取的血浆DNA进行甲基化酶切反应后再进行实时荧光定量PCR反应,相对定量法检测高甲基化SIM2基因的含量。结果:①10例健康未妊娠女性志愿者及产后48小时健康女性外周血浆中均未检测出高甲基化SIM2基因;②57例正常妊娠孕妇中有43例检测出高甲基化SIM2基因,在不同妊娠阶段高甲基化SIM2基因含量的差异有统计学意义,高甲基化SIM2基因的含量在中期妊娠是早期妊娠的2.33倍,晚期妊娠是早期妊娠的5.28倍;③37例子痫前期孕妇中有36例检出高甲基化SIM2基因,高甲基化SIM2基因的含量在轻度子痫前期孕妇血浆中是正常晚期妊娠的3.05倍,在重度子痫前期孕妇中是正常晚期妊娠的6.32倍。结论:高甲基化SIM2基因是可靠的胎儿特异性标记,在孕妇外周血浆中高甲基化SIM2基因的含量随妊娠进展而增加,与孕周有关。高甲基化SIM2基因在子痫前期孕妇血浆中含量明显增加,能够反应子痫前期疾病的严重程度。     

从孕妇外周血中分离胎儿有核红细胞方法学初探

从孕妇外周血中分离胎儿细胞进行无创性产前诊断成为新的研究热点,胎儿有核红细胞被认为是最理想的研究对象［１］。本研究采用简单的不连续密度梯度离心法分离富集孕妇外周血中有核红细胞,进行Ｙ染色体特异性ＤＹＺ１基因的聚合酶链反应（ＰＣＲ）扩增以预测胎儿性别,探讨胎儿有核红细胞用于无创性产前诊断的一些问题一、资料和方法　　１．研究对象孕龄６～１４周,年龄２１～３０岁的孕妇共４５例,分为细胞制片组１５例,包括早孕８例,中孕７例;胎儿性别预测组３０例,包括早孕１８例,中孕１２例。此外,以未婚、无妊娠史的２例女…     

孕妇外周血中低胎儿游离DNA浓度及处理方案

无创产前检测(non-invasive prenatal testing, NIPT)技术因其高灵敏度和特异度的特点已广泛应用于胎儿染色体异常的产前筛查之中。胎儿游离DNA浓度(fetal fraction, FF)是影响NIPT结果准确性的关键因素之一。不同检测平台对FF的最低阈值设定不同,FF达不到检测最低阈值是导致NIPT检测失败的重要原因之一。影响FF的因素众多,主要可分为生物学因素和实验相关因素。低FF也与妊娠期并发症或异常妊娠有一定相关性,其后续处理需引起重视。本文将从可能引起FF降低的因素及后续如何进行妊娠期管理等方面进行综述。     

孕妇外周血中胎儿细胞及胎儿DNA的检测

目的　建立从孕妇外周血中分离有核红细胞 (NRBC)及DNA的可靠方法 ,并鉴定其来源。方法　对88例孕妇外周血分别通过密度梯度离心法 ,流式细胞术 (FCM )和荧光激活细胞分离技术 (FACS)分离NRBCs。应用套式PCR技术对 6 5例孕妇血浆DNA进行正常男性SRY基因检测。结果　①NRBCs:2 7例样品经密度梯度离心 ,其中 14例分选到 1～ 10个NRBCs。FACS技术对 6 1例样品进行转铁蛋白受体阳性细胞 (CD71+ )分选 ,所有样品均有CD71+ 细胞 ,其浓度为 (0 35± 0 2 5 )× 10 -2 。②胎儿DNA :4 6例怀男胎孕妇血浆DNA中SRY基因检测出率为 6 5 2 2 % (30 / 4 6 ) ,怀女胎的 19例样品SRY基因未检出率为 94 74 % (18/ 19)。结论　从孕妇外周血中分选胎儿NRBCs和血浆中胎儿DNA的方法已取得较大进展。利用母血中胎儿细胞及DNA诊断遗传性疾病可望成为最佳非创伤性产前诊断技术     

孕妇外周血富集分离胎儿细胞进行产前诊断

１９６９年,Ｗａｌｋｎｏｗｓｋａ首次报道在母血循环中可能存在胎儿细胞,随后一些学者相继证实了这一发现,但由于其含量极其稀少故很难用于产前诊断。到了１９９０年,随着分子生物学和细胞生物学等技术的完善,使得从母血循环中检测、分离胎儿细胞并用于产前遗传学诊...     

Non-invasive prenatal testing using massively parallel sequencing of maternal plasma DNA: from molecular karyotyping to fetal whole-genome sequencing

The discovery of cell-free fetal DNA in maternal plasma in 1997 has stimulated a rapid development of non-invasive prenatal testing. The recent advent of massively parallel sequencing has allowed the analysis of circulating cell-free fetal DNA to be performed with unprecedented sensitivity and precision. Fetal trisomies 21, 18 and 13 are now robustly detectable in maternal plasma and such analyses have been available clinically since 2011. Fetal genome-wide molecular karyotyping and whole-genome sequencing have now been demonstrated in a number of proof-of-concept studies. Genome-wide and targeted sequencing of maternal plasma has been shown to allow the non-invasive prenatal testing of β-thalassaemia and can potentially be generalized to other monogenic diseases. It is thus expected that plasma DNA-based non-invasive prenatal testing will play an increasingly important role in future obstetric care. It is thus timely and important that the ethical, social and legal issues of non-invasive prenatal testing be discussed actively by all parties involved in prenatal care.The discovery of cell-free fetal DNA in maternal plasma in 1997 has stimulated a rapid development of non-invasive prenatal testing. The recent advent of high-throughput sequencing technologies has allowed the analysis of circulating cell-free fetal DNA to be performed with unprecedented sensitivity and precision. A number of fetal chromosomal disorders are now robustly detectable in maternal plasma and such analyses have been available clinically since 2011. Moving beyond selected fetal chromosomal disorders, fetal single-gene disorders and even fetal whole-genome analysis have now been demonstrated in a number of proof-of-concept studies. It is thus expected that DNA-based non-invasive prenatal testing will play an increasingly important role in future obstetrics care. It is thus timely and important that the ethical, social and legal issues of non-invasive prenatal testing be actively discussed by all parties involved in prenatal care.     

Two-stage elevation of cell-free fetal DNA in maternal sera before onset of preeclampsia

Objective

The purpose was to determine whether preeclampsia (PE) is caused by microfragments of syncytial trophoblast shed into the maternal circulation that stimulate an exaggerated inflammatory response.

Study design

A nested case control study was performed within the Calcium for Preeclampsia Prevention trial cohort of healthy nulliparous women. Each preeclampsia case was matched to 1 normotensive control. One hundred twenty pairs were randomly chosen for analysis of serum cell-free fetal DNA (cffDNA), a marker of placental debris, and C-reactive protein (CRP), a marker of inflammation, in all 658 specimens obtained before labor.

Results

At 29 to 41 weeks of gestation, cffDNA concentrations were significantly higher after preeclampsia than before (219 vs 112 genome equivalents [GE]/mL, P<.001). Before preeclampsia, cffDNA in cases exceeded controls at 17 to 28 weeks (36 vs 16 GE/mL, P<.001), but at 29 to 41 weeks, only within 3 weeks before preeclampsia (176 vs 75 GE/mL, P<.001). CRP serum concentrations were neither associated with cffDNA nor elevated before preeclampsia.

Conclusion

Preeclampsia is accompanied by a 2-stage elevation of fetal DNA, but not by elevation of CRP. Elevated cffDNA at 17 to 28 weeks may be due to placental necrosis and apoptosis. Subsequent elevations may reflect impaired DNA elimination. The 2-stage elevation suggests the possibility of measurement of fetal DNA both to screen for preeclampsia and to indicate impending clinical disease.     

The effect of chorionic villus sampling on the fraction of cell-free fetal DNA in maternal plasma

Objective: This study aims to assess whether the fraction of cell-free fetal DNA (cffDNA) is different at 24?h or 7 days after chorionic villus sampling (CVS), compared to subjects that do not undergo CVS.

Methods: Pregnant women undergoing CVS for genetic testing and matched subjects undergoing first trimester combined screening alone were enrolled between 11^0/7 and 13^6/7 weeks gestation. The fractions of cffDNA were compared before the procedure, 24?h after and 7 days after between CVS patients and ultrasound-only patients.

Results: Forty-five women underwent CVS and 45 had ultrasound alone. The women undergoing CVS were, on average, older (36.8 years versus 28.5 years, p=0.001) and had a higher baseline fraction of cffDNA than women in the comparison group (11.4% versus 9.8%, p=0.033). Both groups had a decrease in the mean fraction of cffDNA after 24?h. After 7 days, the trend of the mean fraction of cffDNA continued to decline in the CVS group but began to trend toward an increase in the ultrasound only group.

Conclusions: CVS does not significantly increase the fraction of cell free fetal (placental) DNA in the maternal plasma. A downward trend in cffDNA in maternal plasma is seen at 24?h and 7 days following CVS compared to baseline.     

The fetal fraction of cell-free DNA in maternal plasma is not affected by a priori risk of fetal trisomy

Objective: To determine the relationship between a priori risk for fetal trisomy and the fraction of fetal cell-free DNA (cfDNA) in maternal blood. Methods: A comparative analysis on fetal cfDNA amounts was performed in subjects stratified into a priori risk groups based on maternal age, prenatal screening results, or nuchal translucency measurement. Results: Across the highest and lowest deciles within each group, there were no significant differences in the fetal cfDNA fraction. Conclusions: These data support the concept that non-invasive prenatal test performance as determined by fetal cfDNA fraction is not predicted to be different based on patient risk classification.     

孕妇血浆中胎儿游离mRNA检测在唐氏综合征产前诊断中的应用

目的探讨孕妇血浆中胎儿游离mRNA含量变化作为唐氏综合征产前筛查指标的可行性。方法选择2007年5月至2008年8月在上海交通大学医学院附属国际和平妇幼保健院就诊的26例孕中期(15～26周)妇女作为研究对象,其中13例为单胎行常规产科检查的孕妇(A组),9例为21-三体综合征胎儿的孕妇(B组),4例为其他染色体异常胎儿的孕妇(C组),提取其外周血血浆中游离mRNA,应用QF-PCR技术检测胎盘来源的HPL,β-HCG,TFPI2,DSCR4,LOC90625基因,以此确定母体血浆中的胎儿游离mRNA含量,并同时检测代表母体与胎儿总游离mRNA的18sRNA基因作为内参照。结果除TFPI2基因外,其他4种基因,在21-三体综合征胎儿孕妇组和其他染色体异常胎儿孕妇组血浆中胎儿游离mRNA含量明显高于正常胎儿孕妇组(P<0.01)。结论胎儿游离mRNA可能成为产前筛查唐氏综合征的有效指标。     

Non-invasive prenatal screening of fetal Down syndrome by maternal plasma DNA sequencing in twin pregnancies

Non-invasive prenatal screening for fetal Down syndrome (NIFTY) by maternal plasma sequencing was performed in 12 subjects with twin pregnancies, including 11 with normal fetuses and 1 with discordant fetal Trisomy 21. For every sample, it was processed, sequenced and reported as soon as it was collected as other clinical samples for singleton pregnancies. The NIFTY test was negative in the 11 pregnancies carried normal fetuses, and was positive (high risk) in the case with discordant fetal Trisomy 21. The sensitivity and specificity were both 100%. This small case series suggested the NIFTY as a screening test for fetal Trisomy 21 is feasible in twin pregnancies.