Method of separation and concentration of fetal nucleated red blood cells in maternal blood and its application to fetal diagnosis

Enhanced Isolation of Fetal Nucleated Red Blood Cells by Enythrocyte-Leukocyte Hybrid Membrane-Coated Magnetic Nanoparticles for Noninvasive Pregnant Diagnostics

Fetal nucleated red blood cells (fNRBCs) in maternal peripheral blood containing the whole genetic information of the fetus may serve for noninvasive pregnant diagnostics (NIPD). However, the fetal cell-based NIPD is seriously limited by the poor purity of the isolated fNRBCs. Recently, the biomimetic cell membrane-camouflaged nanoparticles containing outstanding features have been widely used to detect and isolate rare cells from the peripheral blood samples. In this work, enythrocyte (RBC) and leukocyte (WBC) membranes are fused and coated onto magnet nanoparticles and then modified with anti-CD147 to isolate fNRBCs from the maternal peripheral blood with significant efficiency (∼90%) and purity (∼87%) in simulated spiked blood samples. Further, fNRBCs were isolated and identified from a series of maternal peripheral blood samples coming from pregnant women of 11-13 gestational weeks, and different chromosomal aneuploidies were diagnosed using fNRBCs isolated from maternal blood in early pregnancy. Our strategy may offer additional opportunity to overcome the limitations of current cell-based NIPD platforms.

Highly sensitive and rapid isolation of fetal nucleated red blood cells with microbead-based selective sedimentation for non-invasive prenatal diagnostics

Non-invasive prenatal diagnostics (NIPD) has been an emerging field for prenatal diagnosis research. Carrying the whole genome coding of the fetus, fetal nucleated red blood cells (FNRBCs) have been pursued as a surrogate biomarker traveling around in maternal blood. Here, by combining a unique microbead-based centrifugal separation and enzymatic release, we demonstrated a novel method for FNRBC isolation from the blood samples. First, the gelatin-coated silica microbeads were modified with FNRBC-specific antibody (anti-CD147) to capture the target cells in the blood samples. Then, the density difference between microbead-bound FNRBCs and normal blood cells enables the purification of FNRBCs via an improved high-density percoll-based separation. The non-invasive release of FNRBCs can then be achieved by enzymatically degrading the gelatin film on the surface of the microbeads, allowing a gentle release of the captured target cells with as high as 84% efficiency and ∼80% purity. We further applied it to isolate fetal cells from maternal peripheral blood. The released cells were analyzed by real-time polymerase chain reaction to verify their fetal origin and fluorescent in situ hybridization to detect fetal chromosome disorders. This straightforward and reliable alternative platform for FNRBC detection may have the potential for realizing facile NIPD.

Fetal nucleated red blood cell analysis for non-invasive prenatal diagnostics using a nanostructure microchip

Cell-free DNA has been widely used in non-invasive prenatal diagnostics (NIPD) nowadays. Compared to these incomplete and multi-source DNA fragments, fetal nucleated red blood cells (fNRBCs), once as an aided biomarker to monitor potential fetal pathological conditions, have re-attracted research interest in NIPD because of their definite fetal source and the total genetic information contained in the nuclei. Isolating these fetal cells from maternal peripheral blood and subsequent cell-based bio-analysis make maximal genetic diagnosis possible, while causing minimal harm to the fetus or its mother. In this paper, an affinity microchip is reported which uses hydroxyapatite/chitosan nanoparticles as well as immuno-agent anti-CD147 to effectively isolate fNRBCs from maternal peripheral blood, and on-chip biomedical analysis was demonstrated as a proof of concept for NIPD based on fNRBCs. Tens of fNRBCs can be isolated from 1 mL of peripheral blood (almost 25 mL^-1 in average) from normal pregnant women (from the 10th to 30th gestational week). The diagnostic application of fNRBCs for fetal chromosome disorders (Trisomy 13 and 21) was also demonstrated. Our method offers effective isolation and accurate analysis of fNRBCs to implement comprehensive NIPD and to enhance insights into fetal cell development.

Practicability of prenatal testing using lectin-based enrichment of fetal erythroblasts

AIM

The aim of this study was to investigate the practicability and efficiency of lectin-based isolation of fetal erythroblasts for clinical use in non-invasive prenatal testing.

METHODS

Peripheral blood samples were collected from 39 pregnant women. Leukocytes were removed with an anti-CD45 antibody after density gradient centrifugation. After blood cells were attached to slides by binding to a galactose-specific lectin and galactose-bound vinyl polymer, the slides were stained with May-Grünwald-Giemsa stain and cells were classified by automated image analysis based on their size and the nuclear area/cytoplasmic area ratio. In 14 samples from the women with male fetuses, fetal origin of the isolated erythroblasts was confirmed by detecting the Y chromosome using fluorescence in situ hybridization. In eight samples, single erythroblasts were collected by the laser capture microdissection technique for amplification of the sex-determining region Y gene to confirm fetal origin.

RESULTS

Panning with an anti-CD45 antibody achieved stable removal of leukocytes without aggregation. In all samples, erythroblasts were successfully identified by automated image analysis (18-6000/10 mL of blood). The number of slides required to examine 10 mL of blood ranged from one to six, which was reasonable for clinical use. The Y chromosome was detected in 7.5-43.6% of erythroblasts by fluorescence in situ hybridization, and the sex-determining region Y gene was amplified in seven of eight samples.

CONCLUSION

The combination of lectin-based erythroblast isolation and automated image analysis is a practical and efficient method for isolating fetal erythroblasts as a source of fetal genomes.

The promise of fetal cells in maternal blood

Delaying childbirth increases the proportion of advanced maternal age pregnancies. This increases the number of pregnancies requiring invasive prenatal testing. Prenatal diagnosis of chromosomal aneuploidies and monogenic disorders requires fetal cells obtained through invasive procedures (i.e. chorionic villus sampling and amniocentesis). These procedures carry a risk of fetal loss, which causes anxiety to at-risk couples. Intact fetal cells entering maternal circulation have raised the possibility of non-invasive prenatal diagnosis. Rarity of fetal cells, however, has made it challenging. Fetal nucleated red blood cells are ideal candidate target cells because they have limited lifespan, contain true representation of fetal genotype, contain specific fetal cell identifiers (embryonic and fetal globins), and allow interrogation with chromosomal fluorescence in-situ hybridisation and possibly with array comparative genomic hybridisation. The utility of fetal nucleated red blood cells in non-invasive prenatal diagnosis has not reached clinical application because of the inconsistencies in enrichment strategies and rarity of cells.

Efficiency of manual scanning in recovering rare cellular events identified by fluorescence in situ hybridization: simulation of the detection of fetal cells in maternal blood

Fluorescence in situ hybridization (FISH) and manual scanning is a widely used strategy for retrieving rare cellular events such as fetal cells in maternal blood. In order to determine the efficiency of these techniques in detection of rare cells, slides of XX cells with predefined numbers (1–10) of XY cells were prepared. Following FISH hybridization, the slides were scanned blindly for the presence of XY cells by different observers. The average detection efficiency was 84% (125/148). Evaluation of probe hybridization in the missed events showed that 9% (2/23) were not hybridized, 17% (4/23) were poorly hybridized, while the hybridization was adequate for the remaining 74% (17/23). In conclusion, manual scanning is a relatively efficient method to recover rare cellular events, but about 16% of the events are missed; therefore, the number of fetal cells per unit volume of maternal blood has probably been underestimated when using manual scanning.

Enrichment of nuclear red blood cells by membrane KCC transporter with urea intervention

Intervention by membrane KCC transporter interfering selectively could promote about 5 times enrichment of nuclear red blood cells.

Enrichment and expansion of cells using antibody-coated micropallet arrays

Positive selection, sorting, and collection of single cells from within a heterogeneous population are required for many biological studies. We recently demonstrated a miniaturized cell array for this purpose; however, on-chip pre-enrichment and isolation of specific target cells would provide significant value for cell isolation. In the current work, mixed cell samples of fewer than 30,000 cells were used for panning by means of on-array antibody-capture to pre-enrich the target population. The cell surface receptors Fc(epsilon)R(1), c-Kit, and ErbB2 were used for positive selection of RBL, RBL, and SK-BR-3 cells, respectively, from the mixed population. The capture efficiency, selectivity, and enrichment for the target cells were calculated and compared with fibronectin-coated controls. As expected, the capture efficiency depended on the frequency of the target cell in the mixed population over the range of 0.3-33%. For a frequency of 5% target cells, the capture efficiency was 39%-53% for the three conditions, while the selectivity varied between 78% and 98% with 16-20-fold enrichment. Furthermore, single-cell cloning studies demonstrated a high cloning efficiency of target cells selectively isolated from the array. Antibody-based pre-enrichment in combination with micropallet-based cell selection will be a valuable tool for isolation and expansion of rare cells from small heterogeneous populations.

Biochip for separating fetal cells from maternal circulation

Isolation of fetal cells from maternal circulation is the subject of intense research to eliminate the need for currently used invasive prenatal diagnosis procedures. Fetal cells can be isolated using magnetic-activated cell sorting or fluorescence-activated cell sorting, however no technique to specifically isolate and use fetal cells for genetic diagnosis has reached routine clinical practice. This paper demonstrates the use of a micromachined device to separate fetal cells from maternal circulation based on differences in size and deformation characteristics. Nucleated fetal red blood cells range in diameter from 9 to 12 microm can deform and pass through a channel as small as 2.5 microm wide and 5 microm deep. Although the white blood cells range in diameter from 10 to 20 microm, they cannot deform and are retained by the 2.5 microm wide and 5 microm deep channels under our experimental conditions. Fetal cells were isolated from cord blood and DNA analysis confirmed their fetal origin with ruled out maternal contamination.