Silica microbeads capture fetal nucleated red blood cells for noninvasive prenatal testing of fetal ABO genotype

Exploration of a Novel Noninvasive Prenatal Testing Approach for Monogenic Disorders Based on Fetal Nucleated Red Blood Cells

BACKGROUND

Due to technical issues related to cell-specific capture methods, amplification, and sequencing, noninvasive prenatal testing (NIPT) based on fetal nucleated red blood cells (fNRBCs) has rarely been used for the detection of monogenic disorders.

METHODS

Maternal peripheral blood was collected from 11 families with hereditary hearing loss. After density gradient centrifugation and cellular immunostaining for multiple biomarkers, candidate individual fetal cells were harvested by micromanipulation and amplified by whole-genome amplification (WGA). Whole-exome sequencing/whole-genome sequencing (WGS) and Sanger sequencing were performed on the identified fNRBCs to determine the fetal genotype. The impact of single-cell and pooled WGA products on the sequencing quality and results was compared. A combined analysis strategy, encompassing whole-exome sequencing/WGS, haplotype analysis, and Sanger sequencing, was used to enhance the NIPT results.

RESULTS

fNRBCs were harvested and identified in 81.8% (9/11) of families. The results of cell-based-NIPT (cb-NIPT) were consistent with those of invasive prenatal diagnosis in 8 families; the coincidence rate was 88.9% (8/9). The combined analysis strategy improved the success of cb-NIPT. The overall performance of pooled WGA products was better than that of individual cells. Due to a lack of alternative fetal cells or sufficient sequencing data, cb-NIPT failed in 3 families.

CONCLUSIONS

We developed a novel fNRBC-based NIPT method for monogenic disorders. By combining multiple analysis strategies and multiple fetal cell WGA products, the problem of insufficient genome information in a single cell was remedied. Our method has promising prospects in the field of NIPT for the detection of monogenic disorders.

Noninvasive prenatal diagnosis targeting fetal nucleated red blood cells

Noninvasive prenatal diagnosis (NIPD) aims to detect fetal-related genetic disorders before birth by detecting markers in the peripheral blood of pregnant women, holding the potential in reducing the risk of fetal birth defects. Fetal-nucleated red blood cells (fNRBCs) can be used as biomarkers for NIPD, given their remarkable nature of carrying the entire genetic information of the fetus. Here, we review recent advances in NIPD technologies based on the isolation and analysis of fNRBCs. Conventional cell separation methods rely primarily on physical properties and surface antigens of fNRBCs, such as density gradient centrifugation, fluorescence-activated cell sorting, and magnetic-activated cell sorting. Due to the limitations of sensitivity and purity in Conventional methods, separation techniques based on micro-/nanomaterials have been developed as novel methods for isolating and enriching fNRBCs. We also discuss emerging methods based on microfluidic chips and nanostructured substrates for static and dynamic isolation of fNRBCs. Additionally, we introduce the identification techniques of fNRBCs and address the potential clinical diagnostic values of fNRBCs. Finally, we highlight the challenges and the future directions of fNRBCs as treatment guidelines in NIPD.

Non-Invasive Prenatal Testing in Germany

In the short 10 years following the introduction of non-invasive prenatal testing (NIPT), it has been adapted in many countries around the world as a standard screening test. In this review, this development was analyzed with a special focus on Germany. As a result, it can be stated that all known advantages of NIPT apart from "compensating for having no access to centers offering invasive diagnostics" are valid for Germany. In addition, following a review of the international literature, all documented issues with NIPT are also observed in Germany. However, the German Gene Diagnostics Act (GenDG) addresses a number of these issues, for example, the regulations by GenDG hamper induced abortions, based exclusively on an abnormal NIPT result. At the same time, GenDG has created new problems, as a possible collusion between the "right not to know with regard to parts of the examination result" may occur, or that the sex of the fetus must not be reported to the pregnant woman before the 12th week of gestation. Main conclusions drawn are that appropriate training and the continuing education of the physicians providing NIPT-related counseling are needed, as well as the provision of balanced and comprehensive information for the pregnant woman or the couple that is imperative.

Research Progress in Isolation and Enrichment of Fetal Cells from Maternal Blood

Prenatal diagnosis is an important means of early diagnosis of genetic diseases, which can effectively reduce the risk of birth defects. Free fetal cells, as a carrier of intact fetal genetic material, provide hope for the development of high-sensitivity and high-accuracy prenatal diagnosis technology. However, the number of fetal cells is small and it is difficult to apply clinically. In recent years, noninvasive prenatal diagnosis (NIPD) technology for fetal genetic material in maternal peripheral blood has developed rapidly, which makes it possible to diagnose genetic diseases by fetal cells in maternal peripheral blood. This article reviewed the current status of fetal cell separation and enrichment technology and its application in noninvasive prenatal diagnosis technology.

Isolation of circulating fetal trophoblasts by a four-stage inertial microfluidic device for single-cell analysis and noninvasive prenatal testing

Noninvasive detection of circulating fetal cells carrying the entire fetal genome is a promising way for prenatal testing of genetic diseases. However, ideal approaches for efficient separation of these valuable cells are not available. Here, a novel inertial microfluidic chip (CelutriateChip 1) is developed for ultra-fast, label-free enrichment of circulating trophoblasts (CTBs) from the whole blood samples of pregnant women. The unique structural design of the four-stage curved channel in CelutriateChip 1 enables CTBs with larger size to be efficiently separated from the blood samples under the effect of inertial and Dean drag forces. The transition of the target cells among the stages enables CelutriateChip 1 to achieve one or two orders of magnitude higher throughput compared to single channel inertial microfluidic chips. After optimization of conditions, CTBs can be recovered from 2 mL of whole blood within 5 min with an average recovery efficiency ranging from 52.3% to 65.8% and high white blood cell depletion (99.95%). CTBs collected from the chip can be isolated at the single-cell level and used for downstream immunofluorescence staining and genetic genotyping. Clinical tests are performed on 30 pregnant women and the results demonstrate that CTBs are obtainable in 86.67% of pregnancy cases. A single-base variant in the HBB gene can be accurately detected by sequencing of rare CTBs. This simple, antibody-free and low-cost approach holds promise for obtaining rare CTBs for prenatal detection of various genetic diseases.