Sharpening the Tools: A summary of a National Institutes of Health workshop on new technologies for detection of fetal cells in maternal blood for early prenatal diagnosis

Incognito: Are Microchimeric Fetal Stem Cells that Cross Placental Barrier Real Emissaries of Peace?

Chimerism occurs naturaly throughout gestation and can also occur as a consequence of transfusion and transplantation therapy. It consists of the acquisition and long-term persistence of a genetically distinct population of allogenic cells inside another organism. Previous reports have suggested that feto-maternal microchimerism could exert a beneficial effect on the treatment of hematological and solid tumors in patients treated by PBSCT. In this review we report the mechanism of transplacental fetal stem cell trafficking during pregnancy and the effect of their long-term persistence on autoimmunity, GVHD, PBSCT, cancer and stem cell treatment.

Potential applications and human biosafety of nanomaterials used in nanomedicine

With the rapid development of nanotechnology, potential applications of nanomaterials in medicine have been widely researched in recent years. Nanomaterials themselves can be used as image agents or therapeutic drugs, and for drug and gene delivery, biological devices, nanoelectronic biosensors or molecular nanotechnology. As the composition, morphology, chemical properties, implant sites as well as potential applications become more and more complex, human biosafety of nanomaterials for clinical use has become a major concern. If nanoparticles accumulate in the human body or interact with the body molecules or chemical components, health risks may also occur. Accordingly, the unique chemical and physical properties, potential applications in medical fields, as well as human biosafety in clinical trials are reviewed in this study. Finally, this article tries to give some suggestions for future work in nanomedicine research. Copyright © 2017 John Wiley & Sons, Ltd.

Fetal Cell Based Prenatal Diagnosis: Perspectives on the Present and Future

The ability to capture and analyze fetal cells from maternal circulation or other sources during pregnancy has been a goal of prenatal diagnostics for over thirty years. The vision of replacing invasive prenatal diagnostic procedures with the prospect of having the entire fetal genome in hand non-invasively for chromosomal and molecular studies for both clinical and research use has brought many investigators and innovations into the effort. While the object of this desire, however, has remained elusive, the aspiration for this approach to non-invasive prenatal diagnosis remains and the inquiry has continued. With the advent of screening by cell-free DNA analysis, the standards for fetal cell based prenatal diagnostics have been sharpened. Relevant aspects of the history and the current status of investigations to meet the goal of having an accessible and reliable strategy for capturing and analyzing fetal cells during pregnancy are reviewed.

Lab-on-a-chip technology: impacting non-invasive prenatal diagnostics (NIPD) through miniaturisation

This paper aims to provide a concise review of non-invasive prenatal diagnostics (NIPD) to the lab-on-a-chip and microfluidics community. Having a market of over one billion dollars to explore and a plethora of applications, NIPD requires greater attention from microfluidics researchers. In this review, a complete overview of conventional diagnostic procedures including invasive as well as non-invasive (fetal cells and cell-free fetal DNA) types are discussed. Special focus is given to reviewing the recent and past microfluidic approaches to NIPD, as well as various commercial entities in NIPD. This review concludes with future challenges and ethical considerations of the field.

From prenatal genomic diagnosis to fetal personalized medicine: progress and challenges

Thus far, the focus of personalized medicine has been the prevention and treatment of conditions that affect adults. Although advances in genetic technology have been applied more frequently to prenatal diagnosis than to fetal treatment, genetic and genomic information is beginning to influence pregnancy management. Recent developments in sequencing the fetal genome combined with progress in understanding fetal physiology using gene expression arrays indicate that we could have the technical capabilities to apply an individualized medicine approach to the fetus. Here I review recent advances in prenatal genetic diagnostics, the challenges associated with these new technologies and how the information derived from them can be used to advance fetal care. Historically, the goal of prenatal diagnosis has been to provide an informed choice to prospective parents. We are now at a point where that goal can and should be expanded to incorporate genetic, genomic and transcriptomic data to develop new approaches to fetal treatment.

Integrating stakeholder perspectives into the translation of cell-free fetal DNA testing for aneuploidy

BACKGROUND

The translation of novel genomic technologies from bench to bedside enjoins the comprehensive consideration of the perspectives of all stakeholders who stand to influence, or be influenced by, the translational course. Non-invasive prenatal aneuploidy testing that utilizes cell-free fetal DNA (cffDNA) circulating in maternal blood is one example of an innovative technology that promises significant benefits for its intended end users; however, it is currently uncertain whether it will achieve widespread clinical implementation. We conducted qualitative interviews with 18 diverse stakeholders in this domain, including prospective users of the technology and healthcare personnel, researchers and developers, and experts in social, legal, and regulatory aspects of genetic technology, and a pilot survey of 62 obstetric healthcare providers. Analysis of interview and survey data was combined with a review of the proceedings of a full-day, multidisciplinary conference on the topic and published scientific and ethics literature surrounding this and other relevant technologies.

DISCUSSION

We constructed potential pathways for technological implementation, identified broad stakeholder classes party to these translational processes, and performed a preliminary assessment of the viewpoints and interrelations among these diverse stakeholders. Some of the stakeholders whose priorities are critical to understand and integrate into translation include pregnant women and their families; healthcare providers; scientists, their institutions or companies, and the funding agencies that support them; regulatory and judicial bodies; third-party payers; professional societies; educational systems; disability rights communities; and other representatives from civil society. Stakeholder interviews, survey findings, and conference proceedings add complexity to these envisioned pathways and also demonstrate a paramount need to incorporate an iterative stakeholder analysis early and throughout the translational endeavor. We believe that the translational framework that we have developed will help guide crucial future stakeholder mapping and engagement activities for cffDNA aneuploidy testing and inform novel methods of technology assessment for other developments in the growing field of genomic medicine.

SUMMARY

Mapping potential pathways for implementation and exploring the attitudes and interrelations of diverse stakeholders may lead to more effective translation of a novel method of prenatal aneuploidy testing.

Noninvasive prenatal detection and selective analysis of cell-free DNA obtained from maternal blood: evaluation for trisomy 21 and trisomy 18

OBJECTIVE

We sought to develop a novel biochemical assay and algorithm for the prenatal evaluation of risk for fetal trisomy 21 (T21) and trisomy 18 (T18) using cell-free DNA obtained from maternal blood.

STUDY DESIGN

We assayed cell-free DNA from a training set and a blinded validation set of pregnant women, comprising 250 disomy, 72 T21, and 16 T18 pregnancies. We used digital analysis of selected regions in combination with a novel algorithm, fetal-fraction optimized risk of trisomy evaluation (FORTE), to determine trisomy risk for each subject.

RESULTS

In all, 163/171 subjects in the training set passed quality control criteria. Using a Z statistic, 35/35 T21 cases and 7/7 T18 cases had Z statistic >3 and 120/121 disomic cases had Z statistic <3. FORTE produced an individualized trisomy risk score for each subject, and correctly discriminated all T21 and T18 cases from disomic cases. All 167 subjects in the blinded validation set passed quality control and FORTE performance matched that observed in the training set correctly discriminating 36/36 T21 cases and 8/8 T18 cases from 123/123 disomic cases.

CONCLUSION

Digital analysis of selected regions and FORTE enable accurate, scalable noninvasive fetal aneuploidy detection.

Separation and detection of rare cells in a microfluidic disk via negative selection

Cyto-analysis of rare cells often requires separation and detection with each procedure posing substantial challenges. This paper presents a disk-based microfluidic platform for both procedures via an immunomagnetic negative selection process. The microfluidic platform's unique features include a multistage magnetic gradient to trap labeled cells in double trapping areas, drainage of fluid to substantially shorten detection time, and a bin-like regions to capture target cells to facilitate a seamless enumeration process. Proof-of-concept was conducted using MCF7 as target rare cells (stained with anti-cytokeratin-FITC antibodies) spiked into Jurkat Clone E6-1 non-target cells (labeled with anti-CD45-PE and anti-PE BD magnetic beads). Then, mononuclear cells (MNC) from healthy blood donors were mixed with MCF7s, modeling rare cells, and tested in the disk. Results show a non-linear magnetic coupling effect of the multistage magnet substantially increased the trapping efficacy over that of a single magnet, contributing to the depletion rate of Jurkats, which reaches 99.96%. Detection time is extensively shortened by depletion of 95% of non-cell-containing fluid in the collection area. The average yield of detected MCF7 cells is near-constant 60 ± 10% over a wide range of rarity from 10(-3) to 10(-6) and this yield also holds for the MCF7/MNC complex mixture. Comparison with autoMACS and BD IMagnet separators revealed the average yield from the disk (60%) is superior to that of autoMACS (37.3%) and BD IMagnet (48.3%). The advantages of near-constant yield, roughly 30 min of operation, an acceptable level of cell loss, and potentially low cost system should aid in cyto-analysis of rare cells.

A unified approach to dielectric single cell analysis: impedance and dielectrophoretic force spectroscopy

In this review we present a unified approach for single cell dielectric spectroscopy. Impedance spectroscopy and dielectrophoretic cell sorting, current microtechnologies applied in electrical analysis of single cells are discussed based on their closely related physical principles. In addition, examples of microfluidic devices will be presented: a microfabricated flow cytometer for single cell discrimination based on impedance analysis and a miniaturized continuous dielectrophoretic cell sorter, both using the concept of liquid electrodes. Using the experimental results obtained from both microdevices, we give a comparative overview over the dielectrophoretic sorting and impedance spectroscopy.

Deportation of trophoblastic emboli to maternal lung: A source of cell-free DNA in maternal blood?

During human pregnancy there is a continuous transport of numerous syncytiotrophoblastic cells from the intervillous space of the placenta into the maternal lung. There these cells undergo apoptosis and the fetal nuclear DNA is liberated within the pulmonary capillaries to become cffDNA in the maternal serum. We have examined the sections of lungs of 11 pregnant women (from 8 weeks to term gestation) who had come to the Medical Examiner's Offices after their traumatic demise. We then identified the deported, embolized trophoblastic cells in pulmonary capillaries and attempted to show them to contain hCG immunohistochemically but were unable to do this. We also determined their apoptotic profiles by TUNEL reaction.

Fetal-maternal exchange of multipotent stem/progenitor cells: microchimerism in diagnosis and disease

The biological concept of microchimerism, the bidirectional trafficking and stable long-term persistence of small numbers of allogeneic (fetal and maternal) cells in a genetically different organ, has gained considerable attention. Microchimerism is a common phenomenon in many species, including humans, and microchimeric cells can modify immunological recognition or tolerance, affect the course and outcome of various diseases and demonstrate stem cell-like or regenerative potential. Here, we review current knowledge of the biology of microchimerism and show how long-term allogeneic co-existence within an organism can impact on existing paradigms in chronic disease, cancer biology, regenerative medicine and fetal-maternal immunology. We discuss diagnostic challenges, clinical applications and future research directions in this exciting and rapidly emerging field of allogeneic fetal-maternal cell exchange.

Epsilon haemoglobin specific antibodies with applications in noninvasive prenatal diagnosis

Invasive procedures for prenatal diagnosis are associated with increased risk of abortion; thus, development of noninvasive procedures would be beneficial. Based on the observation that embryonic nucleated red blood cell (NRBC) crosses the placenta and enters the circulation of pregnant women, the ability to identify such cell would allow development of such procedures. Identification of NRBCs in blood samples would be possible provided that specific antibodies are available. Here we have isolated recombinant antibodies using phage display. From the panel of antibody fragments specifically recognising epsilon-Hb, one was chosen for further characterization, DAb1. DAb1 binds to epsilon-Hb both in Western blots and immunocytochemistry. Several epsilon-Hb positive cells were detected in a blood sample taken as postchorionic villus sampling (CVS). To evaluate the sensitivity of the method, K562 cells (which express epsilon-Hb) were spiked in a blood sample followed by staining in solution and FACS analysis.

Noninvasive prenatal diagnosis of aneuploidy using cell-free nucleic acids in maternal blood: promises and unanswered questions

The discovery of cell-free fetal (cff) DNA and RNA in the maternal circulation has driven developments in noninvasive prenatal diagnosis (NIPD) for the past decade. Detection of paternally derived alleles in cff DNA is becoming well established. Now much interest is focussing on NIPD of fetal chromosomal abnormalities, such as trisomy 21, which is a considerable challenge because this demands accurate quantitative measurements of the amounts of specific cff DNA or cff RNA sequences in maternal blood samples. Emerging strategies for distinguishing and quantifying the fetal nucleic acids in the maternal circulation promise continued development of the field, and pose a number of unanswered questions.

High frequency of fetal cells within a primitive stem cell population in maternal blood

BACKGROUND

During pregnancy, fetal cells enter the maternal bloodstream resulting in fetal cell microchimerism. The fetal cells persist in the mother for decades and colonize a variety of maternal organs. They are associated with maternal autoimmune diseases and may also participate in tissue repair. The identity of the microchimeric cells is not certain but they must be able to persist long-term and have potential for multitissue differentiation.

METHODS AND RESULTS

Here we tested the hypothesis that the fetal microchimeric cells are primitive stem cells, represented by CD34+ adherent cells, which have a wide potential for differentiation. We isolated these stem cells from the blood of pregnant females (n = 25) and detected fetal cells of the correct gender, using fluorescence in situ hybridization, in a high proportion (71% male fetuses and 90% female fetuses; false positive rate 11%, false negative rate 29%) of cases. By RT-PCR, we demonstrated that the cells express Oct-4, Nanog and Rex-1. No fetal cells were detected in the mononuclear or total CD34+ cell populations but high frequencies (mean 11.8%) of fetal cells were detected in the adherent CD34+ cell population.

CONCLUSIONS

These results identify adherent CD34+ stem cells as candidate fetal microchimeric cells, which are capable of sustaining the fetal cell population in the long term and have the ability to colonize multiple tissues and organs.

Candidate epigenetic biomarkers for non-invasive prenatal diagnosis of Down syndrome

This report describes the first identification and characterization of three chromosome-21-specific DNA sequences (and reference sequences from other chromosomes) that are differentially methylated between peripheral blood and placental tissue, with the aim of providing epigenetic biomarkers for quantifying cell-free fetal DNA in maternal plasma. To select sequences to be screened for differential methylation, three strategies were adopted: (i) investigating promoters of highly differentially expressed genes; (ii) choosing 'random' promoter regions; and (iii) choosing 'random' non-promoter regions. Over 200 pre-selected DNA sequences were screened using a methylation-specific restriction enzyme assay. Differentially methylated sequences located at 21q22.3 (AIRE, SIM2 and ERG genes), 1q32.1 (CD48 gene and FAIM3 gene), 2p14 (ARHGAP25 gene) and 12q24 (SELPLG gene) were identified. Bisulphite conversion confirmed that CpG sites within the AIRE promoter region are highly differentially methylated, and optimized methylation-specific primers for this region that are highly specific for placental DNA were devised. Next, it was shown that the methylation status of chorionic villus sample DNA from first trimester pregnancies matched the hypermethylated state of term placenta. Thus there is no indication of a difference in methylation status between early and term pregnancy for the sequences tested. The identified sequences constitute candidate biomarkers for non-invasive prenatal diagnosis of Down syndrome.

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.

Medical legal issues in prenatal diagnosis

The capacity to diagnose fetal disease or abnormality continues to grow, especially in the genetic definition of the fetus. With this growth have come claims of medical malpractice that have mostly centered on a failure of informed consent. Failure may occur by omission or failed communication of pertinent information to the parents or by alleged error in the interpretation of diagnostic information. The usual claim against a physician or other provider is not that of causing damage or disease in the fetus but of causing a loss of opportunity to prevent conception or live birth of an infant who has an abnormality. Successful suits for "wrongful birth," brought by parents of an abnormal child, are common in many United States jurisdictions, but suits for "wrongful life," brought on behalf of the child, have usually been denied.