Thymic and extrathymic Aire-expressing cells in maternal-fetal tolerance

Healthy pregnancy requires maternal immune tolerance to both fetal and placental tissues which contain a range of self- and non-self-antigens. While many of the components and mechanisms of maternal-fetal tolerance have been investigated in detail and previously and thoroughly reviewed (Erlebacher A. Annu Rev Immunol. 2013;31:387-411), the role of autoimmune regulator (Aire), a critical regulator of central tolerance expressed by medullary thymic epithelial cells (mTECs), has been less explored. Aire is known to facilitate the expression of a range of otherwise tissue-specific antigens (TSAs) in mTECs, and here we highlight recent work showing a role for mTEC-mediated thymic selection in maintaining maternal-fetal tolerance. Recently, however, our group and others have identified additional populations of extrathymic Aire-expressing cells (eTACs) in the secondary lymphoid organs. These hematopoietic antigen-presenting cells possess the ability to induce functional inactivation and/or deletion of cognate T cells, and deletion of maternal eTACs during pregnancy increases T-cell activation in the lymph nodes and lymphocytic infiltration of the uterus, leading to pregnancy complications including intrauterine growth restriction (IUGR) and fetal resorption. In this review, we briefly summarize findings related to essential Aire biology, discuss the known roles of Aire-deficiency related to pregnancy complications and infertility, review the newly discovered role for eTACs in the maintenance of maternal-fetal tolerance-as well as recent work defining eTACs at the single-cell level-and postulate potential mechanisms by which eTACs may regulate this process.

Detection of microbial cell-free DNA in maternal and umbilical cord plasma in patients with chorioamnionitis using next generation sequencing

Background

Chorioamnionitis has been linked to spontaneous preterm labor and complications such as neonatal sepsis. We hypothesized that microbial cell-free (cf) DNA would be detectable in maternal plasma in patients with chorioamnionitis and could be the basis for a non-invasive method to detect fetal exposure to microorganisms.

Objective

The purpose of this study was to determine whether next generation sequencing could detect microbial cfDNA in maternal plasma in patients with chorioamnionitis.

Study design

Maternal plasma (n = 94) and umbilical cord plasma (n = 120) were collected during delivery at gestational age 28–41 weeks. cfDNA was extracted and sequenced. Umbilical cord plasma samples with evidence of contamination were excluded. The prevalence of microorganisms previously implicated in choriomanionitis, neonatal sepsis and intra-amniotic infections, as described in the literature, were examined to determine if there was enrichment of these microorganisms in this cohort. Specific microbial cfDNA associated with chorioamnionitis was first detected in umbilical cord plasma and confirmed in the matched maternal plasma samples (n = 77 matched pairs) among 14 cases of histologically confirmed chorioamnionitis and one case of clinical chorioamnionitis; 63 paired samples were used as controls. A correlation of rank of a given microorganism across maternal plasma and matched umbilical cord plasma was used to assess whether signals found in umbilical cord plasma were also present in maternal plasma.

Results

Microbial DNA sequences associated with clinical and/or histological chorioamnionitis were enriched in maternal plasma in cases with suspected chorioamnionitis when compared to controls (12/14 microorganisms, p = 0.02). Analysis of the microbial cfDNA in umbilical cord plasma among the 1,251 microorganisms detectable with this assay identified Streptococcus mitis, Ureaplasma spp., and Mycoplasma spp. in cases of suspected chorioamnionitis. This assay also detected cfDNA from Lactobacillus spp. in controls. Comparison between maternal plasma and umbilical cord plasma confirmed these signatures were also present in maternal plasma. Unbiased analysis of microorganisms with significantly correlated signal between matched maternal plasma and umbilical cord plasma identified the above listed 3 microorganisms, all of which have previously been implicated in patients with chorioamnionitis (Mycoplasma hominis p = 0.0001; Ureaplasma parvum p = 0.002; Streptococcus mitis p = 0.007). These data show that the pathogen signal relevant for chorioamnionitis can be identified in both maternal and umbilical cord plasma.

Conclusion

This is the first report showing the detection of relevant microbial cell-free cfDNA in maternal plasma and umbilical cord plasma in patients with clinical and/or histological chorioamnionitis. These results may lead to the development of a specific assay to detect perinatal infections for targeted therapy to reduce early neonatal sepsis complications.

The maternal immune response inhibits the success of in utero hematopoietic cell transplantation

In utero hematopoietic cell transplantation (IUHCTx) is a promising strategy for the treatment of congenital stem cell disorders. Despite the purported immaturity of the fetal immune system, the clinical success of this strategy has been limited by poor engraftment of transplanted cells. The fetal host immune system is thought to be the major barrier to achieving successful IUHCTx. Since the fetal immune system is immature, however, we hypothesized that the maternal immune response may instead pose the true barrier to IUHCTx. We have demonstrated that maternal T cells traffic into the fetus after allogeneic in utero transplantation and that these lymphocytes play a critical role in limiting engraftment. Furthermore, we have shown that MHC matching the donor cells to the mother improves engraftment in the unmatched fetus. These results help renew interest in using the fetal environment to treat patients with congenital stem cell disorders.

Advances in Fetal Surgery

Advances in prenatal screening and diagnosis, combined with an understanding of the pathophysiology of congenital anomalies, have brought incredible impetus to the field of fetal surgery. Identification of fetal anomalies can lead to counseling of the affected family so that informed decisions can be made on how to proceed with the pregnancy. Counseling may lead to pregnancy termination, changes in the timing or mode of delivery, and, in select cases, prenatal intervention. Open fetal surgery may be considered in severe cases of congenital diaphragmatic hernia, congenital chest lesions, sacrococcygeal teratoma, urinary tract obstruction, and myelomeningocele. The ex utero intrapartum treatment procedure may be lifesaving for fetuses with giant neck masses. Finally, fetoscopic surgery may be offered for select cases of twin-twin transfusion syndrome and twin reversed arterial perfusion sequence. Fetal intervention in all of these cases depends on a team approach to the patient and on the objective comparison of outcomes with and without fetal therapy. In the future, further understanding of the genetic basis of congenital diseases may enable minimally invasive treatments such as stem cell transplantation or gene therapy.

Favorable outcomes after in utero transfusion in fetuses with alpha thalassemia major: a case series and review of the literature

OBJECTIVE

Alpha thalassemia major (ATM) is often fatal in utero due to severe hydrops fetalis. Although in utero transfusions (IUTs) are increasingly used to allow fetal survival in ATM, prenatal and postnatal outcomes are not well described.

METHODS

We retrospectively reviewed cases of ATM at our institution treated with consecutive IUT. Clinical records were reviewed for transfusion history, neurodevelopmental outcomes, anatomic abnormalities, survival to hematopoietic cell transplantation, and transfusion independence. A systematic review was performed, and additional reported cases are discussed.

RESULTS

Three patients who underwent IUT for ATM were identified, and review of the literature revealed 17 reported cases. Of patients who received IUT, reported neurodevelopmental deficits occurred in 29% (4/14) and anatomic abnormalities in 55% (11/20). Four patients eventually underwent successful hematopoietic cell transplantation. Transfusion volumes were less than suggested guidelines for other causes of fetal anemia in 91.7% of the transfusions.

CONCLUSION

This series demonstrates the potential for achieving full fetal development with normal neurologic outcomes in those affected by ATM. It provides support for continued patient and provider education about current benefits and risks of active prenatal therapy for fetuses with ATM, as well as continued research to optimize therapeutic strategies such as in utero transplantation. © 2016 John Wiley & Sons, Ltd.

Hepatic portocholecystostomy for biliary atresia: a 25-year follow-up and review

We report the successful salvage of a patient's native liver 25 years after hepatic portocholecystostomy for biliary atresia. Our case demonstrates the effectiveness of biliary specific, high-resolution CT imaging in the diagnosis of, and operative planning for complex cases of biliary obstruction. We also report the longest-term pathologic follow-up of biliary atresia after hepatic portocholecystostomy. Life-long follow-up of patients with biliary atresia is important to prevent life-threatening complications of biliary stasis/obstruction.

A mouse model of in utero transplantation

The transplantation of stem cells and viruses in utero has tremendous potential for treating congenital disorders in the human fetus. For example, in utero transplantation (IUT) of hematopoietic stem cells has been used to successfully treat patients with severe combined immunodeficiency. In several other conditions, however, IUT has been attempted without success. Given these mixed results, the availability of an efficient non-human model to study the biological sequelae of stem cell transplantation and gene therapy is critical to advance this field. We and others have used the mouse model of IUT to study factors affecting successful engraftment of in utero transplanted hematopoietic stem cells in both wild-type mice and those with genetic diseases. The fetal environment also offers considerable advantages for the success of in utero gene therapy. For example, the delivery of adenoviral, adeno-associated viral, retroviral, and lentiviral vectors into the fetus has resulted in the transduction of multiple organs distant from the site of injection with long-term gene expression. in utero gene therapy may therefore be considered as a possible treatment strategy for single gene disorders such as muscular dystrophy or cystic fibrosis. Another potential advantage of IUT is the ability to induce immune tolerance to a specific antigen. As seen in mice with hemophilia, the introduction of Factor IX early in development results in tolerance to this protein. In addition to its use in investigating potential human therapies, the mouse model of IUT can be a powerful tool to study basic questions in developmental and stem cell biology. For example, one can deliver various small molecules to induce or inhibit specific gene expression at defined gestational stages and manipulate developmental pathways. The impact of these alterations can be assessed at various timepoints after the initial transplantation. Furthermore, one can transplant pluripotent or lineage specific progenitor cells into the fetal environment to study stem cell differentiation in a non-irradiated and unperturbed host environment. The mouse model of IUT has already provided numerous insights within the fields of immunology, and developmental and stem cell biology. In this video-based protocol, we describe a step-by-step approach to performing IUT in mouse fetuses and outline the critical steps and potential pitfalls of this technique.

Persistent expression of hF.IX After tolerance induction by in utero or neonatal administration of AAV-1-F.IX in hemophilia B mice

The major complication associated with protein replacement therapy currently used in the treatment of hemophilia B (HB) is the development of antibodies to the infused human Factor IX (hF.IX). We hypothesized that vector-mediated expression of hF.IX, either at a prenatal stage or early in life may lead to tolerance to hF.IX and long-term transgene expression. Fetal, neonatal, and adult F.IX-deficient mice were injected with AAV-1-hF.IX, and the hF.IX levels as well as antibodies to hF.IX in the circulation were assayed. In utero injection followed by postnatal re-administration of adeno-associated virus 1 (AAV-1) vector achieved persistent expression of hF.IX in all animals, with no cellular or humoral immune response to F.IX. Similar results were seen after initial injection in neonatal mice followed by re-administration, whereas all mice injected at the adult stage developed antibodies to hF.IX. In contrast, after administration of AAV-2-hF.IX in the neonatal period, antibodies to hF.IX were formed in all the injected animals. We conclude that in utero or neonatal-stage injection of AAV-1-hF.IX can lead to long-term expression and absence of immune response. The differences in immune response between the AAV-1 and AAV-2 groups suggests that tolerance may be related to differences in bio-distribution, timing of expression, and/or the initial levels of hF.IX expression. This supports the concept of a narrow "window of opportunity" for tolerance induction.

Impact of Continuous Intraoperative Monitoring on Outcomes in Open Fetal Surgery

OBJECTIVES

There are shifts in fetal hemodynamics during open fetal surgery that were not appreciated until the use of intraoperative fetal echocardiography. We have developed an intraoperative monitoring strategy to continuously assess fetal hemodynamics. We hypothesized that this approach would enhance intraoperative management and survival.

METHODS

Medical records of open fetal surgery patients were reviewed since the implementation of this approach. Intraoperative fetal monitoring was accomplished by continuous echocardiography, pulse oximetry, establishment of intravenous access, and arterial blood gas and hemoglobin measurement. Overall survival was compared to fetal surgeries performed prior implementation of this monitoring strategy.

RESULTS

Resections of a congenital cystic adenomatoid malformation or a sacrococcygeal teratoma in nine hydropic fetuses were performed while using this monitoring strategy. Intraoperative echocardiography resulted in a change of management in 7 of 9 fetuses. The main observations on fetal echocardiography resulting in intraoperative intervention were decreased ventricular filling, bradycardia, and decreased ventricular contractility. Therapy included administration of volume expanders and/or inotropic agents. Overall fetal survival was 78% compared to a survival of 42% prior to the implementation of this approach.

CONCLUSION

Continuous intraoperative fetal monitoring provides real time assessment of fetal hemodynamics which results in changes in intraoperative management. The overall outcomes in these critically ill fetuses have been improved.

Multilineage differentiation of human MSC after in utero transplantation

Prenatal transplantation of stem cells is an exciting frontier for the treatment of many congenital diseases. The fetus may be an ideal recipient for stem cells, as it is immunologically immature and has rapidly proliferating cellular compartments that may support the engraftment of transplanted cells. Mesenchymal stem cells (MSC), given their ability to differentiate among multiple lineages, could potentially be used to treat diseases such as osteogenesis imperfecta, muscular dystrophy, and a variety of others that can be diagnosed in utero. We have shown, using a human-sheep in utero xenotransplantation model, that human MSC have the ability to engraft, differentiate into many tissue types, and survive for over 1 year in fetal lamb recipients. This observation warrants further studies of the behavior of MSC following systemic or site-directed transplantation.

Engraftment of bone marrow and fetal liver cells after in utero transplantation in MDX mice

BACKGROUND/PURPOSE

In utero hematopoietic stem cell transplantation (IUHSCTx) has been experimentally or clinically effective only in circumstances in which there is a survival advantage for donor cells. A survival advantage exists for normal muscle cells in muscular dystrophy. Because hematopoietic and mesenchymal stem cells may have the capacity to differentiate into muscle cells, the authors hypothesized that in utero bone marrow (BM) or fetal liver (FL) stem cell transplantation may be used to treat muscular dystrophy.

METHODS

Time-dated 14-day-gestation fetal muscular dystrophy mice (mdx) were injected intraperitoneally with 1 to 5 x 10(6) BM or FL cells per fetus from Rosa26 donor mice (transgenic for lacZ). Four weeks after birth, peripheral blood from the pups was analyzed for hematopoietic chimerism by using fluorescence-activated cell sorting (FACS) for the Ly-9.1 marker. Chimeric mice (6 BM and 2 FL recipients) were sacrificed at 12 to 14 months of age, muscles were stained with X-gal, and analyzed by 1- to 2-microm plastic sections. Polymerase chain reaction (PCR) for lacZ was performed in other organs to determine systemic engraftment.

RESULTS

At the time of death, all animals that were chimeric at 4 weeks continued to show hematopoietic chimerism of 0.2% to 9% by FACS. Engrafted donor cells were found in multiple sections from hindlimb skeletal muscles, diaphragms, and hearts from both BM and FL recipients. These cells had incorporated into the host muscles, and their morphology was consistent with myogenic differentiation. PCR of BM, liver, spleen, thymus, kidney, and lung for lacZ was positive in multiple animals.

CONCLUSIONS

IUHSCTx leads to widespread engraftment of donor cells in multiple muscle compartments of hematopoietic chimeras. The advantage for normal myocytes offered in the mdx model allows engraftment and myogenic differentiation of transplanted BM or FL cells by morphology at a relatively higher frequency in muscle relative to other tissues, without the need for host conditioning. Because muscular dystrophy now can be detected early in gestation, such a strategy may offer a future alternative in the clinical treatment of this disease.

The natural history of prenatally diagnosed conjoined twins

BACKGROUND/PURPOSE

Accurate prenatal diagnosis of complex anatomic connections and associated anomalies has only been possible recently with the use of ultrasonography, echocardiography, and fetal magnetic resonance imaging (MRI). To assess the impact of improved antenatal diagnosis in the management and outcome of conjoined twins, the authors reviewed their experience with 14 cases.

METHODS

A retrospective review of prenatally diagnosed conjoined twins referred to our institution from 1996 to present was conducted.

RESULTS

In 14 sets of conjoined twins, there were 10 thoracoomphalopagus, 2 dicephalus tribrachius dipus, 1 ischiopagus, and 1 ischioomphalopagus. The earliest age at diagnosis was 9 weeks' gestation (range, 9 to 29; mean, 20). Prenatal imaging with ultrasonography, echocardiography, and ultrafast fetal MRI accurately defined the shared anatomy in all cases. Associated anomalies included cardiac malformations (11 of 14), congenital diaphragmatic hernia (4 of 14), abdominal wall defects (2 of 14), and imperforate anus (2 of 14). Three sets of twins underwent therapeutic abortion, 1 set of twins died in utero, and 10 were delivered via cesarean section at a mean gestational age of 34 weeks. There were 5 individual survivors in the series after separation (18%). In one case, in which a twin with a normal heart perfused the cotwin with a rudimentary heart, the ex utero intrapartum treatment procedure (EXIT) was utilized because of concern that the normal twin would suffer immediate cardiac decompensation at birth. This EXIT-to-separation strategy allowed prompt control of the airway and circulation before clamping the umbilical cord and optimized control over a potentially emergent situation, leading to survival of the normal cotwin. In 2 sets of twins in which each twin had a normal heart, tissue expanders were inserted before separation.

CONCLUSIONS

Advances in prenatal diagnosis allow detailed, accurate evaluations of conjoined twins. Careful prenatal studies may uncover cases in which emergent separation at birth is lifesaving.

The management of prenatally diagnosed choledochal cysts

BACKGROUND

Although congenital biliary tree abnormalities are uncommon in the United States, more are being diagnosed antenatally with improved imaging techniques.

METHODS

To determine the prognosis of prenatally diagnosed biliary disease, the authors reviewed the treatment of 3 children who had biliary cystic lesions found during routine prenatal ultrasonography.

RESULTS

All 3 children were born at term. They had elevated bilirubin levels, and postnatal ultrasound scans confirmed the presence of a biliary cystic mass. They underwent exploration within 2 weeks of life. At operation, 2 children were found to have biliary atresia with a cystic biliary lesion. They underwent Kasai procedures and are doing well at 5 and 9 months of age. The third child was found to have a type I choledochal cyst and malrotation at exploration. He underwent cystectomy with Roux-en-Y hepaticojejunostomy and a Ladd's procedure and is doing well at 3 years of age.

CONCLUSIONS

Prenatally diagnosed biliary cysts represent a different spectrum of disease than those diagnosed later in life. The sequelae of biliary disease start before birth, and early operation may be necessary to achieve a good outcome. Because it is impossible to distinguish between choledochal cysts and biliary atresia on antenatal ultrasound scan or magnetic resonance imaging, children with presumed choledochal cysts should undergo early exploration to rule out potential biliary atresia. Excellent outcome is possible with early operation in the absence of severe associated anomalies.

Human mesenchymal stem cells persist, demonstrate site-specific multipotential differentiation, and are present in sites of wound healing and tissue regeneration after transplantation into fetal sheep

Prenatal transplantation of stem cells is an exciting frontier for the treatment of many congenital diseases. The fetus may be an ideal recipient for stem cells, as it is immunologically immature and has rapidly proliferating cellular compartments that may support the engraftment of transplanted cells. Mesenchymal stem cells (MSC), given their ability to differentiate into multiple cell types, could potentially be used to treat diseases such as osteogenesis imperfecta, muscular dystrophy, and other mesenchymal disorders that can be diagnosed in utero. We have shown, using a human-sheep in utero xenotransplantation model, that human MSC have the ability to engraft, undergo site-specific differentiation into multiple cell types, and survive for more than 1 year in fetal lamb recipients. In addition, in this model MSC-derived cells appear to be present in increased numbers in wounded or regenerating tissues. This observation warrants further studies of the biology of MSCs following systemic or site-directed transplantation.