Amniotic fluid stem cells and fetal cell microchimerism

Multipotent fetal stem cells in reproductive biology research

Due to the limited accessibility of the in vivo situation, the scarcity of the human tissue, legal constraints, and ethical considerations, the underlying molecular mechanisms of disorders, such as preeclampsia, the pathological consequences of fetomaternal microchimerism, or infertility, are still not fully understood. And although substantial progress has already been made, the therapeutic strategies for reproductive system diseases are still facing limitations. In the recent years, it became more and more evident that stem cells are powerful tools for basic research in human reproduction and stem cell-based approaches moved into the center of endeavors to establish new clinical concepts. Multipotent fetal stem cells derived from the amniotic fluid, amniotic membrane, chorion leave, Wharton´s jelly, or placenta came to the fore because they are easy to acquire, are not associated with ethical concerns or covered by strict legal restrictions, and can be banked for autologous utilization later in life. Compared to adult stem cells, they exhibit a significantly higher differentiation potential and are much easier to propagate in vitro. Compared to pluripotent stem cells, they harbor less mutations, are not tumorigenic, and exhibit low immunogenicity. Studies on multipotent fetal stem cells can be invaluable to gain knowledge on the development of dysfunctional fetal cell types, to characterize the fetal stem cells migrating into the body of a pregnant woman in the context of fetomaternal microchimerism, and to obtain a more comprehensive picture of germ cell development in the course of in vitro differentiation experiments. The in vivo transplantation of fetal stem cells or their paracrine factors can mediate therapeutic effects in preeclampsia and can restore reproductive organ functions. Together with the use of fetal stem cell-derived gametes, such strategies could once help individuals, who do not develop functional gametes, to conceive genetically related children. Although there is still a long way to go, these developments regarding the usage of multipotent fetal stem cells in the clinic should continuously be accompanied by a wide and detailed ethical discussion.

ceAF Ameliorates Diabetic Wound Healing by Alleviating Inflammation and Oxidative Stress via TLR4/NF-κB and Nrf2 Pathways

Background. With the rise in diabetes incidence, diabetic foot ulcers have become the most common clinically chronic refractory wounds. Persistent chronic inflammation is a typical feature of diabetic cutaneous wounds, and diabetic wound healing can be improved by alleviating inflammation and oxidative stress. Chick early amniotic fluids (ceAF) consist of native conglutinant substances with balanced amounts of growth factors, cytokines, and chemokines. However, whether ceAF modulates inflammation and oxidative stress and thus promotes diabetic wound healing remains unknown. Materials and Methods. RAW264.7 cells were categorized into four groups: negative control, LPS, LPS + ceAF, and ceAF. 10% of ceAF was selected to treat different groups of mice with a full-thickness skin defect wound. Then, RT-qPCR, western blot, immunofluorescence, and other assays were carried out to explore the effect of ceAF on wound healing and its molecular mechanism. Results. Topical administration of ceAF improved M2 macrophage polarization and inflammatory response in the wound tissues, thereby ameliorating delayed wound healing. Histological improvement could be observed in the grade of inflammation, collagen deposition, and neovascularization in wound edge tissues. ceAF also increased M2 macrophage-specific markers expression and exogenous ceAF suppressed LPS-induced cellular inflammatory response in vitro high glucose environment. Additionally, ceAF could activate TLR4/NF-κB and Nrf2 signal transductions to promote M2 macrophage polarization in vitro. Conclusions. In summary, ceAF downregulates inflammatory response, regulates M2 macrophage transition via TLR4/NF-κB and Nrf2 signaling pathways, and thus improves diabetic wound healing.

Amniotic Fluid Stem Cells: What They Are and What They Can Become

In the last two decades, fetal amniotic fluid stem cells progressively attracted attention in the context of both basic research and the development of innovative therapeutic concepts. They exhibit broadly multipotent plasticity with the ability to differentiate into cells of all three embryonic germ layers and low immunogenicity. They are convenient to maintain, highly proliferative, genomically stable, non-tumorigenic, perfectly amenable to genetic modifications, and do not raise ethical concerns. However, it is important to note that among the various fetal amniotic fluid cells, only c-Kit+ amniotic fluid stem cells represent a distinct entity showing the full spectrum of these features. Since amniotic fluid additionally contains numerous terminally differentiated cells and progenitor cells with more limited differentiation potentials, it is of highest relevance to always precisely describe the isolation procedure and characteristics of the used amniotic fluid-derived cell type. It is of obvious interest for scientists, clinicians, and patients alike to be able to rely on up-todate and concisely separated pictures of the utilities as well as the limitations of terminally differentiated amniotic fluid cells, amniotic fluid-derived progenitor cells, and c-Kit+ amniotic fluid stem cells, to drive these distinct cellular models towards as many individual clinical applications as possible.

Amniotic fluid stem cells and the cell source repertoire for non-invasive prenatal testing

Cell-free fetal DNA (cffDNA)-based non-invasive prenatal testing (NIPT) is considered to be a very promising screening tool for pregnant women with an increased risk of fetal aneuploidy. Already millions of women worldwide underwent NIPT. However, due to the observed false-positive and false-negative results, this screening approach does not fulfil the criteria of a diagnostic test. Accordingly, positive results still require risk-carrying invasive prenatal testing, such as amniocentesis or chorionic villus sampling (CVS), for confirmation. Such hurdles need to be overcome before NIPT could become a diagnostic approach widely used in the general population. Here we discuss new evidence that besides the placenta amniotic fluid stem cells (AFSCs) could also represent an origin of cffDNA in the mother’s blood. A comprehensive picture of the involved cell source repertoire could pave the way to more reliable interpretations of NIPT results and ameliorate counselling of advice-seeking patients.

Three-dimensional migration of human amniotic fluid stem cells involves mesenchymal and amoeboid modes and is regulated by mTORC1

Three‐dimensional (3D) cell migration is an integral part of many physiologic processes. Although being well studied in the context of adult tissue homeostasis and cancer development, remarkably little is known about the invasive behavior of human stem cells. Using two different kinds of invasion assays, this study aimed at investigating and characterizing the 3D migratory capacity of human amniotic fluid stem cells (hAFSCs), a well‐established fetal stem cell type. Eight hAFSC lines were found to harbor pronounced potential to penetrate basement membrane (BM)‐like matrices. Morphological examination and inhibitor approaches revealed that 3D migration of hAFSCs involves both the matrix metalloprotease‐dependent mesenchymal, elongated mode and the Rho‐associated protein kinase‐dependent amoeboid, round mode. Moreover, hAFSCs could be shown to harbor transendothelial migration capacity and to exhibit a motility‐associated marker expression pattern. Finally, the potential to cross extracellular matrix was found to be induced by mTORC1‐activating growth factors and reduced by blocking mTORC1 activity. Taken together, this report provides the first demonstration that human stem cells exhibit mTORC1‐dependent invasive capacity and can concurrently make use of mesenchymal and amoeboid 3D cell migration modes, which represents an important step toward the full biological characterization of fetal human stem cells with relevance to both developmental research and stem cell‐based therapy.

Fetomaternal microchimerism and genetic diagnosis: On the origins of fetal cells and cell-free fetal DNA in the pregnant woman

During pregnancy several types of fetal cells and fetal stem cells, including pregnancy-associated progenitor cells (PAPCs), traffic into the maternal circulation. Whereas they also migrate to various maternal organs and adopt the phenotype of the target tissues to contribute to regenerative processes, fetal cells also play a role in the pathogenesis of maternal diseases. In addition, cell-free fetal DNA (cffDNA) is detectable in the plasma of pregnant women. Together they constitute the well-known phenomenon of fetomaternal microchimerism, which inspired the concept of non-invasive prenatal testing (NIPT) using maternal blood. An in-depth knowledge concerning the origins of these fetal cells and cffDNA allows a more comprehensive understanding of the biological relevance of fetomaternal microchimerism and has implications for the ongoing expansion of resultant clinical applications.

Protective effect of GDNF-engineered amniotic fluid-derived stem cells on the renal ischaemia reperfusion injury in vitro

OBJECTIVES

Amniotic fluid-derived stem cells (AFSCs) possessing multilineage differentiation potential are proposed as a novel and accessible source for cell-based therapy and tissue regeneration. Glial-derived neurotrophic factor (GDNF) has been hypothesized to promote the therapeutic effect of AFSCs on markedly ameliorating renal dysfunction. The aim of this study was to investigate whether AFSCs equipped with GDNF (GDNF-AFSCs) had capabilities of attenuating mouse renal tubular epithelial cells (mRTECs) apoptosis and evaluate its potential mechanisms.

MATERIALS AND METHODS

A hypoxia-reoxygenation (H/R) model of the mRTECs was established. Injured mRTECs were co-cultured with GDNF-AFSCs in a transwell system. The mRNA expressions of hepatocytes growth factor (HGF) and fibroblast growth factor (bFGF) were detected by qRT-PCR. Changes of intracelluar reactive oxygen species (ROS) and the level of superoxide dismutase (SOD) and malondialdehyde (MDA) were examined. The expressions of nitrotyrosine, Gp91-phox, Bax, and Bcl-2 were determined by Western blotting. Cell apoptosis was assayed by flow cytometry, and caspase-3 activity was monitored by caspase-3 activity assay kit.

RESULTS

Our study revealed that expression of growth factors was increased and oxidative stress was dramatically counteracted in GDNF-AFSCs-treated group. Furthermore, apoptosis induced by H/R injury was inhibited in mRTECs by GDNF-AFSCs.

CONCLUSIONS

These data indicated that GDNF-AFSCs are beneficial to repairing damaged mRTECs significantly in vitro, which suggests GDNF-AFSCs provide new hopes of innovative interventions in different kidney disease.

Towards a Bioengineered Kidney: Recellularization Strategies for Decellularized Native Kidney Scaffolds

Patients with end-stage renal disease often undergo dialysis as a partial substitute for kidney function while waiting for their only treatment option: a kidney transplant. Several research directions emerged for alternatives in support of the ever-growing numbers of patients. Recent years brought big steps forward in the field, with researchers questioning and improving the current dialysis devices as well as moving towards the design of a bioengineered kidney. Whole-organ engineering is also being explored as a possibility, making use of animal or human kidney scaffolds for engineering a transplantable organ. While this is not a new strategy, having been applied so far for thin tissues, it is a novel approach for complex organs such as the kidneys. Kidneys can be decellularized and the remaining scaffold consisting of an extracellular matrix can be repopulated with (autologous) cells, aiming at growing ex vivo a fully transplantable organ. In a broader view, such organs might also be used for a better understanding of fundamental biological concepts and disease mechanisms, drug screening and toxicological investigations, opening new pathways in the treatment of kidney disease.

Decellularization of whole organs has been widely explored and described; therefore, this manuscript only briefly reviews some important considerations with an emphasis on scaffold decontamination, but focuses further on recellularization strategies. Critical aspects, including cell types and sources that can be used for recellularization, seeding strategies and possible applications beyond renal replacement are discussed.

Massively Parallel Sequencing (MPS) of Cell-Free Fetal DNA (cffDNA) for Trisomies 21, 18, and 13 in Twin Pregnancies

Massively parallel sequencing (MPS) technology has become increasingly available and has been widely used to screen for trisomies 21, 18, and 13 in singleton pregnancies. This study assessed the performance of MPS testing of cell-free fetal DNA (cffDNA) from maternal plasma for trisomies 21, 18, and 13 in twin pregnancies. Ninety-two women with twin pregnancies were recruited. The results were identified through karyotypes of amniocentesis or clinical examination and follow-up of the neonates. Fluorescent in-situ hybridization was used to examine the placentas postnatally in cases of false-positive results. The fetuses with autosomal trisomy 21 (n = 2) and trisomy 15 (n = 1) were successfully detected via MPS testing of cffDNA. There was one false-positive for trisomy 13 (n = 1), and fluorescence in-situ hybridization (FISH) identified confined placental mosaicism in this case. For twin pregnancies undergoing second-trimester screening for trisomy, MPS testing of cffDNA is feasible and can enhance the diagnostic spectrum of non-invasive prenatal testing, which could effectively reduce invasive prenatal diagnostic methods. In addition to screening for trisomy 21, 18, and 13 by cffDNA, MPS can detect fetal additional autosomal trisomy. False-positive results cannot completely exclude confined placental mosaicism.

The Isolation and Production of the Ready-to-Use Product (the Amniotic Stem Cell Culture) in Accordance with Good Manufacturing Practice Regulations

According to the Committee for Advanced Therapies, amniotic stem cells were classified as an advanced therapy medicinal product. This work aims to standardize the isolation of amniotic stem cells and the selection of the optimal time of transplantation and cell application methods in burn patients according to the guidelines of the Good Manufacturing Practice. The placenta used in the study was sourced during a Cesarean section. The remnants of the amnion preparation were placed in a sterile container and transferred to a class B environment, where the primary cultures began. The highest average number of cells was obtained by tissue homogenization and culture growth on the AmnioGrow medium. The isolation of the pure monoculture should be performed using the antibodies against CD105. On the basis of an analysis of population doubling, the aging of a population, the cells' viability, and the severity of injury, the cells should be used between passages 3 and 6. Significant differences were found in the number and viability of cells that were transferred as a full sheet, depending on the transfer method. To sum up, amniotic cells are a promising source in the treatment of burns and can be used as a hospital exemption.

Amniotic Epithelial Cells: A New Tool to Combat Aging and Age-Related Diseases?

The number of elderly people is growing at an unprecedented rate and this increase of the aging population is expected to have a direct impact on the incidence of age-related diseases and healthcare-associated costs. Thus, it is imperative that new tools are developed to fight and slow age-related diseases. Regenerative medicine is a promising strategy for the maintenance of health and function late in life; however, stem cell-based therapies face several challenges including rejection and tumor transformation. As an alternative, the placenta offers an extraordinary source of fetal stem cells, including the amniotic epithelial cells (AECs), which retain some of the characteristics of embryonic stem cells, but show low immunogenicity, together with immunomodulatory and anti-inflammatory activities. Because of these characteristics, AECs have been widely utilized in regenerative medicine. This perspective highlights different mechanisms triggered by transplanted AECs that could be potentially useful for anti-aging therapies, which include: Graft and differentiation for tissue regeneration in age-related settings, anti-inflammatory behavior to combat “inflammaging,” anti-tumor activity, direct lifespan and healthspan extension properties, and possibly rejuvenation in a manner reminiscent of heterochronic parabiosis. Here, we critically discuss benefits and limitation of AECs-based therapies in age-related diseases.

Isolation of Human Neural Stem Cells from the Amniotic Fluid with Diagnosed Neural Tube Defects

Human neural stem cells (NSCs) are particularly valuable for the study of neurogenesis process and have a therapeutic potential in treating neurodegenerative disorders. However, current progress in the use of human NSCs is limited due to the available NSC sources and the complicated isolation and culture techniques. In this study, we describe an efficient method to isolate and propagate human NSCs from the amniotic fluid with diagnosed neural tube defects (NTDs), specifically, anencephaly. These amniotic fluid-derived NSCs (AF-NSCs) formed neurospheres and underwent long-term expansion in vitro. In addition, these cells showed normal karyotypes and telomerase activity and expressed NSC-specific markers, including Nestin, Sox2, Musashi-1, and the ATP-binding cassette G2 (ABCG2). AF-NSCs displayed typical morphological patterns and expressed specific markers that were consistent with neurons, astrocytes, oligodendrocytes, and dopaminergic neurons after proper induction conditions. Furthermore, grafted AF-NSCs improved the physiological functions in a rat stroke model. The ability to isolate and bank human NSCs from this novel source provides a unique opportunity for translational studies of neurological disorders.

Intercellular protein expression variability as a feature of stem cell pluripotency

The expression of pluripotent stem cell protein markers, self-renewal, the potential to differentiate in cell types of all three germlines and teratoma formation in nude mice form the spectrum of the stringent pluripotency criteria for human stem cells. Currently, intercellular variability is discussed as an additional putative defining property of pluripotent stem cells. In future, it will be of relevance to clarify the genesis of intercellular variability for each stem cell line/population before its application in basic science or therapy. Furthermore, for a better understanding of stemness it will be indispensable to separately investigate the issue of intercellular variability for each feature of pluripotency.

Need for gender-specific pre-analytical testing: the dark side of the moon in laboratory testing

Many international organisations encourage studies in a sex-gender perspective. However, research with a gender perspective presents a high degree of complexity, and the inclusion of sex-gender variable in experiments presents many methodological questions, the majority of which are still neglected. Overcoming these issues is fundamental to avoid erroneous results. Here, pre-analytical aspects of the research, such as study design, choice of utilised specimens, sample collection and processing, animal models of diseases, and the observer's role, are discussed. Artefacts in this stage of research could affect the predictive value of all analyses. Furthermore, the standardisation of research subjects according to their lifestyles and, if female, to their life phase and menses or oestrous cycle, is urgent to harmonise research worldwide. A sex-gender-specific attention to pre-analytical aspects could produce a decrease in the time for translation from the bench to bedside. Furthermore, sex-gender-specific pre-clinical pharmacological testing will enable adequate assessment of pharmacokinetic and pharmacodynamic actions of drugs and will enable, where appropriate, an adequate gender-specific clinical development plan. Therefore, sex-gender-specific pre-clinical research will increase the gender equity of care and will produce more evidence-based medicine.

Cigarette smoke exposure during pregnancy alters fetomaternal cell trafficking leading to retention of microchimeric cells in the maternal lung

Cigarette smoke exposure causes chronic oxidative lung damage. During pregnancy, fetal microchimeric cells traffic to the mother. Their numbers are increased at the site of acute injury. We hypothesized that milder chronic diffuse smoke injury would attract fetal cells to maternal lungs. We used a green-fluorescent-protein (GFP) mouse model to study the effects of cigarette smoke exposure on fetomaternal cell trafficking. Wild-type female mice were exposed to cigarette smoke for about 4 weeks and bred with homozygote GFP males. Cigarette smoke exposure continued until lungs were harvested and analyzed. Exposure to cigarette smoke led to macrophage accumulation in the maternal lung and significantly lower fetal weights. Cigarette smoke exposure influenced fetomaternal cell trafficking. It was associated with retention of GFP-positive fetal cells in the maternal lung and a significant reduction of fetal cells in maternal livers at gestational day 18, when fetomaternal cell trafficking peaks in the mouse model. Cells quickly clear postpartum, leaving only a few, difficult to detect, persisting microchimeric cells behind. In our study, we confirmed the postpartum clearance of cells in the maternal lungs, with no significant difference in both groups. We conclude that in the mouse model, cigarette smoke exposure during pregnancy leads to a retention of fetal microchimeric cells in the maternal lung, the site of injury. Further studies will be needed to elucidate the effect of cigarette smoke exposure on the phenotypic characteristics and function of these fetal microchimeric cells, and confirm its course in cigarette smoke exposure in humans.

The decision on the "optimal" human pluripotent stem cell

Because of recent advances, the array of human pluripotent stem cells now contains embryonic stem cells, derived from "surplus" in vitro fertilization embryos or from cloned embryos; induced pluripotent stem cells; and amniotic fluid stem cells. Here, we compare these stem cell types regarding ethical and legal concerns, cultivation conditions, genomic stability, tumor developing potentials, and applicability for disease modeling and human therapy. This overview highlights that in the future appropriate methodological management must include a decision on the "optimal" stem cell to use before the specific application.

Circulating fetal cell-free DNA and prenatal molecular diagnostics: are we ready for consensus?

Abstract Circulating fetal cell-free DNA (cffDNA) is emerging as the most reliable known target for prenatal molecular diagnostics. Different points of view are expressed in literature regarding the safe use of cffDNA for all types of molecular tests, above all those used to detect maternal DNA rather than fetal mutation. The aim of the present study was therefore to achieve consensus on guidelines conducive to standardizing current procedures, which differ between laboratories, and to design stringent technical protocols for the analysis of cffDNA.

Placental mosaicism for Trisomy 13: a challenge in providing the cell-free fetal DNA testing

PURPOSE

We investigated the disagreement between the positive cell-free fetal DNA test for trisomy 13 and the standard cytogenetic diagnosis of one case.

METHODS

Cell-free fetal DNA testing was performed by massively parallel sequencing. We used conventional cytogenetic analysis to confirm the commercial cell-free fetal DNA testing. Additionally, postnatal fluorescent in situ hybridization (FISH) testing was performed on placental tissues.

RESULTS

The cell-free fetal DNA testing result was positive for trisomy 13. G-banded analysis of amniotic fluid was normal, 46, XY. FISH testing of tissues from four quadrants of the placenta demonstrated mosaicism for trisomy 13.

CONCLUSIONS

A positive cell-free fetal DNA testing result may not be representative of the fetal karyotype because of placental mosaicism. Cytogenetic analysis should be performed when abnormal cell-free fetal DNA test results are obtained.