Fetal cells in mother rats contribute to the remodeling of liver and kidney after injury

Fetal microchimerism indicates a mixture of cells of maternal and fetal origin seen in maternal tissues during and after pregnancy. Controversy exists about whether persistent fetal microchimerism is related with some autoimmune disorders occurring during and after pregnancy. In the current experiment, an animal model in which EGFP positive cells were taken as fetal-origin cells was designed to detect the fetal microchimerism in various maternal organs. Ethanol drinking and gentamicin injection were adopted to induce liver and kidney injury simultaneously. EGFP positive cells were engrafted not only in the maternal circulation and bone marrow, but also in the liver and kidney as hepatocytes and tubular cells, respectively. These results indicate that fetal cells are engrafted to maternal hematopoietic system without apparent injury and they also contribute to the repairing process of maternal liver and kidney.     

Pre-disease pregnancy complications and systemic sclerosis: pathogenic or pre-clinical?

The fetal microchimerism theory for the pathogenesis of systemic sclerosis (SSc) has compelling biologic support, including the female predominance of the disease, the mean age of onset after childbearing years, similarities between diffuse cutaneous SSc and graft-versus-host disease, as well as the detection of microchimeric cells in peripheral blood and skin of SSc patients. The previous issue of Arthritis Research and Therapy presents findings of a positive association between pregnancy complications and future diagnosis of SSc in parous women. Before interpreting the results of this epidemiologic study as support for fetal microchimerism, however, other theories for the observed associations must be considered.     

Systemic sclerosis: new insights in autoimmunity.

The strong female predilection of systemic sclerosis, especially in women after their childbearing years, and the clinical and histopathological similarities with chronic graft-versus-host disease make systemic sclerosis an interesting subject of debate. Recent studies concerning the pathogenesis of this disease demonstrated the persistence of fetal cells in the maternal circulation in a majority of female patients. How or whether microchimerism is involved in the pathogenesis of systemic sclerosis remains to be elucidated. The present paper reviews the recent findings on the subject.     

Fetal-maternal HLA compatibility confers susceptibility to systemic sclerosis

 Systemic sclerosis (SSc) is a disease of unknown origin, which occurs predominantly in women after childbearing years. There are prominent clinical and histopathologic similarities between SSc and chronic graft-versus-host disease (GVHD). GVHD can occur after blood transfusions or after transplantation with HLA-compatible bone marrow. Here we examined the hypothesis that SSc may be caused by fetal cells crossing the placenta into the maternal circulation and providing donor lymphocytes which recognize disparate HLA antigens, resulting in a reaction similar to chronic GVHD. To test the hypothesis we analyzed the inheritance of HLA class I and class II haplotypes in the families of 37 SSc patients and 42 control individuals. Twenty-six (70.2%) SSc patients had HLA class II alleles compatible either for their offspring or mother, compared with only nine (21%) control individuals. The four patients with juvenile onset SSc we analyzed had alleles compatible with their mothers. These results suggest that in some patients, SSc may, indeed, be a form of chronic GVHD caused by fetal or maternal cells which have crossed the placenta during pregnancy and have remained unrecognized by the host due to class II HLA compatibility, and that subsequent activation of these cells by as yet unknown stimuli result in the development of the disease. Received: 20 February 1997 / Revised: 15 July 1997     

Human fetal mesenchymal stem cells

Stem cells have been isolated at all stages of development from the early developing embryo to the post-reproductive adult organism. However, the fetal environment is unique as it is the only time in ontogeny that there is migration of stem cells in large numbers into different organ compartments. While fetal neural and haemopoietic stem cells (HSC) have been well characterised, only recently have mesenchymal stem cells from the human fetus been isolated and evaluated. Our group have characterised in human fetal blood, liver and bone marrow a population of non-haemopoietic, non-endothelial cells with an immunophenotype similar to adult bone marrow-derived mesenchymal stem cells (MSC). These cells, human fetal mesenchymal stem cells (hfMSC), are true multipotent stem cells with greater self-renewal and differentiation capacity than their adult counterparts. They circulate in first trimester fetal blood and have been found to traffic into the maternal circulation, engrafting in bone marrow, where they remain microchimeric for decades after pregnancy. Though fetal microchimerism has been implicated in the pathogenesis of autoimmune disease, the biological role of hfMSC microchimerism is unknown. Potential downstream applications of hfMSC include their use as a target cell for non-invasive pre-natal diagnosis from maternal blood, and for fetal cellular and gene therapy. Using hfMSC in fetal therapy offers the theoretical advantages of avoidance of immune rejection, increased engraftment, and treatment before disease pathology sets in. Aside from allogeneic hfMSC in utero transplantation, the use of autologous hfMSC has been brought a step forward with the development of early blood sampling techniques, efficient viral transduction and clonal expansion. Work is ongoing to determine hfMSC fate post-transplantation in murine models of genetic disease. In this review we will examine what is known about hfMSC biology, as well as discussing areas for future research. The implications of hfMSC trafficking in pregnancy will be explored and the potential clinical applications of hfMSC in prenatal diagnosis and fetal therapy discussed.     

Fetal microchimerism and maternal health: A review and evolutionary analysis of cooperation and conflict beyond the womb

The presence of fetal cells has been associated with both positive and negative effects on maternal health. These paradoxical effects may be due to the fact that maternal and offspring fitness interests are aligned in certain domains and conflicting in others, which may have led to the evolution of fetal microchimeric phenotypes that can manipulate maternal tissues. We use cooperation and conflict theory to generate testable predictions about domains in which fetal microchimerism may enhance maternal health and those in which it may be detrimental. This framework suggests that fetal cells may function both to contribute to maternal somatic maintenance (e.g. wound healing) and to manipulate maternal physiology to enhance resource transmission to offspring (e.g. enhancing milk production). In this review, we use an evolutionary framework to make testable predictions about the role of fetal microchimerism in lactation, thyroid function, autoimmune disease, cancer and maternal emotional, and psychological health. Also watch the Video Abstract .     

Microchimerism: incidental byproduct of pregnancy or active participant in human health?

It is now well recognized that cells traffic in both directions between fetus and mother during pregnancy. Moreover, fetal cells have been found to persist for years, probably for a lifetime, in the circulation of healthy women. Harboring of cells from another individual at low levels is called microchimerism. Women have a predilection to autoimmune disease, and chronic graft-versus-host disease, a condition of human chimerism, shares similarities with some autoimmune diseases. The specific HLA genes of donor and host are known to be of central importance in graft-versus-host disease, and HLA class II genes are important in autoimmune disease. Considered together, these observations led to the hypothesis that microchimerism and HLA genes of host and non-host cells are involved in autoimmune diseases. Alternative sources of microchimerism include transfer from a twin or the mother during pregnancy, or from blood transfusion. Studies of systemic sclerosis, primary biliary cirrhosis, Sj?grens syndrome, pruritic eruption of pregnancy, myositis, and thyroid disease have both lent support and raised doubts about a potential role of microchimerism in autoimmune disease.     

Bovine fetal microchimerism in normal and embryo transfer pregnancies and its implications for biotechnology applications in cattle

Fetal cells and DNA have been detected in the maternal circulation during and after pregnancy in a few mammalian species. The incidence of similar microchimerism in cattle could have repercussion for the application of modern biotechnologies such as the transfer of transgenic embryos. To determine if feto-maternal leakage can occur in pregnant cows, we have analyzed maternal blood samples for the presence of fetal DNA during gestation and post-partum periods. Y chromosome-specific DNA was detected in up to 73% of blood samples from naturally mated heifers carrying conventional bull calves and a transgene-specific sequence in up to 50% of recipient cows carrying transgenic fetuses. These findings document for the first time that transplacental leakage of fetal DNA into the maternal circulation can occur in cattle despite the epitheliochorial placenta of ruminants, with potential implications for the utilization of recipient cows in the food chain.     

The effect of pregnancy on production of maternal endogenous hematopoietic stem cells

Fetal microchimerism refers to the presence of fetal cells in maternal blood and tissues during pregnancy. This microchimerism may result from trafficking of fetal and maternal blood across the placenta during pregnancy. Physiological changes in the maternal blood cellular milieu are also recognized during pregnancy and in the early postpartum period. Earlier studies showed that maternal blood contains CD34⁺ hematopoietic stem cells (HSCs) that bear paternal genetic markers or male phenotype, suggesting that these cells circulated to the mother from male fetuses during pregnancy. Other studies showed that these maternal HSCs have significantly lower expansion potential than their fetal counterparts. We have recently shown increased percentages of CD34⁺ HSCs in peripheral blood of pregnant and parous women. Herein, we hypothesize that pregnancy stimulates the production of endogenous CD34⁺ HSCs of maternal origin, a phenomenon which potentially could favor postpartum regenerative capacity.     

Heterogeneous Distribution of Fetal Microchimerism in Local Breast Cancer Environment

Fetal cells enter maternal circulation during pregnancy and persist in the woman’s body for decades, achieving a form of physiological microchimerism. These cells were also evidenced in tumors. We investigated the frequency and concentration of fetal microchimerism in the local breast cancer environment. From 19 patients with confirmed breast neoplasia, after breast surgical resection, we collected three fresh specimens from the tumor core, breast tissue at tumor periphery, and adjacent normal breast tissue. The presence of male DNA was analyzed with a quantitative PCR assay for the sex determining region gene (SRY) gene. In the group of women who had given birth to at least one son, we detected fetal microchimerism in 100% of samples from tumors and their periphery and in 64% (9 of 14) of those from normal breast tissue. The tissues from the tumor and its periphery carry a significantly increased number of SRY copies compared to its neighboring common breast tissue (p = 0.005). The median of the normalized SRY-signal was about 77 (range, 3.2–21467) and 14-fold (range, 1.3–2690) greater in the tumor and respectively in the periphery than in the normal breast tissue. In addition, the relative expression of the SRY gene had a median 5.5 times larger in the tumor than in its periphery (range, 1.1–389.4). We found a heterogeneous distribution of fetal microchimerism in breast cancer environment. In women with sons, breast neoplasia harbors male cells at significantly higher levels than in peripheral and normal breast tissue.     

Pregnancy allows the transfer and differentiation of fetal lymphoid progenitors into functional T and B cells in mothers

T lymphocytes of fetal origin found in maternal circulation after gestation have been reported as a possible cause for autoimmune diseases. During gestation, mothers acquire CD34+CD38+ cells of fetal origin that persist decades. In this study, we asked whether fetal T and B cells could develop from these progenitors in the maternal thymus and bone marrow during and after gestation. RAG-/--deficient female mice (Ly5.2) were mated to congenic wild-type Ly5.1 mice (RAG+/+). Fetal double-positive T cells (CD4+CD8+) with characteristic TCR and IL-7R expression patterns could be recovered in maternal thymus during the resulting pregnancies. We made similar observations in the thymus of immunocompetent mothers. Such phenomenon was observed overall in 12 of 68 tested mice compared with 0 of 51 controls (p=0.001). T cells could also be found in maternal spleen and produced IFN-gamma in the presence of an allogenic or an Ag-specific stimulus. Similarly, CD19+IgM+ fetal B cells as well as plasma Igs could be found in maternal RAG-/- bone marrow and spleen after similar matings. Our results suggest that during gestation mothers acquire fetal lymphoid progenitors that develop into functional T cells. This fetal cell microchimerism may have a direct impact on maternal health.     

Y-chromosome DNA Is Present in the Blood of Female Dogs Suggesting the Presence of Fetal Microchimerism

Fetal microchimerism has been suggested to play contradictory roles in women’s health, with factors including age of the recipient, time elapsed since microchimerism occurred, and microchimeric cell type modulating disease. Both beneficial and harmful effects have been identified in wound healing and tissue regeneration, immune mediated disease, and cancer. This area of research is relatively new, and hindered by the time course from occurrence of fetal microchimerism to the multi-factorial development of disease. Dogs represent an excellent model for study of fetal microchimerism, as they share our environment, have a naturally condensed lifespan, and spontaneously develop immune-mediated diseases and cancers similar to their human counterparts. However, fetal microchimerism has not been described in dogs. These experiments sought preliminary evidence that dogs develop fetal microchimerism following pregnancy. We hypothesized that Y chromosomal DNA would be detected in the peripheral blood mononuclear cells of female dogs collected within two months of parturition. We further hypothesized that Y chromosomal DNA would be detected in banked whole blood DNA samples from parous female Golden Retrievers with at least one male puppy in a prior litter. Amplification of DNA extracted from five female Golden Retrievers that had whelped within the two months prior to collection revealed strong positive bands for the Y chromosome. Of banked, parous samples, 36% yielded positive bands for the Y chromosome. This is the first report of persistent Y chromosomal DNA in post-partum female dogs and these results suggest that fetal microchimerism occurs in the canine species. Evaluation of the contributions of fetal microchimeric cells to disease processes in dogs as a model for human disease is warranted.     

Male Microchimerism in the Human Female Brain

In humans, naturally acquired microchimerism has been observed in many tissues and organs. Fetal microchimerism, however, has not been investigated in the human brain. Microchimerism of fetal as well as maternal origin has recently been reported in the mouse brain. In this study, we quantified male DNA in the human female brain as a marker for microchimerism of fetal origin (i.e. acquisition of male DNA by a woman while bearing a male fetus). Targeting the Y-chromosome-specific DYS14 gene, we performed real-time quantitative PCR in autopsied brain from women without clinical or pathologic evidence of neurologic disease (n = 26), or women who had Alzheimer’s disease (n = 33). We report that 63% of the females (37 of 59) tested harbored male microchimerism in the brain. Male microchimerism was present in multiple brain regions. Results also suggested lower prevalence (p = 0.03) and concentration (p = 0.06) of male microchimerism in the brains of women with Alzheimer’s disease than the brains of women without neurologic disease. In conclusion, male microchimerism is frequent and widely distributed in the human female brain.     

Murine maternal cell microchimerism: analysis using real-time PCR and in vivo imaging

In humans, maternal cells are present in the affected tissues of children with inflammatory myopathy, scleroderma, and neonatal lupus. It is unknown if maternal cell microchimerism (MCM) contributes to the pathology of disease. We sought to understand the factors that affect MCM to serve as a baseline for future mechanistic studies. Using a mouse model, we bred female mice transgenic for the luciferase (Luc) reporter gene to wild-type (WT) males. The WT offspring were sacrificed at various postnatal ages. DNA was extracted from multiple organs, and real-time PCR amplification was used to quantify Luc transgene as a marker for maternally derived cells. Sensitivity was one to two transgenic cells per 100,000 WT cells. MCM was noted in 85% of mice and 45% of tissues assayed. The average quantity of MCM was 158 maternal cells per 100,000 neonatal cells. The organs displaying the highest frequency and quantity of MCM were heart and lung (P < 0.001). Postnatal age up to 21 days did not appear to affect levels of MCM (P = 0.47), whereas increasing parity may increase levels of MCM. The data show that MCM is a common occurrence in healthy newborn mice, that it is present in their major organs, and that there are organ specific differences. This may represent differential migration of maternal cells or varying receptivity of specific fetal organs to microchimerism. Pregnancy history appears to play a role in maternal cell trafficking. The role of MCM in pregnancy and disease pathogenesis remains to be elucidated.     

X chromosome monosomy: a common mechanism for autoimmune diseases

The majority of human autoimmune diseases are characterized by female predominance. Although sex hormone influences have been suggested to explain this phenomenon, the mechanism remains unclear. In contrast to the role of hormones, it has been suggested, based on pilot data in primary biliary cirrhosis, that there is an elevation of monosomy X in autoimmune disease. Using peripheral white blood cells from women with systemic sclerosis (SSc), autoimmune thyroid disease (AITD), or healthy age-matched control women, we studied the presence of monosomy X rates using fluorescence in situ hybridization. We also performed dual-color fluorescence in situ hybridization analysis with a chromosome Y alpha-satellite probe to determine the presence of the Y chromosome in the monosomic cells. In subsets of patients and controls, we determined X monosomy rates in white blood cell subpopulations. The rates of monosomy X increased with age in all three populations. However, the rate of monosomy X was significantly higher in patients with SSc and AITD when compared with healthy women (6.2 +/- 0.3% and 4.3 +/- 0.3%, respectively, vs 2.9 +/- 0.2% in healthy women, p < 0.0001 in both comparisons). Importantly, X monosomy rate was more frequent in peripheral T and B lymphocytes than in the other blood cell populations, and there was no evidence for the presence of male fetal microchimerism. These data highlight the thesis that chromosome instability is common to women with SSc and AITD and that haploinsufficiency for X-linked genes may be a critical factor for the female predominance of autoimmune diseases.     

Microchimerism in health and disease

Microchimerism has been defined by the presence of a low number of circulating cells transferred from one individual to another. This transfer takes place naturally during pregnancy, between mother and fetus and/or between fetuses in multi-gestational pregnancies. Furthermore, the establishment of microchimerism can also occur during blood transfusion and organ transplants. Microchimeric cells have been implicated in health and disease. Microchimerism has been correlated with the hyporesponsiveness of the maternal immune system towards the fetal allograft and with the longevity of organ transplants. However, maternal microchimeric cells have been implicated in diseases of the neonate including neonatal graft-versus-host disease, severe combined immunodeficiency and erythema toxicum neonatorum. And more recently, microchimeric cells have been implicated in the pathogenesis of autoimmune diseases including systemic sclerosis and myositis.     

Fetal cells in the maternal circulation during first trimester in pregnancies

To investigate the presence of fetal cells in the maternal circulation during early pregnancy, the polymerase chain reaction was used to test the presence of human Y chromosome-specific ZFY and SRY gene DNA sequences in maternal peripheral blood specimens from 19 women carrying male fetuses and 12 women carrying female fetuses. The presence of fetal cells was suggested as early as 6 weeks gestation in 1 of the 19 women bearing male fetuses. Fetal cells were present in the maternal circulation of 15 of the 19 women by 9 weeks gestation, and in only 1 of the 19 were fetal cells not detected until the 12th week after conception. These results suggest that identification of fetal cells in the maternal circulation is possible with a properly designed and executed polymerase chain reaction. However, there was considerable variation with respect to when these fetal cells first became detectable during pregnancy. These fetal cells are potentially a valuable source of material for biochemical and genetic studies of the fetuses.     

Emergent roles of maternal microchimerism in postnatal development

Maternal microchimerism (MMc) is the phenomenon that a low number of cells from the mother persists within her progeny. Despite their regular presence in mammalian pregnancies, the overall cell type repertoire and roles of maternal cells, especially after birth, remain unclear. By using transgenic mouse strains and human umbilical blood samples, recent studies have for the first time characterized and quantified MMc cell type repertoires in offspring, identified the cross-generational influence on fetal immunity, and determined possible factors that affect their presence in offspring. This review summarizes new findings, especially on the maternal cell type repertoires and their potential role in utero, in postnatal life, and long after birth.