Mesenchymal stem cells reside in a vascular niche in the decidua basalis and are absent in remodelled spiral arterioles.

INTRODUCTION: Maternal decidua basalis tissue attached to the placenta following delivery is a source of decidual mesenchymal stem cells (DMSCs). The in vitro characteristics of DMSCs have been partly defined but their in vivo function(s) are poorly understood. The anatomic location, or niche, provides clues regarding potential in vivo function(s) of DMSCs, but the niche has not been described. METHODS: Cells were isolated from the decidua basalis and flow cytometric analyses showed the expected phenotypic profile for MSC cell surface markers. In vitro, the cells differentiated into adipocytes, osteocytes, and chondrocytes. DMSCs were then stained with antibodies by immunofluorescence detection. RESULTS: Immunocytochemistry revealed that DMSCs were positive for FZD-9, STRO-1, 3G5, and α-SMA as expected and lacked expression of vWF and Ck7. Fluorescence in situ hybridization analysis showed the cultured cells were of maternal origin. Immunofluorescence was carried out on placental bed biopsies using the FZD-9, STRO-1, 3G5, and α-SMA antibodies. DMSCs were located in the vascular niche in decidua basalis. Immunofluorescence with antibodies to FZD-9, Ck7 and vWF revealed DMSCs in the vascular niche surrounding intact non-transformed spiral arterioles but DMSCs were absent in fully transformed spiral arterioles. DISCUSSION: Spiral arteriole remodelling is a critical feature of human pregnancy. The DMSC niche was investigated in fully transformed and non-transformed spiral arterioles. DMSCs have not been previously implicated in spiral arteriole remodelling. The absence of DMSCs around fully transformed spiral arterioles suggests they are a target for replacement or destruction by invading placental extravillous trophoblast cells, which carry out spiral arteriole remodelling.

Trisomy 16 mosaicism at chorionic villus sampling and amniocentesis with a normal physical and intellectual outcome.

The identification of trisomy mosaicism in the prenatal setting is often shrouded with uncertainty for the genetic counsellor, and more importantly for the parents. The outcomes for these pregnancies may well be normal, but abnormalities and even in utero death are possibilities depending on the chromosomal abnormality and the degree of mosaicism. Advice to parents following the diagnosis of trisomy 16 mosaicism at chorionic villus sampling, with confirmation at subsequent amniocentesis, and in the setting of apparently normal fetal ultrasonography, is necessarily cautious. Malformations are seen in the majority of infants born following a diagnosis of mosaic trisomy 16 at amniocentesis, and intrauterine growth retardation, with postnatal catch-up, is the rule. We report here a case with a normal outcome by age 2.5 years and in fact with above-average language ability, and in whom trisomy mosaicism was confirmed postnatally.

Methylation of the adenomatous polyposis coli (APC) gene in human placenta and hypermethylation in choriocarcinoma cells.

Methylation of the human APC gene promoter is associated with several different types of cancers and has also been documented in some pre-cancerous tissues. We have examined the methylation of APC gene promoters in human placenta and choriocarcinoma cells. This revealed a general hypomethylation of the APC-1b promoter and a pattern with monoallelic methylation of the APC-1a promoter in full term placental tissue. However, there was no evidence of a parent-of-origin effect, suggesting random post zygotic origin of methylation. Increased methylation of this promoter was observed in all choriocarcinoma-derived trophoblast cell lines, suggesting a trophoblastic origin of placental APC methylation and implicating APC hypermethylation in the development of this group of gestational tumours. Our demonstration of placental methylation of the APC-1a promoter represents the first observation of monoallelic methylation of this gene in early development, and provides further support for a role of canonical Wnt signalling in placental trophoblast invasiveness. This also implicates tumour suppressor gene silencing as an integral part of normal human placental development.

Trisomy 13 mosaicism at prenatal diagnosis: dilemmas in interpretation.

We describe six cases of trisomy 13 mosaicism detected at prenatal diagnosis. Most level I and level II trisomy 13 mosaicism detected at prenatal diagnosis is pseudomosaicism or confined placental mosaicism. Rarely, low-level mosaicism at chorionic villus sampling or amniocentesis reflects a true fetal mosaicism. In this case, a normal phenotype is a possible, but not a certain, outcome. Genetic counselling is not straightforward.