Lymphatic capillary hypoplasia in the skin of fetuses with increased nuchal translucency and Turner's syndrome: comparison with trisomies and controls

Mechanisms and cell lineages in lymphatic vascular development

Lymphatic vessels have critical roles in both health and disease and their study is a rapidly evolving area of vascular biology. The consensus on how the first lymphatic vessels arise in the developing embryo has recently shifted. Originally, they were thought to solely derive by sprouting from veins. Since then, several studies have uncovered novel cellular mechanisms and a diversity of contributing cell lineages in the formation of organ lymphatic vasculature. Here, we review the key mechanisms and cell lineages contributing to lymphatic development, discuss the advantages and limitations of experimental techniques used for their study and highlight remaining knowledge gaps that require urgent attention. Emerging technologies should accelerate our understanding of how lymphatic vessels develop normally and how they contribute to disease.

Spatiotemporal dynamics and heterogeneity of renal lymphatics in mammalian development and cystic kidney disease

Heterogeneity of lymphatic vessels during embryogenesis is critical for organ-specific lymphatic function. Little is known about lymphatics in the developing kidney, despite their established roles in pathology of the mature organ. We performed three-dimensional imaging to characterize lymphatic vessel formation in the mammalian embryonic kidney at single-cell resolution. In mouse, we visually and quantitatively assessed the development of kidney lymphatic vessels, remodeling from a ring-like anastomosis under the nascent renal pelvis; a site of VEGF-C expression, to form a patent vascular plexus. We identified a heterogenous population of lymphatic endothelial cell clusters in mouse and human embryonic kidneys. Exogenous VEGF-C expanded the lymphatic population in explanted mouse embryonic kidneys. Finally, we characterized complex kidney lymphatic abnormalities in a genetic mouse model of polycystic kidney disease. Our study provides novel insights into the development of kidney lymphatic vasculature; a system which likely has fundamental roles in renal development, physiology and disease.

In most organs in the body, fluid tends to build up in the spaces between cells, especially if the organs become inflamed. Each organ has a ‘waste disposal system’; a set of specialized tubes called lymphatic vessels, to clear away this excess fluid and keep a check on inflammation. Defects in these tubes have been linked to a wide range of diseases including heart attacks, obesity, dementia and cancer.

The kidneys are responsible for filtering blood and balancing many of the body’s chemical processes. Polycystic kidney disease (PKD) is the most common genetic kidney disorder and it results in cysts filled with fluid building up in the kidney. The growth of cysts in PKD may be due to a problem with the lymphatic vessels. However, compared to other organs, how lymphatic vessels first form within the kidney and what they do is not well understood.

Now, Jafree et al. have used three-dimensional imaging to study how lymphatic vessels form in the kidneys of mice and humans. The experiments showed that lymphatic vessels first appear when mouse kidneys are about half developed, and start to grow rapidly when the kidneys are thought to begin filtering blood. Clusters of cells that may help lymphatic vessels to grow were also found hidden deep within the kidneys of mouse embryos. Treating the kidneys with a factor that stimulates the growth of lymphatic vessels increased the numbers of these clusters. Jafree et al. found similar clusters of cells in human kidneys, suggesting that lymphatic vessels in the kidneys of different mammals may develop in the same way.

Further experiments showed that the lymphatic vessels of kidneys in mice with PKD become distorted early on in the disease, when cysts are still small and before the mice develop symptoms. In the future, identifying drugs that target kidney lymphatic vessels may lead to more effective treatments for patients with PKD and other kidney diseases.

Recognition and management of adults with Turner syndrome: From the transition of adolescence through the senior years

Turner syndrome is recognized now as a syndrome familiar not only to pediatricians and pediatric specialists, medical geneticists, adult endocrinologists, and cardiologists, but also increasingly to primary care providers, internal medicine specialists, obstetricians, and reproductive medicine specialists. In addition, the care of women with Turner syndrome may involve social services, and various educational and neuropsychologic therapies. This article focuses on the recognition and management of Turner syndrome from adolescents in transition, through adulthood, and into another transition as older women. It can be viewed as an interpretation of recent international guidelines, complementary to those recommendations, and in some instances, an update. An attempt was made to provide an international perspective. Finally, the women and families who live with Turner syndrome and who inspired several sections, are themselves part of the broad readership that may benefit from this review.

Angiogenic Gene Expression in Down Syndrome Fetal Hearts

INTRODUCTION

Forty percent of Down syndrome (DS) fetuses have congenital heart defects (CHD). An abnormal angiogenic environment has been described in euploid fetuses with CHD. However, the underlying pathophysiologic pathway that contributes to CHD in DS remains unknown. The objective was to compare the expression of angiogenic factors and chronic hypoxia genes in heart tissue from DS and euploid fetuses with and without CHD.

METHODS

The gene expression profile was determined by real-time PCR quantification in heart tissue from 33 fetuses with DS, 23 euploid fetuses with CHD and 23 control fetuses.

RESULTS

Angiogenic factors mRNA expression was significantly increased in the DS group compared to the controls (soluble fms-like tyrosine kinase-1, 81%, p = 0.007; vascular endothelial growth factor A, 57%, p = 0.006, and placental growth factor, 32%, p = 0.0227). Significant increases in the transcript level of hypoxia-inducible factor-2α and heme oxygenase 1 were also observed in the DS group compared to the controls. The expression of angiogenic factors was similar in DS fetuses and CHD euploid fetuses with CHD.

CONCLUSION

Abnormal angiogenesis was detected in the hearts of DS fetuses with and without CHD. Our results suggest that DS determines an intrinsically angiogenic impairment that may be present in the fetal heart.

Development of Blood and Lymphatic Endothelial Cells in Embryonic and Fetal Human Skin

Blood and lymphatic vessels provide nutrients for the skin and fulfill important homeostatic functions, such as the regulation of immunologic processes. In this study, we investigated the development of blood and lymphatic endothelial cells in prenatal human skin in situ using multicolor immunofluorescence and analyzed angiogenic molecules by protein arrays of lysates and cell culture supernatants. We found that at 8 to 10 weeks of estimated gestational age, CD144(+) vessels predominantly express the venous endothelial cell marker PAL-E, whereas CD144(+)PAL-E(-) vessels compatible with arteries only appear at the end of the first trimester. Lymphatic progenitor cells at 8 weeks of estimated gestational age express CD31, CD144, Prox1, and temporary PAL-E. At that developmental stage not all lymphatic progenitor cells express podoplanin or Lyve-1, which are acquired with advancing gestational age in a stepwise fashion. Already in second-trimester human skin, the phenotype of blood and lymphatic vessels roughly resembles the one in adult skin. The expression pattern of angiogenic molecules in lysates and cell culture supernatants of prenatal skin did not reveal the expected bent to proangiogenic molecules, indicating a complex regulation of angiogenesis during ontogeny. In summary, this study provides enticing new insights into the development and phenotypic characteristics of the vascular system in human prenatal skin.

The lymphatic phenotype in Turner syndrome: an evaluation of nineteen patients and literature review

Turner syndrome is a complex disorder caused by an absent or abnormal sex chromosome. It affects 1/2000-1/3000 live-born females. Congenital lymphoedema of the hands, feet and neck region (present in over 60% of patients) is a common and key diagnostic indicator, although is poorly described in the literature. The aim of this study was to analyse the medical records of a cohort of 19 Turner syndrome patients attending three specialist primary lymphoedema clinics, to elucidate the key features of the lymphatic phenotype and provide vital insights into its diagnosis, natural history and management. The majority of patients presented at birth with four-limb lymphoedema, which often resolved in early childhood, but frequently recurred in later life. The swelling was confined to the legs and hands with no facial or genital swelling. There was only one case of suspected systemic involvement (intestinal lymphangiectasia). The lymphoscintigraphy results suggest that the lymphatic phenotype of Turner syndrome may be due to a failure of initial lymphatic (capillary) function.

The lymphatic phenotype in Turner syndrome: an evaluation of nineteen patients and literature review

Turner syndrome is a complex disorder caused by an absent or abnormal sex chromosome. It affects 1/2000-1/3000 live-born females. Congenital lymphoedema of the hands, feet and neck region (present in over 60% of patients) is a common and key diagnostic indicator, although is poorly described in the literature. The aim of this study was to analyse the medical records of a cohort of 19 Turner syndrome patients attending three specialist primary lymphoedema clinics, to elucidate the key features of the lymphatic phenotype and provide vital insights into its diagnosis, natural history and management. The majority of patients presented at birth with four-limb lymphoedema, which often resolved in early childhood, but frequently recurred in later life. The swelling was confined to the legs and hands with no facial or genital swelling. There was only one case of suspected systemic involvement (intestinal lymphangiectasia). The lymphoscintigraphy results suggest that the lymphatic phenotype of Turner syndrome may be due to a failure of initial lymphatic (capillary) function.

Maternal serum placental growth factor at 11-13 weeks' gestation and fetal cardiac defects

OBJECTIVE

To investigate the relationship between fetal heart defects and maternal serum placental growth factor (PlGF), a marker of placental angiogenesis.

METHODS

Maternal serum PlGF, pregnancy-associated plasma protein-A (PAPP-A) and uterine artery pulsatility index (UtA-PI) at 11-13 weeks' gestation were compared in 68 cases of isolated fetal major heart defects and 340 normal controls. Variables were converted into multiples of the median (MoM) after adjustment for gestational age, maternal age, racial origin, weight, parity and method of conception, and then compared between groups. The cardiac defects included 11 cases of obstruction of the left ventricular outflow tract (LVOT), 25 conotruncal abnormalities and 32 valve defects.

RESULTS

The median PlGF-MoM in the heart defect group was lower than in controls (0.80 (interquartile range (IQR), 0.57-1.08) vs 1.00 (IQR, 0.79-1.32); P < 0.0001). Low PlGF levels were observed in the presence of conotruncal and valve defects but not in the presence of LVOT defects. There was no significant difference between the group with fetal heart defects and controls in PAPP-A-MoM (0.95 (IQR, 0.68-1.28) vs 1.01 (IQR, 0.70-1.39); P = 0.292) or UtA-PI-MoM (1.01 (IQR, 0.84-1.28) vs 0.99 (IQR, 0.80-1.20); P = 0.396).

CONCLUSION

In pregnancies with isolated fetal heart defects there is evidence of impaired placental angiogenesis in the absence of impaired placental perfusion and function.

Correlation of nuchal translucency and thyroxine at 11-13 weeks of gestation

OBJECTIVE

Nuchal translucency (NT) thickness is one of the major screening markers during the first trimester that could be influenced by several factors. Here, we investigated the association between NT thickness and thyroid related hormones.

METHODS

NT thickness was measured with transabdominal ultrasound in 643 pregnant women between 11 and 13 weeks of gestation. Maternal thyroxine (T4), free thyroxine (fT4) and thyroid-stimulating hormone (TSH) were evaluated. Bivariate correlations were assessed and thyroid profile was subcategorized with regard to the calculated reference ranges.

RESULTS

An inverse relation was found between serum levels of maternal T4 with NT thickness (r = -0.128, p = 0.001) and CRL (r = -0.168, p < 0.001). TSH and hCG were also found to be correlated (Spearman's correlation coefficient = -0.092, p = 0.019). Prevalence of maternal hypothyroidism and subclinical hypothyroidism were 1.1% and 3.7%, respectively.

CONCLUSION

Thyroid function tests are found to independently influence NT measurements in the first trimester. Assessment of hormones such as thyroxine could optimize the interpretation of screening tests for pathological conditions during pregnancy.

Increased nuchal translucency and congenital heart disease

Sonographic assessment of fetal nuchal translucency (NT) thickness is the cornerstone of screening for chromosomal abnormality at 11-13(+6) weeks gestation. This marker was first recognized in pregnancies being karyotyped for advanced maternal age, but its underlying pathophysiology remains to be fully determined. Although increased NT is clearly associated with changes in both lymphatic and cardiac development, neither is an obvious causative agent. The association with cardiac defects has now being subjected to a significant amount of research, with a large body of evidence showing that this marker is also a screening tool for major cardiac defects - although it performs more modestly than for chromosomal abnormality. The field continues to change rapidly. Recent evidence that uses a combination of increased NT, tricuspid regurgitation and abnormal flow in the 'a' wave of the ductus venosus can provide an effective screening strategy to predict many major cardiac defects at this early stage of pregnancy.