Ultrastructural and immunohistochemical studies of Wharton's jelly umbilical cord cells

Bioengineering aspects of the umbilical cord

The umbilical cord and its constituent tissues: an outer layer of amnion, porous Wharton's jelly, two umbilical arteries, and one umbilical vein, are designed to protect blood flow to the fetus during a term pregnancy. The outer amnion layer may regulate fluid pressure within the umbilical cord. The porous, fluid filled Wharton's jelly likely acts to prevent compression of the vessels. Blood flow is regulated by smooth muscle surrounding the arteries that is intermingled with a collagen based extracellular matrix (ECM). Doppler ultrasound measurements of blood flow within the umbilical cord, and at specific sites within the developing fetus, provide evidence of impaired blood flow in conditions such as preeclampsia. Mechanosensory communication between cells and the extracellular matrix (ECM) may likely result in cords possessing abnormal physical dimensions, impaired hemodynamics, and altered composition within the umbilical cord tissues. Few studies have explored the biomechanics of the intact umbilical cord, with its constituent tissues, from normal pregnancies or abnormal pregnancies, maternal or fetal complications. Here, alterations in the umbilical cord are reviewed concerning anatomical abnormalities, disease, or chromosomal alterations using sonography, Doppler ultrasound, histology, and biomolecular and biochemical analyses. This paper considers how current knowledge of the umbilical cord and its constituent tissues can be used to infer biomechanical function. In addition, the mechanical consequences of structural abnormalities and altered tissue structure or composition are discussed with a specific focus on preeclampsia.

Stillborn or liveborn? Comparing umbilical cord immunohistochemical expression of vitality markers (tryptase, alpha(1)-antichymotrypsin and CD68) by quantitative analysis and confocal laser scanning microscopy

The distinction between stillborn and liveborn infants and the demonstration of a separate existence of fetuses are central issues in the daily practice of perinatologists and pathologists. The current knowledge about the chronology of responses of the tissue following the occurrence of a vital reaction, as well as the existence of numerous studies that aimed at identifying markers of vitality of cutaneous lesions, induced us to investigate the umbilical cord for the presence or absence of vitality indexes. We investigated 45 samples of umbilical cords obtained during post-mortem examinations of stillborns, as well as samples of umbilical cords taken from newborns after normal labor. On these samples, we performed a complete immunohistochemical study. Our results showed that some of the parameters investigated, such as tryptase for the mast cell, CD68, and alpha-1-antichymotrypsin, showed a statistically significant (p<0.0001) different expression in the two groups under study (stillborn and liveborn). Owing to the strong different expression of these markers in the samples of the umbilical cords from liveborns, compared to those from stillborns, one might regard them as reliable parameters, to which the pathologist may resort whenever he is dealing with the distinction between stillborns and liveborns.

Mutational analysis of the mitochondrial tRNA genes and flanking regions in umbilical cord tissue from uninfected infants receiving AZT-based therapies for prophylaxis of HIV-1

A sensitive vertical denaturing gradient gel electrophoresis (DGGE) method, using 13 unipolar psoralen-clamped PCR primer pairs, was developed for detecting sequence variants in the 22 tRNA genes and flanking regions (together spanning approximately 21%) of the human mitochondrial genome. A study was conducted to determine (i) if mitochondrial DNA (mtDNA) polymorphisms and/or mutations were detectable in healthy newborns and (ii) if prepartum 3'-azido-2',3'-dideoxythymidine (AZT) based HIV-1 prophylaxis was associated with significant increases in mtDNA mutations and changes in the degree of heteroplasmy of sequence variants in uninfected infants born to HIV-1-infected mothers. DGGE analysis of umbilical cord tissue (where vascular endothelium and smooth muscle cells are the major source of mtDNA) showed that mtDNA sequence variants were significantly elevated by threefold in AZT-treated infants compared with unexposed controls (P < 0.001), with 24 changes observed in 19/52 (37%) treated newborns (averaging 0.46 changes/subject) versus only eight changes found in 7/55 (13%) unexposed newborns (averaging 0.15 changes/subject). Six distinct sequence variants occurring in unexposed controls were predominately synonymous and homoplasmic, representing previously reported polymorphisms. Uninfected infants exposed to a combination of AZT and 2',3'-dideoxy-3'-thiacytidine and "maternal HIV-1" had a significant shift in the spectrum of mutations (P = 0.04) driven by increases in nonsynonymous heteroplasmic sequence variants at polymorphic sites (10 distinct variants) and novel sites (four distinct variants). While the weight of evidence suggests that prepartum AZT-based prophylaxis produces mtDNA mutations, additional research is needed to determine the degree to which fetal responses to maternal HIV-1 infection, in the absence of antiretroviral treatment, contribute to prenatal mtDNA mutagenesis.

Reproducible methodology for the isolation of mesenchymal stem cells from human umbilical cord and its potential for cardiomyocyte generation

Mesenchymal stem cells (MSCs) are considered to be a source of stem cells in tissue regeneration and therapeutics, due to their ability to undergo proliferation and differentiation. Complications associated with bone marrow-derived MSCs has prompted researchers to explore alternative sources of MSCs. The human umbilical cord is one such source; it is easily available and its collection is non-invasive. The sources of MSCs are non-controversial and thus they are not subjected to ethical constraints, as in the case of embryonic stem cells. MSCs are multipotent stem cells and has the ability to differentiate into various cell types of the mesodermal lineage. The aim of this study was to establish a reproducible method for the isolation of MSCs from human umbilical cord, as the few methods published till date gave inconsistent results and had a mixed population of contaminating endothelial cells. In our isolation strategy, we isolated a pure population of MSCs from Wharton's jelly of the human umbilical cord, which is very rich in collagen, and we used a high concentration of collagenase enzyme in the isolation of MSCs. Extensive phenotypic characterization analysis of these cells, using flow cytometry and antibody staining methods, have shown that we were able to isolate a pure population of the mesenchymal lineage cells that is devoid of haematopoietic and endothelial cell contaminants. When these MSCs were subjected to cardiomyocyte differentiation, we observed a change in the morphological characteristics, which was accompanied by the formation of myotube structures and spontaneous beating after 21 days.

Neural differentiation and potential use of stem cells from the human umbilical cord for central nervous system transplantation therapy

The human umbilical cord is a rich source of autologous stem and progenitor cells. Interestingly, subpopulations of these, particularly mesenchymal-like cells from both cord blood and the cord stroma, exhibited a potential to be differentiated into neuron-like cells in culture. Umbilical cord blood stem cells have demonstrated efficacy in reducing lesion sizes and enhancing behavioral recovery in animal models of ischemic and traumatic central nervous system (CNS) injury. Recent findings also suggest that neurons derived from cord stroma mesenchymal cells could alleviate movement disorders in hemiparkinsonian animal models. We review here the neurogenic potential of umbilical cord stem cells and discuss possibilities of their exploitation as an alternative to human embryonic stem cells or neural stem cells for transplantation therapy of traumatic CNS injury and neurodegenerative diseases.

TGF-beta binding in human Wharton's jelly

Our previous study reported that TGF-beta may be isolated from human Wharton's jelly (WJ) in a form of soluble, high molecular complex(es). We decided to study the effect of extracellular matrix degradation and reduction of disulphide bridges reduction on the release of TGF-beta from WJ. The WJ prepared from the umbilical cords of newborns delivered at term by healthy mothers was homogenised and treated with hyaluronidase, collagenase, heparinase, chondroitinase and beta-mercaptoethanol, the resulting extracts were then submitted to TGF-beta immunoassay and SDS/PAGE followed by Western immunoblotting. The effect of metalloproteinase activation on TGF-beta was also studied. Pre-treatment of WJ homogenates with hyaluronidase or collagenase markedly increased the extractability of TGF-beta, but did not dissociate the complexes. In contrast, the action of beta-mercaptoethanol resulted in the release of free TGF-beta; but activation of metalloproteinases resulted in the disappearance of this factor. We conclude that TGF-beta1 is bound through disulphide bonds to an extracellular matrix component of WJ. The large amount of collagen fibrils and hyaluronate molecules which surround the cells scattered in WJ may prevent the access of extracting solution to TGF-beta causing a low extractability of this factor. Although hyaluronate and collagen do not bind TGF-beta directly, they may present a barrier that prevents the diffusion of TGF-beta in WJ and results in its concentration around the cells thereby facilitating its interaction with membrane receptors and subsequent stimulation of cell division and synthesis of extracellular matrix components.

Functional structure of adipocytes differentiated from human umbilical cord stroma-derived stem cells

It has been previously demonstrated that human umbilical cord stroma-derived stem cells (HUCSCs) are competent to differentiate into adipocytes. However, controversies have arisen as to whether HUCSCs can become mature adipocytes or not, and to what extent these cells can be induced in adipogenic pathway. Here, we extensively analyzed their adipogenic potency with a structural and functional approach by determining lipid formation dynamics in concordance to adipocyte-specific markers. During a 35-day period, HUCSCs respond to adipogenic induction, at which point 88% of cells exhibited multilocular lipid granules (LGs) having a mean diameter of 3 mum in round-shaped, F-actin-poor cells. Although the 1st week of induction did not generally display typical lipidogenic phenotypes, the degree of adipogenesis was dissected and confirmed by mRNA expressions of peroxisome proliferator-activated receptor gamma, C/EBP-beta, sterol regulatory element-binding transcription factor 1, adipophilin, stearoyl-CoA desaturase, glycerol 3-phosphate dehydrogenase 1, LIPE, adiponectin, and leptin. All markers tested were found elevated in various amounts (3-70-fold) around day 7 and reached a plateau after day 14 or 21 (5-335-fold). Perilipin as a surface protein around the LGs was confined exclusively to the enlarging LGs. Conclusively, we propose that after the termination of proliferation, HUCSCs possess the biochemical and cellular machinery to successfully differentiate into maturing adipocytes under adipogenic conditions, and this feature will ultimately allow these fetus-derived stem cells to be used for various therapeutic or esthetic purposes.

Concise review: human umbilical cord stroma with regard to the source of fetus-derived stem cells

Human umbilical cord (UC) has been a tissue of increasing interest in recent years. Many groups have shown the stem cell potency of stromal cells isolated from the human UC mesenchymal tissue, namely, Wharton's jelly. Since UC is a postnatal organ discarded after birth, the collection of cells does not require an invasive procedure with ethical concerns. Stromal cells, as the dominant cells of this fetus-derived tissue, possess multipotent properties between embryonic stem cells and adult stem cells. They bear a relatively higher proliferation rate and self-renewal capacity. Although they share common surface markers with bone marrow-derived MSCs, they also express certain embryonic stem cell markers, albeit in low levels. Without any spontaneous differentiation, they can be successfully differentiated into mature adipocytes, osteoblasts, chondrocytes, skeletal myocytes, cardiomyocytes, neurons, and endothelial cells. While causing no immunorejection reaction, they effectively function in vivo as dopaminergic neurons, myocytes, and endothelial cells. Given these characteristics, particularly the plasticity and developmental flexibility, UC stromal cells are now considered an alternative source of stem cells and deserve to be examined in long-term clinical trials. This review first aims to document the published findings so far regarding the nature of human UC stroma with special emphasis on the spatial distribution and functional structure of stromal cells and matrix, which serves as a niche for residing cells, and, secondly, to assess the in vitro and in vivo experiments in which differential stem cell potencies were evaluated.

Multiple true umbilical knots: a silent risk for intrauterine growth restriction with anomalous hemodynamic pattern

True knots of the umbilical cord can represent a serious complication for the fetus due to the possible alteration in the fetal circulation with consequent intrauterine growth restriction or fetal death. We report a case of 5 true umbilical cord knots associated with severe fetal growth restriction and an abnormal hemodynamic pattern. The Doppler examination showed a hemodynamic pattern characterized by an early alteration in the waveform profile in the fetal venous districts with normal impedance to flow values in both uterine and umbilical arteries. This normal profile of the umbilical arteries remained unchanged until the last stage of hemodynamic decompensation, while the profiles of the uterine arteries remained normal until delivery. This case report suggests that it is important to pay close attention to the evaluation of the fetal cord in situations in which the above described hemodynamic pattern is noted. Although the ultrasound diagnosis of true knots is extremely difficult, the presence of a true knot should always be suspected in the presence of an intrauterine growth restriction fetus when the venous district is altered before the fetal arterial districts after exclusion of other detectable reasons for growth restriction.

Reference intervals for the cross sectional area of the umbilical cord during gestation

OBJECTIVE

To establish reference values for the sonographic cross-sectional area of the umbilical cord during gestation and to correlate them with fetal anthropometric parameters.

METHODS

A cross-sectional study was performed involving 312 normal pregnant women at gestational ages 24-39 weeks. Measurement of the cross-sectional area of umbilical cord was performed on a plane adjacent to the insertion of the cord into fetal abdomen. The following anthropometric parameters were calculated: biparietal diameter, head circumference, abdominal circumference and femur length. A polynomial regression analysis identified the curves that were better adjusted to the average and standard deviation according to gestational age. Spearman correlation was used to evaluate the correlation of the cross-sectional area of umbilical cord with fetal anthropometric parameters.

RESULTS

A statistically significant correlation was observed between the cord cross-sectional area and gestational age (r=0.376, P<0.001, CI 95%[0.276; 0.467]).

CONCLUSIONS

The reference values of the cross-sectional area of umbilical cord increased according to gestational age until the 33rd week and are related to parameters of fetal growth.

Biology of stem cells in human umbilical cord stroma: in situ and in vitro surveys

Cells in the umbilical cord stroma have gained attention in recent years; however, differentiation to certain lineages in humans has been demonstrated in few studies. Unlike bone marrow MSCs, human umbilical cord stroma cells (HUCSCs) are far from being well characterized. This study attempts to describe proliferation, structural, and differentiation properties of these cells to account for their exceptional nature in many aspects. Cellular dynamics, cellular structure, and the degree of transformations during expansion and differentiation into mesenchymal and neuronal lineages were examined in vitro over a 10-month period. Comparisons with human bone marrow MSCs regarding differentiation were performed. HUCSCs in culture revealed two distinct cell populations, type 1 and type 2 cells, that possessed differential vimentin and cytokeratin filaments. Corresponding cells were encountered in cord sections displaying region-specific localization. alpha-Smooth muscle actin and desmin filaments, which were evident in cord sections, diminished through passages. No difference was noted regarding type 1 and type 2 cells in differentiation to chondrogenic, adipogenic, and osteogenic lineages, whereas a preferential differentiation was noted in neuronal lineage. Relative success was achieved by production of chondrocytic spheres and osteogenic monolayers, whereas adipocytes were immature compared with bone marrow MSCs. The presence of neuronal markers suggests that they transform into a certain state of maturity under neurogenic induction. Conclusively, HUCSCs retain their original phenotype in culture without spontaneous differentiation, have a limited lifespan, and bear multipotent stem cell characteristics. Given these characteristics, they may be generally considered progenitor cells if manipulated under appropriate conditions and deserve further study to be potentially used in cell-based therapies.

Lectin binding in the umbilical cord in altered glycemia

OBJECTIVE

Content and distribution of the oligosaccharides in the umbilical cord from pregnancies with altered glycemia were investigated.

STUDY DESIGN

A prospective cohort study was conducted in the Florence Policlinic of Careggi, Italy. Samples of cord from physiological pregnancies (n=20), from pregnancies with minor degree of glucose intolerance (n=20) and from pregnancies with gestational diabetes mellitus (GDM) treated with insulin (n=20) were collected. Eleven lectins were used (ConA, WGA, PNA, SBA, DBA, LTA, UEA I, OOA, GSL II, MAL II and SNA) in combination with chemical and enzymatic treatments.

RESULTS

Increase of N-acetyl-d-glucosamine and a loss of sialic acid in the umbilical cord of the cases with minor degree of glucose intolerance with respect to the other study groups was observed. d-Galactose(beta1-->3)-N-acetyl-d-galactosamine, N-acetyl-d-galactosamine and l-fucose were in less amount in both the pathological groups with respect to the control one.

CONCLUSION

The increase of some glycoconjugates carbohydrates and the loss of others in the umbilical cord from pregnancies with minor degree of glucose intolerance might be related to its morphofunctional alterations in a not diabetic altered glycemia. Moreover, the treatment with insulin in the GDM might play a role in restoring partially the normal glycosilation in the cord components in the attempt to renew some their functions.

Human umbilical cord perivascular (HUCPV) cells: a source of mesenchymal progenitors

We describe the isolation of a nonhematopoietic (CD45-, CD34-, SH2+, SH3+, Thy-1+, CD44+) human umbilical cord perivascular (HUCPV) cell population. Each HUCPV cell harvest (2-5 x 10(6), depending on the length of cord available) gave rise to a morphologically homogeneous fibroblastic cell population, which expressed alpha-actin, desmin, vimentin, and 3G5 (a pericyte marker) in culture. We determined the colony-forming unit-fibro-blast (CFU-F) frequency of primary HUCPV cells to be 1:333 and the doubling time, which was 60 hours at passage 0 (P0), decreased to 20 hours at P2. This resulted in a significant cell expansion, producing over 10(10) HUCPV cells within 30 days of culture. Furthermore, HUCPV cells cultured in nonosteogenic conditions contained a subpopulation that exhibited a functional osteogenic phenotype and elaborated bone nodules. The frequency of this CFU-osteogenic subpopulation at P1 was 2.6/10(5) CFU-F, which increased to 7.5/10(5) CFU-F at P2. Addition of osteogenic supplements to the culture medium resulted in these frequencies increasing to 1.2/10(4) and 1.3/10(4) CFU-F, respectively, for P1 and P2. CFU-O were not seen at P0 in either osteogenic or non-osteogenic culture conditions, but P0 HUCPV cells did contain a 20% subpopulation that presented neither class I nor class II cell-surface major histocompatibility complexes (MHC-/-). This population increased to 95% following passage and cryopreservation (P5). We conclude that, due to their rapid doubling time, high frequencies of CFU-F and CFU-O, and high MHC-/- phenotype, HUCPV cells represent a significant source of cells for allogeneic mesenchymal cell-based therapies.

Wharton's jelly as a reservoir of peptide growth factors

This study has assessed the amounts of insulin-like growth factor I (IGF-I), fibroblast growth factor (FGF), transforming growth factor beta (TGF-beta), platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) and their binding to extracellular matrix components of Wharton's jelly. Studies were performed on the umbilical cords taken from human newborns delivered by healthy mothers. Wharton's jelly was separated and submitted to homogenisation and extraction with acetic acid and Tris-HCl buffer. The assays of growth factors were carried out with the use of ELISA commercial kits, together with SDS/polyacrylamide gel electrophoresis of tissue extracts followed by Western immunoblotting. Several growth factors, viz. acidic FGF, basic FGF, EGF, IGF-I, PDGF and TGF-beta were detected in Wharton's jelly. The amounts of these factors per gram of tissue vary from about 40 pg (EGF, PDGF) to about 200 ng (IGF-I). The amounts of peptide growth factors calculated per microgram of DNA are distinctly higher in Wharton's jelly in comparison to the umbilical cord artery. Western blot analysis demonstrated that almost the entire amount of these factors is bound to high molecular weight components. Since the number of cells in Wharton's jelly is very low and the amounts of extracellular matrix components are very high, it is concluded that the cells are strongly stimulated by peptide growth factors to produce large amounts of collagen and glycosaminoglycans.

Correlação da área do cordão umbilical com parâmetros antropométricos em gestações normais

OBJETIVO: Este objetivou aferir a área de secção transversa do cordão umbilical (ASTCU) em gestações normais, com idade gestacional entre 20 e 40 semanas, para a construção de uma curva de valores normais para tal parâmetro. MATERIAIS E MÉTODOS: Foi realizado estudo transversal para determinar os valores de referência para a ASTCU em gestações normais (pacientes com datas precisas da última menstruação e exame ultra-sonográfico realizado antes da 20ª semana, sem qualquer doença conhecida). As medidas da ASTCU foram obtidas em plano adjacente à inserção do cordão umbilical no abdome. Os aparelhos de ultra-som utilizados foram da marca Synergy Multi Sync M500, Toshiba 140 e Toshiba Corevision, todos com transdutores transabdominais de 3,5 MHz. A análise estatística foi realizada pelo programa SPSS (Statistical Package for Social Sciences). RESULTADOS: Os dados obtidos foram considerados normais pelo teste de Kolmogorov-Smirnov e a curva de normalidade foi calculada por regressão linear. A análise de variância obtida pelo teste F (F = 356,27) mostrou que o modelo de regressão foi significativo ao nível de p < 0,01, mostrando que a curva estudou corretamente a população recrutada e que o intervalo de confiança (95%) continha o valor real da ASTCU. A equação de regressão encontrada para a ASTCU (y), de acordo com a idade gestacional (x), foi: y = -532,27 + 44,358x - 0,655x². CONCLUSÃO: Obtivemos uma curva de valores normais da ASTCU que mostra um crescimento progressivo de seus valores até a 32ª semana, seguida por um período de estabilização até a 34ª semana e uma queda de seus valores a partir da 35ª semana.

Immunohistochemical staining of IGF-I, IGF-binding proteins-1 and -3, and transforming growth factor beta-3 in the umbilical cords of preeclamptic patients

BACKGROUND

To detect the immunoreactivity of insulin-like growth factor-I, insulin-like growth factor-binding proteins-1 and -3 and transforming growth factor beta-3 in the umbilical cords of normal and preeclamptic patients.

METHODS

Umbilical cords were obtained from 15 normal and 15 preeclamptic patients. Immunoreactivities were determined using either indirect immunofluorescence or immunoperoxidase techniques on formalin-fixed, paraffin-embedded sections. Staining intensity was graded by a semiquantitative scoring method. The results were compared by Mann-Whitney U-test.

RESULTS

The umbilical cords were thinner and the vessels were hypoplastic in the preeclamptic group. Moderate staining intensity for insulin-like growth factor-I, insulin-like growth factor binding protein-1 and -3 and transforming growth factor-beta 3 was observed in normal patients. The preeclamptic group had mild and strong intensities for insulin-like growth factor-I and insulin-like growth factor binding protein-1, respectively, and intensity for insulin-like growth factor binding protein-3 did not change, but diffuse and increased intensity was observed for transforming growth factor-beta 3.

CONCLUSION

Changes in the intensity of insulin-like growth factor-I and its major binding protein and the transformation of growth factor-beta 3 may play a role in the pathogenesis of preeclampsia by altering the structure and responsiveness of the umbilical cord.

A transmission line model of the human foetal circulatory system

A transmission line model of the human foetal circulatory system is presented. The model has been developed in the frequency domain with the cardiac input modeled as a flow rather than as a pressure pulse and is structured upon electrical transmission line analogies. The model is formed by cascading solutions to the two-dimensional Navier-Stokes equations for both oscillatory and steady, laminar viscous fluid flow in isotropic visco-elastic tubes with thick walls, which are constrained by surrounding tissues. Simulations allow for representation of both forward and retrograde travelling flow and pressure waves in all of the main foetal arterial vessels. The solution is verified by a comparison of model generated Doppler indices in the thoracic aorta, abdominal aorta, iliac artery and both ends of the umbilical arteries with previously published indices obtained by clinical measurements in these arteries. For simulations of blood flow in a healthy foetus, the model generated Pulsatility and Resistance indices were on average within 8% of the corresponding clinical measurements. The model results also demonstrates that placental resistance must increase by a factor of three, corresponding to a 60% decrease in flow to the placenta, before umbilical arterial absent end diastolic flow is observed. Differences between indices obtained from simulations at opposite ends of the umbilical arteries increase with increasing placental resistance.

First-trimester umbilical cord diameter: a novel marker of fetal aneuploidy

OBJECTIVE

To compare the umbilical cord diameter at 10-14 weeks of gestation of chromosomally normal and abnormal fetuses.

METHODS

In a consecutive series of women, who were undergoing routine sonographic evaluation at 10-14 weeks of gestation, umbilical cord diameter and nuchal translucency were measured. Reference ranges for umbilical cord diameter according to gestational age and crown-rump length were constructed. Fetal karyotype was obtained at chorionic villus sampling, amniocentesis or at delivery in newborns with features suspicious for chromosomal abnormalities.

RESULTS

During the study period, 784 patients met the inclusion criteria. Of these, a fetal or placental chromosomal abnormality was present in 17 cases. The mean umbilical cord diameter increased with gestational age (r = 0.41, P < 0.001). The proportion of fetuses with an umbilical cord diameter above the 95th centile was higher in the presence of fetal or placental chromosomal abnormalities than in normal fetuses (5/17 vs. 39/767, P < 0.01). Among fetuses with an abnormal fetal or placental karyotype, nuchal translucency was above the 95th centile for gestational age in 10 cases. When only fetal chromosomal abnormalities were considered (n = 14), the combined detection rate was 85.7%(12/14).

CONCLUSIONS

Sonographic assessment of the umbilical cord in early gestation appears to identify a subset of fetuses at increased risk of chromosomal abnormalities.

Umbilical vein blood flow in fetuses with normal and lean umbilical cord

OBJECTIVE

To evaluate whether umbilical vascular coiling is correlated with the umbilical vein blood flow profile and to investigate if this is different between fetuses with a lean and those with a normal umbilical cord.

METHODS

Consecutive women with a singleton gestation who delivered at term and who underwent an ultrasound examination within 24 h from delivery were studied. Umbilical cord and vessel areas were calculated. Umbilical vein blood flow parameters were obtained by digital color Doppler velocity profile integration. After delivery, the umbilical coiling index was calculated.

RESULTS

One hundred and sixteen women were studied. Twelve (10.3%) had a lean umbilical cord (area < 10th centile). A significant correlation was found between the umbilical coiling index and the umbilical vein blood flow (r = 0.67, P < 0.001). A significant difference between fetuses with and without a lean cord was found in terms of: umbilical coiling index (0.18 +/- 0.08 vs. 0.29 +/- 0.09, P < 0.005), cord area (87.6 +/- 5.1 mm2 vs. 200.6 +/- 34.6 mm2, P < 0.001), Wharton's jelly amount (25.7 +/- 10.3 mm2 vs. 122.1 +/- 33.4 mm2, P < 0.001), umbilical vein blood flow (93.7 +/- 17.8 ml/kg per min vs. 126.0 +/- 23.4 ml/kg per min, P < 0.001), and umbilical vein blood flow mean velocity (6.6 +/- 2.7 cm/s vs. 9.0 +/- 3.6 cm/s, P < 0.05). The proportion of fetuses with an umbilical vein blood flow < 80 ml/kg per min was higher when the cord was lean than when it was normal (25% vs. 1.9%, P < 0.01).

CONCLUSIONS

Lean umbilical cords differ from normal cords not only from a structural point of view but also in the umbilical vein blood flow characteristics. This could explain the increased incidence of intrapartum complications and fetal growth restriction among fetuses with a lean and/or hypocoiled cord.

The role of low molecular weight hyaluronic acid contained in Wharton's jelly in necrotizing funisitis

The purpose of this research was to study the changes in the molecular weight of hyaluronic acid in Wharton's jelly altered by necrotizing funisitis. Umbilical cords were collected at delivery from 20 newborns without funisitis, 6 newborns with acute funisitis, and 4 newborns with necrotizing funisitis. Agarose gel electrophoresis of Wharton's jelly was performed to analyze the molecular weight of hyaluronic acid (HA). We also investigated the effects of low or high molecular weight HA on the production of interleukin-8 in human umbilical fibroblasts. In Wharton's jelly without funisitis, HA was 1150 +/- 280 kD in preterm newborns, regardless of gestational week at birth, and that in full-term newborns was 1100 +/- 200 kD. When acute funisitis was present, HA was 700 +/- 250 kD, and when necrotizing funisitis was present, HA was 520 +/- 100 kD. The molecular weight of HA was significantly below normal in newborns with necrotizing funisitis. Low molecular weight HA was associated with increased levels of IL-8 in the supernatant of cultured human umbilical fibroblasts in a time- and dose-dependent manner. High molecular weight HA did not induce the production of IL-8 in the same cells. Low molecular weight HA has a potent inflammatory action. The conversion from high to low molecular weight HA in Wharton's jelly may be important in the pathophysiology of necrotizing funisitis.

Study on myofibroblast differentiation in the stromal cells of Wharton's jelly: expression and localization of alpha-smooth muscle actin

To confirm the characteristics of the stromal cells of Wharton's jelly, we investigated the morphological changes in these cells during each trimester of pregnancy. We evaluated the cytoskeletal features of these cells by examining immunohistochemically the localization of one of the contractile proteins, alpha-smooth muscle actin (ASMA). After the second trimester, the stromal cells of Wharton's jelly were stained with ASMA antibody, exhibited the ultrastructural characteristics of the myofibroblasts, and began to express numerous microfilaments in the cytoplasm. Postembedding immunogold labeling detected immunoreactivity for ASMA on these microfilaments. The finding indicated that the stromal cells of Wharton's jelly undergo a time-dependent maturation involving the differentiation of myofibroblasts during the last 6 months of pregnancy. These cells possess a contractile function that may help to protect the umbilical vessels from compression, considering that ASMA was detected in the microfilamentous bundles.

Microfibrillar composition of umbilical cord matrix: characterization of fibrillin, collagen VI and intact collagen V

Ultrastructural studies made on human umbilical cord revealed that the striated collagen fibrils of the Wharton's jelly matrix are mixed with many microfibrillar structures. Microfibrils were found with a tubular cross-section of 10-12 nm diameter and were organized as beaded filaments characteristic of fibrillin-rich microfibrils. Beads had an average diameter of 25 nm and were spaced at about 50-80 nm. This ultrastructural observation was confirmed by indirect immunofluorescent staining of the jelly matrix using monoclonal antibody to fibrillin. Another constituent of the microfibrillar network was present as typical 100-nm periodic filaments of type VI collagen. Indirect immunofluorescent staining using antibodies to collagen VI showed for the first time that this collagen appeared to be distributed largely in the jelly matrix. In addition, other microfibrils with no specific banding pattern were observed. These microfibrils may constitute an organization of type V collagen different from the one which is generally assembled in heterotypic fibrils with collagen I. Among the latter heterotypic fibrils, type V collagen was studied using an anti-peptide antibody to the most N-terminal non-collagenous region of its alpha 2(V) chain. This antibody recognized a filamentous mesh decorating the bundles of collagen fibrils by immunofluorescent staining. This indicates that at least this part of alpha 2(V) chain may be accessible to the antibody at the surface of the fibrils.

Computerized microscope morphometry of umbilical vessels from pregnancies with intrauterine growth retardation and abnormal umbilical artery Doppler

Computerized microscope morphometry was used to study cross sections from the vessels of the umbilical cord in placentas of patients with intrauterine growth retardation (IUGR) that displayed either normal or abnormal umbilical arteries (UA) Doppler flow velocity waveforms (FVW). Cords from 63 eutrophic fetuses with normal Doppler (controls), 47 IUGR fetuses with normal Doppler and 32 IUGR fetuses with abnormal Doppler underwent morphometric analysis using a highly optimized microscope environment (HOME) and "CordHOME" software. IUGR with an accompanying normal Doppler versus control showed a reduction of Wharton jelly and both the total and lumen vein areas. IUGR with an accompanying pathological Doppler showed a comparable reduction in wall thickness and areas of every vessel. These findings indicate that the hypoplastic umbilical vessels are associated with an increase in placental vascular resistance that may be the consequence of underdevelopment in response to a chronic reduction in placental blood flow.

Stromal differentiation and architecture of the human umbilical cord

In order to assess the characteristics of its stromal cells and the distribution of extracellular matrix proteins, we investigated, immunohistochemically and ultrastructurally, term, first and second trimester human umbilical cords. A differential distribution pattern of the various cytoskeletal proteins of stromal cells and extracellular matrix proteins was observed in different zones of the stroma, the subamniotic stroma, Wharton's jelly, and the vessels' adventitia. All three zones showed immunoreactivities for collagen types I, III and VI and for basement membrane molecules such as collagen type IV, laminin and heparan sulphate proteoglycan. Immunoreactivities for these extracellular matrix molecules were observed around cleft-like territories (stromal clefts) in the Wharton's jelly which were occupied by homogeneous ground substance but void of collagen fibrils and basal lamina molecules. Moreover, between the stromal clefts, slender cells were found which immunohistochemically and ultrastructurally corresponded to various stages of myofibroblastic differentiation. In earlier stages of gestation, stromal cells with a less complex expression pattern prevailed. The stromal clefts and the contractile cells together might serve as a system regulating the turgor of the cord.

Collagen and glycosaminoglycans of Wharton's jelly and their alterations in EPH-gestosis

Some prenatal pathological processes may be caused by biochemical and morphological alterations in the umbilical cord (UC). EPH-gestosis is the most common pregnancy-associated pathological process. For these reasons the role of collagen and glycos-aminoglycans (GAGs) of UC in pathobiochemistry of this syndrome seems to be important. We studied histology of extracellular matrix components, quantity, solubility and molecular polymorphism of collagen, proportional relationships between various types of collagen, the amounts of GAGs and proportional relationships between them in Wharton's jelly of control newborns delivered by healthy mothers and those delivered by mothers with EPH-gestosis. We found that Wharton's jelly is abundant in collagen and GAGs. This collagen is very insoluble and resistant to the action of depolymerizing agents (4% EDTA-Na2, pepsin). Types I, III and V collagens were isolated and quantified. Hyaluronic acid constitutes about 70%, whereas sulphated GAGs constitute about 30% of total GAGs. EPH-gestosis is accompanied by significant increase in sulphated GAGs: hyaluronic acid ratio. The EPH-gestosis-associated alterations in Wharton's jelly correspond to 'premature ageing' of this tissue.