Trophic effect of amniotic fluid on cultured fetal gastric mucosal cells

Unexplained fetal death is associated with increased concentrations of anti-angiogenic factors in amniotic fluid

OBJECTIVE

Angiogenesis is critical for successful pregnancy. An anti-angiogenic state has been implicated in preeclampsia, fetal growth restriction and fetal death. Increased maternal plasma concentrations of the anti-angiogenic factor, soluble vascular endothelial growth factor receptor (sVEGFR)-1, have been reported in women with preeclampsia and in those with fetal death. Recent observations indicate that an excess of sVEGFR-1 and soluble endoglin (sEng) is also present in the amniotic fluid of patients with preeclampsia. The aim of this study was to determine whether fetal death is associated with changes in amniotic fluid concentrations of sVEGFR-1 and sEng, two powerful anti-angiogenic factors. Study design. This cross-sectional study included patients with fetal death (n = 35) and controls (n = 129). Fetal death was subdivided according to clinical circumstances into: (1) unexplained (n = 25); (2) preeclampsia and/or placental abruption (n = 5); and (3) chromosomal/congenital anomalies (n = 5). The control group consisted of patients with preterm labor (PTL) who delivered at term (n = 92) and women at term not in labor (n = 37). AF concentrations of sVEGFR-1 and sEng were determined by ELISA. Non-parametric statistics and logistic regression analysis were applied. Results. (1) Patients with a fetal death had higher median amniotic fluid concentrations of sVEGFR-1 and sEng than women in the control group (p < 0.001 for each); (2) these results remained significant among different subgroups of stillbirth (p < 0.05 for each); and (3) amniotic fluid concentrations of sVEGFR-1 and those of sEng above the third quartile were associated with a significant risk of unexplained preterm fetal death (adjusted OR = 10.8; 95%CI 1.3-89.2 and adjusted OR 87; 95% CI 2.3-3323, respectively). Conclusion. Patients with an unexplained fetal death at diagnosis are characterized by an increase in the amniotic fluid concentrations of sVEGFR-1 and sEng. These observations indicate that an excess of anti-angiogenic factors in the amniotic cavity is associated with unexplained fetal death especially in preterm gestations.

Novel mechanism of human fetal growth regulation: a potential role of lanugo, vernix caseosa and a second tactile system of unmyelinated low-threshold C-afferents

Novel hypothesis of human fetal growth regulation in amniotic fluid environment integrates lanugo, vernix caseosa and a second tactile system of unmyelinated low-threshold C-afferents - all three forming a unique natural instrument powerfully speeding fetal growth during mid-gestation and lowering its tempo at the end of gestation. Repeated oscillations of lanugo hairs encased by vernix caseosa during fetal movements in amniotic fluid activate highly sensitive mechanoreceptors connected to unmyelinated C-afferents, which prime function is to conduct originated impulses from all fetal skin dermatoms via spinal cord and to activate vagal sensory zone, hypothalamus and insular cortex, for concomitant promotion of the anti-stress effect through oxytocin release, and stimulation of fetal growth by the incretin effect of gastrointestinal hormones.

Host factors in amniotic fluid and breast milk that contribute to gut maturation

The gut represents a complex organ system with regional differences, which reflect selective digestive and absorptive functions that change constantly in response to bodily requirements and the outside milieu. As a barrier to the external environment, gut epithelium must be renewed rapidly and repeatedly. Growth and renewal of gut epithelial cells is dependent on controlled cell stimulation and proliferation by a number of signaling processes and agents, including gut peptides-both endogenous and exogenous sources. This cascade of events begins during fetal development; with the ingestion of amniotic fluid, this process is enhanced and continued during infancy and early childhood through the ingestion of human milk. Events influenced by amniotic fluid during fetal development and those influenced by human milk that unfold after birth and early childhood to render the gut mature are presented.

Trophic effect of multiple growth factors in amniotic fluid or human milk on cultured human fetal small intestinal cells

OBJECTIVES

To evaluate the role of growth factors in amniotic fluid and in human milk on gastrointestinal adaptation of the fetus and very low-birth-weight infants, the effects of these fluids and multiple growth factors were investigated in a human fetal small intestinal cell line (FHs 74 Int).

METHODS

After FHs 74 Int cells were incubated with amniotic fluid, human milk, or recombinant growth factors, growth-promoting activity was measured by [3H]-thymidine incorporation into cells.

RESULTS

Incubating cells with amniotic fluid or human milk promoted growth dose dependently. Genistein almost completely inhibited growth-promoting activity in amniotic fluid P = 0.002), and growth was partially inhibited by antibodies against epidermal growth factor (EGF) (P = 0.047), insulin-like growth factor-1 (IGF-1, P = 0.047), or fibroblast growth factor (FGF, P = 0.014). This activity in human milk was inhibited almost completely by genistein (P < 0.0001) and partially inhibited by antibodies against EGF (P = 0.036), IGF-1 (P = 0.009), FGF (P = 0.004), hepatocyte growth factor (HGF, P = 0.001), or transforming growth factor-alpha (TGF-alpha, P = 0.001). Although recombinant EGF, IGF-1, FGF, HGF, and TGF-alpha elicited a synergistic trophic response on cultured cells, the response was much less than with amniotic fluid or with human milk.

CONCLUSION

In aminiotic fluid and in human milk, EGF, IGF-1, FGF, HGF, and TGF-alpha have a strong trophic effect on immature intestinal cells and may be involved in perinatal gastrointestinal adaptation.

Esophageal atresia with tracheoesophageal fistula: suggested mechanism in faulty organogenesis

BACKGROUND/PURPOSE

The organogenesis of esophageal atresia with tracheoesophageal fistula (EA-TEF) is unknown. Using an established model for EA-TEF in rats, the authors proposed to study this aberrancy of development in the hope of gaining insight into its mechanism of formation.

METHODS

Pregnant Sprague-Dawley rats were injected with 2.2 mg/kg of Adriamycin intraperitoneally on days 6 through 9 of gestation. Using microdissection, the trachea, blind-ending esophagus, TEF, and stomach were isolated from embryos of various gestional ages. The specimens were analyzed histologically with routine H&E staining.

RESULTS

The classic EA-TEF developed in the embryos, with proximal EA and distal TEF. As expected, the atresia formed as a blind-ending pouch, but the distal fistula began as an apparent equal trifurcation of the tracheal anlage into two mainstem bronchi and the fistula tract leading to the stomach. Histological analysis of the fistula tract showed respiratorylike pseudostratified columnar epithelium.

CONCLUSIONS

TEF develops as the middle branch of a tracheal trifurcation. EA-TEF occurs by a primary atresia of the esophagus. As a secondary phenomenon, the distal foregut anlage is switched toward the pulmonary phenotype. It trifurcates, and its middle branch grows caudally to fistulize into the stomach.

Inhibition of fibroblast-populated collagen lattice contraction by an albumin-bound lipid fraction in human amniotic fluid

Human amniotic fluid inhibits the contraction of fibroblast-populated collagen lattices. Amniotic fluid of 21 weeks' gestation was previously reported to have peak inhibiting activity. An attempt to isolate the inhibitory factor(s) from human amniotic fluid employing a molecular sieving column demonstrated an inhibitory factor near 70,000 molecular weight (repeated three times with triplicate samples). Since albumin has a molecular weight of 68,000 and is in high concentration in amniotic fluid, the removal of albumin by an Affi-Gel Blue (an albumin binding affinity column) was the first step in the purification scheme. The bound human amniotic fluid albumin fraction was eluted from the Affi-Gel Blue column, and the unexpected finding was that this fraction inhibited fibroblast-populated collagen lattice contraction (three repetitions in duplicate). We previously showed that prostaglandins and saturated and unsaturated fatty acids affect fibroblast-populated collagen lattice contraction, and albumin is a carrier for lipids. The eluted albumin fraction was separated into its protein and lipid components. The lipid-free albumin fraction had no fibroblast-populated collagen lattice contraction inhibiting activity (run four times in duplicate). The isolated lipid fraction inhibited fibroblast-populated collagen lattice contraction in a dose-responsive manner (repeated twice in triplicate). It was demonstrated that lipid bound to albumin isolated from human amniotic fluid inhibited fibroblast-populated collagen lattice contraction.

Isolated fetal mouse limbs: gestational effects on tissue repair in an unperfused system

While it is known that adult tissue repair is tightly regulated through local effects in the wound environment mediated by circulating blood elements such as platelets, white cells, cytokines, and hormones, the degree to which each is required in fetal tissue repair is uncertain. This raises the following questions regarding regulation of fetal tissue repair: (1) is the local wound matrix alone sufficient to sustain fetal tissue repair in the same regenerative manner seen in previous in vivo whole animal studies? (2) Will it occur only during the period of rapid fetal growth and development in early and mid gestation? To address these fundamental questions, an organ culture system has been designed to grow isolated, unperfused, developing fetal mouse limbs in a chemically defined, serum-free media. Amputated fetal mouse forelimbs (n > or = 10) were wounded with linear incisions at gestational days 14, 16, and 18 (term = 19); the wounds were closed primarily. These amputated and wounded limbs were placed on steel grids in organ culture petri dishes, then partially submerged in a chemically defined, serum-free media. The limbs were grown at 37 degrees C in humidified 95% air/5% CO2 for 1 week. These wounded limbs were examined histologically at days 0, 3, and 7 postwounding to determine their viability and whether or not tissue repair occurred. In the 14-day group, limb growth and differentiation was evident during the incubation period. Normal dermal and epidermal architecture was restored at the wound site without abundant collagen deposition by day 7 postwounding.(ABSTRACT TRUNCATED AT 250 WORDS)

Altered intestinal development after jejunal ligation in fetal sheep

Experimental obstruction of the fetal small intestine resulted in massive hypertrophy of the segment proximal to the site of obstruction. Villus morphology was grossly abnormal. Enterocytes developed many irregular features, most notably cytoplasmic extensions (pseudopods, or blebs) from their apical surface. Distal to the site of obstruction, morphological anomalies which resembled those seen after experimental oesophageal ligation were found. These included delayed disappearance of the apical endocytic network, disrupted or absent microvilli, glycogen accumulation and inappropriate cell extrusion. Proximal to the obstruction, where stasis of swallowed fluid occurs, distension and abnormal intestinal development ensues. Distal to the obstruction where the intestine develops in the absence of swallowed fluid, development is also abnormal. The anomalies resemble those noted after oesophageal ligation in utero, and possibly are the results of reduced cellular nutrition. These results suggest that fetal ingestion provides the developing gastrointestinal tract with an important stimulus for normal growth.

Is fetal enteral nutrition important for normal gastrointestinal growth?: a discussion

Long-term total parenteral nutrition results in atrophy of small intestinal structure and function. Maintenance or re-establishment of enteral nutrition can prevent or redress this loss. Paradoxically, the fetus develops in a total parenteral nutrition environment, but at the same time must achieve appropriate levels of gastrointestinal maturation in readiness for enteral feeding soon after birth. The fetus swallows large amounts of fluid during life in utero and growth is arrested if fetal ingestion is impaired. It is possible therefore that enteral nutrition provided by fetal swallowing is just as important in ensuring normal gastrointestinal homeostasis and growth in the fetus as it is in the adult.

Ultrastructural anomalies in the fetal small intestine indicate that fetal swallowing is important for normal development: an experimental study

Fetal swallowing is established early in development and if fetal ingestion is prevented, the gastrointestinal (GI) tract fails to grow normally. In this article we describe the ultrastructural features of GI tissues developing in the absence of swallowing, in the fetal sheep. We have noted a number of defects in enterocyte morphology. These include abnormal or absence of microvilli, inappropriate cell extrusion, glycogen accumulation and altered lysosomal morphology. Many of these changes resemble those seen in malnourished infants. It is possible that fetal ingestion provides a significant source of nutrients, ensuring adequate GI tract growth in utero, in addition to specific growth factors which may be present in ingested fluid.

The role of the kidney in lung growth and maturation in the setting of obstructive uropathy and oligohydramnios

The contribution of the kidneys to lung development, which includes growth and maturation, is uncertain but it appears to be complex. Obstructive uropathy with oligohydramnios produces pulmonary hypoplasia characterized by small lungs (decreased lung volume/body weight) and retarded maturation (reduced total airspace). Lung growth and maturation were studied in a model of early gestation obstructive uropathy to understand better their relationship and their prenatal regulation. Of 26 fetal sheep studied at near term (135 days of gestation) 9 had bladder obstruction created at 60 days of gestation, 11 had bladder obstruction at 60 days with in utero decompression at 95 days, and 6 served as controls and shams. Amniotic fluid volume was measured, kidneys were prepared and evaluated histologically, lungs were inflation-fixed and volumes were measured, and airspace volume percentage was measured morphometrically. Experimental and serendipitous variations in the condition of the kidneys and amniotic fluid at delivery permitted an analysis of the contribution of the kidneys and the amniotic fluid to lung growth and maturation. Impairment of growth and maturation was dissociated in certain animals, and this dissociation was referable to the histological status of the kidneys and the presence or absence of amniotic fluid at delivery. Growth was normal when amniotic fluid was present or likely to have been present in late gestation, even with structurally damaged kidneys. With severe renal damage amniotic fluid was not restored even with in utero decompression and it resulted in severely impaired lung growth. Maturation was normal only in the presence of amniotic fluid and intact kidneys. The dissociation of lung growth and structural maturity suggests their independent regulation. The data suggest that the kidneys are important in early lung growth, while the presence of amniotic fluid contributes to growth later in gestation. Lung maturity requires both factors, suggesting a primary kidney contribution with the amniotic fluid acting in a permissive or supportive role.

Uptake and distribution of continuously infused intraamniotic nutrients in fetal rabbits

Nutrient delivery via the fetal gastrointestinal tract may be a potential prenatal treatment for intrauterine growth retardation. Uptake from continuous intraamniotic infusions with nutrient incorporation into developing fetal tissues has not previously been shown. To study this, ovarian-end fetuses of 18 time-mated rabbit does underwent amniotic cavity catheterization and either esophageal ligation (EL) or sham operation (SH) on gestational day 23 (term, 33 days). Saline plus 14C D-glucose and 3H proline were infused into the amniotic fluid for 4 days. Nutrients absorbed by the EL fetus represent only those taken up into the maternal circulation and subsequently redelivered hematogenously to the fetus. Radioactivity of fetal blood and organs was determined using a liquid scintillation counter. All infused does and 10 of 18 infused fetuses (56%) survived the entire study period. In SH fetuses, uptake of 14C per mg of tissue was highest in the lung and significantly greater in the stomach, jejunum, ileum, and lung than in fetal blood (P less than .05). Uptake of 3H per mg of tissue was also highest in the lung and significantly greater than fetal blood in the stomach, small intestine, lung, and liver (P less than .05). Each organ's 14C and 3H uptake was greater in SH than in EL fetuses (P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)