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Kehl D, Görtz S, Wang C, Hoerstrup SP, Bleul U, Weber B. Gestational Age-Dependent Fetal Fluid Dynamics in the Ovine Developmental Model: Establishment of Surrogate Markers for the Differentiation of Stem Cell Origin. Cells Tissues Organs 2019; 206:208-217. [PMID: 31079095 DOI: 10.1159/000499504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 02/26/2019] [Indexed: 11/19/2022] Open
Abstract
The ovine developmental model represents the standard in vivo model for studies involving maternofetal physiology, amniotic fluid (AF) research, and fetal cell therapy prior to human clinical use. Although being close to the human fetal anatomy, 2 separate extraembryonic fluid compartments remain during gestation, known as the amnion and the allantois. A clear distinction between AF versus allantoic fluid (AL) is therefore indispensable for correct scientific conclusions with regard to human translation. In the presented study, the biochemical composition of AF and AL was evaluated in ovine gravid uteri postmortem (n = 31) over the entire gestation. Four parameters, consisting of Na+, Cl-, Mg2+, and total protein, have been found to allow for specific discrimination of the 2 fetal fluids at all gestational phases and therefore as potential surrogate parameters for gestational age. In addition, volumetric changes of the developing fetus and the 2 fetal fluid cavities were analyzed by contrast-enhanced computed tomography (n = 12). AF showed a significant, linear volumetric increase over gestation, whereas AL volume maintained relatively static independent of gestational age. These results serve as a basis for future studies by providing surrogate markers enabling a reliable distinction of isolated fetal fluids and contained cells in the ovine developmental model over the entire gestation.
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Affiliation(s)
- Debora Kehl
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland
| | - Sabrina Görtz
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland
| | - Craig Wang
- Department of Mathematics, University of Zurich, Zurich, Switzerland
| | - Simon P Hoerstrup
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland.,Center for Applied Biotechnology and Molecular Medicine (CABMM), University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland.,Wyss Zurich, University of Zurich, and ETH Zurich, Zurich, Switzerland
| | - Ulrich Bleul
- Clinic of Reproductive Medicine, Department of Farm Animals, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Benedikt Weber
- Institute for Regenerative Medicine (IREM), University of Zurich, Zurich, Switzerland, .,Center for Applied Biotechnology and Molecular Medicine (CABMM), University of Zurich, Zurich, Switzerland, .,Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland, .,Skin and Endothelium Research Division (SERD), Department of Dermatology, Medical University of Vienna, Vienna, Austria,
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Brace RA, Cheung CY, Anderson DF. Regulation of amniotic fluid volume: insights derived from amniotic fluid volume function curves. Am J Physiol Regul Integr Comp Physiol 2018; 315:R777-R789. [PMID: 30024777 DOI: 10.1152/ajpregu.00175.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Recent advances in understanding the regulation of amniotic fluid volume (AFV) include that AFV is determined primarily by the rate of intramembranous absorption (IMA) of amniotic fluid across the amnion and into fetal blood. In turn, IMA rate is dependent on the concentrations of yet-to-be identified stimulator(s) and inhibitor(s) that are present in amniotic fluid. To put these concepts in perspective, this review 1) discusses the evolution of discoveries that form the current basis for understanding the regulation of AFV, 2) reviews the contribution of IMA to this regulation, and 3) interprets experimentally induced shifts in AFV function curves and amnioinfusion function curves in terms of the activity of the amniotic fluid stimulator and inhibitor of IMA. In the early 1980s, it was not known whether AFV was regulated. However, by the late 1980s, IMA was discovered to be a "missing link" in understanding the regulation of AFV. Over the next 25 years the concept of IMA evolved from being a passive process to being an active, unidirectional transport of amniotic fluid water and solutes by vesicles within the amnion. In the 2010s, it was demonstrated that a renally derived stimulator and a fetal membrane-derived inhibitor are present in amniotic fluid that regulate IMA rate and hence are the primary determinants of AFV. Furthermore, AFV function curves and amnioinfusion function curves provide new insights into the relative efficacy of the stimulator and inhibitor of IMA.
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Affiliation(s)
- Robert A Brace
- Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Oregon Health and Science University , Portland, Oregon.,Center for Developmental Health, Knight Cardiovascular Institute, Oregon Health and Science University , Portland, Oregon
| | - Cecilia Y Cheung
- Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Oregon Health and Science University , Portland, Oregon.,Center for Developmental Health, Knight Cardiovascular Institute, Oregon Health and Science University , Portland, Oregon
| | - Debra F Anderson
- Center for Developmental Health, Knight Cardiovascular Institute, Oregon Health and Science University , Portland, Oregon
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Brace RA, Anderson DF, Cheung CY. Regulation of amniotic fluid volume: mathematical model based on intramembranous transport mechanisms. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1260-73. [PMID: 25186112 PMCID: PMC4233290 DOI: 10.1152/ajpregu.00283.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 08/28/2014] [Indexed: 11/22/2022]
Abstract
Experimentation in late-gestation fetal sheep has suggested that regulation of amniotic fluid (AF) volume occurs primarily by modulating the rate of intramembranous transport of water and solutes across the amnion into underlying fetal blood vessels. In order to gain insight into intramembranous transport mechanisms, we developed a computer model that allows simulation of experimentally measured changes in AF volume and composition over time. The model included fetal urine excretion and lung liquid secretion as inflows into the amniotic compartment plus fetal swallowing and intramembranous absorption as outflows. By using experimental flows and solute concentrations for urine, lung liquid, and swallowed fluid in combination with the passive and active transport mechanisms of the intramembranous pathway, we simulated AF responses to basal conditions, intra-amniotic fluid infusions, fetal intravascular infusions, urine replacement, and tracheoesophageal occlusion. The experimental data are consistent with four intramembranous transport mechanisms acting in concert: 1) an active unidirectional bulk transport of AF with all dissolved solutes out of AF into fetal blood presumably by vesicles; 2) passive bidirectional diffusion of solutes, such as sodium and chloride, between fetal blood and AF; 3) passive bidirectional water movement between AF and fetal blood; and 4) unidirectional transport of lactate into the AF. Further, only unidirectional bulk transport is dynamically regulated. The simulations also identified areas for future study: 1) identifying intramembranous stimulators and inhibitors, 2) determining the semipermeability characteristics of the intramembranous pathway, and 3) characterizing the vesicles that are the primary mediators of intramembranous transport.
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Affiliation(s)
- Robert A Brace
- Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology Oregon Health and Science University, Portland, Oregon; and Center for Developmental Health Oregon Health and Science University, Portland, Oregon
| | - Debra F Anderson
- Center for Developmental Health Oregon Health and Science University, Portland, Oregon
| | - Cecilia Y Cheung
- Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology Oregon Health and Science University, Portland, Oregon; and Center for Developmental Health Oregon Health and Science University, Portland, Oregon
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Abstract
Swallowing of amniotic fluid by late gestation fetuses increases when amniotic fluid volume (AFV) is elevated. Our objectives were to quantitatively characterize fetal swallowing when AFV is elevated above normal to polyhydramniotic levels and to explore the mechanisms that mediate these changes. Late gestation fetal sheep were studied under basal conditions and during intra‐amniotic infusion of lactated Ringer's solution. Control AFV averaged 631 ± 214 mL (SE, n = 6), swallowed volume was 299 ± 94 mL/day, and there were 5.7 ± 1.8 bouts/day of rapid swallowing. During intra‐amniotic infusion, AFV (3065 ± 894 mL) and daily swallowed volume (699 ± 148 mL/day) increased (P < 0.05) and the number of bouts reached a maximum of 13.7 ± 2.0 bouts/day when AFV exceeded 1500 mL. Unexpectedly, the volume swallowed per bout (57.3 ± 5.8 mL, n = 102) did not vary with AFV (r = 0.023, P = 0.81). Neither the number of swallows/day nor the volume/swallow changed consistently with elevated AFV. Daily swallowed volume increases and reaches a maximum of twice normal as AFV approaches polyhydramniotic levels. Mechanistically, the increase in swallowing was achieved primarily by an increase in the number of bouts of swallowing per day rather than the expected passive increase in volume per bout. This implies changes in fetal behavior as AFV was elevated. Furthermore, swallowed volume was four times more sensitive to increases in AFV than reported previously. Daily swallowed volume in the ovine fetus varies sharply with changes in amniotic fluid volume around normal and reaches a maximum as amniotic fluid volume exceeds 2000 mL. These changes are mediated by altering the number of bouts of swallowing per day rather than the volume swallowed per bout. Retrograde esophageal flow was normally low but became large as daily swallowed volume increased above 900 mL/day.
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Affiliation(s)
- Robert A Brace
- Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, Oregon
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Brace RA, Cheung CY. Regulation of Amniotic Fluid Volume: Evolving Concepts. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 814:49-68. [DOI: 10.1007/978-1-4939-1031-1_5] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Anderson DF, Jonker SS, Louey S, Cheung CY, Brace RA. Regulation of intramembranous absorption and amniotic fluid volume by constituents in fetal sheep urine. Am J Physiol Regul Integr Comp Physiol 2013; 305:R506-11. [PMID: 23824958 DOI: 10.1152/ajpregu.00175.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Our objective was to test the hypothesis that fetal urine contains a substance(s) that regulates amniotic fluid volume by altering the rate of intramembranous absorption of amniotic fluid. In late gestation ovine fetuses, amniotic fluid volumes, urine, and lung liquid production rates, swallowed volumes and intramembranous volume and solute absorption rates were measured over 2-day periods under control conditions and when urine was removed and continuously replaced at an equal rate with exogenous fluid. Intramembranous volume absorption rate decreased by 40% when urine was replaced with lactated Ringer solution or lactated Ringer solution diluted 50% with water. Amniotic fluid volume doubled under both conditions. Analysis of the intramembranous sodium and chloride fluxes suggests that the active but not passive component of intramembranous volume absorption was altered by urine replacement, whereas both active and passive components of solute fluxes were altered. We conclude that fetal urine contains an unidentified substance(s) that stimulates active intramembranous transport of amniotic fluid across the amnion into the underlying fetal vasculature and thereby functions as a regulator of amniotic fluid volume.
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Affiliation(s)
- Debra F Anderson
- Oregon Health and Science Univ., Heart Research Center, Portland, OR 97239-4501, USA.
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Brace RA, Anderson DF, Cheung CY. Fetal swallowing as a protective mechanism against oligohydramnios and polyhydramnios in late gestation sheep. Reprod Sci 2012; 20:326-30. [PMID: 22872543 DOI: 10.1177/1933719112453510] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
UNLABELLED Our objectives were to (1) quantify the relationship between daily swallowed volume and amniotic fluid volume (AF volume) in late gestation ovine fetuses and (2) use the resulting regression equation to explore the role of swallowing in regulating AF volume. Daily swallowed volume ranged from 36 to 1963 mL/d while experimental AF volume ranged from 160 to 6150 mL (n = 115). Swallowed volume was near zero when AF volume was far below normal, a maximum of 635 ± 41 (standard error) mL/d when AF volume was 1682 ± 31 mL and did not increase further with higher AF volumes. Computer simulations predicted that fetal swallowing would (1) return AF volume to normal in 5 to 6 days following an acute volume change in the absence of changes in other amniotic inflows or outflows and (2) stabilize AF volume in 4 to 8 days following sustained alterations in amniotic inflows or outflows other than swallowing. CONCLUSIONS The volume of AF swallowed each day by the fetus is a strong function of AF volume and reaches a maximum when mild polyhydramnios develops. With deviations in AF volume from normal, changes in fetal swallowing protect against oligohydramnios and polyhydramnios because the changes in swallowing over time reduce the extent of the AF volume change. However, with experimental changes in AF volume stabilizing in 1 to 2 days, it appears that swallowing is not the major regulator of AF volume.
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Affiliation(s)
- Robert A Brace
- Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, OR 97239, USA.
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Cheung CY, Brace RA. Unidirectional transport across cultured ovine amniotic epithelial cell monolayer. Reprod Sci 2010; 15:1054-8. [PMID: 19088374 DOI: 10.1177/1933719108322426] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVE To determine whether ovine amniotic cells in monolayer culture exhibit unidirectional transport. METHODS Permeability of (14)C-inulin was measured in two directions across ovine amniotic cells grown to confluence on cell culture inserts. RESULTS Permeability was 0.69 + 0.17 (SE) microl/min/cm(2) from the top of the insert where the cells were attached to the bottom and 0.11 + 0.02 microl/min/cm(2) in the reverse direction (P < 0.001). Permeability was similar in the two directions for chorionic cells and umbilical vein endothelial cells. Addition of vascular endothelial growth factor did not alter permeability. CONCLUSIONS Transcellular transport in ovine amniotic monolayers is directionally specific. The transport ratio of 6.2:1 for (14)C-inulin is comparable to the in vivo ratio of 4.7:1 for the ovine intramembranous pathway and is consistent with passive diffusion in both directions and vesicular transport in one direction across the monolayer at 5.2 times the rate of passive diffusion.
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Affiliation(s)
- Cecilia Y Cheung
- Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, Oregon 97210, USA
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Gesteland KM, Anderson DF, Davis LE, Robertson P, Faber JJ, Brace RA. Intramembranous solute and water fluxes during high intramembranous absorption rates in fetal sheep with and without lung liquid diversion. Am J Obstet Gynecol 2009; 201:85.e1-6. [PMID: 19398093 DOI: 10.1016/j.ajog.2009.02.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Revised: 12/11/2008] [Accepted: 02/23/2009] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To examine mechanisms that mediate increased intramembranous solute and water absorption. STUDY DESIGN Intramembranous solute and water fluxes were measured in fetal sheep under basal conditions and after intraamniotic infusion of lactated Ringer's solution of 4 L/d for 3 days with and without lung liquid diversion. RESULTS Intramembranous sodium, potassium, chloride, calcium, glucose, and lactate fluxes increased 2.5- to 7.9-fold, were linearly related to volume fluxes (r = 0.83-0.99), and were unaffected by lung liquid. All clearance rates, except that of lactate, increased to equal the intramembranous volume absorption rate during infusion. CONCLUSION Under basal conditions, passive diffusion makes a minor and bulk flow a major contribution to intramembranous solute absorption. During high absorption rates, the increase in solute absorption above basal levels appears to be due entirely to bulk flow and is unaffected by lung liquid. The increased bulk flow is consistent with vesicular transcytosis.
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Affiliation(s)
- Katherine M Gesteland
- Departments of Obstetrics and Gynecology, Oregon Health and Science University, Portland, OR, USA
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Robertson P, Faber JJ, Brace RA, Louey S, Hohimer AR, Davis LE, Anderson DF. Responses of amniotic fluid volume and its four major flows to lung liquid diversion and amniotic infusion in the ovine fetus. Reprod Sci 2009; 16:88-93. [PMID: 19144891 DOI: 10.1177/1933719108324888] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We designed experiments to allow direct measurement of amniotic fluid volume and continuous measurement of lung liquid production, swallowing, and urine production in fetal sheep. From these values, the rate of intramembranous absorption was calculated. Using this experimental design, the contribution of lung liquid to the control of amniotic fluid volume was examined. Fetuses were assigned to 1 of 4 protocols, each protocol lasting 3 days: control, isovolemic replacement of lung liquid, supplementation of amniotic fluid inflow by 4 L/day, and supplementation of amniotic inflow during isovolemic replacement of lung liquid. We found no effect of lung liquid replacement on any of the known flows into and out of the amniotic fluid. Although intramembranous absorption increased greatly during supplementation, the amniochorionic function curves were not altered by isovolemic lung liquid replacement. We conclude that lung liquid does not appear to contain a significant regulatory substance for amniotic fluid volume control.
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Affiliation(s)
- Patricia Robertson
- Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, Oregon 97239, USA.
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Amniotic fluid volume responses to esophageal ligation in fetal sheep: contribution of lung liquid. Am J Obstet Gynecol 2009; 200:313.e1-6. [PMID: 19114273 DOI: 10.1016/j.ajog.2008.10.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Revised: 08/27/2008] [Accepted: 10/07/2008] [Indexed: 11/20/2022]
Abstract
OBJECTIVE The objective of the study was to determine the amniotic fluid volume (AFV) response to fetal esophageal ligation with and without fetal lung liquid entering the amniotic sac. STUDY DESIGN AFV was measured in 3 groups of late-gestation ovine fetuses: time controls, tracheoesophageal shunted, and esophageal ligated. RESULTS One day after surgery, AFV was similar in all groups, averaging 1064 +/- 66 mL. On postsurgical day 9, AFV was unchanged in control fetuses, increased to 3025 +/- 294 mL in fetuses with esophageal ligation and lung liquid shunted into the fetal stomach, and to 3437 +/- 430 mL in fetuses with esophageal ligation and no shunting. CONCLUSION AFV expanded gradually following esophageal ligation to the highest volume thus far reported in noninfused ovine fetuses. Lung liquid entry into the amniotic sac altered neither the time course nor the extent of the AFV increase following esophageal ligation.
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Jonker SS, Anderson DF, Davis LE, Yang Q, Faber JJ, Giraud GD. Persistent changes in arterial blood gases in fetal sheep. Lab Anim 2008; 42:326-30. [PMID: 18625587 DOI: 10.1258/la.2007.06005e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Two anaesthetic protocols were compared using pregnant sheep. In both groups of animals, anaesthesia was induced using an intravenous (i.v.) injection of diazepam and ketamine. The ewes were then intubated for positive pressure ventilation using 0.8 L/min of nitrous oxide and 2 L/min oxygen with 1.1-1.8% halothane. If the ewe showed any signs of awakening, one of two protocols was followed. First, the halothane concentration was increased to 2-3% until the ewe was completely anaesthetized. Second, the halothane concentration was not altered, but the ewe was given doses of i.v. diazepam (0.1 mg/kg) and ketamine (1 mg/kg) until again completely anaesthetized. At the completion of surgery, maternal recovery was rapid and similar between the two groups. However, five days after surgery, the fetal arterial Po(2) and oxygen content of the fetuses receiving additional halothane (1.9 +/- 0.2 kPa and 4.4 +/- 1.0 mL/100 mL) were statistically significantly depressed when compared with the fetuses receiving additional diazepam and ketamine (2.9 +/- 0.1 kPa and 7.0 +/- 0.5 mL/100 mL). These results led us to conclude that certain anaesthetic protocols, in spite of good maternal recovery, can lead to deleterious effects upon the fetus that persist for at least five days after surgery.
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Affiliation(s)
- S S Jonker
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR, USA.
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Liu H, Zheng Z, Wintour E. Aquaporins and Fetal Fluid Balance. Placenta 2008; 29:840-7. [DOI: 10.1016/j.placenta.2008.07.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2008] [Revised: 07/20/2008] [Accepted: 07/24/2008] [Indexed: 01/01/2023]
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