Ultrasonic detection and developmental changes in calcification of the placenta during normal pregnancy in mice

Imaging in experimental models of diabetes

Translational medicine, experimental medicine and experimental animal models, in particular mice and rats, represent a multidisciplinary field that has made it possible to achieve, in the last decades, important scientific progress. In this review, we have summarized the most frequently used imaging animal models, such as ultrasound (US), micro-CT, MRI and the optical imaging methods, and their main implications in diagnostic and therapeutic fields, with a particular focus on diabetes mellitus, a multifactorial disease extremely widespread among the general population.

Novel insights from fetal and placental phenotyping in 3 mouse models of Down syndrome

BACKGROUND

In human fetuses with Down syndrome, placental pathology, structural anomalies and growth restriction are present. There is currently a significant lack of information regarding the early life span in mouse models of Down syndrome.

OBJECTIVE

The objective of this study was to examine embryonic day 18.5 and placental phenotype in the 3 most common mouse models of Down syndrome (Ts65Dn, Dp(16)1/Yey, Ts1Cje). Based on prenatal and placental phenotyping in 3 mouse models of Down syndrome, we hypothesized that one or more of them would have a similar phenotype to human fetuses with trisomy 21, which would make it the most suitable for in utero treatment studies.

STUDY DESIGN

Here, C57BL6J/6 female mice were mated to Dp(16)1/Yey and Ts1Cje male mice and Ts65Dn female mice to C57BL/B6Eic3Sn.BLiAF1/J male mice. At embryonic day 18.5, dams were euthanized. Embryos and placentas were examined blindly for weight and size. Embryos were characterized as euploid or trisomic, male or female by polymerase chain reaction. A subset of embryos (34 euploid and 34 trisomic) were examined for malformations.

RESULTS

The Ts65Dn mouse model showed the largest differences in fetal growth, brain development, and placental development when comparing euploid and trisomic embryos. For the Dp(16)1/Yey mouse model, genotype did not impact fetal growth, but there were differences in brain and placental development. For the Ts1Cje mouse model, no significant association was found between genotype and fetal growth, brain development, or placental development. Euploid mouse embryos had no congenital anomalies; however, 1 mouse embryo died. Hepatic necrosis was seen in 6 of 12 Dp(16)1/Yey (50%) and 1 of 12 Ts1Cje (8%) mouse embryos; hepatic congestion or inflammation was observed in 3 of 10 Ts65Dn mouse embryos (30%). Renal pelvis dilation was seen in 5 of 12 Dp(16)1/Yey (42%), 5 of 10 Ts65Dn (50%), and 3 of 12 Ts1Cje (25%) mouse embryos. In addition, 1 Ts65Dn mouse embryo and 1 Dp(16)1/Yey mouse embryo had an aortic outflow abnormality. Furthermore, 2 Ts1Cje mouse embryos had ventricular septal defects. Ts65Dn mouse placentas had increased spongiotrophoblast necrosis.

CONCLUSION

Fetal and placental growth showed varying trends across strains. Congenital anomalies were primarily seen in trisomic embryos. The presence of liver abnormalities in all 3 mouse models of Down syndrome (10 of 34 cases) is a novel finding. Renal pelvis dilation was also common (13 of 34 cases). Future research will examine human autopsy material to determine if these findings are relevant to infants with Down syndrome. Differences in placental histology were also observed among strains.

Tebuconazole exposure disrupts placental function and causes fetal low birth weight in rats

Tebuconazole (TEB) is one of the widely used broad-spectrum triazole fungicides. Its accumulation in mammals leads to various endocrine disruptions. However, it is unclear whether the exposure of TEB during pregnancy affects the growth and development of fetus and placenta. Here, TEB was exposed to pregnant Sprague-Dawley female rats from gestational days 12-21 of 0, 25, 50 or 100 mg/kg for 10 days. TEB reduced placental estradiol levels. TEB disrupted the structure and function of the placenta, leading to hypertrophy, fibrin exudation, edema, calcification, arterial fibroblast proliferation, and trophoblastic infarction. RNA-seq analysis showed that TEB mainly down-regulated the expression of iron transport genes and up-regulated the expression of genes for immune/inflammatory responses. Further qPCR showed that TEB down-regulated Tfrc, Hamp, Eif2ak2 and up-regulated the expression of Cd34, Cd36, Jag1, Pln, Cyp1a1, Esrra, and Aqp1 at 50 and 100 mg/kg. Western blot and semi-quantitative immunohistochemical staining also demonstrated that TEB lowered the levels of TFRC and EIF2AK2 and increased the levels of CD34, CD36, JAG1, CYP1A1, and ESRRA at 50 and 100 mg/kg. In conclusion, TEB severely damages the structure and function of the placenta, leading to hypertrophy of the placenta, low birth weight and feminization of the male fetus possibly via several pathways including iron transport and TNF signaling.

Obstetric Ultrasonography to Detect Fetal Abnormalities in a Mouse Model for Zika Virus Infection

In 2015 Zika virus (ZIKV) emerged for the first time in South America. The following ZIKV epidemic resulted in the appearance of a clinical phenotype with microcephaly and other severe malformations in newborns. So far, mechanisms of ZIKV induced damage to the fetus are not completely understood. Previous data suggest that ZIKV may bypass the placenta to reach the fetus. Thus, animal models for ZIKV infection are important to facilitate studies about ZIKV infection during pregnancy. Here, we used ultrasound based imaging (USI) to characterize ZIKV induced pathogenesis in the pregnant Type I interferon receptor-deficient (IFNAR-/-) mouse model. Based on USI we suggest the placenta to be a primary target organ of ZIKV infection enabling ZIKV spreading to the fetus. Moreover, in addition to direct infection of the fetus, the placental ZIKV infection may cause an indirect damage to the fetus through reduced uteroplacental perfusion leading to intrauterine growth retardation (IUGR) and fetal complications as early as embryonic day (ED) 12.5. Our data confirmed the capability of USI to characterize ZIKV induced modifications in mouse fetuses. Data from further studies using USI to monitor ZIKV infections will contribute to a better understanding of ZIKV infection in pregnant IFNAR-/- mice.

Murine Placental-Fetal Phosphate Dyshomeostasis Caused by an Xpr1 Deficiency Accelerates Placental Calcification and Restricts Fetal Growth in Late Gestation

Phosphorus is a necessary component of all living organisms. This nutrient is mainly transported from the maternal blood to the fetus via the placenta, and insufficient phosphorus availability via the placenta disturbs the normal development of the fetus, especially fetal bone formation in late gestation. Key proteins (phosphate transporters and exporters) that are responsible for the maintenance of placental-fetal phosphorus homeostasis have been identified. A deficiency in the phosphate transporter Pit2 has been shown to result in placental calcification and the retardation of fetal development in mice. What roles does XPR1 (the only known phosphate exporter) play in maintaining placental-fetal phosphorus homeostasis? In this study, we found that Xpr1 expression is strong in the murine placenta and increases with age during gestation. We generated a global Xpr1 knockout mouse and found that heterozygous (Xpr1^+/- ) and homozygous (Xpr1^-/- ) fetuses have lower inorganic phosphate (Pi) levels in amniotic fluid and serum and a decreased skeletal mineral content. Xpr1-deficient placentas show abnormal Pi exchange during gestation. Therefore, Xpr1 deficiency in the placenta disrupts placental-fetal Pi homeostasis. We also discovered that the placentas of the Xpr1^+/- and Xpr1^-/- embryos are severely calcified. Mendelian inheritance statistics for offspring outcomes indicated that Xpr1-deficient embryos are significantly reduced in late gestation. In addition, Xpr1^-/- mice die perinatally and a small proportion of Xpr1^+/- mice die neonatally. RNA sequence (RNA-Seq) analysis of placental mRNA revealed that many of the transcripts are significantly differentially expressed due to Xpr1 deficiency and are linked to dysfunction of the placenta. This study is the first to reveal that XPR1 plays an important role in maintaining placental-fetal Pi homeostasis, disruption of which causes severe placental calcification, delays normal placental function, and restricts fetal growth. © 2019 American Society for Bone and Mineral Research.

Ultrasonographic evaluation of feto-placental tissues at different intrauterine locations in rabbit

The main purpose of examining multiparous species with real-time ultrasonography is to determine the gestational age and make various fetal measurements for early diagnosis of growth anomalies and sibling mismatches. This study investigated changes in fetometric measurements, obstetric Doppler indices and placental image analysis results based on gestational age and fetal location in fetuses located cranially and caudally between 16 and 24 days gestation in 22 healthy pregnant New Zealand rabbits. The first study group consisted of fetuses positioned at the cranial end (n = 22) while the second group consisted of fetuses positioned at the caudal end (n = 22) in each pregnancy. Fetal biparietal head diameter (BPD) and trunk diameter (TD) were measured, and mean grayness values (MGV) were determined from placental image analysis of each fetus. Using Doppler USG, the pulsatile (PI) and resistance (RI) indices of the uterine artery (UtA) and umbilical artery (UmA) were recorded. By the end of the study, BPD and TD values for cranial and caudal fetuses had significantly increased with gestational age (P < 0.001). The MGV values of caudal fetuses were significantly higher (except for the 16th day) (P < 0.05). The UtA PI value of the caudal fetuses was significantly higher (except for the 18th day) (P < 0.01). The UtA RI values of caudal fetuses were significantly higher than cranial ones on the 16 and 24th days (P < 0.05). The PI of the UmA increased until the 20th day before decreasing significantly in both study groups (P < 0.001). The UmA RI value decreased according to the gestational age in both groups (P < 0.001). It was significantly higher in the caudal fetuses on the 20th day (P < 0.05). The somatic rate of all fetuses peaked at the end of the second trimester, although caudal fetuses had higher fetometric values, and this location difference also affected placental echotexture. In both vessels of caudal fetuses, pulsatility and resistance values were higher. The 20th day of pregnancy was a threshold for the Doppler exam results. In conclusion, growth and metabolic status of fetuses located in different uterine locations in healthy pregnant New Zealand rabbits vary. Based on the these growth curves and hemodynamic data, more comprehensive studies of intrauterine life may be possible.

Placenta-specific drug delivery by trophoblast-targeted nanoparticles in mice

Rationale: The availability of therapeutics to treat pregnancy complications is severely lacking, mainly due to the risk of harm to the fetus. In placental malaria, Plasmodium falciparum-infected erythrocytes (IEs) accumulate in the placenta by adhering to chondroitin sulfate A (CSA) on the surfaces of trophoblasts. Based on this principle, we have developed a method for targeted delivery of payloads to the placenta using a synthetic placental CSA-binding peptide (plCSA-BP) derived from VAR2CSA, a CSA-binding protein expressed on IEs.

Methods: A biotinylated plCSA-BP was used to examine the specificity of plCSA-BP binding to mouse and human placental tissue in tissue sections in vitro. Different nanoparticles, including plCSA-BP-conjugated nanoparticles loaded with indocyanine green (plCSA-INPs) or methotrexate (plCSA-MNPs), were administered intravenously to pregnant mice to test their efficiency at drug delivery to the placenta in vivo. The tissue distribution and localization of the plCSA-INPs were monitored in live animals using an IVIS imaging system. The effect of plCSA-MNPs on fetal and placental development and pregnancy outcome were examined using a small-animal high-frequency ultrasound (HFUS) imaging system, and the concentrations of methotrexate in fetal and placental tissues were measured using high-performance liquid chromatography (HPLC).

Results: plCSA-BP binds specifically to trophoblasts and not to other cell types in the placenta or to CSA-expressing cells in other tissues. Moreover, we found that intravenously administered plCSA-INPs accumulate in the mouse placenta, and ex vivo analysis of the fetuses and placentas confirmed placenta-specific delivery of these nanoparticles. We also demonstrate successful delivery of methotrexate specifically to placental cells by plCSA-BP-conjugated nanoparticles, resulting in dramatic impairment of placental and fetal development. Importantly, plCSA-MNPs treatment had no apparent adverse effects on maternal tissues.

Conclusion: These results demonstrate that plCSA-BP-guided nanoparticles could be used for the targeted delivery of payloads to the placenta and serve as a novel placenta-specific drug delivery option.

Foetoplacental communication via extracellular vesicles in normal pregnancy and preeclampsia

Intercellular communication is a critical process in biological mechanisms. During pregnancy foetoplacental tissues release a heterogeneous group of extracellular vesicles (EVs) that include exosomes, microvesicles, apoptotic bodies, and syncytial nuclear aggregates. These vesicles contain a complex cargo (proteins, DNA, mRNA transcripts, microRNAs, noncoding RNA, lipids, and other molecules) that actively participate in the maternal-foetal communication by modulating different processes during gestation for a successful foetal development. Each stage of human gestation is marked by events such as immunomodulation, proliferation, invasion, migration, and differentiation, among others, requiring EVs-mediated signalling to be nearby or distant target cells. Furthermore, EVs also associate with pregnancy pathologies such as preeclampsia and intrauterine growth restriction. This review addresses the role of EVs in human foetomaternal communication in normal pregnancy and preeclampsia.

The alteration in placental volume and placental mean grey value in growth-restricted pregnancies assessed by 3D ultrasound (Growth Restriction & 3D Ultrasonography)

We aimed to evaluate the volumetric and echogenic alterations in placentas between the intrauterine growth restriction (IUGR) and normal pregnancies using three-dimensional ultrasound and virtual organ computer-aided analysis (VOCAL) software. This case-control prospective study consisted of 48 singleton pregnancies complicated by IUGR and 60 healthy singleton pregnancies matched for maternal age, gestational age and parity. Placental volume (PV) and placental volumetric mean grey values (MGV) were evaluated. PV (cm(3)) was analysed using the VOCAL imaging analysis program, and 3D histogram was used to calculate the volumetric MGV (%). PV was 278.50 ± 63.68 and 370.98 ± 97.82 cm(3) in IUGR and control groups, respectively (p = 0.004). MGV of the placenta was 38.24 ± 8.41 and 38.24 ± 8.41 in IUGR and control groups, respectively (p = 0.30). receiver operator curve (ROC) curve analysis revealed that area under curve was 0.731 for PV. Correlation analysis revealed that PV was significantly associated with estimated fetal weight (r = 0.319, p = 0.003), biparietal diameter (r = 0.346, p = 0.002), head circumference (r = 0.269, p = 0.019), abdominal circumference (r = 0.344, p = 0.002) and femur length (r = 0.328, p = 0.004). PV was inversely related to the umbilical artery pulsatility index (r = - 0.244, p = 0.017). To the best of our knowledge, this is the first study evaluating volumetric MGV in IUGR placentas by comparing them with healthy pregnancies. Our study showed that PV diminishes significantly in IUGR pregnancies, whereas volumetric MGV does not alter significantly.

Slc20a2 deficiency results in fetal growth restriction and placental calcification associated with thickened basement membranes and novel CD13 and lamininα1 expressing cells

The essential nutrient phosphorus must be taken up by the mammalian embryo during gestation. The mechanism(s) and key proteins responsible for maternal to fetal phosphate transport have not been identified. Established parameters for placental phosphate transport match those of the type III phosphate transporters, Slc20a1 and Slc20a2. Both members are expressed in human placenta, and their altered expression is linked to preeclampsia. In this study, we tested the hypothesis that Slc20a2 is required for placental function. Indeed, complete deficiency of Slc20a2 in either the maternal or embryonic placental compartment results in fetal growth restriction. We found that Slc20a2 null mice can reproduce, but are subviable; ∼50% are lost prior to weaning age. We also observed that 23% of Slc20a2 deficient females develop pregnancy complications at full term, with tremors and placental abnormalities including abnormal vascular structure, increased basement membrane deposition, abundant calcification, and accumulation of novel CD13 and lamininα1 positive cells. Together these data support that Slc20a2 deficiency impacts both maternal and neonatal health, and Slc20a2 is required for normal placental function. In humans, decreased levels of placental Slc20a1 and Slc20a2 have been correlated with early onset preeclampsia, a disorder that can manifest from placental dysfunction. In addition, preterm placental calcification has been associated with poor pregnancy outcomes. We surveyed placental calcification in human preeclamptic placenta samples, and detected basement membrane-associated placental calcification as well as a comparable lamininα1 positive cell type, indicating that similar mechanisms may underlie both human and mouse placental calcification.

Three-dimensional ultrasonographic placental volume in gestational diabetes mellitus

OBJECTIVES

We aimed to evaluate the placental volume and placental mean gray value in gestational diabetes mellitus (GDM) and healthy placentas using three-dimensional (3D) ultrasound and Virtual Organ Computer-aided AnaLysis (VOCAL).

METHODS

This case-control prospective study consisted of 39 singleton pregnancies complicated by GDM and 42 healthy singleton pregnancies matched for gestational age, maternal age and parity. Placental volume and placental volumetric mean gray values were evaluated. The placental volume (cm(3)) was analyzed using the VOCAL imaging analysis program and 3D histogram was used to calculate the volumetric mean gray value (%).

RESULTS

Placental volume was significantly larger in GDM (411.59 ± 170.82 versus 343.86 ± 128.94 cm(3); p = 0.046). There was no significant difference in mean gray value between GDM and healthy placentas (36.65 ± 7.02 versus 38.71 ± 7.91, respectively; p = 0.277). Placental volume was significantly correlated with gestational week (r = 0.219, p = 0.035) and parity (r = 0.228, p = 0.048). There was negative significant relation between placental volume and umbilical artery systolic/diastolic ratio, pulsatility index and resistance index (r = -0.278, p = 0.007; r = -0.315, p = 0.002; r = -0.322, p = 0.001, respectively).

CONCLUSIONS

Placental volume increases significantly in GDM, whereas mean gray values do not alter significantly. These data may reflect the placental changes in GDM placentas that may help to understand the pathophysiology better.

Three-dimensional placental volume and mean grey value: Normal ranges in a Turkish population and correlation with maternal serum biochemistry and Doppler parameters

The aim of this study is to evaluate the relationship between three-dimensional (3D) ultrasound measurements of placenta at 11-13(6) weeks' gestation and maternal serum levels of pregnancy associated plasma protein-A (PAPP-A), free beta human chorionic gonadotrophin (fβhCG), Doppler parameters in early pregnancy. This prospective study consisted of 334 singleton pregnancies at 11-13(6) weeks' gestation. Placental volume and placental volumetric mean grey values were evaluated. The placental volume (cm(3)) was analysed using the Virtual Organ Computer-aided AnaLysis (VOCAL) imaging program and 3D histogram was used to calculate the volumetric mean grey value (%). Mean maternal age was 28.35 ± 7.55. Mean gestational age was 12.29 ± 0.68 weeks. Placental volume was 77.04 ± 35.74 cm(3). Mean grey value of the placenta was 34.38 ± 8.02%. Correlation analysis revealed that placental volume was significantly correlated with the crown-rump length (r = 0.173, p = 0.002), gestational week (r = 0.116, p = 0.036), ductus venosus pulsatility index (r = -0.101, p = 0.04) and maternal weight (r = 0.099, p = 0.037). There was a significant relation between the mean grey value of the placenta and maternal age (r = 0.131, p = 0.02), nuchal translucency (r = -0.109, p = 0.048), PAPP-A (r = 0.108, p = 0.04) and fβhCG (r = 0.104, p = 0.042). Volumetry of the placenta can be carried out with a high percentage of 1st trimester pregnancies. Volumetry during the 1st trimester could be helpful because of the less advanced state of placentation. This examination is easy to perform and the measurements can be acquired correctly and quickly.

Early detection and staging of spontaneous embryo resorption by ultrasound biomicroscopy in murine pregnancy

BACKGROUND

Embryo resorption is a major problem in human medicine, agricultural animal production and in conservation breeding programs. Underlying mechanisms have been investigated in the well characterised mouse model. However, post mortem studies are limited by the rapid disintegration of embryonic structures. A method to reliably identify embryo resorption in alive animals has not been established yet. In our study we aim to detect embryos undergoing resorption in vivo at the earliest possible stage by ultra-high frequency ultrasound.

METHODS

In a longitudinal study, we monitored 30 pregnancies of wild type C57BI/6 mice using ultra-high frequency ultrasound (30-70 MHz), so called ultrasound biomicroscopy (UBM). We compared the sonoembryology of mouse conceptuses under spontaneous resorption and neighbouring healthy conceptuses and correlated the live ultrasound data with the respective histology.

RESULTS

The process of embryo resorption comprised of four stages: first, the conceptus exhibited growth retardation, second, bradycardia and pericardial edema were observed, third, further development ceased and the embryo died, and finally embryo remnants were resorbed by maternal immune cells. In early gestation (day 7 and 8), growth retardation was characterized by a small embryonic cavity. The embryo and its membranes were ill defined or did not develop at all. The echodensity of the embryonic fluid increased and within one to two days, the embryo and its cavity disappeared and was transformed into echodense tissue surrounded by fluid filled caverns. In corresponding histologic preparations, fibrinoid material interspersed with maternal granulocytes and lacunae filled with maternal blood were observed. In later stages (day 9-11) resorption prone embryos were one day behind in their development compared to their normal siblings. The space between Reichert's membrane and inner yolk sac membrane was enlarged The growth retarded embryos exhibited bradycardia and ultimately cessation of heart beat. Corresponding histology showed apoptotic cells in the embryo while the placenta was still intact. In the subsequent resorption process first the embryo and then its membranes disappeared.

CONCLUSIONS

Our results provide a temporal time course of embryo resorption. With this method, animals exhibiting embryo resorption can be targeted, enabling the investigation of underlying mechanisms before the onset of total embryo disintegration.

Impact of toll-like receptor 4 deficiency on the response to uterine ischemia/reperfusion in mice

Our objective was to determine the role of toll-like receptor 4 (TLR4) in uterine ischemia/reperfusion (I/R)-induced fetal growth restriction (FGR). Pregnant TLR4-deficient and wild-type mice were subjected to I/R or a sham procedure. Fetal and placental weights were recorded and tissues were collected. Pep-1 (inhibits low-molecular-weight hyaluronan (LMW-HA) binding to TLR4) was used to determine whether LMW-HA-TLR4 interaction has a role in FGR. TLR4-deficient mice exhibited significantly lower baseline fetal weights compared with wild-type mice (P<0.05), along with extensive placental calcification that was not present in wild-type mice. Following I/R, fetal and placental weights were significantly reduced in wild-type (P<0.05) but not in TLR4-deficient mice. However, I/R increased fetal loss (P<0.05) only in TLR4-deficient mice. Corresponding with the reduced fetal weights, uterine myeloperoxidase activity increased in wild-type mice (P<0.001), indicating an inflammatory response, which was absent in TLR4-deficient mice. TLR4 was shown to have a regulatory role for two anti-inflammatory cytokines: interferon-B1 decreased only in wild-type mice (P<0.01) and interleukin-10 increased only in TLR4-deficient mice (P<0.001), in response to I/R. Pep-1 completely prevented I/R-induced FGR (P<0.001), indicating a potential role for the endogenous TLR4 ligand LMW-HA in I/R-induced FGR. In conclusion, uterine I/R in pregnancy produces FGR that is dependent on TLR4 and endogenous ligand(s), including breakdown products of HA. In addition, TLR4 may play a role in preventing pregnancy loss after uterine I/R.

Ultrasound determination of gestational age using placental thickness in female dogs: an experimental study

Objective. To verify if the placental thickness allows determining the gestational age, evaluating the correlation between the referred gestational age with the studied one, and the accuracy of the placental thickness measurement (biometry) with fetal morphologic parameters in bitches. Methods. The placental thickness of 336 bitches of diverse breeds was evaluated. Bitches were divided in three groups by body weight: small, medium, and big large size. The gestations pregnancies were evaluated by ultrasound from the third week of gestation. An analysis was performed between the mean values of the gestational age obtained of placental thickness by adjustment of curves and the reported gestational age. Student's t-test was applied to compare the mean of reported and placental thickness gestational age. Significance was defined as P < 0.05. Results. A positive and statistically significant correlation exists between the placental thickness and gestational age. The expression that presents the best correlation coefficient and explanation was thickness of placenta = 0.021x gestational age -0.314. Conclusion. It is possible to determine the gestational age in relation to the placental thickness measured by ultrasound in bitches with a satisfactory accuracy in relation to fetal morphologic parameters as gestational vesicle, ribs, or kidneys.

Estimation of mouse fetal weight by ultrasonography: application from clinic to laboratory

Ultrasonographic assessment of fetal growth to estimate fetal weight has been widely used in clinical obstetrics but not in laboratory mice. Even though it is important to assess fetal growth abnormalities for gene-targeting studies using mice, there have been no reports of accurately estimated fetal weight using fetal biometric parameters in mice. The aim of this study was to establish an accurate mouse formula using fetal biometric parameters under ultrasound imaging. Using a high-frequency ultrasound system with a 40 MHz transducer, we measured 293 fetuses of biparietal diameter and mean abdominal diameter from day 12.5 postcoitus (p.c.) until day 18.5 p.c every day. Thirteen algorithms for humans based on head and/or abdominal measurements were assessed. We established an accurate formula based on measurement of the abdomen in Jcl:ICR mice to investigate gestational complications, such as intrauterine growth restriction.

Association between calcifying nanoparticles and placental calcification

BACKGROUND

The purpose of this study was to examine the possible contribution of calcifying nanoparticles to the pathogenesis of placental calcification.

METHODS

Calcified placental tissues and distal tissue samples were collected from 36 confirmed placental calcification cases. In addition, 20 normal placental tissue samples were obtained as a control group. All the tissue samples were cultured using special nanobacterial culture methods. The cultured calcifying nanoparticles were examined by transmission electron microscopy (TEM), and their growth was monitored by optical density (OD) at a wavelength of 650 nm. 16S rRNA gene expression of the cultured calcifying nanoparticles was also isolated and sequenced.

RESULTS

Novel calcifying nanoparticles wrapped with electron-dense shells between 50 nm to 500 nm in diameter were observed in the extracellular matrix of calcified placental tissues. They were detected in placental villi and hydroxyapatite crystals, and contained "nucleic acid-like materials". After isolation and four weeks of culture, 28 of 36 calcified placental tissue samples showed white granular precipitates attached to the bottom of the culture tubes. OD(650) measurements indicated that the precipitates from the calcified placental tissues were able to grow in culture, whereas no such precipitates from the control tissues were observed. The 16S rRNA genes were isolated from the cultured calcifying nanoparticles and calcified placental tissues, and their gene sequencing results implied that calcifying nanoparticles were novel nanobacteria (GenBank JF823648).

CONCLUSION

Our results suggest that these novel calcifying nanoparticles may play a role in placental calcification.

A comparison of the imaging performance of high resolution ultrasound scanners for preclinical imaging

Nine ultrasound transducers from six ultrasound scanners were assessed for their utility for preclinical ultrasound imaging. The transducers were: L8-16, L10-22 (Diasus; Dynamic Imaging Ltd., Livingston, UK); L17-5, L15-7io (iU22; Philips, Seattle, WA, USA), HFL38/13-6 (MicroMaxx; Sonosite Inc., Bothell, WA, USA); il3Lv (Vivid 5; GE, Fairfield, CT, USA), RMV 704 (Vevo 770; Visualsonics Inc., Toronto, Canada) and MS550S, MS550D (Vevo 2100; Visualsonics Inc.). A quantitative analysis of the ultrasound images from all nine transducers employed measurements of the resolution integral as an indication of the versatility and technology of the ultrasound scanners. Two other parameters derived from the resolution integral, the characteristic resolution and depth of field, were used to characterise imaging performance. Six of these transducers were also assessed qualitatively by ultrasonically scanning 59 female common marmosets (Callithrix jacchus) yielding a total of 215 scans. The quantitative measurements for each of the transducers were consistent with the results obtained in the qualitative in vivo assessment. Over a 0-10 mm imaging depth, the values of the resolution integral, characteristic resolution and depth of field, measured using the Edinburgh Pipe Phantom, ranged in magnitude from 7-72, 93-930 μm and 3.3-9.2 mm respectively. The largest resolution integrals were obtained using the Vevo 770 and Vevo 2100 scanners. The Edinburgh Pipe Phantom provides a quantitative method of characterising the imaging performance of preclinical imaging scanners.

The effect of insulin signaling on female reproductive function independent of adiposity and hyperglycemia

Physiological states of insulin resistance such as obesity and diabetes have been linked to abnormalities in female reproductive function. However, it is difficult to distinguish the direct effects of impaired insulin signaling from those of adiposity or hyperglycemia because these conditions often coexist in human syndromes and animal models of insulin resistance. In this study, we used lean, normoglycemic mouse lines with differing degrees of hyperinsulinemia and insulin receptor (Insr) expression to dissect the effects of altered insulin signaling on female reproduction. All three mouse lines [Ttr-Insr(-/-), Insr(+/-), and Insr(+/+) (wild type)] are able to maintain fertility. However, the insulin-resistant and hyperinsulinemic mice demonstrate altered duration of estrous cycles as well as aberrant distribution and morphology of ovarian follicles. These effects appear to be independent of hyperandrogenism in the mice. Pregnancy studies indicate decreased success in early progression of gestation. In successful pregnancies, decreased embryo weights and increased placental calcification also implicate altered insulin signaling in later gestational effects. Thus, abnormal insulin signaling, independent of adipose tissue mass, adipokine expression levels, and hyperglycemia, can affect parameters of the female hypothalamic-pituitary-gonadal axis and pregnancy outcomes.

In vivo quantification of embryonic and placental growth during gestation in mice using micro-ultrasound

BACKGROUND

Non-invasive micro-ultrasound was evaluated as a method to quantify intrauterine growth phenotypes in mice. Improved methods are required to accelerate research using genetically-altered mice to investigate the interactive roles of genes and environments on embryonic and placental growth. We determined (1) feasible age ranges for measuring specific variables, (2) normative growth curves, (3) accuracy of ultrasound measurements in comparison with light microscopy, and (4) weight prediction equations using regression analysis for CD-1 mice and evaluated their accuracy when applied to other mouse strains.

METHODS

We used 30-40 MHz ultrasound to quantify embryonic and placental morphometry in isoflurane-anesthetized pregnant CD-1 mice from embryonic day 7.5 (E7.5) to E18.5 (full-term), and for C57Bl/6J, B6CBAF1, and hIGFBP1 pregnant transgenic mice at E17.5.

RESULTS

Gestational sac dimension provided the earliest measure of conceptus size. Sac dimension derived using regression analysis increased from 0.84 mm at E7.5 to 6.44 mm at E11.5 when it was discontinued. The earliest measurement of embryo size was crown-rump length (CRL) which increased from 1.88 mm at E8.5 to 16.22 mm at E16.5 after which it exceeded the field of view. From E10.5 to E18.5 (full term), progressive increases were observed in embryonic biparietal diameter (BPD) (0.79 mm to 7.55 mm at E18.5), abdominal circumference (AC) (4.91 mm to 26.56 mm), and eye lens diameter (0.20 mm to 0.93 mm). Ossified femur length was measureable from E15.5 (1.06 mm) and increased linearly to 2.23 mm at E18.5. In contrast, placental diameter (PD) and placental thickness (PT) increased from E10.5 to E14.5 then remained constant to term in accord with placental weight. Ultrasound and light microscopy measurements agreed with no significant bias and a discrepancy of less than 25%. Regression equations predicting gestational age from individual variables, and embryonic weight (BW) from CRL, BPD, and AC were obtained. The prediction equation BW = -0.757 + 0.0453 (CRL) + 0.0334 (AC) derived from CD-1 data predicted embryonic weights at E17.5 in three other strains of mice with a mean discrepancy of less than 16%.

CONCLUSION

Micro-ultrasound provides a feasible tool for in vivo morphometric quantification of embryonic and placental growth parameters in mice and for estimation of embryonic gestational age and/or body weight in utero.

L’échographie haute résolution de la souris

Small-animal ultrasound imaging has been made possible using high-resolution imaging devices. The spatial resolution is therefore sufficient to accurately measure anatomical parameters in mice. This paper reviews some of the main applications of high-resolution ultrasound imaging of the mouse and highlights what could be the forthcoming advances.

Imaging tools for the developmental biologist: ultrasound biomicroscopy of mouse embryonic development

Progress has been rapid in the elucidation of genes responsible for cardiac development. Strategies to ascertain phenotypes, however, have lagged behind advances in genomics, particularly in the in vivo mouse embryo, considered a model organism for mammalian development, and for human development and disease. Over the past several years, our laboratory and others have pioneered a variety of ultrasound biomicroscopy (UBM)-Doppler approaches to study in vivo development in both normal and mutant mouse embryos. This state-of-the-art review will discuss the development and potential of ultrasound biomicroscopy as a tool for the in vivo imaging and phenotyping of both cardiac and non-cardiac organ systems in the early developing mouse. Broad, long-term research objectives are to define living structure-function relationships during critical periods of mammalian morphogenesis.

High resolution ultrasound-guided microinjection for interventional studies of early embryonic and placental development in vivo in mice

Background

In utero microinjection has proven valuable for exploring the developmental consequences of altering gene expression, and for studying cell lineage or migration during the latter half of embryonic mouse development (from embryonic day 9.5 of gestation (E9.5)). In the current study, we use ultrasound guidance to accurately target microinjections in the conceptus at E6.5–E7.5, which is prior to cardiovascular or placental dependence. This method may be useful for determining the developmental effects of targeted genetic or cellular interventions at critical stages of placentation, gastrulation, axis formation, and neural tube closure.

Results

In 40 MHz ultrasound images at E6.5, the ectoplacental cone region and proamniotic cavity could be visualized. The ectoplacental cone region was successfully targeted with 13.8 nL of a fluorescent bead suspension with few or no beads off-target in 51% of concepti microinjected at E6.5 (28/55 injected). Seventy eight percent of the embryos survived 2 to 12 days post injection (93/119), 73% (41/56) survived to term of which 68% (38/56) survived and appeared normal one week after birth. At E7.5, the amniotic and exocoelomic cavities, and ectoplacental cone region were discernable. Our success at targeting with few or no beads off-target was 90% (36/40) for the ectoplacental cone region and 81% (35/43) for the exocoelomic cavity but tended to be less, 68% (34/50), for the smaller amniotic cavity. At E11.5, beads microinjected at E7.5 into the ectoplacental cone region were found in the placental spongiotrophoblast layer, those injected into the exocoelomic cavity were found on the surface or within the placental labyrinth, and those injected into the amniotic cavity were found on the surface or within the embryo. Following microinjection at E7.5, survival one week after birth was 60% (26/43) when the amniotic cavity was the target and 66% (19/29) when the target was the ectoplacental cone region. The survival rate was similar in sham experiments, 54% (33/61), for which procedures were identical but no microinjection was performed, suggesting that surgery and manipulation of the uterus were the main causes of embryonic death.

Conclusion

Ultrasound-guided microinjection into the ectoplacental cone region at E6.5 or E7.5 and the amniotic cavity at E7.5 was achieved with a 7 day postnatal survival of ≥60%. Target accuracy of these sites and of the exocoelomic cavity at E7.5 was ≥51%. We suggest that this approach may be useful for exploring gene function during early placental and embryonic development.