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

Application of ultrasonographic human estimated foetal weight formulas to cynomolgus monkeys (Macaca fascicularis) at 129-132 days of gestation: A comparative study of estimated and actual birthweight

BACKGROUND

Cynomolgus monkeys (Macaca fascicularis) are essential in biomedical research, including reproductive studies. However, the application of human estimated foetal weight (EFW) formulas using ultrasonography (USG) in these non-human primates is not well established.

OBJECTIVES

This study aims to evaluate the applicability of human EFW formulas for estimating foetal weight in cynomolgus monkeys at approximately 130 days of gestation.

METHODS

Our study involved nine pregnant cynomolgus monkeys. We measured foetal parameters, including biparietal diameter, head circumference, abdominal circumference and femur length using USG. The EFW was calculated using 11 human EFW formulas. The actual birthweight (ABW) was recorded following Cesarean section, the day after the EFW calculation. For comparing EFW and ABW, we employed statistical methods such as mean absolute percentage error (APE) and Bland-Altman analysis.

RESULTS

The ABW ranged between 200.36 and 291.33 g. Among the 11 formulas, the Combs formula showed the lowest APE (4.3%) and highest correlation with ABW (p < 0.001). Notably, EFW and ABW differences for the Combs formula were ≤5% in 66.7% and ≤10% in 100% of cases. The Bland-Altman analysis supported these results, showing that all cases fell within the limits of agreement.

CONCLUSIONS

The Combs formula is applicable for estimating the weight of cynomolgus monkey fetuses with USG at approximately 130 days of gestation. Our observations suggest that the Combs formula can be applied in the prenatal care and biomedical research of this species.

Ultrasonographic and macroscopic study of pregnancy in golden hamster

Background

Hamster is widely used as an experimental model in the study of reproductive system. However, pregnancy diagnosis and aging always have been a challenge. ultrasonography have been used in diagnosis of pregnancy in some small laboratory animals, such as rabbits, rats, and mice. Current study describes use of trans-abdominal ultrasonography for pregnancy diagnosis and fetal age estimation in golden hamster. Furthermore, a macroscopic examination was performed to evaluate the embryonic vesicle diameter, crown-rump length, and fetal head diameter. Ten adult female golden hamsters were selected and maintained under controlled light conditions (14 h light/10 h darkness). The estrous cycle was synchronized using eCG and hCG. During estrous (18 h after hCG injection), the hamsters were naturally mated. After seven days of mating, the hamsters were examined daily for pregnancy diagnosis and aging with an ultrasound scanner equipped with an 8.5-MHZ linear probe. On each day of the experiment, at least one of the pregnant hamsters was euthanized and dissected for macroscopic fetal measurements using a digital caliper.

Results

The gestational sac and crown-rump length were identified and measured by ultrasonographicly on day 7 of pregnancy and head could be visible after day 10 of gestation. Statistical analysis revealed that the ultrasound estimation of gestational age was significantly correlated with the actual age of the fetus (r = 0.98; p < 0.05).

Conclusions

Real-time ultrasound can be used for the diagnosis of pregnancy and estimation of fetal age in golden hamster from day 7 of gestation.

Estimation du poids du fœtus zébu peulh à partir de mesures échographiques des paramètres fœtaux

Cette étude vise à estimer le poids du fœtus zébu peulh à partir des mesures échographiques des diamètres de l’abdomen (DA), du bipariétal (DBP), du cordon ombilical (DCO), de la corne utérine (DCU) et des longueurs du fémur (LF), du tibia (LT), et du dos (LD). Elle a concerné soixante et un (n = 61) utérus gravides recueillis après abattage de femelles gestantes. Toutes les gestations étaient simples. Les examens ont été réalisés en bain d’eau au moyen d’une sonde convexe de 3,5 MHz. Les utérus ont été ensuite disséqués afin de rapporté le poids des fœtus au moyen d’une balance. Les données ont été analysées au moyen du système de régression curvilinéaire. Les formules d’estimation du poids à partir des paramètres biométriques ont été de type y = axb, où y est le poids (g), a et b_constantes, et x est le paramètre biomètrique (mm). Toutes les structures morphologiques étudiées ont présenté des corrélations positives et hautement significatives avec le poids du fœtus (p < 0,0001). Toutefois, les DA (R2 = 0,94), DBP (R2 = 0,80), et la LF (R2 = 0,81) semblent être les plus appropriés pour l’estimation du poids du fœtus. À défaut de ces paramètres, les autres structures étudiées peuvent servir de repère dans l’estimation du poids.

Endothelin-1 profiles in advanced maternal age complicated with hypertensive disorders of pregnancy

Recently, advanced maternal age (AMA) has been increasing due to late marriage and assisted reproductive technology. AMA is high-risk pregnancy associated with the life-threatening diseases such as hypertensive disorders of pregnancy (HDP). Recently we have reported novel AMA model mice using aged spontaneous pregnant mice, and found that the phenotypes of AMA model mice reflect the same characteristics as human AMA. We have also demonstrated that atypical angiogenic factors profiles including soluble VEGF-R1 (sFlt-1) and placental growth factor in both AMA pregnant women and AMA model mice. VEGF-endothelin-1 system have been also known as one of HDP-associated factors, however, there has been few reports on the relation between VEGF-endothelin-1 system and AMA. In this study, we investigated the profiles of VEGF-endothelin-1 system using our model mice's samples. As a result, VEGF and endothelin-1 levels were not significantly different between AMA and young individuals. Our results indicated that the mechanisms of hypertension in AMA may differ from those in young individuals from the point of VEGF-endothelin-1 system.

Novel biomarker profiles in experimental aged maternal mice with hypertensive disorders of pregnancy

Recently, advanced maternal age (AMA) has increased in Western countries because of late marriage and advances in assisted reproductive technology. One major complication of AMA is hypertensive disorders of pregnancy (HDP). While clinical investigations into human AMA have been reported, there has been limited information obtained from basic research. In this investigation, we established the AMA mouse model using aged pregnant ICR mice. We demonstrated that the phenotypes of aged pregnant ICR mice reflect the same characteristics as human AMA. The significant findings of our investigation are as follows: (1) The AMA mouse model manifested the same complication phenotypes of human AMA, including maternal obesity, declining fertility, small for gestational age, and a higher rate of intrauterine fetal death; (2) The AMA mouse model exhibited an increasing systolic blood pressure at late gestation (108.2 ± 7.7 vs. 92.7 ± 5.7 mmHg, P < 0.01) that normalized after delivery similar to human HDP patients; and (3) While HDP and placental dysfunction are complicated, AMA mice and human HDP AMA patients manifested a low serum soluble fms-like tyrosine kinase-1 (sFlt-1) level in late gestation (AMA group vs. control group, mice, 16800.0 ± 10709.5 vs. 26611.9 ± 8702.0 pg/mL, respectively, P < 0.01; human, 8507.6 ± 3298.7 vs. 14816.9 ± 5413.5 pg/mL, respectively, P < 0.05). In conclusion, the aged pregnant mouse model resembled human AMA. The AMA mouse model was complicated with HDP despite the low serum sFlt-1 level. Our findings provide evidence that the serum sFlt-1 level does not necessarily reflect the conventional pathogenesis of HDP in aged human and murine pregnancies and may contribute to the future management of HDP in AMA.

A Novel Use of Three-dimensional High-frequency Ultrasonography for Early Pregnancy Characterization in the Mouse

High-frequency ultrasonography (HFUS) is a common method to non-invasively monitor the real-time development of the human fetus in utero. The mouse is routinely used as an in vivo model to study embryo implantation and pregnancy progression. Unfortunately, such murine studies require pregnancy interruption to enable follow-up phenotypic analysis. To address this issue, we used three-dimensional (3-D) reconstruction of HFUS imaging data for early detection and characterization of murine embryo implantation sites and their individual developmental progression in utero. Combining HFUS imaging with 3-D reconstruction and modeling, we were able to accurately quantify embryo implantation site number as well as monitor developmental progression in pregnant C57BL6J/129S mice from 5.5 days post coitus (d.p.c.) through to 9.5 d.p.c. with the use of a transducer. Measurements included: number, location, and volume of implantation sites as well as inter-implantation site spacing; embryo viability was assessed by cardiac activity monitoring. In the immediate post-implantation period (5.5 to 8.5 d.p.c.), 3-D reconstruction of the gravid uterus in both mesh and solid overlay format enabled visual representation of the developing pregnancies within each uterine horn. As genetically engineered mice continue to be used to characterize female reproductive phenotypes derived from uterine dysfunction, this method offers a new approach to detect, quantify, and characterize early implantation events in vivo. This novel use of 3-D HFUS imaging demonstrates the ability to successfully detect, visualize, and characterize embryo-implantation sites during early murine pregnancy in a non-invasive manner. The technology offers a significant improvement over current methods, which rely on the interruption of pregnancies for gross tissue and histopathologic characterization. Here we use a video and text format to describe how to successfully perform ultrasounds of early murine pregnancy to generate reliable and reproducible data with reconstruction of the uterine form in mesh and solid 3-D images.

Three-Dimensional High-Frequency Ultrasonography for Early Detection and Characterization of Embryo Implantation Site Development in the Mouse

Ultrasonography is a powerful tool to non-invasively monitor in real time the development of the human fetus in utero. Although genetically engineered mice have served as valuable in vivo models to study both embryo implantation and pregnancy progression, such studies usually require sacrifice of parous mice for subsequent phenotypic analysis. To address this issue, we used three-dimensional (3-D) reconstruction in silico of high-frequency ultrasound (HFUS) imaging data for early detection and characterization of murine embryo implantation sites and their development in utero. With HFUS imaging followed by 3-D reconstruction, we were able to precisely quantify embryo implantation site number and embryonic developmental progression in pregnant C57BL6J/129S mice from as early as 5.5 days post coitus (d.p.c.) through to 9.5 d.p.c. using a VisualSonics Vevo 2100 (MS550S) transducer. In addition to measurements of implantation site number, location, volume and spacing, embryo viability via cardiac activity monitoring was also achieved. A total of 12 dams were imaged with HFUS with approximately 100 embryos examined per embryonic day. For the post-implantation period (5.5 to 8.5 d.p.c.), 3-D reconstruction of the gravid uterus in mesh or solid overlay format enabled visual representation in silico of implantation site location, number, spacing distances, and site volume within each uterine horn. Therefore, this short technical report describes the feasibility of using 3-D HFUS imaging for early detection and analysis of post-implantation events in the pregnant mouse with the ability to longitudinally monitor the development of these early pregnancy events in a non-invasive manner. As genetically engineered mice continue to be used to characterize female reproductive phenotypes, we believe this reliable and non-invasive method to detect, quantify, and characterize early implantation events will prove to be an invaluable investigative tool for the study of female infertility and subfertility phenotypes based on a defective uterus.

Association of physical performance and biochemical profile of mice with intrinsic endurance swimming

We aimed to investigate the potential mediators and relationship affecting congenital exercise performance in an animal model with physical activity challenge from physiological and biochemical perspectives. A total of 75 male ICR mice (5 weeks old) were adapted for 1 week, then mice performed a non-loading and exhaustive swimming test and were assigned to 3 groups by exhaustive swimming time: low exercise capacity (LEC) (<3 hr), medium exercise capacity (MEC) (3-5 hr), and high exercise capacity (HEC) (>5 hr). After a 1-week rest, the 3 groups of mice performed an exhaustive swimming test with a 5% and 7.5% weight load and a forelimb grip-strength test, with a 1-week rest between tests. Blood samples were collected immediately after an acute exercise challenge and at the end of the experiment (resting status) to evaluate biochemical blood variables and their relation with physical performance. Physical activity, including exhaustive swimming and grip strength, was greater for HEC than other mice. The swimming performance and grip strength between groups were moderately correlated (r=0.443, p<0.05). Resting serum ammonium level was moderately correlated with endurance with a 7.5% weight load (r=-0.447, p<0.05) and with lactate level (r=0.598, p<0.05). The pulmonary morphology of the HEC group seemed to indicate benefits for aerobic exercise. Mice showed congenital exercise performance, which was significantly correlated with different physical challenges and biochemical variable values. This study may have implications for interference in intrinsic characteristics.

Use of real-time ultrasonography as an alternative method for early detection, confirmation and evaluation of rat pregnancy

Researchers sometimes face difficulties in the diagnosis of pregnancy and assessment of embryonic development. Ultrasonography (US) is a non-invasive imaging method with minimal side effects on the subjects or operators. It provides real-time evaluation of the physiology of rapidly moving structures (i.e., heart) and facilitates evaluation of fetal tissue development. US discerns tissues based on composition, making it the imaging method of choice for abdominal examination. In this study we used real-time US as an alternative method for early diagnosis of pregnancy in rats. Sixty-four Wistar rats aged 16-20 wk were examined, and day 8 was the earliest point at which pregnancy could be detected. We constructed a detailed timeline of embryonic features detectable by US on days 8 to 19. We trust this index will be a valuable tool. More refined work toward a more detailed "atlas" will help to reduce animal sacrifice during embryonic development studies.

Establishment of an orthotopic transplantation tumor model of hepatocellular carcinoma in mice

AIM

To improve the outcome of orthotopic transplantation in a mouse model, we used an absorbable gelatin sponge (AGS) in nude mice to establish an orthotopic implantation tumor model.

METHODS

MHCC-97L hepatocellular carcinoma (HCC) cells stably expressing the luciferase gene were injected into the subcutaneous region of nude mice. One week later, the ectopic tumors were harvested and transplanted into the left liver lobe of nude mice. The AGS was used to establish the nude mouse orthotopic implantation tumor model. The tumor suppressor gene, paired box gene 5 (PAX5), which is a tumor suppressor in HCC, was transfected into HCC cells to validate the model. Tumor growth was measured by bioluminescence imaging technology. Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) and histopathology were used to confirm the tumorigenicity of the implanted tumor from the MHCC-97L cell line.

RESULTS

We successfully developed an orthotopic transplantation tumor model in nude mice with the use of an AGS. The success rate of tumor transplantation was improved from 60% in the control group to 100% in the experimental group using AGS. The detection of fluorescent signals showed that tumors grew in all live nude mice. The mice were divided into 3 groups: AGS-, AGS+/PAX5- and AGS+/PAX5+. Tumor size was significantly smaller in PAX5 transfected nude mice compared to control mice (P < 0.0001). These fluorescent signal results were consistent with observations made during surgery. Pathologic examination further confirmed that the tissues from the ectopic tumor were HCC. Results from RT-PCR proved that the HCC originated from MHCC-97L cells.

CONCLUSION

Using an AGS is a convenient and efficient way of establishing an indirect orthotopic liver transplantation tumor model with a high success rate.