Use of urinary 13,14, dihydro-15-keto-prostaglandin F2α (PGFM) concentrations to diagnose pregnancy and predict parturition in the giant panda (Ailuropoda melanolecua)

MicroRNA expression profiles in plasma exosomes of late pregnant giant pandas

BACKGROUND

MicroRNAs can regulate various biological functions including cell proliferation, differentiation, embryo formation, and implantation. The giant panda exhibits embryonic diapause, with embryo development resuming in late pregnancy. However, the changes in microRNAs during late pregnancy remain poorly understand.

METHODS AND RESULTS

After mating, plasma samples were collected on day 40 of early pregnancy (EP; n = 3) and 30 days before delivery of late pregnancy (LP; n = 3). Following microRNAs screening, a total of 120 microRNAs were detected in the plasma exosomes of pregnant pandas. Nine differentially expressed microRNAs (DEmicroRNAs) were identified in LP compared to EP, including three that were upregulated and six that were downregulated. Notably, miR-25b and miR-47 were significantly downregulated in LP group. All DEmicroRNAs were predicted to target a total of 2,675 genes. Pathway enrichment analysis of these target genes revealed significant enrichment in the MAPK and Rap1 signaling pathways, which are closely related to cell proliferation, differentiation, and cell-cell and cell-matrix interactions. Analysis of protein-protein interaction networks showed that most of the hub genes (five out of eight), including Fgfr1, Fgf2, Fgf18, Erbb4, and Kras within the MAPK and Rap1 pathways are associated with the cell proliferation and differentiation. Significantly, Erbb4 was regulated by significantly differentially expressed miRNA-47.

CONCLUSIONS

We suggest that plasma exosomal microRNAs are involved in cell proliferation and differentiation during embryonic development by regulating key hub genes within MAPK and Rap1 pathways. These findings provided new insights into the development of giant panda embryos.

Development and validation of a versatile non-invasive urinary steroidomics method for wildlife biomonitoring

Wildlife conservation is often challenged by a lack of knowledge about the reproduction biology and adaptability of endangered species. Although monitoring steroids and related molecules can increase this knowledge, the applicability of current techniques (e.g. immunoassays) is hampered by species-specific steroid metabolism and the requisite to avoid invasive sampling. This study presents a validated steroidomics method for the (un)targeted screening of a wide range of sex and stress steroids and related molecules in urine using ultra-high performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS). In total, 50 steroids (conjugated and non-conjugated androgens, estrogens, progestogens and glucocorticoids) and 6 prostaglandins could be uniquely detected. A total of 45 out of 56 compounds demonstrated a detection limit below 0.01 ng μL-1. Excellent linearity (R2 > 0.99), precision (CV < 20 %), and recovery (80-120 %) were observed for 46, 41, and 39 compounds, respectively. Untargeted screening of pooled giant panda and human samples yielded 9691 and 8366 features with CV < 30 %, from which 84.1 % and 83.0 %, respectively, also demonstrated excellent linearity (R2 > 0.90). The biological validity of the method was investigated on male and female giant panda urine (n = 20), as well as pooled human samples (n = 10). A total of 24 different steroids were detected with clear qualitative and quantitative differences between human and giant panda samples. Furthermore, expected differences were revealed between female giant panda samples from different reproductive phases. In contrast to traditional biomonitoring techniques, the developed steroidomics method was able to screen a wide range of compounds and provide information on the putative identities of metabolites potentially important for reproductive monitoring in giant pandas. These results illustrate the advancements steroidomics brings to the field of wildlife biomonitoring in the pursuit to better understand the biology of endangered species.

Label-Free Quantification (LFQ) of Fecal Proteins for Potential Pregnancy Detection in Polar Bears

Reliable pregnancy diagnostics would be beneficial for monitoring polar bear (Ursus maritimus) populations both in situ and ex situ, but currently there is no method of non-invasive pregnancy detection in this species. Recent reports in several carnivore species described the identification of fecal proteins that may serve as pregnancy biomarkers; however, repeatability has been limited. The objective of the current analysis was to utilize an unbiased, antibody-free, label-free method for the identification and quantification of fecal proteins to determine if differences associated with pregnancy are detectable in polar bears. Protein was extracted from fecal samples (n = 48) obtained from parturient (n = 6) and non-parturient (n = 6) profiles each at four timepoints: pre-breeding season, embryonic diapause, early placental pregnancy, and mid-placental pregnancy. Protein was prepared and analyzed on the Thermo Orbitrap Eclipse nanoLC-MS/MS system. A total of 312 proteins was identified and quantified; however, coefficients of variation (CV) were high for both abundance ratio variability (384.8 ± 61.0% SEM) and within group variability (86.8 ± 1.5%). Results of this study suggest that the inconsistencies in specific protein concentrations revealed previously by antibody-based assays may not be due to that methodology’s limitations, but rather, are reflective of true variation that exists among samples.

Luteal phase length, endometrial edema, and behavior differentiate post-ovulatory events in a giant panda (Ailuropoda melanoleuca)

Despite decades of reproductive research on the giant panda (Ailuropoda melanoleuca), the post-ovulatory phase continues to confound zoologists in conservation and breeding centers around the world, often resulting in significant investments of time and resources without reproductive success. The purpose of this project was to document and compare post-ovulatory characteristics during a non-productive and productive breeding in the same individual in consecutive years. A multidisciplinary approach was used to monitor the visiting female giant panda at the Toronto Zoo through the luteal phase of her first two full reproductive cycles in 2014 and 2015. Monitoring occurred via urine-endocrine analysis, weekly ultrasound examinations, and continuous behavioral observations. The 2014 reproductive cycle consisted of a pseudopregnancy, characterized by an extended luteal phase (241 days), the identification of endometrial edema and folding during ultrasound examinations, and a lack of strong association between behavior patterns and urinary progestagen secretion. The 2015 reproductive cycle included increased feeding time through the primary progestagen rise compared to the previous year, followed by simultaneous decrease in appetite and increases in inactivity, resting, sitting upright, and pre-partum-associated behaviors. These changes began 25 days before the birth of twins on Day 153 post-ovulation. Both fetuses were detected via ultrasound 15 days pre-partum. These results suggest that an absence of pre-partum behaviors, ultrasound evidence of endometrial edema without a fetus, and an extended luteal phase may be indicative of pseudopregnancy in giant pandas. Simultaneous monitoring of morphology, behavior, and urinary-endocrine profiles showed clear differences between successful and unsuccessful reproductive years.

Development and validation of protein biomarkers of health in grizzly bears

Large carnivores play critical roles in the maintenance and function of natural ecosystems; however, the populations of many of these species are in decline across the globe. Therefore, there is an urgent need to develop novel techniques that can be used as sensitive conservation tools to detect new threats to the health of individual animals well in advance of population-level effects. Our study aimed to determine the expression of proteins related to energetics, reproduction and stress in the skin of grizzly bears (Ursus arctos) using a liquid chromatography and multiple reaction monitoring mass spectrometry assay. We hypothesized that a suite of target proteins could be measured using this technique and that the expression of these proteins would be associated with biological (sex, age, sample location on body) and environmental (geographic area, season, sample year) variables. Small skin biopsies were collected from free-ranging grizzly bears in Alberta, Canada, from 2013 to 2019 (n = 136 samples from 111 individuals). Over 700 proteins were detected in the skin of grizzly bears, 19 of which were chosen as targets because of their established roles in physiological function. Generalized linear mixed model analysis was used for each target protein. Results indicate that sample year influenced the majority of proteins, suggesting that physiological changes may be driven in part by responses to changes in the environment. Season influenced the expression of proteins related to energetics, reproduction and stress, all of which were lower during fall compared to early spring. The expression of proteins related to energetics and stress varied by geographic area, while the majority of proteins that were affected by biological attributes (age class, sex and age class by sex interaction) were related to reproduction and stress. This study provides a novel method by which scientists and managers can further assess and monitor physiological function in wildlife.

Urinary estrogens as a non-invasive biomarker of viable pregnancy in the giant panda (Ailuropoda melanoleuca)

Female giant pandas show complex reproductive traits, being seasonally monoestrus, displaying a variable length embryonic diapause and exhibiting pseudopregnancy. Currently, there is no confirmatory non-invasive biomarker of blastocyst implantation or pregnancy. This study aimed to monitor urinary estrogens across gestation in pregnancy (n = 4), pseudopregnancy (n = 4) and non-birth cycles (n = 5) in the giant panda. A pregnancy-specific profile of estrogens corrected for urinary specific gravity was identified during the gestation period. Pregnant females showed increasing concentrations of estrogens for 29 days until birth, no increase was observed during pseudopregnancy and the two profiles were distinguishable from each other for the final 2 weeks of the cycle suggesting the estrogens are of placental origin. This allowed a nomogram, starting at a known fixed point during the cycle, to be created and tested with cycles of known outcome, and cycles which were inseminated but did not result in a birth. Non-birth profiles showed deviations from that of pregnancy. We believe these deviations indicate the point of failure of the placenta to support a developing cub. Non-invasive longitudinal monitoring of estrogen concentrations therefore has the potential to be developed as a panda pregnancy test to predict viable cub development.

Comprehensive Breeding Techniques for the Giant Panda

The dramatic growth of the captive giant panda (Ailuropoda melanoleuca) population exemplifies how the application of scientific findings to animal care and reproductive management can improve conservation breeding outcomes. Detailed behavioral studies of giant panda estrus, pregnancy and cub rearing have demonstrated the importance of husbandry management that supports natural reproductive behavior to enhance breeding success. Natural breeding has been valuably augmented by the development of assisted reproductive techniques founded through detailed studies of the reproductive physiology of the giant panda and outlining fundamental information about reproductive seasonality, male fertility and characterization of the estrous cycle. The resultant holistic understanding of giant panda reproduction has improved reproductive success in the captive population to such an extent that it is now self-sustaining and provides surplus animals for reintroduction. Despite these significant advances, there are knowledge gaps and remaining challenges to be addressed. Pregnancy detection remains the single biggest challenge when determining if natural mating or assisted breeding have been successful. Because pregnancy can only be determined in the few weeks prior to parturition, there are gaps in understanding and detecting delayed implantation and early embryonic loss. Additionally, dynamic management practices and standard of care for reproductive assistance needs to be developed. Only large breeding centers in China have the ability to promote normal reproductive behaviors and allow mate choice for the giant panda. These challenges need to be addressed in the near future in order to maintain a self-sustaining, genetically diverse and behaviorally competent captive population. This chapter documents the development of successful giant panda managed breeding programs by focusing on three key areas, (1) the development of science-driven reproductive techniques to improve fecundity in a species where the mating system was poorly understood, (2) how targeted research and adaptive management of social settings surrounding estrus and breeding improved reproductive success, and (3) insights and solutions to challenges faced across the program's history with future directions for research.

Urinary specific gravity as an alternative for the normalisation of endocrine metabolite concentrations in giant panda (Ailuropoda melanoleuca) reproductive monitoring

Reproductive monitoring for captive breeding in giant pandas is based on behavioural observation and non-invasive hormone analysis. In urine, interpretation of results requires normalisation due to an animal’s changing hydration. Correction of urinary concentrations based on creatinine is the gold standard. In this study, a largely unexplored, easy-to-perform normalisation technique, based on urinary specific gravity (USpG), was examined and compared to creatinine. To this extent, six cycles from two female pandas (SB741(1) and SB569(5)) were monitored through urine analysis for oestrogen, progesterone, ceruloplasmin and 13,14-dihydro-15-keto-PGF2a (PGFM). The Pearson’s correlation between creatinine and USpG was high (r = 0.805–0.894; p < 0.01), indicative for a similar performance of both normalisation methods. However, generally lower values were observed during pro-oestrus and primary (progesterone) rise. This could be associated with huge shifts in appetite, monitored by faecal output (kg) with an averaged > 50% decrease during oestrus and >50% increase during primary progesterone rise. In parallel, respectively highest and lowest creatinine and USpG levels, were measured, with creatinine obviously more affected as a result of linkage with muscle tissue metabolism affected by reproductive hormones. As a consequence, metabolite levels were significantly different between both corrected datasets with significantly higher oestrogen peak levels during oestrus ranging from 2.13–86.93 and 31.61–306.45 ng/mL (USpG correction) versus 2.33–31.20 and 36.36–249.05 ng/mL Cr (creatinine correction) for SB569 and SB741 respectively, and significant lower progesterone levels during primary progesterone rise ranging from 0.35–3.21 and 0.85–6.80 ng/mL (USpG correction) versus 0.52–10.31 and 2.10–272.74 ng/mL Cr (creatinine correction) for SB569 and SB741 respectively. Consequently, USpG correction rendered unbiased profiles, less subject to variation and metabolic artefacts and therefore allowed a more straightforward identification of peak oestrogen and onset of secondary progesterone rise, being potentially advantageous for future studies unravelling key giant panda reproductive events, including (delayed) implantation. The alternative application of USpG as a normalisation factor was further supported by its easy application and environmental and technical robustness.