Transcriptomic analysis of equine placenta reveals key regulators and pathways involved in ascending placentitis†

Placental homogeneity: Characterizing transcriptional variation among equine chorioallantoic locations

The proper function of the placenta is essential for the health and growth of the fetus and the mother. The placenta relies on dynamic gene expression for its correct and timely development and function. Although numerous studies have identified genes vital for placental functions, equine placental molecular research has primarily focused on single placental locations, in sharp contrast with the broader approach in human studies. Here, we hypothesized that the molecular differences across different regions of the equine placenta are negligible because of its diffuse placental type with a macroscopic homogenous distribution of villi across the placental surface. We compared the transcriptome and stereological findings of the body, pregnant horn, and non-pregnant horn within the equine chorioallantois. Our transcriptomic analysis indicates that the variation between regions of the placenta within individuals is less than the variation observed between individuals. A low number of differentially expressed genes (DEGs) (n = 8) was identified when comparing pregnant and non-pregnant horns within the same placenta, suggesting a remarkable molecular uniformity. A higher number of DEGs was identified when comparing each horn to the body (193 DEGs comparing pregnant horn with body and 207 DEGs comparing non-pregnant horn with body). Genes with a higher expression in the body were associated with processes such as extracellular matrix synthesis and remodeling, which is relevant for placental maturation and placenta-endometrial separation at term and implies asynchrony of these processes across locations. The stereological analysis showed no differences in microcotyledonary density, and width between the locations. However, we observed a greater chorioallantoic thickness in the body and pregnant horn compared to the non-pregnant horn. Overall, our findings reveal a uniform transcriptomic profile across the placental horns, alongside a more distinct gene expression pattern between the uterine body and horns. These regional differences in gene expression suggest a different pace in the placental maturation and detachment among the placental locations.

Evaluating the IL-6 Family of Cytokines Throughout Equine Gestation

INTRODUCTION

The interleukin (IL)-6 family of cytokines is grouped by a common receptor subunit (gp130), but functions in distinct but overlapping physiological activities, including regulation of acute phase reaction and the balance between effector and regulatory T cell populations-both of which play a role in successful pregnancy maturation.

METHODS

Here, we aim to assess the expression profiles of members of the IL-6 cytokine family throughout equine gestation. To do so, RNA Sequencing was performed on chorioallantois and endometrium of mares at 120, 180, 300, and 330 days of gestation (n = 4/stage), as well as 45-day chorioallantois (n = 4) and diestrus endometrium (n = 3). Expression levels of members of the IL-6 cytokine family including ciliary neurotrophic factor (CNTF), cardiotrophin 1 (CT-1), cardiotrophin-like cytokine factor 1 (CLCF1), galectin-10, oncostatin M (OSM), and IL-6, -11, and -27 were evaluated in addition to the receptors for IL-6 (IL-6R) and the common receptor subunit gp130. Additionally, peripheral concentration of IL-6 was assessed.

RESULTS

In the chorioallantois, differential expression of IL-6, IL-11, CNTF, CLCF1, OSM, and CT-1 was noted. In the endometrium, the gestational age of pregnancy impacted the expression of IL-11, CNTF, and CT-1. Circulatory IL-6 concentrations reached their highest concentrations at 120 days, with lesser concentrations noted at 45, 180, 300, and 330 days. Both IL-6R and gp130 altered in expression throughout equine gestation.

CONCLUSION

In conclusion, members of the IL-6 cytokine family appear to fluctuate constantly throughout equine pregnancy, with varying expression profiles noted when comparing individual members. Additionally, different expression profiles were noted when comparing chorioallantois, endometrium, and circulation, indicating that the function of the cytokine is tissue-specific.

Characterization of the equine placental microbial population during nocardioform placentitis

Nocardioform placentitis is a poorly understood disease of equine late gestation. The presence of nocardioform, filamentous branching gram-positive bacteria, has been linked to the disease, with Crossiella equi, Amycolatopsis spp., and Streptomyces spp. being the most frequently identified bacteria. However, these bacteria are not found in all clinical cases in addition to being isolated from healthy, normal postpartum placentas. To better understand this form of placentitis, we analyzed the microbial composition in the equine placenta (chorioallantois) of both healthy postpartum (control; n = 11) and nocardioform-affected samples (n = 22) using 16S rDNA sequencing. We found a lower Shannon index in nocardioform samples, a higher Chao1 index in nocardioform samples, and a difference in beta diversity between control and nocardioform samples (p < 0.05), suggesting the presence of dysbiosis during the disease. In the majority of the NP samples (77 %), one of the following genera-Amycolatopsis, Crossiella, Lentzea, an unidentified member of the Pseudonocardiaceae family, Mycobacterium, or Enterococcus -represented over 70 % of the relative abundance. Overall, the data suggest that a broader spectrum of potential opportunistic pathogens could be involved in nocardioform placentitis, extending beyond the traditionally recognized bacteria, resulting in a similar histomorphological profile.

Role of nuclear receptor PXR in immune cells and inflammatory diseases

Pregnane X receptor (PXR, NR1I2), a prototypical member of the nuclear receptor superfamily, has been implicated in various processes including metabolism, immune response, and inflammation. The immune system is made up of many interdependent parts, including lymphoid organs, cells, and cytokines, which play important roles in identifying, repelling, and eliminating pathogens and other foreign chemicals. An impaired immune system could contribute to various physical dysfunction, including severe infections, allergic diseases, autoimmune disorders, and other inflammatory diseases. Recent studies revealed the involvement of PXR in the pathogenesis of immune disorders and inflammatory responses. Thus, the aim of this work is to review and discuss the advances in research associated with PXR on immunity and inflammatory diseases and to provide insights into the development of therapeutic interventions of immune disorders and inflammatory diseases by targeting PXR.

Transcriptomic and histochemical analysis reveal the complex regulatory networks in equine Chorioallantois during spontaneous term labor

The equine chorioallantois (CA) undergoes complex physical and biochemical changes during labor. However, the molecular mechanisms controlling these changes are still unclear. Therefore, the current study aimed to characterize the transcriptome of equine CA during spontaneous labor and compare it to that of normal preterm CA. Placental samples were collected postpartum from mares with normal term labor (TL group, n = 4) and from preterm not in labor mares (330 days GA; PTNL group, n = 4). Our study identified 4137 differentially expressed genes (DEGs) (1820 upregulated and 2317 downregulated) in CA during TL as compared to PTNL. TL was associated with the upregulation of several pro-inflammatory mediators (MHC-I, MHC-II, NLRP3, CXCL8, and MIF). Also, TL was associated with the upregulation of matrix metalloproteinase (MMP1, MMP2, MMP3, and MMP9) with subsequent extracellular matrix degradation and apoptosis, as reflected by upregulation of several apoptosis-related genes (ATF3, ATF4, FAS, FOS, and BIRC3). In addition, TL was associated with downregulation of 21 transcripts coding for collagens. The upregulation of proteases, along with the downregulation of collagens, is believed to be implicated in separation and rupture of the CA during TL. Additionally, TL was associated with downregulation of transcripts coding for proteins essential for progestin synthesis (SRD5A1 and AKR1C1) and angiogenesis (VEGFA and RTL1), as well as upregulation of prostaglandin synthesis-related genes (PTGS2 and PTGES), which could reflect the physiological switch in placental endocrinology and function during TL. In conclusion, our findings revealed the equine CA gene expression signature in spontaneous labor at term, which improves our understanding of the molecular mechanisms triggering labor.

Tumor necrosis factor signaling during equine placental infection leads to pro-apoptotic and necroptotic outcomes

Ascending placentitis is the leading cause of abortion in the horse. The pleiotropic cytokine tumor necrosis factor (TNF) is an upstream regulator of this disease, but little is understood regarding its function in pregnancy maintenance or placental infection. To assess this, RNA sequencing was performed on chorioallantois and endometrium of healthy pregnant mares at various gestational lengths (n = 4/gestational age), in addition to postpartum chorioallantois, and diestrus endometrium to assess expression of TNF, TNFR-1, and TNFR-2. Additionally, ascending placentitis was induced via trans-cervical inoculation of S. equi spp. zooepidemicus in pregnant mares (n = 6 infected / n = 6 control) and tissues and serum were collected to evaluate TNF-related transcripts. IHC was performed to confirm protein localization of TNFR-1 and TNFR-2. In healthy pregnancy, TNFR-1 appears to be the predominant TNF-related receptor. Following induction of disease, TNF concentrations increased in maternal serum, but expression did not alter at the tissue level. While both TNFR-1 and TNFR-2 increased following induction of disease, alterations in downstream pathways indicate that TNFR-1 is the dominant receptor in ascending placentitis, and is primarily activated within the chorioallantois, with minimal signaling occurring within the endometrium. In conclusion, TNF appears to be involved in the pathophysiology of ascending placentitis. An increase in this cytokine during disease progression is believed to activate TNFR-1 within the chorioallantois, leading to various pro-apoptotic and necroptotic outcomes, all of which may signal for fetal demise and impending abortion.

Impact of inflammation and infection on the expression of amino acid transporters in the placenta: A minireview

Amino acid transporters expressed in the placenta help to regulate the transfer of amino acids from maternal to fetal circulation. Nutritional or hormonal factors are known to potentially impact the expression of amino acid transporters in the placenta. A relatively new field of inquiry has also demonstrated that inflammation, whether associated with infection or not, also alters the expression of amino acid transporters in the placenta. Indeed, studies over the past 15 years have demonstrated that malaria, viral and bacterial models of infection, preeclampsia, and direct administration of proinflammatory cytokines can alter placental amino acid transporter expression. While such studies have largely focused on System A and System L transporters, other transporters are also affected. p38 MAPK, STAT3, mTORC1, and AMPK signaling have all been implicated in these changes, but the underlying mechanism(s) remain to be fully elucidated. Furthermore, the implications of such changes warrant further investigation. This review will summarize studies that have investigated the impact of inflammation on placental amino acid transporter expression, identify questions that remain unanswered, and propose future areas of research to advance the field. As amino acid transporters are now being considered for drug targeting and drug delivery, furthering our understanding of the regulation of these transporters during disease states will be of increasing clinical value. Significance Statement While this is a relatively new field of research, multiple studies have demonstrated that inflammation alters placental amino acid transporter expression. This review will serve to summarize, for the first time, studies in this field and identify gaps in current knowledge as research in this area moves beyond identifying changes in transporter expression to investigating the implications of such changes and the mechanisms underlying them.

Multifaced roles of PLAC8 in cancer

The role of PLAC8 in tumorigenesis has been gradually elucidated with the development of research. Although there are common molecular mechanisms that enforce cell growth, the impact of PLAC8 is varied and can, in some instances, have opposite effects on tumorigenesis. To systematically understand the role of PLAC8 in tumors, the molecular functions of PLAC8 in cancer will be discussed by focusing on how PLAC8 impacts tumorigenesis when it arises within tumor cells and how these roles can change in different stages of cancer progression with the ultimate goal of suppressing PLAC8-relevant cancer behavior and related pathologies. In addition, we highlight the diversity of PLAC8 in different tumors and its functional output beyond cancer cell growth. The comprehension of PLAC8's molecular function might provide new target and lead to the development of novel anticancer therapies.

Transcriptomic analysis of equine chorioallantois reveals immune networks and molecular mechanisms involved in nocardioform placentitis

Nocardioform placentitis (NP) continues to result in episodic outbreaks of abortion and preterm birth in mares and remains a poorly understood disease. The objective of this study was to characterize the transcriptome of the chorioallantois (CA) of mares with NP. The CA were collected from mares with confirmed NP based upon histopathology, microbiological culture and PCR for Amycolatopsis spp. Samples were collected from the margin of the NP lesion (NPL, n = 4) and grossly normal region (NPN, n = 4). Additionally, CA samples were collected from normal postpartum mares (Control; CRL, n = 4). Transcriptome analysis identified 2892 differentially expressed genes (DEGs) in NPL vs. CRL and 2450 DEGs in NPL vs. NPN. Functional genomics analysis elucidated that inflammatory signaling, toll-like receptor signaling, inflammasome activation, chemotaxis, and apoptosis pathways are involved in NP. The increased leukocytic infiltration in NPL was associated with the upregulation of matrix metalloproteinase (MMP1, MMP3, and MMP8) and apoptosis-related genes, such as caspases (CASP3 and CASP7), which could explain placental separation associated with NP. Also, NP was associated with downregulation of several placenta-regulatory genes (ABCG2, GCM1, EPAS1, and NR3C1), angiogenesis-related genes (VEGFA, FLT1, KDR, and ANGPT2), and glucose transporter coding genes (GLUT1, GLUT10, and GLUT12), as well as upregulation of hypoxia-related genes (HIF1A and EGLN3), which could elucidate placental insufficiency accompanying NP. In conclusion, our findings revealed for the first time, the key regulators and mechanisms underlying placental inflammation, separation, and insufficiency during NP, which might lead to the development of efficacious therapies or diagnostic aids by targeting the key molecular pathways.