The Effects of Platelet-Activating Factor on Uterine Contractility, Perfusion, Hypoxia, and Pain in Mice

Imaging the dynamics of murine uterine contractions in early pregnancy†

Uterine muscle contractility is essential for reproductive processes including sperm and embryo transport, and during the uterine cycle to remove menstrual effluent. Even still, uterine contractions have primarily been studied in the context of preterm labor. This is partly due to a lack of methods for studying the uterine muscle contractility in the intact organ. Here, we describe an imaging-based method to evaluate mouse uterine contractility of both the longitudinal and circular muscles in the cycling stages and in early pregnancy. By transforming the image-based data into three-dimensional spatiotemporal contractility maps, we calculate waveform characteristics of muscle contractions, including amplitude, frequency, wavelength, and velocity. We report that the native organ is highly contractile during the progesterone-dominant diestrus stage of the cycle when compared to the estrogen-dominant proestrus and estrus stages. We also observed that during the first phase of uterine embryo movement when clustered embryos move toward the middle of the uterine horn, contractions are dynamic and non-uniform between different segments of the uterine horn. In the second phase of embryo movement, contractions are more uniform and rhythmic throughout the uterine horn. Finally, in Lpar3-/- uteri, which display faster embryo movement, we observe global and regional increases in contractility. Our method provides a means to understand the wave characteristics of uterine smooth muscle in response to modulators and in genetic mutants. Better understanding uterine contractility in the early pregnancy stages is critical for the advancement of artificial reproductive technologies and a possibility of modulating embryo movement during clinical embryo transfers.

Role of Platelet Activating Factor as a Mediator of Inflammatory Diseases and Preterm Delivery

Nearly 70% of preterm deliveries occur spontaneously, and the clinical pathways involved include preterm labor and preterm premature rupture of membranes. Prediction of preterm delivery is considered crucial due to the significant effects of preterm birth on health and the economy at both the personal and community levels. Although similar inflammatory processes occur in both term and preterm delivery, the premature activation of these processes or exaggerated inflammatory response triggered by infection or sterile factors leads to preterm delivery. Platelet activating factor (PAF) is a phosphoglycerylether lipid mediator of inflammation that is implicated in infections, cancers, and various chronic diseases and disorders including cardiovascular, renal, cerebrovascular, and central nervous system diseases. In gestational tissues, PAF mediates the inflammatory pathways that stimulate the effector mechanisms of labor, including myometrial contraction, cervical dilation, and fetal membrane rupture. Women with preterm labor and preterm premature rupture of membranes have increased levels of PAF in their amniotic fluid. In mice, the intrauterine or intraperitoneal administration of carbamyl PAF activates inflammation in gestational tissues, thereby eliciting preterm delivery. This review summarizes recent research on PAF as an important inflammatory mediator in preterm delivery and in other inflammatory disorders, highlighting its potential value for prediction, intervention, and prevention of these diseases.

Inhibitory Effect and Mechanism upon Glucose-Insulin-Potassium Administration on Postpartum Mice with Uterine Cramping Pain

This study aimed to explore the effect of glucose-insulin-potassium (GIK) on postpartum uterine cramping pain(UCP) in mice and the possible underlying mechanisms. Thirty full-term pregnancy C57BL/6 mice, within 6 h after spontaneous labor, the mice were randomly assigned into the following three groups: the control group (group C), the oxytocin group (group O), and the GIK plus oxytocin group (group G). Group G and group O were administered GIK and normal saline, respectively, and 10 min later, oxytocin was injected intraperitoneally; group C received normal saline twice. The pain scores of the mice were assessed after establishment of the postpartum UCP model. The differential expressions of energy metabolism and oxidized lipid metabolites in the uterus were analyzed. The behavioral scores in group G were significantly lower than those in group O (P < 0.05).When compared to group O, group G showed a significant increase in ATP levels (P = 0.046), and group G exhibited elevated levels of amino acids, including L-glutamine, L-aspartic acid, and ornithine. Additionally, phosphate compounds (2-phosphoglyceric acid and 3-phosphoglyceric acid) showed elevated levels. When compared to group O, group G exhibited a decrease in 19R-hydroxy PGF2α, an increase in 9,10-EpOME and 12,13-EpOME, and a decrease in trans-EKODE-E-Ib. Additionally, group G showed an elevation in 16,17-EpDPE and 8-HDoHE. This study confirms the analgesic effect of GIK during postpartum oxytocin infusion. Metabolomics and glycolysis product analysis suggest that GIK's alleviation of UCP is associated with its enhancement of glycolysis and the influence of phenylalanine synthesis, aspartate metabolism, and arginine synthesis pathways. Additionally, the effects of GIK appears to be linked to its influence on the linoleic acid metabolic pathway.

Facilitated Central Pain Mechanisms Across the Menstrual Cycle in Dysmenorrhea and Enlarged Pain Distribution in Women With Longer Pain History

Dysmenorrhea (DYS), or recurrent menstrual pain, is a highly prevalent pain condition among otherwise healthy women. However, the progression of DYS over time and the influence of the menstrual cycle phases need to be better understood. While the location and distribution of pain have been used to assess pain mechanisms in other conditions, they are unexplored in DYS. Thirty otherwise healthy women with severe DYS and 30 healthy control women were recruited into 3 subgroups (n = 10) according to the length of their menstrual history (<5, 5-15, or>15 years since menarche). The intensity and distribution of menstrual pain were recorded. Pressure pain thresholds at abdominal, hip, and arm sites, pressure-induced pain distribution, temporal summation of pain, and pain intensity after pressure cessation over the gluteus medius were assessed at 3 menstrual cycle phases. Compared with the healthy control women, those with DYS showed lower pressure pain thresholds in every site and menstrual cycle phase (P < .05), enlarged pressure-induced pain areas during menstruations (P < .01), and increased temporal summation and pain intensity after pressure cessation in the overall menstrual cycle (P < .05). Additionally, these manifestations were enhanced during the menstrual and premenstrual phases compared to ovulation in women with DYS (P < .01). Women with long-term DYS demonstrated enlarged pressure-induced pain distribution, enlarged menstrual pain areas, and more days with severe menstrual pain compared to the short-term DYS subgroup (P < .01). Pressure-induced and menstrual pain distributions were strongly correlated (P < .001). These findings suggest that severe DYS is a progressive condition underscored by facilitated central pain mechanisms associated with pain recurrence and exacerbation. PERSPECTIVE: Enlarged pressure-induced pain areas occur in DYS, associated with the length of the condition and the distribution of menstrual pain. Generalized hyperalgesia is present throughout the entire menstrual cycle and intensifies during premenstrual and menstrual phases.

The Role of Platelets in the Pathogenesis and Pathophysiology of Adenomyosis

Widely viewed as an enigmatic disease, adenomyosis is a common gynecological disease with bewildering pathogenesis and pathophysiology. One defining hallmark of adenomyotic lesions is cyclic bleeding as in eutopic endometrium, yet bleeding is a quintessential trademark of tissue injury, which is invariably followed by tissue repair. Consequently, adenomyotic lesions resemble wounds. Following each bleeding episode, adenomyotic lesions undergo tissue repair, and, as such, platelets are the first responder that heralds the subsequent tissue repair. This repeated tissue injury and repair (ReTIAR) would elicit several key molecular events crucial for lesional progression, eventually leading to lesional fibrosis. Platelets interact with adenomyotic cells and actively participate in these events, promoting the lesional progression and fibrogenesis. Lesional fibrosis may also be propagated into their neighboring endometrial-myometrial interface and then to eutopic endometrium, impairing endometrial repair and causing heavy menstrual bleeding. Moreover, lesional progression may result in hyperinnervation and an enlarged uterus. In this review, the role of platelets in the pathogenesis, progression, and pathophysiology is reviewed, along with the therapeutic implication. In addition, I shall demonstrate how the notion of ReTIAR provides a much needed framework to tether to and piece together many seemingly unrelated findings and how it helps to make useful predictions.

Glucose-insulin-potassium alleviates uterine cramping pain following cesarean delivery: A randomized, controlled trial

Objectives

To explore the effect of glucose-insulin-potassium (GIK) therapy on uterine cramping pain (UCP) following cesarean delivery (CD).

Design

Single-center, randomized controlled study.

Setting

Second Affiliated Hospital of Army Medical University, Chongqing, China.

Participants

A total of 140 women, aged 20-40 years, who underwent CD with a transverse incision were randomly assigned to the GIK (P) or control (C) groups in a 1:1 ratio.

Interventions

GIK was intravenously administered to patients in Group P. Patients in Group C received normal saline (NS). After umbilical cord clamping, oxytocin was administered intravenously. The same GIK and NS regimens were administered on postoperative days 1 and 2, followed by oxytocin 10 min later.

Primary and secondary outcome measures

Following oxytocin administration, UCP was assessed using the visual analog scale (VAS), and the maximum VAS score (primary outcome) was recorded.

Results

Patients in Group P had significantly lower maximum VAS scores than those in Group C on postoperative days 1 (38.4 ± 21.1 vs. 52.3 ± 20.8, p < 0.001) and 2 (10 [0,30] vs. 30.5 [8.75,50], p < 0.001). Group P patients also had shorter pain duration on postoperative day 1 (39.6 ± 19.5 min vs. 50.6 ± 18.2 min, p = 0.001). Group P patients had a lower incidence of inadequate analgesia of UCP than Group C on days 1 (45.5% vs. 74.2%, p < 0.001) and 2 (10.6% vs. 47.0%, p < 0.001); the RRs for experiencing inadequate analgesia for UCP postpartum in Group P patients was 0.612 (95% CI: 0.454-0.826, p < 0.001) on day 1 and 0.226 (95% CI: 0.107-0.476, p < 0.001) on day 2. The absolute risk reduction (ARR) was 28.7%; thus number needed to treat (NNT) was 3 after rounding up. A subgroup analysis demonstrated that Group P patients undergoing repeat CD had lower maximum VAS scores for UCP on both postoperative days 1 and 2.

Conclusion

Our findings suggest that GIK can relieve UCP and shorten its duration. Our results provide information to facilitate the development of novel approaches for managing UCP.Clinical Trial Registration: This study was approved by the Medical Ethics Committee of Second Affiliated Hospital of Army Medical University (2020-109-01, 19/11/2020) and registered in the Chinese Clinical Trial Registry (http://www.chictr.org.cn, ChiCTR2100041607,01/01/2021).

Analgesic outcomes of tramadol alone and in combination with Butorphanol or Flurbiprofen Axetil after cesarean section: a retrospective study with propensity score matching analysis

BACKGROUND

The Society for Obstetric Anesthesia and Perinatology recommends a multimodal analgesia regimen for cesarean delivery analgesia. This study aimed to compare the analgesic effects of tramadol alone and combined with butorphanol or flurbiprofen axetil after a cesarean section.

METHODS

We performed a retrospective analysis based on the electronic medical records of a teaching hospital in China from January 2018 to January 2020. We collected data on demographic characteristics, anesthesia, analgesia strategy, and pain intensity postoperatively during the first 48 hours. Inadequate postoperative analgesia during this period was defined as an NRS score ≥ 4. We also collected data regarding off-bed activity and intestinal function recovery. Participants were classified into three groups according to analgesia regimens. Groups T, TF, and TB received tramadol, a mixture of tramadol and flurbiprofen axetil, and a combination of tramadol and butorphanol, respectively. Analgesic outcomes were compared using propensity score matching analysis.

RESULTS

Data from 2323 cases of caesarean section were included in the analysis, and 521 pairs were matched in each group according to their propensity score. Compared with group T, The inadequate analgesia on pain at rest and pain at movement was lower in group TF (RR: 0.42, 95% CI: 0.36-0.49, P = 0.001 and RR: 0.58, 95% CI: 0.48-0.69, P < 0.001, respectively),and the incidence of inadequate control of pain at movement was higher in group TB (RR: 1.38, 95% CI: 1.22-1.55, P < 0.001). Additionally, the percentage of off-bed activity at 2 days postoperatively was higher in group TB than in groups TF and T (78.7% vs. 68.5 and 78.7% vs. 64.9%, respectively, P < 0.001). The incidence of intestinal function recovery 2 days after cesarean delivery in group TB was higher than that in group TF (73.3% vs. 66.2%, P = 0.013).

CONCLUSIONS

Combining tramadol and flurbiprofen axetil could enhance the analgesic effect and be safely used for analgesia after a cesarean section. However, combining tramadol and butorphanol may produce an antagonistic effect.

Association of endocannabinoids with pain in endometriosis

ABSTRACT

Endocannabinoid (eCB) levels fluctuate in inflammatory conditions and as such may take part in endometriosis-associated pain or even in endometriosis pathogenesis. In this case-control (23 cases and 19 controls) study, targeted lipids were measured in the serum and peritoneal fluid collected during laparoscopy. Endometriosis was confirmed histologically. Dysmenorrhea, abdominal pain, and dyspareunia were assessed using the Numeric Rating Scale for pain. Steroids, eCBs, and related lipids were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Tumor necrosis factor alpha, IL-8, PAPP-A, PP14, RANTES, OPG, MIDKINE, MCP-1, VEGF, leptin, and defensins were quantified by ELISA. We found that eCB levels were significantly influenced by both noncyclic and cyclic abdominal pain. Specifically, women suffering from noncyclic abdominal pain were characterized by a higher 2-AG level in the peritoneal fluid throughout the menstrual cycle, whereas women suffering from dysmenorrhea had higher 2-AG levels and lower AEA levels during the proliferative phase alone. In addition, 2-AG positively correlated with prostaglandin E2 (PGE2), and the ratio AEA/2-AG positively correlated with defensins, suggesting a possible link between endocannabinoids system and inflammatory pain. The results of the current study indicate that the eCB system may play a role in endometriosis-associated pain, but additional studies are needed to investigate the causal relationship.

Low Serum Naproxen Concentrations Are Associated with Minimal Pain Relief: A Preliminary Study in Women with Dysmenorrhea

OBJECTIVE

Incomplete pain relief after administration of nonsteroidal anti-inflammatory drugs (NSAIDs) is common, but it is unknown whether malabsorption or heightened metabolism contributes to NSAID resistance. To explain the etiology of NSAID resistance, we evaluated naproxen absorption and metabolism in relation to pain relief in a pilot study of women with dysmenorrhea.

METHODS

During menses, participants completed before and after naproxen ingestion pain assessments. Analgesic effectiveness was calculated as a percent change in pain rating before and after naproxen administration. To evaluate the impact of malabsorption, the correlation between analgesic effectiveness and serum naproxen was analyzed. To identify whether hypermetabolism contributes to NSAID resistance, we also analyzed the metabolite O-desmethylnaproxen.

RESULTS

Serum naproxen and O-desmethylnaproxen concentrations of the dysmenorrheic cohort (N = 23, 126 ± 10 µg/mL, 381 ± 56 ng/mL) and healthy controls (N = 12, 135 ± 8 µg/mL, 355 ± 58 ng/mL) were not significantly different (P > 0.05), suggesting that menstrual pain does not affect drug absorption and metabolism. However, nine dysmenorrhea participants had levels of analgesic effectiveness <30%. Among dysmenorrheic women, analgesic effectiveness was correlated with serum naproxen (r = 0.49, P = 0.019) and O-desmethylnaproxen (r = 0.45, P = 0.032) concentrations. After controlling for other gynecological diagnoses, a multivariate model analysis confirmed that lower serum naproxen concentrations were associated with reduced pain relief (P  = 0.038).

CONCLUSIONS

Our preliminary findings suggest that poor drug absorption contributes to ineffective pain relief in dysmenorrheic women. Future studies should explore whether malabsorption contributes to NSAID resistance for other pain conditions.

Mouse model of menstruation: An indispensable tool to investigate the mechanisms of menstruation and gynaecological diseases (Review)

Abnormal menstruation may result in several pathological alterations and gynaecological diseases, including endometriosis, menstrual pain and miscarriage. However, the pathogenesis of menstruation remains unclear due to the limited number of animal models available to study the menstrual cycle. In recent years, an effective, reproducible, and highly adaptive mouse model to study menstruation has been developed. In this model, progesterone and oestrogen were administered in cycles following the removal of ovaries. Subsequently, endometrial decidualisation was induced using sesame oil, followed by withdrawal of progesterone administration. Vaginal bleeding in mice is similar to that in humans. Therefore, the use of mice as a model organism to study the mechanism of menstruation and gynaecological diseases may prove to be an important breakthrough. The present review is focussed ond the development and applications of a mouse model of menstruation. Furthermore, various studies have been described to improve this model and the research findings that may aid in the treatment of menstrual disorders in women are presented.

Hypertensive disorders of pregnancy are associated with dysmenorrhea in early adulthood: A cohort study

AIM

Hypertensive disorders of pregnancy (HDP) are serious conditions that occur in 5-10% of pregnancies. Maternal factors, such as maternal age, obesity, and renal disease, have been described as risk factors. In order to extract the background lifestyle and gynecological characteristics for HDP, we conducted a prospective cohort study.

METHODS

Pregnant participants were administered a questionnaire on characteristics, menstrual abnormalities and lifestyle factors. The women were followed individually until 1-month postpartum. We used medical records to examine the relationship between menstrual abnormalities and the onset of HDP.

RESULTS

We collected data from 193 pregnant women, and excluding 3 who had miscarriage, examined the records of 190. A total of 26 patients developed HDP, of which 10 had early-onset HDP and 16 had late-onset HDP. Although there was no significant association between HDP and dysmenorrhea just prior to pregnancy, there was a significant increase in the incidence of HDP in patients who experienced dysmenorrhea around the age of 20 years (odds ratio 4.362 [95% CI 1.61-11.81]).

CONCLUSION

We found that patients with a history of dysmenorrhea around the age of 20 years have a significantly higher risk of developing HDP. Although dysmenorrhea in young adulthood is ameliorated, it may become apparent as a perinatal disease when a physical load such as pregnancy is applied.

Menstrual Pain: A Review of Foreign Literature

The World Health Organization estimates dysmenorrhea as the most important cause of a chronic pelvic pain. Its prevalence among adolescents and young women ranges from 40 % to 90 %, and varies, depending on age, country of residence and population density of the area. Primary dysmenorrhea is responsible for reducing the quality of life, absenteeism in the workplace or at school, refusing to participate in community and sporting events, changing of pain perception and sleep disturbance. There is evidence of its relationship with an early menarche, a family history, a length of the menstrual cycle, bad habits, poor sleep hygiene, an unbalanced diet, sedentary lifestyle and obesity. Characteristic features of a personality contribute in a certain way, making women prone to neuroticism and pain catastrophizing to be more at risk of developing dysmenorrhea. Irritable bowel syndrome, musculoskeletal pain and interstitial cystitis often accompany dysmenorrhea and respond to its treatment positively. Despite the proven validity of nonsteroidal anti­inflammatory drugs treatment there are resistant forms of menstrual pain, those make a search for alternative therapy relevant.

Abdominal skeletal muscle activity precedes spontaneous menstrual cramping pain in primary dysmenorrhea

BACKGROUND

Dysmenorrhea is a pervasive pain condition that affects 20-50% of reproductive-aged women. Distension of a visceral organ, such as the uterus, could elicit a visceromotor reflex, resulting in involuntary skeletal muscle activity and referred pain. Although referred abdominal pain mechanisms can contribute to visceral pain, the role of abdominal muscle activity has not yet been investigated within the context of menstrual pain.

OBJECTIVE

The goal of this study was to determine whether involuntary abdominal muscle activity precedes spontaneous episodes of menstrual cramping pain in dysmenorrheic women and whether naproxen administration affects abdominal muscle activity.

STUDY DESIGN

Abdominal electromyography activity was recorded from women with severe dysmenorrhea (n = 38) and healthy controls (n = 10) during menses. Simultaneously, pain was measured in real time using a squeeze bulb or visual analog rheostat. Ninety minutes after naproxen administration, abdominal electromyography activity and menstrual pain were reassessed. As an additional control, women were also recorded off menses, and data were analyzed in relation to random bulb squeezes. Because it is unknown whether mechanisms of menstrual cramps are different in primary or secondary dysmenorrhea/chronic pelvic pain, the relationship between medical history and abdominal muscle activity was examined. To further examine differences in nociceptive mechanisms, pressure pain thresholds were also measured to evaluate changes in widespread pain sensitivity.

RESULTS

Abdominal muscle activity related to random-bulb squeezing was rarely observed in healthy controls on menses (0.9 ± 0.6 episodes/hour) and in dysmenorrhea participants off menses (2.3 ± 0.6 episodes/hour). In dysmenorrheic participants during menses, abdominal muscle activity frequently preceded bulb squeezing indicative of menstrual cramping pain (10.8 ± 3.0 episodes/hour; P < .004). Whereas 45% of the women with dysmenorrhea (17 of 38) had episodes of abdominal muscle activity associated pain, only 13% (5 of 38) had episodes after naproxen (P = .011). Women with the abdominal muscle activity-associated pain were less likely to have a diagnosis for secondary dysmenorrhea or chronic pelvic pain (2 of 17) than women without this pain phenotype (10 of 21; P = .034). Similarly, women with the abdominal muscle activity-associated pain phenotype had less nonmenstrual pain days per month (0.6 ± 0.5) than women without the phenotype (12.4 ± 0.3; P = .002). Women with abdominal muscle activity-associated pain had pressure pain thresholds (22.4 ± 3.0 N) comparable with healthy controls (22.2 ± 3.0 N; P = .967). In contrast, women without abdominal muscle activity-associated pain had lower pressure pain thresholds (16.1 ± 1.9 N; P = .039).

CONCLUSION

Abdominal muscle activity may contribute to cramping pain in primary dysmenorrhea but is resolvable with naproxen. Dysmenorrheic patients without cramp-associated abdominal muscle activity exhibit widespread pain sensitivity (lower pressure pain thresholds) and are more likely to also have a chronic pain diagnosis, suggesting their cramps are linked to changes in central pain processes. This preliminary study suggests new tools to phenotype menstrual pain and supports the hypothesis that multiple distinct mechanisms may contribute to dysmenorrhea.

Cine MRI during spontaneous cramps in women with menstrual pain

BACKGROUND

The lack of noninvasive methods to study dysmenorrhea has resulted in poor understanding of the mechanisms underlying pain, insufficient diagnostic tests, and limited treatment options. To address this knowledge gap, we have developed a magnetic resonance imaging-based strategy for continuously monitoring the uterus in relationship to participants' spontaneous pain perception.

OBJECTIVE

The study objective was to evaluate whether magnetic resonance imaging can detect real-time changes in myometrial activity during cramping episodes in women with dysmenorrhea, with a handheld squeeze bulb for pain reporting.

STUDY DESIGN

Sixteen women with dysmenorrhea and 10 healthy control women both on and off their menses were evaluated with magnetic resonance imaging while not taking analgesic medication. Continuous magnetic resonance imaging was acquired using half-Fourier acquisition single-shot turbo spin echo sequence along with simultaneous reporting of pain severity with a squeeze bulb. Pearson's coefficient was used to compare results between reviewers. Proportional differences between women with dysmenorrhea and controls on/off menses were evaluated with a Fisher exact test. The temporal relationships between signal changes were evaluated with Monte Carlo simulations.

RESULTS

Spontaneous progressive decreases in myometrial signal intensity were more frequently observed in women on their menses than in the absence of pain in the same women off their menses or participants without dysmenorrhea (P < .01). Women without reductions in myometrial signal intensity on their menses either had a history of endometriosis or were not in pain. Observations of myometrial events were consistently reported between 2 raters blinded to menstrual pain or day status (r = 0.97, P < .001). Episodes of cramping occurred either immediately before or 32-70 seconds after myometrial signal change onset (P < .05).

CONCLUSION

Transient decreases in myometrial uterine T2-weighted signal intensity can be reliably measured in women with menstrual pain. The directionality of signal change and temporal relationship to pain onset suggest that cramping pain may be caused by a combination of uterine pressure and hemodynamic dysfunction.

Nonsteroidal antiinflammatory drug resistance in dysmenorrhea: epidemiology, causes, and treatment

Although nonsteroidal antiinflammatory drugs can alleviate menstrual pain, about 18% of women with dysmenorrhea are unresponsive, leaving them and their physicians to pursue less well-studied strategies. The goal of this review is to provide a background for treating menstrual pain when first-line options fail. Research on menstrual pain and failure of similar drugs in the antiplatelet category suggested potential mechanisms underlying nonsteroidal antiinflammatory drug resistance. Based on these mechanisms, alternative options may be helpful for refractory cases. This review also identifies key pathways in need of further study to optimize menstrual pain treatment.