Biological Sex Differences Research Articles

The sweet side of sex as a biological variable.

Glycobiology as a field holds enormous potential for understanding human health and disease. However, few glycobiology studies adequately address the issue of sex differences in biology, which severely limits the conclusions that can be drawn. Numerous CAZymes, lectins, and other carbohydrate-associated molecules have the potential to be differentially expressed and regulated with sex, leading to differences in O-GlcNAc, N-glycan branching, fucosylation, sialylation, and proteoglycan structure, among others. Expression of proteins involved in glycosylation is influenced through hormones, miRNA, and gene dosage effects. In this review, we discuss the benefits of incorporating sex-based analysis in glycobiology research and the potential drivers of sex differences. We highlight examples of where incorporation of sex-based analysis has led to insights into glycobiology. Finally, we offer suggestions for how to proceed moving forward, even if the experiments are already complete. Properly incorporating sex based analyses into projects will substantially improve the accuracy and reproducibility of studies as well as accelerate the rate of discovery in the glycosciences.

Virologists' Sex- and Gender-Based Medical Knowledge of COVID-19 Affects Quality of Students' Education.

A sex- and gender-based approach to medical education is important to develop new knowledge and to improve quality of and equality within health care. Results of a systematic survey showed a lack of sex- and gender-based medical education at German medical faculties. The global severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) pandemic is affecting people from diverse backgrounds differently, and the reciprocal interactions between biological sex and sociocultural gender aspects with regard to coronavirus disease 2019 (COVID-19) necessitate an intersectional research approach and transfer to medical education. This descriptive-phenomenological qualitative online survey focused on the sex and gender knowledge of faculty staff and the status of implementation in medical education and research at departments of virology and immunology at German university hospitals. It comprised 16 questions generated by an expert consortium based on published research data. In the fall of 2021, 36 leading virologists were invited to participate anonymously in this survey. The response rate was 44%. Most experts deemed sex and gender knowledge as not that important or not important. Almost half the lecturers supported a sex- and gender-based research design and sex-disaggregated analysis of animal study data. Biological sex differences and gender aspects regarding SARS-CoV-2 were at least occasionally addressed upon a student's request. Virologists attributed only minor importance to sex and gender knowledge, despite scientific evidence of sex and gender differences in the field of virology, immunology, and COVID-19 in particular. This knowledge is not systematically implemented in the curriculum, but rather only occasionally passed on to medical students.

Cancer researchers’ perceptions of the importance of the sex of cell lines, animals, and human samples for cancer biology research

Sex differences in cancer risk and outcome are currently a topic of major interest in clinical oncology. It is however unknown to what extent cancer researchers consider sex as a biological variable for their research. We conducted an international survey among 1243 academic cancer researchers and collected both quantitative and qualitative data. Although most of the participants indicated that they were familiar with the concept of studying sex differences in cancer biology, they did not think it was important to investigate sex differences in every context of cancer research nor in all tumor types. This is in stark contrast to the current recommendations and guidelines and illustrates the need for increased awareness among cancer researchers regarding the potential impact of the sex of cell lines, animals, and human samples in their studies.

Sex Differences in Onset and Progression of Cerebral Amyloid Angiopathy.

Cerebral Amyloid Angiopathy (CAA) disease course is highly variable even in hereditary forms. Sex may be a possible modifying factor. We investigated biological sex differences in clinical disease course and magnetic resonance imaging-markers in sporadic (sCAA) and Dutch-type hereditary CAA (D-CAA). Patients with D-CAA and sCAA were included from hospital and research databases of the Leiden University Medical Center (2012-2020) and Massachusetts General Hospital (1994-2012). Key outcomes were: sex differences in symptomatic intracerebral hemorrhage (sICH) onset, recurrence and survival (analyzed using Kaplan Meier survival and regression analyses), and sex differences in magnetic resonance imaging-markers in D-CAA (explored using scatterplots), and in sCAA (investigated using regression analysis). We included 136 patients with D-CAA (mean age 57 years, 56% women, 64% with previous sICH) and 370 patients with sCAA (mean age 76 years, 51% women, all with previous sICH). Men and women with D-CAA did not differ for sICH onset (median age 54 in men and 56 in women [P=0.13]). Men with D-CAA had a slightly higher number of sICH compared with women (median 2 versus 1; adjusted RR, 1.5 [95% CI, 1.1-1.9]) and a shorter interval between the first and second sICH (median 1.8 years for men and 3.1 years for women, P=0.02). Men with sCAA had their first sICH at an earlier age (median 75 versus 78 years, respectively, P=0.003) and more lobar microbleeds (median 1 versus 0, P=0.022) compared with women with sCAA. No substantial differences were found in the other magnetic resonance imaging markers. Survival after first sICH was comparable between sexes for D-CAA (P=0.12) and sCAA (P=0.23). Men with CAA seem to have an earlier onset (sCAA) and more hemorrhagic disease course (sCAA and D-CAA) compared with women. Future studies are necessary to confirm these findings and determine the underlying role of sex-related factors.

Interracial Couples at Risk: Discrimination, Well-Being, and Health

As the number of interracial couples in the U.S. continues to grow, it is important to examine stressors that may lead to decreased well-being and self-rated health due to stigma. Using AddHealth, we conducted ordinary least squares (OLS) regressions to test if individuals in Black/White interracial couples experience (1) higher stress and discriminatory experiences, (2) worse depression and self-rated health, and (3) if depression and self-rated health vary as a function of perceived stress and experiences of discrimination. Biological sex differences were assessed as well. Compared to White couples, interracial couples were, on average, more likely to experience discrimination, and higher perceived stress, more depressive symptoms, and worse overall self-rated health. Our findings suggest a potential mechanism underlying these associations might be through increased stress and discrimination. Future research should further assess additional stressors to understand if interracial couples experience worse health outcomes due to being in a stigmatized relationship.

Age-related changes in antigen-specific natural antibodies are influenced by sex.

Natural antibody (NAb) derived from CD5+ B-1 cells maintains tissue homeostasis, controls inflammation, aids in establishing long-term protective responses against pathogens, and provides immediate protection from infection. CD5+ B-1 cell NAbs recognize evolutionarily fixed epitopes, such as phosphatidylcholine (PtC), found on bacteria and senescent red blood cells. Anti-PtC antibodies are essential in protection against bacterial sepsis. CD5+ B-1 cell-derived NAbs have a unique germline-like structure that lacks N-additions, a feature critical for providing protection against infection. Previously, we demonstrated the repertoire and germline status of PtC+CD5+ B-1 cell IgM obtained from male mice changes with age depending on the anatomical location of the B-1 cells. More recently, we demonstrated serum antibody from aged female mice maintains protection against pneumococcal infection, whereas serum antibody from male mice does not provide protection. Here, we show that aged female mice have significantly more splenic PtC+CD5+ B-1 cells and more PtC specific serum IgM than aged male mice. Furthermore, we find both age and biological sex related repertoire differences when comparing B cell receptor (BCR) sequencing results of PtC+CD5+ B-1 cells. While BCR germline status of PtC+CD5+ B-1 cells from aged male and female mice is similar in the peritoneal cavity, it differs significantly in the spleen, where aged females retain germline configuration and aged males do not. Nucleic acid sensing toll-like receptors are critical in the maintenance of PtC+ B-1 cells; therefore, to begin to understand the mechanism of differences observed between the male and female PtC+CD5+ B-1 cell repertoire, we analyzed levels of cell-free nucleic acids and found increases in aged females. Our results suggest the antigenic milieu differs between aged males and females, leading to differential selection of antigen-specific B-1 cells over time. Further elucidation of how biological sex differences influence the maintenance of B-1 cells within the aging environment will be essential to understand sex and age-related disparities in the susceptibility to bacterial infection and will aid in the development of more effective vaccination and/or therapeutic strategies specific for males and females.

Menstrual phase influences cerebrovascular responsiveness in females but may not affect sex differences.

Background and aims: Sex differences in the rate and occurrence of cerebrovascular diseases (e.g., stroke) indicate a role for female sex hormones (i.e., oestrogen and progesterone) in cerebrovascular function and regulation. However, it remains unclear how cerebrovascular function differs between the sexes, and between distinct phases of the menstrual cycle. This study aimed to compare cerebrovascular-CO2 responsiveness in 1) females during the early follicular (EF), ovulatory (O) and mid-luteal (ML) phases of their menstrual cycle; and 2) males compared to females during phases of lower oestrogen (EF) and higher oestrogen (O). Methods: Eleven females (25 ± 5years) complete experimental sessions in the EF (n = 11), O (n = 9) and ML (n = 11) phases of the menstrual cycle. Nine males (22 ± 3years) completed two experimental sessions, approximately 2weeks apart for comparison to females. Middle and posterior cerebral artery velocity (MCAv, PCAv) was measured at rest, during two stages of hypercapnia (2% and 5% CO2 inhalation) and hypocapnia (voluntary hyperventilation to an end-tidal CO2 of 30 and 24mmHg). The linear slope of the cerebral blood velocity response to changes in end-tidal CO2 was calculated to measure cerebrovascular-CO2 responsiveness.. Results: In females, MCAv-CO2 responsiveness to hypocapnia was lower during EF (-.78 ± .45cm/s/mmHg) when compared to the O phase (-1.17 ± .52cm/s/mmHg; p < .05) and the ML phase (-1.30 ± .82; p < .05). MCAv-CO2 responsiveness to hypercapnia and hypo-to-hypercapnia, and PCAv-CO2 responsiveness across the CO2 range were similar between menstrual phases (p ≥ .20). MCAv-CO2 responsiveness to hypo-to hypercapnia was greater in females compared to males (3.12 ± .91cm/s/mmHg vs. 2.31 ± .46cm/s/mmHg; p = .03), irrespective of menstrual phase (EF or O). Conclusion: Females during O and ML phases have an enhanced vasoconstrictive capacity of the MCA compared to the EF phase. Additionally, biological sex differences can influence cerebrovascular-CO2 responsiveness, dependent on the insonated vessel.

Biological sex and age-related differences shape the antiviral response to SARS-CoV-2 infection

For the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, clinical manifestations are broad and highly heterogeneous for both sexes. We aimed to determine how biological sex and age impact immune gene expression, particularly influencing the humoral neutralizing antibody (NAb) response and the cytokine production in coronavirus disease 2019 (COVID-19) subjects. The immune gene expression, according to biological sex and age, was assessed using the genome wide expression profile of blood proteins from healthy individuals using the Genotype Tissue Expression (GTEx) database. Moreover, anti-SARS-CoV-2 neutralizing antibody titers and cytokine levels were determined in blood samples from 141 COVID-19 individuals from Medellín, Colombia. Among subjects with COVID-19, males had statistically significantly higher median NAb titers and serum concentrations of interleukin-6 and CC chemokine ligand 3 than females. Overall, our findings point out a more robust innate immune response in women that could help recognize and restrain the virus faster than in men.

Biological Sex Differences in Risk Factors and Outcomes Among Hospitalized Adults With Stroke in Lusaka, Zambia.

We investigated sex differences in clinical characteristics and outcomes among hospitalized adults with stroke in Zambia. We retrospectively collected information for 324 consecutively hospitalized adults with stroke on the neurology service at the University Teaching Hospital in Lusaka, Zambia, between October 2018 and March 2019. Stroke characteristics were then compared by biological sex. Female participants constituted 62% (n = 200) of the cohort, were older (61 ± 19 vs 57 ± 16 years, p = 0.06), had fewer hemorrhagic stroke than male participants (22% vs 37%, p = 0.001), and had higher rates of hypertension (84% vs 74%, p = 0.04), diabetes (19% vs 13%, p = 0.04), heart disease (38% vs 27%, p = 0.04), and history of stroke (26% vs 14%, p = 0.01). Male participants had higher rates of alcohol (33% vs 4%, p < 0.001) and tobacco (19% vs 2%, p < 0.001) use. Female participants were less likely to have neuroimaging completed during their hospitalization (82% vs 94%, p = 0.002) and had higher 90 days postdischarge mortality (28% vs 10%, p = 0.002) independent of age and stroke subtype (OR 2.48, 95% CI 1.1-5.58, p = 0.03). Female participants in this Zambian stroke cohort had a higher prevalence of vascular risk factors but were less likely to have neuroimaging completed. Postdischarge mortality was markedly higher among female participants even after adjusting for age and stroke subtype. Our data highlight the need for future studies of social and socioeconomic factors that may influence stroke-related outcomes.

Temporal changes in the microglial proteome of male and female mice after a diffuse brain injury using label-free quantitative proteomics.

Traumatic brain injury (TBI) triggers neuroinflammatory cascades mediated by microglia, which promotes tissue repair in the short-term. These cascades may exacerbate TBI-induced tissue damage and symptoms in the months to years post-injury. However, the progression of the microglial function across time post-injury and whether this differs between biological sexes is not well understood. In this study, we examined the microglial proteome at 3-, 7-, or 28-days after a midline fluid percussion injury (mFPI) in male and female mice using label-free quantitative proteomics. Data are available via ProteomeXchange with identifier PXD033628. We identified a reduction in microglial proteins involved with clearance of neuronal debris via phagocytosis at 3- and 7-days post-injury. At 28 days post-injury, pro-inflammatory proteins were decreased and anti-inflammatory proteins were increased in microglia. These results indicate a reduction in microglial clearance of neuronal debris in the days post-injury with a shift to anti-inflammatory function by 28 days following TBI. The changes in the microglial proteome that occurred across time post-injury did not differ between biological sexes. However, we did identify an increase in microglial proteins related to pro-inflammation and phagocytosis as well as insulin and estrogen signaling in males compared with female mice that occurred with or without a brain injury. Although the microglial response was similar between males and females up to 28 days following TBI, biological sex differences in the microglial proteome, regardless of TBI, has implications for the efficacy of treatment strategies targeting the microglial response post-injury.

Analyzing social wrongs

Analyzing social wrongs

Sexual Dimorphism in Interstitial Lung Disease.

Interstitial lung diseases (ILD) are a group of heterogeneous progressive pulmonary disorders, characterised by tissue remodelling and/or fibrotic scarring of the lung parenchyma. ILD patients experience lung function decline with progressive symptoms, poor response to treatment, reduced quality of life and high mortality. ILD can be idiopathic or associated with systemic or connective tissue diseases (CTD) but idiopathic pulmonary fibrosis (IPF) is the most common form. While IPF has a male predominance, women are affected more greatly by CTD and therefore associated ILDs. The mechanisms behind biological sex differences in these progressive lung diseases remain unclear. However, differences in environmental exposures, variable expression of X-chromosome related inflammatory genes and sex hormones play a role. Here, we will outline sex-related differences in the incidence, progression and mechanisms of action of these diseases and discuss existing and novel cellular and pre-clinical studies. Furthermore, we will highlight how sex-differences are not adequately considered in pre-clinical disease models, how gender bias exists in clinical diagnosis and how women are underrepresented in clinical trials. Future action on these observations will hopefully shed light on the role of biological sex in disease development, identify potential targets for intervention and increase female participant numbers in clinical trials.

A population-based cohort study of sex and risk of severe outcomes in covid-19

There is a male sex disadvantage in morbidity and mortality due to COVID-19. Proposed explanations to this disparity include gender-related health behaviors, differential distribution of comorbidities and biological sex differences. In this study, we investigated the association between sex and risk of severe COVID-19 while adjusting for comorbidities, socioeconomic factors, as well as unmeasured factors shared by cohabitants which are often left unadjusted. We conducted a total-population-based cohort study (n = 1,854,661) based on individual-level register data. Cox models was used to estimate the associations between sex and risk for severe COVID-19. We additionally used a within-household design and conditional Cox models aiming to account for unmeasured factors shared by cohabitants. A secondary aim was to compare the risk of COVID-19 related secondary outcomes between men and women hospitalized due to COVID-19 using logistic regression. Men were at higher risk for hospitalization (HR = 1.63;95%CI = 1.57–1.68), ICU admission (HR = 2.63;95%CI = 2.38–2.91) and death (HR = 1.81;95%CI = 1.68–1.95) due to COVID-19, based on fully adjusted models. However, the effect of sex varied significantly across age groups: Among people in their 50s, men had > four times higher risk of COVID-19 death. The within-household design did not provide any further explanation to the sex disparity. Among patients hospitalized due to COVID-19, men had an increased risk for viral pneumonia, acute respiratory distress syndrome, acute respiratory insufficiency, acute kidney injury, and sepsis which persisted in fully adjusted models. Recognition of the combined effect of sex and age on COVID-19 outcomes has implications for policy strategies to reduce the adverse effects of the disease.

Assessment of Exercise-Associated Gastrointestinal Perturbations in Research and Practical Settings: Methodological Concerns and Recommendations for Best Practice.

Strenuous exercise is synonymous with disturbing gastrointestinal integrity and function, subsequently prompting systemic immune responses and exercise-associated gastrointestinal symptoms, a condition established as "exercise-induced gastrointestinal syndrome." When exercise stress and aligned exacerbation factors (i.e.,extrinsic and intrinsic) are of substantial magnitude, these exercise-associated gastrointestinal perturbations can cause performance decrements and health implications of clinical significance. This potentially explains the exponential growth in exploratory, mechanistic, and interventional research in exercise gastroenterology to understand, accurately measure and interpret, and prevent or attenuate the performance debilitating and health consequences of exercise-induced gastrointestinal syndrome. Considering the recent advancement in exercise gastroenterology research, it has been highlighted that published literature in the area is consistently affected by substantial experimental limitations that may affect the accuracy of translating study outcomes into practical application/s and/or design of future research. This perspective methodological review attempts to highlight these concerns and provides guidance to improve the validity, reliability, and robustness of the next generation of exercise gastroenterology research. These methodological concerns include participant screening and description, exertional and exertional heat stress load, dietary control, hydration status, food and fluid provisions, circadian variation, biological sex differences, comprehensive assessment of established markers of exercise-induced gastrointestinal syndrome, validity of gastrointestinal symptoms assessment tool, and data reporting and presentation. Standardized experimental procedures are needed for the accurate interpretation of research findings, avoiding misinterpreted (e.g.,pathological relevance of response magnitude) and overstated conclusions (e.g.,clinical and practical relevance of intervention research outcomes), which will support more accurate translation into safe practice guidelines.

My story of sex, gender, and women's health in a pandemic.

After more than 20 years of studying sex differences in viral pathogenesis and immunity to vaccines, the COVID‐19 pandemic provided me with a unique opportunity to raise awareness about biological sex differences. The scientific community and public, alike, embraced the clinical and epidemiological data and supported inquiries into how males are twice as likely to be hospitalized and die from COVID‐19. Immunological changes associated with pregnancy also contribute to worse outcomes from COVID‐19. Collectively, we are finding that inflammation is a critical mediator of worse outcomes for males and pregnant females. The pandemic gave me a platform to discuss and address sex differences on a bigger stage, but two decades of studies working with other viruses prepared me for this moment in history.

Sex Differences in Functional Capacity in Older Adults With Stroke: An Analysis of Data From the National Health and Aging Trends Study.

Women experience greater disability following stroke, but biological sex differences in both overall and specific domains of functional capacity are not well understood. The primary objective of this study was to examine sex differences in overall functional capacity (Short Physical Performance Battery [SPPB] score) cross-sectionally and longitudinally over a 3-year follow-up period. The secondary objective was to determine whether sex differences exist in specific domains of functional capacity of walking speed and lower extremity functional strength. This study was a secondary analysis of data of individuals with stroke from the National Health and Aging Trends Study. For the cross-sectional analyses, general linear models were used to examine differences between 293 men and 427 women in SPPB, walking speed, and the 5-Times Sit-to-Stand Test (5XSST). For the longitudinal analysis, survey-weighted, multivariable-adjusted generalized linear mixed models were used to compare 3-year trajectories in SPPB scores between the sexes (87 men, 153 women). Women had lower SPPB scores at baseline (difference = 0.9, linearized SE = 0.3) and over 3years. SPPB scores declined similarly between men and women. Women had lower walking speed (difference = 0.08m/s, SE = 0.02) as compared with men, but men and women had similar 5XSST scores (difference = 0.6seconds, SE = 0.5). Older women with stroke have clinically meaningfully lower overall functional capacity as compared with older men but decline at a similar rate over time. Walking speed was lower in older women with stroke, but similar between sexes in 5XSST. Women with stroke have poorer functional capacity compared with men, which reinforces the importance of targeted stroke rehabilitation strategies to address these sex-specific disparities. Women with stroke have poorer outcomes in terms of their ability to move around the community when compared with men. However, both men and women with stroke have similar physical functioning over time.

Biological sex: an understudied factor driving disease susceptibility in pigs.

Biological sex is a major host factor influencing risk for infectious disease-associated mortality, and chronic inflammatory and metabolic diseases. Research in human and rodent models -has revealed sex differences that exist across organ systems during health and disease that may contribute to sex biases in disease risk. Despite the robust and growing literature on the role of sex as a risk factor in human disease, comparatively little attention has been focused on investigating the role of biological sex in disease susceptibility in agriculturally important animal populations such as the pig. To date, comparisons between sexes have focused on carcass composition, growth rate, and feed efficiency in pigs. However, there is a large gap in the literature regarding the effects of biological sex on other integral aspects of health and disease. The objective of this review is to highlight the available literature reporting sex differences in pig health and biology with an emphasis on sex differences in mortality, immunity, and gastrointestinal (GI) physiology and to address biological sex as a significant biological variable in disease risk and research study design. A basic overview of the biology of sex differences including the major hormonal and genetic/chromosomal mechanisms of sexual differentiation and the developmental periods in which sex differences emerge will be covered. This review will also discuss how production-relevant management and environmental factors (e.g., wean age, castration, stress, and nutrition) interact with biological sex to shape host immune and GI development and function. Perceived gaps in knowledge and areas of future research will also be discussed.

Sex Differences in Performance and Depth of Field in the United States Olympic Trials.

Jobe, TK, Shaffer, HN, Doci, CL, and Gries, KJ. Sex differences in performance and depth of field in the United States Olympic trials. J Strength Cond Res 36(11): 3122-3129, 2022-Recently, there has been an increased discussion on the role of sex as a variable in human performance. Although there likely remains sociological factors, we can estimate biological sex differences in human performance by comparing finishing times in elite men and women. We sought to determine the effect of sex on running and swimming velocity and depth of field in events of varying lengths in the previous 25 years. Finishing times from United States Olympic trials in running events (100 m to marathon) and freestyle swimming (50-1,500 m) from 1996 to 2021 were collected. Sex differences in velocity were calculated for each year (trends), place (first through seventh), and depth of field (nth place/first place). Significance was set at p ≤ 0.05. Men were 9-13% faster than women in all running events (p ≤ 0.05). The 100-m dash (9%) had the lowest sex difference compared with races of longer distance (p ≤ 0.05). In swimming, men were faster in all events (6-12%, p ≤ 0.05), in which sex differences generally decreased with longer distances. Depth of field was similar between men and women in all running and swimming events. No differences in the analyzed variables were observed from 1996 to 2021. These data suggest that elite men are 9% faster in the 100 m compared with running races of longer distances (~12%). Sex differences in swimmers tended to get smaller as duration increased. Although participation and other sociological factors in these events may play a role, these sex differences warrant further discussion on the role of sex in athletic competition.

0320 Sex Differences in Sleep Quality and Biomarker Levels in Service Members and Veterans with Chronic Mild Traumatic Brain Injury

Abstract Introduction Sleep disorders are highly prevalent in military populations and are frequently associated with a history of traumatic brain injury (TBI). Despite the recent increase in female representation in the military, few studies have focused on sex differences in sleep quality in military populations. In this study, we examined biological sex differences in self-reported sleep quality and blood levels of protein biomarkers of TBI in a cohort of service members and veterans with chronic mild TBI (mTBI). Methods Participants (n=1,121) were enrolled in the Chronic Effects of Neurotrauma Consortium (CENC)/Long Term Impact of Military Brain Injury Consortium (LIMBIC) study. Females (n=147) and males (n=974) were classified into control (n=192, no TBI history) or mTBI (n=929, positive history of mTBI) groups. Self-reported sleep quality was assessed using PSQI (Pittsburgh Sleep Quality Index). Plasma levels of glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), Tau, interleukin (IL)-10, IL-6, and tumor necrosis factor-alpha (TNFα) were analyzed using a Simoa HD-X analyzer. Results Regression models revealed higher PSQI scores in females than males (ß(SE)=1.36(0.40), p =0.001) and in the TBI group (ß(SE)=1.97(0.36), p&amp;lt;0.001) in comparison to controls. TBI x sex interaction was not statistically significant. Within the mTBI group, females had higher PSQI scores (p=0.031) and GFAP levels (p&amp;lt;0.001) than males, which remained significant when controlling for demographics, number of mTBIs, and time since last mTBI. No other significant differences in biomarker levels were observed. In men, but not women, higher levels of GFAP were associated with lower PSQI scores (ß(SE)=-1.38(0.43), p=0.001). Conclusion Our findings suggest sex differences in sleep quality after mTBI, providing insights into possible mechanisms underlying the development of chronic symptoms in military populations. Our results support the need for considering biological sex in the development of personalized therapeutic strategies for chronic TBI-related sleep disorders. Support (If Any) This work was supported by grant funding from: The U.S. Army Medical Research and Material Command, from the U.S. Department of Veterans Affairs Long-term Impact of Military-related Brain Injury Consortium/Chronic Effects of Neurotrauma Consortium under Award No.1I01CX002097-01 and the U.S Department of Defense under Award No.W81XWH-18-PH/TBIRP-LIMBIC.

Astrocyte Reactivity in Female Rats with Persistent Low Back Pain Following Spinal Mobilization

Low back pain (LBP) is a physiologically complex and highly disabling condition with poorly understood pathophysiology. Glial reactivity has been reported in patients with chronic LBP and astrocyte reactivity has been suggested as a potential contributor to LBP chronicity.1 Spinal mobilization (SM) is a non‐pharmacological approach with mild to moderate efficacy in treating LBP but physiological mechanisms responsible are unknown.PurposeTo investigate changes in astrocyte reactivity in the upper lumbar spinal cord following SM treatment in a Nerve‐Growth Factor (NGF)‐induced LBP pre‐clinical model. We hypothesize that the administration of trunk NGF will increase astrocyte reactivity, while SM treatment will decrease this reactivity in the upper lumbar spinal cord of female rats.MethodsFemale Sprague Dawley rats (212‐252g) were unilaterally injected with either NGF (50μl;2.0μM) or phosphate buffer saline ‐ PBS (50μl; control) on Days 0 and 5 in the left multifidus muscle under isoflurane anesthesia (1‐2%/2L O2). Ten days lapsed allowing for muscular LBP to develop in NGF animals. Treatment groups (NGF + SM [N=5]; PBS + SM [N=4]) received daily passive SM (10 min) via a feedback motor (1.2Hz, 0.9N) from Days 10 to 16, while the NGF only (N=5) group received no SM treatment. On Day 17, lumbar spinal cord (L1–L3) segments were harvested, fixated, and sectioned at 14μm. Sections were blocked and permeabilized (0.1% Triton X‐100 in 5% donkey serum) for 20 min at room temperature (RT), rinsed in PBS (6 x 5 min), and incubated with primary (Polyclonal Rabbit Anti‐Glial Fibrillary Acidic Protein ‐ 3h at RT) and secondary antibodies (IgG Highly Cross‐Adsorbed Donkey anti‐Rabbit, Alexa Fluor® 488 ‐ 1h at RT). Sections were then mounted on Fluorogel II containing 4′,6‐diamidino‐2‐phenylindole. Images of the superficial dorsal‐horn (laminas I‐III) and deep dorsal‐horn (lamina V) were captured at 20x magnification (Nikon Eclipse). Astrocyte mean fluorescent intensity (MFI) was quantified using FIJI/ImageJ® by blinded lab personnel. Analysis of variance was used to assess the differences in MFI between groups on the left and right sides of the spinal cord dorsal‐horn.ResultsNo significant differences between groups at the superficial horn level was found (p&gt;0.05). Astrocyte MFI was statistically significantly higher in the NGF‐only group when compared to the PBS +SM group at the L3 spinal cord deep‐horn level (p=0.03). SM did not appear to decrease astrocyte reactivity at superficial or deep‐horn spinal cord levels.ConclusionOverall, these preliminary findings suggest that superficial‐horn astrocyte reactivity does not play a large mechanistic role in this female NGF‐induced LBP model despite astrocytic hyperreactivity being demonstrated among male rats with NGF‐induced LBP. Biological sex differences in glial signaling have been reported in other pre‐clinical pain models which may provide an explanation for the non‐significant NGF findings among females. Whether SM acts to decrease astrocyte reactivity in male NGF‐induced LBP rats remains to be investigated.