Human Sex Differences Research Articles

Brain-body mechanisms contribute to sexual dimorphism in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is the most common form of human motor neuron disease. It is characterized by the progressive degeneration of upper and lower motor neurons, leading to generalized motor weakness and, ultimately, respiratory paralysis and death within 3-5 years. The disease is shaped by genetics, age, sex and environmental stressors, but no cure or routine biomarkers exist for the disease. Maleindividuals have a higher propensity to develop ALS, and a different manifestation of the disease phenotype, than femaleindividuals. However, the mechanisms underlying these sex differences remain a mystery. In this Review, we summarize the epidemiology of ALS, examine the sexually dimorphic presentation of the disease and highlight the genetic variants and molecular pathways that might contribute to sex differences in humans and animal models of ALS. We advance the idea that sexual dimorphism in ALS arises from the interactions between the CNS and peripheral organs, involving vascular, metabolic, endocrine, musculoskeletal and immune systems, which are strikingly different between male and femaleindividuals. Finally, we review the response to treatments in ALS and discuss the potential to implement future personalized therapeutic strategies for the disease.

X-chromosome inactivation in human iPSCs provides insight into X-regulated gene expression in autosomes

BackgroundVariation in X chromosome inactivation (XCI) in human-induced pluripotent stem cells (hiPSCs) can impact their ability to model biological sex biases. The gene-wise landscape of X chromosome gene dosage remains unresolved in female hiPSCs. To characterize patterns of de-repression and escape from inactivation, we performed a systematic survey of allele specific expression in 165 female hiPSC lines.ResultsXCI erosion is non-random and primarily affects genes that escape XCI in human tissues. Individual genes and cell lines vary in the frequency and degree of de-repression. Bi-allelic expression increases gradually after modest decrease of XIST in cultures, whose loss is commonly used to mark lines with eroded XCI. We identify three clusters of female lines at different stages of XCI. Increased XCI erosion amplifies female-biased expression at hypomethylated sites and regions normally occupied by repressive histone marks, lowering male-biased differences in the X chromosome. In autosomes, erosion modifies sex differences in a dose-dependent way. Male-biased genes are enriched for hypermethylated regions, and de-repression of XIST-bound autosomal genes in female lines attenuates normal male-biased gene expression in eroded lines. XCI erosion can compensate for a dominant loss of function effect in several disease genes.ConclusionsWe present a comprehensive view of X chromosome gene dosage in hiPSCs and implicate a direct mechanism for XCI erosion in regulating autosomal gene expression in trans. The uncommon and variable reactivation of X chromosome genes in female hiPSCs can provide insight into X chromosome’s role in regulating gene expression and sex differences in humans.

Comparative neuroimaging of sex differences in human and mouse brain anatomy

In vivo neuroimaging studies have established several reproducible volumetric sex differences in the human brain, but the causes of such differences are hard to parse. While mouse models are useful for understanding the cellular and mechanistic bases of sex-specific brain development, there have been no attempts to formally compare human and mouse neuroanatomical sex differences to ascertain how well they translate. Addressing this question would shed critical light on the use of the mouse as a translational model for sex differences in the human brain and provide insights into the degree to which sex differences in brain volume are conserved across mammals. Here, we use structural magnetic resonance imaging to conduct the first comparative neuroimaging study of sex-specific neuroanatomy of the human and mouse brain. In line with previous findings, we observe that in humans, males have significantly larger and more variable total brain volume; these sex differences are not mirrored in mice. After controlling for total brain volume, we observe modest cross-species congruence in the volumetric effect size of sex across 60 homologous regions (r=0.30). This cross-species congruence is greater in the cortex (r=0.33) than non-cortex (r=0.16). By incorporating regional measures of gene expression in both species, we reveal that cortical regions with greater cross-species congruence in volumetric sex differences also show greater cross-species congruence in the expression profile of 2835 homologous genes. This phenomenon differentiates primary sensory regions with high congruence of sex effects and gene expression from limbic cortices where congruence in both these features was weaker between species. These findings help identify aspects of sex-biased brain anatomy present in mice that are retained, lost, or inverted in humans. More broadly, our work provides an empirical basis for targeting mechanistic studies of sex-specific brain development in mice to brain regions that best echo sex-specific brain development in humans.

Comparative neuroimaging of sex differences in human and mouse brain anatomy.

In vivo neuroimaging studies have established several reproducible volumetric sex differences in the human brain, but the causes of such differences are hard to parse. While mouse models are useful for understanding the cellular and mechanistic bases of sex-specific brain development, there have been no attempts to formally compare human and mouse neuroanatomical sex differences to ascertain how well they translate. Addressing this question would shed critical light on the use of the mouse as a translational model for sex differences in the human brain and provide insights into the degree to which sex differences in brain volume are conserved across mammals. Here, we use structural magnetic resonance imaging to conduct the first comparative neuroimaging study of sex-specific neuroanatomy of the human and mouse brain. In line with previous findings, we observe that in humans, males have significantly larger and more variable total brain volume; these sex differences are not mirrored in mice. After controlling for total brain volume, we observe modest cross-species congruence in the volumetric effect size of sex across 60 homologous regions (r=0.30). This cross-species congruence is greater in the cortex (r=0.33) than non-cortex (r=0.16). By incorporating regional measures of gene expression in both species, we reveal that cortical regions with greater cross-species congruence in volumetric sex differences also show greater cross-species congruence in the expression profile of 2835 homologous genes. This phenomenon differentiates primary sensory regions with high congruence of sex effects and gene expression from limbic cortices where congruence in both these features was weaker between species. These findings help identify aspects of sex-biased brain anatomy present in mice that are retained, lost, or inverted in humans. More broadly, our work provides an empirical basis for targeting mechanistic studies of sex-specific brain development in mice to brain regions that best echo sex-specific brain development in humans.

Effects of resistance training and protein supplementation interventions on muscle volume and muscle function: sex differences in humans.

This review aimed to identify differences in the effects of co-intervention with resistance training (RT) and protein supplementation according to sex and provide meaningful information for future research on the development of exercise programs to improve muscle volume and muscle function. PubMed, Science Direct, and Google Scholar were searched to identify clinical and nonclinical studies that assessed the effects of RT in older adults with sarcopenia; these studies were published between 1990 and 2023. Cross-sectional and double-blind studies (randomized controlled trials, RCTs) were examined in this review. The effects of parallel intervention with RT and protein supplementation on muscle volume and physical function were found to differ according to sex. Both males and females had improvements in muscle strength, muscle mass, and physical function after RT and protein supplementation; however, many studies found a greater increase in muscle volume and function in males than in females. Such difference may be due to differences in physiological characteristics between males and females. Based on the findings of this review, the effects of combined intervention with RT and protein supplementation on muscle strength, muscle mass, and physical function to differ according to sex. Owing to these sex differences in the response and physiological characteristics caused by the parallel intervention of RT and protein supplementation, such differences must be considered to maximize the effects of RT and protein supplementation.

Out of the Silence: Insights into How Genes Escape X-Chromosome Inactivation.

The silencing of all but one X chromosome in mammalian cells is a remarkable epigenetic process leading to near dosage equivalence in X-linked gene products between the sexes. However, equally remarkable is the ability of a subset of genes to continue to be expressed from the otherwise inactive X chromosome-in some cases constitutively, while other genes are variable between individuals, tissues or cells. In this review we discuss the advantages and disadvantages of the approaches that have been used to identify escapees. The identity of escapees provides important clues to mechanisms underlying escape from XCI, an arena of study now moving from correlation to functional studies. As most escapees show greater expression in females, the not-so-inactive X chromosome is a substantial contributor to sex differences in humans, and we highlight some examples of such impact.

Effects of Resistance Exercise on Older Individuals with Sarcopenia: Sex Differences in Humans

Sarcopenia affects tens of millions of adults worldwide, with a reported prevalence of 10-50% among older adults. A decrease in muscle strength and function due to aging reduces physical performance, causing pain and disease. Accordingly, interest in the treatment or prevention of sarcopenia through resistance exercises, which have been found to be effective in improving muscle strength and hypertrophy, is increasing. However, given the individual differences, it is difficult to determine the optimal RE method. Currently, the importance of personalized resistance exercise (RE) prescriptions is emphasized, and research on sex/gender differences needs to be conducted. Our review focused on the effects of resistance exercise on muscle strength, muscle hypertrophy, and muscle function in older adults in relation to sex differences. In this review, we aimed to analyze sex differences in the effect of RE on older adults with sarcopenia and provide meaningful information for future research on exercise programs for individuals with sarcopenia.

Prepubertal castration eliminates sex differences in lifespan and growth trajectories in genetically heterogeneous mice.

Sex differences in aging and longevity have been widely observed, with females consistently outliving males across human populations. However, the mechanisms driving these disparities remain poorly understood. In this study, we explored the influence of post-pubertal testicular effects on sex differences in aging by prepubertally castrating genetically heterogeneous (UM-HET3) mice, a unique mouse model that emulates human sex differences in age-related mortality. Prepubertal castration eliminated the longevity disparity between sexes by reducing the elevated early- to mid-life mortality rate observed in males and extending their median lifespan to match that of females. Additionally, castration extended the duration of body weight growth and attenuated the inverse correlation between early-age body weight and lifespan in males, aligning their growth trajectories with those of females. Our findings suggest that post-pubertal testicular actions in genetically diverse mice are primarily responsible for sex differences in longevity as well as growth trajectories. These findings offer a foundation for further investigation into the fundamental mechanisms driving sex-specific aging patterns and the development of potential pro-longevity interventions.

Sex differences in hippocampal β-amyloid accumulation in the triple-transgenic mouse model of Alzheimer's disease and the potential role of local estrogens.

Epidemiological studies show that women have a higher prevalence of Alzheimer's disease (AD) than men. Peripheral estrogen reduction during aging in women is proposed to play a key role in this sex-associated prevalence, however, the underlying mechanism remains elusive. We previously found that transcription factor early growth response-1 (EGR1) significantly regulates cholinergic function. EGR1 stimulates acetylcholinesterase (AChE) gene expression and is involved in AD pathogenesis. We aimed to investigate whether the triple-transgenic AD (3xTg-AD) mice harboring PS1 M146V , APP Swe , and Tau P301L show sex differences in β-amyloid (Aβ) and hyperphosphorylated tau (p-Tau), the two primary AD hallmarks, and how local 17β-estradiol (E2) may regulate the expression of EGR1 and AChE. We first sacrificed male and female 3xTg-AD mice at 3-4, 7-8, and 11-12 months and measured the levels of Aβ, p-Tau, EGR1, and AChE in the hippocampal complex. Second, we infected SH-SY5Y cells with lentivirus containing the amyloid precursor protein construct C99, cultured with or without E2 administration we measured the levels of extracellular Aβ and intracellular EGR1 and AChE. Female 3xTg-AD mice had higher levels of Aβ compared to males, while no p-Tau was found in either group. In SH-SY5Y cells infected with lentivirus containing the amyloid precursor protein construct C99, we observed significantly increased extracellular Aβ and decreased expression of intracellular EGR1 and AChE. By adding E2 to the culture medium, extracellular Aβ(l-42) was significantly decreased while intracellular EGR1 and AChE expression were elevated. This data shows that the 3xTg-AD mouse model can be useful for studying the human sex differences of AD, but only in regards to Ap. Furthermore, in vitro data shows local E2 may be protective for EGR1 and cholinergic functions in AD while suppressing soluble Aβ(1-42) levels. Altogether, this study provides further in vivo and in vitro data supporting the human epidemiological data indicating a higher prevalence of AD in women is related to changes in brain estrogen levels.

Monkeys do not show sex differences in toy preferences through their individual choices

BackgroundAs interest in evaluating sex differences in nonhuman animals grows, the finding that male and female monkeys have toy preferences that differ, and that parallel those documented in human children, has garnered significant attention and is leveraged as an argument in favor of a biological contribution for human sex differences. To date, however, only two studies have investigated sex differences in monkeys’ toy preferences, both documenting that males prefer toys considered to be “masculine” (such as vehicles) and females prefer toys considered to be “feminine” (such as dolls). Monkeys in these studies were tested in their social groups, making it hard to determine if the sex differences reported reflect actual individual preferences or result from social dynamics present at the time of testing.MethodHere, we assessed the preferences of 14 rhesus macaques (N = 7 males; N = 7 females) who were singly tested in a choice test with a variety of toys characterized as masculine (hard non-zoomorphic wheeled toys), feminine (zoomorphic soft toys), neutral (hard non-zoomorphic toys) and ambiguous (zoomorphic or plush vehicles) based on criteria from previous studies.ResultsMales and females showed similar preferences for neutral and “masculine” toys and preferred them (i.e., were more likely to interact with them) to “feminine” and sex-ambiguous toys. When they interacted with the toys, both males and females interacted more with neutral than with “masculine” toys. Females, but not males, interacted more with neutral and “masculine” toys than with “feminine” toys. The highest frequency of interaction for any single toy for the male monkeys was with the doll—standing is stark contrast to previous findings.ConclusionsOur results contrast greatly with the previous study in rhesus monkeys, as well as findings in human children, suggesting that the previously documented sex differences are likely context dependent, and question the existence of a strong biological basis to sex differences in toy preferences.

Harshening stem cell research and precision medicine: The states of human pluripotent cells stem cell repository diversity, and racial and sex differences in transcriptomes.

In vitro investigation on human development, disease modeling, and drug discovery has been empowered by human induced pluripotent stem cell (hiPSC) technologies that form the foundation of precision medicine. Race and sex genetic backgrounds have become a major focus of many diseases modeling and drug response evaluation in the pharmaceutical industry. Here, we gathered data from major stem cell repositories to analyze the diversity with respect to ethnicity, sex, and disease types; and we also analyzed public datasets to unravel transcriptomics differences between samples of different ethnicities and sexes. We found a lack of diversity despite the large sample size of human induced pluripotent stem cells. In the ethnic comparison, the White group made up the majority of the banked hiPSCs. Similarly, for the organ/disease type and sex comparisons, the neural and male hiPSCs accounted for the majority of currently available hiPSCs. Bulk RNA-seq and single-cell transcriptomic analysis coupled with Machine Learning and Network Analysis revealed panels of gene features differently expressed in healthy hiPSCs and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) of different races and sexes. The data highlights the current ethnic and sex inequality in stem cell research and demonstrates the molecular biological diversity of hiPSCs and cardiomyocytes from different races and genders. We postulate that future efforts in stem cell biology, regenerative and precision medicine should be guided towards an inclusive, diverse repository reflecting the prevalence of diseases across racial and ethnic groups and the sexes, important for both common and rare disease modeling, drug screening, and cell therapeutics.

Age-dependent sex difference of non-alcoholic fatty liver disease in TSOD and db/db mice.

According to previous clinical studies, the prevalence of non-alcoholic fatty liver disease (NAFLD) is higher in men than women only during the reproductive age. Animal models of NAFLD that reflect sex differences in humans have not been established. In this study, we examined sex differences in the hepatic lesions of Tsumura Suzuki obese diabetes (TSOD) and db/db mice, which are representative genetic models of NAFLD. Male and female TSOD and db/db mice were fed with a normal diet and tap water ad libitum. Six male and female mice of each strain were sacrificed at the ages of 3 and 9 months, respectively, and serum biochemical, pathological, and molecular analyses were performed. Serum aspartate aminotransferase (AST) levels were significantly higher in male than female mice of both strains at the age of 3 months; however, at 9 months, significant sex differences were not observed. Similarly, alanine aminotransferase (ALT) levels were significantly higher in male mice than in female TSOD mice at the age of 3 months; however, at 9 months, significant sex differences were not observed. Image analysis of histological slides revealed that the frequency of the steatotic area was significantly higher in male than female db/db mice at the age of 3 months; however, significant sex differences were not observed at 9 months. The frequency of Sirius red-positive fibrotic area was significantly higher in male than female mice in both strains at the age of 3 months; however, significant sex differences were not observed at 9 months. Serum AST and ALT levels and hepatic steatosis and fibrosis in TSOD and db/db mice showed age-dependent sex differences consistent with those observed in human NAFLD. These mice may be suitable for studying sex differences of the disease.

Modeling sex differences in humans using isogenic induced pluripotent stemcells.

Biological sex is a fundamental trait influencing development, reproduction, pathogenesis, and medical treatment outcomes. Modeling sex differences is challenging because of the masking effect of genetic variability and the hurdle of differentiating chromosomal versus hormonal effects. In this work we developed a cellular model to study sex differences in humans. Somatic cells from a mosaic Klinefelter syndrome patient were reprogrammed to generate isogenic induced pluripotent stem cell (iPSC) lines with different sex chromosome complements: 47,XXY/46,XX/46,XY/45,X0. Transcriptional analysis of the hiPSCs revealed novel and known genes and pathways that are sexually dimorphic in the pluripotent state and during early neural development. Female hiPSCs more closely resembled the naive pluripotent state than their male counterparts. Moreover, the system enabled differentiation between the contributions of X versus Y chromosome to these differences. Taken together, isogenic hiPSCs present a novel platform for studying sex differences in humans and bear potential to promote gender-specific medicine in the future.

Neuroinflammatory profiles of the human female brain in midlife resembles the human male late‐life Alzheimer's brain

AbstractNicole Delatorre & Hannah Van Rossum are co‐first authorsBackgroundNeuroinflammation is a well‐documented feature of Alzheimer’s Disease (AD). Two important questions in defining the role of the neuroimmune system in AD remain unaddressed: 1) the initiation phase of inflammation and 2) sex differences in the inflammatory cascade. Previous preclinical findings from our group demonstrated elevated inflammatory and immune transcripts including CD3, CD4, and MHCII. With this work, we extend and translate our preclinical discoveries to test the hypotheses that the inflammatory phenotype of LOAD is initiated in midlife of the human aging process and sex differences are prevalent.MethodBoth fixed and frozen human tissue samples were obtained from NIH NeuroBioBank (University of Maryland, University of Miami, and Mt. Sinai) that included the corpus callosum, hippocampus, and hypothalamus of 40 brain donors that were sex and age matched. For the purposes of this study, samples were sub‐classified into 3 groups: healthy aging 40‐49 years‐old, healthy aging 50‐59 years‐old, and AD age 60‐80 years‐old. Transcriptomic analyses were conducted to determine neuroinflammatory gene expression and to identify common signaling profiles. Neuroinflammatory markers were visualized using 3,3’‐diaminobenzidine immunohistochemistry and included microglia (IBA‐1), activated microglia (HLA), and T‐cells (CD3, CD4, CD8).ResultGene expression change was determined by comparing each group to the young male. The profiles were compared using fisher exact tests and revealed region‐specific and sex‐specific transcript regulation. Midlife females exhibited significant differences in genes involved in hypothalamic adaptive immune response (p=0.0054), hippocampal astrocyte function p=0.007, and hypothalamic inflammatory signaling p=0.028). AD males exhibited altered gene expression in corpus callosum neurotransmission (p=0.0355), hippocampal innate immune response, and hypothalamic adaptive and innate immune response (p=0.0496, p=0.0208). Both midlife female and AD male showed hippocampal upregulation of innate immune transcripts and hypothalamic upregulation of adaptive and innate immune response genes.ConclusionThese results provide evidence of early activation of the immune response in brain as a potential sex‐dependent risk factor for AD. Outcomes of these analyses support future studies that identify neuroimmune biomarkers of the AD prodrome and present an early opportunity for intervention in order to reduce risk and/or delay AD.NIH: R01AG057931, R01AG057931‐02S1, T32AG061897, R01AG057931‐01A1

Gene essentiality in cancer cell lines is modified by the sex chromosomes.

Human sex differences arise from gonadal hormones and sex chromosomes. Studying the direct effects of sex chromosomes in humans is still challenging. Here we studied how the sex chromosomes can modulate gene expression and the outcome of mutations across the genome by exploiting the tendency of cancer cell lines to lose or gain sex chromosomes. We inferred the dosage of the sex chromosomes in 355 female and 408 male cancer cell lines and used it to dissect the contributions of the Y and X Chromosomes to sex-biased gene expression. Furthermore, based on genome-wide CRISPR screens, we identified genes whose essentiality is different between male and female cells depending on the sex chromosomes. The most significant genes were X-linked genes compensated by Y-linked paralogs. Our sex-based analysis identifies genes that, when mutated, can affect male and female cells differently and reinforces the roles of the X and Y Chromosomes in sex-specific cell function.

Is digit ratio (2D:4D) associated with a religious profession? An exploratory study on male Polish seminary students

Human females demonstrate higher religiosity than men in populations. Digit ratio (2D:4D), being a putative indicator of prenatal testosterone, is associated in varying degrees with characters that show sexual dimorphism. A small number of studies have indicated that religiosity may be associated with the biological basis of sex differences in humans. The objective of the present study was to ascertain whether 2D:4D in religiously oriented seminary students is different from individuals in other occupations. The study followed a cross-sectional design. Male participants of the study included 13 seminary students, 18 military chaplains and 91 control students from study courses relating to civil occupations. Lengths of second (2D) and fourth (4D) digits and their ratio (2D:4D) for each hand, height and weight were the variables and 2D:4D was the outcome measure. The results demonstrated that the seminary students had significantly higher 2D:4D than both the military chaplains and civil students. The military chaplains had the lowest 2D:4D. The study also revealed that the choice of religious occupation, and for that matter, religiosity, could be linked with the prenatal hormonal environment, particularly lower intrauterine testosterone compared to oestrogen.

Sex differences in the impact of pain, morphine administration and morphine withdrawal on quality of life in rats

The disruptive effects of pain on quality of life are greater in men than in women, but the disruptive effects of opioid administration and withdrawal tend to be greater in women. These sex differences in pain, acute opioid effects, and opioid withdrawal tend to be opposite to sex differences reported in laboratory rats. We hypothesized that sex differences in humans and rats would more closely align if animal research measured quality of life as opposed to traditional evoked behaviors of pain (e.g., nociceptive reflexes) and opioid withdrawal (e.g., wet dog shakes). The present study assessed quality of life in adult female and male rats by measuring voluntary wheel running in the rat's home cage. Hindpaw inflammation induced by administration of Complete Freund's Adjuvant (CFA) into the right hindpaw caused a greater depression of wheel running in male compared to female rats. Twice daily injections of high morphine doses (5–20 mg/kg) and the subsequent morphine withdrawal caused a greater depression of wheel running in female compared to male rats. These sex differences are consistent with human data that shows the impact of pain on quality of life is greater in men than women, but the negative effects of opioid administration and withdrawal are greater in women. The present data indicate that the clinical significance of animal research would be enhanced by shifting the endpoint from pain and opioid evoked behaviors to measures of quality of life such as voluntary wheel running.

Cardiometabolic Disease Results in Sex‐ and Age‐Dependent Cerebrovascular Degeneration and Arteriolar Morphological Changes

ABSTRACT In the past 20 years, no drug therapies have been successfully translated into human use for intracerebral hemorrhage (ICH), the most devastating stroke subset. One likely factor is lack of effective animal models of human disease including common comorbidities, such as hypertension and diabetes. We evaluated the cardiometabolic rodent model, (mRen2)27, where overexpression of Ren2 results in extreme hypertension, glucose intolerance and obesity, as an appropriate ICH model. Methods: Sprague Dawley (SD) and (mRen2)27 rats were sacrificed at 14‐, 32‐, and 52‐weeks. Brains were sectioned sagittally at 5 μm. Whole‐brain sections were stained using Hematoxylin & Eosin (H&E) and Van Geison (VG) collagen staining to visualize the pial blood vessels. Wall‐to‐lumen ratios for vessels were calculated and compared using a student t‐test to determine significance. Results: There was no significant difference in arteriolar morphology at 14‐weeks between male SD and mRen animals (SD, n=16 and mRen, n=16). At 32‐weeks, there was a significant difference in mRen male rats (SD, n=13 and mRen, n=17; p<0.0001), with significantly increased wall thickness and decreased Lumen size in the mRen animals (increased W:L ratio). However, at this timeframe, there was no significant difference between the female SD and mRen cohorts (SD, n=6 and mRen, n=8). At 52‐weeks, there was a significant increase in W:L ratios in both male (SD, n=4 and mRen, n=7; p<0.01) and female (SD, n=9 and mRen, n=8; p<0.05) mRen animals compared to control. Conclusion: The (mRen2)27 cardiometabolic animal model demonstrates age‐related sex changes in the wall:lumen ratio of cerebral vasculature consistent with cerebrovascular disease seen in ischemic and hemorrhagic stroke patients. Males develop these vascular changes earlier than females, but both sexes in this model develop cerebral vascular changes by 1 year of age. The (mRen2)27 model appears to recapitulate human disease and sex differences, and may serve as an appropriate translational model of ICH.

Penalized decomposition using residuals (PeDecURe) for feature extraction in the presence of nuisance variables.

Neuroimaging data are an increasingly important part of etiological studies of neurological and psychiatric disorders. However, mitigating the influence of nuisance variables, including confounders, remains a challenge in image analysis. In studies of Alzheimer's disease, for example, an imbalance in disease rates by age and sex may make it difficult to distinguish between structural patterns in the brain (as measured by neuroimaging scans) attributable to disease progression and those characteristic of typical human aging or sex differences. Concerningly, when not properly accounted for, nuisance variables pose threats to the generalizability and interpretability of findings from these studies. Motivated by this critical issue, in this work, we examine the impact of nuisance variables on feature extraction methods and propose Penalized Decomposition Using Residuals (PeDecURe), a new method for obtaining nuisance variable-adjusted features. PeDecURe estimates primary directions of variation which maximize covariance between partially residualized imaging features and a variable of interest (e.g., Alzheimer's diagnosis) while simultaneously mitigating the influence of nuisance variation through a penalty on the covariance between partially residualized imaging features and those variables. Using features derived using PeDecURe's first direction of variation, we train a highly accurate and generalizable predictive model, as evidenced by its robustness in testing samples with different underlying nuisance variable distributions. We compare PeDecURe to commonly used decomposition methods (principal component analysis (PCA) and partial least squares) as well as a confounder-adjusted variation of PCA. We find that features derived from PeDecURe offer greater accuracy and generalizability and lower correlations with nuisance variables compared with the other methods. While PeDecURe is primarily motivated by challenges that arise in the analysis of neuroimaging data, it is broadly applicable to data sets with highly correlated features, where novel methods to handle nuisance variables are warranted.

Combining Antiandrogens with Immunotherapy for Bladder Cancer Treatment

BackgroundMen are three to four times more likely to be diagnosed with bladder cancer (BCa) than women, who often have more aggressive tumors. Intravesical bacillus Calmette-Guerin (BCG) for non–muscle-invasive bladder cancer (NMIBC) is one of the first immunotherapies, with use of immune checkpoint inhibitors for BCa immunotherapy expanding. Sex hormones, and notably androgens, might impact the outcome of these therapies. ObjectiveTo understand immunological sex differences in BCa and investigate androgen receptor (AR) inhibition as a novel strategy to improve the response to BCa immunotherapy. Design, setting, and participantsHuman NMIBC tumors were freshly collected following transurethral resection. In vivo studies used the subcutaneous MBT-2 BCa model in male and female C3H mice. The AR antagonist enzalutamide was given alone or in combination with anti–programmed cell death protein-1 (anti–PD-1) or intratumoral BCG + poly(I:C) treatments. Outcome measurements and statistical analysisTumor growth and survival were evaluated in vivo. Flow cytometry and RNA sequencing characterized the immune cells present in murine and human tumors. Descriptive comparisons were performed for MBT-2 tumors between sexes and with human NMIBC tumors. Results and limitationsThe MBT-2 model shows multiple similarities to the immune composition of human NMIBC tumors and recapitulates previously observed human tumor immune cell sex differences. Enzalutamide in combination with either anti–PD-1 or BCG + poly(I:C) treatment in male mice synergized to improve response rates. Notably, the proportion of complete responses in male mice treated with the combination treatment resembles that observed in female mice with either immunotherapy alone. Limitations include the sample size for murine experiments. ConclusionsOur results suggest that combining AR antagonism with immunotherapy in male BCa patients may potentiate the antitumor immune response and increase response rates. The MBT-2 model appears relevant to investigate immunological BCa sex differences. Patient summaryOur studies suggest that combining antiandrogen treatments with BCa immunotherapy may improve response rates in men. We also demonstrate the utility of the MBT-2 mouse model to study sex differences in BCa.