Limb proportions show developmental plasticity in response to embryo movement

Interruption of the Intratumor CD8:Treg Crosstalk Improves the Efficacy of PD-1 Immunotherapy

PD-1 blockade unleashes the potent antitumor activity of CD8 cells but can also promote immunosuppressive T regulatory (Treg) cells, which may worsen response to immunotherapy. Tumor Treg inhibition is a promising strategy to overcome therapeutic resistance; however, the mechanisms supporting tumor Tregs during PD-1 immunotherapy are largely unexplored. Here, we report that PD-1 blockade increases tumor Tregs in mouse models of immunogenic tumors, including melanoma, and metastatic melanoma patients. Unexpectedly, Treg accumulation was not caused by Treg-intrinsic inhibition of PD-1 signaling but instead depended on an indirect effect of activated CD8 cells. CD8 cells colocalized with Tregs within tumors and produced IL-2, especially after PD-1 immunotherapy. IL-2 upregulated the anti-apoptotic protein ICOS on tumor Tregs, causing their accumulation. ICOS signaling inhibition before PD-1 immunotherapy resulted in increased control of immunogenic melanoma. Thus, interrupting the intratumor CD8:Treg crosstalk is a novel strategy that may enhance the efficacy of immunotherapy in patients.

Comparative single-cell analyses identify shared and divergent features of human and mouse kidney development

Mammalian kidneys maintain fluid homeostasis through the cellular activity of nephrons and the conjoined collecting system. Each epithelial network originates from distinct progenitor cell populations that reciprocally interact during development. To extend our understanding of human and mouse kidney development, we profiled chromatin organization (ATAC-seq) and gene expression (RNA-seq) in developing human and mouse kidneys. Data were analyzed at a species level and then integrated into a common, cross-species multimodal data set. Comparative analysis of cell types and developmental trajectories identified conserved and divergent features of chromatin organization and linked gene activity, revealing species- and cell-type specific regulatory programs. Identification of human-specific enhancer regions linked through GWAS studies to kidney disease highlights the potential of developmental modeling to provide clinical insight.

Proteomic Pathways across Ejection Fraction Spectrum in Heart Failure: an EXSCEL Substudy

Background

Ejection fraction (EF) is a key component of heart failure (HF) classification, including the increasingly codified HF with mildly reduced EF (HFmrEF) category. However, the biologic basis of HFmrEF as an entity distinct from HF with preserved EF (HFpEF) and reduced EF (HFrEF) has not been well characterized.

Methods

The EXSCEL trial randomized participants with type 2 diabetes (T2DM) to once-weekly exenatide (EQW) vs. placebo. For this study, profiling of ∼5000 proteins using the SomaLogic SomaScan platform was performed in baseline and 12-month serum samples from N=1199 participants with prevalent HF at baseline. Principal component analysis (PCA) and ANOVA (FDR p<0.1) were used to determine differences in proteins between three EF groups, as previously curated in EXSCEL (EF>55% [HFpEF], EF 40-55% [HFmrEF], EF<40% [HFrEF]). Cox proportional hazards was used to assess association between baseline levels of significant proteins, and changes in protein level between baseline and 12-month, with time-to-HF hospitalization. Mixed models were used to assess whether significant proteins changed differentially with exenatide vs. placebo therapy.

Results

Of N=1199 EXSCEL participants with prevalent HF, 284 (24%), 704 (59%) and 211 (18%) had HFpEF, HFmrEF and HFrEF, respectively. Eight PCA protein factors and 221 individual proteins within these factors differed significantly across the three EF groups. Levels of the majority of proteins (83%) demonstrated concordance between HFmrEF and HFpEF, but higher levels in HFrEF, predominated by the domain of extracellular matrix regulation, e.g. COL28A1 and tenascin C [TNC]; p<0.0001. Concordance between HFmrEF and HFrEF was observed in a minority of proteins (1%) including MMP-9 (p<0.0001). Biologic pathways of epithelial mesenchymal transition, ECM receptor interaction, complement and coagulation cascades, and cytokine receptor interaction demonstrated enrichment among proteins with the dominant pattern, i.e. HFmrEF-HFpEF concordance. Baseline levels of 208 (94%) of the 221 proteins were associated with time-to-incident HF hospitalization including domains of extracellular matrix (COL28A1, TNC), angiogenesis (ANG2, VEGFa, VEGFd), myocyte stretch (NT-proBNP), and renal function (cystatin-C). Change in levels of 10 of the 221 proteins from baseline to 12 months (including increase in TNC) predicted incident HF hospitalization (p<0.05). Levels of 30 of the 221 significant proteins (including TNC, NT-proBNP, ANG2) were reduced differentially by EQW compared with placebo (interaction p<0.0001).

Conclusions

In this HF substudy of a large clinical trial of people with T2DM, we found that serum levels of most proteins across multiple biologic domains were similar between HFmrEF and HFpEF. HFmrEF may be more biologically similar to HFpEF than HFrEF, and specific related biomarkers may offer unique data on prognosis and pharmacotherapy modification with variability by EF.

Long ant life span is maintained by a unique heat shock factor

Eusocial insect reproductive females show strikingly longer life spans than nonreproductive female workers despite high genetic similarity. In the ant Harpegnathos saltator (Hsal), workers can transition to reproductive "gamergates," acquiring a fivefold prolonged life span by mechanisms that are poorly understood. We found that gamergates have elevated expression of heat shock response (HSR) genes in the absence of heat stress and enhanced survival with heat stress. This HSR gene elevation is driven in part by gamergate-specific up-regulation of the gene encoding a truncated form of a heat shock factor most similar to mammalian HSF2 (hsalHSF2). In workers, hsalHSF2 was bound to DNA only upon heat stress. In gamergates, hsalHSF2 bound to DNA even in the absence of heat stress and was localized to gamergate-biased HSR genes. Expression of hsalHSF2 in Drosophila melanogaster led to enhanced heat shock survival and extended life span in the absence of heat stress. Molecular characterization illuminated multiple parallels between long-lived flies and gamergates, underscoring the centrality of hsalHSF2 to extended ant life span. Hence, ant caste-specific heat stress resilience and extended longevity can be transferred to flies via hsalHSF2. These findings reinforce the critical role of proteostasis in health and aging and reveal novel mechanisms underlying facultative life span extension in ants.

Time-varying association between cigarette and ENDS use on incident hypertension among US adults: a prospective longitudinal study

OBJECTIVE

Electronic nicotine delivery systems (ENDS) products have emerged as the most popular alternative to combustible cigarettes. However, ENDS products contain potentially dangerous toxicants and chemical compounds, and little is known about their health effects. The aim of the present study was to examine the prospective association between cigarette and ENDS use on self-reported incident hypertension.

DESIGN

Longitudinal cohort study.

SETTING

Nationally representative sample of the civilian, non-institutionalised population in the USA.

PARTICIPANTS

17 539 adults aged 18 or older who participated at follow-up and had no self-reported heart condition or previous diagnosis of hypertension or high cholesterol at baseline.

MEASURES

We constructed a time-varying tobacco exposure, lagged by one wave, defined as no use, exclusive established use (every day or some days) of ENDS or cigarettes, and dual use. We controlled for demographics (age, sex, race/ethnicity and household income), clinical risk factors (family history of heart attack, obesity, diabetes and binge drinking) and smoking history (cigarette pack-years).

OUTCOMES

Self-reported incident hypertension diagnosis.

RESULTS

The self-reported incidence of hypertension was 3.7% between wave 2 and wave 5. At baseline, 18.0% (n=5570) of respondents exclusively smoked cigarettes; 1.1% (n=336) exclusively used ENDS; and 1.7% (n=570) were dual users. In adjusted models, exclusive cigarette use was associated with an increased risk of self-reported incident hypertension compared with non-use (adjusted HR (aHR) 1.21, 95% CI 1.06 to 1.38), while exclusive ENDS use (aHR 1.00, 95% CI 0.68 to 1.47) and dual use (aHR 1.15, 95% CI 0.87 to 1.52) were not.

CONCLUSIONS

We found that smoking increased the risk of self-reported hypertension, but ENDS use did not. These results highlight the importance of using prospective longitudinal data to examine the health effects of ENDS use.

Aged Breast Matrix Bound Vesicles Promote Breast Cancer Invasiveness

Aging is one of the inherent risk factors for breast cancer. Although the influence of age-related cellular alterations on breast cancer development has been extensively explored, little is known about the alterations in the aging breast tissue microenvironment, specifically the extracellular matrix (ECM). Here, for the first time in literature, we have identified tissue resident matrix bound vesicles (MBVs) within the healthy mouse breast ECM, investigated and compared their characteristics in young and aged healthy breast tissues, and studied the effects of these MBVs on normal (KTB21) and cancerous (MDA-MB-231) human mammary epithelial cells with respect to the tissue age that they are extracted from. Using vesicle labeling technology, we were able to visualize cellular uptake of the MBVs directly from the native decellularized tissue sections, showing that these MBVs have regulatory roles in the tissue microenvironment. We mimicked the ECM by embedding the MBVs in collagen gels, and showed that MBVs could be taken up by the cells. The miRNA and cytokine profiling showed that MBVs shifted towards a more tumorigenic and invasive phenotype with age, as evidenced by the more pronounced presence of cancer-associated cytokines, and higher expression levels of oncomiRs miR-10b, miR-30e, and miR-210 in MBVs isolated from aged mice. When treated with MBVs or these upregulated factors, KTB21 and MDA-MB-231 cells showed significantly higher motility and invasion compared to untreated controls. Treatment of cells with a cocktail of miRNAs (miR-10b, miR-30e, and miR-210) or with the agonist of adiponectin (AdipoRon), which both were enriched in the aged MBVs, recapitulated the effect of aged MBVs on cells. This study shows for the first time that the MBVs have a regulatory role in the tissue microenvironment and that the MBV contents change towards cancer-promoting upon aging. Studying the effects of MBVs and their cargos on cellular behavior could lead to a better understanding of the critical roles of MBVs played in breast cancer progression and metastasis.

Bifurcation occlusions and endovascular treatment outcome in acute ischemic stroke

BACKGROUND

A thrombus in the M1 segment of the middle cerebral artery (MCA) can occlude this main stem only or extend into the M1-M2 bifurcation. The occlusion pattern may affect endovascular treatment (EVT) success, as a bifurcated thrombus may be more prone to fragmentation during retrieval.

OBJECTIVE

To investigate whether bifurcated thrombus patterns are associated with EVT procedural and clinical outcomes.

METHODS

Occlusion patterns of MCA thrombi on CT angiography from MR CLEAN Registry patients were classified into three groups: main stem occlusion, bifurcation occlusion extending into one M2 branch, and bifurcation occlusion extending into both M2 branches. Procedural parameters, procedural outcomes (reperfusion grade and embolization to new territory), and clinical outcomes (24-48 hour National Institutes of Health Stroke Scale [NIHSS_FU] score, change in NIHSS scores between 24 and 48 hours and baseline ∆ [NIHSS], and 90-day modified Rankin Scale [mRS] scores) were compared between occlusion patterns.

RESULTS

We identified 1023 patients with an MCA occlusion of whom 370 (36%) had a main stem occlusion, 151 (15%) a single branch, and 502 (49%) a double branch bifurcation occlusion. There were no statistically significant differences in retrieval method, procedure time, number of retrieval attempts, reperfusion grade, and embolization to new territory between occlusion patterns. Patients with main stem occlusions had lower NIHSS_FU scores than patients with single (7 vs 11, p=0.01) or double branch occlusions (7 vs 9, p=0.04). However, there were no statistically significant differences in ∆ NIHSS or in 90-day mRS scores.

CONCLUSIONS

In our population, EVT procedural and long-term clinical outcomes were similar for MCA bifurcation occlusions and MCA main stem occlusions.

Barriers to immune cell infiltration in tumors

Increased immune cell infiltration into tumors is associated with improved patient survival and predicts response to immune therapies. Thus, identification of factors that determine the extent of immune infiltration is crucial, so that methods to intervene on these targets can be developed. T cells enter tumor tissues through the vasculature, and under control of interactions between homing receptors on the T cells and homing receptor ligands (HRLs) expressed by tumor vascular endothelium and tumor cell nests. HRLs are often deficient in tumors, and there also may be active barriers to infiltration. These remain understudied but may be crucial for enhancing immune-mediated cancer control. Multiple intratumoral and systemic therapeutic approaches show promise to enhance T cell infiltration, including both approved therapies and experimental therapies. This review highlights the intracellular and extracellular determinants of immune cell infiltration into tumors, barriers to infiltration, and approaches for intervention to enhance infiltration and response to immune therapies.

Targeting wild-type IDH1 enhances chemosensitivity in pancreatic cancer

Pancreatic cancer (PC) is one of the most aggressive types of cancer, with a five-year overall survival rate of 11% among all-comers. Current systemic therapeutic options are limited to cytotoxic chemotherapies which have limited clinical efficacy and are often associated with development of drug resistance. Analysis of The Cancer Genome Atlas showed that wild-type isocitrate dehydrogenase (wtIDH1) is overexpressed in pancreatic tumors. In this study, we focus on the potential roles of wtIDH1 in pancreatic cancer chemoresistance. We found that treatment of pancreatic cancer cells with chemotherapy induced expression of wtIDH1, and this serves as a key resistance factor. The enzyme is protective to cancer cells under chemotherapy-induced oxidative stress by producing NADPH and alpha-ketoglutarate to maintain redox balance and mitochondrial function. An FDA-approved mutant IDH1 inhibitor, ivosidenib (AG-120), is actually a potent wtDH1 inhibitor under a nutrient-deprived microenvironment, reflective of the pancreatic cancer microenvironment. Suppression of wtIDH1 impairs redox balance, results in increased ROS levels, and enhances chemotherapy induced apoptosis in pancreatic cancer vis ROS damage in vitro. In vivo experiments further revealed that inhibiting wtIDH1 enhances chemotherapy anti-tumor effects in patient-derived xenografts and murine models of pancreatic cancer. Pharmacologic wtIDH1 inhibition with ivosidenib represents an attractive option for combination therapies with cytotoxic chemotherapy for patients with pancreatic cancer. Based on these data, we have initiated phase Ib trial combining ivosidenib and multi-agent chemotherapy in patients with pancreatic cancer (NCT05209074).

Highly Parallel Tissue Grafting for Combinatorial In Vivo Screening

Material- and cell-based technologies such as engineered tissues hold great promise as human therapies. Yet, the development of many of these technologies becomes stalled at the stage of pre-clinical animal studies due to the tedious and low-throughput nature of in vivo implantation experiments. We introduce a 'plug and play' in vivo screening array platform called Highly Parallel Tissue Grafting (HPTG). HPTG enables parallelized in vivo screening of 43 three-dimensional microtissues within a single 3D printed device. Using HPTG, we screen microtissue formations with varying cellular and material components and identify formulations that support vascular self-assembly, integration and tissue function. Our studies highlight the importance of combinatorial studies that vary cellular and material formulation variables concomitantly, by revealing that inclusion of stromal cells can "rescue" vascular self-assembly in manner that is material-dependent. HPTG provides a route for accelerating pre-clinical progress for diverse medical applications including tissue therapy, cancer biomedicine, and regenerative medicine.

Impact of Socioeconomic Status on Amygdala and Hippocampus Subdivisions in Children and Adolescents

Socioeconomic status (SES) in childhood can impact behavioral and brain development. Past work has consistently focused on the amygdala and hippocampus, two brain areas critical for emotion and behavioral responding. While there are SES differences in amygdala and hippocampal volumes, there are many unanswered questions in this domain connected to neurobiological specificity, and for whom these effects may be more pronounced. We may be able to investigate some anatomical subdivisions of these brain areas, as well as if relations with SES vary by participant age and sex. No work to date has however completed these types of analyses. To overcome these limitations, here, we combined multiple, large neuroimaging datasets of children and adolescents with information about neurobiology and SES (N=2,765). We examined subdivisions of the amygdala and hippocampus and found multiple amygdala subdivisions, as well as the head of the hippocampus, were related to SES. Greater volumes in these areas were seen for higher-SES youth participants. Looking at age- and sex-specific subgroups, we tended to see stronger effects in older participants, for both boys and girls. Paralleling effects for the full sample, we see significant positive associations between SES and volumes for the accessory basal amygdala and head of the hippocampus. We more consistently found associations between SES and volumes of the hippocampus and amygdala in boys (compared to girls). We discuss these results in relation to conceptions of "sex-as-a-biological variable" and broad patterns of neurodevelopment across childhood and adolescence. These results fill in important gaps on the impact of SES on neurobiology critical for emotion, memory, and learning.

Characterization of spatiotemporal dynamics of binary and graded tonic pain in humans using intracranial recordings

Pain is a complex experience involving sensory, emotional, and cognitive aspects, and multiple networks manage its processing in the brain. Examining how pain transforms into a behavioral response can shed light on the networks' relationships and facilitate interventions to treat chronic pain. However, studies using high spatial and temporal resolution methods to investigate the neural encoding of pain and its psychophysical correlates have been limited. We recorded from intracranial stereo-EEG (sEEG) electrodes implanted in sixteen different brain regions of twenty patients who underwent psychophysical pain testing consisting of a tonic thermal stimulus to the hand. Broadband high-frequency local field potential amplitude (HFA; 70-150 Hz) was isolated to investigate the relationship between the ongoing neural activity and the resulting psychophysical pain evaluations. Two different generalized linear mixed-effects models (GLME) were employed to assess the neural representations underlying binary and graded pain psychophysics. The first model examined the relationship between HFA and whether the patient responded "yes" or "no" to whether the trial was painful. The second model investigated the relationship between HFA and how painful the stimulus was rated on a visual analog scale. GLMEs revealed that HFA in the inferior temporal gyrus (ITG), superior frontal gyrus (SFG), and superior temporal gyrus (STG) predicted painful responses at stimulus onset. An increase in HFA in the orbitofrontal cortex (OFC), SFG, and striatum predicted pain responses at stimulus offset. Numerous regions including the anterior cingulate cortex, hippocampus, IFG, MTG, OFC, and striatum, predicted the pain rating at stimulus onset. However, only the amygdala and fusiform gyrus predicted increased pain ratings at stimulus offset. We characterized the spatiotemporal representations of binary and graded painful responses during tonic pain stimuli. Our study provides evidence from intracranial recordings that the neural encoding of psychophysical pain changes over time during a tonic thermal stimulus, with different brain regions being predictive of pain at the beginning and end of the stimulus.

T-cell activation, senescence, and exhaustion in asymptomatic HIV/Leishmania infantum co-infection

Background

Leishmania infantum is an opportunistic parasitic infection. An immunocompromised state increases the risk of converting asymptomatic infection to symptomatic visceral leishmaniasis (VL), which has a ~5% fatality rate even with treatment. HIV coinfection increases the risk of death from VL.

Methods

A cross-sectional study was performed between 2014 and 2016 to determine the prevalence of L. infantum infection in HIV positive subjects residing in the state of Rio Grande do Norte, Brazil (n=1,372) and of these a subgroup of subjects were followed longitudinally. Subsequent incident cases of VL were ascertained from a public health database through 2018. A subgroup (n=69) of the cross-sectional study subjects was chosen to assess immune status (T cell activation, senescence, exhaustion) and outcome. The data were compared between asymptomatic HIV+/L. infantum+ (HIV/Leish), symptomatic visceral leishmaniasis (VL), recovered VL, DTH+ (Delayed-Type Hypersensitivity response - Leishmanin skin test), AIDS/VL, HIV+ only (HIV+), and Non-HIV/Non L. infantum infection (control subjects).

Results

The cross-sectional study showed 24.2% of HIV+ subjects had positive anti-IgG Leishmania antibodies. After 3 years, 2.4% (8 of 333) of these HIV/Leish coinfected subjects developed AIDS/VL, whereas 1.05% (11 of 1,039) of HIV subjects with negative leishmania serology developed AIDS/VL. Poor adherence to antiretroviral therapy (p=0.0008) or prior opportunistic infections (p=0.0007) was associated with development of AIDS/VL. CD4+ (p=0.29) and CD8+ (p=0.38) T cells counts or viral load (p=0.34) were similar between asymptomatic HIV/Leish and HIV subjects. However, activated CD8+CD38+HLA-DR+ T cells were higher in asymptomatic HIV/Leish than HIV group. Likewise, senescent (CD57+) or exhausted (PD1+) CD8+ T cells were higher in asymptomatic HIV/Leish than in AIDS/VL or HIV groups.

Conclusion

Although asymptomatic HIV/Leish subjects had normal and similar CD4+ and CD8+ T cells counts, their CD8+T cells had increased activation, senescence, and exhaustion, which could contribute to risk of developing VL.

Language Experience during Infancy Predicts White Matter Myelination at Age 2 Years

Parental input is considered a key predictor of language achievement during the first years of life, yet relatively few studies have assessed the effects of parental language input and parent-infant interactions on early brain development. We examined the relationship between measures of parent and child language, obtained from naturalistic home recordings at child ages 6, 10, 14, 18, and 24 months, and estimates of white matter myelination, derived from quantitative MRI at age 2 years (mean = 26.30 months, SD = 1.62, N = 22). Analysis of the white matter focused on dorsal pathways associated with expressive language development and long-term language ability, namely, the left arcuate fasciculus (AF) and superior longitudinal fasciculus (SLF). Frequency of parent-infant conversational turns (CT) uniquely predicted myelin density estimates in both the AF and SLF. Moreover, the effect of CT remained significant while controlling for total adult speech and child speech-related utterances, suggesting a specific role for interactive language experience, rather than simply speech exposure or production. An exploratory analysis of 18 additional tracts, including the right AF and SLF, indicated a high degree of anatomic specificity. Longitudinal analyses of parent and child language variables indicated an effect of CT as early as 6 months of age, as well as an ongoing effect over infancy. Together, these results link parent-infant conversational turns to white matter myelination at age 2 years, and suggest that early, interactive experiences with language uniquely contribute to the development of white matter associated with long-term language ability.SIGNIFICANCE STATEMENT Children's earliest experiences with language are thought to have profound and lasting developmental effects. Recent studies suggest that intervention can increase the quality of parental language input and improve children's learning outcomes. However, important questions remain about the optimal timing of intervention, and the relationship between specific aspects of language experience and brain development. We report that parent-infant turn-taking during home language interactions correlates with myelination of language related white matter pathways through age 2 years. Effects were independent of total speech exposure and infant vocalizations and evident starting at 6 months of age, suggesting that structured language interactions throughout infancy may uniquely support the ongoing development of brain systems critical to long-term language ability.

GATA4 and GATA6 loss-of-expression is associated with extinction of the classical programme and poor outcome in pancreatic ductal adenocarcinoma

OBJECTIVE

GATA6 is a key regulator of the classical phenotype in pancreatic ductal adenocarcinoma (PDAC). Low GATA6 expression associates with poor patient outcome. GATA4 is the second most expressed GATA factor in the pancreas. We assessed whether, and how, GATA4 contributes to PDAC phenotype and analysed the association of expression with outcome and response to chemotherapy.

DESIGN

We analysed PDAC transcriptomic data, stratifying cases according to GATA4 and GATA6 expression and identified differentially expressed genes and pathways. The genome-wide distribution of GATA4 was assessed, as well as the effects of GATA4 knockdown. A multicentre tissue microarray study to assess GATA4 and GATA6 expression in samples (n=745) from patients with resectable was performed. GATA4 and GATA6 levels were dichotomised into high/low categorical variables; association with outcome was assessed using univariable and multivariable Cox regression models.

RESULTS

GATA4 messenger RNA is enriched in classical, compared with basal-like tumours. We classified samples in 4 groups as high/low for GATA4 and GATA6. Reduced expression of GATA4 had a minor transcriptional impact but low expression of GATA4 enhanced the effects of GATA6 low expression. GATA4 and GATA6 display a partially overlapping genome-wide distribution, mainly at promoters. Reduced expression of both proteins in tumours was associated with the worst patient survival. GATA4 and GATA6 expression significantly decreased in metastases and negatively correlated with basal markers.

CONCLUSIONS

GATA4 and GATA6 cooperate to maintain the classical phenotype. Our findings provide compelling rationale to assess their expression as biomarkers of poor prognosis and therapeutic response.

Novel insights into the contribution of plastoglobules and reactive oxygen species to chromoplast differentiation

Plant tissues can be enriched in phytonutrients not only by stimulating their biosynthesis but also by providing appropriate sink structures for their sequestering and storage. In the case of carotenoids, they accumulate at high levels in chromoplasts naturally found in flowers and fruit. Chromoplasts can also be artificially differentiated from leaf chloroplasts by boosting carotenoid production with the bacterial protein crtB. Here we used electron and confocal microscopy together with subplastidial fractionation and transcript, protein and metabolite analyses to analyze the structural and biochemical changes occurring in crtB-induced artificial chromoplasts and their impact on the accumulation of health-related isoprenoids. We show that leaf chromoplasts develop plastoglobules (PG) harboring high levels of carotenoids (mainly phytoene and pro-vitamin A β-carotene) but also other nutritionally relevant isoprenoids, such as tocopherols (vitamin E) and phylloquinone (vitamin K1). Further promoting PG proliferation by exposure to intense (high) light resulted in a higher accumulation of these health-related metabolites but also an acceleration of the chloroplast-to-chromoplast conversion. We further show that the production of reactive oxygen species (ROS) stimulates chromoplastogenesis. Our data suggest that carotenoid accumulation and ROS production are not just consequences but promoters of the chromoplast differentiation process.

A pillar/perfusion plate enhances cell growth, reproducibility, throughput, and user friendliness in dynamic 3D cell culture

Static three-dimensional (3D) cell culture has been demonstrated in ultralow attachment well plates, hanging droplet plates, and microtiter well plates with hydrogels or magnetic nanoparticles. Although it is simple, reproducible, and relatively inexpensive, thus potentially used for high-throughput screening, statically cultured 3D cells often suffer from the necrotic core due to limited nutrient and oxygen diffusion and waste removal and have limited in vivo-like tissue structure. Here, we overcome these challenges by developing a pillar/perfusion plate platform and demonstrating high-throughput, dynamic 3D cell culture. Cell spheroids have been loaded on the pillar plate with hydrogel by simple sandwiching and encapsulation and cultured dynamically in the perfusion plate on a digital rocker. Unlike traditional microfluidic devices, fast flow rates were maintained within perfusion wells, and the pillar plate could be separated from the perfusion plate for cell-based assays. It was compatible with common lab equipment and allowed cell culture, testing, staining, and imaging in situ. The pillar/perfusion plate enhanced cell growth by rapid diffusion, reproducibility, assay throughput, and user friendliness in dynamic 3D cell culture.

Cellular Senescence Is Immunogenic and Promotes Antitumor Immunity

Cellular senescence is a stress response that activates innate immune cells, but little is known about its interplay with the adaptive immune system. Here, we show that senescent cells combine several features that render them highly efficient in activating dendritic cells (DC) and antigen-specific CD8 T cells. This includes the release of alarmins, activation of IFN signaling, enhanced MHC class I machinery, and presentation of senescence-associated self-peptides that can activate CD8 T cells. In the context of cancer, immunization with senescent cancer cells elicits strong antitumor protection mediated by DCs and CD8 T cells. Interestingly, this protection is superior to immunization with cancer cells undergoing immunogenic cell death. Finally, the induction of senescence in human primary cancer cells also augments their ability to activate autologous antigen-specific tumor-infiltrating CD8 lymphocytes. Our study indicates that senescent cancer cells can be exploited to develop efficient and protective CD8-dependent antitumor immune responses.

SIGNIFICANCE

Our study shows that senescent cells are endowed with a high immunogenic potential-superior to the gold standard of immunogenic cell death. We harness these properties of senescent cells to trigger efficient and protective CD8-dependent antitumor immune responses. See related article by Chen et al., p. 432. This article is highlighted in the In This Issue feature, p. 247.

Activation of AKT induces EZH2-mediated β-catenin trimethylation in colorectal cancer

Colorectal cancer (CRC) develops in part through the deregulation of different signaling pathways, including activation of the WNT/β-catenin and PI3K/AKT pathways. Enhancer of zeste homolog 2 (EZH2) is a lysine methyltransferase that is involved in regulating stem cell development and differentiation and is overexpressed in CRC. However, depending on the study EZH2 has been found to be both positively and negatively correlated with the survival of CRC patients suggesting that EZH2's role in CRC may be context specific. In this study, we explored how PI3K/AKT activation alters EZH2's role in CRC. We found that activation of AKT by PTEN knockdown or by hydrogen peroxide treatment induced EZH2 phosphorylation at serine 21. Phosphorylation of EZH2 resulted in EZH2-mediated methylation of β-catenin and an associated increased interaction between β-catenin, TCF1, and RNA polymerase II. AKT activation increased β-catenin's enrichment across the genome and EZH2 inhibition reduced this enrichment by reducing the methylation of β-catenin. Furthermore, PTEN knockdown increased the expression of epithelial-mesenchymal transition (EMT)-related genes, and somewhat unexpectedly EZH2 inhibition further increased the expression of these genes. Consistent with these findings, EZH2 inhibition enhanced the migratory phenotype of PTEN knockdown cells. Overall, we demonstrated that EZH2 modulates AKT-induced changes in gene expression through the AKT/EZH2/ β-catenin axis in CRC with active PI3K/AKT signaling. Therefore, it is important to consider the use of EZH2 inhibitors in CRC with caution as these inhibitors will inhibit EZH2-mediated methylation of histone and non-histone targets such as β-catenin, which can have tumor-promoting effects.

Identification and characterization of a proliferative cell population in estrogen receptor-positive metastatic breast cancer through spatial and single-cell transcriptomics

Background

Intratumor heterogeneity is a hallmark of most solid tumors, including breast cancers. We applied spatial transcriptomics and single-cell RNA-sequencing technologies to profile spatially resolved cell populations within estrogen receptor-positive (ER ⁺ ) metastatic breast cancers and elucidate their importance in estrogen-dependent tumor growth.

Methods

Spatial transcriptomics and single-cell RNA-sequencing were performed on two patient-derived xenografts (PDXs) of "ER-high" metastatic breast cancers with opposite estrogen-mediated growth responses: estrogen-suppressed GS3 (80-100% ER) and estrogen-stimulated SC31 (30-75% ER) models. The analyses included samples treated with and without 17β-estradiol. The findings were validated via scRNA-seq analyses on "ER-low" estrogen-accelerating PDX, GS1 (5% ER). The results from our spatial and single-cell analyses were further supported by the analysis of a publicly available single cell dataset and a protein-based dual immunohistochemical (IHC) evaluation using three important clinical markers [i.e., ER, progesterone receptor (PR), and Ki67]. The translational implication of these results was assessed by clinical outcome analyses on public breast cancer cohorts.

Results

Our novel space-gene-function study revealed a "proliferative" cell population in addition to three major spatially distinct compartments within ER ⁺ metastatic breast cancers. These compartments showed functional diversity (i.e., estrogen-responsive, proliferative, hypoxia-induced, and inflammation-related). The "proliferative ( MKI67 ⁺ )" population, not "estrogen-responsive" compartment, was crucial for estrogen-dependent tumor growth, leading to the acquisition of luminal B features. The cells with induction of typical estrogen-responsive genes such as PGR were not directly linked to estrogen-dependent proliferation. Additionally, the dual IHC analyses demonstrated the distinct contribution of the Ki67 ⁺ proliferative cells toward estrogen-mediated growth and their response to palbociclib, a CDK4/6 inhibitor. The gene signatures developed from the proliferative, hypoxia-induced, and inflammation-related compartments were significantly correlated with worse clinical outcomes, while patients with the high estrogen-responsive scores showed better prognosis, confirming that the estrogen-responsive compartment would not be directly associated with estrogen-dependent tumor progression.

Conclusions

For the first time, our study elucidated a "proliferative" cell population distinctly distributed in ER ⁺ metastatic breast cancers. They contribute differently toward progression of these cancers, and the gene signature in the "proliferative" compartment is an important determinant of luminal cancer subtypes.

A modular plasmid toolkit applied in marine Proteobacteria reveals functional insights during bacteria-stimulated metamorphosis

A conspicuous roadblock to studying marine bacteria for fundamental research and biotechnology is a lack of modular synthetic biology tools for their genetic manipulation. Here, we applied, and generated new parts for, a modular plasmid toolkit to study marine bacteria in the context of symbioses and host-microbe interactions. To demonstrate the utility of this plasmid system, we genetically manipulated the marine bacterium Pseudoalteromonas luteoviolacea , which stimulates the metamorphosis of the model tubeworm, Hydroides elegans . Using these tools, we quantified constitutive and native promoter expression, developed reporter strains that enable the imaging of host-bacteria interactions, and used CRISPR interference (CRISPRi) to knock down a secondary metabolite and a host-associated gene. We demonstrate the broader utility of this modular system for rapidly creating and iteratively testing genetic tractability by modifying marine bacteria that are known to be associated with diverse host-microbe symbioses. These efforts enabled the successful transformation of twelve marine strains across two Proteobacteria classes, four orders and ten genera. Altogether, the present study demonstrates how synthetic biology strategies enable the investigation of marine microbes and marine host-microbe symbioses with broader implications for environmental restoration and biotechnology.

The nanoscale organization of reticulon 4 shapes local endoplasmic reticulum structure in situ

The endoplasmic reticulum’s (ER) structure is directly linked to the many functions of the ER but its formation is not fully understood. We investigate how the ER-membrane curving protein reticulon 4 (Rtn4) localizes to and organizes in the membrane and how that affects local ER structure. We show a strong correlation between the local Rtn4 density and the local ER membrane curvature. Our data further reveal that the typical ER tubule possesses an elliptical cross-section with Rtn4 enriched at either end of the major axis. Rtn4 oligomers are linear-shaped, contain about five copies of the protein, and preferentially orient parallel to the tubule axis. Our observations support a mechanism in which oligomerization leads to an increase of the local Rtn4 concentration with each molecule increasing membrane curvature through a hairpin wedging mechanism. This quantitative analysis of Rtn4 and its effects on the ER membrane result in a new model of tubule shape as it relates to Rtn4.

SUMMARY

Rtn4 forms linear-shaped oligomers that contain an average of five Rtn4 proteins, localize to the sides of elliptical tubules, prefer orientations near parallel to the tubule axis, and increase local curvature of the ER membrane by increasing local Rtn4 density.

Disentangling Object Category Representations Driven by Dynamic and Static Visual Input

Humans can label and categorize objects in a visual scene with high accuracy and speed, a capacity well characterized with studies using static images. However, motion is another cue that could be used by the visual system to classify objects. To determine how motion-defined object category information is processed by the brain in the absence of luminance-defined form information, we created a novel stimulus set of "object kinematograms" to isolate motion-defined signals from other sources of visual information. Object kinematograms were generated by extracting motion information from videos of 6 object categories and applying the motion to limited-lifetime random dot patterns. Using functional magnetic resonance imaging (fMRI) (n = 15, 40% women), we investigated whether category information from the object kinematograms could be decoded within the occipitotemporal and parietal cortex and evaluated whether the information overlapped with category responses to static images from the original videos. We decoded object category for both stimulus formats in all higher-order regions of interest (ROIs). More posterior occipitotemporal and ventral regions showed higher accuracy in the static condition, while more anterior occipitotemporal and dorsal regions showed higher accuracy in the dynamic condition. Further, decoding across the two stimulus formats was possible in all regions. These results demonstrate that motion cues can elicit widespread and robust category responses on par with those elicited by static luminance cues, even in ventral regions of visual cortex that have traditionally been associated with primarily image-defined form processing.SIGNIFICANCE STATEMENT Much research on visual object recognition has focused on recognizing objects in static images. However, motion is a rich source of information that humans might also use to categorize objects. Here, we present the first study to compare neural representations of several animate and inanimate objects when category information is presented in two formats: static cues or isolated dynamic motion cues. Our study shows that, while higher-order brain regions differentially process object categories depending on format, they also contain robust, abstract category representations that generalize across format. These results expand our previous understanding of motion-derived animate and inanimate object category processing and provide useful tools for future research on object category processing driven by multiple sources of visual information.

Pre- and Post-Portosystemic Shunt Placement Metabolomics Reveal Molecular Signatures for the Development of Hepatic Encephalopathy

Hepatic encephalopathy (HE) is a common complication of advanced liver disease causing brain dysfunction. This is likely due to the accumulation of unfiltered toxins within the bloodstream. A known risk factor for developing or worsening HE is the placement of a transjugular intrahepatic portosystemic shunt (TIPS), which connects the pre-hepatic and post-hepatic circulation allowing some blood to bypass the dysfunctional liver and decreases portal hypertension. To better understand the pathophysiology of post-TIPS HE, we conducted a multi-center prospective cohort study employing metabolomic analyses on hepatic vein and peripheral vein blood samples from participants with cirrhosis undergoing elective TIPS placement, measuring chemical modifications and changes in concentrations of metabolites resulting from TIPS placement. In doing so, we identified numerous alterations in metabolites, including bile acids, glycerophosphocholines, and bilirubins possibly implicated in the development and severity of HE.

Look who's TORking: mTOR-mediated integration of cell status and external signals during limb development and endochondral bone growth

The balance of cell proliferation and size is key for the control of organ development and repair. Moreover, this balance has to be coordinated within tissues and between tissues to achieve robustness in the organ's pattern and size. The tetrapod limb has been used to study these topics during development and repair, and several conserved pathways have emerged. Among them, mechanistic target of rapamycin (mTOR) signaling, despite being active in several cell types and developmental stages, is one of the least understood in limb development, perhaps because of its multiple potential roles and interactions with other pathways. In the body of this review, we have collated and integrated what is known about the role of mTOR signaling in three aspects of tetrapod limb development: 1) limb outgrowth; 2) chondrocyte differentiation after mesenchymal condensation and 3) endochondral ossification-driven longitudinal bone growth. We conclude that, given its ability to interact with the most common signaling pathways, its presence in multiple cell types, and its ability to influence cell proliferation, size and differentiation, the mTOR pathway is a critical integrator of external stimuli and internal status, coordinating developmental transitions as complex as those taking place during limb development. This suggests that the study of the signaling pathways and transcription factors involved in limb patterning, morphogenesis and growth could benefit from probing the interaction of these pathways with mTOR components.

Single-cell RNA sequencing reveals intrahepatic and peripheral immune characteristics related to disease phases in HBV-infected patients

OBJECTIVE

A comprehensive immune landscape for HBV infection is pivotal to achieve HBV cure.

DESIGN

We performed single-cell RNA sequencing of 2 43 000 cells from 46 paired liver and blood samples of 23 individuals, including six immune tolerant, 5 immune active (IA), 3 acute recovery (AR), 3 chronic resolved and 6 HBV-free healthy controls (HCs). Flow cytometry and histological assays were applied in a second HBV cohort for validation.

RESULTS

Both IA and AR were characterised by high levels of intrahepatic exhausted CD8+ T (Tex) cells. In IA, Tex cells were mainly derived from liver-resident GZMK+ effector memory T cells and self-expansion. By contrast, peripheral CX3CR1+ effector T cells and GZMK+ effector memory T cells were the main source of Tex cells in AR. In IA but not AR, significant cell-cell interactions were observed between Tex cells and regulatory CD4+ T cells, as well as between Tex and FCGR3A+ macrophages. Such interactions were potentially mediated through human leukocyte antigen class I molecules together with their receptors CANX and LILRBs, respectively, contributing to the dysfunction of antiviral immune responses. By contrast, CX3CR1+GNLY+ central memory CD8+ T cells were concurrently expanded in both liver and blood of AR, providing a potential surrogate marker for viral resolution. In clinic, intrahepatic Tex cells were positively correlated with serum alanine aminotransferase levels and histological grading scores.

CONCLUSION

Our study dissects the coordinated immune responses for different HBV infection phases and provides a rich resource for fully understanding immunopathogenesis and developing effective therapeutic strategies.

Advancing human gut microbiota research by considering gut transit time

Accumulating evidence indicates that gut transit time is a key factor in shaping the gut microbiota composition and activity, which are linked to human health. Both population-wide and small-scale studies have identified transit time as a top covariate contributing to the large interindividual variation in the faecal microbiota composition. Despite this, transit time is still rarely being considered in the field of the human gut microbiome. Here, we review the latest research describing how and why whole gut and segmental transit times vary substantially between and within individuals, and how variations in gut transit time impact the gut microbiota composition, diversity and metabolism. Furthermore, we discuss the mechanisms by which the gut microbiota may causally affect gut motility. We argue that by taking into account the interindividual and intraindividual differences in gut transit time, we can advance our understanding of diet-microbiota interactions and disease-related microbiome signatures, since these may often be confounded by transient or persistent alterations in transit time. Altogether, a better understanding of the complex, bidirectional interactions between the gut microbiota and transit time is required to better understand gut microbiome variations in health and disease.

Building a Co-ordinated Musculoskeletal System: The Plasticity of the Developing Skeleton in Response to Muscle Contractions

The skeletal musculature and the cartilage, bone and other connective tissues of the skeleton are intimately co-ordinated. The shape, size and structure of each bone in the body is sculpted through dynamic physical stimuli generated by muscle contraction, from early development, with onset of the first embryo movements, and through repair and remodelling in later life. The importance of muscle movement during development is shown by congenital abnormalities where infants that experience reduced movement in the uterus present a sequence of skeletal issues including temporary brittle bones and joint dysplasia. A variety of animal models, utilising different immobilisation scenarios, have demonstrated the precise timing and events that are dependent on mechanical stimulation from movement. This chapter lays out the evidence for skeletal system dependence on muscle movement, gleaned largely from mouse and chick immobilised embryos, showing the many aspects of skeletal development affected. Effects are seen in joint development, ossification, the size and shape of skeletal rudiments and tendons, including compromised mechanical function. The enormous plasticity of the skeletal system in response to muscle contraction is a key factor in building a responsive, functional system. Insights from this work have implications for our understanding of morphological evolution, particularly the challenging concept of emergence of new structures. It is also providing insight for the potential of physical therapy for infants suffering the effects of reduced uterine movement and is enhancing our understanding of the cellular and molecular mechanisms involved in skeletal tissue differentiation, with potential for informing regenerative therapies.

Epigenetic modulation of neuroblastoma enhances T cell and NK cell immunogenicity by inducing a tumor-cell lineage switch

BACKGROUND

Immunotherapy in high-risk neuroblastoma (HR-NBL) does not live up to its full potential due to inadequate (adaptive) immune engagement caused by the extensive immunomodulatory capacity of HR-NBL. We aimed to tackle one of the most notable immunomodulatory processes in neuroblastoma (NBL), absence of major histocompatibility complex class I (MHC-I) surface expression, a process greatly limiting cytotoxic T cell engagement. We and others have previously shown that MHC-I expression can be induced by cytokine-driven immune modulation. Here, we aimed to identify tolerable pharmacological repurposing strategies to upregulate MHC-I expression and therewith enhance T cell immunogenicity in NBL.

METHODS

Drug repurposing libraries were screened to identify compounds enhancing MHC-I surface expression in NBL cells using high-throughput flow cytometry analyses optimized for adherent cells. The effect of positive hits was confirmed in a panel of NBL cell lines and patient-derived organoids. Compound-treated NBL cell lines and organoids were cocultured with preferentially expressed antigen of melanoma (PRAME)-reactive tumor-specific T cells and healthy-donor natural killer (NK) cells to determine the in vitro effect on T cell and NK cell cytotoxicity. Additional immunomodulatory effects of histone deacetylase inhibitors (HDACi) were identified by transcriptome and translatome analysis of treated organoids.

RESULTS

Drug library screening revealed MHC-I upregulation by inhibitor of apoptosis inhibitor (IAPi)- and HDACi drug classes. The effect of IAPi was limited due to repression of nuclear factor kappa B (NFκB) pathway activity in NBL, while the MHC-I-modulating effect of HDACi was widely translatable to a panel of NBL cell lines and patient-derived organoids. Pretreatment of NBL cells with the HDACi entinostat enhanced the cytotoxic capacity of tumor-specific T cells against NBL in vitro, which coincided with increased expression of additional players regulating T cell cytotoxicity (eg, TAP1/2 and immunoproteasome subunits). Moreover, MICA and MICB, important in NK cell cytotoxicity, were also increased by entinostat exposure. Intriguingly, this increase in immunogenicity was accompanied by a shift toward a more mesenchymal NBL cell lineage.

CONCLUSIONS

This study indicates the potential of combining (immuno)therapy with HDACi to enhance both T cell-driven and NKcell-driven immune responses in patients with HR-NBL.

From mesenchymal niches to engineered in vitro model systems: Exploring and exploiting biomechanical regulation of vertebrate hedgehog signalling

Tissue patterning is the result of complex interactions between transcriptional programs and various mechanical cues that modulate cell behaviour and drive morphogenesis. Vertebrate Hedgehog signalling plays key roles in embryogenesis and adult tissue homeostasis, and is central to skeletal development and the osteogenic differentiation of mesenchymal stem cells. The expression of several components of the Hedgehog signalling pathway have been reported to be mechanically regulated in mesodermal tissue patterning and osteogenic differentiation in response to external stimulation. Since a number of bone developmental defects and skeletal diseases, such as osteoporosis, are directly linked to aberrant Hedgehog signalling, a better knowledge of the regulation of Hedgehog signalling in the mechanosensitive bone marrow-residing mesenchymal stromal cells will present novel avenues for modelling these diseases and uncover novel opportunities for extracellular matrix-targeted therapies. In this review, we present a brief overview of the key molecular players involved in Hedgehog signalling and the basic concepts of mechanobiology, with a focus on bone development and regeneration. We also highlight the correlation between the activation of the Hedgehog signalling pathway in response to mechanical cues and osteogenesis in bone marrow-derived mesenchymal stromal cells. Finally, we propose different tissue engineering strategies to apply the expanding knowledge of 3D material-cell interactions in the modulation of Hedgehog signalling in vitro for fundamental and translational research applications.

TGFβ-derived immune modulatory vaccine: targeting the immunosuppressive and fibrotic tumor microenvironment in a murine model of pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is associated with very poor survival, making it the third and fourth leading cause of all cancer-related deaths in the USA and European Union, respectively. The tumor microenvironment (TME) in PDAC is highly immunosuppressive and desmoplastic, which could explain the limited therapeutic effect of immunotherapy in PDAC. One of the key molecules that contributes to immunosuppression and fibrosis is transforming growth factor-β (TGFβ). The aim of this study was to target the immunosuppressive and fibrotic TME in PDAC using a novel immune modulatory vaccine with TGFβ-derived peptides in a murine model of pancreatic cancer.

METHODS

C57BL/6 mice were subcutaneously inoculated with Pan02 PDAC cells. Mice were treated with TGFβ1-derived peptides (major histocompatibility complex (MHC)-I and MHC-II-restricted) adjuvanted with Montanide ISA 51VG. The presence of treatment-induced TGFβ-specific T cells was assessed by ELISpot (enzyme-linked immunospot). Changes in the immune infiltration and gene expression profile in tumor samples were characterized by flow cytometry, reverse transcription-quantitative PCR (RT-qPCR), and bulk RNA sequencing.

RESULTS

Treatment with immunogenic TGFβ-derived peptides was safe and controlled tumor growth in Pan02 tumor-bearing mice. Enlargement of tumor-draining lymph nodes in vaccinated mice positively correlated to the control of tumor growth. Analysis of immune infiltration and gene expression in Pan02 tumors revealed that TGFβ-derived peptide vaccine increased the infiltration of CD8⁺ T cells and the intratumoral M1/M2 macrophage ratio, it increased the expression of genes involved in immune activation and immune response to tumors, and it reduced the expression of myofibroblast-like cancer-associated fibroblast (CAF)-related genes and genes encoding fibroblast-derived collagens. Finally, we confirmed that TGFβ-derived peptide vaccine actively modulated the TME, as the ability of T cells to proliferate was restored when exposed to tumor-conditioned media from vaccinated mice compared with media from untreated mice.

CONCLUSION

This study demonstrates the antitumor activity of TGFβ-derived multipeptide vaccination in a murine tumor model of PDAC. The data suggest that the vaccine targets immunosuppression and fibrosis in the TME by polarizing the cellular composition towards a more pro-inflammatory phenotype. Our findings support the feasibility and potential of TGFβ-derived peptide vaccination as a novel immunotherapeutic approach to target immunosuppression in the TME.

NFATc1 signaling drives chronic ER stress responses to promote NAFLD progression

OBJECTIVES

Non-alcoholic fatty liver disease (NAFLD) can persist in the stage of simple hepatic steatosis or progress to steatohepatitis (NASH) with an increased risk for cirrhosis and cancer. We examined the mechanisms controlling the progression to severe NASH in order to develop future treatment strategies for this disease.

DESIGN

NFATc1 activation and regulation was examined in livers from patients with NAFLD, cultured and primary hepatocytes and in transgenic mice with differential hepatocyte-specific expression of the transcription factor (Alb-cre, NFATc1^c.a . and NFATc1^Δ/Δ ). Animals were fed with high-fat western diet (WD) alone or in combination with tauroursodeoxycholic acid (TUDCA), a candidate drug for NAFLD treatment. NFATc1-dependent ER stress-responses, NLRP3 inflammasome activation and disease progression were assessed both in vitro and in vivo.

RESULTS

NFATc1 expression was weak in healthy livers but strongly induced in advanced NAFLD stages, where it correlates with liver enzyme values as well as hepatic inflammation and fibrosis. Moreover, high-fat WD increased NFATc1 expression, nuclear localisation and activation to promote NAFLD progression, whereas hepatocyte-specific depletion of the transcription factor can prevent mice from disease acceleration. Mechanistically, NFATc1 drives liver cell damage and inflammation through ER stress sensing and activation of the PERK-CHOP unfolded protein response (UPR). Finally, NFATc1-induced disease progression towards NASH can be blocked by TUDCA administration.

CONCLUSION

NFATc1 stimulates NAFLD progression through chronic ER stress sensing and subsequent activation of terminal UPR signalling in hepatocytes. Interfering with ER stress-responses, for example, by TUDCA, protects fatty livers from progression towards manifest NASH.

Ionised hypocalcaemia in emergency and acute medicine

Acute hypocalcaemia can be life-threatening and must be diagnosed promptly. The gold-standard investigation is ionised calcium, which is measured on most blood gas analysers. Total calcium measurements are inaccurate in severe depletion even if 'corrected' or 'adjusted' for albumin. We present an illustrative case of a woman in her 30s with symptomatic hypocalcaemia and a very low ionised calcium on VBG analysis. Emergency calcium replacement was delayed due to a falsely reassuring corrected calcium result. Our discussion includes a systematic literature review on the use of ionised calcium in emergency and acute medical settings. We suggest cognitive biases that may explain clinical over-reliance on corrected calcium, and call for the inclusion of ionised calcium values in major treatment guidelines for acute hypocalcaemia.

Perceived needs and health-related quality of life in women with breast cancer undergoing chemotherapy: a cross-sectional study

OBJECTIVES

Women with breast cancer have different needs that are various in perceived importance and satisfaction. This study aimed to examine the relationship among perceived needs satisfaction, perceived needs importance with health-related quality of life (HRQoL) in women with breast cancer and determine the intermediary role of perceived needs importance in the relationship between perceived needs satisfaction and HRQoL.

DESIGN

Cross-sectional design.

SETTING

Two tertiary level hospitals in Shaanxi Province, China.

PARTICIPANTS

Women newly diagnosed with breast cancer were recruited.

OUTCOME MEASURES

The Needs Self-Rating Questionnaire for Breast Cancer and the Medical Outcomes Study 36-item Short-Form Health Survey V. 2.0 were used for data collection regarding perceived needs satisfaction, perceived needs importance and HRQoL.

RESULTS

A total of 359 valid questionnaires were collected. The perceived needs importance was negatively associated with physical component summary (PCS) (b=-0.067, p=0.024) and mental component summary (MCS) (b=-0.185, p&lt;0.001). On the contrary, perceived needs satisfaction was positively associated with PCS (c'=0.005, p=0.843), although not statistically significant. Perceived needs satisfaction was positively associated with MCS (c'=0.194, p&lt;0.001) and perceived needs importance (a=0.458, p&lt;0.001). Furthermore, the perceived needs importance suppressed the relationship between perceived needs satisfaction and PCS (a*b=-0.031; 95% CI -0.058 to -0.004) and the relationship between perceived needs satisfaction and MCS (a*b=-0.085; 95% CI -0.138 to -0.043).

CONCLUSION

For women with breast cancer, higher perceived needs satisfaction is associated with higher HRQoL. However, higher perceived needs importance would be conversely associated with lower HRQoL by suppressing the positive association of perceived needs satisfaction with HRQoL. Healthcare providers should pay more attention to those who have high perceived needs importance but low perceived needs satisfaction and fulfil the important needs.

Alleviation of renal injury in rabbits by allisartan

The objective of this study was to determine the relationship between renal injury and inflammatory response induced by high-fat diet in rabbits and the interventional effect of allisartan. Fifteen 6-week-old healthy male rabbits were randomly divided into three groups: normal control (NC) group, high-lipid diet (HLD) group, high-lipid diet and allisartan (HLD+ALST) group. After allisartan treatment for 12 weeks, changes in total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), serum creatinine (Scr) and blood urea nitrogen (BUN) were measured enzymatically in the three groups. The left side of the kidney tissue was kept for paraffin section, and HE staining, periodic acid-Schiff (PAS) staining and Masson staining were used to observe the renal pathologic changes. TC, TG, LDL-C, Scr and BUN levels were all higher and HDL-C levels were lower in the HLD group compared with the NC group. Compared with the HLD group, Scr and BUN levels were significantly decreased in the HLD+ALST group. The results of HE staining showed that allisartan improved the changes of renal tissue morphology in rabbits on high-fat diet, reduced glomerular mesangial cell proliferation and improved glomerulosclerosis; PAS staining showed that glomerular glycogen deposition was reduced and glomerular red staining was significantly lighter; Masson staining showed that renal tubular blue-stained collagen fibers were reduced. In conclusion, hyperlipidemia can lead to aberrant expression of multiple cellular proteins and kidney tissue morphological damage in rabbits. On the other hand, allisartan attenuated renal injury and the mechanism may be related to the downregulation of the inflammatory response.

Radiofrequency-assisted transection of the pancreas versus stapler in distal pancreatectomy: study protocol for a multicentric randomised clinical trial (TRANSPAIRE)

INTRODUCTION

To date, no pancreatic stump closure technique has been shown to be superior to any other in distal pancreatectomy. Although several studies have shown a trend towards better results in transection using a radiofrequency device (radiofrequency-assisted transection (RFT)), no randomised trial for this purpose has been performed to date. Therefore, we designed a randomised clinical trial, with the hypothesis that this technique used in distal pancreatectomies is superior in reducing clinically relevant postoperative pancreatic fistula (CR-POPF) than mechanical closures.

METHODS AND ANALYSIS

TRANSPAIRE is a multicentre randomised controlled trial conducted in seven Spanish pancreatic centres that includes 112 patients undergoing elective distal pancreatectomy for any indication who will be randomly assigned to RFT or classic stapler transections (control group) in a ratio of 1:1. The primary outcome is the CR-POPF percentage. Sample size is calculated with the following assumptions: 5% one-sided significance level (α), 80% power (1-β), expected POPF in control group of 32%, expected POPF in RFT group of 10% and a clinically relevant difference of 22%. Secondary outcomes include postoperative results, complications, radiological evaluation of the pancreatic stump, metabolomic profile of postoperative peritoneal fluid, survival and quality of life. Follow-ups will be carried out in the external consultation at 1, 6 and 12 months postoperatively.

ETHICS AND DISSEMINATION

TRANSPAIRE has been approved by the CEIM-PSMAR Ethics Committee. This project is being carried out in accordance with national and international guidelines, the basic principles of protection of human rights and dignity established in the Declaration of Helsinki (64th General Assembly, Fortaleza, Brazil, October 2013), and in accordance with regulations in studies with biological samples, Law 14/2007 on Biomedical Research will be followed. We have defined a dissemination strategy, whose main objective is the participation of stakeholders and the transfer of knowledge to support the exploitation of activities.

REGISTRATION DETAILS

ClinicalTrials.gov Registry (NCT04402346).

The dinosaurian femoral head experienced a morphogenetic shift from torsion to growth along the avian stem

Significant evolutionary shifts in locomotor behaviour often involve comparatively subtle anatomical transitions. For dinosaurian and avian evolution, medial overhang of the proximal femur has been central to discussions. However, there is an apparent conflict with regard to the evolutionary origin of the dinosaurian femoral head, with neontological and palaeontological data suggesting seemingly incongruent hypotheses. To reconcile this, we reconstructed the evolutionary history of morphogenesis of the proximal end of the femur from early archosaurs to crown birds. Embryological comparison of living archosaurs (crocodylians and birds) suggests the acquisition of the greater overhang of the femoral head in dinosaurs results from additional growth of the proximal end in the medial-ward direction. On the other hand, the fossil record suggests that this overhang was acquired by torsion of the proximal end, which projected in a more rostral direction ancestrally. We reconcile this apparent conflict by inferring that the medial overhang of the dinosaur femoral head was initially acquired by torsion, which was then superseded by mediad growth. Details of anatomical shifts in fossil forms support this hypothesis, and their biomechanical implications are congruent with the general consensus regarding broader morpho-functional evolution on the avian stem.

Arginase-2-specific cytotoxic T cells specifically recognize functional regulatory T cells

Background

High expression of the metabolic enzyme arginase-2 (ARG2) by cancer cells, regulatory immune cells, or cells of the tumor stroma can reduce the availability of arginine (L-Arg) in the tumor microenvironment (TME). Depletion of L-Arg has detrimental consequences for T cells and leads to T-cell dysfunction and suppression of anticancer immune responses. Previous work from our group has demonstrated the presence of proinflammatory ARG2-specific CD4 T cells that inhibited tumor growth in murine models on activation with ARG2-derived peptides. In this study, we investigated the natural occurrence of ARG2-specific CD8 T cells in both healthy donors (HDs) and patients with cancer, along with their immunomodulatory capabilities in the context of the TME.

Materials and methods

A library of 15 major histocompatibility complex (MHC) class I-restricted ARG2-derived peptides were screened in HD peripheral blood mononuclear cells using interferon gamma (IFN-γ) ELISPOT. ARG2-specific CD8 T-cell responses were identified using intracellular cytokine staining and ARG2-specific CD8 T-cell cultures were established by enrichment and rapid expansion following in vitro peptide stimulation. The reactivity of the cultures toward ARG2-expressing cells, including cancer cell lines and activated regulatory T cells (Tregs), was assessed using IFN-γ ELISPOT and a chromium release assay. The Treg signature was validated based on proliferation suppression assays, flow cytometry and quantitative reverse transcription PCR (RT-qPCR). In addition, vaccinations with ARG2-derived epitopes were performed in the murine Pan02 tumor model, and induction of ARG2-specific T-cell responses was evaluated with IFN-γ ELISPOT. RNAseq and subsequent GO-term and ImmuCC analysis was performed on the tumor tissue.

Results

We describe the existence of ARG2-specific CD8⁺ T cells and demonstrate these CD8⁺ T-cell responses in both HDs and patients with cancer. ARG2-specific T cells recognize and react to an ARG2-derived peptide presented in the context of HLA-B8 and exert their cytotoxic function against cancer cells with endogenous ARG2 expression. We demonstrate that ARG2-specific T cells can specifically recognize and react to activated Tregs with high ARG2 expression. Finally, we observe tumor growth suppression and antitumorigenic immunomodulation following ARG2 vaccination in an in vivo setting.

Conclusion

These findings highlight the ability of ARG2-specific T cells to modulate the immunosuppressive TME and suggest that ARG2-based immunomodulatory vaccines may be an interesting option for cancer immunotherapy.

Effectiveness of early spectacle intervention on visual outcomes in babies at risk of cerebral visual impairment: a parallel group, open-label, randomised clinical feasibility trial protocol

INTRODUCTION

Hypoaccommodation is common in children born prematurely and those with hypoxic ischaemic encephalopathy (HIE), with the potential to affect wider learning. These children are also at risk of longer-term cerebral visual impairment. It is also well recognised that early intervention for childhood visual pathology is essential, because neuroplasticity progressively diminishes during early life. This study aims to establish the feasibility and acceptability of conducting a randomised controlled trial to test the effectiveness of early near vision correction with spectacles in infancy, for babies, at risk of visual dysfunction.

METHODS AND ANALYSIS

This is a parallel group, open-label, randomised controlled (feasibility) study to assess visual outcomes in children with perinatal brain injury when prescribed near vision spectacles compared with the current standard care-waiting until a problem is detected. The study hypothesis is that accommodation, and possibly other aspects of vision, may be improved by intervening earlier with near vision glasses. Eligible infants (n=75, with either HIE or <29 weeks preterm) will be recruited and randomised to one of three arms, group A (no spectacles) and two intervention groups: B1 or B2. Infants in both intervention groups will be offered glasses with +3.00 DS added to the full cycloplegic refraction and prescribed for full time wear. Group B1 will get their first visit assessment and intervention at 8 weeks corrected gestational age (B1) and B2 at 16 weeks corrected gestational age. All infants will receive a complete visual and neurodevelopmental assessment at baseline and a follow-up visit at 3 and 6 months after the first visit.

ETHICS AND DISSEMINATION

The South-Central Oxford C Research Ethics Committee has approved the study. Members of the PPI committee will give advice on dissemination of results through peer-reviewed publications, conferences and societies.

TRIAL REGISTRATION NUMBER

ISRCTN14646770, NCT05048550, NIHR ref: PB-PG-0418-20006.

Evaluating the impact of a sleep health education and a personalised smartphone application on sleep, productivity and healthcare utilisation among employees: results of a randomised clinical trial

OBJECTIVES

We evaluated an online Sleep Health and Wellness (SHAW) programme paired with dayzz, a personalised sleep training programme deployed via smartphone application (dayzz app) that promotes healthy sleep and treatment for sleep disorders, among employees at a large healthcare organisation.

DESIGN

Open-label, randomised, parallel-group controlled trial.

SETTING

A healthcare employer in the USA.

PARTICIPANTS

1355 daytime workers.

INTERVENTION

Participants were randomised to intervention (n=794) or control (n=561) on consent. Intervention participants received the SHAW educational programme at baseline plus access to the personalised dayzz app for up to 9 months. The control condition received the intervention at month 10.

PRIMARY AND SECONDARY OUTCOME MEASURES

Our primary outcome measures were sleep-related behavioural changes (eg, consistent sleep schedule); sleep behaviour tracked on an electronic sleep diary and sleep quality. Our secondary outcome measures included employee absenteeism, performance and productivity; stress, mood, alertness and energy; and adverse health and safety outcomes (eg, accidents).

RESULTS

At follow-up, employees in the intervention condition were more likely to report increased sleep duration on work (7.20 vs 6.99, p=0.01) and on free (8.26 vs 8.04, p=0.03) nights. At follow-up, the prevalence of poor sleep quality was lower in the intervention (n=160 of 321, 50%) compared with control (n=184 of 327, 56%) (p=0.04). The mean total dollars lost per person per month due to reduced workplace performance (presenteeism) was less in the intervention condition (US$1090 vs US$1321, p=0.001). Employees in the intervention reported fewer mental health visits (RR 0.72, 95% CI 0.56 to 0.94, p=0.01) and lower healthcare utilisation over the study interval (RR 0.81, 95% CI 0.67 to 0.98, p=0.03). We did not observe differences in stress (4.7 (95% CI 4.6 to 4.8) vs 4.7 (95% CI 4.6 to 4.8)), mood (4.5 (95% CI 4.4 to 4.6) vs 4.6 (95% CI 4.5 to 4.7)), alertness (4.9 (95% CI 4.8 to 5.0) vs 5.0 (95% CI 4.9 to 5.1)) or adverse health and safety outcomes (motor vehicle crashes: OR 0.82 (95% CI 0.34 to 1.9); near-miss crashes: OR=0.89 (95% CI 0.5 to 1.5) and injuries: 0.9 (95% CI 0.6 to 1.3)); energy was higher at follow-up in the intervention group (4.3 vs 4.5; p=0.03).

CONCLUSIONS

Results from this trial demonstrate that a SHAW programme followed by access to the digital dayzz app can be beneficial to both the employee and employer.

TRIAL REGISTRATION NUMBER

NCT04224285.

The role of single-cell genomics in human genetics

Single-cell sequencing is a powerful approach that can detect genetic alterations and their phenotypic consequences in the context of human development, with cellular resolution. Humans start out as single-cell zygotes and undergo fission and differentiation to develop into multicellular organisms. Before fertilisation and during development, the cellular genome acquires hundreds of mutations that propagate down the cell lineage. Whether germline or somatic in nature, some of these mutations may have significant genotypic impact and lead to diseased cellular phenotypes, either systemically or confined to a tissue. Single-cell sequencing enables the detection and monitoring of the genotype and the consequent molecular phenotypes at a cellular resolution. It offers powerful tools to compare the cellular lineage between 'normal' and 'diseased' conditions and to establish genotype-phenotype relationships. By preserving cellular heterogeneity, single-cell sequencing, unlike bulk-sequencing, allows the detection of even small, diseased subpopulations of cells within an otherwise normal tissue. Indeed, the characterisation of biopsies with cellular resolution can provide a mechanistic view of the disease. While single-cell approaches are currently used mainly in basic research, it can be expected that applications of these technologies in the clinic may aid the detection, diagnosis and eventually the treatment of rare genetic diseases as well as cancer. This review article provides an overview of the single-cell sequencing technologies in the context of human genetics, with an aim to empower clinicians to understand and interpret the single-cell sequencing data and analyses. We discuss the state-of-the-art experimental and analytical workflows and highlight current challenges/limitations. Notably, we focus on two prospective applications of the technology in human genetics, namely the annotation of the non-coding genome using single-cell functional genomics and the use of single-cell sequencing data for in silico variant prioritisation.

Label-free metabolic imaging for sensitive and robust monitoring of anti-CD47 immunotherapy response in triple-negative breast cancer

Background

Immunotherapy is revolutionizing cancer treatment from conventional radiotherapies and chemotherapies to immune checkpoint inhibitors which use patients’ immune system to recognize and attack cancer cells. Despite the huge clinical success and vigorous development of immunotherapies, there is a significant unmet need for a robust tool to identify responders to specific immunotherapy. Early and accurate monitoring of immunotherapy response is indispensable for personalized treatment and effective drug development.

Methods

We established a label-free metabolic intravital imaging (LMII) technique to detect two-photon excited autofluorescence signals from two coenzymes, NAD(P)H (reduced nicotinamide adenine dinucleotide (phosphate) hydrogen) and FAD (flavin adenine dinucleotide) as robust imaging markers to monitor metabolic responses to immunotherapy. Murine models of triple-negative breast cancer (TNBC) were established and tested with different therapeutic regimens including anti-cluster of differentiation 47 (CD47) immunotherapy to monitor time-course treatment responses using the developed metabolic imaging technique.

Results

We first imaged the mechanisms of the CD47-signal regulatory protein alpha pathway in vivo, which unravels macrophage-mediated antibody-dependent cellular phagocytosis and illustrates the metabolism of TNBC cells and macrophages. We further visualized the autofluorescence of NAD(P)H and FAD and found a significant increase during tumor growth. Following anti-CD47 immunotherapy, the imaging signal was dramatically decreased demonstrating the sensitive monitoring capability of NAD(P)H and FAD imaging for therapeutic response. NAD(P)H and FAD intravital imaging also showed a marked decrease after chemotherapy and radiotherapy. A comparative study with conventional whole-body bioluminescence and fluorescent glucose imaging demonstrated superior sensitivity of metabolic imaging. Flow cytometry validated metabolic imaging results. In vivo immunofluorescent staining revealed the targeting ability of NAD(P)H imaging mainly for tumor cells and a small portion of immune-active cells and that of FAD imaging mainly for immunosuppressive cells such as M2-like tumor-associated macrophages.

Conclusions

Collectively, this study showcases the potential of the LMII technique as a powerful tool to visualize dynamic changes of heterogeneous cell metabolism of cancer cells and immune infiltrates in response to immunotherapy thus providing sensitive and complete monitoring. Leveraged on ability to differentiate cancer cells and immunosuppressive macrophages, the presented imaging approach provides particularly useful imaging biomarkers for emerged innate immune checkpoint inhibitors such as anti-CD47 therapy.

Poststroke motor, cognitive and speech rehabilitation with brain-computer interface: a perspective review

Brain-computer interface (BCI) technology translates brain activity into meaningful commands to establish a direct connection between the brain and the external world. Neuroscientific research in the past two decades has indicated a tremendous potential of BCI systems for the rehabilitation of patients suffering from poststroke impairments. By promoting the neuronal recovery of the damaged brain networks, BCI systems have achieved promising results for the recovery of poststroke motor, cognitive, and language impairments. Also, several assistive BCI systems that provide alternative means of communication and control to severely paralysed patients have been proposed to enhance patients' quality of life. In this article, we present a perspective review of the recent advances and challenges in the BCI systems used in the poststroke rehabilitation of motor, cognitive, and communication impairments.

Effect of beetroot or beetroot plus vitamin C supplementation on cardiovascular function in patients with coronary artery disease: protocol for a double-blind, placebo-controlled, randomised trial

INTRODUCTION

Coronary artery disease (CAD), classified into the atherosclerosis category, is a prevalent cardiovascular disease worldwide that is associated with serious comorbidities and death. The purpose of this study was to evaluate the effect of beetroot/beetroot plus vitamin C on cardiovascular health status and function in patients with CAD.

METHOD AND ANALYSIS

A randomised, placebo-controlled, double-blind clinical trial to recruit 90 patients with CAD at the cardiac outpatient clinic and Imam Reza Hospital, Mashhad, Iran. Participants will be divided into three groups: (1) Those who receive 500 mg three times a day of beetroot capsules, (2) Those who receive 500 mg three times a day of beetroot plus vitamin C capsules, and (3) Those who receive placebo capsules three times a day for 4 weeks. Pulse wave velocity, Augmentation Index, heart rate, volume of oxygen (VO₂) max/VO₂ peak, peak heart rate, blood pressure, interleukin 6 (IL-6), high sensitivity C reactive protein, intercellular adhesion molecule, vascular cell adhesion molecule, lipid profile and anthropometry will be measured at the beginning and end of the intervention.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee of Mashhad University of Medical Sciences (IR.MUMS.MEDICAL.REC.1399.717). All participants will be asked to complete the consent form at the beginning of the study. The results will be actively disseminated through peer-reviewed journals and conference presentations.

TRIAL REGISTRATION NUMBER

Iranian Registry of Clinical Trials, IRCT20210217050393N1 (registered 16 May 2021).

A single-component luminescent biosensor for the SARS-CoV-2 spike protein

Many existing protein detection strategies depend on highly functionalized antibody reagents. A simpler and easier to produce class of detection reagent is highly desirable. We designed a single-component, recombinant, luminescent biosensor that can be expressed in laboratory strains of E. coli and S. cerevisiae . This biosensor is deployed in multiple homogenous and immobilized assay formats to detect recombinant SARS-CoV-2 spike antigen and cultured virus. The chemiluminescent signal generated facilitates detection by an un-augmented cell phone camera. B inding A ctivated T andem split-enzyme (BAT) biosensors may serve as a useful template for diagnostics and reagents that detect SARS-CoV-2 antigens and other proteins of interest.

Human Spindle Variability

In humans, sleep spindles are 10- to 16-Hz oscillations lasting approximately 0.5-2 s. Spindles, along with cortical slow oscillations, may facilitate memory consolidation by enabling synaptic plasticity. Early recordings of spindles at the scalp found anterior channels had overall slower frequency than central-posterior channels. This robust, topographical finding led to dichotomizing spindles as "slow" versus "fast," modeled as two distinct spindle generators in frontal versus posterior cortex. Using a large dataset of intracranial stereoelectroencephalographic (sEEG) recordings from 20 patients (13 female, 7 male) and 365 bipolar recordings, we show that the difference in spindle frequency between frontal and parietal channels is comparable to the variability in spindle frequency within the course of individual spindles, across different spindles recorded by a given site, and across sites within a given region. Thus, fast and slow spindles only capture average differences that obscure a much larger underlying overlap in frequency. Furthermore, differences in mean frequency are only one of several ways that spindles differ. For example, compared with parietal, frontal spindles are smaller, tend to occur after parietal when both are engaged, and show a larger decrease in frequency within-spindles. However, frontal and parietal spindles are similar in being longer, less variable, and more widespread than occipital, temporal, and Rolandic spindles. These characteristics are accentuated in spindles which are highly phase-locked to posterior hippocampal spindles. We propose that rather than a strict parietal-fast/frontal-slow dichotomy, spindles differ continuously and quasi-independently in multiple dimensions, with variability due about equally to within-spindle, within-region, and between-region factors.SIGNIFICANCE STATEMENT Sleep spindles are 10- to 16-Hz neural oscillations generated by cortico-thalamic circuits that promote memory consolidation. Spindles are often dichotomized into slow-anterior and fast-posterior categories for cognitive and clinical studies. Here, we show that the anterior-posterior difference in spindle frequency is comparable to that observed between different cycles of individual spindles, between spindles from a given site, or from different sites within a region. Further, we show that spindles vary on other dimensions such as duration, amplitude, spread, primacy and consistency, and that these multiple dimensions vary continuously and largely independently across cortical regions. These findings suggest that multiple continuous variables rather than a strict frequency dichotomy may be more useful biomarkers for memory consolidation or psychiatric disorders.

Pancreatic β-Cell Development and Regeneration

The pancreatic β-cells are essential for regulating glucose homeostasis through the coordinated release of the insulin hormone. Dysfunction of the highly specialized β-cells results in diabetes mellitus, a growing global health epidemic. In this review, we describe the development and function of β-cells the emerging concept of heterogeneity within insulin-producing cells, and the potential of other cell types to assume β-cell functionality via transdifferentiation. We also discuss emerging routes to design cells with minimal β-cell properties and human stem cell differentiation efforts that carry the promise to restore normoglycemia in patients suffering from diabetes.

Local mechanical stimuli correlate with tissue growth in axolotl salamander joint morphogenesis

Movement-induced forces are critical to correct joint formation, but it is unclear how cells sense and respond to these mechanical cues. To study the role of mechanical stimuli in the shaping of the joint, we combined experiments on regenerating axolotl (Ambystoma mexicanum) forelimbs with a poroelastic model of bone rudiment growth. Animals either regrew forelimbs normally (control) or were injected with a transient receptor potential vanilloid 4 (TRPV4) agonist during joint morphogenesis. We quantified growth and shape in regrown humeri from whole-mount light sheet fluorescence images of the regenerated limbs. Results revealed significant differences in morphology and cell proliferation between groups, indicating that TRPV4 desensitization has an effect on joint shape. To link TRPV4 desensitization with impaired mechanosensitivity, we developed a finite element model of a regenerating humerus. Local tissue growth was the sum of a biological contribution proportional to chondrocyte density, which was constant, and a mechanical contribution proportional to fluid pressure. Computational predictions of growth agreed with experimental outcomes of joint shape, suggesting that interstitial pressure driven from cyclic mechanical stimuli promotes local tissue growth. Predictive computational models informed by experimental findings allow us to explore potential physical mechanisms involved in tissue growth to advance our understanding of the mechanobiology of joint morphogenesis.