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Abstract
The Neurofibromatosis Type 1 (NF1) RASopathy is associated with persistent fibrotic nonunions (pseudarthrosis) in human and mouse skeletal tissue. Here, we first performed spatial transcriptomics to define the molecular signatures across normal endochondral healing following fracture in mice. Within the control fracture callus, we observed spatially restricted activation of morphogenetic pathways, such as TGF-β, WNT, and BMP. To investigate the molecular mechanisms contributing to Nf1-deficient delayed fracture healing, we performed spatial transcriptomic analysis on a Postn-cre;Nf1flox/- (Nf1Postn) fracture callus. Transcriptional analyses, subsequently confirmed through p-SMAD1/5/8 immunohistochemistry, demonstrated a lack of BMP pathway induction in Nf1Postn mice. To further inform the human disease, we performed spatial transcriptomic analysis of fracture pseudarthrosis tissue from a NF1 patient. Analyses detected increased MAPK signaling at the fibrocartilaginous-osseus junction. Similar to the Nf1Postn fracture, BMP pathway activation was absent within the pseudarthrosis tissue. Our results demonstrate the feasibility to delineate the molecular and tissue-specific heterogeneity inherent in complex regenerative processes, such as fracture healing, and to reconstruct phase transitions representing endochondral bone formation in vivo. Furthermore, our results provide in situ molecular evidence of impaired BMP signaling underlying NF1 pseudarthrosis, potentially informing the clinical relevance of off-label BMP2 as a therapeutic intervention.
Authors
Jonathan J. Rios, Conan Juan, John M. Shelton, Nandina Paria, Ila Oxendine, Meghan Wassell, Yared H. Kidane, Reuel Cornelia, Elise C. Jeffery, David A. Podeszwa, Simon J. Conway, Carol A. Wise, Robert J. Tower
Abstract
Childhood obesity and its adverse health consequences have risen worldwide, with low socioeconomic status increasing the risk in high-income countries like the US. Understanding the interplay between childhood obesity, cognition, socioeconomic factors, and the brain is crucial for prevention and treatment. Using data from the ABCD study, we investigated how body mass index (BMI) relates to brain structural and functional connectivity metrics. Obese/overweight children (n = 2,356) were more likely to live in poverty and exhibited lower cognitive performance compared to normal weight children (n = 4,754). Higher BMI was associated with multiple brain measures that were strongest for lower longitudinal diffusivity in corpus callosum, increased activity in cerebellum, insula, and somatomotor cortex, and decreased functional connectivity in multimodal brain areas, with effects more pronounced among children from low-income families. Notably, nearly 80% of the association of low income and 70% of the association of impaired cognition on BMI were mediated by higher brain activity in somatomotor areas. Increased resting activity in somatomotor areas and decreased structural and functional connectivity likely contribute to the higher risk of overweight/obesity among children from low-income families. Supporting low-income families and implementing educational interventions to improve cognition may promote healthy brain function and reduce the risk of obesity.
Authors
Dardo Tomasi, Nora D. Volkow
Abstract
We evaluated the safety and viral rebound, after analytical treatment interruption (ATI), of vedolizumab and ART in recent HIV-1 infection. We used this model to analyze the impact of α4β7 on the HIV-1 reservoir size. Participants started ART with monthly Vedolizumab infusions and ATI was performed at week 24. Biopsies were obtained from ileum and caecum at baseline and week 24. Vedolizumab levels, HIV-1 reservoir, flow cytometry and cell-sorting and antibody competition experiments were assayed. Vedolizumab was safe and well-tolerated. No participant achieved undetectable viremia off ART 24 weeks after ATI. Only a modest effect on the time to achieve >1000 HIV-RNA copies/mL and the proportion of participants off ART was observed, being higher compared to historical controls. Just before ATI, α4β7 expression was associated with HIV-1 DNA and RNA in peripheral blood and with PD1 and TIGIT levels. Importantly, a complete blocking of α4β7 was observed on peripheral CD4+ T-cells but not in gut (ileum and caecum), where α4β7 blockade and vedolizumab levels were inversely associated with HIV-1 DNA. Our findings support α4β7 as an important determinant in HIV-1 reservoir size, suggesting the complete α4β7 blockade in tissue as a promising tool for HIV-cure combination strategies.
Authors
Maria Reyes Jimenez-Leon, Carmen Gasca-Capote, Cristina Roca-Oporto, Nuria Espinosa, Salvador Sobrino, Maria Fontillon-Alberdi, Ce Gao, Isabelle Roseto, Gregory Gladkov, Inmaculada Rivas-Jeremias, Karin Neukam, Jose German Sanchez-Hernandez, Raul Rigo-Bonnin, Antonio J. Cervera-Barajas, Rosario Mesones, Federico García, Ana Isabel Alvarez-Rios, Sara Bachiller, Joana Vitalle, Alberto Perez-Gomez, María Inés Camacho-Sojo, Isabel Gallego, Christian Brander, Ian McGowan, Beatriz Mothe, Pompeyo Viciana, Xu Yu, Mathias Lichterfeld, Luis F. Lopez-Cortes, Ezequiel Ruiz-Mateos
Abstract
Solid organ transplantation remains the life-saving treatment for end-stage organ failure, but chronic rejection remains a major obstacle to long-term allograft outcomes and has not improved substantially. Tertiary lymphoid organs (TLO) are ectopic lymphoid structures that form under conditions of chronic inflammation, and evidence from human transplantation suggests that TLO regularly form in allografts undergoing chronic rejection. In this study, we utilized a mouse renal transplantation model and manipulation of the lymphotoxin alpha (LTα) – lymphotoxin beta receptor (LTβR) pathway, which is essential for TLO formation, to define the role of TLO in transplantation. We showed that intragraft TLO are sufficient to activate the alloimmune response and mediate graft rejection in a model where the only lymphoid organs are TLO in the allograft. When transplanted to recipients with a normal set of secondary lymphoid organs, the presence of graft TLO or LTα overexpression accelerated rejection. If the LTβR pathway was disrupted in the donor graft, TLO formation was abrogated, and graft survival prolonged. Intravital microscopy of renal TLO demonstrated that local T and B cell activation in TLOs is similar to that observed in secondary lymphoid organs. In summary, we demonstrated that immune activation in TLO contributes to local immune responses, leading to earlier allograft failure. TLO and the LTαβ-LTβR pathway are therefore prime targets to limit local immune responses and prevent allograft rejection. These findings are applicable to other diseases such as autoimmunity or tumors, where either limiting or boosting local immune responses is beneficial and improves disease outcomes.
Authors
Gang Zhang, Neda Feizi, Daqiang Zhao, Latha Halesha, Amanda L. Williams, Parmjeet S. Randhawa, Khodor I. Abou-Daya, Martin H. Oberbarnscheidt
Abstract
Upon infection, naïve CD8+ T cells differentiate into cytotoxic effector cells to eliminate the pathogen-infected cells. Although many mechanisms underlying this process have been demonstrated, the regulatory role of chromatin remodel system in this process remains largely unknown. Here we showed that BRD7, a component of the polybromo-associated BRG1-associated factor complex (PBAF), was required for naïve CD8+ T cells to differentiate into functional short-lived effector cells (SLECs) in response to acute infections caused by influenza virus or lymphocytic choriomeningitis virus (LCMV). BRD7-deficiency in CD8+ T cells resulted in profound defects in effector population and functions, thereby impairing viral clearance and host recovery. Further mechanical studies indicated that the expression of BRD7 significantly turned to high from naïve CD8+ T cells to effector cells, bridged BRG1 and PBRM1 to the core module of PBAF complex, consequently facilitating the assembly of PBAF complex rather than BAF complex in the effector cells. The PBAF complex changed the chromatin accessibility at the loci of Tbx21 gene and up-regulated its expression, leading to the maturation of effector T cells. Our research confirms BRD7 and the PBAF complex are key in CD8+ T cell development and present a significant target for advancing immune therapies.
Authors
Feng Huang, Yingtong Lin, Yidan Qiao, Yaochang Yuan, Zhihan Zhong, Baohong Luo, Yating Wu, Jun Liu, Jingliang Chen, Wanying Zhang, Hui Zhang, Bingfeng Liu
Abstract
Pulmonary disorders impact 40% to 80% of individuals with obesity. Respiratory muscle dysfunction is linked to these conditions; however, its pathophysiology remains largely undefined. Mice subjected to diet-induced obesity (DIO) develop diaphragmatic weakness. Increased intra-diaphragmatic adiposity and extracellular matrix (ECM) content correlate with reductions in contractile force. Thrombospondin-1 (THBS1) is an obesity-associated matricellular protein linked with muscular damage in genetic myopathies. THBS1 induces proliferation of fibro-adipogenic progenitors (FAPs) — mesenchymal cells that differentiate into adipocytes and fibroblasts. We hypothesized that THBS1 drives FAP-mediated diaphragm remodeling and contractile dysfunction in DIO. We tested this by comparing the effects of dietary challenge on diaphragms of wild-type (WT) and Thbs1 knockout (Thbs1–/–) mice. Bulk and single-cell transcriptomics demonstrated DIO-induced stromal expansion in WT diaphragms. Diaphragm FAPs displayed upregulation of ECM and TGF β-related expression signatures and augmentation of a Thy1-expressing sub-population previously linked to type 2 diabetes. Despite similar weight gain, Thbs1–/– mice were protected from these transcriptomic changes and from obesity-induced increases in diaphragm adiposity and ECM deposition. Unlike WT controls, Thbs1–/– diaphragms maintained normal contractile force and motion after DIO challenge. These findings establish THBS1 as a necessary mediator of diaphragm stromal remodeling and contractile dysfunction in overnutrition and a potential therapeutic target in obesity-associated respiratory dysfunction.
Authors
Eric D. Buras, Moon-Sook Woo, Romil Kaul Verma, Sri Harshita Kondisetti, Carol S. Davis, Dennis R. Claflin, Kimber Converso-Baran, Daniel E. Michele, Susan V. Brooks, Tae-Hwa Chun
Abstract
Beside suppressing immune responses, regulatory T cells (Tregs) maintain tissue homeostasis and control systemic metabolism. Whether iron is involved in Treg-mediated tolerance is completely unknown. Here, we showed that the transferrin receptor CD71 was upregulated on activated Tregs infiltrating human liver cancer. Mice with a Treg-restricted CD71 deficiency spontaneously developed a scurfy-like disease, caused by impaired perinatal Treg expansion. CD71-null Tregs displayed decreased proliferation and tissue-Treg signature loss. In perinatal life, CD71 deficiency in Tregs triggered hepatic iron overload response, characterized by increased hepcidin transcription and iron accumulation in macrophages. Lower bacterial diversity, and reduction of beneficial species, were detected in the fecal microbiota of CD71 conditional knock-out neonates. Our findings indicate that CD71-mediated iron absorption is required for Treg perinatal expansion and related to systemic iron homeostasis and bacterial gut colonization. Therefore, we hypothesize that Tregs establish nutritional tolerance through competition for iron during bacterial colonization after birth.
Authors
Ilenia Pacella, Alessandra Pinzon Grimaldos, Alessandra Rossi, Gloria Tucci, Marta Zagaglioni, Elena Potenza, Valeria Pinna, Ivano Rotella, Ilenia Cammarata, Valeria Cancila, Beatrice Belmonte, Claudio Tripodo, Giuseppe Pietropaolo, Chiara Di Censo, Giuseppe Sciumè, Valerio Licursi, Giovanna Peruzzi, Ylenia Antonucci, Silvia Campello, Francesca Guerrieri, Valerio Iebba, Rita Prota, Maria Di Chiara, Gianluca Terrin, Valerio De Peppo, Gian Luca Grazi, Vincenzo Barnaba, Silvia Piconese
Abstract
Rheumatoid arthritis (RA) management lean toward achieving remission or low-disease activity. In this study, we conducted single-cell RNA sequencing (scRNAseq) of peripheral blood mononuclear cells (PBMCs) from 36 individuals (18 RA patients and 18 matched controls, accounting for age, sex, race, and ethnicity), to identify disease-relevant cell subsets and cell type-specific signatures associated with disease activity. Our analysis revealed 18 distinct PBMC subsets, including an IFITM3 overexpressing Interferon-activated (IFN-activated) monocyte subset. We observed an increase in CD4+ T effector memory cells in patients with moderate to high disease activity (DAS28-CRP ≥ 3.2), and a decrease in non-classical monocytes in patients with low disease activity or remission (DAS28-CRP < 3.2). Pseudobulk analysis by cell type identified 168 differentially expressed genes between RA and matched controls, with a downregulation of pro-inflammatory genes in the gamma-delta T cells subset, alteration of genes associated with RA predisposition in the IFN-activated subset, and non-classical monocytes. Additionally, we identified a gene signature associated with moderate-high disease activity, characterized by upregulation of pro-inflammatory genes such as TNF, JUN, EGR1, IFIT2, MAFB, G0S2, and downregulation of genes including HLA-DQB1, HLA-DRB5, TNFSF13B. Notably, cell-cell communication analysis revealed an upregulation of signaling pathways, including VISTA, in both moderate-high and remission-low disease activity contexts. Our findings provide valuable insights into the systemic cellular and molecular mechanisms underlying RA disease activity.
Authors
Marie Binvignat, Brenda Y. Miao, Camilla Wibrand, Monica M. Yang, Dmitry Rychkov, Emily Flynn, Joanne Nititham, Whitney Tamaki, Umair Khan, Alexander Carvidi, Melissa Krueger, Erene C. Niemi, Yang Sun, Gabriela K. Fragiadakis, Jérémie Sellam, Encarnita Mariotti-Ferrandiz, David Klatzmann, Andrew J. Gross, Chun Jimmie Ye, Atul J. Butte, Lindsey A. Criswell, Mary C. Nakamura, Marina Sirota
Abstract
Endoplasmic reticulum (ER) stress and proinsulin misfolding are heralded as contributing factors to β-cell dysfunction in Type 2 diabetes (T2D), yet how ER function becomes compromised is not well understood. Recent data identifies altered ER redox homeostasis as a critical mechanism that contributes to insulin granule loss in diabetes. Hyperoxidation of the ER delays proinsulin export and limits the proinsulin supply available for insulin granule formation. In this report, we identified glucose metabolism as a critical determinant in the redox homeostasis of the ER. Using multiple β-cell models, we showed that loss of mitochondrial function or inhibition of cellular metabolism elicited ER hyperoxidation and delayed ER proinsulin export. Our data further demonstrated that β-cell ER redox homeostasis was supported by the metabolic supply of reductive redox donors. We showed that limiting NADPH and thioredoxin flux delayed ER proinsulin export, whereas Txnip suppression restored ER redox and proinsulin trafficking. Taken together, we propose that β-cell ER redox homeostasis is buffered by cellular redox donor cycles, which are maintained through active glucose metabolism.
Authors
Kristen E. Rohli, Nicole J. Stubbe, Emily M. Walker, Gemma L. Pearson, Scott A. Soleimanpour, Samuel B. Stephens
Abstract
The average time-to-degree for completing a life sciences PhD in the U.S. is longer for single-degree than dual-degree trainees, supporting a perception that the PhD training of MD-PhDs is less rigorous or fulsome. To determine whether the duration and impact of graduate training is influenced by degree format, we analyzed data for the 2011–2016 graduates of three Harvard Medical School PhD programs. Linear mixed effects models were used to determine the association between degree type (MD-PhD vs. PhD) and research outcomes, including time-to-degree, time-to-thesis-defense, and publications submitted during the PhD. Although pursuing an MD-PhD was associated with a 1.5-year shorter time-to-PhD-degree, basing this calculation on the official PhD period does not account for completion of early PhD requirements, including research rotations and qualifying coursework, during the first two years of medical school. There was no association between degree format and the total number of first-authored or overall publications, although pursuing a dual degree was associated with increased impact metrics of published papers. The results highlight that despite the optically shorter PhD durations of MD-PhD graduates based on graduate program enrollment period, research training is on par with their single-degree peers, rendering MD-PhD graduates well equipped to become successful scientific investigators.
Authors
Rory Vu Mather, Temperance R. Rowell, Steve Obuchowski, Loren D. Walensky
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