The tumor microenvironment shows a hierarchy of cell-cell interactions dominated by fibroblasts

The tumor microenvironment (TME) is comprised of non-malignant cells that interact with each other and with cancer cells, critically impacting cancer biology. The TME is complex, and understanding it requires simplifying approaches. Here we provide an experimental-mathematical approach to decompose the TME into small circuits of interacting cell types. We find, using female breast cancer single-cell-RNA-sequencing data, a hierarchical network of interactions, with cancer-associated fibroblasts (CAFs) at the top secreting factors primarily to tumor-associated macrophages (TAMs). This network is composed of repeating circuit motifs. We isolate the strongest two-cell circuit motif by culturing fibroblasts and macrophages in-vitro, and analyze their dynamics and transcriptomes. This isolated circuit recapitulates the hierarchy of in-vivo interactions, and enables testing the effect of ligand-receptor interactions on cell dynamics and function, as we demonstrate by identifying a mediator of CAF-TAM interactions - RARRES2, and its receptor CMKLR1. Thus, the complexity of the TME may be simplified by identifying small circuits, facilitating the development of strategies to modulate the TME.

BRCA mutational status shapes the stromal microenvironment of pancreatic cancer linking clusterin expression in cancer associated fibroblasts with HSF1 signaling

Tumors initiate by mutations in cancer cells, and progress through interactions of the cancer cells with non-malignant cells of the tumor microenvironment. Major players in the tumor microenvironment are cancer-associated fibroblasts (CAFs), which support tumor malignancy, and comprise up to 90% of the tumor mass in pancreatic cancer. CAFs are transcriptionally rewired by cancer cells. Whether this rewiring is differentially affected by different mutations in cancer cells is largely unknown. Here we address this question by dissecting the stromal landscape of BRCA-mutated and BRCA Wild-type pancreatic ductal adenocarcinoma. We comprehensively analyze pancreatic cancer samples from 42 patients, revealing different CAF subtype compositions in germline BRCA-mutated vs. BRCA Wild-type tumors. In particular, we detect an increase in a subset of immune-regulatory clusterin-positive CAFs in BRCA-mutated tumors. Using cancer organoids and mouse models we show that this process is mediated through activation of heat-shock factor 1, the transcriptional regulator of clusterin. Our findings unravel a dimension of stromal heterogeneity influenced by germline mutations in cancer cells, with direct implications for clinical research.

Abstract LB009: Dynamic changes in the compositions of cancer associated-fibroblasts correlate with clinical outcome in breast cancer

Cancer associated fibroblasts (CAFs) are prevalent in carcinomas. CAFs are also heterogeneous and perform various tumor-promoting tasks. Understanding whether distinct CAF-subsets exert specific functions, and how the composition of CAFs changes as tumors evolve could improve the accuracy of cancer treatment. Here, we analyzed thousands of CAFs by single-cell RNA-sequencing and index-sorting at several timepoints along breast tumor progression in mice, revealing distinct CAF-subsets. We discovered that the transcriptional programs of these subsets change over time, shifting from an immune-regulatory program at earlier timepoints to wound-healing and antigen-presenting programs at later timepoints, indicating that the composition and functions of CAFs are dynamic. We also found the two main CAF subsets in human breast tumors, wherein their ratio was associated with disease outcome. This association was particularly correlated with BRCA mutations in triple-negative breast cancer. Our findings indicate that the diverse composition of CAFs in breast cancer changes over time as tumors progress, and that these changes are linked to disease outcome.

Citation Format: Gil Friedman, Oshrat Levi-Galibov, Eyal David, Chamutal Bornstein, Amir Giladi, Maya Dadiani, Avi Mayo, Coral Halperin, Meirav Pevsner-Fischer, Hagar Lavon, Shimrit Mayer, Reinat Nevo, Yaniv Stein, Nora Balint-Lahat, Iris Barshack, H. Raza Ali, Carlos Caldas, Einav Nili Gal-Yam, Uri Alon, Ido Amit, Ruth Scherz-Shouval. Dynamic changes in the compositions of cancer associated-fibroblasts correlate with clinical outcome in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB009.

Abstract LB204: HSF1 promotes inflammation induced tumor development through ECM remodeling

HSF1 promotes inflammation induced tumor development through ECM remodelingAbstractIn the colon, long-term exposure to chronic inflammation drives colitis associated colon cancer (CAC) in patients with inflammatory bowel disease (IBD). Chronic inflammation underlies tumor initiation, promotion, invasion, and metastasis. While the causal and clinical link between chronic inflammation and CAC is well established, we lack a molecular understanding of what is the way in which chronic inflammation leads to develop colon cancer. Within the tumor, cancer cells are surrounded by a variety of non-malignant cells, such as macrophages, endothelial cells, neutrophils, cancer-associated fibroblasts (CAFs), and together with the extracellular matrix (ECM) they compose the tumor microenvironment (TME), also termed the stroma. Even the most aggressive cancers depend and interact with their environment mostly through secreted factors. Unlike cancer cells, stromal cells are genomically stable, and do not harbor oncogenic mutations that could drive their co-evolution and functional reprogramming. Rather, stromal reprogramming is thought to be achieved by transcriptional rewiring. Previous work by us and others has shown that the master regulator heat shock factor 1 (HSF1) plays a crucial role in this process, by mediating a transcriptional program in fibroblasts that enables their reprogramming into cancer-associated fibroblasts (CAFs) to promote malignancy. We hypothesizde that HSF1 plays a crucial role in inflammation-driven cancer by initiation of a transcriptional program that leads to changes in the extracellular matrix (ECM). We found that, in cell culture, cancer-induced ECM assembly by fibroblasts requires HSF1. Using an inflammation-driven cancer model in mice, we measured the changes in proteomic and ECM organization over time. We found that HSF1 drives a transcriptional program that leads to ECM remodeling in early stages and results in development of colon cancer. Loss of HSF1 prevents inflammation-induced ECM remodeling. Further to that, in CAC patients, we found high activation of stromal HSF1 and similarity to our HSF1 proteomic ECM signature in human colorectal cancer driven by HSF1. Thus, HSF1-dependent ECM remodeling mediates the transition from chronic inflammation to colon cancer.

Citation Format: Oshrat Levi Galibov, Hagar Lavon, Rina Wassermann-Dozorets, Meirav Pevsner-Fischer, Shimrit Mayer, Esther Wershof, Yaniv Stein, Lauren E. Brown, Wenhan Zhang, Gil Friedman, Reinat Nevo, Ofra Golani, Lior H. Katz, Rona Yaeger, Ido Laish, John A. Porco, Erik Sahai, Dror S Shouval, David Kelsen, Ruth Scherz-Shouval. HSF1 promotes inflammation induced tumor development through ECM remodeling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB204.

Cancer-Associated Fibroblasts Promote Aggressive Gastric Cancer Phenotypes via Heat Shock Factor 1-Mediated Secretion of Extracellular Vesicles

Gastric cancer is the third most lethal cancer worldwide, and evaluation of the genomic status of gastric cancer cells has not translated into effective prognostic or therapeutic strategies. We therefore hypothesize that outcomes may depend on the tumor microenvironment (TME), in particular, cancer-associated fibroblasts (CAF). However, very little is known about the role of CAFs in gastric cancer. To address this, we mapped the transcriptional landscape of human gastric cancer stroma by microdissection and RNA sequencing of CAFs from patients with gastric cancer. A stromal gene signature was associated with poor disease outcome, and the transcription factor heat shock factor 1 (HSF1) regulated the signature. HSF1 upregulated inhibin subunit beta A and thrombospondin 2, which were secreted in CAF-derived extracellular vesicles to the TME to promote cancer. Together, our work provides the first transcriptional map of human gastric cancer stroma and highlights HSF1 and its transcriptional targets as potential diagnostic and therapeutic targets in the genomically stable tumor microenvironment. SIGNIFICANCE: This study shows how HSF1 regulates a stromal transcriptional program associated with aggressive gastric cancer and identifies multiple proteins within this program as candidates for therapeutic intervention. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/7/1639/F1.large.jpg.

Heat Shock Factor 1-dependent extracellular matrix remodeling mediates the transition from chronic intestinal inflammation to colon cancer

In the colon, long-term exposure to chronic inflammation drives colitis-associated colon cancer (CAC) in patients with inflammatory bowel disease. While the causal and clinical links are well established, molecular understanding of how chronic inflammation leads to the development of colon cancer is lacking. Here we deconstruct the evolving microenvironment of CAC by measuring proteomic changes and extracellular matrix (ECM) organization over time in a mouse model of CAC. We detect early changes in ECM structure and composition, and report a crucial role for the transcriptional regulator heat shock factor 1 (HSF1) in orchestrating these events. Loss of HSF1 abrogates ECM assembly by colon fibroblasts in cell-culture, prevents inflammation-induced ECM remodeling in mice and inhibits progression to CAC. Establishing relevance to human disease, we find high activation of stromal HSF1 in CAC patients, and detect the HSF1-dependent proteomic ECM signature in human colorectal cancer. Thus, HSF1-dependent ECM remodeling plays a crucial role in mediating inflammation-driven colon cancer.

Cancer-associated fibroblast compositions change with breast cancer progression linking the ratio of S100A4+ and PDPN+ CAFs to clinical outcome

Tumors are supported by cancer-associated fibroblasts (CAFs). CAFs are heterogeneous and carry out distinct cancer-associated functions. Understanding the full repertoire of CAFs and their dynamic changes as tumors evolve could improve the precision of cancer treatment. Here we comprehensively analyze CAFs using index and transcriptional single-cell sorting at several time points along breast tumor progression in mice, uncovering distinct subpopulations. Notably, the transcriptional programs of these subpopulations change over time and in metastases, transitioning from an immunoregulatory program to wound-healing and antigen-presentation programs, indicating that CAFs and their functions are dynamic. Two main CAF subpopulations are also found in human breast tumors, where their ratio is associated with disease outcome across subtypes and is particularly correlated with BRCA mutations in triple-negative breast cancer. These findings indicate that the repertoire of CAF changes over time in breast cancer progression, with direct clinical implications.

Induction of Nitric-Oxide Metabolism in Enterocytes Alleviates Colitis and Inflammation-Associated Colon Cancer

Nitric oxide (NO) plays an established role in numerous physiological and pathological processes, but the specific cellular sources of NO in disease pathogenesis remain unclear, preventing the implementation of NO-related therapy. Argininosuccinate lyase (ASL) is the only enzyme able to produce arginine, the substrate for NO generation by nitric oxide synthase (NOS) isoforms. Here, we generated cell-specific conditional ASL knockout mice in combination with genetic and chemical colitis models. We demonstrate that NO derived from enterocytes alleviates colitis by decreasing macrophage infiltration and tissue damage, whereas immune cell-derived NO is associated with macrophage activation, resulting in increased severity of inflammation. We find that induction of endogenous NO production by enterocytes with supplements that upregulate ASL expression and complement its substrates results in improved epithelial integrity and alleviation of colitis and of inflammation-associated colon cancer.

Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT

Probiotics are widely prescribed for prevention of antibiotics-associated dysbiosis and related adverse effects. However, probiotic impact on post-antibiotic reconstitution of the gut mucosal host-microbiome niche remains elusive. We invasively examined the effects of multi-strain probiotics or autologous fecal microbiome transplantation (aFMT) on post-antibiotic reconstitution of the murine and human mucosal microbiome niche. Contrary to homeostasis, antibiotic perturbation enhanced probiotics colonization in the human mucosa but only mildly improved colonization in mice. Compared to spontaneous post-antibiotic recovery, probiotics induced a markedly delayed and persistently incomplete indigenous stool/mucosal microbiome reconstitution and host transcriptome recovery toward homeostatic configuration, while aFMT induced a rapid and near-complete recovery within days of administration. In vitro, Lactobacillus-secreted soluble factors contributed to probiotics-induced microbiome inhibition. Collectively, potential post-antibiotic probiotic benefits may be offset by a compromised gut mucosal recovery, highlighting a need of developing aFMT or personalized probiotic approaches achieving mucosal protection without compromising microbiome recolonization in the antibiotics-perturbed host.

Correction to: Human umbilical cord-derived mesenchymal stem cells protect against experimental colitis via CD5+ B regulatory cells

The original article [1] contains a duplication error within Figure 3.

The Citrobacter rodentium type III secretion system effector EspO affects mucosal damage repair and antimicrobial responses

Infection with Citrobacter rodentium triggers robust tissue damage repair responses, manifested by secretion of IL-22, in the absence of which mice succumbed to the infection. Of the main hallmarks of C. rodentium infection are colonic crypt hyperplasia (CCH) and dysbiosis. In order to colonize the host and compete with the gut microbiota, C. rodentium employs a type III secretion system (T3SS) that injects effectors into colonic intestinal epithelial cells (IECs). Once injected, the effectors subvert processes involved in innate immune responses, cellular metabolism and oxygenation of the mucosa. Importantly, the identity of the effector/s triggering the tissue repair response is/are unknown. Here we report that the effector EspO ,an orthologue of OspE found in Shigella spp, affects proliferation of IECs 8 and 14 days post C. rodentium infection as well as secretion of IL-22 from colonic explants. While we observed no differences in the recruitment of group 3 innate lymphoid cells (ILC3s) and T cells, which are the main sources of IL-22 at the early and late stages of C. rodentium infection respectively, infection with ΔespO was characterized by diminished recruitment of sub-mucosal neutrophils, which coincided with lower abundance of Mmp9 and chemokines (e.g. S100a8/9) in IECs. Moreover, mice infected with ΔespO triggered significantly lesser nutritional immunity (e.g. calprotectin, Lcn2) and expression of antimicrobial peptides (Reg3β, Reg3γ) compared to mice infected with WT C. rodentium. This overlapped with a decrease in STAT3 phosphorylation in IECs. Importantly, while the reduced CCH and abundance of antimicrobial proteins during ΔespO infection did not affect C. rodentium colonization or the composition of commensal Proteobacteria, they had a subtle consequence on Firmicutes subpopulations. EspO is the first bacterial virulence factor that affects neutrophil recruitment and secretion of IL-22, as well as expression of antimicrobial and nutritional immunity proteins in IECs.

Citrobacter rodentium Relies on Commensals for Colonization of the Colonic Mucosa

We investigated the role of commensals at the peak of infection with the colonic mouse pathogen Citrobacter rodentium. Bioluminescent and kanamycin (Kan)-resistant C. rodentium persisted avirulently in the cecal lumen of mice continuously treated with Kan. A single Kan treatment was sufficient to displace C. rodentium from the colonic mucosa, a phenomenon not observed following treatment with vancomycin (Van) or metronidazole (Met). Kan, Van, and Met induce distinct dysbiosis, suggesting C. rodentium relies on specific commensals for colonic colonization. Expression of the master virulence regulator ler is induced in germ-free mice, yet C. rodentium is only seen in the cecal lumen. Moreover, in conventional mice, a single Kan treatment was sufficient to displace C. rodentium constitutively expressing Ler from the colonic mucosa. These results show that expression of virulence genes is not sufficient for colonization of the colonic mucosa and that commensals are essential for a physiological infection course.

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Specific dysbiosis rapidly displaces Citrobacter rodentium from the colonic mucosa

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Mucosal exclusion is independent of C. rodentium virulence gene expression

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Extended antibiotic treatment causes accumulation of luminal avirulent C. rodentium

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C. rodentium relies on commensals for survival at the colonic mucosa

Hyperglycemia drives intestinal barrier dysfunction and risk for enteric infection

Obesity, diabetes, and related manifestations are associated with an enhanced, but poorly understood, risk for mucosal infection and systemic inflammation. Here, we show in mouse models of obesity and diabetes that hyperglycemia drives intestinal barrier permeability, through GLUT2-dependent transcriptional reprogramming of intestinal epithelial cells and alteration of tight and adherence junction integrity. Consequently, hyperglycemia-mediated barrier disruption leads to systemic influx of microbial products and enhanced dissemination of enteric infection. Treatment of hyperglycemia, intestinal epithelial-specific GLUT2 deletion, or inhibition of glucose metabolism restores barrier function and bacterial containment. In humans, systemic influx of intestinal microbiome products correlates with individualized glycemic control, indicated by glycated hemoglobin levels. Together, our results mechanistically link hyperglycemia and intestinal barrier function with systemic infectious and inflammatory consequences of obesity and diabetes.

The anti-inflammatory IFITM genes ameliorate colitis and partially protect from tumorigenesis by changing immunity and microbiota

Inflammation plays pivotal roles in different stages of tumor development. Screening for predisposing genetic abnormalities and understanding the roles these genes play in the crosstalk between immune and cancer cells will provide new targets for cancer therapy and prevention. The interferon inducible transmembrane (IFITM) genes are involved in pathogenesis of the gastro-intestinal tract. We aimed at delineating the role of IFITM3 in colonic epithelial homeostasis, inflammation and colitis-associated tumorigenesis using IFITM3-deficient mice. Chemical induction of colitis in IFITM3-deficient mice results in significantly increased clinical signs of inflammation and induction of invasive tumorigenesis. Bone marrow transplantation showed that cells of the hematopoietic system are responsible for colitis deterioration. In these mice, impaired cytokine expression skewed inflammatory response toward pathogenic Th17 with reduced expression of the anti-inflammatory cytokine IL10 during the recovery phase. Intriguingly, mice lacking the entire IFITM locus developed spontaneous chronic colitis from the age of 14 weeks. Sequencing the 16S rRNA of naïve mice lacking IFITM3 gene, or the entire locus containing five IFITM genes, revealed these mice had significant bacterial differences from their wild-type littermates. Our novel results provide strong evidence for the essential role of IFITM genes in ameliorating colitis and colitis-associated tumorigenesis.

Cultured Mesenchymal Stem Cells Stimulate an Immune Response by Providing Immune Cells with Toll-Like Receptor 2 Ligand

Mesenchymal stem cells (MSCs) serve as supporting and regulatory cells, by providing tissues with multiple factors and are also known for their immunosuppressive capabilities. Our laboratory had previously shown that MSCs expressed toll-like receptor (TLR) 2 and are activated by its ligand Pam3Cys. TLR2 is an important component of the innate immune system, as it recognizes bacterial lipopeptides, thus priming a pro-inflammatory immune response. This study showed that Pam3Cys attached extensively to cells of both wild-type and TLR2 deficient cultured MSCs, thus, independently of TLR2. The TLR2 independent binding occurred through the adsorption of the palmitoyl moieties of Pam3Cys. It was further showed that Pam3Cys was transferred from cultured MSCs to immune cells. Moreover, Pam3Cys provided to the immune cells induced a pro-inflammatory response in vitro and in vivo. Overall, it is demonstrated herein that a TLR2 ligand bound to MSCs also through a TLR2 independent mechanism. Furthermore, the ligand incorporated by MSCs is subsequently released to stimulate an immune response both in vitro and in vivo. It is thus suggested that during bacterial infection, stromal cells may retain a reservoir of the TLR2 ligands, in a long-term manner, and release them slowly to maintain an immune response.

The Spectrum and Regulatory Landscape of Intestinal Innate Lymphoid Cells Are Shaped by the Microbiome

Innate lymphoid cells (ILCs) are critical modulators of mucosal immunity, inflammation, and tissue homeostasis, but their full spectrum of cellular states and regulatory landscapes remains elusive. Here, we combine genome-wide RNA-seq, ChIP-seq, and ATAC-seq to compare the transcriptional and epigenetic identity of small intestinal ILCs, identifying thousands of distinct gene profiles and regulatory elements. Single-cell RNA-seq and flow and mass cytometry analyses reveal compartmentalization of cytokine expression and metabolic activity within the three classical ILC subtypes and highlight transcriptional states beyond the current canonical classification. In addition, using antibiotic intervention and germ-free mice, we characterize the effect of the microbiome on the ILC regulatory landscape and determine the response of ILCs to microbial colonization at the single-cell level. Together, our work characterizes the spectrum of transcriptional identities of small intestinal ILCs and describes how ILCs differentially integrate signals from the microbial microenvironment to generate phenotypic and functional plasticity.

Human umbilical cord-derived mesenchymal stem cells protect against experimental colitis via CD5(+) B regulatory cells

Background

To clarify the effect of human umbilical cord-derived mesenchymal stem cell (hUC-MSCs) treatment on colitis and to explore the role of CD5⁺ B cells in MSC therapy.

Methods

The trinitrobenzenesulfonic acid (TNBS)-induced colitis mouse model was used. HUC-MSCs were transferred peritoneally. Survival rates, colitis symptoms, and macroscopic and histologic scores were evaluated. CD4⁺ T helper (Th) cell subgroups and CD5⁺ regulatory B cell (Bregs) in lymphocytes were quantitated by flow cytometry. Cytokine levels were detected by ELISA and Bio-plex. CD5⁺ B cells were isolated for in vitro co-culture and adaptive transfer.

Results

HUC-MSC treatment alleviated TNBS-induced colitis by increasing survival rates, relieving symptoms, and improving macroscopic and histologic scores. Labeled hUC-MSCs were located in the inflamed areas of colitis mice. Increases in regulatory T cells (Tregs) and CD5⁺ B cells and decreases in Th1 cells, Th17 cells, and several pro-inflammatory cytokines were observed with hUC-MSC treatment. After adaptive transfer, CD5⁺ B cells, which were located mainly in the peritoneal lavage fluid, improved TNBS-induced colitis by correcting Treg/Th1/Th17 imbalances. CD5⁺ B cells also inhibited T-cell proliferation and produced interleukin (IL)-10.

Conclusions

HUC-MSCs protected against experimental colitis by boosting the numbers of CD5⁺ B cells and IL-10-producing CD5⁺ Bregs, and correcting Treg/Th17/Th1 imbalances.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0376-2) contains supplementary material, which is available to authorized users.

Role of the microbiome in non-gastrointestinal cancers

“The forgotten organ”, the human microbiome, comprises a community of microorganisms that colonizes various sites of the human body. Through coevolution of bacteria, archaea and fungi with the human host over thousands of years, a complex host-microbiome relationship emerged in which many functions, including metabolism and immune responses, became codependent. This coupling becomes evident when disruption in the microbiome composition, termed dysbiosis, is mirrored by the development of pathologies in the host. Among the most serious consequences of dysbiosis, is the development of cancer. As many as 20% of total cancers worldwide are caused by a microbial agent. To date, a vast majority of microbiome-cancer studies focus solely on the microbiome of the large intestine and the development of gastrointestinal cancers. Here, we will review the available evidence implicating microbiome involvement in the development and progression of non-gastrointestinal cancers, while distinguishing between viral and bacterial drivers of cancer, as well as “local” and “systemic”, “cancer-stimulating” and “cancer-suppressing” effects of the microbiome. Developing a system-wide approach to cancer-microbiome studies will be crucial in understanding how microbiome influences carcinogenesis, and may enable to employ microbiome-targeting approaches as part of cancer treatment.

Microbiota-Modulated Metabolites Shape the Intestinal Microenvironment by Regulating NLRP6 Inflammasome Signaling

Host-microbiome co-evolution drives homeostasis and disease susceptibility, yet regulatory principles governing the integrated intestinal host-commensal microenvironment remain obscure. While inflammasome signaling participates in these interactions, its activators and microbiome-modulating mechanisms are unknown. Here, we demonstrate that the microbiota-associated metabolites taurine, histamine, and spermine shape the host-microbiome interface by co-modulating NLRP6 inflammasome signaling, epithelial IL-18 secretion, and downstream anti-microbial peptide (AMP) profiles. Distortion of this balanced AMP landscape by inflammasome deficiency drives dysbiosis development. Upon fecal transfer, colitis-inducing microbiota hijacks this microenvironment-orchestrating machinery through metabolite-mediated inflammasome suppression, leading to distorted AMP balance favoring its preferential colonization. Restoration of the metabolite-inflammasome-AMP axis reinstates a normal microbiota and ameliorates colitis. Together, we identify microbial modulators of the NLRP6 inflammasome and highlight mechanisms by which microbiome-host interactions cooperatively drive microbial community stability through metabolite-mediated innate immune modulation. Therefore, targeted "postbiotic" metabolomic intervention may restore a normal microenvironment as treatment or prevention of dysbiosis-driven diseases.

Personalized Nutrition by Prediction of Glycemic Responses

Elevated postprandial blood glucose levels constitute a global epidemic and a major risk factor for prediabetes and type II diabetes, but existing dietary methods for controlling them have limited efficacy. Here, we continuously monitored week-long glucose levels in an 800-person cohort, measured responses to 46,898 meals, and found high variability in the response to identical meals, suggesting that universal dietary recommendations may have limited utility. We devised a machine-learning algorithm that integrates blood parameters, dietary habits, anthropometrics, physical activity, and gut microbiota measured in this cohort and showed that it accurately predicts personalized postprandial glycemic response to real-life meals. We validated these predictions in an independent 100-person cohort. Finally, a blinded randomized controlled dietary intervention based on this algorithm resulted in significantly lower postprandial responses and consistent alterations to gut microbiota configuration. Together, our results suggest that personalized diets may successfully modify elevated postprandial blood glucose and its metabolic consequences. VIDEO ABSTRACT.

Cell isolation induces fate changes of bone marrow mesenchymal cells leading to loss or alternatively to acquisition of new differentiation potentials

Mesenchymal stromal cell populations include a fraction, termed mesenchymal stem cells, exhibiting multipotency. Other cells within this population possess a lesser differentiation range. This was assumed to be due to a mesenchymal cellular cascade topped by a multipotent cell, which gives rise to progeny with diminishing differentiation potentials. Here, we show that mesenchymal cells, a priori exhibiting a limited differentiation potential, may gain new capacities and become multipotent following single-cell isolation. These fate changes were accompanied by upregulation of differentiation promoting genes, many of which also became H4K20me1 methylated. Early events in the process included TGFβ and Wnt modulation, and downregulation of hypoxia signaling. Indeed, hypoxic conditions inhibited the observed cell changes. Overall, cell isolation from neighboring partners caused major molecular changes and particularly, a newly established epigenetic state, ultimately leading to the acquisition of new differentiation potentials and an altered cell fate.

Growth dynamics of gut microbiota in health and disease inferred from single metagenomic samples

Metagenomic sequencing increased our understanding of the role of the microbiome in health and disease, yet it only provides a snapshot of a highly dynamic ecosystem. Here, we show that the pattern of metagenomic sequencing read coverage for different microbial genomes contains a single trough and a single peak, the latter coinciding with the bacterial origin of replication. Furthermore, the ratio of sequencing coverage between the peak and trough provides a quantitative measure of a species' growth rate. We demonstrate this in vitro and in vivo, under different growth conditions, and in complex bacterial communities. For several bacterial species, peak-to-trough coverage ratios, but not relative abundances, correlated with the manifestation of inflammatory bowel disease and type II diabetes.

Divergent levels of LBP and TGFβ1 in murine MSCs lead to heterogenic response to TLR and proinflammatory cytokine activation

The outstanding heterogeneity of stem cell populations is a major obstacle on the way to their clinical application. It is therefore paramount to identify the molecular mechanisms that underlay this heterogeneity. Individually derived bone marrow mesenchymal stromal cells (MSCs) preparations, studied here, diverged markedly in various properties, despite of being all tripotent in their differentiation potential. Microarray analysis showed that MSC diversity is evident also in highly variable gene expression patterns. Differentially expressed genes were significantly enriched in toll-like receptors (TLRs) and differentiation pathways. Marked differences were observed in LPS binding protein (LBP) and transforming growth factor (TGF)β1 expression. These differences correlated with MSC functionality. Therefore, the possible contribution of these molecules to MSC diversity was examined. In the TLR signaling pathway, LBP levels predicted the ability of specific MSCs to secrete interleukin (IL)-6 in response to LPS. A relatively higher expression of TGFβ1 endowed MSCs with a capacity to respond to IL-1β by reduced osteogenic differentiation. This study thus demonstrates major diversity within MSC isolates, which appears early on following derivation and persists following long-term culture. MSC heterogeneity results from highly variable transcriptome. Differential expression of LBP and TGFβ1, along with other genes, in different MSC preparations, produces the variable responses to external stimuli.

The origin of human mesenchymal stromal cells dictates their reparative properties

Background

Human mesenchymal stromal cells (hMSCs) from adipose cardiac tissue have attracted considerable interest in regard to cell‐based therapies. We aimed to test the hypothesis that hMSCs from the heart and epicardial fat would be better cells for infarct repair.

Methods and Results

We isolated and grew hMSCs from patients with ischemic heart disease from 4 locations: epicardial fat, pericardial fat, subcutaneous fat, and the right atrium. Significantly, hMSCs from the right atrium and epicardial fat secreted the highest amounts of trophic and inflammatory cytokines, while hMSCs from pericardial and subcutaneous fat secreted the lowest. Relative expression of inflammation‐ and fibrosis‐related genes was considerably higher in hMSCs from the right atrium and epicardial fat than in subcutaneous fat hMSCs. To determine the functional effects of hMSCs, we allocated rats to hMSC transplantation 7 days after myocardial infarction. Atrial hMSCs induced greatest infarct vascularization as well as highest inflammation score 27 days after transplantation. Surprisingly, cardiac dysfunction was worst after transplantation of hMSCs from atrium and epicardial fat and minimal after transplantation of hMSCs from subcutaneous fat. These findings were confirmed by using hMSC transplantation in immunocompromised mice after myocardial infarction. Notably, there was a correlation between tumor necrosis factor‐α secretion from hMSCs and posttransplantation left ventricular remodeling and dysfunction.

Conclusions

Because of their proinflammatory properties, hMSCs from the right atrium and epicardial fat of cardiac patients could impair heart function after myocardial infarction. Our findings might be relevant to autologous mesenchymal stromal cell therapy and development and progression of ischemic heart disease.

Stable changes in mesenchymal stromal cells from multiple myeloma patients revealed through their responses to Toll-like receptor ligands and epidermal growth factor

In human multiple myeloma (MM), the tumor cells exhibit strict dependence on bone marrow (BM) stromal elements. It has been suggested that, in turn, MM cells modify multipotent stromal cells (MSCs), diverting them to support the myeloma. We investigated MM-derived MSCs by comparing their toll-like receptor (TLR) responses to those of MSCs derived from healthy controls. We now report that MM-derived MSCs manifested intact proliferation responses and IL-6 secretion and their adipose and osteogenic differentiation responses to TLR ligands were also similar to those of healthy controls, ranging from augmentation to inhibition. However, MM-derived MSCs were found to be defective in IL-8 secretion and ERK1/2 phosphorylation following TLR-2 activation. Moreover, MM-derived MSCs failed to respond to EGF by elevation of ERK1/2 phosphorylation. The persistence of these changes in extensively cultured MM-derived MSCs, suggests that these cells are stably, if not irreversibly modified.

Heat shock protein 60, via MyD88 innate signaling, protects B cells from apoptosis, spontaneous and induced

We recently reported that heat shock protein 60 (HSP60) via TLR4 signaling activates B cells and induces them to proliferate and secrete IL-10. We now report that HSP60 inhibits mouse B cell apoptosis, spontaneous or induced by dexamethasone or anti-IgM activation. Unlike HSP60 enhancement of B cell proliferation and IL-10 secretion, TLR4 signaling was not required for the inhibition of apoptosis by HSP60; nevertheless, MyD88 was essential. Inhibition of apoptosis by HSP60 was associated with up-regulation of the antiapoptotic molecules Bcl-2, Bcl-x(L), and survivin, maintenance of the mitochondrial transmembrane potential, and inhibition of caspase-3 activation. Moreover, B cells incubated with HSP60 manifested prolonged survival following transfer into recipient mice. These results extend the varied role of HSP60 in the innate regulation of the adaptive immune response.

p53 plays a role in mesenchymal differentiation programs, in a cell fate dependent manner

Background

The tumor suppressor p53 is an important regulator that controls various cellular networks, including cell differentiation. Interestingly, some studies suggest that p53 facilitates cell differentiation, whereas others claim that it suppresses differentiation. Therefore, it is critical to evaluate whether this inconsistency represents an authentic differential p53 activity manifested in the various differentiation programs.

Methodology/Principal Findings

To clarify this important issue, we conducted a comparative study of several mesenchymal differentiation programs. The effects of p53 knockdown or enhanced activity were analyzed in mouse and human mesenchymal cells, representing various stages of several differentiation programs. We found that p53 down-regulated the expression of master differentiation-inducing transcription factors, thereby inhibiting osteogenic, adipogenic and smooth muscle differentiation of multiple mesenchymal cell types. In contrast, p53 is essential for skeletal muscle differentiation and osteogenic re-programming of skeletal muscle committed cells.

Conclusions

These comparative studies suggest that, depending on the specific cell type and the specific differentiation program, p53 may exert a positive or a negative effect, and thus can be referred as a “guardian of differentiation” at large.

The myelopoietic supportive capacity of mesenchymal stromal cells is uncoupled from multipotency and is influenced by lineage determination and interference with glycosylation

Cultured bone marrow stromal cells create an in vitro milieu supportive of long-term hemopoiesis and serve as a source for multipotent mesenchymal progenitor cells defined by their ability to differentiate into a variety of mesodermal derivatives. This study aims to examine whether the capacity to support myelopoiesis is coupled with the multipotency. Our results show that the myelopoietic supportive ability of stromal cells, whether from the bone marrow or from embryo origin, is not linked with multipotency; cell populations that possess multipotent capacity may or may not support myelopoiesis, whereas others, lacking multipotency, may possess full myelopoietic supportive ability. However, upon differentiation, the ability of multipotent mesenchymal progenitors to support myelopoiesis is varied. Osteogenic differentiation did not affect myelopoietic supportive capacity, whereas adipogenesis resulted in reduced ability to support the maintenance of myeloid progenitor cells. These differences were accompanied by a divergence in glycosylation patterns, as measured by binding to lectin microarrays; osteogenic differentiation was associated with an increased level of antennarity of N-linked glycans, whereas adipogenic differentiation caused a decrease in antennarity. Inhibition of glycosylation prior to seeding the stroma with bone marrow cells resulted in reduced capacity of the stromal cells to support the formation of cobblestone areas. Our data show that myelopoietic support is unrelated to the multipotent phenotype of cultured mesenchymal progenitors but is dependent on the choice of differentiation pathway and upon correct glycosylation of the stromal cells.

Characterization of the interacting domain of the HIV-1 fusion peptide with the transmembrane domain of the T-cell receptor

HIV infection is initiated by the fusion of the viral membrane with the target T-cell membrane. The HIV envelope glycoprotein, gp41, contains a fusion peptide (FP) in the N terminus that functions together with other gp41 domains to fuse the virion with the host cell membrane. We recently reported that FP co-localizes with CD4 and T-cell receptor (TCR) molecules, co-precipitates with TCR, and inhibits antigen-specific T-cell proliferation and pro-inflammatory cytokine secretion. Molecular dynamic simulation implicated an interaction between an alpha-helical transmembrane domain (TM) of the TCRalpha chain (designated CP) and the beta-sheet 5-13 region of the 16 N-terminal amino acids of FP (FP(1-16)). To correlate between the theoretical prediction and experimental data, we synthesized a series of mutants derived from the interacting motif GALFLGFLG stretch (FP(5-13)) and investigated them structurally and functionally. The data reveal a direct correlation between the beta-sheet structure of FP(5-13) and its mutants and their ability to interact with CP and induce immunosuppressive activity; the phenylalanines play an important role. Furthermore, studies with fluorescently labeled peptides revealed that this interaction leads to penetration of the N terminus of FP and its active analogues into the hydrophobic core of the membrane. A detailed understanding of the molecular interactions mediating the immunosuppressive activity of the FP(5-13) motif should facilitate evaluating its contribution to HIV pathology and its exploitation as an immunotherapeutic tool.

Cutting Edge: T Cells Respond to Lipopolysaccharide Innately via TLR4 Signaling

LPS, a molecule produced by Gram-negative bacteria, is known to activate both innate immune cells such as macrophages and adaptive immune B cells via TLR4 signaling. Although TLR4 is also expressed on T cells, LPS was observed not to affect T cell proliferation or cytokine secretion. We now report, however, that LPS can induce human T cells to adhere to fibronectin via TLR4 signaling. This response to LPS was confirmed in mouse T cells; functional TLR4 and MyD88 were required, but T cells from TLR2 knockout mice could respond to LPS. The human T cell response to LPS depended on protein kinase C signaling and involved the phosphorylation of the proline-rich tyrosine kinase (Pyk-2) and p38. LPS also up-regulated the T cell expression of suppressor of cytokine signaling 3, which led to inhibition of T cell chemotaxis toward the chemokine stromal cell-derived factor 1alpha (CXCL12). Thus, LPS, through TLR4 signaling, can affect T cell behavior in inflammation.

Toll-like receptors and their ligands control mesenchymal stem cell functions

Mesenchymal stem cells (MSCs) are widespread in adult organisms and may be involved in tissue maintenance and repair as well as in the regulation of hematopoiesis and immunologic responses. Thus, it is important to discover the factors controlling MSC renewal and differentiation. Here we report that adult MSCs express functional Toll-like receptors (TLRs), confirmed by the responses of MSCs to TLR ligands. Pam3Cys, a prototypic TLR-2 ligand, augmented interleukin-6 secretion by MSC, induced nuclear factor kappa B (NF-kappaB) translocation, reduced MSC basal motility, and increased MSC proliferation. The hallmark of MSC function is the capacity to differentiate into several mesodermal lineages. We show herein that Pam3Cys inhibited MSC differentiation into osteogenic, adipogenic, and chondrogenic cells while sparing their immunosuppressive effect. Our study therefore shows that a TLR ligand can antagonize MSC differentiation triggered by exogenous mediators and consequently maintains the cells in an undifferentiated and proliferating state in vitro. Moreover, MSCs derived from myeloid factor 88 (MyD88)-deficient mice lacked the capacity to differentiate effectively into osteogenic and chondrogenic cells. It appears that TLRs and their ligands can serve as regulators of MSC proliferation and differentiation and might affect the maintenance of MSC multipotency.

Heat shock protein 60 activates B cells via the TLR4-MyD88 pathway

We recently reported that soluble 60-kDa heat shock protein (HSP60) can directly activate T cells via TLR2 signaling to enhance their Th2 response. In this study we investigated whether HSP60 might also activate B cells by an innate signaling pathway. We found that human HSP60 (but not the Escherichia coli GroEL or the Mycobacterial HSP65 molecules) induced naive mouse B cells to proliferate and to secrete IL-10 and IL-6. In addition, the HSP60-treated B cells up-regulated their expression of MHC class II and accessory molecules CD69, CD40, and B7-2. We tested the functional ability of HSP60-treated B cells to activate an allogeneic T cell response and found enhanced secretion of both IL-10 and IFN-gamma by the responding T cells. The effects of HSP60 were found to be largely dependent on TLR4 and MyD88 signaling; B cells from TLR4-mutant mice or from MyD88 knockout mice showed decreased responses to HSP60. Care was taken to rule out contamination of the HSP60 with LPS as a causative factor. These findings add B cells to the complex web of interactions by which HSP60 can regulate immune responses.