COL6A3-derived endotrophin links reciprocal interactions among hepatic cells in the pathology of chronic liver disease

In vitro integration of a functional vasculature to model endothelial regulation of chemotherapy and T-cell immunotherapy in liver cancer

The complex tumor microenvironment (TME) presents significant challenges to the development of effective therapies against solid tumors, highlighting the need for advanced in vitro models that better recapitulate TME biology. To address this, we developed a vascularized human liver tumor model using a microfluidic platform, designed to test both drug and cell-based therapies. This model mimics critical tumorigenic features such as hypoxia, extracellular matrix (ECM), and perfusable vascular networks. Intravascular administration of Sorafenib demonstrated its ability to disrupt vascular structures significantly, while eliciting heterogeneous responses in two distinct liver tumor cell lines, HepG2 and Hep3b. Furthermore, treatment with engineered T-cells revealed that the tumor vasculature impeded T-cell infiltration into the tumor core but preserved their cytotoxic capacity, albeit with reduced exhaustion levels. Cytokine analysis and spatial profiling of vascularized tumor samples identified proinflammatory factors that may enhance T-cell-mediated antitumor responses. By capturing key TME characteristics, this microfluidic platform provides a powerful tool enabling detailed investigation of tumor-immune and tumor-vascular interactions. Its versatility could serve as a promising bridge between preclinical studies and clinical testing, offering opportunities for developing and optimizing personalized therapeutic strategies for solid tumors.

The fibroblast hormone Endotrophin is a biomarker of mortality in chronic diseases

Fibrosis, driven by fibroblast activities, is an important contributor to morbidity and mortality in most chronic diseases. Endotrophin, a signaling molecule derived from processing of type VI collagen by highly activated fibroblasts, is involved in fibrotic tissue remodeling. Circulating levels of endotrophin have been associated with an increased risk of mortality in multiple chronic diseases. We conducted a systematic literature review collecting evidence from original papers published between 2012 and January 2023 that reported associations between circulating endotrophin (PROC6) and mortality. Cohorts with data available to the study authors were included in an Individual Patient Data (IPD) meta-analysis that evaluated the association of PROC6 with mortality (PROSPERO registration number: CRD42023340215) after adjustment for age, sex and BMI, where available. In the IPD meta-analysis including sixteen cohorts of patients with different non-communicable chronic diseases (NCCDs) (N = 15,205) the estimated summary hazard ratio for 3-years all-cause mortality was 2.10 (95 % CI 1.75-2.52) for a 2-fold increase in PROC6, with some heterogeneity observed between the studies (I2=70 %). This meta-analysis is the first study documenting that fibroblast activities, as quantified by circulating endotrophin, are independently associated with mortality across a broad range of NCCDs. This indicates that, irrespective of disease, interstitial tissue remodeling, and consequently fibroblast activities, has a central role in adverse clinical outcomes, and should be considered with urgency from drug developers as a target to treat.

Endotrophin, a Key Marker and Driver for Fibroinflammatory Disease

Our overview covers several key areas related to recent results obtained for collagen type VI and endotrophin (ETP). (1) An introduction to the history of ETP, including how it was identified, how it is released, and its function and potential receptors. (2) An introduction to the collagen family, with a focus on what differentiates collagen type VI from an evolutionary standpoint. (3) An overview of collagen type VI, the 6 individual chains (COL6A1, A2, A3, A4, A5, and A6), their differences and similarities, as well as their expression profiles and function. (4) A detailed analysis of COL6A3, including the cleaved product endotrophin, and what separates it from the other 5 collagen 6 molecules, including its suggested function based on insights gained from knockout and gain of function mouse models. (5) The pathology of ETP. What leads to its presence and release and what are the consequences thereof? (6) Functional implications of circulating ETP. Here we review the data with the functional roles of ETP in mind. (7) We propose that ETP is a mediator for fibrotic (or fibroinflammatory) disorders. Based on what we know about ETP, we have to consider it as a target for the treatment of fibrotic (or fibroinflammatory) disorders. What segment(s) of the patient population would most dramatically respond to an ETP-targeted intervention? How can we find the population that would profit most from an intervention? We aim to present a broad overview over the ETP field at large, providing an assessment of where the future research efforts need to be placed to tap into the vast potential of ETP, both as a marker and as a target in different diseases.

Changes in proteomic cargo of circulating extracellular vesicles in response to lifestyle intervention in adolescents with hepatic steatosis

BACKGROUND

Recent studies suggest that proteomic cargo of extracellular vesicles (EVs) may play a role in metabolic improvements following lifestyle interventions. However, the relationship between changes in liver fat and circulating EV-derived protein cargo following intervention remains unexplored.

METHODS

The study cohort comprised 18 Latino adolescents with obesity and hepatic steatosis (12 males/6 females; average age 13.3 ± 1.2 y) who underwent a six-month lifestyle intervention. EV size distribution and concentration were determined by light scattering intensity; EV protein composition was characterized by liquid chromatography tandem-mass spectrometry.

RESULTS

Average hepatic fat fraction (HFF) decreased 23% by the end of the intervention (12.5% [5.5] to 9.6% [4.9]; P = 0.0077). Mean EV size was smaller post-intervention compared to baseline (120.2 ± 16.4 nm to 128.4 ± 16.5 nm; P = 0.031), although the difference in mean EV concentration (1.1E+09 ± 4.1E+08 particles/mL to 1.1E+09 ± 1.8E+08 particles/mL; P = 0.656)) remained unchanged. A total of 462 proteins were identified by proteomic analysis of plasma-derived EVs from participants pre- and post-intervention, with 113 proteins showing differential abundance (56 higher and 57 lower) between the two timepoints (adj-p <0.05). Pathway analysis revealed enrichment in complement cascade, initial triggering of complement, creation of C4 and C2 activators, and regulation of complement cascade. Hepatocyte-specific EV affinity purification identified 40 proteins with suggestive (p < 0.05) differential abundance between pre- and post-intervention samples.

CONCLUSIONS

Circulating EV-derived proteins, particularly those associated with the complement cascade, may contribute to improvements in liver fat in response to lifestyle intervention.

Integration of transcriptomes of senescent cell models with multi-tissue patient samples reveals reduced COL6A3 as an inducer of senescence

Senescent cells are a major contributor to age-dependent cardiovascular tissue dysfunction, but knowledge of their in vivo cell markers and tissue context is lacking. To reveal tissue-relevant senescence biology, we integrate the transcriptomes of 10 experimental senescence cell models with a 224 multi-tissue gene co-expression network based on RNA-seq data of seven tissues biopsies from ∼600 coronary artery disease (CAD) patients. We identify 56 senescence-associated modules, many enriched in CAD GWAS genes and correlated with cardiometabolic traits-which supports universality of senescence gene programs across tissues and in CAD. Cross-tissue network analyses reveal 86 candidate senescence-associated secretory phenotype (SASP) factors, including COL6A3. Experimental knockdown of COL6A3 induces transcriptional changes that overlap the majority of the experimental senescence models, with cell-cycle arrest linked to modulation of DREAM complex-targeted genes. We provide a transcriptomic resource for cellular senescence and identify candidate biomarkers, SASP factors, and potential drivers of senescence in human tissues.

Limited Hyperoxia-Induced Proliferative Retinopathy (LHIPR) as a Model of Retinal Fibrosis, Angiogenesis, and Inflammation

The progression to fibrosis and traction in retinopathy of prematurity (ROP) and other ischemic retinopathies remains an important clinical and surgical challenge, necessitating a comprehensive understanding of its pathogenesis. Fibrosis is an unbalanced deposition of extracellular matrix components responsible for scar tissue formation with consequent tissue and organ impairment. Together with retinal traction, it is among the main causes of retinal detachment and vision loss. We capitalize on the Limited Hyperoxia Induced Retinopathy (LHIPR) model, as it reflects the more advanced pathological phenotypes seen in ROP and other ischemic retinopathies. To model LHIPR, we exposed wild-type C57Bl/6J mouse pups to 65% oxygen from P0 to P7. Then, the pups were returned to room air to recover until later endpoints. We performed histological and molecular analysis to evaluate fibrosis progression, angiogenesis, and inflammation at several time points, from 1.5 months to 9 months. In addition, we performed in vivo retinal imaging by optical coherence tomography (OCT) or OCT Angiography (OCTA) to follow the fibrovascular progression in vivo. Although the retinal morphology was relatively preserved, we found a progressive increase in preretinal fibrogenesis over time, up to 9 months of age. We also detected blood vessels in the preretinal space as well as an active inflammatory process, altogether mimicking advanced preretinal fibrovascular disease in humans.

High levels of intracellular endotrophin in adipocytes mediate COPII vesicle supplies to autophagosome to impair autophagic flux and contribute to systemic insulin resistance in obesity

BACKGROUND AND AIMS

Extracellular matrix (ECM) homeostasis plays a crucial role in metabolic plasticity and endocrine function of adipose tissue. High levels of intracellular endotrophin, a cleavage peptide of type VI collagen alpha 3 chain (Col6a3), have been frequently observed in adipocyte in obesity and diabetes. However, how endotrophin intracellularly traffics and influences metabolic homeostasis in adipocyte remains unknown. Therefore, we aimed to investigate the trafficking of endotrophin and its metabolic effects in adipocytes depending on lean or obese condition.

METHODS

We used doxycycline-inducible adipocyte-specific endotrophin overexpressed mice for a gain-of-function study and CRISPR-Cas9 system-based Col6a3-deficient mice for a loss-of-function study. Various molecular and biochemical techniques were employed to examine the effects of endotrophin on metabolic parameters.

RESULTS

In adipocytes during obesity, the majority of endosomal endotrophin escapes lysosomal degradation and is released into the cytosol to mediate direct interactions between SEC13, a major component of coat protein complex II (COPII) vesicles, and autophagy-related 7 (ATG7), leading to the increased formation of autophagosomes. Autophagosome accumulation disrupts the balance of autophagic flux, resulting in adipocyte death, inflammation, and insulin resistance. These adverse metabolic effects were ameliorated by either suppressing ATG7 with siRNA ex vivo or neutralizing endotrophin with monoclonal antibodies in vivo.

CONCLUSIONS

High levels of intracellular endotrophin-mediated autophagic flux impairment in adipocyte contribute to metabolic dysfunction such as apoptosis, inflammation, and insulin resistance in obesity.

Endotrophin Levels Are Associated with Allograft Outcomes in Kidney Transplant Recipients

Early prediction of kidney graft function may assist clinical management, and for this, reliable non-invasive biomarkers are needed. We evaluated endotrophin (ETP), a novel non-invasive biomarker of collagen type VI formation, as a prognostic marker in kidney transplant recipients. ETP levels were measured with the PRO-C6 ELISA in the plasma (P-ETP) of 218 and urine (U-ETP/Cr) of 172 kidney transplant recipients, one (D1) and five (D5) days, as well as three (M3) and twelve (M12) months, after transplantation. P-ETP and U-ETP/Cr at D1 (P-ETP AUC = 0.86, p < 0.0001; U-ETP/Cr AUC = 0.70, p = 0.0002) were independent markers of delayed graft function (DGF) and P-ETP at D1 had an odds ratio of 6.3 (p < 0.0001) for DGF when adjusted for plasma creatinine. The results for P-ETP at D1 were confirmed in a validation cohort of 146 transplant recipients (AUC = 0.92, p < 0.0001). U-ETP/Cr at M3 was negatively associated with kidney graft function at M12 (p = 0.007). This study suggests that ETP at D1 can identify patients at risk of delayed graft function and that U-ETP/Cr at M3 can predict the future status of the allograft. Thus, measuring collagen type VI formation could aid in predicting graft function in kidney transplant recipients.

Plasma endotrophin, reflecting tissue fibrosis, is associated with graft failure and mortality in KTRs: results from two prospective cohort studies

BACKGROUND

Fibrosis is a suggested cause of graft failure and mortality among kidney transplant recipients (KTRs). Accumulating evidence suggests that collagen type VI is tightly linked to fibrosis and may be a marker of systemic fibrosis and ageing. We studied whether plasma endotrophin, a pro-collagen type VI fragment, is associated with graft failure and mortality among KTRs.

METHODS

In cohort A (57% male, age 53 ± 13 years), we measured plasma endotrophin in 690 prevalent KTRs ≥1 year after transplantation. The non-overlapping cohort B included 500 incident KTRs with serial endotrophin measurements before and after kidney transplantation to assess trajectories and intra-individual variation of endotrophin.

RESULTS

In cohort A, endotrophin was higher in KTRs compared with healthy controls. Concentrations were positively associated with female sex, diabetes, cardiovascular disease, markers of inflammation and kidney injury. Importantly, endotrophin was associated with graft failure {hazard ratio [HR] per doubling 1.87 [95% confidence interval (CI) 1.07-3.28]} and mortality [HR per doubling 2.59 (95% CI 1.73-3.87)] independent of potential confounders. Data from cohort B showed that endotrophin concentrations strongly decrease after transplantation and remain stable during post-transplantation follow-up [intra-individual coefficient of variation 5.0% (95% CI 3.7-7.6)].

CONCLUSIONS

Plasma endotrophin is strongly associated with graft failure and mortality among KTRs. These findings suggest a key role of abnormal extracellular matrix turnover and fibrosis in graft and patient prognosis among KTRs and highlight the need for (interventional) studies targeting the profibrotic state of KTRs. The intra-individual stability after transplantation indicates potential use of endotrophin as a biomarker and outcome measure of fibrosis.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02811835.

Biomarkers of fibrosis, kidney tissue injury and inflammation may predict severity and outcome of renal ANCA – associated vasculitis

Background

Activity and chronicity of kidney involvement in ANCA-associated vasculitis (AAV) can be currently reliably evaluated only by kidney biopsy. In this study, we measured a panel of serum and urinary biomarkers collected at the time of kidney biopsy and hypothesized that they could reflect specific histopathological parameters in the biopsy and help to predict prognosis.

Methods

We examined a cohort of 45 patients with AAV and 10 healthy controls. Biomarker levels (DKK-3, CD163, EGF, PRO-C6 and C3M) were measured in this study by ELISA. Biopsies were scored with a scoring system for AAV (focal x crescentic x sclerotic x mixed class) and interstitial fibrosis was quantified.

Results

Levels of urinary DKK-3, CD163, EGF, PRO-C6 and C3M significantly differed among biopsy classes in AAV, with urinary DKK-3 and PRO-C6 levels being highest in the sclerotic class and lowest in the focal class, urinary CD163 levels highest in the crescentic class and urinary C3M levels highest in the focal class. Moreover, the urinary biomarkers were able to discriminate focal biopsy class from the other classes. Urinary DKK-3, EGF, PRO-C6 and C3M levels measured at the time of biopsy were also significantly related to the extent of fibrosis and to the final kidney function at the end of follow-up.

Conclusions

This small pilot study suggests that selected urinary biomarkers of fibrosis and inflammation may reflect changes in the kidney biopsy and be prognostic of kidney outcome in patients with AAV.

Extracellular Matrix (ECM) and Fibrosis in Adipose Tissue: Overview and Perspectives

Fibrosis in adipose tissue is a major driver of obesity-related metabolic dysregulation. It is characterized by an overaccumulation of extracellular matrix (ECM) during unhealthy expansion of adipose tissue in response to over nutrition. In obese adipose-depots, hypoxia stimulates multiple pro-fibrotic signaling pathways in different cell populations, thereby inducing the overproduction of the ECM components, including collagens, noncollagenous proteins, and additional enzymatic components of ECM synthesis. As a consequence, local fibrosis develops. The result of fibrosis-induced mechanical stress not only triggers cell necrosis and inflammation locally in adipose tissue but also leads to system-wide lipotoxicity and insulin resistance. A better understanding of the mechanisms underlying the obesity-induced fibrosis will help design therapeutic approaches to reduce or reverse the pathological changes associated with obese adipose tissue. Here, we aim to summarize the major advances in the field, which include newly identified fibrotic factors, cell populations that contribute to the fibrosis in adipose tissue, as well as novel mechanisms underlying the development of fibrosis. We further discuss the potential therapeutic strategies to target fibrosis in adipose tissue for the treatment of obesity-linked metabolic diseases and cancer. © 2023 American Physiological Society. Compr Physiol 13:4387-4407, 2023.

Extracellular matrix remodeling facilitates obesity-associated cancer progression

Obesity, a global public health concern, is an important risk factor for metabolic diseases and several cancers. Fibro-inflammation in adipose tissues (ATs) is tightly associated with the pathologies of obesity; excessive or uncontrolled extracellular matrix (ECM) production in AT has a crucial role in this pathogenesis. The ECM is a critical and functional component of various tissues, providing a mechanical and chemical network of proteins that controls cell survival, development, and tissue repair. The ECM is tightly regulated and dynamically remodeled; this is an important factor for AT expansion and can result in modifications to the physical shape and biological function of AT. Here, we focus on ECM remodeling in AT and how it affects obesity-related cancer progression.

MicroRNA-29 Ameliorates Fibro-Inflammation and Insulin Resistance in HIF1α-Deficient Obese Adipose Tissue by Inhibiting Endotrophin Generation

Dysregulation of extracellular matrix proteins in obese adipose tissue (AT) induces systemic insulin resistance. The metabolic roles of type VI collagen and its cleavage peptide endotrophin in obese AT are well established. However, the mechanisms regulating endotrophin generation remain elusive. Herein, we identified that several endotrophin-containing peptides (pre-endotrophins) were generated from the COL6A3 chain in a stepwise manner for the efficient production of mature endotrophin, partly through the action of hypoxia-induced matrix metalloproteinases (MMPs), including MMP2, MMP9, and MMP16. Hypoxia is an upstream regulator of COL6A3 expression and the proteolytic processing that regulates endotrophin generation. Hypoxia-inducible factor 1α (HIF1α) and the hypoxia-associated suppression of microRNA-29 (miR-29) cooperatively control the levels of COL6A3 and MMPs, which are responsible for endotrophin generation in hypoxic ATs. Adipocyte-specific Hif1α knock-out (APN-HIF1αKO) mice fed a chronic high-fat diet exhibited the significant amelioration of both local fibro-inflammation in AT and systemic insulin resistance compared with their control littermates, partly through the inhibition of endotrophin generation. Strikingly, adenovirus-mediated miR-29 overexpression in the ATs of APN-HIF1αKO mice in obesity significantly decreased endotrophin levels, suggesting that miR-29, combined with HIF1α inhibition in AT, could be a promising therapeutic strategy for treating obesity and related metabolic diseases.

meGPS: a multi-omics signature for hepatocellular carcinoma detection integrating methylome and transcriptome data

MOTIVATION

Hepatocellular carcinoma (HCC) is a primary malignancy with poor prognosis. Recently, multi-omics molecular-level measurement enables HCC diagnosis and prognosis prediction, which is crucial for early intervention of personalized therapy to diminish mortality. Here, we introduce a novel strategy utilizing DNA methylation and RNA expression data to achieve a multi-omics gene pair signature (GPS) for HCC discrimination.

RESULTS

The immune genes with negative correlations between expression and promoter methylation are enriched in the highly connected cancer-related pathway network, which are considered as the candidates for HCC detection. After that, we separately construct a methylation GPS (mGPS) and an expression GPS (eGPS), and then assemble them as a meGPS with five gene pairs, in which the significant methylation and expression changes occur between HCC tumor and non-tumor groups. Reliable performance has been validated by independent tissue (age, gender, and etiology) and blood datasets. This study proposes a procedure for multi-omics GPS identification and develops a novel HCC signature using both methylome and transcriptome data, suggesting potential molecular targets for the detection and therapy of HCC.

AVAILABILITY AND IMPLEMENTATION

Models are available at https://github.com/bioinformaticStudy/meGPS.git.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Biomarkers of extracellular matrix formation are associated with acute-on-chronic liver failure

Background & Aims

Acute-on-chronic liver failure (ACLF) is characterised by organ failure(s), high short-term mortality, and, pathophysiologically, deranged inflammatory responses. The extracellular matrix (ECM) is critically involved in regulating the inflammatory response. This study aimed to determine alterations in biomarkers of ECM turnover in ACLF and their association with inflammation, organ failures, and mortality.

Methods

We studied 283 patients with cirrhosis admitted for acute decompensation (AD) with or without ACLF, 64 patients with stable cirrhosis, and 30 healthy controls. A validation cohort (25 ACLF, 9 healthy controls) was included. Plasma PRO-C3, PRO-C4, PRO-C5, PRO-C6, and PRO-C8 (i.e. collagen type III–VI and VIII formation) and C4M and C6M (i.e. collagen type IV and VI degradation) were measured. Immunohistochemistry of PRO-C6 was performed on liver biopsies (AD [n = 7], ACLF [n = 5]). A competing-risk regression analysis was performed to explore the prognostic value of biomarkers of ECM turnover with 28- and 90-day mortality.

Results

PRO-C3 and PRO-C6 were increased in ACLF compared to AD (p = 0.089 and p <0.001, respectively), whereas collagen degradation markers C4M and C6M were similar. Both PRO-C3 and PRO-C6 were strongly associated with liver function and inflammatory markers. Only PRO-C6 was associated with extrahepatic organ failures and 28- and 90-day mortality (hazard ratio [HR; on log-scale] 6.168, 95% CI 2.366–16.080, p <0.001, and 3.495, 95% CI 1.509–8.093, p = 0.003, respectively). These findings were consistent in the validation cohort. High PRO-C6 expression was observed in liver biopsies of patients with ACLF.

Conclusions

This study shows, for the first time, evidence of severe net interstitial collagen deposition in ACLF and makes the novel observation of the association between PRO-C6 and (extrahepatic) organ failures and mortality. Further studies are needed to define the pathogenic significance of these observations.

Lay summary

This study describes a disrupted turnover of collagen type III and VI in Acute-on-chronic liver failure (ACLF). Plasma biomarkers of these collagens (PRO-C3 and PRO-C6) are associated with the severity of liver dysfunction and inflammation. PRO-C6, also known as the hormone endotrophin, has also been found to be associated with multi-organ failure and prognosis in acute decompensation and ACLF.

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Collagen type III and VI formation is increased in ACLF compared to AD.

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PRO-C3 and PRO-C6 correlate with the severity of liver dysfunction and inflammation in AD and ACLF.

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High PRO-C6 levels were found to be indicative for the presence of multi-organ failure and worse survival.

Considerations for understanding protein measurements: Identification of formation, degradation and more pathological relevant epitopes

OBJECTIVES

There is a need for precision medicine and an unspoken promise of an optimal approach for identification of the right patients for value-based medicine based on big data. However, there may be a misconception that measurement of proteins is more valuable than measurement of fewer selected biomarkers. In population-based research, variation may be somewhat eliminated by quantity. However, this fascination of numbers may limit the attention to and understanding of the single. This review highlights that protein measurements (with collagens as examples) may mean different things depending on the targeted epitope - formation or degradation of tissues, and even signaling potential of proteins.

DESIGN AND METHODS

PubMed was searched for collagen, neo-epitope, biomarkers.

RESULTS

Ample examples of assays with specific epitopes, either pathological such as HbA1c, or domain specific such as pro-peptides, which total protein arrays would not have identified were evident.

CONCLUSIONS

We suggest that big data may be considered as the funnel of data points, in which most important parameters will be selected. If the technical precision is low or the biological accuracy is limited, and we include suboptimal quality of biomarkers, disguised as big data, we may not be able to fulfill the promise of helping patients searching for the optimal treatment. Alternatively, if the technical precision of the total protein quantification is high, but we miss the functional domains with the most considerable biological meaning, we miss the most important and valuable information of a given protein. This review highlights that measurements of the same protein in different ways may provide completely different meanings. We need to understand the pathological importance of each epitope quantified to maximize protein measurements.

Collagen Type III and VI Remodeling Biomarkers Are Associated with Kidney Fibrosis in Lupus Nephritis

Background

Lupus nephritis (LN) occurs in <40% of patients with SLE. Reliable biomarkers of kidney damage are needed to identify patients with SLE at risk of developing LN to improve screening, treat the disease earlier, and halt progression to kidney failure. Novel biomarkers of extracellular matrix remodeling were evaluated as markers of kidney fibrosis and disease activity in patients with LN.

Methods

Biomarkers of the interstitial collagen type III (PRO-C3) and type VI (PRO-C6) formation and of collagen type III (C3M) degradation were evaluated in the serum and urine of 40 patients with LN, 20 patients with SLE but without LN, 20 healthy controls, and ten biopsy controls (histologic kidney inflammation/damage without SLE). Their association with histologic markers of interstitial fibrosis and tubular atrophy, with inflammatory cell infiltration and with disease activity and chronicity in the patients with LN was assessed.

Results

Despite PRO-C3 (serum) and PRO-C6 (serum and urine) being significantly elevated in patients with LN compared with healthy controls, the markers did not differentiate patients with LN from those with SLE. C3M (urine) levels were not different in LN compared with the other groups. C3M (urine) strongly correlated and PRO-C6 (serum and urine) inversely correlated with kidney function (eGFR). The biomarkers of interstitial collagen turnover PRO-C6 (serum) and C3M (urine) correlated with histologic markers of interstitial fibrosis, tubular atrophy, and monocyte infiltration.

Conclusions

Noninvasive collagen turnover biomarkers are promising tools to identify patients with SLE with kidney histologic modifications.

Collagen VI as a driver and disease biomarker in human fibrosis

Fibrosis of visceral organs such as the lungs, heart, kidneys and liver remains a major cause of morbidity and mortality and is also associated with many other disorders, including cancer and metabolic disease. In this review, we focus upon the microfibrillar collagen VI, which is present in the extracellular matrix (ECM) of most tissues. However, expression is elevated in numerous fibrotic conditions, such as idiopathic pulmonary disease (IPF), and chronic liver and kidney diseases. Collagen VI is composed of three subunits α1, α2 and α3, which can be replaced with alternate chains of α4, α5 or α6. The C-terminal globular domain (C5) of collagen VI α3 can be proteolytically cleaved to form a biologically active fragment termed endotrophin, which has been shown to actively drive fibrosis, inflammation and insulin resistance. Tissue biopsies have long been considered the gold standard for diagnosis and monitoring of progression of fibrotic disease. The identification of neoantigens from enzymatically processed collagen chains have revolutionised the biomarker field, allowing rapid diagnosis and evaluation of prognosis of numerous fibrotic conditions, as well as providing valuable clinical trial endpoint determinants. Collagen VI chain fragments such as endotrophin (PRO-C6), C6M and C6Mα3 are emerging as important biomarkers for fibrotic conditions.

Endotrophin is associated with chronic multimorbidity and all-cause mortality in a cohort of elderly women

BACKGROUND

The signalling peptide endotrophin is derived through proteolytic cleavage of the carboxyl-terminal during formation of type VI collagen. It is expressed by most descendants of the mesenchymal stem cells lineage, including adipocytes and fibroblasts, and have been proposed to be a central extracellular matrix hormone associated with several age-related diseases. We aimed to assess the association of endotrophin with chronic disease incidence and death in older women.

METHODS

5,602 elderly Danish women from the observational, prospective cohort: The Prospective Epidemiological Risk Factor (PERF) study were included in the analysis which covered baseline (BL) and follow-up (FU) 14 years later. An elastic net was used to investigate the relative importance of 58 variables to serum endotrophin-levels. 20 chronic diseases were defined on the basis of clinical variables available along with diagnoses extracted from both the National Patient Register, the National Diabetes Register and the Danish Cancer Registry. The cross-sectional associations between endotrophin-levels and these 17 chronic age-related diseases were investigated using logistic regression and a set-analysis explored disease-combinations within multimorbidity. The association of endotrophin with mortality was assessed by Cox proportional hazard models.

FINDINGS

Formation of type III collagen (PRO-C3), age and creatine-levels were the most influential variables of endotrophin-levels. Several chronic diseases were significantly associated with endotrophin-levels independent of age and BMI including chronic kidney disease (BL OR=3.7, p < 0.001; FU OR = 7.9 p < 0.001), diabetes (BL OR = 1.5, p = 0.0015, FU OR=1.6, p = 0.004) and peripheral arterial disease (BL OR = 1.3, p = 0.029; FU OR=2.4, p < 0.001). Lastly, endotrophin-levels were significantly rising with number of morbidities (p < 0.001) and a predictor of death after adjusting for age and BMI (BL HR=1.95; FU HR = 2.00).

INTERPRETATION

Endotrophin was associated with death and increased with number of morbidities. Endotrophin may be a central hormone of fibroblast that warrant investigation and possible targeted intervention in several chronic diseases.

FUNDING

The funder of the PERF study had no role in study design, data collection, data analysis, data interpretation, or writing of the report. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication.

Serum levels of endotrophin are associated with nonalcoholic steatohepatitis

BACKGROUND AND AIMS

There are no currently available biomarkers that can accurately indicate the presence of non-alcoholic steatohepatitis (NASH). We investigated the association between endotrophin, a cleavage product of collagen type 6α3, and disease severity in patients with non-alcoholic fatty liver disease (NAFLD).

METHODS

We measured serum endotrophin levels in 211 patients with NAFLD and nine healthy controls. Liver biopsy data was available for 141 (67%) of the patients. Associations between endotrophin and the presence of NASH and advanced fibrosis were investigated alone and in combination with standard clinical parameters using logistic regression.

RESULTS

A total of 211 patients were enrolled in this study, consisting of 108 (51%) men and 103 (49%) women with a mean age of 55.6 years. 58 (27%) of the patients had advanced fibrosis. Of those with biopsy data, 87 (62%) had NASH. Serum levels of endotrophin were significantly higher in patients with NAFLD than those in healthy controls (37[±12] vs. 17[±7] ng/mL, p<.001). Serum levels of endotrophin were also significantly higher in patients with NASH than in those without NASH (40[±12] vs. 32[±13] ng/mL, p<.001). A model using age, sex, body mass index and levels of alanine aminotransferase (ALT), glucose and endotrophin effectively predicted the presence of NASH in a derivation (AUROC 0.83, 95%CI = 0.74-0.92) and validation cohort (AUROC 0.71, 95%CI = 0.54-0.88). There was no significant association between serum levels of endotrophin and advanced fibrosis.

CONCLUSIONS

These data suggest that serum endotrophin could be a valuable biomarker for diagnosing NASH, but not for detecting advanced fibrosis in NAFLD.

Biomarker Identification for Liver Hepatocellular Carcinoma and Cholangiocarcinoma Based on Gene Regulatory Network Analysis

Background:

Liver hepatocellular carcinoma (LIHC) and cholangiocarcinoma (CHOL) are two main histological subtypes of primary liver cancer with a unified molecular landscape, and feed-forward loops (FFLs) have been shown to be relevant in these complex diseases.

Objective:

To date, there has been no comparative analysis of the pathogenesis of LIHC and CHOL based on regulatory relationships. Therefore, we investigated the common and distinct regulatory properties of LIHC and CHOL in terms of gene regulatory networks.

Method:

Based on identified FFLs and an analysis of pathway enrichment, we constructed pathway-specific co-expression networks and further predicted biomarkers for these cancers by network clustering.

Resul:

We identified 20 and 36 candidate genes for LIHC and CHOL, respectively. The literature from PubMed supports the reliability of our results.

Conclusion:

Our results indicated that the hsa01522-Endocrine resistance pathway was associated with both LIHC and CHOL. Additionally, six genes (SPARC, CTHRC1, COL4A1, EDIL3, LAMA4 and OLFML2B) were predicted to be highly associated with both cancers, and COL4A2, CSPG4, GJC1 and ADAMTS7 were predicted to be potential biomarkers of LIHC, and COL6A3, COL1A2, FAP and COL8A1 were predicted to be potential biomarkers of CHOL. In addition, we inferred that the Collagen gene family, which appeared more frequently in our overall prediction results, might be closely related to cancer development.

Extracellular Matrix Remodeling in Chronic Liver Disease

PURPOSE OF THE REVIEW

This review aims to summarize the current knowledge of the extracellular matrix remodeling during hepatic fibrosis. We discuss the diverse interactions of the extracellular matrix with hepatic cells and the surrounding matrix in liver fibrosis, with the focus on the molecular pathways and the mechanisms that regulate extracellular matrix remodeling.

RECENT FINDINGS

The extracellular matrix not only provides structure and support for the cells, but also controls cell behavior by providing adhesion signals and by acting as a reservoir of growth factors and cytokines.

SUMMARY

Hepatic fibrosis is characterized by an excessive accumulation of extracellular matrix. During fibrogenesis, the natural remodeling process of the extracellular matrix varies, resulting in the excessive accumulation of its components, mainly collagens. Signals released by the extracellular matrix induce the activation of hepatic stellate cells, which are the major source of extracellular matrix and most abundant myofibroblasts in the liver.

GRAPHICAL ABSTRACT

Endotrophin, a pro-peptide of Type VI collagen, is a biomarker of survival in cirrhotic patients with hepatocellular carcinoma

AIM

Type VI collagen, is emerging as a signaling collagen originating from different types of fibroblasts. A specific fragment of Type VI collagen, the pro-peptide, is also known as the hormone endotrophin. We hypothesized that this fibroblast hormone would be of particular relevance in cancer types with a high amount of fibrosis activity, namely for outcome in hepatocellular carcinoma (HCC) cirrhotic patients.

PATIENTS & METHODS

Plasma C6M, PRO-C6 and alphafeto-protein (AFP) were assessed in 309 patients with mixed etiologies (hepatitis C, hepatitis B, alcohol and nonalcoholic fatty liver) diagnosed as cirrhotics, cirrhotics with HCC, noncirrhotics and healthy controls. Progression-free survival and overall survival (OS) data were collected up to 6120 days after diagnosis. The ability of each marker to predict survival was investigated.

RESULTS & CONCLUSION

The level of endotrophin assessed by PRO-C6 was able to separate healthy controls, noncirrhotics and cirrhotics from HCC (p < 0.05-0.0001). Both endotrophin and C6M provided value in the prediction of OS in cirrhotic patients with HCC. In the multivariate analysis for identifying HCC, in patients with high endotrophin (highest quartile) and that were positive for AFP (≥20 IU/ml), the hazard ratio for predicting OS was increased from 3.7 (p = 0.0006) to 14.4 (p = 0.0001) when comparing with AFP positive as a stand-alone marker. In conclusion, plasma levels for markers of Type VI collagen remodeling were associated with survival in cirrhotic patients with HCC. A combination of AFP with endotrophin improved the prognostic value compared with AFP alone for predicting OS in cirrhotic patients with HCC.

The impact of endotrophin on the progression of chronic liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease and can lead to multiple complications, including non-alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. The fibrotic liver is characterized by the pathological accumulation of extracellular matrix (ECM) proteins. Type VI collagen alpha3 (Col6a3) is a biomarker of hepatic fibrosis, and its cleaved form, endotrophin (ETP), plays a critical role in adipose tissue dysfunction, insulin resistance, and breast cancer development. Here, we studied the effects of the Col6a3-derived peptide ETP on the progression of chronic liver diseases, such as NASH and liver cancer. We used a doxycycline (Dox)-inducible liver-specific ETP-overexpressing mouse model on a NAFLD-prone (liver-specific SREBP1a transgenic) background. For this, we evaluated the consequences of local ETP expression in the liver and its effect on hepatic inflammation, fibrosis, and insulin resistance. Accumulation of ETP in the liver induced hepatic inflammation and the development of fibrosis with associated insulin resistance. Surprisingly, ETP overexpression also led to the emergence of liver cancer within 10 months in the SREBP1a transgenic background. Our data revealed that ETP can act as a “second hit” during the progression of NAFLD and can play an important role in the development of NASH and hepatocellular carcinoma (HCC). These observations firmly link elevated levels of ETP to chronic liver disease.

Localized buildup in the liver of a collagen-derived cleavage fragment plays a critical role in accelerating the development of tissue scarring and liver cancer in mice. Using a transgenic mouse model of fatty liver disease, a team led by Philipp Scherer from the University of Texas Southwestern Medical Center, Dallas, USA, and Jiyoung Park of Ulsan National Institute of Science and Technology, South Korea, showed that liver-specific accumulation of a collagen fragment known as endotrophin leads to activation of inflammatory and fibrotic pathways. The mice subsequently develop metabolic dysfunction, insulin resistance and, with time, cancerous nodules in the liver. The findings suggest that endotrophin accumulation, when it occurs in liver tissue that already contains large depositions of fat, can overwhelm normal liver physiology and accelerate organ damage.

Identifying collagen VI as a target of fibrotic diseases regulated by CREBBP/EP300

Fibrotic diseases remain a major cause of morbidity and mortality, yet there are few effective therapies. The underlying pathology of all fibrotic conditions is the activity of myofibroblasts. Using cells from freshly excised disease tissue from patients with Dupuytren's disease (DD), a localized fibrotic disorder of the palm, we sought to identify new therapeutic targets for fibrotic disease. We hypothesized that the persistent activity of myofibroblasts in fibrotic diseases might involve epigenetic modifications. Using a validated genetics-led target prioritization algorithm (Pi) of genome wide association studies (GWAS) data and a broad screen of epigenetic inhibitors, we found that the acetyltransferase CREBBP/EP300 is a major regulator of contractility and extracellular matrix production via control of H3K27 acetylation at the profibrotic genes, ACTA2 and COL1A1 Genomic analysis revealed that EP300 is highly enriched at enhancers associated with genes involved in multiple profibrotic pathways, and broad transcriptomic and proteomic profiling of CREBBP/EP300 inhibition by the chemical probe SGC-CBP30 identified collagen VI (Col VI) as a prominent downstream regulator of myofibroblast activity. Targeted Col VI knockdown results in significant decrease in profibrotic functions, including myofibroblast contractile force, extracellular matrix (ECM) production, chemotaxis, and wound healing. Further evidence for Col VI as a major determinant of fibrosis is its abundant expression within Dupuytren's nodules and also in the fibrotic foci of idiopathic pulmonary fibrosis (IPF). Thus, Col VI may represent a tractable therapeutic target across a range of fibrotic disorders.

The fibrotic response of primary liver spheroids recapitulates in vivo hepatic stellate cell activation

A major obstacle in the development of efficient therapies for progressive liver fibrosis is the lack of representative in vitro models of liver fibrosis to aid in understanding the mechanisms of the disease and to promote the development of pharmaceuticals. Our aim was to develop a relevant in vitro mouse liver fibrosis model, based on the central hypothesis that liver fibrosis in vitro cannot be studied using only hepatic stellate cells (HSCs)-the main producer of scar tissue during fibrosis-, but requires cultures in which at least hepatocytes are integrated. We established robust methods to generate co-culture spheroids from freshly isolated mouse hepatocytes and HSCs. Characteristics and functionality of these spheroids were analyzed by qPCR of cell-type specific markers, CYP induction and immunohistochemistry. Compound toxicity was determined by ATP-assays. Hepatocytes and HSCs maintained their cell-type specific marker expression over a 15-day culture period without major hepatocyte dedifferentiation or HSC activation. Exposure of spheroids to TGFβ can directly activate HSCs, while acetaminophen exposure mounts a hepatocyte damage dependent activation of HSCs. Pharmaceuticals with known anti-fibrotic properties, such as Valproic acid and Verteporfin, reduce HSC activation in response to hepatocyte damage in these cultures. A comparison between the fibrotic response of the spheroid co-cultures and in vivo activated HSCs showed that these 3D co-cultures are more representative than the commonly used 2D HSC monocultures. Finally, we showed that the 3D cultures can be integrated in microfluidic chips. We conclude that our hepatocyte-stellate cell-spheroid cultures are a robust in vitro model of liver fibrosis. This model could be used to further unravel the mechanism of HSC activation and facilitate the discovery of, or testing for novel anti-fibrotic compounds, as these spheroids better reproduce HSC in vivo activation compared to the more traditional 2D mono-culture models.

Review article: the signalling and functional role of the extracellular matrix in the development of liver fibrosis

BACKGROUND

Patients with liver fibrosis show a large heterogeneity, and for that reason effective treatments are still lacking. Emerging data suggest that there is more to fibrosis than previously understood. Opposed to earlier belief of being a passive scaffold for cells to reside in, the extracellular matrix (ECM) is now known to hold both signalling and functional properties important for the development of fibrosis. The interaction between the ECM and the collagen-producing cells determines the course of the disease but is still poorly understood. Exploring the dynamics of this interplay will aid in the development of effective treatments.

AIM

To summarise and discuss the latest advances in the pathogenesis of liver fibrosis as well as key mediators of early disease progression.

METHODS

Through literature search using databases including PubMed and Google Scholar, manuscripts published between 1961 and 2019 were included to assess both well-established and recent theories of fibrosis development. Both pre-clinical and clinical studies were included.

RESULTS

Fibrosis alters the structure of the ECM releasing signalling fragments with the potential to escalate disease severity. In a diseased liver, hepatic stellate cells and other fibroblasts, together with hepatocytes and sinusoidal cells, produce an excessive amount of collagens. The cell-to-collagen interactions are unique in the different liver aetiologies, generating ECM profiles with considerable patient-monitoring potential.

CONCLUSIONS

The local milieu in the injured area affects the course of fibrosis development in a site-specific manner. Future research should focus on the dissimilarities in the ECM profile between different aetiologies of liver fibrosis.

The Biological Role of the Collagen Alpha-3 (VI) Chain and Its Cleaved C5 Domain Fragment Endotrophin in Cancer

The collagen alpha-3 (VI) chain encoded by the gene COL6A3 is one of the 3 subunits of collagen VI which is a microfibrillar component of the extracellular matrix and is essential for the stable assembly process of collagen VI. The collagen alpha-3 (VI) chain and the cleaved C5 domain fragment, called endotrophin, are highly expressed in a variety of cancers and play a crucial role in cancer progression. The biological functions of endotrophin in tumors can be driven by adipocytes. Studies have demonstrated that endotrophin can directly affect the malignancy of cancer cells through TGF-β-dependent mechanisms, inducing epithelial–mesenchymal transition and fibrosis of the tumor microenvironment. In addition, endotrophin can also recruit macrophages and endothelial cells through chemotaxis to regulate the tumor microenvironment and ultimately promote tumor inflammation and angiogenesis. Furthermore, COL6A3 and endotrophin serve as novel diagnostic and prognostic biomarkers in cancer and contribute to clinical therapeutic applications in the future. In summary, in this review, we discuss the importance of the collagen alpha-3 (VI) chain and endotrophin in cancer progression, the future clinical applications of endotrophin and the remaining challenges in this field.

Critical Role of Matrix Metalloproteinase 14 in Adipose Tissue Remodeling during Obesity

Fibrosis is recognized as the major pathological change in adipose tissue during the development of obesity. However, the detailed mechanisms governing the interactions between the fibrotic components and their modifiers remain largely unclear. Here, we reported that matrix metalloproteinase 14 (MMP14), a key pericellular collagenase, is dramatically upregulated in obese adipose tissue. We generated a doxycycline-inducible adipose tissue-specific MMP14 overexpression model to study its regulatory function. We found that overexpression of MMP14 in the established obese adipose tissue leads to enlarged adipocytes and increased body weights in transgenic mice. Furthermore, the mice exhibited decreased energy expenditure, impaired lipid metabolism, and insulin resistance. Mechanistically, we found that MMP14 digests collagen 6α3 to produce endotrophin, a potent costimulator of fibrosis and inflammation. Unexpectedly, when overexpressing MMP14 in the early-stage obese adipose tissue, the transgenic mice showed a healthier metabolic profile, including ameliorated fibrosis and inflammation, as well as improved lipid and glucose metabolism. This unique metabolic phenotype is likely due to digestion/modification of the dense adipose tissue extracellular matrix by MMP14, thereby releasing the mechanical stress to allow for its healthy expansion. Understanding these dichotomous impacts of MMP14 provides novel insights into strategies to treat obesity-related metabolic disorders.

Beyond adiponectin and leptin: adipose tissue-derived mediators of inter-organ communication

The breakthrough discoveries of leptin and adiponectin more than two decades ago led to a widespread recognition of adipose tissue as an endocrine organ. Many more adipose tissue-secreted signaling mediators (adipokines) have been identified since then, and much has been learned about how adipose tissue communicates with other organs of the body to maintain systemic homeostasis. Beyond proteins, additional factors, such as lipids, metabolites, noncoding RNAs, and extracellular vesicles (EVs), released by adipose tissue participate in this process. Here, we review the diverse signaling mediators and mechanisms adipose tissue utilizes to relay information to other organs. We discuss recently identified adipokines (proteins, lipids, and metabolites) and briefly outline the contributions of noncoding RNAs and EVs to the ever-increasing complexities of adipose tissue inter-organ communication. We conclude by reflecting on central aspects of adipokine biology, namely, the contribution of distinct adipose tissue depots and cell types to adipokine secretion, the phenomenon of adipokine resistance, and the capacity of adipose tissue to act both as a source and sink of signaling mediators.

C-terminal proteolysis of the collagen VI α3 chain by BMP-1 and proprotein convertase(s) releases endotrophin in fragments of different sizes

The assembly of collagen VI microfibrils is a multistep process in which proteolytic processing within the C-terminal globular region of the collagen VI α3 chain plays a major role. However, the mechanisms involved remain elusive. Moreover, C5, the short and most C-terminal domain of the α3 chain, recently has been proposed to be released as an adipokine that enhances tumor progression, fibrosis, inflammation, and insulin resistance and has been named "endotrophin." Serum endotrophin could be a useful biomarker to monitor the progression of such disorders as chronic obstructive pulmonary disease, systemic sclerosis, and kidney diseases. Here, using biochemical and isotopic MS-based analyses, we found that the extracellular metalloproteinase bone morphogenetic protein 1 (BMP-1) is involved in endotrophin release and determined the exact BMP-1 cleavage site. Moreover, we provide evidence that several endotrophin-containing fragments are present in various tissues and body fluids. Among these, a large C2-C5 fragment, which contained endotrophin, was released by furin-like proprotein convertase cleavage. By using immunofluorescence microscopy and EM, we also demonstrate that these proteolytic maturations occur after secretion of collagen VI tetramers and during microfibril assembly. Differential localization of N- and C-terminal regions of the collagen VI α3 chain revealed that cleavage products are deposited in tissue and cell cultures. The detailed information on the processing of the collagen VI α3 chain reported here provides a basis for unraveling the function of endotrophin (C5) and larger endotrophin-containing fragments and for refining their use as biomarkers of disease progression.