Latent transforming growth factor beta-binding protein 1 interacts with fibrillin and is a microfibril-associated protein

Geleophysic dysplasia and Weill-Marchesani syndrome: ADAMTSL2 a possible common gene

BACKGROUND

Geleophysic dysplasia (GD) and Weill-Marchesani syndrome (WMS) are two rare genetic disorders that are classified as acromelic dysplasias and have many common features that overlap clinically and genetically in some patients. Both diseases are characterized by acromelic features, including short stature, brachydactyly, joint limitations, and cardiac involvement. WMS is distinguished from GD mainly by ocular abnormalities, including high myopia, microspherophakia, ectopia lentis, and glaucoma and the absence of the life-threatening airway stenosis and early lethality. These two syndromes are allelic diseases of the FBN1 gene, with the gene families including A Disintegrin and Metalloproteinase with Thrombospondin motifs (ADAMTS) and latent transforming growth factor-beta-binding protein (LTBP). Although the ADAMTSL2 gene has been associated only with GD within the acromelic dysplasias, there have been reports of patients with ADAMTSL2-related GD exhibiting ocular abnormalities that resemble WMS.

METHODS AND RESULTS

We present a 24-year-old female patient with microspherophakia, ectopia lentis, myopia, short stature, joint stiffness, thick skin, short hands and feet, and cardiac valve disease consistent with WMS. The virtual panel analysis, including WMS and GD-related genes, revealed a homozygous c.493 G>A (p.Ala165Thr) variant in the ADAMTSL2 gene (NM_014694.4), which has been previously reported in a geleophysic dysplasia patient.

CONCLUSIONS

Mounting evidence suggests that GD and WMS may be allelic diseases of the ADAMTSL2 gene.

Changes in the Transcriptome and Long Non-Coding RNAs but Not the Methylome Occur in Human Cells Exposed to Borrelia burgdorferi

Lyme disease, caused by infection with members of the Lyme borreliosis group of Borrelia spirochete bacteria, is increasing in frequency and distribution worldwide. Epigenetic interactions between the mammalian host, tick, and bacterial pathogen are poorly understood. In this study, high-throughput next-generation sequencing (NGS) allowed for the in vitro study of the transcriptome, non-coding RNAs, and methylome in human host cells in response to Borrelia burgdorferi infection. We tested the effect of the Borrelia burgdorferi strain B31 on a human primary cell line (HUVEC) and an immortalized cell line (HEK-293) for 72 h, a long-duration time that might allow for epigenetic responses in the exposed human host cells. Differential gene expression was detected in both cell models in response to B. burgdorferi. More differentially expressed genes were found in HUVECs compared to HEK-293 cells. Borrelia burgdorferi exposure significantly induced genes in the interferon, in addition to cytokine and other immune response signaling in HUVECs. In HEK-293 cells, pre-NOTCH processing in Golgi was significantly downregulated in Borrelia-exposed cells. Other significantly altered gene expressions were found in genes involved in the extracellular matrix. No significant global methylation changes were detected in HUVECs or HEK-293 cells exposed to B. burgdorferi; however, two long non-coding RNAs and a pseudogene were deregulated in response to B. burgdorferi in HUVECs, suggesting that other epigenetic mechanisms may be initiated by infection.

Proteomic profiling of the extracellular matrix in the human adrenal cortex

The extracellular matrix (ECM) comprises macromolecules that shape a complex three-dimensional network. Filling the intercellular space and playing a crucial role in the structure and function of tissues, ECM regulates essential cellular processes such as adhesion, differentiation, and cell signaling. In the human adrenal gland, composed of cortex and medulla surrounded by a capsule, the ECM has not yet been directly described, although its impact on the processes of proliferation and steroidogenesis of the adrenal cortex is recognized. This study analyzes the ECM of the adult human adrenal cortex, which was separated into outer fraction (OF) and inner fraction (IF), by comparing their proteomic profiles. The study discusses the composition, spatial distribution, and relevance of differentially expressed ECM signatures of the adrenal cortex matrisome on adrenal structure and function. The findings were validated through database analysis (cross-validation), histochemical, and immunohistochemical approaches. A total of 121 ECM proteins were identified and categorized into glycoproteins, collagens, ECM regulators, proteoglycans, ECM-affiliated proteins, and secreted factors. Thirty-one ECM proteins were identified only in OF, nine only in IF, and 81 were identified in common with both fractions. Additionally, 106 ECM proteins were reported in the Human matrisome DB 2.0, and the proteins differentially expressed in OF and IF, were identified. This study provides significant insights into the composition and regulation of the ECM in the human adrenal cortex, shedding light on the adrenal microenvironment and its role in the functioning, maintenance, and renewal of the adrenal gland.

Molecular force-induced liberation of transforming growth factor-beta remodels the spleen for ectopic liver regeneration

BACKGROUND & AIMS

Ectopic liver regeneration in the spleen is a promising alternative to organ transplantation for treating liver failure. To accommodate transplanted liver cells, the splenic tissue must undergo structural changes to increase extracellular matrix content, demanding a safe and efficient approach for tissue remodelling.

METHODS

We synthesised sulphated hyaluronic acid (sHA) with an affinity for the latent complex of transforming growth factor-β (TGF-β) and cross-linked it into a gel network (sHA-X) via click chemistry. We injected this glycan into the spleens of mice to induce splenic tissue remodelling via supraphysiological activation of endogenous TGF-β.

RESULTS

sHA-X efficiently bound to the abundant latent TGF-β in the spleen. It provided the molecular force to liberate the active TGF-β dimers from their latent complex, mimicking the 'bind-and-pull' mechanism required for physiological activation of TGF-β and reshaping the splenic tissue to support liver cell growth. Hepatocytes transplanted into the remodelled spleen developed into liver tissue with sufficient volume to rescue animals with a metabolic liver disorder (Fah-/- transgenic model) or following 90% hepatectomy, with no adverse effects observed and no additional drugs required.

CONCLUSION

Our findings highlight the efficacy and translational potential of using sHA-X to remodel a specific organ by mechanically activating one single cytokine, representing a novel strategy for the design of biomaterials-based therapies for organ regeneration.

IMPACT AND IMPLICATIONS

Cell transplantation may provide a lifeline to millions of patients with end-stage liver diseases, but their severely damaged livers being unable to accommodate the transplanted cells is a crucial hurdle. Herein, we report an approach to restore liver functions in another organ - the spleen - by activating one single growth factor in situ. This approach, based on a chemically designed polysaccharide that can mechanically liberate the active transforming growth factor-β to an unusually high level, promotes the function of abundant allogenic liver cells in the spleen, rescuing animals from lethal models of liver diseases and showing a high potential for clinical translation.

Functional diversity of apoptotic vesicle subpopulations from bone marrow mesenchymal stem cells in tissue regeneration

Apoptosis releases numerous apoptotic vesicles that regulate processes such as cell proliferation, immunity, and tissue regeneration and repair. Now, it has also emerged as an attractive candidate for biotherapeutics. However, apoptotic vesicles encompass a diverse range of subtypes, and it remains unclear which specific subtypes play a pivotal role. In this study, we successfully isolated different apoptotic vesicle subtypes based on their sizes and characterized them using NTA and TEM techniques, respectively. We compared the functional variances among the distinct subtypes of apoptotic vesicles in terms of stem cell proliferation, migration, and differentiation, as well as for endothelial cell and macrophage function, effectively identifying subtypes that exhibit discernible functional differences. ApoSEV (with diameter <1000 nm) promoted stem cell proliferation, migration, and multi-potent differentiation, and accelerated skin wound healing of diabetes mouse model, while apoBD (with diameter >1000 nm) played the opposite effect on cell function and tissue regeneration. Lastly, employing protein analysis and gene sequencing techniques, we elucidated the intrinsic mechanisms underlying these differences between different subtypes of apoEVs. Collectively, this study identified that apoptotic vesicle subtypes possessed distinct bio-functions in regulating stem cell function and behaviour and modulating tissue regeneration, which primarily attribute to the distinct profiling of protein and mRNA in different subtypes. This comprehensive analysis of specific subtypes of apoEVs would provide novel insights for potential therapeutic applications in cell biology and tissue regeneration.

Exploring the mechanisms behind autologous lipotransfer for radiation-induced fibrosis: A systematic review

AIM

Radiation-induced fibrosis is a recognised consequence of radiotherapy, especially after multiple and prolonged dosing regimens. There is no definitive treatment for late-stage radiation-induced fibrosis, although the use of autologous fat transfer has shown promise. However, the exact mechanisms by which this improves radiation-induced fibrosis remain poorly understood. We aim to explore existing literature on the effects of autologous fat transfer on both in-vitro and in-vivo radiation-induced fibrosis models, and to collate potential mechanisms of action.

METHOD

PubMed, Cochrane reviews and Scopus electronic databases from inception to May 2023 were searched. Our search strategy combined both free-text terms with Boolean operators, derived from synonyms of adipose tissue and radiation-induced fibrosis.

RESULTS

The search strategy produced 2909 articles. Of these, 90 underwent full-text review for eligibility, yielding 31 for final analysis. Nine conducted in-vitro experiments utilising a co-culture model, whilst 25 conducted in-vivo experiments. Interventions under autologous fat transfer included adipose-derived stem cells, stromal vascular function, whole fat and microfat. Notable findings include downregulation of fibroblast proliferation, collagen deposition, epithelial cell apoptosis, and proinflammatory processes. Autologous fat transfer suppressed hypoxia and pro-inflammatory interferon-γ signalling pathways, and tissue treated with adipose-derived stem cells stained strongly for anti-inflammatory M2 macrophages. Although largely proangiogenic initially, studies show varying effects on vascularisation. There is early evidence that adipose-derived stem cell subgroups may have different functional properties.

CONCLUSION

Autologous fat transfer functions through pro-angiogenic, anti-fibrotic, immunomodulatory, and extracellular matrix remodelling properties. By characterising these mechanisms, relevant drug targets can be identified and used to further improve clinical outcomes in radiation-induced fibrosis. Further research should focus on adipose-derived stem cell sub-populations and augmentation techniques such as cell-assisted lipotransfer.

The extracellular matrix glycoprotein fibrillin-1 in health and disease

Fibrillin-1 (FBN1) is a large, cysteine-rich, calcium binding extracellular matrix glycoprotein encoded by FBN1 gene. It serves as a structural component of microfibrils and provides force-bearing mechanical support in elastic and nonelastic connective tissue. As such, mutations in the FBN1 gene can cause a wide variety of genetic diseases such as Marfan syndrome, an autosomal dominant disorder characterized by ocular, skeletal and cardiovascular abnormalities. FBN1 also interacts with numerous microfibril-associated proteins, growth factors and cell membrane receptors, thereby mediating a wide range of biological processes such as cell survival, proliferation, migration and differentiation. Dysregulation of FBN1 is involved in the pathogenesis of many human diseases, such as cancers, cardiovascular disorders and kidney diseases. Paradoxically, both depletion and overexpression of FBN1 upregulate the bioavailability and signal transduction of TGF-β via distinct mechanisms in different settings. In this review, we summarize the structure and expression of FBN1 and present our current understanding of the functional role of FBN1 in various human diseases. This knowledge will allow to develop better strategies for therapeutic intervention of FBN1 related diseases.

Genetic models of fibrillinopathies

The fibrillinopathies represent a group of diseases in which the 10-12 nm extracellular microfibrils are disrupted by genetic variants in one of the genes encoding fibrillin molecules, large glycoproteins of the extracellular matrix. The best-known fibrillinopathy is Marfan syndrome, an autosomal dominant condition affecting the cardiovascular, ocular, skeletal, and other systems, with a prevalence of around 1 in 3,000 across all ethnic groups. It is caused by variants of the FBN1 gene, encoding fibrillin-1, which interacts with elastin to provide strength and elasticity to connective tissues. A number of mouse models have been created in an attempt to replicate the human phenotype, although all have limitations. There are also natural bovine models and engineered models in pig and rabbit. Variants in FBN2 encoding fibrillin-2 cause congenital contractural arachnodactyly and mouse models for this condition have also been produced. In most animals, including birds, reptiles, and amphibians, there is a third fibrillin, fibrillin-3 (FBN3 gene) for which the creation of models has been difficult as the gene is degenerate and nonfunctional in mice and rats. Other eukaryotes such as the nematode C. elegans and zebrafish D. rerio have a gene with some homology to fibrillins and models have been used to discover more about the function of this family of proteins. This review looks at the phenotype, inheritance, and relevance of the various animal models for the different fibrillinopathies.

Proteomic analysis reveals activation of platelet- and fibrosis-related pathways in hearts of ApoE-/- mice exposed to diesel exhaust particles

Air pollution is an environmental risk factor linked to multiple human diseases including cardiovascular diseases (CVDs). While particulate matter (PM) emitted by diesel exhaust damages multiple organ systems, heart disease is one of the most severe pathologies affected by PM. However, the in vivo effects of diesel exhaust particles (DEP) on the heart and the molecular mechanisms of DEP-induced heart dysfunction have not been investigated. In the current study, we attempted to identify the proteomic signatures of heart fibrosis caused by diesel exhaust particles (DEP) in CVDs-prone apolipoprotein E knockout (ApoE-/-) mice model using tandem mass tag (TMT)-based quantitative proteomic analysis. DEP exposure induced mild heart fibrosis in ApoE-/- mice compared with severe heart fibrosis in ApoE-/- mice that were treated with CVDs-inducing peptide, angiotensin II. TMT-based quantitative proteomic analysis of heart tissues between PBS- and DEP-treated ApoE-/- mice revealed significant upregulation of proteins associated with platelet activation and TGFβ-dependent pathways. Our data suggest that DEP exposure could induce heart fibrosis, potentially via platelet-related pathways and TGFβ induction, causing cardiac fibrosis and dysfunction.

Unraveling the role of TGFβ signaling in thoracic aortic aneurysm and dissection using Fbn1 mutant mouse models

Although abnormal TGFβ signaling is observed in several heritable forms of thoracic aortic aneurysms and dissections including Marfan syndrome, its precise role in aortic disease progression is still disputed. Using a mouse genetic approach and quantitative isobaric labeling proteomics, we sought to elucidate the role of TGFβ signaling in three Fbn1 mutant mouse models representing a range of aortic disease from microdissection (without aneurysm) to aneurysm (without rupture) to aneurysm and rupture. Results indicated that reduced TGFβ signaling and increased mast cell proteases were associated with microdissection. In contrast, increased abundance of extracellular matrix proteins, which could be reporters for positive TGFβ signaling, were associated with aneurysm. Marked reductions in collagens and fibrillins, and increased TGFβ signaling, were associated with aortic rupture. Our data indicate that TGFβ signaling performs context-dependent roles in the pathogenesis of thoracic aortic disease.

FBN1 knockout promotes cervical artery dissection by inducing N-glycosylation alternation of extracellular matrix proteins in rat VSMCs

FBN1 mutation promotes the degeneration of microfibril structures and extracellular matrix (ECM) integrity in the tunica media of the aorta in Marfan syndrome. However, whether FBN1 modulates cervical artery dissection (CAD) development and the potential molecular mechanisms of abnormal FBN1 in CAD remains elusive. In this study, FBN1 deficiency participated in the development of CAD and influenced the proliferation, apoptosis, and migration of vascular smooth muscle cells. FBN1 knockout induced alternations in mRNA levels of the transcriptome, protein expression of the proteome, and abundance of N-glycosylation of the N-glycoproteome. Comprehensive analysis of multiple omics showed up-regulation in mRNA levels of ECM proteins; yet, both the ECM protein levels and relative abundance of N-glycosylation were decreased. Moreover, we performed in vivo experiments to confirm the altered glycosylation of proteins in vascular smooth muscle cells. In conclusion, FBN1 deletion in vascular smooth muscle cells can result in altered N-glycosylation of ECM protein, which were critical for the stability of ECM and the process of CAD. This may open the way for a novel therapeutic strategy to treat people with CAD.

Marfan Syndrome: Enhanced Diagnostic Tools and Follow-up Management Strategies

Marfan syndrome (MFS) is a rare inherited autosomic disorder, which encompasses a variety of systemic manifestations caused by mutations in the Fibrillin-1 encoding gene (FBN1). Cardinal clinical phenotypes of MFS are highly variable in terms of severity, and commonly involve cardiovascular, ocular, and musculoskeletal systems with a wide range of manifestations, such as ascending aorta aneurysms and dissection, mitral valve prolapse, ectopia lentis and long bone overgrowth, respectively. Of note, an accurate and prompt diagnosis is pivotal in order to provide the best treatment to the patients as early as possible. To date, the diagnosis of the syndrome has relied upon a systemic score calculation as well as DNA mutation identification. The aim of this review is to summarize the latest MFS evidence regarding the definition, differences and similarities with other connective tissue pathologies with severe systemic phenotypes (e.g., Autosomal dominant Weill-Marchesani syndrome, Loeys-Dietz syndrome, Ehlers-Danlos syndrome) and clinical assessment. In this regard, the management of MFS requires a multidisciplinary team in order to accurately control the evolution of the most severe and potentially life-threatening complications. Based on recent findings in the literature and our clinical experience, we propose a multidisciplinary approach involving specialists in different clinical fields (i.e., cardiologists, surgeons, ophthalmologists, orthopedics, pneumologists, neurologists, endocrinologists, geneticists, and psychologists) to comprehensively characterize, treat, and manage MFS patients with a personalized medicine approach.

Collagen type VI regulates TGFβ bioavailability in skeletal muscle

Collagen VI-related disorders (COL6-RDs) are a group of rare muscular dystrophies caused by pathogenic variants in collagen VI genes (COL6A1, COL6A2, and COL6A3). Collagen type VI is a heterotrimeric, microfibrillar component of the muscle extracellular matrix (ECM), predominantly secreted by resident fibroadipogenic precursor cells in skeletal muscle. The absence or mislocalizatoion of collagen VI in the ECM underlies the non-cell autonomous dysfunction and dystrophic changes in skeletal muscle with an as of yet elusive direct mechanistic link between the ECM and myofiber dysfunction. Here, we conduct a comprehensive natural history and outcome study in a novel mouse model of COL6-RDs (Col6a2-/- mice) using standardized (Treat-NMD) functional, histological, and physiologic parameter. Notably, we identify a conspicuous dysregulation of the TGFβ pathway early in the disease process and propose that the collagen VI deficient matrix is not capable of regulating the dynamic TGFβ bioavailability at baseline and also in response to muscle injury. Thus, we propose a new mechanism for pathogenesis of the disease that links the ECM regulation of TGFβ with downstream skeletal muscle abnormalities, paving the way for developing and validating therapeutics that target this pathway.

Biology of mitral valve prolapse: from general mechanisms to advanced molecular patterns-a narrative review

Mitral valve prolapse (MVP) represents the most frequent cause of primary mitral regurgitation. For several years, biological mechanisms underlying this condition attracted the attention of investigators, trying to identify the pathways responsible for such a peculiar condition. In the last ten years, cardiovascular research has moved from general biological mechanisms to altered molecular pathways activation. Overexpression of TGF-β signaling, for instance, was shown to play a key role in MVP, while angiotensin-II receptor blockade was found to limit MVP progression by acting on the same signaling pathway. Concerning extracellular matrix organization, the increased valvular interstitial cells density and dysregulated production of catalytic enzymes (matrix metalloproteinases above all) altering the homeostasis between collagen, elastin and proteoglycan components, have been shown to possibly provide a mechanistic basis contributing to the myxomatous MVP phenotype. Moreover, it has been observed that high levels of osteoprotegerin may contribute to the pathogenesis of MVP by increasing collagen deposition in degenerated mitral leaflets. Although MVP is believed to represent the result of multiple genetic pathways alterations, it is important to distinguish between syndromic and non-syndromic conditions. In the first case, such as in Marfan syndrome, the role of specific genes has been clearly identified, while in the latter a progressively increasing number of genetic loci have been thoroughly investigated. Moreover, genomics is gaining more interest as potential disease-causing genes and loci possibly associated with MVP progression and severity have been identified. Animal models could be of help in better understanding the molecular basis of MVP, possibly providing sufficient information to tackle specific mechanisms aimed at slowing down MVP progression, therefore developing non-surgical therapies impacting on the natural history of this condition. Although continuous progress has been made in this field, further translational studies are advocated to improve our knowledge of biological mechanisms underlying MVP development and progression.

Nanoscale Structural Comparison of Fibrillin-1 Microfibrils Isolated from Marfan and Non-Marfan Syndrome Human Aorta

Fibrillin-1 microfibrils are essential elements of the extracellular matrix serving as a scaffold for the deposition of elastin and endowing connective tissues with tensile strength and elasticity. Mutations in the fibrillin-1 gene (FBN1) are linked to Marfan syndrome (MFS), a systemic connective tissue disorder that, besides other heterogeneous symptoms, usually manifests in life-threatening aortic complications. The aortic involvement may be explained by a dysregulation of microfibrillar function and, conceivably, alterations in the microfibrils' supramolecular structure. Here, we present a nanoscale structural characterization of fibrillin-1 microfibrils isolated from two human aortic samples with different FBN1 gene mutations by using atomic force microscopy, and their comparison with microfibrillar assemblies purified from four non-MFS human aortic samples. Fibrillin-1 microfibrils displayed a characteristic "beads-on-a-string" appearance. The microfibrillar assemblies were investigated for bead geometry (height, length, and width), interbead region height, and periodicity. MFS fibrillin-1 microfibrils had a slightly higher mean bead height, but the bead length and width, as well as the interbead height, were significantly smaller in the MFS group. The mean periodicity varied around 50-52 nm among samples. The data suggest an overall thinner and presumably more frail structure for the MFS fibrillin-1 microfibrils, which may play a role in the development of MFS-related aortic symptomatology.

Fibrillin microfibril structure identifies long-range effects of inherited pathogenic mutations affecting a key regulatory latent TGFβ-binding site

Genetic mutations in fibrillin microfibrils cause serious inherited diseases, such as Marfan syndrome and Weill-Marchesani syndrome (WMS). These diseases typically show major dysregulation of tissue development and growth, particularly in skeletal long bones, but links between the mutations and the diseases are unknown. Here we describe a detailed structural analysis of native fibrillin microfibrils from mammalian tissue by cryogenic electron microscopy. The major bead region showed pseudo eightfold symmetry where the amino and carboxy termini reside. On the basis of this structure, we show that a WMS deletion mutation leads to the induction of a structural rearrangement that blocks interaction with latent TGFβ-binding protein-1 at a remote site. Separate deletion of this binding site resulted in the assembly of shorter fibrillin microfibrils with structural alterations. The integrin α_vβ₃-binding site was also mapped onto the microfibril structure. These results establish that in complex extracellular assemblies, such as fibrillin microfibrils, mutations may have long-range structural consequences leading to the disruption of growth factor signaling and the development of disease.

Correlation between large FBN1 deletions and severe cardiovascular phenotype in Marfan syndrome: Analysis of two novel cases and analytical review of the literature

BACKGROUND

Marfan syndrome (MFS) is a clinically heterogeneous hereditary connective tissue disorder. Severe cardiovascular manifestations (i.e., aortic aneurysm and dissection) are the most life-threatening complications. Most of the cases are caused by mutations, a minor group of which are copy number variations (CNV), in the FBN1 gene.

METHODS

Multiplex ligation-dependent probe amplification test was performed to detect CNVs in 41 MFS patients not carrying disease-causing mutations in FBN1 gene. Moreover, the association was analyzed between the localization of CNVs, the affected regulatory elements and the cardiovascular phenotypes among all cases known from the literature.

RESULTS

A large two-exon deletion (exon 46 and 47) was identified in two related patients, which was associated with a mild form of cardiovascular phenotype. Severe cardiovascular symptoms were found significantly more frequent in patients with FBN1 large deletion compared to our patients with intragenic small scale FBN1 mutation. Bioinformatic data analyses of regulatory elements located within the FBN1 gene revealed an association between the deletion of STAT3 transcription factor-binding site and cardiovascular symptoms in five out of 25 patients.

CONCLUSION

Our study demonstrated that large CNVs are often associated with severe cardiovascular manifestations in MFS and the localization of these CNVs affect the phenotype severity.

Recent progress in the manipulation of biochemical and biophysical cues for engineering functional tissues

Tissue engineering (TE) is currently considered a cutting-edge discipline that offers the potential for developing treatments for health conditions that negatively affect the quality of life. This interdisciplinary field typically involves the combination of cells, scaffolds, and appropriate induction factors for the regeneration and repair of damaged tissue. Cell fate decisions, such as survival, proliferation, or differentiation, critically depend on various biochemical and biophysical factors provided by the extracellular environment during developmental, physiological, and pathological processes. Therefore, understanding the mechanisms of action of these factors is critical to accurately mimic the complex architecture of the extracellular environment of living tissues and improve the efficiency of TE approaches. In this review, we recapitulate the effects that biochemical and biophysical induction factors have on various aspects of cell fate. While the role of biochemical factors, such as growth factors, small molecules, extracellular matrix (ECM) components, and cytokines, has been extensively studied in the context of TE applications, it is only recently that we have begun to understand the effects of biophysical signals such as surface topography, mechanical, and electrical signals. These biophysical cues could provide a more robust set of stimuli to manipulate cell signaling pathways during the formation of the engineered tissue. Furthermore, the simultaneous application of different types of signals appears to elicit synergistic responses that are likely to improve functional outcomes, which could help translate results into successful clinical therapies in the future.

No differences in FBN1 genotype between men with and without abdominal aortic aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA) is an aortic enlargement in which the transverse diameter reaches at least 30 mm. Certain risk factors, such as age, male gender, and smoking, are well known; however, less is known about the genetic factors involved. Fibrillin-1 (FBN1) is a protein that coordinates the deposition of elastin fibres in the extracellular matrix and is therefore likely to affect the elastic properties in the aortic wall. Previously studies have found associations between the FBN1-2/3 genotype and arterial stiffness, but how different FBN1 genotypes, AAA, and arterial stiffness are related has been less frequently investigated.

AIM

This study aimed to investigate whether there is a difference in FBN1 genotype between men with and without AAA. A further aim was to study whether the FBN1 genotype affects arterial wall stiffness differently in men with and without AAA.

METHODS

Pulse wave velocity and FBN1 genotyping were performed in 229 men (159 with AAA, 70 without AAA). Participants were recruited from ultrasound AAA surveillance programs or ongoing ultrasound screening programs from 2011 to 2016.

RESULTS

The distribution of the FBN1 genotype in the AAA and control groups were as follows: FBN1-2/2: 62% vs. 64%; FBN1-2/3: 8% vs. 14%; and FBN1-2/4: 30% vs. 21%, respectively. Men with AAA and FBN1-2/2 had increased central pulse wave velocity (p < 0.005) compared to the control group (those without AAA) with the FBN1-2/2 genotype.

CONCLUSION

No differences were found with respect to FBN1 genotypes between men with and without AAA. The development of AAA in men does not appear to be linked to a specific FBN1 genotype. Nevertheless, men with FBN1-2/2 and AAA have increased central arterial stiffness compared to men with the same FBN1 genotype but without AAA.

Fibrillin-1 and asprosin, novel players in metabolic syndrome

Fibrillin-1 is a major component of the extracellular microfibrils, where it interacts with other extracellular matrix proteins to provide elasticity to connective tissues, and regulates the bioavailability of TGFβ family members. A peptide consisting of the C-terminal 140 amino acids of fibrillin-1 has recently been identified as a glucogenic hormone, secreted from adipose tissue during fasting and targeting the liver to release glucose. This fragment, called asprosin, also signals in the hypothalamus to stimulate appetite. Asprosin levels are correlated with many of the pathologies indicative of metabolic syndrome, including insulin resistance and obesity. Previous studies and reviews have addressed the therapeutic potential of asprosin as a target in obesity, diabetes and related conditions without considering mechanisms underlying the relationship between generation of asprosin and expression of the much larger fibrillin-1 protein. Profibrillin-1 undergoes obligatory cleavage at the cell surface as part of its assembly into microfibrils, producing the asprosin peptide as well as mature fibrillin-1. Patterns of FBN1 mRNA expression are inconsistent with the necessity for regulated release of asprosin. The asprosin peptide may be protected from degradation in adipose tissue. We present evidence for an alternative possibility, that asprosin mRNA is generated independently from an internal promoter within the 3' end of the FBN1 gene, which would allow for regulation independent of fibrillin-synthesis and is more economical of cellular resources. The discovery of asprosin opened exciting possibilities for treatment of metabolic syndrome related conditions, but there is much to be understood before such therapies could be introduced into the clinic.

EMILIN1 deficiency causes arterial tortuosity with osteopenia and connects impaired elastogenesis with defective collagen fibrillogenesis

EMILIN1 (elastin-microfibril-interface-located-protein-1) is a structural component of the elastic fiber network and localizes to the interface between the fibrillin microfibril scaffold and the elastin core. How EMILIN1 contributes to connective tissue integrity is not fully understood. Here, we report bi-allelic EMILIN1 loss-of-function variants causative for an entity combining cutis laxa, arterial tortuosity, aneurysm formation, and bone fragility, resembling autosomal-recessive cutis laxa type 1B, due to EFEMP2 (FBLN4) deficiency. In both humans and mice, absence of EMILIN1 impairs EFEMP2 extracellular matrix deposition and LOX activity resulting in impaired elastogenesis, reduced collagen crosslinking, and aberrant growth factor signaling. Collagen fiber ultrastructure and histopathology in EMILIN1- or EFEMP2-deficient skin and aorta corroborate these findings and murine Emilin1^-/- femora show abnormal trabecular bone formation and strength. Altogether, EMILIN1 connects elastic fiber network with collagen fibril formation, relevant for both bone and vascular tissue homeostasis.

ADAMTS6 cleaves the large latent TGFβ complex and increases the mechanotension of cells to activate TGFβ

The ADAMTS superfamily is composed of secreted metalloproteases and structurally related non-catalytic ADAMTS-like proteins. A subset of this superfamily, including ADAMTS6, ADAMTS10 and ADAMTSL2, are involved in elastic fiber assembly and bind to fibrillin and other matrix molecules that regulate the extracellular bioavailability of the potent growth factor TGFβ. Fibrillinopathies, that can also result from mutation of these ADAMTS/L proteins, have been linked to disrupted TGFβ homeostasis. ADAMTS6 and ADAMTS10 are homologous metalloproteases with poorly characterized substrates where ADAMTS10 is thought to process fibrillin-2 and ADAMTS6 latent TGFβ-binding protein (LTBP)-1. In order to understand the contribution of ADAMTS6, and these other members of the ADAMTS/L family, to TGFβ homeostasis, we have analyzed the effects of ADAMTS6, ADAMTS10 and ADAMTSL2 expression on TGFβ activation. We found that their expression increases TGFβ activation in a dose dependent manner, following stimulation with mature TGFβ1. For ADAMTS6, the catalytically active protease is required for effective TGFβ activation, where ADAMTS6 cleaves LTBP3 as well as LTBP1, and binds to the large latent TGFβ complexes of LTBP1 and LTBP3. Furthermore, ADAMTS6 expression increases the mechanotension of cells which results in inactivation of the Hippo Pathway, resulting in an increased translocation of YAP/TAZ complex to the nucleus. Together these findings suggest that when the balance of TGFβ is perturbed ADAMTS6 can influence TGFβ activation via two mechanisms. It directly cleaves the latent TGFβ complexes and also acts indirectly, along with ADAMTS10 and ADAMTSL2, by altering the mechanotension of cells. Together this increases activation of TGFβ from large latent complexes which may contribute to disease pathogenesis.

Transforming growth factor-β in tumour development

Transforming growth factor-β (TGFβ) is a ubiquitous cytokine essential for embryonic development and postnatal tissue homeostasis. TGFβ signalling regulates several biological processes including cell growth, proliferation, apoptosis, immune function, and tissue repair following injury. Aberrant TGFβ signalling has been implicated in tumour progression and metastasis. Tumour cells, in conjunction with their microenvironment, may augment tumourigenesis using TGFβ to induce epithelial-mesenchymal transition, angiogenesis, lymphangiogenesis, immune suppression, and autophagy. Therapies that target TGFβ synthesis, TGFβ-TGFβ receptor complexes or TGFβ receptor kinase activity have proven successful in tissue culture and in animal models, yet, due to limited understanding of TGFβ biology, the outcomes of clinical trials are poor. Here, we review TGFβ signalling pathways, the biology of TGFβ during tumourigenesis, and how protein quality control pathways contribute to the tumour-promoting outcomes of TGFβ signalling.

Targets for Renal Carcinoma Growth Control Identified by Screening FOXD1 Cell Proliferation Pathways

Simple Summary

FOXD1 regulates the proliferation of clear cell renal cell carcinoma (ccRCC) cells, and ccRCC cells in which FOXD1 has been inactivated do not form tumors efficiently in an animal model. Reproducing growth inhibition in tumor cells by inhibiting FOXD1 pathways presents a possible therapeutic approach for ccRCC and other cancers. We have established an analysis strategy to identify FOXD1-regulated target pathways that may be therapeutically tractable, and compounds that modulate these pathways were selected for testing. Targets in three pathways were identified: FOXM1, PME1, and TMEM167A, which were inhibited by compounds FDI-6, AMZ-30, and silibinin, respectively. The effects of these compounds on the growth of tumor cells from patients cultured in a novel 3D tumor-replica culture environment revealed that FDI-6 and silibinin had strong growth inhibitory effects. This investigation informs new therapeutic targets to control ccRCC tumor growth, and provides a strategy to compare the responsiveness of individual patient tumor replicas to growth-inhibitory compounds.

Abstract

Clinical association studies suggest that FOXD1 is a determinant of patient outcome in clear cell renal cell carcinoma (ccRCC), and laboratory investigations have defined a role for this transcription factor in controlling the growth of tumors through regulation of the G2/M cell cycle transition. We hypothesized that the identification of pathways downstream of FOXD1 may define candidates for pharmacological modulation to suppress the G2/M transition in ccRCC. We developed an analysis pipeline that utilizes RNA sequencing, transcription factor binding site analysis, and phenotype validation to identify candidate effectors downstream from FOXD1. Compounds that modulate candidate pathways were tested for their ability to cause growth delay at G2/M. Three targets were identified: FOXM1, PME1, and TMEM167A, which were targeted by compounds FDI-6, AMZ-30, and silibinin, respectively. A 3D ccRCC tumor replica model was used to investigate the effects of these compounds on the growth of primary cells from five patients. While silibinin reduced 3D growth in a subset of tumor replicas, FDI-6 reduced growth in all. This study identifies tractable pathways to target G2/M transition and inhibit ccRCC growth, demonstrates the applicability of these strategies across patient tumor replicas, and provides a platform for individualized patient testing of compounds that inhibit tumor growth.

Experimental evidence of the genetic hypothesis on the etiology of bicuspid aortic valve aortopathy in the hamster model

Bicuspid aortopathy occurs in approximately 50% of patients with bicuspid aortic valve (BAV), the most prevalent congenital cardiac malformation. Although different molecular players and etiological factors (genetic and hemodynamic) have been suggested to be involved in aortopathy predisposition and progression, clear etiophysiopathological mechanisms of disease are still missing. The isogenic (genetically uniform) hamster (T) strain shows 40% incidence of BAV, but aortic dilatations have not been detected in this model. We have performed comparative anatomical, histological and molecular analyses of the ascending aorta of animals with tricuspid aortic valve (TAV) and BAV from the T strain (TTAV and TBAV, respectively) and with TAV from a control strain (HTAV). Aortic diameter, smooth muscle apoptosis, elastic waviness, and Tgf-β and Fbn-2 expression were significantly increased in T strain animals, regardless of the valve morphology. Strain and aortic valve morphology did not affect Mmp-9 expression, whereas Mmp-2 transcripts were reduced in BAV animals. eNOS protein amount decreased in both TBAV and TTAV compared to HTAV animals. Thus, histomorphological and molecular alterations of the ascending aorta appear in a genetically uniform spontaneous hamster model irrespective of the aortic valve morphology. This is a direct experimental evidence supporting the genetic association between BAV and aortic dilatation. This model may represent a population of patients with predisposition to BAV aortopathy, in which increased expression of Tgf-β and Fbn-2 alters elastic lamellae structure and induces cell apoptosis mediated by eNOS. Patients either with TAV or BAV with the same genetic defect may show the same risk to develop bicuspid aortopathy.

Latent Transforming Growth Factor β Binding Protein 3 Controls Adipogenesis

Transforming growth factor-beta (TGFβ) is released from cells as part of a trimeric latent complex consisting of TGFβ, the TGFβ propeptides, and either a latent TGFβ binding protein (LTBP) or glycoprotein-A repetitions predominant (GARP) protein. LTBP1 and 3 modulate latent TGFβ function with respect to secretion, matrix localization, and activation and, therefore, are vital for the proper function of the cytokine in a number of tissues. TGFβ modulates stem cell differentiation into adipocytes (adipogenesis), but the potential role of LTBPs in this process has not been studied. We observed that 72 h post adipogenesis initiation Ltbp1, 2, and 4 expression levels decrease by 74-84%, whereas Ltbp3 expression levels remain constant during adipogenesis. We found that LTBP3 silencing in C3H/10T1/2 cells reduced adipogenesis, as measured by the percentage of cells with lipid vesicles and the expression of the transcription factor peroxisome proliferator-activated receptor gamma (PPARγ). Lentiviral mediated expression of an Ltbp3 mRNA resistant to siRNA targeting rescued the phenotype, validating siRNA specificity. Knockdown (KD) of Ltbp3 expression in 3T3-L1, M2, and primary bone marrow stromal cells (BMSC) indicated a similar requirement for Ltbp3. Epididymal and inguinal white adipose tissue fat pad weights of Ltbp3^-/- mice were reduced by 62% and 57%, respectively, compared to wild-type mice. Inhibition of adipogenic differentiation upon LTBP3 loss is mediated by TGFβ, as TGFβ neutralizing antibody and TGFβ receptor I kinase blockade rescue the LTBP3 KD phenotype. These results indicate that LTBP3 has a TGFβ-dependent function in adipogenesis both in vitro and possibly in vivo.

Treatment With Methotrexate Associated With Lipid Core Nanoparticles Prevents Aortic Dilation in a Murine Model of Marfan Syndrome

In Marfan syndrome (MFS), dilation, dissection, and rupture of the aorta occur. Inflammation can be involved in the pathogenicity of aortic defects and can thus be a therapeutic target for MFS. Previously, we showed that the formulation of methotrexate (MTX) associated with lipid nanoparticles (LDE) has potent anti-inflammatory effects without toxicity. To investigate whether LDEMTX treatment can prevent the development of aortic lesions in the MFS murine model. MgΔloxPneo MFS (n = 40) and wild-type (WT, n = 60) mice were allocated to 6 groups weekly injected with IP solutions of: (1) only LDE; (2) commercial MTX; (3) LDEMTX (dose = 1mg/kg) between 3rd and 6th months of life. After 12 weeks of treatments, animals were examined by echocardiography and euthanatized for morphometric and molecular studies. MFS mice treated with LDEMTX showed narrower lumens in the aortic arch, as well as in the ascending and descending aorta. LDEMTX reduced fibrosis and the number of dissections in MFS but not the number of elastic fiber disruptions. In MFS mice, LDEMTX treatment lowered protein expression of pro-inflammatory factors macrophages (CD68), T-lymphocytes (CD3), tumor necrosis factor-α (TNF-α), apoptotic factor cleaved-caspase 3, and type 1 collagen and lowered the protein expression of the transforming growth factor-β (TGF-β), extracellular signal-regulated kinases ½ (ERK1/2), and SMAD3. Protein expression of CD68 and CD3 had a positive correlation with an area of aortic lumen (r² = 0.36; p < 0.001), suggesting the importance of inflammation in the causative mechanisms of aortic dilation. Enhanced adenosine availability by LDEMTX was suggested by higher aortic expression of an anti-adenosine A2a receptor (A2a) and lower adenosine deaminase expression. Commercial MTX had negligible effects. LDEMTX prevented the development of MFS-associated aortic defects and can thus be a candidate for testing in clinical studies.

The Role of Transforming Growth Factor-β Signaling in Myxomatous Mitral Valve Degeneration

Mitral valve prolapse (MVP) due to myxomatous degeneration is one of the most important chronic degenerative cardiovascular diseases in people and dogs. It is a common cause of heart failure leading to significant morbidity and mortality in both species. Human MVP is usually classified into primary or non-syndromic, including Barlow’s Disease (BD), fibro-elastic deficiency (FED) and Filamin-A mutation, and secondary or syndromic forms (typically familial), such as Marfan syndrome (MFS), Ehlers-Danlos syndrome, and Loeys–Dietz syndrome. Despite different etiologies the diseased valves share pathological features consistent with myxomatous degeneration. To reflect this common pathology the condition is often called myxomatous mitral valve degeneration (disease) (MMVD) and this term is universally used to describe the analogous condition in the dog. MMVD in both species is characterized by leaflet thickening and deformity, disorganized extracellular matrix, increased transformation of the quiescent valve interstitial cell (qVICs) to an activated state (aVICs), also known as activated myofibroblasts. Significant alterations in these cellular activities contribute to the initiation and progression of MMVD due to the increased expression of transforming growth factor-β (TGF-β) superfamily cytokines and the dysregulation of the TGF-β signaling pathways. Further understanding the molecular mechanisms of MMVD is needed to identify pharmacological manipulation strategies of the signaling pathway that might regulate VIC differentiation and so control the disease onset and development. This review briefly summarizes current understanding of the histopathology, cellular activities, molecular mechanisms and pathogenesis of MMVD in dogs and humans, and in more detail reviews the evidence for the role of TGF-β.

Association of TGF-β Canonical Signaling-Related Core Genes With Aortic Aneurysms and Aortic Dissections

Transforming growth factor-beta (TGF-β) signaling is essential for the maintenance of the normal structure and function of the aorta. It includes SMAD-dependent canonical pathways and noncanonical signaling pathways. Accumulated genetic evidence has shown that TGF-β canonical signaling-related genes have key roles in aortic aneurysms (AAs) and aortic dissections and many gene mutations have been identified in patients, such as those for transforming growth factor-beta receptor one TGFBR1, TGFBR2, SMAD2, SMAD3, SMAD4, and SMAD6. Aortic specimens from patients with these mutations often show paradoxically enhanced TGF-β signaling. Some hypotheses have been proposed and new AA models in mice have been constructed to reveal new mechanisms, but the role of TGF-β signaling in AAs is controversial. In this review, we focus mainly on the role of canonical signaling-related core genes in diseases of the aorta, as well as recent advances in gene-mutation detection, animal models, and in vitro studies.

LTBP1 promotes fibrillin incorporation into the extracellular matrix

LTBP1 is a large extracellular matrix protein and an associated ligand of fibrillin-microfibrils. Knowledge of LTBP1 functions is largely limited to its role in targeting and sequestering TGFβ growth factors within the extracellular matrix, thereby regulating their bioavailability. However, the recent description of a wide spectrum of phenotypes in multiple tissues in patients harboring LTBP1 pathogenic variants suggests a multifaceted role of the protein in the homeostasis of connective tissues. To better understand the human pathology caused by LTBP1 deficiency it is important to investigate its functional role in extracellular matrix formation. In this study, we show that LTBP1 coordinates the incorporation of fibrillin-1 and -2 into the extracellular matrix in vitro. We also demonstrate that this function is differentially exerted by the two isoforms, the short and long forms of LTBP1. Thereby our findings uncover a novel TGFβ-independent LTBP1 function potentially contributing to the development of connective tissue disorders.

The fibrillinopathies: new insights with focus on the paradigm of opposing phenotypes for both FBN1 and FBN2

Different pathogenic variants in the fibrillin‐1 gene (FBN1) cause Marfan syndrome and acromelic dysplasias. Whereas the musculoskeletal features of Marfan syndrome involve tall stature, arachnodactyly, joint hypermobility, and muscle hypoplasia, acromelic dysplasia patients present with short stature, brachydactyly, stiff joints, and hypermuscularity. Similarly, pathogenic variants in the fibrillin‐2 gene (FBN2) cause either a Marfanoid congenital contractural arachnodactyly or a FBN2‐related acromelic dysplasia that most prominently presents with brachydactyly. The phenotypic and molecular resemblances between both the FBN1 and FBN2‐related disorders suggest that reciprocal pathomechanistic lessons can be learned. In this review, we provide an updated overview and comparison of the phenotypic and mutational spectra of both the “tall” and “short” fibrillinopathies. The future parallel functional study of both FBN1/2‐related disorders will reveal new insights into how pathogenic fibrillin variants differently affect the fibrillin microfibril network and/or growth factor homeostasis in clinically opposite syndromes. This knowledge may eventually be translated into new therapeutic approaches by targeting or modulating the fibrillin microfibril network and/or the signaling pathways under its control.

Identification, function, and biological relevance of POGLUT2 and POGLUT3

O-glycosylation of Epidermal Growth Factor-like (EGF) repeats plays crucial roles in protein folding, trafficking and function. The Notch extracellular domain has been used as a model to study these mechanisms due to its many O-glycosylated EGF repeats. Three enzymes were previously known to O-glycosylate Notch EGF repeats: Protein O-Glucosyltransferase 1 (POGLUT1), Protein O-Fucosyltransferase 1 (POFUT1), and EGF Domain Specific O-Linked N-Acetylglucosamine Transferase (EOGT). All of these modifications affect Notch activity. Recently, POGLUT2 and POGLUT3 were identified as two novel O-glucosyltransferases that modify a few Notch EGF repeats at sites distinct from those modified by POGLUT1. Comparison of these modification sites revealed a putative consensus sequence which predicted modification of many extracellular matrix proteins including fibrillins (FBNs) and Latent TGFβ-binding proteins (LTBPs). Glycoproteomic analysis revealed that approximately half of the 47 EGF repeats in FBN1 and FBN2, and half of the 18 EGF repeats in LTBP1, are modified by POGLUT2 and/or POGLUT3. Cellular assays showed that loss of modifications by POGLUT2 and/or POGLUT3 significantly reduces FBN1 secretion. There is precedent for EGF modifications to affect protein-protein interactions, as has been demonstrated by research of POGLUT1 and POFUT1 modifications on Notch. Here we discuss the identification and characterization of POGLUT2 and POGLUT3 and the ongoing research that continues to elucidate the biological significance of these novel enzymes.

Elastic Fibre Proteins in Elastogenesis and Wound Healing

As essential components of our connective tissues, elastic fibres give tissues such as major blood vessels, skin and the lungs their elasticity. Their formation is complex and co-ordinately regulated by multiple factors. In this review, we describe key players in elastogenesis: fibrillin-1, tropoelastin, latent TGFβ binding protein-4, and fibulin-4 and -5. We summarise their roles in elastogenesis, discuss the effect of their mutations on relevant diseases, and describe their interactions involved in forming the elastic fibre network. Moreover, we look into their roles in wound repair for a better understanding of their potential application in tissue regeneration.

Association of gene polymorphisms in FBN1 and TGF-β signaling with the susceptibility and prognostic outcomes of Stanford type B aortic dissection

Background

This study is aimed at investigating the association of Fibrillin-1 (FBN1) and transforming growth factor β (TGF-β) signaling-related gene polymorphisms with the susceptibility of Stanford type B aortic dissection (AD) and its clinical prognostic outcomes.

Methods

Five single-nucleotide polymorphism (SNPs) (FBN1rs 145233125, rs201170905, rs11070646, TGFB1rs1800469, and TGFB2rs900) were analyzed in patients with Stanford type B AD (164) and healthy controls (317). Gene–gene and gene–environment interactions were assessed by generalized multifactor dimensionality reduction. A 4-year follow-up was performed for all AD patients.

Results

G carriers of FBN1 rs201170905 and TGFB1 rs1800469 have an increased risk of Stanford type B AD. The interaction of FBN1, TGFB1, TGFB2 and environmental promoted to the increased risk of type B AD (cross-validation consistency = 10/10, P = 0.001). Dominant models of FBN1rs145233125 TC + CC genotype (P = 0.028), FBN1 rs201170905 AG + GG (P = 0.047) and TGFB1 rs1800469 AG + GG (P = 0.052) were associated with an increased risk of death of Stanford type B AD. The recessive model of FBN1 rs145233125 CC genotype (P < 0.001), FBN1rs201170905 GG (P < 0.001), TGFB1 rs1800469 AG + GG genotype (P = 0.011) was associated with an increased risk of recurrence of chest pain in Stanford type B AD.

Conclusions

The interactions of gene–gene and gene–environment are related with the risk of Stanford type B AD. C carriers of rs145233125, G carriers of rs201170905 and G carriers of rs1800469 may be the poor clinical outcome indicators of mortality and recurrent chest pain in Stanford type B AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01213-z.

The Fibrillin-1/VEGFR2/STAT2 signaling axis promotes chemoresistance via modulating glycolysis and angiogenesis in ovarian cancer organoids and cells

Background

Chemotherapy resistance is a primary reason of ovarian cancer therapy failure; hence it is important to investigate the underlying mechanisms of chemotherapy resistance and develop novel potential therapeutic targets.

Methods

RNA sequencing of cisplatin‐resistant and ‐sensitive (chemoresistant and chemosensitive, respectively) ovarian cancer organoids was performed, followed by detection of the expression level of fibrillin‐1 (FBN1) in organoids and clinical specimens of ovarian cancer. Subsequently, glucose metabolism, angiogenesis, and chemosensitivity were analyzed in structural glycoprotein FBN1‐knockout cisplatin‐resistant ovarian cancer organoids and cell lines. To gain insights into the specific functions and mechanisms of action of FBN1 in ovarian cancer, immunoprecipitation, silver nitrate staining, mass spectrometry, immunofluorescence, Western blotting, and Fӧrster resonance energy transfer‐fluorescence lifetime imaging analyses were performed, followed by in vivo assays using vertebrate model systems of nude mice and zebrafish.

Results

FBN1 expression was significantly enhanced in cisplatin‐resistant ovarian cancer organoids and tissues, indicating that FBN1 might be a key factor in chemoresistance of ovarian cancer. We also discovered that FBN1 sustained the energy stress and induced angiogenesis in vitro and in vivo, which promoted the cisplatin‐resistance of ovarian cancer. Knockout of FBN1 combined with treatment of the antiangiogenic drug apatinib improved the cisplatin‐sensitivity of ovarian cancer cells. Mechanistically, FBN1 mediated the phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2) at the Tyr1054 residue, which activated its downstream focal adhesion kinase (FAK)/protein kinase B (PKB or AKT) pathway, induced the phosphorylation of signal transducer and activator of transcription 2 (STAT2) at the tyrosine residue 690 (Tyr690), promoted the nuclear translocation of STAT2, and ultimately altered the expression of genes associated with STAT2‐mediated angiogenesis and glycolysis.

Conclusions

The FBN1/VEGFR2/STAT2 signaling axis may induce chemoresistance of ovarian cancer cells by participating in the process of glycolysis and angiogenesis. The present study suggested a novel FBN1‐targeted therapy and/or combination of FBN1 inhibition and antiangiogenic drug for treating ovarian cancer.

Fibrillin-1 regulates periostin expression during maintenance of periodontal homeostasis

Background/purpose

Human periodontal ligament consists of elastic system fibers, mainly fibrillin-1 (FBN1). Periostin (POSTN) maintains periodontal homeostasis. A previous study showed that the expression of Postn in periodontal ligament cells was decreased in mice underexpressing Fbn1. However, the relationship between FBN1 and POSTN is not fully understood in the context of mechanical stress. FBN1 contributes to transforming growth factor β1 (TGF-β1) activation; TGF-β1 upregulates the expression of POSTN in human periodontal ligament cells. This study examined whether FBN1 contributed to the maintenance of periodontal homeostasis in cultured human periodontal ligament cells.

Materials and methods

Human periodontal ligament fibroblasts (HPDLFs) were exposed to mechanical force via centrifugation. The expression of POSTN was examined by quantitative reverse transcription polymerase chain reaction. The phosphorylation of Smad2 in the TGF-β/Smad signaling pathway was monitored by western blotting.

Results

The expression levels of FBN1 and POSTN were not significantly decreased by centrifugation. However, the expression of POSTN after centrifugation significantly decreased upon knockdown of FBN1. The phosphorylation of Smad2 after centrifugation was decreased, regardless of FBN1 knockdown. Supplementation with 0.1 ng/ml recombinant human TGF-β1 rescued POSTN expression after centrifugation in HPDLFs upon knockdown of FBN1.

Conclusion

FBN1 regulates the expression of POSTN to maintain periodontal homeostasis via TGF-β/Smad signaling during centrifugation.

Latent TGFβ-binding proteins 1 and 3 protect the larval zebrafish outflow tract from aneurysmal dilatation

Aortic root aneurysm is a common cause of morbidity and mortality in Loeys-Dietz and Marfan syndromes, where perturbations in transforming growth factor beta (TGFβ) signaling play a causal or contributory role, respectively. Despite the advantages of cross-species disease modeling, animal models of aortic root aneurysm are largely restricted to genetically engineered mice. Here, we report that zebrafish devoid of the genes encoding latent-transforming growth factor beta-binding protein 1 and 3 (ltbp1 and ltbp3, respectively) develop rapid and severe aneurysm of the outflow tract (OFT), the aortic root equivalent. Similar to syndromic aneurysm tissue, the distended OFTs display evidence for paradoxical hyperactivated TGFβ signaling. RNA-sequencing revealed significant overlap between the molecular signatures of disease tissue from mutant zebrafish and a mouse model of Marfan syndrome. Moreover, chemical inhibition of TGFβ signaling in wild-type animals phenocopied mutants but chemical activation did not, demonstrating that TGFβ signaling is protective against aneurysm. Human relevance is supported by recent studies implicating genetic lesions in LTBP3 and, potentially, LTBP1 as heritable causes of aortic root aneurysm. Ultimately, our data demonstrate that zebrafish can now be leveraged to interrogate thoracic aneurysmal disease and identify novel lead compounds through small-molecule suppressor screens. This article has an associated First Person interview with the first author of the paper.

Latent TGFβ complexes are transglutaminase cross-linked to fibrillin to facilitate TGFβ activation

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TGFβ is regulated via the formation latent complexes in the extracellular matrix.

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Fibrillin-1 is a substrate for transglutaminase-2 which forms a covalent link between fibrillin-1 and latent TGFβ complexes.

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Formation of the cross-link increases TGFβ activation in cell-based assays.

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Fibrillin may direct the latent TGFβ complexes to the cell surface for activation.

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The structure of the cross-linked LTBP1-fibrillin complex has a perpendicular arrangement to enable bridging long-range interactions between the matrix and cell surface.

TGFβ superfamily members are potent growth factors in the extracellular matrix with essential roles in all aspects of cellular behaviour. Latent TGFβ binding proteins (LTBPs) are co-expressed with TGFβ, essential for correct folding and secretion of the growth factor, to form large latent complexes. These large latent complexes bind extracellular proteins such as fibrillin for sequestration of TGFβ in the matrix, essential for normal tissue function, and dysregulated TGFβ signalling is a hallmark of many fibrillinopathies. Transglutaminase-2 (TG2) cross-linking of LTBPs is known to play a role in TGFβ activation but the underlying molecular mechanisms are not resolved. Here we show that fibrillin is a matrix substrate for TG2 and that TG2 cross-linked complexes can be formed between fibrillin and LTBP-1 and -3, and their latent TGFβ complexes. The structure of the fibrillin-LTBP1 complex shows that the two elongated proteins interact in a perpendicular arrangement which would allow them to form distal interactions between the matrix and the cell surface. Formation of the cross-link with fibrillin does not change the interaction between latent TGFβ and integrin αVβ6 but does increase TGFβ activation in cell-based assays. The activating effect may be due to direction of the latent complexes to the cell surface by fibrillin, as competition with heparan sulphate can ameliorate the activating effect. Together, these data support that TGFβ activation can be enhanced by covalent tethering of LTBPs to the matrix via fibrillin.

An update of medical care in Marfan syndrome

Marfan syndrome (MFS), a multisystemic connective disorder, caused by fibrillin 1 gene mutations with autosomal dominant inheritance. The disease spectrum is wide and the major causes of death are related to aortic root aneurysm or dissection. The purposes of medical treatment are to reduce structural changes in the aortic wall and slow aortic root dilatation. Advance in medical researches have provided new insights into the pathogenesis of disease and opened up new horizons for treatments. Several medications such as angiotensin II type I receptor blockers, β-blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers, tetracyclines, and statins have been studied for the purpose. Currently, the life expectancy of Marfan patients improves significantly and is closes to the general population with proper treatment. In this article, we review and update the medical treatments for patients with MFS.

Mechanical Cues: Bidirectional Reciprocity in the Extracellular Matrix Drives Mechano-Signalling in Articular Cartilage

The composition and organisation of the extracellular matrix (ECM), particularly the pericellular matrix (PCM), in articular cartilage is critical to its biomechanical functionality; the presence of proteoglycans such as aggrecan, entrapped within a type II collagen fibrillar network, confers mechanical resilience underweight-bearing. Furthermore, components of the PCM including type VI collagen, perlecan, small leucine-rich proteoglycans—decorin and biglycan—and fibronectin facilitate the transduction of both biomechanical and biochemical signals to the residing chondrocytes, thereby regulating the process of mechanotransduction in cartilage. In this review, we summarise the literature reporting on the bidirectional reciprocity of the ECM in chondrocyte mechano-signalling and articular cartilage homeostasis. Specifically, we discuss studies that have characterised the response of articular cartilage to mechanical perturbations in the local tissue environment and how the magnitude or type of loading applied elicits cellular behaviours to effect change. In vivo, including transgenic approaches, and in vitro studies have illustrated how physiological loading maintains a homeostatic balance of anabolic and catabolic activities, involving the direct engagement of many PCM molecules in orchestrating this slow but consistent turnover of the cartilage matrix. Furthermore, we document studies characterising how abnormal, non-physiological loading including excessive loading or joint trauma negatively impacts matrix molecule biosynthesis and/or organisation, affecting PCM mechanical properties and reducing the tissue’s ability to withstand load. We present compelling evidence showing that reciprocal engagement of the cells with this altered ECM environment can thus impact tissue homeostasis and, if sustained, can result in cartilage degradation and onset of osteoarthritis pathology. Enhanced dysregulation of PCM/ECM turnover is partially driven by mechanically mediated proteolytic degradation of cartilage ECM components. This generates bioactive breakdown fragments such as fibronectin, biglycan and lumican fragments, which can subsequently activate or inhibit additional signalling pathways including those involved in inflammation. Finally, we discuss how bidirectionality within the ECM is critically important in enabling the chondrocytes to synthesise and release PCM/ECM molecules, growth factors, pro-inflammatory cytokines and proteolytic enzymes, under a specified load, to influence PCM/ECM composition and mechanical properties in cartilage health and disease.

Cooperative Mechanism of ADAMTS/ ADAMTSL and Fibrillin-1 in the Marfan Syndrome and Acromelic Dysplasias

The term “fibrillinopathies” gathers various diseases with a wide spectrum of clinical features and severity but all share mutations in the fibrillin genes. The first described fibrillinopathy, Marfan syndrome (MFS), is a multisystem disease with a unique combination of skeletal, thoracic aortic aneurysm (TAA) and ocular features. The numerous FBN1 mutations identified in MFS are located all along the gene, leading to the same pathogenic mechanism. The geleophysic/acromicric dysplasias (GD/AD), characterized by short stature, short extremities, and joint limitation are described as “the mirror image” of MFS. Previously, in GD/AD patients, we identified heterozygous FBN1 mutations all affecting TGFβ-binding protein-like domain 5 (TB5). ADAMTS10, ADAMTS17 and, ADAMTSL2 are also involved in the pathogenic mechanism of acromelic dysplasia. More recently, in TAA patients, we identified mutations in THSD4, encoding ADAMTSL6, a protein belonging to the ADAMTSL family suggesting that ADAMTSL proteins are also involved in the Marfanoid spectrum. Together with human genetic data and generated knockout mouse models targeting the involved genes, we provide herein an overview of the role of fibrillin-1 in opposite phenotypes. Finally, we will decipher the potential biological cooperation of ADAMTS-fibrillin-1 involved in these opposite phenotypes.

Structural studies of elastic fibre and microfibrillar proteins

Elastic tissues owe their functional properties to the composition of their extracellular matrices, particularly the range of extracellular, multidomain extensible elastic fibre and microfibrillar proteins. These proteins include elastin, fibrillin, latent TGFβ binding proteins (LTBPs) and collagens, where their biophysical and biochemical properties not only give the matrix structural integrity, but also play a vital role in the mechanisms that underlie tissue homeostasis. Thus far structural information regarding the structure and hierarchical assembly of these molecules has been challenging and the resolution has been limited due to post-translational modification and their multidomain nature leading to flexibility, which together result in conformational and structural heterogeneity. In this review, we describe some of the matrix proteins found in elastic fibres and the new emerging techniques that can shed light on their structure and dynamic properties.

Gene Therapy for Cardiovascular Disease: Basic Research and Clinical Prospects

In recent years, the vital role of genetic factors in human diseases have been widely recognized by scholars with the deepening of life science research, accompanied by the rapid development of gene-editing technology. In early years, scientists used homologous recombination technology to establish gene knock-out and gene knock-in animal models, and then appeared the second-generation gene-editing technology zinc-finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs) that relied on nucleic acid binding proteins and endonucleases and the third-generation gene-editing technology that functioned through protein-nucleic acids complexes-CRISPR/Cas9 system. This holds another promise for refractory diseases and genetic diseases. Cardiovascular disease (CVD) has always been the focus of clinical and basic research because of its high incidence and high disability rate, which seriously affects the long-term survival and quality of life of patients. Because some inherited cardiovascular diseases do not respond well to drug and surgical treatment, researchers are trying to use rapidly developing genetic techniques to develop initial attempts. However, significant obstacles to clinical application of gene therapy still exists, such as insufficient understanding of the nature of cardiovascular disease, limitations of genetic technology, or ethical concerns. This review mainly introduces the types and mechanisms of gene-editing techniques, ethical concerns of gene therapy, the application of gene therapy in atherosclerosis and inheritable cardiovascular diseases, in-stent restenosis, and delivering systems.

Connective Tissue Disorders and Cardiovascular Complications: The Indomitable Role of Transforming Growth Factor-β Signaling

Marfan Syndrome (MFS) and Loeys-Dietz Syndrome (LDS) represent heritable connective tissue disorders that segregate with a similar pattern of cardiovascular defects (thoracic aortic aneurysm, mitral valve prolapse/regurgitation, and aortic dilatation with regurgitation). This pattern of cardiovascular defects appears to be expressed along a spectrum of severity in many heritable connective tissue disorders and raises suspicion of a relationship between the normal development of connective tissues and the cardiovascular system. With overwhelming evidence of the involvement of aberrant Transforming Growth Factor-beta (TGF-β) signaling in MFS and LDS, this signaling pathway may represent the common link in the relationship between connective tissue disorders and their associated cardiovascular complications. To further explore this hypothetical link, this chapter will review the TGF-β signaling pathway, the heritable connective tissue syndromes related to aberrant TGF-β signaling, and will discuss the pathogenic contribution of TGF-β to these syndromes with a primary focus on the cardiovascular system.

Pathophysiology and Pathogenesis of Marfan Syndrome

Marfan syndrome (MFS) is a systemic connective tissue disorder that is inherited in an autosomal dominant pattern with variable penetrance. While clinically this disease manifests in many different ways, the most life-threatening manifestations are related to cardiovascular complications including mitral valve prolapse, aortic insufficiency, dilatation of the aortic root, and aortic dissection. In the past 30 years, research efforts have not only identified the genetic locus responsible but have begun to elucidate the molecular pathogenesis underlying this disorder, allowing for the development of seemingly rational therapeutic strategies for treating affected individuals. In spite of these advancements, the cardiovascular complications still remain as the most life-threatening clinical manifestations. The present chapter will focus on the pathophysiology and clinical treatment of Marfan syndrome, providing an updated overview of the recent advancements in molecular genetics research and clinical trials, with an emphasis on how this information can focus future efforts toward finding betters ways to detect, diagnose, and treat this devastating condition.

Respiratory manifestations of Marfan syndrome: a narrative review

Objective

The prevalence of Marfan syndrome (MFS) is estimated to be 1 in 10,000 to 15,000 individuals, but the phenotype of MFS may not be apparent and hence its diagnosis may not be considered by clinicians. Furthermore, the effects of MFS on the lungs and breathing are underrecognized despite the high morbidity that can occur. The objective of this Narrative Review is to delineate the molecular consequences of a defective fibrillin-1 protein and the skeletal and lung abnormalities in MFS that may contribute to respiratory compromise. It is important for clinicians to be cognizant of these MFS-associated respiratory conditions, and a contemporaneous review is needed.

Background

MFS is an autosomal dominant, connective tissue disorder caused by mutations in the FIBRILLIN-1 (FBN1) gene, resulting in abnormal elastic fibers as well as increased tissue availability of transforming growth factor-beta (TGFβ), both of which lead to the protean clinical abnormalities. While these clinical characteristics are most often recognized in the cardiovascular, skeletal, and ocular systems, MFS may also cause significant impairment on the lungs and breathing.

Methods

We searched PubMed for the key words of “Marfan syndrome,” “pectus excavatum,” and “scoliosis” with that of “lung disease,” “breathing”, or “respiratory disease.” The bibliographies of identified articles were further searched for relevant articles not previously identified. Each relevant article was reviewed by one or more of the authors and a narrative review was composed.

Conclusions

Though the classic manifestations of MFS are cardiovascular, skeletal, and ocular, FBN1 gene mutation can induce a variety of effects on the respiratory system, inducing substantial morbidity and potentially increased mortality. These respiratory effects may include chest wall and spinal deformities, emphysema, pneumothorax, sleep apnea, and potentially increased incidence of asthma, bronchiectasis, and interstitial lung disease. Further research into approaches to prevent respiratory complications is needed, but improved recognition of the respiratory complications of MFS is necessary before this research is likely to occur.

Autosomal Recessive Cutis Laxa 1C Mutations Disrupt the Structure and Interactions of Latent TGFβ Binding Protein-4

Latent TGFβ binding protein-4 (LTBP4) is a multi-domain glycoprotein, essential for regulating the extracellular bioavailability of TGFβ and assembly of elastic fibre proteins, fibrillin-1 and tropoelastin. LTBP4 mutations are linked to autosomal recessive cutis laxa type 1C (ARCL1C), a rare congenital disease characterised by high mortality and severely disrupted connective tissues. Despite the importance of LTBP4, the structure and molecular consequences of disease mutations are unknown. Therefore, we analysed the structural and functional consequences of three ARCL1C causing point mutations which effect highly conserved cysteine residues. Our structural and biophysical data show that the LTBP4 N- and C-terminal regions are monomeric in solution and adopt extended conformations with the mutations resulting in subtle changes to their conformation. Similar to LTBP1, the N-terminal region is relatively inflexible, whereas the C-terminal region is flexible. Interaction studies show that one C-terminal mutation slightly decreases binding to fibrillin-1. We also found that the LTBP4 C-terminal region directly interacts with tropoelastin which is perturbed by both C-terminal ARCL1C mutations, whereas an N-terminal mutation increased binding to fibulin-4 but did not affect the interaction with heparan sulphate. Our results suggest that LTBP4 mutations contribute to ARCL1C by disrupting the structure and interactions of LTBP4 which are essential for elastogenesis in a range of mammalian connective tissues.

Marfan syndrome

Marfan syndrome (MFS) is an autosomal dominant, age-related but highly penetrant condition with substantial intrafamilial and interfamilial variability. MFS is caused by pathogenetic variants in FBN1, which encodes fibrillin-1, a major structural component of the extracellular matrix that provides support to connective tissues, particularly in arteries, the pericondrium and structures in the eye. Up to 25% of individuals with MFS have de novo variants. The most prominent manifestations of MFS are asymptomatic aortic root aneurysms, aortic dissections, dislocation of the ocular lens (ectopia lentis) and skeletal abnormalities that are characterized by overgrowth of the long bones. MFS is diagnosed based on the Ghent II nosology; genetic testing confirming the presence of a FBN1 pathogenetic variant is not always required for diagnosis but can help distinguish MFS from other heritable thoracic aortic disease syndromes that can present with skeletal features similar to those in MFS. Untreated aortic root aneurysms can progress to life-threatening acute aortic dissections. Management of MFS requires medical therapy to slow the rate of growth of aneurysms and decrease the risk of dissection. Routine surveillance with imaging techniques such as transthoracic echocardiography, CT or MRI is necessary to monitor aneurysm growth and determine when to perform prophylactic repair surgery to prevent an acute aortic dissection.

POGLUT2 and POGLUT3 O-glucosylate multiple EGF repeats in fibrillin-1, -2, and LTBP1 and promote secretion of fibrillin-1

Fibrillin-1 (FBN1) is the major component of extracellular matrix microfibrils, which are required for proper development of elastic tissues, including the heart and lungs. Through protein-protein interactions with latent transforming growth factor (TGF) β-binding protein 1 (LTBP1), microfibrils regulate TGF-β signaling. Mutations within the 47 epidermal growth factor-like (EGF) repeats of FBN1 cause autosomal dominant disorders including Marfan Syndrome, which is characterized by disrupted TGF-β signaling. We recently identified two novel protein O-glucosyltransferases, Protein O-glucosyltransferase 2 (POGLUT2) and 3 (POGLUT3), that modify a small fraction of EGF repeats on Notch. Here, using mass spectral analysis, we show that POGLUT2 and POGLUT3 also modify over half of the EGF repeats on FBN1, fibrillin-2 (FBN2), and LTBP1. While most sites are modified by both enzymes, some sites show a preference for either POGLUT2 or POGLUT3. POGLUT2 and POGLUT3 are homologs of POGLUT1, which stabilizes Notch proteins by addition of O-glucose to Notch EGF repeats. Like POGLUT1, POGLUT2 and 3 can discern a folded versus unfolded EGF repeat, suggesting POGLUT2 and 3 are involved in a protein folding pathway. In vitro secretion assays using the N-terminal portion of recombinant FBN1 revealed reduced FBN1 secretion in POGLUT2 knockout, POGLUT3 knockout, and POGLUT2 and 3 double-knockout HEK293T cells compared with wild type. These results illustrate that POGLUT2 and 3 function together to O-glucosylate protein substrates and that these modifications play a role in the secretion of substrate proteins. It will be interesting to see how disease variants in these proteins affect their O-glucosylation.