New insights into form and function of fibronectin splice variants

Serum Fibronectin Levels Increased Significantly Following the Administration of an Inactivated SARS-CoV-2 Vaccine: A Prospective Observational Study

Background

There has been a lack of comprehensive studies on the long-term observation of laboratory values following the administration of SARS-CoV-2 vaccines. The objective of this study is to assess the long-term impact of inactivated SARS-CoV-2 vaccines on coagulation function and other health indicators.

Methods

We enrolled residents of Chengdu who consented to receive inactivated SARS-CoV-2 vaccines, categorizing them into two groups: healthy donors (n=40) and survivors of COVID-19 infection (n=34), based on their SARS-CoV-2 infection status prior to vaccination. Blood samples from the subjects were collected at specific intervals following vaccination.

Results

The levels of Fibronectin (FN) increased significantly in both healthy donors and survivors of COVID-19 infection after receiving two doses of the inactivated SARS-CoV-2 vaccine (both P < 0.001), and there was no statistically significant difference in the degree of FN increase between the two groups (153.05 ± 77.19 mg/L vs 172.32±90.42 mg/L, P=0.326). The rate of elevated FN levels was significantly higher six months after vaccination compared to the rate before vaccination, both in healthy donors (85.0% vs 5.0%, P<0.001) and in survivors of COVID-19 infection (94.1% vs 29.4%, P<0.001). Additionally, the levels of FN in healthy donors further increased six months after receiving a booster dose of the inactivated vaccine compared to pre-booster levels (569.90±119.44 mg/L vs 467.35±62.04 mg/L, P < 0.001).

Conclusion

The study indicates that serum FN levels increased significantly following the administration of the inactivated SARS-CoV-2 vaccine, and these elevated FN levels may persist for more than six months. However, it remains unclear whether this increase could result in any adverse effects.

Quantitative Assessment of Pulmonary Fibrosis in a Murine Model via a Multimodal Imaging Workflow

Disease-recapitulating animal models are valuable tools in preclinical development for the study of compounds. In the case of fibrotic pulmonary diseases such as idiopathic pulmonary fibrosis (IPF), the bleomycin model of lung injury in the mouse is widely used. To evaluate bleomycin-induced changes in the lung, we employed a quantitative, multimodal approach. Using in vivo microcomputed tomography (μCT), we demonstrated radiographic changes associated with disease progression in aeration levels of the lung parenchyma. There exists an unmet need for a quantitative, high-resolution imaging probe to detect pulmonary fibrosis, particularly that can differentiate between inflammatory and fibrotic components of the disease. Matrix remodeling and overexpression of extracellular matrix (ECM) proteins such as collagen and fibronectin are hallmarks of organ fibrosis. A splice variant of fibronectin containing extra domain A (FnEDA) is of particular interest in fibrosis due to its high level of expression in diseased tissue, which is confirmed here using immunohistochemistry (IHC) in mouse and human lungs. An antibody against FnEDA was evaluated for use as an imaging tool, particularly by using in vivo single-photon emission computed tomography (SPECT) and ex vivo near-infrared (NIR) fluorescence imaging. These data were further corroborated with histological tissue staining and fibrosis quantitation based on a Modified Ashcroft (MA) score and a digital image analysis of whole slide lung tissue sections. The fusion of these different approaches represents a robust integrated workflow combining anatomical and molecular imaging technologies to enable the visualization and quantitation of disease activity and treatment response with an inhibitor of the TGFβ signaling pathway.

FN1 shapes the behavior of papillary thyroid carcinoma through alternative splicing of EDB region

Papillary thyroid cancer (PTC) is often characterized by indolent behavior, small tumors with slow cell proliferation and a tendency to metastasize to cervical lymph node simultaneously, and the molecular mechanisms underlying that remain poorly understood. In this study, FN1 was the hottest gene of PTC and distinctive expression in PTC cells. FN1 deficiency severely inhibited the p53 signaling pathway, especially cyclin proteins, resulting in increased cell growth but hampered invasion. The alternatively splicing EDB region of FN1 was exclusively expressed in tumors, which impacted integrin β1 (ITGB1) bonding FN1 and its secretion process, resulting in completely distinct roles of two isoforms that FN1 including and skipping EDB domain. The isoform EDB(-)FN1 intracellularly inhibited tumor proliferation by upregulating p21 expression, whereas extracellular EDB(+)FN1 promoted lymph node metastasis via the VEGF signaling pathway in vitro and in vivo. Moreover, the alternative splicing EDB region of FN1 was modulated by p53-targeted protein ZMAT3 which activated cell migration and lymphoangiogenesis. Collectively, combined with p53-induced proteins, FN1 played both anti- and pro-cancer roles owing to EDB domain alternative splicing. FN1 is a potential determinant behind the characteristic behavior of PTC, which may contribute to a deeper understanding of the peculiarity of PTC and provide a promising target for regional lymph node metastasis.

Changes in various forms of fibronectin in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass - a prospective, observational study

Coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) is associated with the transient activation of a systemic inflammatory response. Fibronectin (FN), an endogenous inflammatory mediator, is a key component of the extracellular matrix. This study aimed to detect changes in cellular and plasma FN levels, as well as its potential fragmentation or FN-fibrin complex formation, in 40 patients undergoing CABG with CPB. Our results indicate that CPB was associated with changes in the levels of cellular and plasma FN and with intensified FN fragmentation. Moreover, FN-fibrin complexes were detected in all patients, indicating activation of the coagulation process during CPB. In a multivariate regression analysis, a history of arterial hypertension and CPB duration influenced plasma FN levels at 6 h (β = -0.458, p = 0.001; -0.375, p = 0.008, respectively) and 12 h (β = -0.293, p = 0.026; -0.554, p = 0.000) after surgery. Alterations in FN concentration, intensified FN degradation, and the presence of FN-fibrin complexes after surgery may suggest that these changes are related to the remodelling of the extracellular matrix resulting from cardiac surgery and the associated repair processes. The results indicate that FN has clinical potential as a marker of repair processes.

Salirasib Inhibits the Expression of Genes Involved in Fibrosis in Fibroblasts of Systemic Sclerosis Patients

BACKGROUND

Fibrosis is a principal sign of systemic sclerosis (SSc) which can affect several organs including the lung, heart, and dermis. Dermal fibroblasts of SSc patients are characterized by persistent and activated Ras and ERK1/2 signaling which stimulates extreme collagen and extracellular matrix synthesis. Salirasib is a Ras inhibitor that competitively prevents the adherence of GTP-bound Ras to the plasma membrane, that inhibits Ras signaling. This study intended to clarify whether salirasib can influence fibrotic mediators in SSc fibroblasts.

MATERIALS AND METHODS

Dermal fibroblasts from 10 SSc patients were treated with salirasib in the presence of TGF-β1, and mRNA levels of H-Ras and genes related to fibrosis, such as COL1A1, COL1A2, CTGF, TGF-β1, fibronectin, ACTA2, and MMP1 was measured by real-time PCR. The α-SMA protein expression was analyzed by immunofluorescence staining.

RESULTS

In dermal fibroblasts of SSc patients, salirasib treatment, markedly downregulated the H-Ras gene expression. In addition, the protein expression of α-SMA and gene expression of ACTA2 were inhibited upon salirasib treatment. Salirasib also significantly reduced the expression of COL1A1, and COL1A2 genes and augmented the gene expression of MMP1. The mRNA levels of other genes related to fibrosis such as FN1, CTGF, and TGF-β1 were significantly decreased upon salirasib treatment.

CONCLUSION

Considering salirasib significantly reduced the expression of genes related to the fibrosis process and α-SMA gene and protein expression, and given significant upregulation of MMP1 by salirasib, it can be considered as a new curative strategy for fibrotic diseases like SSc.

Intermanufacturer assessment of diagnostic performance of angiogenic ratio vs glycosylated fibronectin in women with suspected pre-eclampsia

OBJECTIVE

To compare the diagnostic performance of different manufacturers' immunoassays for the soluble fms-like tyrosine kinase-1 (sFlt-1)-to-placental growth factor (PlGF) ratio with that of a point-of-care (PoC) test for glycosylated fibronectin (GlyFn) in women with suspected pre-eclampsia (PE).

METHODS

This was a prospective, single-center, double-blinded, non-interventional study of East Asian women with a singleton pregnancy who presented with hypertension with or without clinical features of PE after 20 weeks' gestation between January 2020 and March 2022. Maternal serum samples were collected at the time of presentation, and subsequent management followed the departmental protocol, based on gestational age, severity of hypertension, fetal condition and presence of severe PE features. Women diagnosed with PE at presentation were excluded. PE was diagnosed according to the 2018 International Society for the Study of Hypertension in Pregnancy classification. Levels of sFlt-1 and PlGF were measured using the Cobas e411 (Roche Diagnostics), BRAHMS KRYPTOR (ThermoFisher Scientific) and iMAGIN 1800 (Ningbo Aucheer) platforms. GlyFn levels were measured using the Lumella™ GlyFn PoC test (DiabetOmics Inc.). The predictive performance of each test to rule out PE within 7 days and rule in PE within 28 days from the date of presentation was assessed. Based on the PROGNOSIS study, a sFlt-1/PlGF ratio of ≤ 38 on the Roche platform was used to predict the absence of PE within 7 days. The sFlt-1/PlGF ratio was classified as high or low using platform-specific thresholds equivalent to a Roche sFlt-1/PlGF ratio of 38, which were derived using Passing-Bablok regression. GlyFn was categorized as high or low using two reported clinical management thresholds (263 μg/mL and 510 μg/mL).

RESULTS

Overall, 236 women with suspected PE were included, of whom 70 (29.7%) were diagnosed with PE; 36 (51.4%) and 70 (100%) developed PE within 7 days and 28 days, respectively. Eighty-eight (37.3%) women had a sFlt-1/PlGF ratio of > 38 on the Roche platform, 79 (33.5%) women had a sFlt-1/PlGF ratio of > 55 on the KRYPTOR platform and 96 (40.7%) women had a sFlt-1/PlGF ratio of > 40 on the iMAGIN 1800 platform. Furthermore, 62 (26.3%) and four (1.7%) women had a GlyFn level of > 263 μg/mL and > 510 μg/mL, respectively. The negative predictive value (NPV) of the sFlt-1/PlGF ratio measured on the Roche, KRYPTOR and iMAGIN 1800 platforms to rule out PE within 7 days after presentation was 83.3%, 82.0% and 82.9%, respectively, while that for GlyFn > 263 μg/mL and > 510 μg/mL was 82.6% and 70.4%, respectively. The corresponding positive predictive values (PPV) to rule in PE within 28 days after presentation were 50.5%, 52.3% and 46.7%, respectively, for the sFlt-1/PlGF ratio, and 35.4% and 50.0%, respectively, for GlyFn > 263 μg/mL and > 510 μg/mL.

CONCLUSIONS

The predictive performance of different manufacturers' assays for the sFlt-1/PlGF ratio to rule in and rule out PE were similar once standardized to a common threshold. Our findings suggest that the sFlt-1/PlGF ratio and GlyFn using a cut-off of 263 μg/mL can both be utilized to rule out PE within 7 days after assessment, with a moderate NPV. The PPV for ruling in PE within 28 days remains poor. © 2024 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Impaired incorporation of fibronectin into the extracellular matrix during aging exacerbates the senescent state of dermal cells

Fibronectin (Fn) is a ubiquitous extracellular matrix (ECM) glycoprotein that acts as an ECM scaffold organizer and is essential in many biological functions, including tissue repair, differentiation or cancer dissemination. Evidence suggests that the amount of Fn changes during aging. However, how these changes influence the aging process remains unclear. This study aims to understand Fn influence on cell aging. First, we assess the relative level of Fn abundance in both different biopsies of skin donors and replicative senescence cellular model. In skin biopsies, we observed that Fn level decreases with aging in the reticular dermis, while its expression remains relatively stable in the papillary dermis, likely to sustain the dermis-epidermis junction. During replicative senescence, in BJ skin fibroblasts, while intracellular Fn increases, we found that secretion and Fn fibrils formation are less effective. Reduced Fn fibrils leads to disorganization of the ECM. This could be explained by the expression of different Fn isoforms observed in the secretome of senescent cells. Surprisingly, the knockdown of Fn delays the onset of senescence while cultivating cells onto a Fn-coated support promotes it. Taken together, these new insights on the role of Fn during aging may emerge new therapeutic strategies on aged-related diseases.

DAMPs Drive Fibroinflammatory Changes in the Glaucomatous ONH

Purpose

The optic nerve head (ONH) is well known to be the initial site of glaucomatous damage; however, the molecular mechanisms initiating this pathology are not fully understood. To further understand the initiating factors in glaucomatous damage we utilized a novel mouse model of glaucoma, B6.EDA+/+ mice, which constitutively express fibronectin containing the extra domain A (FN+EDA). FN+EDA is a known damage-associated molecular pattern (DAMP) that activates Toll-like receptor 4 and elicits a fibro-inflammatory response.

Methods

Eyes from B6.EDA+/+ and C57BL/6J mice were evaluated for retinal ganglion cell (RGC) death, retinal nerve fiber layer (RNFL) thickness, and optic nerve (ON) damage at 12 months and 22 months of age. ONH sections were isolated using laser capture microdissection for subsequent RNA-sequencing and Gene Set Enrichment Analysis (GSEA). GSEA results were confirmed using immunohistochemical (IHC) staining.

Results

B6.EDA+/+ mice exhibit significantly higher intraocular pressure, loss of RGCs, thinning of the RNFL, and progressive levels of ON damage at 12 months and 22 months of age compared to C57BL/6J controls. Protein expression of DAMPs FN+EDA and biglycan was significantly increased in B6.EDA+/+ mice compared to C57BL/6J controls. GSEA analysis identified significantly up- and downregulated gene groupings at both 12 months and 22 months of age, and IHC staining at 12 and 18 months of age demonstrated significant increases of IFNα, IFNβ, and pSTAT1 expression in B6.EDA+/+ mice compared to C57BL/6J controls.

Conclusions

Our study characterizes glaucomatous changes to the retina, ON, and ONH over the course of 2 years and identifies novel molecular pathways associated with these pathophysiological changes. These data illustrate the effects of FN+EDA on the fibro-inflammatory response in the aging ONH in a novel mouse model of glaucoma.

Ubiquitin-derived artificial binding proteins targeting oncofetal fibronectin reveal scaffold plasticity by β-strand slippage

Affilin proteins, artificial binding proteins based on the ubiquitin scaffold, have been generated by directed protein evolution to yield de-novo variants that bind the extra-domain B (EDB) of oncofetal fibronectin, an established marker of tumor neovasculature. The crystal structures of two EDB-specific Affilin variants reveal a striking structural plasticity of the ubiquitin scaffold, characterised by β-strand slippage, leading to different negative register shifts of the β5 strands. This process recruits amino acid residues from β5 towards the N-terminus to an adjacent loop region and subsequent residues into β5, respectively, remodeling the binding interface and leading to target specificity and affinity. Protein backbone alterations resulting from β-strand register shifts, as seen in the ubiquitin fold, can pose additional challenges to protein engineering as structural evidence of these events is still limited and they are difficult to predict. However, they can surface under the selection pressure of directed evolution and suggest that backbone plasticity allowing β-strand slippages can increase structural diversity, enhancing the evolutionary potential of a protein scaffold.

The integrin receptor beta7 subunit mediates airway remodeling and hyperresponsiveness in allergen exposed mice

BACKGROUND

Fibroblast differentiation to a myofibroblast phenotype is a feature of airway remodeling in asthma. Lung fibroblasts express the integrin receptor α4β7 and fibronectin induces myofibroblast differentiation via this receptor.

OBJECTIVES

To investigate the role of the β7 integrin receptor subunit and α4β7 integrin complex in airway remodeling and airway hyperresponsiveness (AHR) in a murine model of chronic allergen exposure.

METHODS

C57BL/6 wild type (WT) and β7 integrin null mice (β7 -/-) were sensitized (days 1,10) and challenged with ovalbumin (OVA) three times a week for one or 4 weeks. Similar experiments were performed with WT mice in the presence or absence of α4β7 blocking antibodies. Bronchoalveolar (BAL) cell counts, AHR, histological evaluation, soluble collagen content, Transforming growth factor-β (TGFβ) and Interleukin-13 (IL13) were measured. Phenotype of fibroblasts cultured from WT and β7 -/- saline (SAL) and OVA treated mice was evaluated.

RESULTS

Eosinophil numbers were similar in WT vs β7-/- mice. Prolonged OVA exposure in β7-/- mice was associated with reduced AHR, lung collagen content, peribronchial smooth muscle, lung tissue TGFβ and IL13 expression as compared to WT. Similar findings were observed in WT mice treated with α4β7 blocking antibodies. Fibroblast migration was enhanced in response to OVA in WT but not β7 -/- fibroblasts. α-SMA and fibronectin expression were reduced in β7-/- fibroblasts relative to WT.

CONCLUSIONS

The β7 integrin subunit and the α4β7 integrin complex modulate AHR and airway remodeling in a murine model of allergen exposure. This effect is, at least in part, explained by inhibition of fibroblast activation and is independent of eosinophilic inflammation.

Delivery technologies for therapeutic targeting of fibronectin in autoimmunity and fibrosis applications

Fibronectin (FN) is a critical component of the extracellular matrix (ECM) contributing to various physiological processes, including tissue repair and immune response regulation. FN regulates various cellular functions such as adhesion, proliferation, migration, differentiation, and cytokine release. Alterations in FN expression, deposition, and molecular structure can profoundly impact its interaction with other ECM proteins, growth factors, cells, and associated signaling pathways, thus influencing the progress of diseases such as fibrosis and autoimmune disorders. Therefore, developing therapeutics that directly target FN or its interaction with cells and other ECM components can be an intriguing approach to address autoimmune and fibrosis pathogenesis.

Diagnostic Accuracy of Serum Glycosylated Fibronectin in Prediction of Preeclampsia: A Nested Case-Control Study

BACKGROUND

Preeclampsia is a life-threatening complication of pregnancy that occurs in approximately 7% of all pregnancies. In India, the incidence of preeclampsia is 8%-10% and the prevalence is 5.4%, whereas the prevalence of hypertensive disorders of pregnancy is 7.8%.

AIM AND OBJECTIVES

This study was aimed at evaluating the diagnostic accuracy of serum glycosylated fibronectin (S. GlyFn) in the prediction of preeclampsia.

METHODS

A nested case-control study was carried out for 16 months in the department of obstetrics and gynecology. A total of 240 women were recruited and followed after written consent and ethical clearance. Six were lost to follow-up, 15 had second-trimester abortions (excluded from the study), and 32 women developed hypertensive disorders of pregnancy (cases), out of which 1 woman developed antepartum eclampsia, 10 women developed preeclampsia with severe features, and 21 women developed preeclampsia without severe features. One hundred and eighty-seven women remained normotensive throughout the pregnancy until 6 weeks postpartum. After randomization, out of these samples, 54 were analyzed and considered controls. Levels of S. GlyFn were estimated using an ELISA kit using the ELISA technique.

RESULTS

The mean S. GlyFn level was significantly higher at the time of enrollment among those women who later developed preeclampsia (127.59 ± 27.68 ng/m) as compared to controls (107.79-53.51 ng/mL). GlyFn at a cutoff value of 126.70 ng/mL significantly (P = 0.034) discriminates cases of preeclampsia with severe features from healthy controls with a sensitivity of 90.00%, a specificity of 63.00%, a 31.03% positive predictive value, and 97.14% negative predictive value.

CONCLUSION

S. GlyFn, at a cutoff value of 126.70 ng/mL, had good sensitivity to discriminate PE from normotensive and was also a good prognostic marker.

Astrocytic TIMP-1 regulates production of Anastellin, an inhibitor of oligodendrocyte differentiation and FTY720 responses

Astrocyte activation is associated with neuropathology and the production of tissue inhibitor of metalloproteinase-1 (TIMP1). TIMP1 is a pleiotropic extracellular protein that functions both as a protease inhibitor and as a growth factor. Astrocytes that lack expression of Timp1 do not support rat oligodendrocyte progenitor cell (rOPC) differentiation, and adult global Timp1 knockout (Timp1KO) mice do not efficiently remyelinate following a demyelinating injury. Here, we performed an unbiased proteomic analysis and identified a fibronectin-derived peptide called Anastellin (Ana) that was unique to the Timp1KO astrocyte secretome. Ana was found to block rOPC differentiation in vitro and enhanced the inhibitory influence of fibronectin on rOPC differentiation. Ana is known to act upon the sphingosine-1-phosphate receptor 1, and we determined that Ana also blocked the pro-myelinating effect of FTY720 (or fingolimod) on rOPC differentiation in vitro. Administration of FTY720 to wild-type C57BL/6 mice during MOG35-55-experimental autoimmune encephalomyelitis ameliorated clinical disability while FTY720 administered to mice lacking expression of Timp1 (Timp1KO) had no effect. Analysis of Timp1 and fibronectin (FN1) transcripts from primary human astrocytes from healthy and multiple sclerosis (MS) donors revealed lower TIMP1 expression was coincident with elevated FN1 in MS astrocytes. Last, analyses of proteomic databases of MS samples identified Ana peptides to be more abundant in the cerebrospinal fluid (CSF) of human MS patients with high disease activity. A role for Ana in MS as a consequence of a lack of astrocytic TIMP-1 production could influence both the efficacy of fingolimod responses and innate remyelination potential in the MS brain.

Mutations F352A and Y528A in human HSP90α reduce fibronectin association and fibrillogenesis in cell-derived matrices

HSP90 is a ubiquitously expressed chaperone protein that regulates the maturation of numerous substrate proteins called 'clients'. The glycoprotein fibronectin (FN) is an important protein of the extracellular matrix (ECM) and a client protein of HSP90. FN and HSP90 interact directly, and the FN ECM is regulated by exogenous HSP90 or HSP90 inhibitors. Here, we extend the analysis of the HSP90 - FN interaction. The importance of the N-terminal 70-kDa fragment of fibronectin (FN70) and FN type I repeat was demonstrated by competition for FN binding between HSP90 and the functional upstream domain (FUD) of the Streptococcus pyogenes F1 adhesin protein. Furthermore, His-HSP90α mutations F352A and Y528A (alone and in combination) reduced the association with full-length FN (FN-FL) and FN70 in vitro. Unlike wild type His-HSP90α, these HSP90 mutants did not enhance FN matrix assembly in the Hs578T cell line model when added exogenously. Interestingly, the HSP90 E353A mutation, which did not significantly reduce the HSP90 - FN interaction in vitro, dramatically blocked FN matrix assembly in Hs578T cell-derived matrices. Taken together, these data extend our understanding of the role of HSP90 in FN fibrillogenesis and suggest that promotion of FN ECM assembly by HSP90 is not solely regulated by the affinity of the direct interaction between HSP90 and FN.

Different roles of endothelial cell-derived fibronectin and plasma fibronectin in endothelial dysfunction

Background/aim

Atherosclerosis is significantly influenced by endothelial cell activation and dysfunction. Studies have demonstrated the substantial presence of fibronectin (Fn) within atherosclerotic plaques, promoting endothelial inflammation and activation. However, cellular Fn (cFn) secreted by various cell types, including endothelial cells and smooth muscle cells, and plasma Fn (pFn) produced by hepatocytes. They are distinct forms of Fn that differ in both structure and function. The specific contribution of different types of Fn in promoting endothelial cell activation and dysfunction remain uncertain. Therefore, this study aimed to investigate the respective roles of pFn and endothelial cell-derived Fn (FnEC) in promoting endothelial cell activation and dysfunction.

Materials and methods

Initially, endothelial cell injury was induced by exposing the cells to oxidized low-density lipoprotein (ox-LDL) and subsequently we generated a mutant strain of aortic endothelial cells with Fn knockdown (FnEC-KD). The impact of the FnEC-KD arel the addition of pFn on the expression levels of inflammatory factors, vasoconstrictors, and diastolic factors were compared.

Results

The results showed that the FnEC-KD significantly inhibited ox-LDL-induced intercellular adhesion molecule 1 (ICAM-1, p < 0.05), vascular cell adhesion molecule (VCAM-1, p < 0.05), and endothelin (p < 0.05) expression, and nuclear factor kappa-B (NFκB, p < 0.05) activation. These results implied that FnEC-KD inhibited both endothelial cell activation and dysfunction. Surprisingly, the addition of pFn significantly inhibited the ox-LDL-induced ICAM-1 (p < 0.05), VCAM-1 (p < 0.05), and endothelin (p < 0.05) expression and NFκB (p < 0.05) activation. Implying that pFn inhibits endothelial cell activation and dysfunction. Additionally, the study revealed that ox-LDL stimulation enhanced the production of excessive nitric oxide, leading to severe endothelial cell damage.

Conclusion

Aortic FnEC promotes endothelial cell activation and endothelial dysfunction, whereas pFn inhibits ox-LDL-induced endothelial cell activation and endothelial dysfunction.

Extracellular Matrix-Derived Damage-Associated Molecular Patterns (DAMP): Implications in Systemic Sclerosis and Fibrosis

Damage-associated molecular patterns (DAMPs) are intracellular molecules released under cellular stress or recurring tissue injury, which serve as endogenous ligands for toll-like receptors (TLRs). Such DAMPs are either actively secreted by immune cells or passively released into the extracellular environment from damaged cells or generated as alternatively spliced mRNA variants of extracellular matrix (ECM) glycoproteins. When recognized by pattern recognition receptors (PRRs) such as TLRs, DAMPs trigger innate immune responses. Currently, the best-characterized PRRs include, in addition to TLRs, nucleotide-binding oligomerization domain-like receptors, RIG-I-like RNA helicases, C-type lectin receptors, and many more. Systemic sclerosis (SSc) is a chronic autoimmune condition characterized by inflammation and progressive fibrosis in multiple organs. Using an unbiased survey for SSc-associated DAMPs, we have identified the ECM glycoproteins fibronectin-containing extra domain A and tenascin C as the most highly upregulated in SSc skin and lung biopsies. These DAMPs activate TLR4 on resident stromal cells to elicit profibrotic responses and sustained myofibroblasts activation resulting in progressive fibrosis. This review summarizes the current understanding of the complex functional roles of DAMPs in the progression and failure of resolution of fibrosis in general, with a particular focus on SSc, and considers viable therapeutic approaches targeting DAMPs.

Glycosylated fibronectin improves first-trimester prediction of pre-eclampsia

OBJECTIVE

To determine whether maternal serum glycosylated fibronectin (GlyFn) level in the first trimester increases the sensitivity of the Fetal Medicine Foundation (FMF) triple test, which incorporates mean arterial pressure, uterine artery pulsatility index and placental growth factor, when screening for pre-eclampsia (PE) in an Asian population.

METHODS

This was a nested case-control study of Chinese women with a singleton pregnancy who were screened for PE at 11-13 weeks' gestation as part of a non-intervention study between December 2016 and June 2018. GlyFn levels were measured retrospectively in archived serum from 1685 pregnancies, including 101 with PE, using an enzyme-linked immunosorbent assay (ELISA), and from 448 pregnancies, including 101 with PE, using a point-of-care (POC) device. Concordance between ELISA and POC tests was assessed using Lin's correlation coefficient and Passing-Bablok and Bland-Altman analyses. GlyFn was transformed into multiples of the median (MoM) to adjust for maternal and pregnancy characteristics. GlyFn MoM was compared between PE and non-PE pregnancies, and the association between GlyFn MoM and gestational age at delivery with PE was assessed. Risk for developing PE was estimated using the FMF competing-risks model. Screening performance for preterm and any-onset PE using different biomarker combinations was quantified by area under the receiver-operating-characteristics curve (AUC) and detection rate (DR) at a 10% fixed false-positive rate (FPR). Differences in AUC between biomarker combinations were compared using the DeLong test.

RESULTS

The concordance correlation coefficient between ELISA and POC measurements was 0.86 (95% CI, 0.83-0.88). Passing-Bablok analysis indicated proportional bias (slope, 1.08 (95% CI, 1.04-1.14)), with POC GlyFn being significantly higher compared with ELISA GlyFn. ELISA GlyFn in non-PE pregnancies was independent of gestational age at screening (P = 0.11), but significantly dependent on maternal age (P < 0.003), weight (P < 0.0002), height (P = 0.001), parity (P < 0.02) and smoking status (P = 0.002). Compared with non-PE pregnancies, median GlyFn MoM using ELISA and POC testing was elevated significantly in those with preterm PE (1.23 vs 1.00; P < 0.0001 and 1.18 vs 1.00; P < 0.0001, respectively) and those with term PE (1.26 vs 1.00; P < 0.0001 and 1.22 vs 1.00; P < 0.0001, respectively). GlyFn MoM was not correlated with gestational age at delivery with PE (P = 0.989). Adding GlyFn to the FMF triple test for preterm PE increased significantly the AUC from 0.859 to 0.896 (P = 0.012) and increased the DR at 10% FPR from 64.9% (95% CI, 48.7-81.1%) to 82.9% (95% CI, 66.4-93.4%). The corresponding DRs at 10% FPR for any-onset PE were 52.5% (95% CI, 42.3-62.5%) and 65.4% (95% CI, 55.2-74.5%), respectively.

CONCLUSIONS

Adding GlyFn to the FMF triple test increased the screening sensitivity for both preterm and any-onset PE in an Asian population. Prospective non-intervention studies are needed to confirm these initial findings. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Cooperative and competitive regulation of the astrocytic transcriptome by neurons and endothelial cells: Impact on astrocyte maturation

Astrocytes have essential roles in central nervous system (CNS) health and disease. During development, immature astrocytes show complex interactions with neurons, endothelial cells, and other glial cell types. Our work and that of others have shown that these interactions are important for astrocytic maturation. However, whether and how these cells work together to control this process remains poorly understood. Here, we test the hypothesis that cooperative interactions of astrocytes with neurons and endothelial cells promote astrocytic maturation. Astrocytes were cultured alone, with neurons, endothelial cells, or a combination of both. This was followed by astrocyte sorting, RNA sequencing, and bioinformatic analysis to detect transcriptional changes. Across culture configurations, 7302 genes were differentially expressed by 4 or more fold and organized into 8 groups that demonstrate cooperative and antagonist effects of neurons and endothelia on astrocytes. We also discovered that neurons and endothelial cells caused splicing of 200 and 781 mRNAs, respectively. Changes in gene expression were validated using quantitative PCR, western blot (WB), and immunofluorescence analysis. We found that the transcriptomic data from the three-culture configurations correlated with protein expression of three representative targets (FAM107A, GAT3, and GLT1) in vivo. Alternative splicing results also correlated with cortical tissue isoform representation of a target (Fibronectin 1) at different developmental stages. By comparing our results to published transcriptomes of immature and mature astrocytes, we found that neurons or endothelia shift the astrocytic transcriptome toward a mature state and that the presence of both cell types has a greater effect on maturation than either cell alone. These results increase our understanding of cellular interactions/pathways that contribute to astrocytic maturation. They also provide insight into how alterations to neurons and/or endothelial cells may alter astrocytes with implications for astrocytic changes in CNS disorders and diseases.

Evaluating Dual-Targeted ECO/siRNA Nanoparticles against an Oncogenic lncRNA for Triple Negative Breast Cancer Therapy with Magnetic Resonance Molecular Imaging

Differentiation antagonizing noncoding RNA (DANCR) is recognized as an oncogenic long noncoding RNA (lncRNA) overexpressed in triple negative breast cancer (TNBC). We showed in a previous study that RNAi with targeted multifunctional ionizable lipid ECO/siRNA nanoparticles was effective to regulate this undruggable target for effective treatment of TNBC. In this study, we developed dual-targeted ECO/siDANCR nanoparticles by targeting a tumor extracellular matrix oncoprotein, extradomain B fibronectin (EDB-FN), and integrins overexpressed on cancer cells for enhanced delivery of siDANCR. The treatment of Hs578T TNBC cells and MCF-7 estrogen receptor-positive cells in vitro resulted in significant down-regulation of DANCR and EDB-FN and suppressed invasion and 3D spheroid formation of the cells. Magnetic resonance molecular imaging (MRMI) with an EDB-FN-targeted contrast agent, MT218, was used to noninvasively evaluate tumor response to treatment with the targeted ECO/siDANCR nanoparticles in female nude mice bearing orthotopic Hs578T and MCF-7 xenografts. MRMI with MT218 was effective to differentiate between aggressive TNBC with high DANCR and EDB-FN expression and ER+ MCF-7 tumors with low expression of the targets. MRMI showed that the dual-targeted ECO/siDANCR nanoparticles resulted in more significant inhibition of tumor growth in both models than the controls and significantly reduced EDB-FN expression in the TNBC tumors. The combination of MRMI and dual-targeted ECO/siDANCR nanoparticles is a promising approach for image-guided treatment of TNBC by regulating the onco-lncRNA.

The Fibro-Inflammatory Response in the Glaucomatous Optic Nerve Head

Glaucoma is a progressive disease and the leading cause of irreversible blindness. The limited therapeutics available are only able to manage the common risk factor of glaucoma, elevated intraocular pressure (IOP), indicating a great need for understanding the cellular mechanisms behind optic nerve head (ONH) damage during disease progression. Here we review the known inflammatory and fibrotic changes occurring in the ONH. In addition, we describe a novel mechanism of toll-like receptor 4 (TLR4) and transforming growth factor beta-2 (TGFβ2) signaling crosstalk in the cells of the ONH that contribute to glaucomatous damage. Understanding molecular signaling within and between the cells of the ONH can help identify new drug targets and therapeutics.

Coalescent RNA-localizing and transcriptional activities of SAM68 modulate adhesion and subendothelial basement membrane assembly

Endothelial cell interactions with their extracellular matrix are essential for vascular homeostasis and expansion. Large-scale proteomic analyses aimed at identifying components of integrin adhesion complexes have revealed the presence of several RNA binding proteins (RBPs) of which the functions at these sites remain poorly understood. Here, we explored the role of the RBP SAM68 (Src associated in mitosis, of 68 kDa) in endothelial cells. We found that SAM68 is transiently localized at the edge of spreading cells where it participates in membrane protrusive activity and the conversion of nascent adhesions to mechanically loaded focal adhesions by modulation of integrin signaling and local delivery of β-actin mRNA. Furthermore, SAM68 depletion impacts cell-matrix interactions and motility through induction of key matrix genes involved in vascular matrix assembly. In a 3D environment SAM68-dependent functions in both tip and stalk cells contribute to the process of sprouting angiogenesis. Altogether, our results identify the RBP SAM68 as a novel actor in the dynamic regulation of blood vessel networks.

Strategic outline of interventions targeting extracellular matrix for promoting healthy longevity

The extracellular matrix (ECM), composed of interlinked proteins outside of cells, is an important component of the human body that helps maintain tissue architecture and cellular homeostasis. As people age, the ECM undergoes changes that can lead to age-related morbidity and mortality. Despite its importance, ECM aging remains understudied in the field of geroscience. In this review, we discuss the core concepts of ECM integrity, outline the age-related challenges and subsequent pathologies and diseases, summarize diagnostic methods detecting a faulty ECM, and provide strategies targeting ECM homeostasis. To conceptualize this, we built a technology research tree to hierarchically visualize possible research sequences for studying ECM aging. This strategic framework will hopefully facilitate the development of future research on interventions to restore ECM integrity, which could potentially lead to the development of new drugs or therapeutic interventions promoting health during aging.

IsoTools: a flexible workflow for long-read transcriptome sequencing analysis

MOTIVATION

Long-read transcriptome sequencing (LRTS) has the potential to enhance our understanding of alternative splicing and the complexity of this process requires the use of versatile computational tools, with the ability to accommodate various stages of the workflow with maximum flexibility.

RESULTS

We introduce IsoTools, a Python-based LRTS analysis framework that offers a wide range of functionality for transcriptome reconstruction and quantification of transcripts. Furthermore, we integrate a graph-based method for identifying alternative splicing events and a statistical approach based on the beta-binomial distribution for detecting differential events. To demonstrate the effectiveness of our methods, we applied IsoTools to PacBio LRTS data of human hepatocytes treated with the histone deacetylase inhibitor valproic acid. Our results indicate that LRTS can provide valuable insights into alternative splicing, particularly in terms of complex and differential splicing patterns, in comparison to short-read RNA-seq.

AVAILABILITY AND IMPLEMENTATION

IsoTools is available on GitHub and PyPI, and its documentation, including tutorials, CLI, and API references, can be found at https://isotools.readthedocs.io/.

A positive feedback loop driven by fibronectin and IL-1β sustains the inflammatory microenvironment in breast cancer

Inflammatory alterations of the extracellular matrix shape the tumor microenvironment and promote all stages of carcinogenesis. This study aims to determine the impact of cellular fibronectin on inflammatory facets of tumor-associated macrophages (TAMs) in breast cancer. Cellular fibronectin (FN) harboring the alternatively spliced extra domain A (FN-EDA) was determined to be a matrix component produced by the triple-negative breast cancer (TNBC) cells. High levels of FN-EDA correlated with poor survival in breast cancer patients. The proinflammatory cytokine IL-1β enhanced the expression of cellular fibronectin including FN-EDA. TAMs were frequently observed in the tumor areas rich in FN-EDA. Conditioned media from TNBC cells induced the differentiation of CD206⁺CD163⁺ macrophages and stimulated the STAT3 pathway, ex vivo. In the macrophages, the STAT3 pathway enhanced FN-EDA-induced IL-1β secretion and NF-κB signaling. In conclusion, our data indicate a self-reinforcing mechanism sustained by FN-EDA and IL-1β through NF-κB and STAT3 signaling in TAMs which fosters an inflammatory environment in TNBC.

Targeted Interleukin-9 delivery in pulmonary hypertension: Comparison of immunocytokine formats and effector cell study

AIMS

Pulmonary hypertension (PH) is accompanied by pulmonary vascular remodelling. By targeted delivery of Interleukin-9 (IL9) via the immunocytokine F8IL9, beneficial effects could be demonstrated in a mouse model of PH. This study aimed to compare two immunocytokine formats (single-chain Fv and full IgG) and to identify potential target cells of IL9.

METHODS

The Monocrotaline mouse model of PH (PH, n = 12) was chosen to evaluate the treatment effects of F8IL9F8 (n = 12) and F8IgGIL9 (n = 6) compared with sham-induced animals (control, n = 10), the dual endothelin receptor antagonist Macitentan (MAC, n = 12) or IL9-based immunocytokines with irrelevant antigen specificity (KSFIL9KSF, n = 12; KSFIgGIL9 n = 6). Besides comparative validation of treatment effects, the study was focused on the detection and quantification of mast cells (MCs) and regulatory T cells (Tregs).

RESULTS

There was a significantly elevated systolic right ventricular pressure (104 ± 36 vs. 45 ± 17 mmHg) and an impairment of right ventricular echocardiographic parameters (RVbasal: 2.52 ± 0.25 vs. 1.94 ± 0.13 mm) in untreated PH compared with controls (p < 0.05). Only the groups treated with F8IL9, irrespective of the format, showed consistent beneficial effects (p < 0.05). Moreover, F8IL9F8 but not F8IgGIL9 treatment significantly reduced lung tissue damage compared with untreated PH mice (p < 0.05). There was a significant increase in Tregs in F8IL9-treated compared with control animals, the untreated PH and the MAC group (p < 0.05).

CONCLUSIONS

Beneficial treatment effects of targeted IL9 delivery in a preclinical model of PH could be convincingly validated. IL9-mediated recruitment of Tregs into lung tissue might play a crucial role in the induction of anti-inflammatory and anti-proliferative mechanisms potentially contributing to a novel disease-modifying concept.

RNA-Seq Analysis of Extradomain A and Extradomain B Fibronectin as Extracellular Matrix Markers for Cancer

Alternatively spliced forms of fibronectin, called oncofetal fibronectin, are aberrantly expressed in cancer, with little to no expression in normal tissue, making them attractive biomarkers to exploit for tumor-targeted therapeutics and diagnostics. While prior studies have explored oncofetal fibronectin expression in limited cancer types and limited sample sizes, no studies have performed a large-scale pan-cancer analysis in the context of clinical diagnostics and prognostics to posit the utility of these biomarkers across multiple cancer types. In this study, RNA-Seq data sourced from the UCSC Toil Recompute project were extracted and analyzed to determine the correlation between the expression of oncofetal fibronectin, including extradomain A and extradomain B fibronectin, and patient diagnosis and prognosis. We determined that oncofetal fibronectin is significantly overexpressed in most cancer types relative to corresponding normal tissues. In addition, strong correlations exist between increasing oncofetal fibronectin expression levels and tumor stage, lymph node activity, and histological grade at the time of diagnosis. Furthermore, oncofetal fibronectin expression is shown to be significantly associated with overall patient survival within a 10-year window. Thus, the results presented in this study suggest oncofetal fibronectin as a commonly upregulated biomarker in cancer with the potential to be used for tumor-selective diagnosis and treatment applications.

Astrocytic TIMP-1 regulates production of Anastellin, a novel inhibitor of oligodendrocyte differentiation and FTY720 responses

Astrocyte activation is associated with neuropathology and the production of tissue inhibitor of metalloproteinase-1 (TIMP1). TIMP1 is a pleiotropic extracellular protein that functions both as a protease inhibitor and as a growth factor. We have previously demonstrated that murine astrocytes that lack expression of Timp1 do not support rat oligodendrocyte progenitor cell (rOPC) differentiation, and adult global Timp1 knockout ( Timp1 KO ) mice do not efficiently remyelinate following a demyelinating injury. To better understand the basis of this, we performed unbiased proteomic analyses and identified a fibronectin-derived peptide called anastellin that is unique to the murine Timp1 KO astrocyte secretome. Anastellin was found to block rOPC differentiation in vitro and enhanced the inhibitory influence of fibronectin on rOPC differentiation. Anastellin is known to act upon the sphingosine-1-phosphate receptor 1 (S1PR1), and we determined that anastellin also blocked the pro-myelinating effect of FTY720 (or fingolimod) on rOPC differentiation in vitro . Further, administration of FTY720 to wild-type C57BL/6 mice during MOG 35-55 -EAE ameliorated clinical disability while FTY720 administered to mice lacking expression of Timp1 in astrocytes ( Timp1 cKO ) had no effect. Analysis of human TIMP1 and fibronectin ( FN1 ) transcripts from healthy and multiple sclerosis (MS) patient brain samples revealed an inverse relationship where lower TIMP1 expression was coincident with elevated FN1 in MS astrocytes. Lastly, we analyzed proteomic databases of MS samples and identified anastellin peptides to be more abundant in the cerebrospinal fluid (CSF) of human MS patients with high versus low disease activity. The prospective role for anastellin generation in association with myelin lesions as a consequence of a lack of astrocytic TIMP-1 production could influence both the efficacy of fingolimod responses and the innate remyelination potential of the the MS brain.

Significance Statement

Astrocytic production of TIMP-1 prevents the protein catabolism of fibronectin. In the absence of TIMP-1, fibronectin is further digested leading to a higher abundance of anastellin peptides that can bind to sphingosine-1-phosphate receptor 1. The binding of anastellin with the sphingosine-1-phosphate receptor 1 impairs the differentiation of oligodendrocytes progenitor cells into myelinating oligodendrocytes in vitro , and negates the astrocyte-mediated therapeutic effects of FTY720 in the EAE model of chronic CNS inflammation. These data indicate that TIMP-1 production by astrocytes is important in coordinating astrocytic functions during inflammation. In the absence of astrocyte produced TIMP-1, elevated expression of anastellin may represent a prospective biomarker for FTY720 therapeutic responsiveness.

Recent Progress on the Role of Fibronectin in Tumor Stromal Immunity and Immunotherapy

As a major component of the stromal microenvironment of various solid tumors, the extracellular matrix (ECM) has attracted increasing attention in cancer-related studies. ECM in the tumor stroma not only provides an external barrier and framework for tumor cell adhesion and movement, but also acts as an active regulator that modulates the tumor microenvironment, including stromal immunity. Fibronectin (Fn), as a core component of the ECM, plays a key role in the assembly and remodeling of the ECM. Hence, understanding the role of Fn in the modulation of tumor stromal immunity is of great importance for cancer immunotherapy. Hence, in-depth studies on the underlying mechanisms of Fn in tumors are urgently needed to clarify the current understanding and issues and to identify new and specific targets for effective diagnosis and treatment purposes. In this review, we summarize the structure and role of Fn, its potent derivatives in tumor stromal immunity, and their biological effects and mechanisms in tumor development. In addition, we discuss the novel applications of Fn in tumor treatment. Therefore, this review can provide prospective insight into Fn immunotherapeutic applications in tumor treatment.

Elevated plasma EDA fibronectin in primary myelofibrosis is determined by high allele burden of JAK2V617F mutation and strongly predicts splenomegaly progression

In primary myelofibrosis, extra-domain A fibronectin (EDA-FN), the result of alternative splicing of FN gene, sustains megakaryocyte proliferation and confers a pro-inflammatory phenotype to bone marrow cell niches. In this work we assessed the levels of circulating EDA-FN in plasma samples of 122 patients with primary myelofibrosis. Patients with a homozygous JAK2V617F genotype displayed the higher level of plasma EDA-FN. Increased EDA-FN levels were associated with anemia, elevated high-sensitivity C-reactive protein, bone marrow fibrosis and splanchnic vein thrombosis at diagnosis. While no correlation was observed with CD34+ hematopoietic stem cell mobilization, elevated blood level of EDA-FN at diagnosis was a predictor of large splenomegaly (over 10 cm from the left costal margin) outcome. Thus, EDA-FN expression in primary myelofibrosis may represent the first marker of disease progression, and a novel target to treat splenomegaly.

Explainable Artificial Intelligence Helps in Understanding the Effect of Fibronectin on Survival of Sepsis

Fibronectin (FN) plays an essential role in the host’s response to infection. In previous studies, a significant decrease in the FN level was observed in sepsis; however, it has not been clearly elucidated how this parameter affects the patient’s survival. To better understand the relationship between FN and survival, we utilized innovative approaches from the field of explainable machine learning, including local explanations (Break Down, Shapley Additive Values, Ceteris Paribus), to understand the contribution of FN to predicting individual patient survival. The methodology provides new opportunities to personalize informative predictions for patients. The results showed that the most important indicators for predicting survival in sepsis were INR, FN, age, and the APACHE II score. ROC curve analysis showed that the model’s successful classification rate was 0.92, its sensitivity was 0.92, its positive predictive value was 0.76, and its accuracy was 0.79. To illustrate these possibilities, we have developed and shared a web-based risk calculator for exploring individual patient risk. The web application can be continuously updated with new data in order to further improve the model.

Toll-Like Receptor 4 Signaling in the Trabecular Meshwork

Primary open-angle glaucoma is one of the leading causes of blindness worldwide. With limited therapeutics targeting the pathogenesis at the trabecular meshwork (TM), there is a great need for identifying potential new targets. Recent evidence has implicated Toll-like receptor 4 (TLR4) and it is signaling pathway in augmenting the effects of transforming growth factor beta-2 (TGFβ2) and downstream extracellular matrix production. In this review, we examine the role of TLR4 signaling in the trabecular meshwork and the interplay between endogenous activators of TLR4 (damage-associated molecular patterns (DAMPs)), extracellular matrix (ECM), and the effect on intraocular pressure.

Fibronectin isoforms in skeletal development and associated disorders

The extracellular matrix is an intricate and essential network of proteins and non-proteinaceous components that provide a conducive microenvironment for cells to regulate cell function, differentiation, and survival. Fibronectin is one key component in the extracellular matrix that participates in determining cell fate and function crucial for normal vertebrate development. Fibronectin undergoes time dependent expression patterns during stem cell differentiation, providing a unique stem cell niche. Mutations in fibronectin have been recently identified to cause a rare form of skeletal dysplasia with scoliosis and abnormal growth plates. Even though fibronectin has been extensively analyzed in developmental processes, the functional role and importance of this protein and its various isoforms in skeletal development remains less understood. This review attempts to provide a concise and critical overview of the role of fibronectin isoforms in cartilage and bone physiology and associated pathologies. This will facilitate a better understanding of the possible mechanisms through which fibronectin exerts its regulatory role on cellular differentiation during skeletal development. The review discusses the consequences of mutations in fibronectin leading to corner fracture type spondylometaphyseal dysplasia and presents a new outlook towards matrix-mediated molecular pathways in relation to therapeutic and clinical relevance.

Fibronectin containing alternatively spliced extra domain A interacts at the central and c-terminal domain of Toll-like receptor-4

Extra domain A of cellular fibronectin (FN-EDA) is known to cause insulin resistance, atherosclerosis, tissue fibrosis, ischemic stroke and exaggerated myocardial reperfusion injury through Toll-like receptor 4 (TLR4). However, the FN-EDA-TLR4 interacting site is not well established. Therefore, in-silico approaches have been used to study FN-EDA and TLR4 interactions at the interface. In the present study, molecular docking studies of FN-EDA with TLR4-myeloid differentiation factor 2 (MD2) heterodimer have been performed to unravel the FN-EDA-TLR4 interacting sequence. Furthermore, the modulatory role of FN-EDA adjacent domains FNIII(11) and FNIII(12) on its interaction with TLR4-MD2 was investigated. The results show that FN-EDA interacting sequence “SPEDGIRELF” selectively interacts with TLR4 directly near its central and C-terminal domain region. The regulatory domains, FN type III 11 facilitate and 12 impede the FN-EDA-TLR4 interaction. Furthermore, the molecular dynamic simulation studies confirmed that FN-EDA forms a stable complex with TLR4-MD2 heterodimer. In conclusion, FN-EDA interacts and forms a stable complex through its “SPEDGIRELF” sequence at the central and C-terminal domain region of TLR4. The revelation of FN-EDA and TLR4 interacting sites may help design novel therapeutics for drug discovery research.

Fibronectin extra domain A (FN-EDA) causes glaucomatous trabecular meshwork, retina, and optic nerve damage in mice

BACKGROUND

Elevated intraocular pressure (IOP) is a major risk factor for the development and progression of primary open angle glaucoma and is due to trabecular meshwork (TM) damage. Here, we investigate the role of an endogenous Toll-like receptor 4 (TLR4) ligand, FN-EDA, in the development of glaucoma utilizing a transgenic mouse strain (B6.EDA+/+) that constitutively expresses only FN containing the EDA isoform.

METHODS

Eyes from C57BL6/J (wild-type), B6.EDA+/+ (constitutively active EDA), B6.EDA-/- (EDA null) mice were processed for electron microscopy and consecutive images of the entire length of the TM and Schlemm's canal (SC) from anterior to posterior were collected and montaged into a single image. ECM accumulation, basement membrane length, and size and number of giant vacuoles were quantified by ImageJ analysis. Tlr4 and Iba1 expression in the TM and ONH cells was conducted using RNAscope in situ hybridization and immunohistochemistry protocols. IOP was measured using a rebound tonometer, ON damage assessed by PPD stain, and RGC loss quantified in RBPMS labeled retina flat mounts.

RESULTS

Ultrastructure analyses show the TM of B6.EDA+/+ mice have significantly increased accumulation of ECM between TM beams with few empty spaces compared to C57BL/6 J mice (p < 0.05). SC basement membrane is thicker and more continuous in B6.EDA+/+ mice compared to C57BL/6 J. No significant structural differences are detected in the TM of EDA null mice. Tlr4 and Iba1 expression is increased in the TM of B6.EDA+/+ mice compared to C57BL/6 J eyes (p < 0.05). IOP is significantly higher in B6.EDA+/+ mice compared to C57BL/6 J eyes (p < 0.001), and significant ON damage (p < 0.001) and RGC loss (p < 0.05) detected at 1 year of age. Tlr4 mRNA is expressed in mouse ONH cells, and is present in ganglion cell axons, microglia, and astrocytes. There is a significant increase in the area occupied by Iba-1 positive microglia cells in the ONH of B6.EDA+/+ mice compared to C57BL/6 J control eyes (p < 0.01).

CONCLUSIONS

B6.EDA+/+ mice have increased ECM accumulation in the TM, elevated IOP, enhanced proinflammatory changes in the ONH, loss of RGCs, and ONH damage. These data suggest B6.EDA+/+ mice recapitulate many aspects of glaucomatous damage.

Speciomics as a concept involving chemical speciation and omics

The study of chemical speciation and the refinement and expansion of omics-based methods are both consolidated and highly active research fields. Although well established, such fields are extremely dynamic and are driven by the emergence of new strategies and improvements in instrumentation. In the case of omics-based studies, subareas including lipidomics, proteomics, metallomics, metabolomics and foodomics have emerged. Here, speciomics is being proposed as an "umbrella" term, that incorporates all of these subareas, to capture studies where the evaluation of chemical species is carried out using omics approaches. This paper contextualizes both speciomics and the speciome, and reviews omics applications used for species identification through examination of proteins, metalloproteins, metabolites, and nucleic acids. In addition, some implications from such studies and a perspective for future development of this area are provided. SIGNIFICANCE: The synergic effect between chemical speciation and omics is highlighted in this work, demonstrating an emerging area of research with a multitude of possibilities in terms of applications and further developments. This work not only defines and contextualizes speciomics and individual speciomes, but also demonstrates with some examples the great potential of this new interdisciplinary area of research.

Predictive value of the second-trimester fibronectin concentration for severe preeclampsia: A prospective nested case-control study in China

AIM

To evaluate the value of the second-trimester fibronectin concentration, alone and in combination with other markers (e.g., mean arterial pressure, inhibin A), in the identification of women who subsequently develop severe preeclampsia.

METHODS

For this prospective nested case-control study, serum from pregnant women (gestational age 15-22 weeks) who underwent routine Down syndrome screening was analyzed. The women were tracked to delivery and assigned to the severe preeclampsia or control group, according to whether they developed severe preeclampsia. Each woman who later developed severe preeclampsia was paired with five healthy women with pregnancies of similar gestational age (± 1 week). Fibronectin, inhibin A, human chorionic gonadotropin, placental growth factor, cysteine, and homocysteine concentrations were measured in 44 cases in the severe preeclampsia group and 220 cases in the control group. The body mass index and mean arterial pressure were calculated. All results were compared between the two groups. Logistic regression analysis and receiver operating characteristic curve construction were conducted for markers differing significantly between two groups.

RESULTS

The second-trimester fibronectin value was positively correlated with severe preeclampsia and predicted 67.7% of severe preeclampsia cases. The combination of fibronectin, inhibin A, and mean arterial pressure predicted 76.7% of severe preeclampsia cases; predictive values for combinations of fibronectin with mean arterial pressure or inhibin A were 75.4% and 74.6%, respectively. Combination with these other markers increased the predictive value of fibronectin. In addition, fibronectin was more powerful for the late severe preeclampsia and severe preeclampsia without fetal growth restriction subgroups.

CONCLUSIONS

The second-trimester fibronectin concentration can be used to predict severe preeclampsia.

Instructive Hydrogels for Primary Tumor Cell Culture: Current Status and Outlook

Primary tumor organoids (PTOs) growth in hydrogels have emerged as an important in vitro model that recapitulates many characteristics of the native tumor tissue, and have important applications in fundamental cancer research and for the development of useful therapeutic treatment. This paper begins with reviewing the methods of isolation of primary tumor cells. Then, recent advances on the instructive hydrogels as biomimetic extracellular matrix for primary tumor cell culture and construction of PTO models are summarized. Emerging microtechnology for growth of PTOs in microscale hydrogels and the applications of PTOs are highlighted. This paper concludes with an outlook on the future directions in the investigation of instructive hydrogels for PTO growth.

Transforming growth factor β latency: A mechanism of cytokine storage and signalling regulation in liver homeostasis and disease

Transforming growth factor-β (TGF-β) is a potent effector in the liver, which is involved in a plethora of processes initiated upon liver injury. TGF-β affects parenchymal, non-parenchymal, and inflammatory cells in a highly context-dependent manner. Its bioavailability is critical for a fast response to various insults. In the liver – and probably in other organs – this is made possible by the deposition of a large portion of TGF-β in the extracellular matrix as an inactivated precursor form termed latent TGF-β (L-TGF-β). Several matrisomal proteins participate in matrix deposition, latent complex stabilisation, and activation of L-TGF-β. Extracellular matrix protein 1 (ECM1) was recently identified as a critical factor in maintaining the latency of deposited L-TGF-β in the healthy liver. Indeed, its depletion causes spontaneous TGF-β signalling activation with deleterious effects on liver architecture and function. This review article presents the current knowledge on intracellular L-TGF-β complex formation, secretion, matrix deposition, and activation and describes the proteins and processes involved. Further, we emphasise the therapeutic potential of toning down L-TGF-β activation in liver fibrosis and liver cancer.

The extracellular matrix of hematopoietic stem cell niches

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Comprehensive overview of different classes of ECM molecules in the HSC niche.

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Overview of current knowledge on role of biophysics of the HSC niche.

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Description of approaches to create artificial stem cell niches for several application.

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Importance of considering ECM in drug development and testing.

Hematopoietic stem cells (HSCs) are the life-long source of all types of blood cells. Their function is controlled by their direct microenvironment, the HSC niche in the bone marrow. Although the importance of the extracellular matrix (ECM) in the niche by orchestrating niche architecture and cellular function is widely acknowledged, it is still underexplored. In this review, we provide a comprehensive overview of the ECM in HSC niches. For this purpose, we first briefly outline HSC niche biology and then review the role of the different classes of ECM molecules in the niche one by one and how they are perceived by cells. Matrix remodeling and the emerging importance of biophysics in HSC niche function are discussed. Finally, the application of the current knowledge of ECM in the niche in form of artificial HSC niches for HSC expansion or targeted differentiation as well as drug testing is reviewed.

B7-H3 inhibits apoptosis of gastric cancer cell by interacting with Fibronectin

Anti-apoptosis has been widely accepted as a hallmark of malignancy. B7-H3, a type I transmembrane protein, plays a key role in anti-apoptosis and immune escape, but its regulation during cancer development remains unclear. To investigate how the effect of anti-apoptosis is regulated by B7-H3 in gastric cancer, we stably knocked down B7-H3 gene by shRNA in MGC-803 and MKN-45 cells. The correlation between B7-H3 and Fibronectin (FN) expression were investigated by bioinformatics in public data from TCGA (The Cancer Genome Atlas). Here, we reported that B7-H3 expression is positively correlated with FN in clinical gastric cancer samples, and B7-H3 promoted adhesion and inhibited apoptosis of gastric cancer cell through an FN-dependent pathway. Mechanistically, B7-H3 interacted with FN and subsequently activated PI3K/AKT signaling pathway, a critical mediator of oncogenic signaling. In addition, exogenous FN could inhibit the expression of pro-apoptosis-related proteins such as Caspase 3, Caspase 8, Caspase 9, Bax , p53, Apaf-1 and Cleaved PARP, and upregulated the levels of signal molecule p-PI3K, p-AKT and anti-apoptotic proteins Bcl-2 in B7-H3^high group, as compared with those in B7-H3^low group. In conclusion, we here for the first time revealed that B7-H3 inhibits apoptosis of gastric cancer cell through regulation of FN-mediated PI3K/AKT signaling pathways.

Targeting the extracellular matrix for immunomodulation: applications in drug delivery and cell therapies

Host immune cells interact bi-directionally with their extracellular matrix (ECM) to receive and deposit molecular signals, which orchestrate cellular activation, proliferation, differentiation, and function to maintain healthy tissue homeostasis. In response to pathogens or damage, immune cells infiltrate diseased sites and synthesize critical ECM molecules such as glycoproteins, proteoglycans, and glycosaminoglycans to promote healing. When the immune system misidentifies pathogens or fails to survey damaged cells effectively, maladies such as chronic inflammation, autoimmune diseases, and cancer can develop. In these conditions, it is essential to restore balance to the body through modulation of the immune system and the ECM. This review details the components of dysregulated ECM implicated in pathogenic environments and therapeutic approaches to restore tissue homeostasis. We evaluate emerging strategies to overcome inflamed, immune inhibitory, and otherwise diseased microenvironments, including mechanical stimulation, targeted proteases, adoptive cell therapy, mechanomedicine, and biomaterial-based cell therapeutics. We highlight various strategies that have produced efficacious responses in both pre-clinical and human trials and identify additional opportunities to develop next-generation interventions. Significantly, we identify a need for therapies to address dense or fibrotic tissue for the treatment of organ tissue damage and various cancer subtypes. Finally, we conclude that therapeutic techniques that disrupt, evade, or specifically target the pathogenic microenvironment have a high potential for improving therapeutic outcomes and should be considered a priority for immediate exploration. A schematic showing the various methods of extracellular matrix disruption/targeting in both fibrotic and cancerous environments. a Biomaterial-based cell therapy can be used to deliver anti-inflammatory cytokines, chemotherapeutics, or other factors for localized, slow release of therapeutics. b Mechanotherapeutics can be used to inhibit the deposition of molecules such as collagen that affect stiffness. c Ablation of the ECM and target tissue can be accomplished via mechanical degradation such as focused ultrasound. d Proteases can be used to improve the distribution of therapies such as oncolytic virus. e Localization of therapeutics such as checkpoint inhibitors can be improved with the targeting of specific ECM components, reducing off-target effects and toxicity.

Bone marrow microenvironment of MPN cells

In this chapter, we will discuss the current knowledge concerning the alterations of the cellular components in the bone marrow niche in Myeloproliferative Neoplasms (MPNs), highlighting the central role of the megakaryocytes in MPN progression, and the extracellular matrix components characterizing the fibrotic bone marrow.

The RNA binding protein Quaking represses splicing of the Fibronectin EDA exon and downregulates the interferon response

Quaking (QKI) controls RNA metabolism in many biological processes including innate immunity, where its roles remain incompletely understood. To illuminate these roles, we performed genome scale transcriptome profiling in QKI knockout cells with or without poly(I:C) transfection, a double-stranded RNA analog that mimics viral infection. Analysis of RNA-sequencing data shows that QKI knockout upregulates genes induced by interferons, suggesting that QKI is an immune suppressor. Furthermore, differential splicing analysis shows that QKI primarily controls cassette exons, and among these events, we noted that QKI silences splicing of the extra domain A (EDA) exon in fibronectin (FN1) transcripts. QKI knockout results in elevated production and secretion of FN1-EDA protein, which is a known activator of interferons. Consistent with an upregulation of the interferon response in QKI knockout cells, our results show reduced production of dengue virus-2 and Japanese encephalitis virus in these cells. In conclusion, we demonstrate that QKI downregulates the interferon system and attenuates the antiviral state.

Targeted Delivery of Cabazitaxel Using Cyclic Cell-Penetrating Peptide and Biomarkers of Extracellular Matrix for Prostate and Breast Cancer Therapy

Targeted drug delivery for cancer therapy is an emerging area of research. Cancer cells overexpress certain biomarkers that can be exploited for their targeted therapy. Cyclic cell-penetrating peptides (cCPP) are increasingly assessed for intracellular cargo delivery in cancer cells. In this study, we have conjugated cabazitaxel (CBT) to the cCPP via an ester bond to assist CBT release in the tumor's acidic environment. Integrin targeting (RGDC, TP1) and extra domain B of fibronectin (EDB-Fn) targeting (CTVRTSAD, TP2) peptides were linked to the peptide-drug conjugate (cCPP-CBT) via a disulfide bond to provide targeting ability to the conjugates until they reach the tumor site. Conjugate 11 (TP1-cCPP-CBT) and conjugate 16 (TP2-cCPP-CBT) showed approximately 3-4-fold less antiproliferative activity on integrin and EDB-FN overexpressing cancer cell lines as compared to the CBT analogue used for comparison (CBT-GA, 5). Conjugates (11 and 16) were less toxic (31-34-fold less antiproliferative activity) to the normal human embryonic kidney (HEK-293) cells as compared to CBT. The flow cytometry and quantitative confocal microscopy data further confirm the selective efficacy of conjugates (TP1-cCPP-FAM (10) and TP1-cCPP-FAM (15)) toward biomarker overexpressing cancer cells. Furthermore, the stability and release studies of conjugate 11 revealed its therapeutic potential under different conditions, such as human plasma, different pHs, and redox conditions. This conjugation strategy was proven to enhance chemotherapeutics agents' efficacy and targeting and can be applied to other chemotherapeutic agents.

A story of fibers and stress: Matrix-embedded signals for fibroblast activation in the skin

Our skin is continuously exposed to mechanical challenge, including shear, stretch, and compression. The extracellular matrix of the dermis is perfectly suited to resist these challenges and maintain integrity of normal skin even upon large strains. Fibroblasts are the key cells that interpret mechanical and chemical cues in their environment to turnover matrix and maintain homeostasis in the skin of healthy adults. Upon tissue injury, fibroblasts and an exclusive selection of other cells become activated into myofibroblasts with the task to restore skin integrity by forming structurally imperfect but mechanically stable scar tissue. Failure of myofibroblasts to terminate their actions after successful repair or upon chronic inflammation results in dysregulated myofibroblast activities which can lead to hypertrophic scarring and/or skin fibrosis. After providing an overview on the major fibrillar matrix components in normal skin, we will interrogate the various origins of fibroblasts and myofibroblasts in the skin. We then examine the role of the matrix as signaling hub and how fibroblasts respond to mechanical matrix cues to restore order in the confusing environment of a healing wound.

Serum Liberation of Fetal Fibronectin Variants in Patients with Pulmonary Hypertension: ED-A+ Fn as Promising Novel Biomarker of Pulmonary Vascular and Right Ventricular Myocardial Remodeling

Background and Aims: Pulmonary Hypertension (PH) represents an aetiologically and clinically heterogeneous disorder accompanied by a severely impaired prognosis. Key steps of PH pathogenesis are vascular and right ventricular myocardial remodelling entailing the re-occurrence of fetal variants of the cell adhesion modulating protein fibronectin (Fn) being virtually absent in healthy adult tissues. These variants are liberated into circulation and are therefore qualified as excellent novel serum biomarkers. Moreover, these molecules might serve as promising therapeutic targets. The current study was aimed at quantifying the serum levels of two functionally important fetal Fn variants (ED-A⁺ and ED-B⁺ Fn) in patients suffering from PH due to different aetiologies compared to healthy controls. Methods: Serum levels of ED-A⁺ and ED-B⁺ Fn were quantified using novel ELISA protocols established and validated in our group in 80 PH patients and 40 controls. Results were analysed with respect to clinical, laboratory, echocardiographic and functional parameters. Results: Serum levels of ED-A⁺ Fn (p = 0.001) but not ED-B⁺ Fn (p = 0.722) were significantly increased in PH patients compared to healthy controls. Thus, the following analyses were performed only for ED-A⁺ Fn. When dividing PH patients into different aetiological groups according to current ESC guidelines, the increase in ED-A⁺ Fn in PH patients compared to controls remained significant for group 1 (p = 0.032), 2 (p = 0.007) and 3 (p = 0.001) but not for group 4 (p = 0.156). Correlation analysis revealed a significant relation between ED-A⁺ Fn and brain natriuretic peptide (BNP) (r = 0.310; p = 0.002), six minutes’ walk test (r = −0.275; p = 0.02) and systolic pulmonary artery pressure (PAPsys) (r = 0.364; p < 0.001). By logistic regression analysis (backward elimination WALD) including a variety of potentially relevant patients’ characteristics, only chronic kidney disease (CKD) (OR: 8.866; CI: 1.779–44.187; p = 0.008), C reactive protein (CRP) (OR: 1.194; CI: 1.011–1.410; p = 0.037) and ED-A⁺ Fn (OR: 1.045; CI: 1.011–1.080; p = 0.009) could be identified as independent predictors of the presence of PH. Conclusions: Against the background of our results, ED-A⁺ Fn could serve as a promising novel biomarker of PH with potential value for initial diagnosis and aetiological differentiation. Moreover, it might contribute to more precise risk stratification of PH patients. Beyond that, the future role of ED-A⁺ Fn as a therapeutic target has to be evaluated in further studies.

Fibronectin in Fracture Healing: Biological Mechanisms and Regenerative Avenues

The importance of extracellular matrix (ECM) proteins in mediating bone fracture repair is evident, and fibronectin (FN) has emerged as a pivotal regulator of this process. FN is an evolutionarily conserved glycoprotein found in all tissues of the body, and functions in several stages of fracture healing. FN acts as a three-dimensional scaffold immediately following trauma, guiding the assembly of additional ECM components. Furthermore, FN regulates cellular behavior via integrin-binding and growth factor-binding domains, promoting downstream responses including cell recruitment, proliferation and differentiation. Due to its diverse functions, the development of FN-based strategies to promote fracture healing is under intense research. In this review, we discuss the recent advancements in utilizing FN-based biomaterials, showing promise in tissue engineering and regenerative medicine applications.

Identification of fibronectin 1 as a candidate genetic modifier in a Col4a1 mutant mouse model of Gould syndrome

Collagen type IV alpha 1 and alpha 2 (COL4A1 and COL4A2) are major components of almost all basement membranes. COL4A1 and COL4A2 mutations cause a multisystem disorder that can affect any organ but typically involves the cerebral vasculature, eyes, kidneys and skeletal muscles. In recent years, patient advocacy and family support groups have united under the name of Gould syndrome. The manifestations of Gould syndrome are highly variable, and animal studies suggest that allelic heterogeneity and genetic context contribute to the clinical variability. We previously characterized a mouse model of Gould syndrome caused by a Col4a1 mutation in which the severities of ocular anterior segment dysgenesis (ASD), myopathy and intracerebral hemorrhage (ICH) were dependent on genetic background. Here, we performed a genetic modifier screen to provide insight into the mechanisms contributing to Gould syndrome pathogenesis and identified a single locus [modifier of Gould syndrome 1 (MoGS1)] on Chromosome 1 that suppressed ASD. A separate screen showed that the same locus ameliorated myopathy. Interestingly, MoGS1 had no effect on ICH, suggesting that this phenotype could be mechanistically distinct. We refined the MoGS1 locus to a 4.3 Mb interval containing 18 protein-coding genes, including Fn1, which encodes the extracellular matrix component fibronectin 1. Molecular analysis showed that the MoGS1 locus increased Fn1 expression, raising the possibility that suppression is achieved through a compensatory extracellular mechanism. Furthermore, we found evidence of increased integrin-linked kinase levels and focal adhesion kinase phosphorylation in Col4a1 mutant mice that is partially restored by the MoGS1 locus, implicating the involvement of integrin signaling. Taken together, our results suggest that tissue-specific mechanistic heterogeneity contributes to the variable expressivity of Gould syndrome and that perturbations in integrin signaling may play a role in ocular and muscular manifestations.