Lysyl oxidase is essential for normal development and function of the respiratory system and for the integrity of elastic and collagen fibers in various tissues

Tuning local matrix compliance accelerates mesenchymal stem cell chondrogenesis in 3D sliding hydrogels

The mechanical properties of the extracellular matrix critically regulate stem cell differentiation in 3D. Alginate hydrogels with tunable bulk stiffness and viscoelasticity can modulate differentiation in 3D through mechanotransduction. Such enhanced differentiation is correlated with changes in the local matrix compliance- the extent of matrix deformation under applied load. However, the causal effect of local matrix compliance changes without altering bulk hydrogel mechanics on stem cell differentiation remains unclear. To address this, we report sliding hydrogel (SG) designs with tunable local matrix compliance obtained by varying the molecular mobility of the hydrogel network without changing bulk mechanics. Atomic force microscopy showed increasing SG mobility allowed cells to increasingly deform local niches with lesser forces, indicating higher local matrix compliance. Increasing SG mobility accelerates MSC chondrogenesis in a mobility-dependent manner and is independent of exogenous adhesive ligands or cell volume expansion. The enhanced chondrogenesis in SG is accompanied by enhanced cytoskeletal organization and TRPV4 expression, and blocking these elements abolished the effect. In conclusion, this study establishes a causal link between local matrix compliance and stem cell differentiation and establishes it as a crucial hydrogel design parameter. Furthermore, it offers novel SG designs to probe the role of local matrix compliance in various biological processes.

Lysyl oxidase mediates regeneration of chondrocytes and extracellular matrix in the construction of tissue-engineered cartilage in vitro

Cartilage tissue engineering affords great promise for cartilage tissue regeneration in clinical practice. Unfortunately, in vitro engineered cartilage falls short of mechanical properties compared to natural cartilage, which has not yet become the mainstream of cartilage defect repair. Notably, the collagen fiber structure in the extracellular matrix (ECM) of chondrocytes accounts for the mechanical properties of engineered cartilage. Specifically, massive collagen fibers in ECM are covalently cross-linked by lysyl oxidase (LOX) to form a rigid cross-linked structure, contributing to certain mechanical properties. Accordingly, LOX may be a key enzyme for improving the mechanical properties of tissue-engineered cartilage in vitro. As reported, transforming growth factor-β1 (TGF-β1) can activate LOX via the SMAD-independent MAPK pathway, and β-aminopropionitrile (BAPN), an irreversible inhibitor of LOX, directly represses the cross-linking between macromolecules in the ECM of chondrocytes. In the present study, we intervened in cartilage regeneration in vitro using the aforementioned activator and inhibitor of LOX, thereby evaluating the quality and mechanical properties of tissue-engineered cartilage and further investigating the role of LOX in cartilage regeneration in vitro. Our results demonstrated that TGF-β1 improved the mechanical properties of cartilage in vitro at both two-dimensional and three-dimensional constructs by activating LOX. Therefore, further experimental studies are warranted to probe the activators of LOX and their mechanisms in cartilage regeneration in vitro.

Skeletal muscle activity affects the deformity of long bone morphology in lathyritic chick embryo

Embryonic muscle activity is involved in various aspects of bone morphogenesis and growth. Normal mechanical stimuli of muscle contraction are important in most cases, and when the muscles are immobilized, the developing bones are abnormally shaped. In chick embryos, a characteristic curved deformity is reproducibly induced in the developing tibiotarsus using the bone-weakening agent, beta-aminopropionitrile (bAPN). In this study, we applied decamethonium bromide (DMB), a well-established neuromuscular blocking agent, to embryos treated with bAPN, to test the hypothesis that the deformity is triggered and formed depending on the balance between the decrease in stiffness of the bAPN-affected tibiotarsus and the normal physiological increase in embryonic skeletal muscle activity. The occurrence of curved morphology induced by bAPN administered at 4 or 8 days of incubation (embryonic day [ED]) was temporally consistent with the posterior displacement of the leg muscles, which occurred just before ED8. The displaced muscles were assumed to exert a contraction force comparable to that of untreated normal muscles. When treated with DMB at ED8, the muscles atrophied and exhibited degenerative changes, and the degree of curved morphology was alleviated and reduced to 50% or more in the morphometric evaluation at ED10. These findings indicated that the coordinated development of skeletal element stiffness and muscle activity must be temporally regulated, particularly during the early stages of skeletogenesis.

An in vitro model to measure the strength and stiffness of the extracellular matrix synthesized de novo by human fibroblasts

Purpose

Alterations to the strength and stiffness of the human extracellular matrix (ECM) are the underlying pathology manifest in a wide range of diseases. These include inherited conditions, such as Ehlers Danlos syndrome, as well as acquired diseases such as fibrosis, which remains a major unmet medical need. To evaluate promising therapies, new models are needed that can measure the strength and stiffness of the human ECM.

Methods

Cultured human fibroblasts were seeded into circular troughs of agarose that had been molded into a 24 well plate and equilibrated with cell culture medium. The cells settled by gravity, aggregated and formed 3D ring-shaped tissues 5 mm in diameter without the aid of added exogenous scaffold material. The ECM proteins synthesized de novo by the rings were characterized by immuno-staining. The response of the rings to drug and growth factor treatments were assessed by measuring changes to the dimensions of the rings and by measuring levels of collagen. A tensile test was used to quantify drug and growth factor induced changes to the strength and stiffness of the rings.

Results

Ring-shaped tissues readily formed in the molds and synthesized de novo a circumferentially aligned collagen-rich fibrous ECM network positive for collagen type I, collagen type III and fibronectin. Low dose treatment with incyclinide, an inhibitor of matrix metalloproteinases (MMPs), increased strength and stiffness, whereas as a high dose decreased tensile properties, likely due to a toxic effect. Treatment with TGF-β1, a well-known driver of fibrosis, increased levels of collagen and tensile properties and mimicked the fibrotic environment in vitro. Treatment with PAT-1251, an inhibitor of the collagen crosslinking enzyme lysyl oxidase-like protein 2 (LOXL2), had no effect on levels of collagen but significantly reduced the strength and stiffness of the ring even when elevated by treatment with TGF-β1.

Conclusion

Human fibroblasts will self-assemble a 3D ring-shaped tissue and synthesize a fibrous network of ECM proteins whose tensile properties can be measured. The fibrotic environment can be mimicked by addition of TGF-β1, which increases levels of collagen as well as the strength and stiffness of the rings. Treatment with two drugs, incyclinide and PAT 1251 that were developed as potential treatments for diseases of the ECM, altered the strength and stiffness of the rings, thereby demonstrating the utility of the model for testing new therapies that target the biomechanics of the ECM.

Supplementary Information

The online version contains supplementary material available at 10.1007/s44164-025-00081-y.

Coordination among cytoskeletal organization, cell contraction, and extracellular matrix development is dependent on LOX for aneurysm prevention

Distinct and seemingly independent cellular pathways affecting intracellular machinery or extracellular matrix (ECM) deposition and organization have been implicated in aneurysm formation. One of the key genes associated with this pathology in both humans and mice is lysyl oxidase (LOX), a secreted ECM-modifying enzyme, highly expressed in medial vascular smooth muscle cells. To dissect the mechanisms leading to aneurysm development, we conditionally deleted Lox in smooth muscle cells. We find that cytoskeletal organization is lost following Lox deletion. Cell culture assays and in vivo analyses demonstrate a cell-autonomous role for LOX affecting myosin light-chain phosphorylation and cytoskeletal assembly resulting in irregular smooth muscle contraction. These results not only highlight new intracellular roles for LOX, but notably, they provide a link between multiple processes leading to aneurysm formation, suggesting LOX coordinates ECM development, cytoskeletal organization, and cell contraction required for media development and function.

Pulmonary lysyl oxidase expression and its role in seeding Lewis lung carcinoma cells

Copper promotes tumor growth and metastasis through a variety of mechanisms, most notably as a cofactor within the lysyl oxidase (LOX) family of secreted cuproenzymes. Members of this family, which include LOX and LOX-like enzymes LOXL1-4, catalyze the copper-dependent crosslinking of collagens and elastin within the extracellular matrix (ECM). Elevated LOX expression is associated with higher incidence and worse prognosis in multiple cancers, including colorectal, breast, pancreatic, and head and neck. In this study, we demonstrated that elevated LOX expression correlates with decreased overall survival and shorter median time to first progression in patients with lung cancer. Previous studies have demonstrated that LOX secreted from tumors is critical for pre-metastatic niche formation by promoting ECM remodeling and the recruitment of immune cells and endothelial precursors. Here, we demonstrated that ablation of the LOX gene in Lewis lung carcinoma (LLC) cells diminishes tumor growth and metastasis compared to wild-type LLC cells in a syngeneic mouse model. Although the role of tumor-derived LOX in tumor formation and metastasis is well established, little is known regarding the possible contribution of LOX produced by the parenchymal tissue of metastatic organs. Thus, this report describes our findings that host-derived LOX produced by the lung contributes to the pulmonary metastasis of LLC cells in mice. The suppression of pulmonary lysyl oxidase expression reduces the metastatic potential of Lewis Lung Carcinoma cells in mice, revealing a previously unknown influence of LOX expression in the parenchymal tissue of metastatic target organs on the seeding of tumor cells.

Lysyl Oxidase Mediates Proliferation and Differentiation in the Esophageal Epithelium

In homeostatic conditions, the basal progenitor cells of the esophagus differentiate into a stratified squamous epithelium. However, in the setting of acid exposure or inflammation, there is a marked failure of basal cell differentiation, leading to basal cell hyperplasia. We have previously shown that lysyl oxidase (LOX), a collagen crosslinking enzyme, is upregulated in the setting of allergic inflammation of the esophagus; however, its role beyond collagen crosslinking is unknown. Herein, we propose a non-canonical epithelial-specific role of LOX in the maintenance of epithelial homeostasis using 3D organoid and murine models. We performed quantitative reverse transcriptase PCR, Western blot, histologic analysis, and RNA sequencing on immortalized non-transformed human esophageal epithelial cells (EPC2-hTERT) with short-hairpin RNA (shRNA) targeting LOX mRNA in both monolayer and 3D organoid culture. A novel murine model with a tamoxifen-induced Lox knockout specific to the stratified epithelium (K5CreER; Loxfl/fl) was utilized to further define the role of epithelial LOX in vivo. We found that LOX knockdown decreased the proliferative capacity of the esophageal epithelial cells in monolayer culture, and dramatically reduced the organoid formation rate (OFR) in the shLOX organoids. LOX knockdown was associated with decreased expression of the differentiation markers filaggrin, loricrin, and involucrin, with RNA sequencing analysis revealing 1224 differentially expressed genes demonstrating downregulation of pathways involved in cell differentiation and epithelial development. Mice with Lox knockout in their stratified epithelium demonstrated increased basaloid content of their esophageal epithelium and decreased Ki-67 staining compared to the vehicle-treated mice, suggesting reduced differentiation and proliferation in the Lox-deficient epithelium in vivo. Our results demonstrate, both in vivo and in vitro, that LOX may regulate epithelial homeostasis in the esophagus through the modulation of epithelial proliferation and differentiation. Understanding the mechanisms of perturbation in epithelial proliferation and differentiation in an inflamed esophagus could lead to the development of novel treatments that could promote epithelial healing and restore homeostasis.

Roles of Lysyl oxidases (LOX(L)) in pathologic calcification

Calcification of tissues involves the formation and deposition of calcium-containing crystals in the extracellular matrix (ECM). While this process is normal in bones, it becomes pathological when it occurs in cardiovascular and musculoskeletal soft tissues. Pathological calcification (PC) triggers detrimental pathways such as inflammation and oxidative stress, contributing to tissue damage and dysregulated tissue biomechanics, ultimately leading to severe complications and even death. The underlying mechanisms of PC remain elusive. Emerging evidence suggests a significant role of lysyl oxidases (LOX(L)) in PC. LOX(L) are a group of five enzymes involved in collagen cross-linking and ECM maturation. Beyond their classical role in bone mineralization, recent investigations propose new non-classical roles for LOX(L) that could be relevant in PC. In this review, we analyzed and summarized the functions of LOX(L) in cardiovascular and musculoskeletal PC, highlighting their deleterious roles in most studies. To date, specific inhibitors targeting LOX(L) isoforms are under development. New therapeutic tools targeting LOX(L) are warranted in PC and must avoid adverse effects on physiological bone mineralization.

Cancer treatments as paradoxical catalysts of tumor awakening in the lung

Much of the fatality of tumors is linked to the growth of metastases, which can emerge months to years after apparently successful treatment of primary tumors. Metastases arise from disseminated tumor cells (DTCs), which disperse through the body in a dormant state to seed distant sites. While some DTCs lodge in pre-metastatic niches (PMNs) and rapidly develop into metastases, other DTCs settle in distinct microenvironments that maintain them in a dormant state. Subsequent awakening, induced by changes in the microenvironment of the DTC, causes outgrowth of metastases. Hence, there has been extensive investigation of the factors causing survival and subsequent awakening of DTCs, with the goal of disrupting these processes to decrease cancer lethality. We here provide a detailed overview of recent developments in understanding of the factors controlling dormancy and awakening in the lung, a common site of metastasis for many solid tumors. These factors include dynamic interactions between DTCs and diverse epithelial, mesenchymal, and immune cell populations resident in the lung. Paradoxically, among key triggers for metastatic outgrowth, lung tissue remodeling arising from damage induced by the treatment of primary tumors play a significant role. In addition, growing evidence emphasizes roles for inflammation and aging in opposing the factors that maintain dormancy. Finally, we discuss strategies being developed or employed to reduce the risk of metastatic recurrence.

Stiffness-Dependent Lysyl Oxidase Regulation through Hypoxia-Inducing Factor 1 Drives Extracellular Matrix Modifications in Psoriasis

Psoriasis is a common chronic inflammatory skin disease characterized by a thickened epidermis with elongated rete ridges and massive immune cell infiltration. It is currently unclear what impact mechanoregulatory aspects may have on disease progression. Using multiphoton second harmonic generation microscopy, we found that the extracellular matrix was profoundly reorganized within psoriatic dermis. Collagen fibers were highly aligned and assembled into thick, long collagen bundles, whereas the overall fiber density was reduced. This was particularly pronounced within dermal papillae extending into the epidermis. Furthermore, the extracellular matrix-modifying enzyme lysyl oxidase was highly upregulated in the dermis of patients with psoriasis. In vitro experiments identified a previously unreported link between hypoxia-inducing factor 1 stabilization and lysyl oxidase protein regulation in mechanosensitive skin fibroblasts. Lysyl oxidase secretion and activity directly correlated with substrate stiffness and were independent of hypoxia and IL-17. Finally, single-cell RNA-sequencing analysis identified skin fibroblasts expressing high amounts of lysyl oxidase and confirmed elevated hypoxia-inducing factor 1 expression in psoriasis. Our findings suggest a potential yet undescribed mechanical aspect of psoriasis. Deregulated mechanical forces hence may be involved in initiating or maintaining of a positive feedback loop in fibroblasts and contribute to tissue stiffening and diminished skin elasticity in psoriasis, potentially exacerbating disease pathogenesis.

A Comprehensive Review of Protein Biomarkers for Invasive Lung Cancer

Invasion and metastasis are important hallmarks of lung cancer, and affect patients' survival. Early diagnostics of metastatic potential are important for treatment management. Recent findings suggest that the transition to an invasive phenotype causes changes in the expression of 700-800 genes. In this context, the biomarkers restricted to the specific type of cancer, like lung cancer, are often overlooked. Some well-known protein biomarkers correlate with the progression of the disease and the immunogenicity of the tumor. Most of these biomarkers are not exclusive to lung cancer because of their significant role in tumorigenesis. The dysregulation of others does not necessarily indicate cell invasiveness, as they play an active role in cell division. Clinical studies of lung cancer use protein biomarkers to assess the invasiveness of cancer cells for therapeutic purposes. However, there is still a need to discover new biomarkers for lung cancer. In the future, minimally invasive techniques, such as blood or saliva analyses, may be sufficient for this purpose. Many researchers suggest unconventional biomarkers, like circulating nucleic acids, exosomal proteins, and autoantibodies. This review paper aims to discuss the advantages and limitations of protein biomarkers of invasiveness in lung cancer, to assess their prognostic value, and propose novel biomarker candidates.

Copper homeostasis dysregulation in respiratory diseases: a review of current knowledge

Cu is an essential micronutrient for various physiological processes in almost all human cell types. Given the critical role of Cu in a wide range of cellular processes, the local concentrations of Cu and the cellular distribution of Cu transporter proteins in the lung are essential for maintaining a steady-state internal environment. Dysfunctional Cu metabolism or regulatory pathways can lead to an imbalance in Cu homeostasis in the lungs, affecting both acute and chronic pathological processes. Recent studies have identified a new form of Cu-dependent cell death called cuproptosis, which has generated renewed interest in the role of Cu homeostasis in diseases. Cuproptosis differs from other known cell death pathways. This occurs through the direct binding of Cu ions to lipoylated components of the tricarboxylic acid cycle during mitochondrial respiration, leading to the aggregation of lipoylated proteins and the subsequent downregulation of Fe-S cluster proteins, which causes toxic stress to the proteins and ultimately leads to cell death. Here, we discuss the impact of dysregulated Cu homeostasis on the pathogenesis of various respiratory diseases, including asthma, chronic obstructive pulmonary disease, idiopathic interstitial fibrosis, and lung cancer. We also discuss the therapeutic potential of targeting Cu. This study highlights the intricate interplay between copper, cellular processes, and respiratory health. Copper, while essential, must be carefully regulated to maintain the delicate balance between necessity and toxicity in living organisms. This review highlights the need to further investigate the precise mechanisms of copper interactions with infections and immune inflammation in the context of respiratory diseases and explore the potential of therapeutic strategies for copper, cuproptosis, and other related effects.

The interplay of collagen, macrophages, and microcalcification in atherosclerotic plaque cap rupture mechanics

The rupture of an atherosclerotic plaque cap overlying a lipid pool and/or necrotic core can lead to thrombotic cardiovascular events. In essence, the rupture of the plaque cap is a mechanical event, which occurs when the local stress exceeds the local tissue strength. However, due to inter- and intra-cap heterogeneity, the resulting ultimate cap strength varies, causing proper assessment of the plaque at risk of rupture to be lacking. Important players involved in tissue strength include the load-bearing collagenous matrix, macrophages, as major promoters of extracellular matrix degradation, and microcalcifications, deposits that can exacerbate local stress, increasing tissue propensity for rupture. This review summarizes the role of these components individually in tissue mechanics, along with the interplay between them. We argue that to be able to improve risk assessment, a better understanding of the effect of these individual components, as well as their reciprocal relationships on cap mechanics, is required. Finally, we discuss potential future steps, including a holistic multidisciplinary approach, multifactorial 3D in vitro model systems, and advancements in imaging techniques. The obtained knowledge will ultimately serve as input to help diagnose, prevent, and treat atherosclerotic cap rupture.

Coordination between cytoskeletal organization, cell contraction and extracellular matrix development, is depended on LOX for aneurysm prevention

Distinct, seemingly independent, cellular pathways affecting intracellular machineries or extracellular matrix (ECM) deposition and organization, have been implicated in aneurysm formation. One of the key genes associated with the pathology in both humans and mice is Lysyl oxidase (LOX), a secreted ECM-modifying enzyme, highly expressed in medial vascular smooth muscle cells. To dissect the mechanisms leading to aneurysm development, we conditionally deleted Lox in smooth muscle cells. We find that cytoskeletal organization is lost following Lox deletion. Cell culture assays and in vivo analyses demonstrate a cell-autonomous role for LOX affecting myosin light chain phosphorylation and cytoskeletal assembly resulting in irregular smooth muscle contraction. These results not only highlight new intracellular roles for LOX, but notably they link between multiple processes leading to aneurysm formation suggesting LOX coordinates ECM development, cytoskeletal organization and cell contraction required for media development and function.

Neutrophil Activity and Extracellular Matrix Degradation: Drivers of Lung Tissue Destruction in Fatal COVID-19 Cases and Implications for Long COVID

Pulmonary fibrosis, severe alveolitis, and the inability to restore alveolar epithelial architecture are primary causes of respiratory failure in fatal COVID-19 cases. However, the factors contributing to abnormal fibrosis in critically ill COVID-19 patients remain unclear. This study analyzed the histopathology of lung specimens from eight COVID-19 and six non-COVID-19 postmortems. We assessed the distribution and changes in extracellular matrix (ECM) proteins, including elastin and collagen, in lung alveoli through morphometric analyses. Our findings reveal the significant degradation of elastin fibers along the thin alveolar walls of the lung parenchyma, a process that precedes the onset of interstitial collagen deposition and widespread intra-alveolar fibrosis. Lungs with collapsed alveoli and organized fibrotic regions showed extensive fragmentation of elastin fibers, accompanied by alveolar epithelial cell death. Immunoblotting of lung autopsy tissue extracts confirmed elastin degradation. Importantly, we found that the loss of elastin was strongly correlated with the induction of neutrophil elastase (NE), a potent protease that degrades ECM. This study affirms the critical role of neutrophils and neutrophil enzymes in the pathogenesis of COVID-19. Consistently, we observed increased staining for peptidyl arginine deiminase, a marker for neutrophil extracellular trap release, and myeloperoxidase, an enzyme-generating reactive oxygen radical, indicating active neutrophil involvement in lung pathology. These findings place neutrophils and elastin degradation at the center of impaired alveolar function and argue that elastolysis and alveolitis trigger abnormal ECM repair and fibrosis in fatal COVID-19 cases. Importantly, this study has implications for severe COVID-19 complications, including long COVID and other chronic inflammatory and fibrotic disorders.

Lysyl Oxidase Regulates Epithelial Differentiation and Barrier Integrity in Eosinophilic Esophagitis

BACKGROUND & AIMS

Epithelial disruption in eosinophilic esophagitis (EoE) encompasses both impaired differentiation and diminished barrier integrity. We have shown that lysyl oxidase (LOX), a collagen cross-linking enzyme, is up-regulated in the esophageal epithelium in EoE. However, the functional roles of LOX in the esophageal epithelium remains unknown.

METHODS

We investigated roles for LOX in the human esophageal epithelium using 3-dimensional organoid and air-liquid interface cultures stimulated with interleukin (IL)13 to recapitulate the EoE inflammatory milieu, followed by single-cell RNA sequencing, quantitative reverse-transcription polymerase chain reaction, Western blot, histology, and functional analyses of barrier integrity.

RESULTS

Single-cell RNA sequencing analysis on patient-derived organoids revealed that LOX was induced by IL13 in differentiated cells. LOX-overexpressing organoids showed suppressed basal and up-regulated differentiation markers. In addition, LOX overexpression enhanced junctional protein genes and transepithelial electrical resistance. LOX overexpression restored the impaired differentiation and barrier function, including in the setting of IL13 stimulation. Transcriptome analyses on LOX-overexpressing organoids identified an enriched bone morphogenetic protein (BMP) signaling pathway compared with wild-type organoids. In particular, LOX overexpression increased BMP2 and decreased the BMP antagonist follistatin. Finally, we found that BMP2 treatment restored the balance of basal and differentiated cells.

CONCLUSIONS

Our data support a model whereby LOX exhibits noncanonical roles as a signaling molecule important for epithelial homeostasis in the setting of inflammation via activation of the BMP pathway in the esophagus. The LOX/BMP axis may be integral in esophageal epithelial differentiation and a promising target for future therapies.

S100A4 Is a Key Facilitator of Thoracic Aortic Dissection

Background: Thoracic aortic dissection (TAD) is one of the cardiovascular diseases with high incidence and fatality rates. Vascular smooth muscle cells (VSMCs) play a vital role in TAD formation. Recent studies have shown that extracellular S100A4 may participate in VSMCs regulation. However, the mechanism(s) underlying this association remains elusive. Consequently, this study investigated the role of S100A4 in VSMCs regulation and TAD formation. Methods: Hub genes were screened based on the transcriptome data of aortic dissection in the Gene Expression Synthesis database. Three-week-old male S100A4 overexpression (AAV9- S100A4 OE) and S100A4 knockdown (AAV9- S100A4 KD) mice were exposed to β-aminopropionitrile monofumarate through drinking water for 28 days to create the murine TAD model. Results: S100A4 was observed to be the hub gene in aortic dissection. Furthermore, overexpression of S100A4 was exacerbated, whereas inhibition of S100A4 significantly improved TAD progression. In the TAD model, the S100A4 was observed to aggravate the phenotypic transition of VSMCs. Additionally, lysyl oxidase (LOX) was an important target of S100A4 in TAD. S100A4 interacted with LOX in VSMCs, reduced mature LOX (m-LOX), and decreased elastic fiber deposition, thereby disrupting extracellular matrix homeostasis and promoting TAD development. Elastic fiber deposition in human aortic tissues was negatively correlated with the expression of S100A4, which in turn, was negatively correlated with LOX. Conclusions: Our data showed that S100A4 modulates TADprogression, induces lysosomal degradation of m-LOX, and reduces the deposition of elastic fibers by interacting with LOX, thus contributing to the disruption of extracellular matrix homeostasis in TAD. These findings suggest that S100A4 may be a new target for the prevention and treatment of TAD.

Lysyl oxidase inhibits BMP9-induced osteoblastic differentiation through reducing Wnt/β-catenin via HIF-1a repression in 3T3-L1 cells

BACKGROUND

Bone morphogenetic protein 9 (BMP9) is a promising growth factor in bone tissue engineering, while the detailed molecular mechanism underlying BMP9-oriented osteogenesis remains unclear. In this study, we investigated the effect of lysyl oxidase (Lox) on the BMP9 osteogenic potential via in vivo and in vitro experiments, as well as the underlying mechanism.

METHODS

PCR assay, western blot analysis, histochemical staining, and immunofluorescence assay were used to quantify the osteogenic markers level, as well as the possible mechanism. The mouse ectopic osteogenesis assay was used to assess the impact of Lox on BMP9-induced bone formation.

RESULTS

Our findings suggested that Lox was obviously upregulated by BMP9 in 3T3-L1 cells. BMP9-induced Runx2, OPN, and mineralization were all enhanced by Lox inhibition or knockdown, while Lox overexpression reduced their expression. Additionally, the BMP9-induced adipogenic makers were repressed by Lox inhibition. Inhibition of Lox resulted in an increase in c-Myc mRNA and β-catenin protein levels. However, the increase in BMP9-induced osteoblastic biomarkers caused by Lox inhibition was obviously reduced when β-catenin knockdown. BMP9 upregulated HIF-1α expression, which was further enhanced by Lox inhibition or knockdown, but reversed by Lox overexpression. Lox knockdown or HIF-1α overexpression increased BMP9-induced bone formation, although the enhancement caused by Lox knockdown was largely diminished when HIF-1α was knocked down. Lox inhibition increased β-catenin levels and decreased SOST levels, which were almost reversed by HIF-1α knockdown.

CONCLUSION

Lox may reduce the BMP9 osteoblastic potential by inhibiting Wnt/β-catenin signaling via repressing the expression HIF-1α partially.

Functional Pdgfra fibroblast heterogeneity in normal and fibrotic mouse lung

Aberrant fibroblast function plays a key role in the pathogenesis of idiopathic pulmonary fibrosis, a devastating disease of unrelenting extracellular matrix deposition in response to lung injury. Platelet-derived growth factor α-positive (Pdgfra+) lipofibroblasts (LipoFBs) are essential for lung injury response and maintenance of a functional alveolar stem cell niche. Little is known about the effects of lung injury on LipoFB function. Here, we used single-cell RNA-Seq (scRNA-Seq) technology and PdgfraGFP lineage tracing to generate a transcriptomic profile of Pdgfra+ fibroblasts in normal and injured mouse lungs 14 days after bleomycin exposure, generating 11 unique transcriptomic clusters that segregated according to treatment. While normal and injured LipoFBs shared a common gene signature, injured LipoFBs acquired fibrogenic pathway activity with an attenuation of lipogenic pathways. In a 3D organoid model, injured Pdgfra+ fibroblast-supported organoids were morphologically distinct from those cultured with normal fibroblasts, and scRNA-Seq analysis suggested distinct transcriptomic changes in alveolar epithelia supported by injured Pdgfra+ fibroblasts. In summary, while LipoFBs in injured lung have not migrated from their niche and retain their lipogenic identity, they acquire a potentially reversible fibrogenic profile, which may alter the kinetics of epithelial regeneration and potentially contribute to dysregulated repair, leading to fibrosis.

Lysyl oxidase like-2 in fibrosis and cardiovascular disease

Fibrosis is an important and essential reparative response to injury that, if left uncontrolled, results in the excessive synthesis, deposition, remodeling, and stiffening of the extracellular matrix, which is deleterious to organ function. Thus, the sustained activation of enzymes that catalyze matrix remodeling and cross linking is a fundamental step in the pathology of fibrotic diseases. Recent studies have implicated the amine oxidase lysyl oxidase like-2 (LOXL2) in this process and established significantly elevated expression of LOXL2 as a key component of profibrotic conditions in several organ systems. Understanding the relationship between LOXL2 and fibrosis as well as the mechanisms behind these relationships can offer significant insights for developing novel therapies. Here, we summarize the key findings that demonstrate the link between LOXL2 and fibrosis and inflammation, examine current therapeutics targeting LOXL2 for the treatment of fibrosis, and discuss future directions for experiments and biomedical engineering.

Targeting lysyl-oxidase (LOX) may facilitate intramural periarterial drainage for the treatment of Alzheimer's disease

Alzheimer's disease is the commonest form of dementia. It is likely that a lack of clearance of amyloid beta (Aβ) results in its accumulation in the parenchyma as Aβ oligomers and insoluble plaques, and within the walls of blood vessels as cerebral amyloid angiopathy (CAA). The drainage of Aβ along the basement membranes of blood vessels as intramural periarterial drainage (IPAD), could be improved if the driving force behind IPAD could be augmented, therefore reducing Aβ accumulation. There are alterations in the composition of the vascular basement membrane in Alzheimer's disease. Lysyl oxidase (LOX) is an enzyme involved in the remodelling of the extracellular matrix and its expression and function is altered in various disease states. The expression of LOX is increased in Alzheimer's disease, but it is unclear whether this is a contributory factor in the impairment of IPAD in Alzheimer's disease. The pharmacological inhibition of LOX may be a strategy to improve IPAD and reduce the accumulation of Aβ in the parenchyma and within the walls of blood vessels.

LOXL4, but not LOXL2, is the critical determinant of pathological collagen cross-linking and fibrosis in the lung

Idiopathic pulmonary fibrosis is a progressive fibrotic disease characterized by excessive deposition of (myo)fibroblast produced collagen fibrils in alveolar areas of the lung. Lysyl oxidases (LOXs) have been proposed to be the central enzymes that catalyze the cross-linking of collagen fibers. Here, we report that, while its expression is increased in fibrotic lungs, genetic ablation of LOXL2 only leads to a modest reduction of pathological collagen cross-linking but not fibrosis in the lung. On the other hand, loss of another LOX family member, LOXL4, markedly disrupts pathological collagen cross-linking and fibrosis in the lung. Furthermore, knockout of both Loxl2 and Loxl4 does not offer any additive antifibrotic effects when compared to Loxl4 deletion only, as LOXL4 deficiency decreases the expression of other LOX family members including Loxl2. On the basis of these results, we propose that LOXL4 is the main LOX activity underlying pathological collagen cross-linking and lung fibrosis.

Matrilin-2 within a three-dimensional lysine-modified chitosan porous scaffold enhances Schwann cell migration and axonal outgrowth for peripheral nerve regeneration

Background: Matrilin-2 is a key extracellular matrix protein involved in peripheral nerve regeneration. We sought to develop a biomimetic scaffold to enhance peripheral nerve regeneration by incorporating matrilin-2 within a chitosan-derived porous scaffold. We hypothesized that the use of such a novel biomaterial delivers microenvironmental cues to facilitate Schwann cell (SC) migration and enhance axonal outgrowth during peripheral nerve regeneration. Materials and Methods: The effect of matrilin-2 on SC migration was evaluated with agarose drop migration assay on matrilin-2 coated dishes. SC adhesion was determined with SCs cultured atop tissue culture dishes coated with matrilin-2. Various formulations of chitosan vs matrilin-2 in scaffold constructs were examined with scanning electron microscopy. The effect of the matrilin-2/chitosan scaffold on SC migration in the collagen conduits was determined by capillary migration assays. Neuronal adhesion and axonal outgrowth were evaluated with three-dimensional (3D) organotypic assay of dorsal root ganglions (DRG). DRG axonal outgrowth within the scaffolds was determined by immunofluorescence staining of neurofilaments. Results: Matrilin-2 induced SC migration and enhanced its adhesion. A formulation of 2% chitosan with matrilin-2 demonstrated an optimal 3D porous architecture for SC interaction. Matrilin-2/chitosan scaffold enabled SCs to migrate against gravity within conduits. Chemical modification of chitosan with lysine (K-chitosan) further improved DRG adhesion and axonal outgrowth than the matrilin-2/chitosan scaffold without lysine modification. Conclusion: We developed a matrilin-2/K-chitosan scaffold to mimic extracellular matrix cues and provide a porous matrix to enhance peripheral nerve regeneration. Taking advantage of matrilin-2's capability to stimulate SC migration and adhesion, we formulated a porous matrilin-2/chitosan scaffold to support axongal outgrowth. Chemical modification of chitosan with lysine further improved matrilin-2 bioactivity in the 3D scaffold. The 3D porous matrilin-2/K-chitosan scaffolds have high potential for enhancing nerve repair by stimulating SC migration, neuronal adhesion, and axonal outgrowth.

Lysyl oxidase regulates epithelial differentiation and barrier integrity in eosinophilic esophagitis

Background & Aims

Epithelial disruption in eosinophilic esophagitis (EoE) encompasses both impaired differentiation and diminished barrier integrity. We have shown that lysyl oxidase (LOX), a collagen cross-linking enzyme, is upregulated in the esophageal epithelium in EoE. However, the functional roles of LOX in the esophageal epithelium remains unknown.

Methods

We investigated roles for LOX in the human esophageal epithelium using 3-dimensional organoid and air-liquid interface cultures stimulated with interleukin (IL)-13 to recapitulate the EoE inflammatory milieu, followed by single-cell RNA sequencing, quantitative reverse transcription-polymerase chain reaction, western blot, histology, and functional analyses of barrier integrity.

Results

Single-cell RNA sequencing analysis on patient-derived organoids revealed that LOX was induced by IL-13 in differentiated cells. LOX-overexpressing organoids demonstrated suppressed basal and upregulated differentiation markers. Additionally, LOX overexpression enhanced junctional protein genes and transepithelial electrical resistance. LOX overexpression restored the impaired differentiation and barrier function, including in the setting of IL-13 stimulation. Transcriptome analyses on LOX-overexpressing organoids identified enriched bone morphogenetic protein (BMP) signaling pathway compared to wild type organoids. Particularly, LOX overexpression increased BMP2 and decreased BMP antagonist follistatin. Finally, we found that BMP2 treatment restored the balance of basal and differentiated cells.

Conclusions

Our data support a model whereby LOX exhibits non-canonical roles as a signaling molecule important for epithelial homeostasis in the setting of inflammation via activation of BMP pathway in esophagus. The LOX/BMP axis may be integral in esophageal epithelial differentiation and a promising target for future therapies.

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

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

Structure-Reactivity-Property Relationships in Covalent Adaptable Networks

Polymer networks built out of dynamic covalent bonds offer the potential to translate the control and tunability of chemical reactions to macroscopic physical properties. Under conditions at which these reactions occur, the topology of covalent adaptable networks (CANs) can rearrange, meaning that they can flow, self-heal, be remolded, and respond to stimuli. Materials with these properties are necessary to fields ranging from sustainability to tissue engineering; thus the conditions and time scale of network rearrangement must be compatible with the intended use. The mechanical properties of CANs are based on the thermodynamics and kinetics of their constituent bonds. Therefore, strategies are needed that connect the molecular and macroscopic worlds. In this Perspective, we analyze structure-reactivity-property relationships for several classes of CANs, illustrating both general design principles and the predictive potential of linear free energy relationships (LFERs) applied to CANs. We discuss opportunities in the field to develop quantitative structure-reactivity-property relationships and open challenges.

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.

Semicarbazide-Sensitive Amine Oxidase (SSAO) and Lysyl Oxidase (LOX) Association in Rat Aortic Vascular Smooth Muscle Cells

Vascular smooth muscle cells (VSMCs) are the main stromal cells in the medial layer of the vascular wall. These cells produce the extracellular matrix (ECM) and are involved in many pathological changes in the vascular wall. Semicarbazide-sensitive amine oxidase (SSAO) and lysyl oxidase (LOX) are vascular enzymes associated with the development of atherosclerosis. In the vascular smooth muscle cells, increased SSAO activity elevates reactive oxygen species (ROS) and induces VSMCs death; increased LOX induces chemotaxis through hydrogen peroxide dependent mechanisms; and decreased LOX contributes to endothelial dysfunction. This study investigates the relationship between SSAO and LOX in VSMCs by studying their activity, protein, and mRNA levels during VSMCs passaging and after silencing the LOX gene, while using their respective substrates and inhibitors. At the basal level, LOX activity decreased with passage and its protein expression was maintained between passages. βAPN abolished LOX activity (** p < 0.01 for 8 vs. 3 and * p < 0.05 for 5 vs. 8) and had no effect on LOX protein and mRNA levels. MDL72527 reduced LOX activity at passage 3 and 5 (## p < 0.01) and had no effect on LOX protein, and mRNA expression. At the basal level, SSAO activity also decreased with passage, and its protein expression was maintained between passages. MDL72527 abolished SSAO activity (**** p < 0.0001 for 8 vs. 3 and * p < 0.05 for 5 vs. 8), VAP-1 expression at passage 5 (** p < 0.01) and 8 (**** p < 0.0001), and Aoc3 mRNA levels at passage 8 (* p < 0.05). βAPN inhibited SSAO activity (**** p < 0.0001 for 5 vs. 3 and 8 vs. 3 and * p < 0.05 for 5 vs. 8), VAP-1 expression at passage 3 (* p < 0.05), and Aoc3 mRNA levels at passage 3 (* p < 0.05). Knockdown of the LOX gene (**** p < 0.0001 for Si6 vs. Sictrl and *** p < 0.001 for Si8 vs. Sictrl) and LOX protein (** p < 0.01 for Si6 and Si8 vs. Sictrl) in VSMCs at passage 3 resulted in a reduction in Aoc3 mRNA (#### p < 0.0001 for Si6 vs. Sictrl and ### p < 0.001 for Si8 vs. Sictrl) and VAP-1 protein (# p < 0.05 for Si8 vs. Sictrl). These novel findings demonstrate a passage dependent decrease in LOX activity and increase in SSAO activity in rat aortic VSMCs and show an association between both enzymes in early passage rat aortic VSMCs, where LOX was identified as a regulator of SSAO activity, protein, and mRNA expression.

Lysyl Oxidases: Orchestrators of Cellular Behavior and ECM Remodeling and Homeostasis

Lysyl oxidases have long been considered key secreted extracellular matrix modifying enzymes. As such, their activity has been associated with the crosslinking of collagens and elastin, and as a result, they have been linked to multiple developmental and pathological processes. However, numerous lines of evidence also demonstrated that members of this enzyme family are localized and are active within the cytoplasm or cell nuclei, where they regulate and participate in distinct cellular events. In this review, we focus on a few of these events and highlight the intracellular role these enzymes play. Close examination of these events, suggest that the intracellular activities of lysyl oxidases is mostly observed in processes where concomitant changes in the extracellular matrix takes place. Here, we suggest that the LOX family members act in the relay between changes in the cells’ environment and the intracellular processes that promote them or that follow.

Single-cell transcriptomics reveals the regulative roles of cancer associated fibroblasts in tumor immune microenvironment of recurrent osteosarcoma

Rationale: Osteosarcoma (OS) is the most common primary bone tumor with a poor prognosis, but the detailed mechanism is still unclear. A comprehensive investigation of tumor microenvironment (TME) of OS might help find effective anti-tumor strategies. Single-cell transcriptomics is a powerful new tool to explore TME. Therefore, this study is designed to investigate the TME and gene expression pattern of primary and recurrent OS at the single-cell level.

Methods: The single-cell RNA sequencing and bioinformatic analysis were conducted to investigate the cellular constitution of primary, recurrent, and lung metastatic OS lesions according to the datasets of GSE152048 and GSE162454. TIMER database was used to investigate the role of LOX in the prognosis of sarcoma. The functions of related cells and markers were further confirmed by in vitro and in vivo experiments.

Results: Cancer associated fibroblasts (CAFs) were found with a higher infiltrating level in recurrent OS, and were enriched in the epithelial-mesenchymal transition (EMT) pathway. CAFs showed remarkably increased expression of LOX, which might lead to EMT and poor prognosis of OS. Mechanically, LOX regulated the function of CAFs and macrophage polarization to remodel the tumor immune microenvironment. Moreover, LOX inhibitor could inhibit migration and promote apoptosis of OS both in vitro and in vivo.

Conclusions: This study revealed the heterogeneity of recurrent OS and highlighted an innovative mechanism that CAFs regulate EMT of OS via LOX. Targeting LOX of CAFs showed promising efficacy in remodeling TME and treating recurrent OS.

The IRE1α-XBP1s Arm of the Unfolded Protein Response Activates N-Glycosylation to Remodel the Subepithelial Basement Membrane in Paramyxovirus Infection

Respiratory syncytial virus (RSV) causes severe lower respiratory tract infections (LRTI) associated with decreased pulmonary function, asthma, and allergy. Recently, we demonstrated that RSV induces the hexosamine biosynthetic pathway via the unfolded protein response (UPR), which is a pathway controlling protein glycosylation and secretion of the extracellular matrix (ECM). Because the presence of matrix metalloproteinases and matricellular growth factors (TGF) is associated with severe LRTI, we studied the effect of RSV on ECM remodeling and found that RSV enhances the deposition of fibronectin-rich ECM by small airway epithelial cells in a manner highly dependent on the inositol requiring kinase (IRE1α)–XBP1 arm of the UPR. To understand this effect comprehensively, we applied pharmacoproteomics to understand the effect of the UPR on N-glycosylation and ECM secretion in RSV infection. We observe that RSV induces N-glycosylation and the secretion of proteins related to ECM organization, secretion, or proteins integral to plasma membranes, such as integrins, laminins, collagens, and ECM-modifying enzymes, in an IRE1α–XBP1 dependent manner. Using a murine paramyxovirus model that activates the UPR in vivo, we validate the IRE1α–XBP1-dependent secretion of ECM to alveolar space. This study extends understanding of the IRE1α–XBP1 pathway in regulating N-glycosylation coupled to structural remodeling of the epithelial basement membrane in RSV infection.

Genetically Modified Mouse Models of Congenital Diaphragmatic Hernia: Opportunities and Limitations for Studying Altered Lung Development

Congenital diaphragmatic hernia (CDH) is a relatively common and life-threatening birth defect, characterized by an abnormal opening in the primordial diaphragm that interferes with normal lung development. As a result, CDH is accompanied by immature and hypoplastic lungs, being the leading cause of morbidity and mortality in patients with this condition. In recent decades, various animal models have contributed novel insights into the pathogenic mechanisms underlying CDH and associated pulmonary hypoplasia. In particular, the generation of genetically modified mouse models, which show both diaphragm and lung abnormalities, has resulted in the discovery of multiple genes and signaling pathways involved in the pathogenesis of CDH. This article aims to offer an up-to-date overview on CDH-implicated transcription factors, molecules regulating cell migration and signal transduction as well as components contributing to the formation of extracellular matrix, whilst also discussing the significance of these genetic models for studying altered lung development with regard to the human situation.

Regulators of collagen crosslinking in developing and adult tendons

Tendons are collagen-rich musculoskeletal tissues that possess the mechanical strength needed to transfer forces between muscles and bones. The mechanical development and function of tendons are impacted by collagen crosslinks. However, there is a limited understanding of how collagen crosslinking is regulated in tendon during development and aging. Therefore, the objective of the present review was to highlight potential regulators of enzymatic and non-enzymatic collagen crosslinking and how they impact tendon function. The main collagen crosslinking enzymes include lysyl oxidase (LOX) and the lysyl oxidase-like isoforms (LOXL), whereas non-enzymatic crosslinking is mainly mediated by the formation of advanced glycation end products (AGEs). Regulators of the LOX and LOXL enzymes may include mechanical stimuli, mechanotransducive cell signaling pathways, sex hormones, transforming growth factor (TGF)β family, hypoxia, and interactions with intracellular or extracellular proteins. AGE accumulation in tendon is due to diabetic conditions and aging, and can be mediated by diet and mechanical stimuli. The formation of these enzymatic and non-enzymatic collagen crosslinks plays a major role in tendon biomechanics and in the mechanisms of force transfer. A more complete understanding of how enzymatic and non-enzymatic collagen crosslinking is regulated in tendon will better inform tissue engineering and regenerative therapies aimed at restoring the mechanical function of damaged tendons.

Lysyl oxidase regulation and protein aldehydes in the injured newborn lung

During newborn lung injury, excessive activity of lysyl oxidases (LOXs) disrupts extracellular matrix (ECM) formation. Previous studies indicate that TGFβ activation in the O₂-injured mouse pup lung increases lysyl oxidase (LOX) expression. But how TGFβ regulates this, and whether the LOXs generate excess pulmonary aldehydes are unknown. First, we determined that O₂-mediated lung injury increases LOX protein expression in TGFβ-stimulated pup lung interstitial fibroblasts. This regulation appeared to be direct; this is because TGFβ treatment also increased LOX protein expression in isolated pup lung fibroblasts. Then using a fibroblast cell line, we determined that TGFβ stimulates LOX expression at a transcriptional level via Smad2/3-dependent signaling. LOX is translated as a pro-protein that requires secretion and extracellular cleavage before assuming amine oxidase activity and, in some cells, reuptake with nuclear localization. We found that pro-LOX is processed in the newborn mouse pup lung. Also, O₂-mediated injury was determined to increase pro-LOX secretion and nuclear LOX immunoreactivity particularly in areas populated with interstitial fibroblasts and exhibiting malformed ECM. Then, using molecular probes, we detected increased aldehyde levels in vivo in O₂-injured pup lungs, which mapped to areas of increased pro-LOX secretion in lung sections. Increased activity of LOXs plays a critical role in the aldehyde generation; an inhibitor of LOXs prevented the elevation of aldehydes in the O₂-injured pup lung. These results reveal new mechanisms of TGFβ and LOX in newborn lung disease and suggest that aldehyde-reactive probes might have utility in sensing the activation of LOXs in vivo during lung injury.

LOX upregulates FAK phosphorylation to promote metastasis in osteosarcoma

Osteosarcoma is a malignant bone tumor that commonly occurs in the pediatric population. Despite the use of chemotherapy and surgery, metastasis remains to be the leading cause of death in patients with osteosarcoma. We have previously reported that cytoplasmic mislocalization of p27 is associated with a poor outcome in osteosarcoma. In this study, we further show that lysyl oxidase (LOX) expression was associated with p27 mislocalization. LOX is an enigmatic molecule that acts as a tumor suppressor or a metastatic promoter; however, its role in osteosarcoma is still unclear. Hence, we performed both in vitro and in vivo analyses to dissect the role of LOX in osteosarcoma. The result of our survival analysis indicated that LOX expression significantly correlated with a poor outcome in osteosarcoma with or without controlling for the initial metastasis status (P < 0.05). Functionally, we found that higher LOX expression promoted osteosarcoma cell proliferation, migration, and invasiveness in vitro and produced a higher number of mice with pulmonary metastases in an orthotopic xenograft mouse model. Mechanistically, phospho-FAK was increased in osteosarcoma cells with high LOX expression. Our results further showed that FAK inhibition significantly reduced tumor cell proliferation and migration in vitro as well as LOX-mediated metastasis in mice. Together, our findings suggest that there is a novel link between p27 mislocalization and LOX expression. LOX plays a pivotal role in osteosarcoma metastasis by upregulating FAK phosphorylation. FAK inhibition may constitute a promising therapeutic strategy to reduce the development of metastasis in osteosarcoma with LOX overexpression.

Cadherin-11 promotes the mechanical strength of engineered elastic cartilage by enhancing extracellular matrix synthesis and microstructure

Limitations of current treatments for auricular cartilage defects have prompted the field of auricular cartilage tissue engineering. To date, inducing the formation of cartilaginous constructs with biochemical and biomechanical properties of native tissue is the final aim. Through hematoxylin-eosin and immunohistochemistry staining, Cadherin-11(CDH11) was confirmed highly expressed in the auricular cartilage tissue and chondrocytes. In vitro, by knockdown and overexpression of CDH11 in chondrocytes, CDH11 was demonstrated to promote the expression of collagen type II (COL2A), elastin (ELN), aggrecan (ACAN), and cartilage oligomeric matrix protein (COMP). In addition, the CDH11 overexpressed chondrocytes promoted neo-cartilage formation and its biomechanical property by increasing the key transcription factor of chondrogenesis SOX9 expression and cartilage extracellular matrix (ECM) production. The young's modulus and yield stress of the neo-cartilage in CDH11 overexpression group were about 1.7 times (p = 0.0152) and 2 times (p = 0.0428) higher than those in control group, respectively. Then, the immunohistochemistry staining, qRT-PCR and western blot examination results showed that the expression of COL2A and ELN were significantly increased. Notably, the electron microscopy results showed that the collagen and elastic fibers of the neo-cartilage in CDH11-OV group arranged in bunches and were more uniform and compact compared to the control group. Furthermore, CDH11 promoted elastic fiber assembly by increasing lysyl oxidase (LOX), fibrillin-1 (FBN1) expression. Taken together, our results demonstrated that CDH11 improves the mechanical strength of tissue-engineered elastic cartilage by promoting ECM synthesis and elastic fiber assembly.

Mineral Micronutrients in Asthma

Asthma represents one of the most common medical issues in the modern world. It is a chronic inflammatory disease characterized by persistent inflammation of the airways and disturbances in redox status, leading to hyperresponsiveness of bronchi and airway obstruction. Apart from classical risk factors such as air pollution, family history, allergies, or obesity, disturbances of the levels of micronutrients lead to impairments in the defense mechanisms of the affected organism against oxidative stress and proinflammatory stimuli. In the present review, the impact of micronutrients on the prevalence, severity, and possible risk factors of asthma is discussed. Although the influence of classical micronutrients such as selenium, copper, or zinc are well known, the effects of those such as iodine or manganese are only rarely mentioned. As a consequence, the aim of this paper is to demonstrate how disturbances in the levels of micronutrients and their supplementation might affect the course of asthma.

Dynamic and cell-specific transport networks for intracellular copper ions

Copper (Cu) homeostasis is essential for the development and function of many organisms. In humans, Cu misbalance causes serious pathologies and has been observed in a growing number of diseases. This Review focuses on mammalian Cu(I) transporters and highlights recent studies on regulation of intracellular Cu fluxes. Cu is used by essential metabolic enzymes for their activity. These enzymes are located in various intracellular compartments and outside cells. When cells differentiate, or their metabolic state is otherwise altered, the need for Cu in different cell compartments change, and Cu has to be redistributed to accommodate these changes. The Cu transporters SLC31A1 (CTR1), SLC31A2 (CTR2), ATP7A and ATP7B regulate Cu content in cellular compartments and maintain Cu homeostasis. Increasing numbers of regulatory proteins have been shown to contribute to multifaceted regulation of these Cu transporters. It is becoming abundantly clear that the Cu transport networks are dynamic and cell specific. The comparison of the Cu transport machinery in the liver and intestine illustrates the distinct composition and dissimilar regulatory response of their Cu transporters to changing Cu levels.

Developmental lineage of human pluripotent stem cell-derived cardiac fibroblasts affects their functional phenotype

Cardiac fibroblasts (CFBs) support heart function by secreting extracellular matrix (ECM) and paracrine factors, respond to stress associated with injury and disease, and therefore are an increasingly important therapeutic target. We describe how developmental lineage of human pluripotent stem cell-derived CFBs, epicardial (EpiC-FB), and second heart field (SHF-FB) impacts transcriptional and functional properties. Both EpiC-FBs and SHF-FBs exhibited CFB transcriptional programs and improved calcium handling in human pluripotent stem cell-derived cardiac tissues. We identified differences including in composition of ECM synthesized, secretion of growth and differentiation factors, and myofibroblast activation potential, with EpiC-FBs exhibiting higher stress-induced activation potential akin to myofibroblasts and SHF-FBs demonstrating higher calcification and mineralization potential. These phenotypic differences suggest that EpiC-FBs have utility in modeling fibrotic diseases while SHF-FBs are a promising source of cells for regenerative therapies. This work directly contrasts regional and developmental specificity of CFBs and informs CFB in vitro model selection.

Enzymatic cross-linking of collagens in organ fibrosis - resolution and assessment

Introduction: Enzymatic cross-linking of the collagens within the extracellular matrix (ECM) catalyzed by enzymes such as lysyl oxidase (LOX) and lysyl oxidase like-enzymes 1-4 (LOXL), transglutaminase 2 (TG2), and peroxidasin (PXDN) contribute to fibrosis progression through extensive collagen cross-linking. Studies in recent years have begun elucidating the important role of collagen cross-linking in perpetuating progression of organ fibrosis independently of inflammation through an increasingly stiff and noncompliant ECM. Therefore, collagen cross-linking and the cross-linking enzymes have become new targets in anti-fibrotic therapy as well as targets of novel biomarkers to properly assess resolution of the fibrotic ECM.Areas covered: The enzymatic actions of enzymes catalyzing collagen cross-linking and their relevance in organ fibrosis. Potential biomarkers specifically quantifying proteolytic fragments of collagen cross-linking is discussed based on Pubmed search done in November 2020 as well as the authors knowledge.Expert opinion: Current methods for the assessment of fibrosis involve the use of invasive and/or cumbersome and expensive methods such as tissue biopsies. Thus, an unmet need exists for the development and validation of minimally invasive biomarkers of proteolytic fragments of cross-linked collagens. These biomarkers may aid in the development and proper assessment of fibrosis resolution in coming years.

Lysyl oxidase interactions with transforming growth factor-β during angiogenesis are mediated by endothelin 1

Crosstalk between multiple components underlies the formation of mature vessels. Although the players involved in angiogenesis have been identified, mechanisms underlying the crosstalk between them are still unclear. Using the ex vivo aortic ring assay, we set out to dissect the interactions between two key angiogenic signaling pathways, vascular endothelial growth factor (VEGF) and transforming growth factor β (TGFβ), with members of the lysyl oxidase (LOX) family of matrix modifying enzymes. We find an interplay between VEGF, TGFβ, and the LOXs is essential for the formation of mature vascular smooth muscle cells (vSMC)-coated vessels. RNA sequencing analysis further identified an interaction with the endothelin-1 pathway. Our work implicates endothelin-1 downstream of TGFβ in vascular maturation and demonstrate the complexity of processes involved in generating vSMC-coated vessels.

Extracellular matrix-mediated remodeling and mechanotransduction in large vessels during development and disease

The vascular extracellular matrix (ECM) is synthesized and secreted during embryogenesis and facilitates the growth and remodeling of large vessels. Proper interactions between the ECM and vascular cells are pivotal for building the vasculature required for postnatal dynamic circulation. The ECM serves as a structural component by maintaining the integrity of the vessel wall while also regulating intercellular signaling, which involves cytokines and growth factors. The major ECM component in large vessels is elastic fibers, which include elastin and microfibrils. Elastin is predominantly synthesized by vascular smooth muscle cells (SMCs) and uses microfibrils as a scaffold to lay down and assemble cross-linked elastin. The absence of elastin causes developmental defects that result in the subendothelial proliferation of SMCs and inward remodeling of the vessel wall. Notably, elastic fiber formation is attenuated in the ductus arteriosus and umbilical arteries. These two vessels function during embryogenesis and close after birth via cellular proliferation, migration, and matrix accumulation. In dynamic postnatal mechano-environments, the elastic fibers in large vessels also serve an essential role in proper signal transduction as a component of elastin-contractile units. Disrupted mechanotransduction in SMCs leads to pathological conditions such as aortic aneurysms that exhibit outward remodeling. This review discusses the importance of the ECM-mainly the elastic fiber matrix-in large vessels during developmental remodeling and under pathological conditions. By dissecting the role of the ECM in large vessels, we aim to provide insights into the role of ECM-mediated signal transduction that can provide a basis for seeking new targets for intervention in vascular diseases.

Low-level red plus near infrared lights combination induces expressions of collagen and elastin in human skin in vitro

OBJECTIVE

Light therapy has attracted medical interests as a safe, alternative treatment for photo-ageing and photo-damaged skin. Recent research suggested the therapeutic activity of red and infrared (IR) lights may be effective at much lower energy levels than those used clinically. This study was to evaluate the efficacy of low-level red plus near IR light emitting diode (LED) combination on collagen and elastin and ATP production.

METHODS

Human dermal fibroblasts or skin tissues were irradiated daily by red (640 nm) plus near IR (830 nm) LED lights combination at 0.5 mW/cm² for 10 minutes (0.3 J/cm² ). qPCR, ELISAs or histology were used to determine the gene and protein expressions. Fluorescent measurement was used to assess crosslinks of collagen and elastic fibres. ATP production was evaluated by ATP assay.

RESULTS

Treatment of human fibroblast cell cultures with low-level red plus near IR lights combination was found to significantly increase LOXL1, ELN and COL1A1 and COL3A1 gene expressions as well as the synthesis of the procollagen type I and elastin proteins. Treating human skin explants with low-level red plus near IR lights combination similarly induced significant increases in the same gene expressions, type III collagen and elastic fibre formation and crosslinks. ATP production was increased in human dermal fibroblasts after red plus near IR lights combination treatment.

CONCLUSION

Low-level red plus near IR lights combination stimulated the production of collagen and elastin production associated with anti-ageing benefits. These findings suggest that low-level red plus near IR LED light combination may provide an effective treatment opportunity for people with photo-aged skin.

Severe congenital cutis laxa: Identification of novel homozygous LOX gene variants in two families

We report three babies from two families with a severe lethal form of congenital cutis laxa. All three had redundant and doughy-textured skin and two siblings from one family had facial dysmorphism. Echocardiograms showed thickened and poorly contractile hearts, arterial dilatation and tortuosity. Post-mortem examination in two of the babies further revealed widespread ectasia and tortuosity of medium and large sized arteries, myocardial hypertrophy, rib and skull fractures. The presence of fractures initially suggested a diagnosis of osteogenesis imperfecta. Under light microscopy bony matrices were abnormal and arterial wall architecture was grossly abnormal showing fragmented elastic fibres. Molecular analysis of known cutis laxa genes did not yield any pathogenic defects. Whole exome sequencing of DNA following informed consent identified two separate homozygous variants in the LOX (Lysyl Oxidase) gene. LOX belongs to the 5-lysyl oxidase gene family involved in initiation of cross-linking of elastin and collagen. A mouse model of a different variant in this gene recapitulates the phenotype seen in the three babies. Our findings suggest that the LOX gene is a novel cause of severe congenital cutis laxa with arterial tortuosity, bone fragility and respiratory failure.

Genetic Diversity and Signatures of Selection for Thermal Stress in Cattle and Other Two Bos Species Adapted to Divergent Climatic Conditions

Understanding the biological mechanisms of climatic adaptation is of paramount importance for the optimization of breeding programs and conservation of genetic resources. The aim of this study was to investigate genetic diversity and unravel genomic regions potentially under selection for heat and/or cold tolerance in thirty-two worldwide cattle breeds, with a focus on Chinese local cattle breeds adapted to divergent climatic conditions, Datong yak (Bos grunniens; YAK), and Bali (Bos javanicus) based on dense SNP data. In general, moderate genetic diversity levels were observed in most cattle populations. The proportion of polymorphic SNP ranged from 0.197 (YAK) to 0.992 (Mongolian cattle). Observed and expected heterozygosity ranged from 0.023 (YAK) to 0.366 (Sanhe cattle; SH), and from 0.021 (YAK) to 0.358 (SH), respectively. The overall average inbreeding (±SD) was: 0.118 ± 0.028, 0.228 ± 0.059, 0.194 ± 0.041, and 0.021 ± 0.004 based on the observed versus expected number of homozygous genotypes, excess of homozygosity, correlation between uniting gametes, and runs of homozygosity (ROH), respectively. Signatures of selection based on multiple scenarios and methods (F ST, HapFLK, and ROH) revealed important genomic regions and candidate genes. The candidate genes identified are related to various biological processes and pathways such as heat-shock proteins, oxygen transport, anatomical traits, mitochondrial DNA maintenance, metabolic activity, feed intake, carcass conformation, fertility, and reproduction. This highlights the large number of biological processes involved in thermal tolerance and thus, the polygenic nature of climatic resilience. A comprehensive description of genetic diversity measures in Chinese cattle and YAK was carried out and compared to 24 worldwide cattle breeds to avoid potential biases. Numerous genomic regions under positive selection were detected using three signature of selection methods and candidate genes potentially under positive selection were identified. Enriched function analyses pinpointed important biological pathways, molecular function and cellular components, which contribute to a better understanding of the biological mechanisms underlying thermal tolerance in cattle. Based on the large number of genomic regions identified, thermal tolerance has a complex polygenic inheritance nature, which was expected considering the various mechanisms involved in thermal stress response.

Pbx1, Meis1, and Runx1 Expression Is Decreased in the Diaphragmatic and Pulmonary Mesenchyme of Rats with Nitrofen-Induced Congenital Diaphragmatic Hernia

INTRODUCTION

 Congenital diaphragmatic hernia (CDH) and associated pulmonary hypoplasia (PH) are thought to originate from mesenchymal defects in pleuroperitoneal folds (PPFs) and primordial lungs. Pre-B-cell leukemia homeobox 1 (Pbx1), its binding partner myeloid ecotropic integration site 1 (Meis1), and runt-related transcription factor 1 (Runx1) are expressed in diaphragmatic and lung mesenchyme, functioning as transcription cofactors that modulate mesenchymal cell proliferation. Furthermore, Pbx1 ^-/- mice develop diaphragmatic defects and PH similar to human CDH. We hypothesized that diaphragmatic and pulmonary Pbx1, Meis1, and Runx1 expression is decreased in the nitrofen-induced CDH model.

MATERIALS AND METHODS

 Time-mated rats were exposed to nitrofen or vehicle on gestational day 9 (D9). Fetal diaphragms (n = 72) and lungs (n = 48) were microdissected on D13, D15, and D18, and were divided into control and nitrofen-exposed specimens. Diaphragmatic and pulmonary gene expression levels of Pbx1, Meis1, and Runx1 were analyzed by quantitative real-time polymerase chain reaction. Immunofluorescence-double-staining for Pbx1, Meis1, and Runx1 was combined with mesenchymal/myogenic markers Gata4 and myogenin to evaluate protein expression.

RESULTS

 Relative mRNA expression of Pbx1, Meis1, and Runx1 was significantly decreased in PPFs (D13), developing diaphragms/lungs (D15), and muscularized diaphragms/differentiated lungs (D18) of nitrofen-exposed fetuses compared with controls. Confocal-laser-scanning-microscopy revealed markedly diminished Pbx1, Meis1, and Runx1 immunofluorescence in diaphragmatic and pulmonary mesenchyme, associated with less proliferating mesenchymal cells in nitrofen-exposed fetuses on D13, D15, and D18 compared with controls.

CONCLUSION

 Decreased Pbx1, Meis1, and Runx1 expression during diaphragmatic development and lung branching morphogenesis may reduce mesenchymal cell proliferation, causing malformed PPFs and disrupted airway branching, thus leading to diaphragmatic defects and PH in the nitrofen-induced CDH model.

Inhibition of lysyl oxidase stimulates TGF-β signaling and metalloproteinases-2 and -9 expression and contributes to the disruption of ascending aorta in rats: protection by propylthiouracil

Mutations in lysyl oxidase (LOX) genes cause severe vascular anomalies in mice and humans. LOX activity can be irreversibly inhibited by the administration of β-aminoproprionitrile (BAPN). We investigated the mechanisms underlying the damage to the ascending thoracic aorta induced by LOX deficiency and evaluated whether 6-propylthiouracil (PTU) can afford protection in rats. BAPN administration caused disruption of the ascending aortic wall, increased the number of apoptotic cells, stimulated TGF-β signaling (increase of nuclear p-SMAD2 staining), and up-regulated the expression of metalloproteinases-2 and -9. In BAPN-treated animals, PTU reduced apoptosis, p-SMAD2 staining, MMP-2, and -9 expression, and markedly decreased the damage to the aortic wall. Our results suggest that, as in some heritable vascular diseases, enhanced TGF-β signaling and upregulation of MMP-2 and -9 can contribute to the pathogenesis of ascending aorta damage caused by LOX deficiency. We have also shown that PTU, a drug already in clinical use, protects against the effects of LOX inhibition. MMP-2 and -9 might be potential targets of new therapeutic strategies for the treatment of vascular diseases caused by LOX deficiency.

Inhibition of extracellular matrix integrity attenuates the early phase of aortic medial calcification in a rodent model

BACKGROUND AND AIMS

The mechanism of vascular calcification (VC) resembles that of bone metabolism, and a correlation has frequently been reported between calcification and vascular extracellular matrix (ECM) regulating its integrity; however, the detailed mechanisms remain unclear. In this study, we examined how the vascular ECM, especially collagen metabolism, is involved in the process of VC.

METHODS

VC was modeled using 5-week-old male Sprague-Dawley rats fed a diet containing warfarin and vitamin K1 (WVK). Additionally, β-aminopropionitrile (BAPN) was administered to inhibit lysyl oxidase (LOX), which is an enzyme that mediates collagen cross-linking. Harvested aortic samples were analyzed by staining with alizarin red (AR), immunohistochemistry (IHC), transmission electron microscopy (TEM), and ex vivo microcomputed tomography (μCT).

RESULTS

Rats fed WVK developed increasing numbers of aortic medial calcifications (AMCs) over time. TEM images indicated punctate calcification within collagen fibers in the early phase of AMC. AR staining of translucent samples revealed the distribution and severity of calcification, and these lesions were significantly decreased in the BAPN group. Three-dimensional reconstructed μCT images that allowed the quantification of calcified volumes revealed that BAPN significantly reduced the bulk of calcification. Moreover, IHC showed that both LOX and collagen I were present around the sites of AMC, and thus the IHC-positive area was reduced in the BAPN group compared to the WVK group.

CONCLUSIONS

The results indicated that inhibition of LOX by BAPN attenuated AMC, and that collagen metabolism plays a significant role in the early pathogenesis of VC.