The stiffness-controlled release of interleukin-6 by cardiac fibroblasts is dependent on integrin α2β1

Modeling the Progression of Placental Transport from Early- to Late-Stage Pregnancy by Tuning Trophoblast Differentiation and Vascularization

The early-stage placental barrier is characterized by a lack of fetal circulation and by a thick trophoblastic barrier, whereas the later-stage placenta consists of vascularized chorionic villi encased in a thin, differentiated trophoblast layer, ideal for nutrient transport. In this work, predictive models of early- and late-stage placental transport are created using blastocyst-derived placental stem cells (PSCs) by modulating PSC differentiation and model vascularization. PSC differentiation results in a thinner, fused trophoblast layer, as well as an increase in human chorionic gonadotropin secretion, barrier permeability, and secretion of certain inflammatory cytokines, which are consistent with in vivo findings. Further, gene expression confirms this shift toward a differentiated trophoblast subtype. Vascularization results in a molecule type- and size-dependent change in dextran and insulin permeability. These results demonstrate that trophoblast differentiation and vascularization have critical effects on placental barrier permeability and that this model can be used as a predictive measure to assess fetal toxicity of xenobiotic substances at different stages of pregnancy.

Osteosarocma progression in biomimetic matrix with different stiffness: Insights from a three-dimensional printed gelatin methacrylamide hydrogel

Recent studies on osteosarcoma and matrix stiffness are still mostly performed in a 2D setting, which is distinct from in vivo conditions. Therefore, the results from the 2D models may not reflect the real effect of matrix stiffness on cell phenotype. Here, we employed a 3D bioprinted osteosarcoma model, to study the effect of matrix stiffness on osteosarcoma cells. Through density adjustment of GelMA, we constructed three osteosarcoma models with distinct matrix stiffnesses of 50, 80, and 130 kPa. In this study, we found that osteosarcoma cells proliferated faster, migrated more actively, had a more stretched morphology, and a lower drug sensitivity in a softer 3D matrix. When placed in a stiffer matrix, osteosarcoma cells secrete more MMP and VEGF, potentially to fight for survival and attract vascular invasion. Transcriptomic analysis showed that matrix stiffness could impact the signaling pathway of integrin α5-MAPK. The transplantation of 3D printed models in nude mice showed that cells encapsulated in the softer hydrogel were more likely to form subcutaneous tumors. These results suggest that matrix stiffness plays an important role in the development of osteosarcoma in a 3D environment and that inhibition of integrin α5 could block the signal transduction of matrix stiffness.

Melatonin increases collagen content accumulation and Fibroblast Growth Factor-2 secretion in cultured human cardiac fibroblasts

BACKGROUND

The extracellular matrix serves as a scaffold for cardiomyocytes, allowing them to work in accord. In rats, collagen metabolism within a myocardial infarction scar is regulated by melatonin. The present study determines whether melatonin influences matrix metabolism within human cardiac fibroblast cultures and examines the underlying mechanism.

METHODS

The experiments were performed on cultures of cardiac fibroblasts. The Woessner method, 1,9-dimethylmethylene blue assay, enzyme-linked immunosorbent assay and quantitative PCR were used in the study.

RESULTS

Melatonin treatment lowered the total cell count within the culture, elevated necrotic and apoptotic cell count as well as augmented cardiac fibroblast proliferation, and increased total, intracellular, and extracellular collagen within the fibroblast culture; it also elevated type III procollagen α1 chain expression, without increasing procollagen type I mRNA production. The pineal hormone did not influence matrix metalloproteinase-2 (MMP-2) release or glycosaminoglycan accumulation by cardiac fibroblasts. Melatonin increased the release of Fibroblast Growth Factor-2 (FGF-2) by human cardiac fibroblasts, but cardiotrophin release was not influenced.

CONCLUSION

Within human cardiac fibroblast culture, collagen metabolism is regulated by melatonin. The profibrotic effect of melatonin depends on the elevation of procollagen type III gene expression, and this could be modified by FGF-2. Two parallel processes, viz., cell elimination and proliferation, induced by melatonin, lead to excessive replacement of cardiac fibroblasts.

Integrins in cardiac fibrosis

Cells sense mechanical stress and changes in their matrix environment through the integrins, a family of heterodimeric surface receptors that bind to extracellular matrix ligands and trigger cytoskeletal remodeling, while transducing a wide range of intracellular signals. Integrins have been extensively implicated in regulation of inflammation, repair and fibrosis in many different tissues. This review manuscript discusses the role of integrin-mediated cascades in myocardial fibrosis. In vitro studies have demonstrated that β1 and αv integrins play an important role in fibrogenic conversion of cardiac fibroblast, acting through direct stimulation of FAK/Src cascades, or via accentuation of growth factor signaling. Fibrogenic actions of αv integrins may be mediated, at least in part, through pericellular activation of latent TGF-β stores. In vivo evidence supporting the role of integrin heterodimers in fibrotic cardiac remodeling is limited to associative evidence, and to experiments using pharmacologic inhibitors, or global loss-of-function approaches. Studies documenting in vivo actions of integrins on fibroblasts using cell-specific strategies are lacking. Integrin effects on leukocytes may also contribute to the pathogenesis of fibrotic myocardial responses by mediating recruitment and activation of fibrogenic macrophages. The profile and role of integrins in cardiac fibrosis may be dependent on the underlying pathologic condition. Considering their cell surface localization and the availability of small molecule inhibitors, integrins may be attractive therapeutic targets for patients with heart failure associated with prominent fibrotic remodeling.

Serum collected from rats with myocardial infarction increases extracellular matrix accumulation by myofibroblasts isolated from myocardial infarction scar

The effect on extracellular matrix content is believed to be an average of several serum derived compounds acting in opposition. The aim of the study is to determine whether whole serum of rats with myocardial infarction may modify the accumulation of extracellular matrix in cultures of myofibroblasts isolated from the myocardial infarction scar. A second aim is to determine whether the tested serum can also degranulate the mast cells. Serum was collected from rats with sham myocardial infarction, rats with myocardial infarction induced by coronary artery ligation and control animals. The experiments were carried out on myocardial infarction scar myofibroblasts or mast cells from the peritoneal cavity. The cultures were divided into three groups containing eight cultures each: one treated with serum from control rats, from animals after sham operation or from those after myocardial infarction. In all groups, the serum was used at concentrations of 10%, 20% or 30%. The total collagen content (Woesner method) glycosaminoglycan level (Farandale method), cell proliferation (BrdU), histamine secretion from mast cells (spectrofluorymetry), β1 integrin and α-smooth muscle actin expression (flow cytometry) were evaluated. Isolated cells were α-smooth muscle actin positive and identified as myofibroblasts. Serum derived from rats with myocardial infarction increased collagen and glycosaminoglycan content in the cultures and modified myofibroblast proliferation in a concentration-dependent manner. The serum also results in an imbalance between collagen and glycosaminoglycan levels. The content of β1 integrin was not influenced by myocardial infarction serum. The serum of rats with myocardial infarction is involved in regulation of collagen and glycosaminoglycan content in myofibroblast cultures, as well as the modification of their proliferation. These changes were not accompanied with integrin β1 density variations. The serum of the myocardial infarction rats did not influence the mast cell degranulation.

The Stiffness of Cardiac Fibroblast Substrates Exerts a Regulatory Influence on Collagen Metabolism via α2β1 Integrin, FAK and Src Kinases

Information about mechanical strain in the extracellular space is conducted along collagen fibers connected with integrins and then transmitted within cells. An aim of the study is to verify the hypothesis that the stiffness of cardiac human fibroblast substrates exerts a regulatory effect on collagen metabolism via integrin α2β1 and downstream signaling. The experiments were performed on human cardiac fibroblasts cultured on stiff or soft polyacrylamide gels. Extracellular and intracellular collagen content, metalloproteinase-1 (MMP-1), metalloproteinase-9 (MMP-9) and expression of the α1 chain of the procollagen type I gene (Col1A1) were elevated in cultures settled on soft substrate. The substrate stiffness did not modify tissue inhibitors of matrix metalloproteinase capacity (TIMPs 1–4). Integrin α2β1 inhibition (TC-I 15) or α2 subunit silencing resulted in augmentation of collagen content within the culture. Expression of Col1A1 and Col3A1 genes was increased in TC-I 15-treated fibroblasts. Total and phosphorylated levels of both FAK and Src kinases were elevated in fibroblasts cultured on stiff substrate. Inhibition of FAK (FAK kinase inhibitor 14) or Src kinase (AZM 47527) increased collagen content within the culture. The substrate stiffness exerted a regulatory influence on collagen metabolism via integrin α2β1 and its downstream signaling (FAK and Src kinases) in cardiac fibroblasts.

Key Roles of RGD-Recognizing Integrins During Cardiac Development, on Cardiac Cells, and After Myocardial Infarction

Cardiac cells interact with the extracellular matrix (ECM) proteins through integrin mechanoreceptors that control many cellular events such as cell survival, apoptosis, differentiation, migration, and proliferation. Integrins play a crucial role in cardiac development as well as in cardiac fibrosis and hypertrophy. Integrins recognize oligopeptides present on ECM proteins and are involved in three main types of interaction, namely with collagen, laminin, and the oligopeptide RGD (Arg-Gly-Asp) present on vitronectin and fibronectin proteins. To date, the specific role of integrins recognizing the RGD has not been addressed. In this review, we examine their role during cardiac development, their role on cardiac cells, and their upregulation during pathological processes such as heart fibrosis and hypertrophy. We also examine their role in regenerative and angiogenic processes after myocardial infarction (MI) in the peri-infarct area. Specific targeting of these integrins may be a way of controlling some of these pathological events and thereby improving medical outcomes.

Histamine is involved in the regulation of collagen content in cultured heart myofibroblasts via H2, H3 and H4 histamine receptors

Histamine is involved in the regulation of collagen metabolism during healing following a myocardial infarction; however, its effects on the intact heart tissue is unknown. The aim of the present study was to determine whether histamine may influence collagen content in cells isolated from intact heart, and to identify the histamine receptor involved in the regulation of collagen deposition. Cells were isolated from intact rat hearts and subjected to identification by flow cytometry. The effects of histamine and its receptor agonists and antagonists were investigated. The heart cells were found to be actin, desmin and vimentin positive. Histamine (used at a concentrations of 1x10-10-1x10-5 M) increased collagen content within the culture and increased the expression of α1 chain of the procollagen type III gene. The H2, H3 and H4 receptor inhibitors ranitidine, ciproxifan and JNJ 7777120 blocked the effect of histamine on collagen content. All tested histamine receptor agonists, viz. 2-pyridylethylamine dihydrochloride (H1 receptor agonist), amthamine dihydrobromide (H2 receptor agonist), imetit (H3 receptor agonist) and 4-methylhistamine hydrochloride (H4 receptor agonist), elevated collagen content within the heart myofibroblast cultures. The cells isolated from the intact heart were identified as myofibroblasts. Thus, the results of the present study showed that histamine augmented collagen content in the heart myofibroblast culture by activation of three histamine receptors (H2, H3 and H4). The effect of the amine was also dependent on the activation of collagen type III gene expression.

Piezo1 Channels Contribute to the Regulation of Human Atrial Fibroblast Mechanical Properties and Matrix Stiffness Sensing

The mechanical environment of cardiac cells changes continuously and undergoes major alterations during diseases. Most cardiac diseases, including atrial fibrillation, are accompanied by fibrosis which can impair both electrical and mechanical function of the heart. A key characteristic of fibrotic tissue is excessive accumulation of extracellular matrix, leading to increased tissue stiffness. Cells are known to respond to changes in their mechanical environment, but the molecular mechanisms underlying this ability are incompletely understood. We used cell culture systems and hydrogels with tunable stiffness, combined with advanced biophysical and imaging techniques, to elucidate the roles of the stretch-activated channel Piezo1 in human atrial fibroblast mechano-sensing. Changing the expression level of Piezo1 revealed that this mechano-sensor contributes to the organization of the cytoskeleton, affecting mechanical properties of human embryonic kidney cells and human atrial fibroblasts. Our results suggest that this response is independent of Piezo1-mediated ion conduction at the plasma membrane, and mediated in part by components of the integrin pathway. Further, we show that Piezo1 is instrumental for fibroblast adaptation to changes in matrix stiffness, and that Piezo1-induced cell stiffening is transmitted in a paracrine manner to other cells by a signaling mechanism requiring interleukin-6. Piezo1 may be a new candidate for targeted interference with cardiac fibroblast function.