Smad3-dependent CCN2 mediates fibronectin expression in human skin dermal fibroblasts

PAI-1 influences and curcumin destabilizes MMP-2, MMP-9 and basement membrane proteins during lung injury and fibrosis

One of the characteristic feature of idiopathic pulmonary fibrosis is an imbalanced fibrinolytic system. Plasminogen activator inhibitor-1 (PAI-1), an essential serine protease in the fibrinolytic system, has an anti-fibrotic tendency in some organs and a pro-fibrotic nature in others. Curcumin is reported to regulate the fibrinolytic system. In this study, we sought to determine how curcumin affected alterations in tissue remodelling mediated by PAI-1 in lung fibrosis. For in vitro studies, NIH3T3 fibroblasts were either exposed to TGF-β or overexpressed with PAI-1, and/or treated with curcumin. For in vivo studies, C57BL/6 mice were either instilled with bleomycin, overexpressed with PAI-1, and/or intervened with curcumin. Protein and gene expression studies were performed by western blotting and RT-PCR techniques, respectively. Curcumin intervention, in vitro and in vivo, could inhibit the the expression of collagen, fibronectin, MMP-2, and MMP-9, which was otherwise elevated by TGF-β or bleomycin. In conclusion, curcumin reduces pulmonary fibrosis by suppressing excessive basement membrane protein deposition and, likely, preventing the thickening of the alveolar septum.

CTGF Inhibits the Differentiation of Chicken Preadipocytes via the TGFβ/Smad3 Signaling Pathway or by Inducing the Expression of ACTG2

Chicken is the main source of protein for humans in most parts of the world. However, excessive fat deposition in chickens has become a serious problem. This adversely affects the growth of chickens and causes economic losses. Fat formation mainly occurs through preadipocyte differentiation, and excessive fat deposition results from the accumulation of preadipocytes after differentiation. Our previous studies have found that the connective tissue growth factor (CTGF) may be an important candidate gene for fat deposition. However, its function and mechanism in preadipocyte differentiation are still unclear. In this study, the RT-qPCR and Western blot results showed that the expression of CTGF mRNA and protein in the abdominal adipose of lean chickens was significantly higher than that of fat chickens. Therefore, we studied the function and mechanism of the CTGF in the differentiation of chicken preadipocytes. Functionally, the CTGF inhibited the differentiation of chicken preadipocytes. Mechanistically, the CTGF mediated the TGFβ1/Smad3 signaling pathway, thereby inhibiting the differentiation of chicken preadipocytes. In addition, we used the unique molecular identifier (UMI) RNA-Seq technology to detect genes that can be regulated by the CTGF in the whole genome. Through transcriptome data analysis, we selected actin gamma 2 (ACTG2) as a candidate gene. Regarding the function of the ACTG2 gene, we found that it inhibited the differentiation of chicken preadipocytes. Furthermore, we found that the CTGF can inhibit the differentiation of preadipocytes through the ACTG2 gene. In summary, this study found the CTGF as a new negative regulator of chicken preadipocyte differentiation. The results of this study help improve the understanding of the molecular genetic mechanism of chicken adipose tissue growth and development and also have reference significance for the study of human obesity.

Dual delivery gene-activated scaffold directs fibroblast activity and keratinocyte epithelization

Fibroblasts are the most abundant cell type in dermal skin and keratinocytes are the most abundant cell type in the epidermis; both play a crucial role in wound remodeling and maturation. We aim to assess the functionality of a novel dual gene activated scaffold (GAS) on human adult dermal fibroblasts (hDFs) and see how the secretome produced could affect human dermal microvascular endothelial cells (HDMVECs) and human epidermal keratinocyte (hEKs) growth and epithelization. Our GAS is a collagen chondroitin sulfate scaffold loaded with pro-angiogenic stromal derived factor (SDF-1α) and/or an anti-aging β-Klotho plasmids. hDFs were grown on GAS for two weeks and compared to gene-free scaffolds. GAS produced a significantly better healing outcome in the fibroblasts than in the gene-free scaffold group. Among the GAS groups, the dual GAS induced the most potent pro-regenerative maturation in fibroblasts with a downregulation in proliferation (twofold, p < 0.05), fibrotic remodeling regulators TGF-β1 (1.43-fold, p < 0.01) and CTGF (1.4-fold, p < 0.05), fibrotic cellular protein α-SMA (twofold, p < 0.05), and fibronectin matrix deposition (twofold, p < 0.05). The dual GAS secretome also showed enhancements of paracrine keratinocyte pro-epithelializing ability (1.3-fold, p < 0.05); basement membrane regeneration through laminin (6.4-fold, p < 0.005) and collagen IV (8.7-fold, p < 0.005) deposition. Our findings demonstrate enhanced responses in dual GAS containing hDFs by proangiogenic SDF-1α and β-Klotho anti-fibrotic rejuvenating activities. This was demonstrated by activating hDFs on dual GAS to become anti-fibrotic in nature while eliciting wound repair basement membrane proteins; enhancing a proangiogenic HDMVECs paracrine signaling and greater epithelisation of hEKs.

Increased Levels of BAMBI Inhibit Canonical TGF-β Signaling in Chronic Wound Tissues

Chronic wounds affect more than 2% of the population worldwide, with a significant burden on affected individuals, healthcare systems, and societies. A key regulator of the entire wound healing cascade is transforming growth factor beta (TGF-β), which regulates not only inflammation and extracellular matrix formation but also revascularization. This present work aimed at characterizing wound tissues obtained from acute and chronic wounds regarding angiogenesis, inflammation, as well as ECM formation and degradation, to identify common disturbances in the healing process. Serum and wound tissues from 38 patients (N = 20 acute and N = 18 chronic wounds) were analyzed. The patients' sera suggested a shift from VEGF/VEGFR to ANGPT/TIE2 signaling in the chronic wounds. However, this shift was not confirmed in the wound tissues. Instead, the chronic wound tissues showed increased levels of MMP9, a known activator of TGF-β. However, regulation of TGF-β target genes, such as CTGF, COL1A1, or IL-6, was absent in the chronic wounds. In wound tissues, all three TGF-β isoforms were expressed with increased levels of TGF-β1 and TGF-β3 and a reporter assay confirmed that the expressed TGF-β was activated. However, Western blots and immunostaining showed decreased canonical TGF-β signaling in the respective chronic wound tissues, suggesting the presence of a TGF-β inhibitor. As a potential regulatory mechanism, the TGF-β proteome profiler array suggested elevated levels of the TGF-β pseudo-receptor BAMBI. Also, tissue expression of BAMBI was significantly increased not only in chronic wounds (10.6-fold) but also in acute wounds that had become chronic (9.5-fold). In summary, our data indicate a possible regulatory role of BAMBI in the development of chronic wounds. The available few in vivo studies support our findings by postulating a therapeutic potential of BAMBI for controlling scar formation.

CCN1 is predominantly elevated in human skin dermis by solar-simulated ultraviolet irradiation and accumulated in dermal extracellular matrix

Skin primarily comprises a collagen-rich extracellular matrix (ECM) that provides structural and functional support to the skin. Aging causes progressive loss and fragmentation of dermal collagen fibrils, leading to thin and weakened skin (Dermal aging). We previously reported that CCN1 is elevated in naturally aged human skin, photoaged human skin, and acute UV-irradiated human skin dermal fibroblasts in vivo. Elevated CCN1 alters the expression of numerous secreted proteins that have deleterious effects on the dermal microenvironment, impairing the structural integrity and function of the skin. Here we show that CCN1 is predominantly elevated in the human skin dermis by UV irradiation and accumulated in the dermal extracellular matrix. Laser capture microdissection indicated that CCN1 is predominantly induced in the dermis, not in the epidermis, by acute UV irradiation in human skin in vivo. Interestingly, while UV-induced CCN1 in the dermal fibroblasts and in the medium is transient, secreted CCN1 accumulates in the ECM. We explored the functionality of the matrix-bound CCN1 by culturing dermal fibroblasts on an acellular matrix plate that was enriched with a high concentration of CCN1. We observed that matrix-bound CCN1 activates integrin outside-in signaling resulting in the activation of FAK and its downstream target paxillin and ERK, as well as elevated MMP-1 and inhibition of collagen, in human dermal fibroblasts. These data suggest that accumulation of CCN1 in the dermal ECM is expected to progressively promote the aging of the dermis and thereby negatively impact the function of the dermis.

Fibronectin in hyperglycaemia and its potential use in the treatment of diabetic foot ulcers: A review

Metabolism of fibronectin, the protein that plays a key role in the healing of wounds, is changed in the patients with diabetes mellitus. Fibronectin can interact with other proteins and proteoglycans and organise them to form the extracellular matrix, the basis of the granulation tissue in healing wounds. However, diabetic foot ulcers (DFUs) suffer from inadequate deposition of this protein. Degradation prevails over fibronectin synthesis in the proteolytic inflammatory environment in the ulcers. Because of the lack of fibronectin in the wound bed, the assembly of the extracellular matrix and the deposition of the granulation tissue cannot be started. A number of methods have been designed that prevents fibronectin degradation, replace lacking fibronectin or support its formation in non-healing wounds in animal models of diabetes. The aim of this article is to review the metabolism of fibronectin in DFUs and to emphasise that it would be useful to pay more attention to fibronectin matrix assembly in the ulcers when laboratory methods are translated to clinical practice.

Establishment of an In Vitro Scab Model for Investigating Different Phases of Wound Healing

Chronic wounds are a serious problem in clinical work and a heavy burden for individuals and society. In order to develop novel therapies, adequate model systems for the investigation of wound healing are required. Although in past years different in vitro and in vitro wound healing models have been established, a true human-like model does still not exist. Animal models are limited in their use due to species-specific differences in the skin, a lengthy manufacturing process, experimental costs, and ethical concerns. Both 2D and 3D in vitro models are usually comprised of only one or two skin cell types and fail to capture the reaction between blood cells and skin cells. Thus, our aim was to develop an in vitro scab model to investigate early reactions in the wound healing process. The here established scab model is comprised of HaCaT cells and freshly collected blood from healthy volunteers. The generated scabs were stably cultured for more than 2 weeks. TGF-β signaling is well known to regulate the early phases of wound healing. All three TGF-β isoforms and target genes involved in extracellular matrix composition and degradation were expressed in the in vitro scabs. To validate the in vitro scab model, the effects of either additional stimulation or the inhibition of the TGF-β signaling pathway were investigated. Exogenous application of TGF-β1 stimulated matrix remodeling, which loosened the structure of the in vitro scabs with time, also induced expression of the inhibitory Smad7. Inhibition of the endogenous TGF-β signaling, on the contrary, resulted in a rapid condensation and degranulation of the in vitro scabs. In summary, the here established in vitro scab model can be used to analyze the first phases of wound healing where blood and skin cells interact, as it is viable and responsive for more than 2 weeks.

3D cell culture using a clinostat reproduces microgravity-induced skin changes

Exposure to microgravity affects human physiology in various ways, and astronauts frequently report skin-related problems. Skin rash and irritation are frequent complaints during space missions, and skin thinning has also been reported after returning to Earth. However, spaceflight missions for studying the physiological changes in microgravity are impractical. Thus, we used a previously developed 3D clinostat to simulate a microgravity environment and investigate whether physiological changes of the skin can be reproduced in a 3D in vitro setting. Our results showed that under time-averaged simulated microgravity (taSMG), the thickness of the endothelial cell arrangement increased by up to 59.75%, indicating skin irritation due to vasodilation, and that the diameter of keratinocytes and fibroblast co-cultured spheroids decreased by 6.66%, representing skin thinning. The α1 chain of type I collagen was upregulated, while the connective tissue growth factor was downregulated under taSMG. Cytokeratin-10 expression was significantly increased in the taSMG environment. The clinostat-based 3D culture system can reproduce physiological changes in the skin similar to those under microgravity, providing insight for understanding the effects of microgravity on human health before space exploration.

Fibronectin in development and wound healing

Fibronectin structure and composition regulate contextual cell signaling. Recent advances have been made in understanding fibronectin and its role in tissue organization and repair. This review outlines fibronectin splice variants and their functions, evaluates potential therapeutic strategies targeting or utilizing fibronectin, and concludes by discussing potential future directions to modulate fibronectin function in development and wound healing.

WISP1 promotes bovine MDSC differentiation via recruitment of ANXA1 for the regulation of the TGF-β signalling pathway

Skeletal muscle is one of the most important tissues of the human body necessary for sporting activities. The differentiation of muscle-derived satellite cells (MDSCs) plays an important role in the development and regeneration of skeletal muscles. Similarly, the Wnt/β-catenin signalling pathway plays an important role in the process of muscle differentiation. Wnt1-inducible signalling pathway protein-1 (WISP1), a downstream protein of the Wnt/β-catenin signalling pathway and a member of the CCN family that also plays an important role in the differentiation process, and its expression increase during the differentiation of bovine MDSCs. However, its role in MDSC differentiation is poorly understood. Therefore, we investigated the mechanisms regulating this process via Western blot and immunofluorescence staining. Immunoprecipitation and mass spectrometry detected annexin A1 (ANXA1), a protein that interacts with WISP1. To determine whether WISP1 influences TGF-β signalling and differentiation independently of ANXA1, the latter was knocked down, while WISP1 was activated. WISP1 expression increased significantly during bovine MDSC differentiation. However, WISP1 did not affect the TGF-β signalling pathway protein marker when ANXA1 was inhibited. Taken together, WISP1 regulates the TGF-β signalling pathway through ANXA1 recruitment, thereby promoting bovine MDSC differentiation, suggesting the Wnt/β-catenin signalling pathway as another target to promote cell differentiation.

Cell-size-dependent upregulation of HGF expression in dermal fibroblasts: Impact on human skin connective tissue aging

BACKGROUND

Aged human skin is primarily attributable to loss of collagen, the main structural component of skin. Hepatocyte growth factor (HGF) acts as an anti-fibrotic factor by suppression of collagen production. It is not known whether HGF is involved in age-related collagen deficit in human skin.

OBJECTIVE

The objective of this study was to investigate the expression of HGF in human skin, and the underlying mechanisms of age-related elevation of HGF expression.

METHODS

The expression of HGF in young (25±5years, six subjects) and aged (75±6years, six subjects) human skin was determined by laser capture microdissection (LCM) coupled real-time PCR and immunohistology. The underlying mechanisms of age-related elevation of HGF were investigated by reducing dermal fibroblast size, which is a prominent feature of aged skin fibroblast in vivo.

RESULTS

HGF is predominantly expressed in human skin dermal fibroblasts, the major cells responsible for collagen production, and is significantly elevated in aged human skin in vivo. Mechanistically, reduced fibroblast size, which is a prominent feature of aged skin fibroblasts in vivo, is responsible for age-related elevation of HGF expression. Cell-size-dependent upregulation of HGF expression is driven by increased c-Jun and impaired TGF-β signaling. Restoration of fibroblast size normalizes increased c-Jun expression and impaired TGF-β signaling, and thus reversed the elevated HGF expression. Finally, we confirmed that application of retinoid (ROL), which has been shown to improve aged human skin, significantly reduced elevated HGF mRNA expression in aged human skin in vivo (78±4years, six subjects).

CONCLUSION

These data reveal a novel mechanism by which reduction of fibroblast size upregulates HGF expression, which in turn contributes to loss of collagen, a prominent feature of aged skin.

Correction: Smad3-dependent CCN2 mediates fibronectin expression in human skin dermal fibroblasts

[This corrects the article DOI: 10.1371/journal.pone.0173191.].