Crucial role of fibroblast integrins α2 and β1 in maintaining the structural and mechanical properties of the skin

Withania somnifera root extract inhibits MGO-induced skin fibroblast cells dysfunction via ECM-integrin interaction

ETHNOPHARMACOLOGICAL RELEVANCE

Withania somnifera (L.) Dunal, known as Ashwagandha, has long been used in traditional medicine in Ayurveda, India, a representative adaptogen. The main active constituents of W. somnifera are withanolides, and the root is often used as a medicine with a wide range of pharmacological activities, which can be used to treat insomnia, neurasthenia, diabetes mellitus and skin cancer.

AIM OF THE STUDY

Whole-component qualitative and quantitative analyses were performed on W. somnifera. We explored the ameliorative effect of the adaptogen representative plant W. somnifera on the senescence events of MGO-injured fibroblasts and its action mechanism and verified the hypotheses that WS can inhibit the accumulation of AGEs and regulate the dynamic balance among the components of the ECM by modulating the expression of integrin β1 receptor; as a result, WS maintains cellular behavioural and biological functions in a normal range and retards the aging of skin from the cellular level.

MATERIALS AND METHODS

In this study, the components of WS were first qualitatively and quantitatively analysed by HPLC fingerprinting and LC-MS detection. Second, a model of MGO-induced injury of CML-overexpressing fibroblasts was established. ELISA was used to detect CML expression and the synthesis of key extracellular matrix ECM protein components COL1, FN1, LM5 and TNC synthesis; CCK-8 was used to detect cell viability; EDU was used to detect cell proliferation capacity; fluorescence was used to detect cell adhesion capacity; and migration assay were used to detect cell migration capacity; qRT-PCR was used to detect the regulatory pathway TGF-β1 and MMP-2, MMP-9 in ECMs; immunofluorescence was used to detect the expression of ITGB1; and WB was used to detect the expression of COL1, FN1, LM5, Tnc, TGF-β1, MMP-2, MMP-9 and ITGB1.

RESULTS

In total, 27 active ingredients were analysed from WS, which mainly consisted of withanolide components, such as withaferin A and withanolide A. Based on the model of MGO-induced fibroblast senescence injury, WS significantly inhibited CML synthesis. By up-regulating the expression of integrin β1, it upregulated the expression of the TGF-β1 gene, which is closely related to the generation of ECMs, downregulated the expression of the MMP-2 and MMP-9 genes, which are closely related to the degradation of ECMs, maintained the dynamic balance of the four types of ECMs, and improved cell viability as well as proliferation, migration and adhesion abilities.

CONCLUSIONS

WS can prevent cellular behavioural dysfunction and delay skin ageing by reducing the accumulation of CML, upregulating the expression of the ITGB1 receptor, maintaining the normal function of ECM-integrin receptor interaction and preventing an imbalance between the production and degradation of protein components of ECMs. The findings reported in this study suggest that WS as a CML inhibitor can modulate ECM-integrin homeostasis and has great potential in the field of aging retardation.

Essential oils extracted from nine different plants exhibit differential effects on skin antioxidation and elasticity

Essential oils derived from plants are major ingredients in the medical and cosmetic industry. Here, we evaluated nine types of plant essential oils to identify potential candidates with antioxidant and elasticity-enhancing properties. Seven essential oils showed at least 10% radical scavenging activity at the highest concentration. Essential oils extracted from Aster glehnii, Cinnamomum cassia, Citrus unshiu, Juniperus chinensis L., and Juniperus chinensis var. sargentii significantly enhanced fibroblast viability, and oils from Cit. unshiu, J. chinensis L., and J. chinensis var. sargentii significantly increased cell proliferation and migration. Expression of extracellular matrix proteins, including collagen 1, collagen 3, and elastin, were upregulated by J. chinensis L. and J. chinensis var. sargentii oil, which also significantly enhanced the contractile activity of skin cells in a three-dimensional gel contraction assay. The results suggest that J. chinensis L. and J. chinensis var. sargentii essential oils may be potential anti-wrinkling and anti-oxidative agents for future consideration of use in the medical and cosmetic industry.

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.

The Soft- and Hard-Heartedness of Cardiac Fibroblasts: Mechanotransduction Signaling Pathways in Fibrosis of the Heart

Cardiac fibrosis, the excessive accumulation of extracellular matrix (ECM), remains an unresolved problem in most forms of heart disease. In order to be successful in preventing, attenuating or reversing cardiac fibrosis, it is essential to understand the processes leading to ECM production and accumulation. Cardiac fibroblasts are the main producers of cardiac ECM, and harbor great phenotypic plasticity. They are activated by the disease-associated changes in mechanical properties of the heart, including stretch and increased tissue stiffness. Despite much remaining unknown, an interesting body of evidence exists on how mechanical forces are translated into transcriptional responses important for determination of fibroblast phenotype and production of ECM constituents. Such mechanotransduction can occur at multiple cellular locations including the plasma membrane, cytoskeleton and nucleus. Moreover, the ECM functions as a reservoir of pro-fibrotic signaling molecules that can be released upon mechanical stress. We here review the current status of knowledge of mechanotransduction signaling pathways in cardiac fibroblasts that culminate in pro-fibrotic gene expression.

Mechanobiology of myofibroblast adhesion in fibrotic cardiac disease

Fibrotic cardiac disease, a leading cause of death worldwide, manifests as substantial loss of function following maladaptive tissue remodeling. Fibrosis can affect both the heart valves and the myocardium and is characterized by the activation of fibroblasts and accumulation of extracellular matrix. Valvular interstitial cells and cardiac fibroblasts, the cell types responsible for maintenance of cardiac extracellular matrix, are sensitive to changing mechanical environments, and their ability to sense and respond to mechanical forces determines both normal development and the progression of disease. Recent studies have uncovered specific adhesion proteins and mechano-sensitive signaling pathways that contribute to the progression of fibrosis. Integrins form adhesions with the extracellular matrix, and respond to changes in substrate stiffness and extracellular matrix composition. Cadherins mechanically link neighboring cells and are likely to contribute to fibrotic disease propagation. Finally, transition to the active myofibroblast phenotype leads to maladaptive tissue remodeling and enhanced mechanotransductive signaling, forming a positive feedback loop that contributes to heart failure. This Commentary summarizes recent findings on the role of mechanotransduction through integrins and cadherins to perpetuate mechanically induced differentiation and fibrosis in the context of cardiac disease.

Immunoexpression of α2-integrin and Hsp47 in hereditary gingival fibromatosis and gingival fibromatosis-associated dental abnormalities

Objective: The purpose of the present study was to investigate the expression of the α2-integrin subunit and heat shock protein 47 (Hsp47) in two families with isolated gingival fibromatosis (GF) form and one family with GF associated with dental abnormalities and normal gingiva (NG). Study Design: Immunohistochemistry was performed with antibodies against α2-integrin and Hsp47 in specimens from two unrelated families with hereditary gingival fibromatosis (Families 1 and 2) and from one family with a gingival fibromatosis-associated dental abnormality (Family 3); NG samples were used for comparison. The results were analysed statistically. Results: Immunoreactivity for α2-integrin and Hsp47 was observed in the nucleus of epithelial cells of both the basal and suprabasal layer and a more discreet signal was noted in connective tissue in all study samples. Hsp47 showed higher immunoreactivity in Family 2 compared with the other families (p≤0.05). Despite the markup α2-integrin was higher in Family 3 there was no statistically significant difference between the families studied (p≥0.05). Conclusions: Our results confirmed the heterogeneity of GF, such that similar patterns of expression of the condition may show differences in the expression of proteins such as Hsp47. Although no difference in α2-integrin expression was observed between GF and NG groups, future studies are necessary to determine the exact role of this protein in the various forms of GF and whether it contributes to GF pathogenesis.

Key words:Gingival fibromatosis, integrin alpha2, heat shock protein Hsp47.

Mechanosignaling pathways in cutaneous scarring

Mechanotransduction is the process by which physical forces are sensed and converted into biochemical signals that then result in cellular responses. The discovery and development of various molecular pathways involved in this process have revolutionized the fundamental and clinical understanding regarding the formation and progression of cutaneous scars. The aim of this review is to report the recent advances in scar mechanosignaling research. The mechanosignaling pathways that participate in the formation and growth of cutaneous scars can be divided into those whose role in mechanoresponsiveness has been proven (the TGF-β/Smad, integrin, and calcium ion pathways) and those who have a possible but as yet unproven role (such as MAPK and G protein, Wnt/β-catenin, TNF-α/NF-κB, and interleukins). During scar development, these cellular mechanosignaling pathways interact actively with the extracellular matrix. They also crosstalk extensively with the hypoxia, inflammation, and angiogenesis pathways. The elucidation of scar mechanosignaling pathways provides a new platform for understanding scar development. This better understanding will facilitate research into this promising field and may help to promote the development of pharmacological interventions that could ultimately prevent, reduce, or even reverse scar formation or progression.

Allosteric modulation of beta1 integrin function induces lung tissue repair

The cellular cytoskeleton, adhesion receptors, extracellular matrix composition, and their spatial distribution are together fundamental in a cell's balanced mechanical sensing of its environment. We show that, in lung injury, extracellular matrix-integrin interactions are altered and this leads to signalling alteration and mechanical missensing. The missensing, secondary to matrix alteration and cell surface receptor alterations, leads to increased cellular stiffness, injury, and death. We have identified a monoclonal antibody against β1 integrin which caused matrix remodelling and enhancement of cell survival. The antibody acts as an allosteric dual agonist/antagonist modulator of β1 integrin. Intriguingly, this antibody reversed both functional and structural tissue injury in an animal model of degenerative disease in lung.

Comprehension of terminal differentiation and dedifferentiation of chondrocytes during passage cultures

A high density collagen type I coated substrate (CL substrate) was used to evaluate the chondrocyte phenotypes in passaged cultures. With increasing age of cell population (population doubling (PD)=0-14.5), the frequency of non-dividing spindle shaped cells without ALP activity increased, accompanied with an increase in gene expression of collagen type I, meaning the senescence of dedifferentiated cells. At the middle age of cell population (PD=5.1 and 6.6), the high frequency of polygonal shaped cells with ALP activity existed on the CL substrate together with up-regulated expressions of collagen types II and X, indicating the terminal differentiation of chondrocytes. When the chondrocytes passaged up to the middle age were embedded in collagen gel, the high frequency of single hypertrophic cells with collagen type II formation was recognized, which supports the thought that the high gene expression of collagen type II was attributed to terminal differentiation rather than redifferentiation. These results show that the CL substrate can draw out the potential of terminal differentiation in chondrocytes, which is unattainable by a polystyrene surface, and that the CL substrate can be a tool to evaluate cell quality in three-dimensional culture with the collagen gel.

Lowered albumin extravasation rate in heart but not in other organs in beta3-integrin-deficient mice

AIM

The vascular protein permeability is dependent on the integrity of the vascular wall. The heart capillaries in male mice lacking beta3 integrins have an immature phenotype. Previously, we have demonstrated a role for alphavbeta3 integrins in control of interstitial fluid pressure (Pif) and thereby in the fluid flux during inflammation. We wanted to explore a possible role for alphavbeta3 integrins in controlling capillary protein permeability during control situation and inflammation.

METHODS

We performed double-tracer and microdialysis experiments on beta3-integrin-deficient mice and wild type control mice. We also measured blood pressure and heart rate in the two mice strains.

RESULTS

We found reduced albumin extravasation (during 25 min) in the heart capillaries (0.053 +/- 0.003 vs. 0.087 +/- 0.009 mL g(-1) dw, P < 0.05), and an increased cardiac mass/body weight (5.3 x 10(-3) +/- 0.3 x 10(-3) vs. 3.8 x 10(-3) +/- 0.1 x 10(-3), P < 0.01) in the beta3-integrin-deficient mice (n = 6) compared with the controls (n = 6). Heart rate and blood pressure were the same in mice with and without beta3-integrins. No difference in permeability was found in other tissues studied, or under local inflammation.

CONCLUSION

These results show a function for the alphavbeta3 integrin in the regulation of protein permeability, selective for the heart capillaries.

Morphological evaluation of chondrogenic potency in passaged cell populations

The present study describes the morphological assessment of chondrogenic potency during a cell expanding process through serial subculturing of rabbit chondrocytes at different levels of population doublings (PD) in a T-flask with a conventional polystyrene surface. The passaged populations were seeded on a high-density collagen surface (CL surface) and in a collagen gel (CL gel) scaffold to evaluate the planar and spatial morphologies of the chondrocytes, respectively, as well as the gene expressions of mRNA for collagen types I and II. The planar morphological estimation was based on roundness (R(c)) of chondrocyte cells at different PD values after 1 day incubation on the CL surface. The frequency of round-shaped cells with R(c)>0.9 (f(R)) decreased with increasing PD values, accompanied by an increase in collagen type I mRNA level. At PD=17.8, the frequency reached f(R)=0.12, which was less than one-sixth of that at PD=0. A similar trend was found with respect to the passaged chondrocytes embedded in the CL gels by estimating the spatial morphology in terms of sphericity (S(c)) determined 4 days after seeding. With an increase in PD value, the frequency in spherical-shaped cells with S(c)>0.9 (f(S)) decreased and the mRNA expression of collagen type I increased, giving f(S)=0.28 at PD=17.8 which was less than a quarter of that at PD=0. From these results, the cell morphologies on the CL surface and in the CL gel were proposed as indicators for understanding chondrogenic potentials concerning the phenotypes and differentiated states in the population during cell expansion, ultimately leading to quality control of tissue-engineered cartilage.

Effect of therapeutic pulsed ultrasound on lipoperoxidation and fibrogenesis in an animal model of wound healing

Evidence from the literature has shown that the wound healing process is enhanced by ultrasound therapy. In the present study, we measured thiobarbituric acid-reactive substances (TBARS; index of lipoperoxidation) and hydroxyproline (index of collagen synthesis) levels in wounds after therapeutic pulsed ultrasound (TPU) treatment. Male Wistar rats were submitted to skin ulceration, and three doses of TPU (0.4, 0.6, and 0.8W/cm(2)) were used. A circular area of skin was removed with a punch biopsy from the medial dorsal region. After TPU for 10 days, TBARS (Draper and Hadley [21]) and hydroxyproline (Woessner [22]) levels were measured in the tissue around the wound. Results showed that TPU improved wound healing, since the wound size was significantly smaller 5 and 10 days after ulceration in groups submitted to this treatment. Moreover, TBARS levels were decreased in the 0.4, 0.6, and 0.8W/cm(2) TPU groups, and hydroxyproline levels were increased in the 0.6 and 0.8W/cm(2) TPU groups. These findings indicate that TPU presents beneficial effects on the wound healing process, probably by speeding up the inflammatory phase and inducing collagen synthesis.

Positively and negatively modulating cell adhesion to type I collagen via peptide grafting

The biophysical interactions between cells and type I collagen are controlled by the level of cell adhesion, which is dictated primarily by the density of ligands on collagen and the density of integrin receptors on cells. The native adhesivity of collagen was modulated by covalently grafting glycine-arginine-glycine-aspartic acid-serine (GRGDS), which includes the bioactive RGD sequence, or glycine-arginine-aspartic acid-glycine-serine (GRDGS), which includes the scrambled RDG sequence, to collagen with the hetero-bifunctional coupling agent 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. The peptide-grafted collagen self-assembled into a fibrillar gel with negligible changes in gel structure and rheology. Rat dermal fibroblasts (RDFs) and human smooth muscle cells demonstrated increased levels of adhesion on gels prepared from RGD-grafted collagen, and decreased levels of adhesion on RDG-grafted collagen. Both cell types demonstrated an increased ability to compact free-floating RGD-grafted collagen gels, and an impaired ability to compact RDG-grafted gels. RDF migration on and within collagen was increased with RDG-grafted collagen and decreased with RGD-grafted collagen, and dose-response experiments indicated a biphasic response of RDF migration to adhesion. Smooth muscle cells demonstrated similar, though not statistically significant, trends. The ability to both positively and negatively modulate cell adhesion to collagen increases the versatility of this natural biomaterial for regenerative therapies.