Production of matrix metalloproteinase 2 in fibroblast reaction to mechanical stress in a collagen gel

Collagen matrix as a tool in studying fibroblastic cell behavior

Type I collagen is a fibrillar protein, a member of a large family of collagen proteins. It is present in most body tissues, usually in combination with other collagens and other components of extracellular matrix. Its synthesis is increased in various pathological situations, in healing wounds, in fibrotic tissues and in many tumors. After extraction from collagen-rich tissues it is widely used in studies of cell behavior, especially those of fibroblasts and myofibroblasts. Cells cultured in a classical way, on planar plastic dishes, lack the third dimension that is characteristic of body tissues. Collagen I forms gel at neutral pH and may become a basis of a 3D matrix that better mimics conditions in tissue than plastic dishes.

Mechanical compression upregulates MMP9 through SMAD3 but not SMAD2 modulation in hypertrophic scar fibroblasts

PURPOSE

Activation of transforming growth factor-β (TGF-β) signaling and matrix metalloproteinases are involved in hypertrophic scar (HS) formation. Compression therapy is known to be an effective approach for the treatment of hypertrophic scarring; however, the underlying molecular mechanisms remain poorly understood. We investigated the relationship between TGF-β signaling activation and matrix metalloproteinases in HS fibroblasts during mechanical compressive stress.

MATERIALS AND METHODS

Two groups of skin tissue from HS and the nearby normal tissue were obtained from surgical patients and analyzed. Primary fibroblasts from the HS tissue and normal fibroblasts were isolated. Pressure therapy was recapitulated in an in vitro three-dimensional culture model, using mechanical stress produced with the Flexcell FX-4000C Compression Plus System. Quantitative real-time PCR (qPCR) was used to analyze the gene expression profiles in skin tissue and cultured primary cells exposed to compressive stress. Knockdown of SMAD2 and SMAD3 was performed using their specific siRNA in HS and normal fibroblasts subjected to compressive stress, and gene expression was examined by qPCR and Western blot.

RESULTS

There was a significant upregulation of the mRNA expression of matrix metalloproteinase-2 (MMP2) and MMP9 in primary HS fibroblasts in response to mechanical stress. In contrast, the mRNA levels of collagen I and collagen III were downregulated in primary HS fibroblasts compared with those in the control cells. SiRNA-mediated knockdown of SMAD3 in the primary fibroblasts exposed to mechanical stress resulted in a decrease in the expression of MMP9 compared to control cells.

CONCLUSION

These results demonstrate that compressive stress upregulates MMP9 by SMAD3 but not by SMAD2.

Silica-collagen bionanocomposites as three-dimensional scaffolds for fibroblast immobilization

Silica-collagen bionanocomposite hydrogels were obtained by addition of silica nanoparticles to a protein suspension followed by neutralization. Electron microscopy studies indicated that larger silica nanoparticles (80 nm) do not interact strongly with collagen, whereas smaller ones (12 nm) form rosaries along the protein fibers. However, the composite network structurally evolved with time due to the contraction of the cells and the dissolution of the silica nanoparticles. When compared to classical collagen hydrogels, these bionanocomposite materials showed lower surface contraction in the short term (1 week) and higher viability of entrapped cells in the long term (3 weeks). A low level of gelatinase MMP2 enzyme expression was also found after this period. Several proteins involved in the catabolic and anabolic activity of the cells could also be observed by immunodetection techniques. All these data suggest that the bionanocomposite matrices constitute a suitable environment for fibroblast adhesion, proliferation and biological activity and therefore constitute an original three-dimensional environment for in vitro cell culture and in vivo applications, in particular as biological dressings.

Modulation of wound contracture alpha-smooth muscle actin and multispecific vitronectin receptor integrin alphavbeta3 in the rabbit's experimental model

The myofibroblast, a major component of granulation tissue, is a key cell during wound healing, tissue repair and connective tissue remodelling. Persistence of myofibroblasts within a fibrotic lesion leads to excessive scarring impairing function and aesthetics. Various wound-healing cytokines can be modulated by topical application of active agents to promote optimal wound healing and improve scar quality. Thus, the myofibroblast may represent an important target for wound-healing modulation to improve the evolution of conditions such as hypertrophic scars. The purpose of this work is to study the modulation of myofibroblasts and integrin alphavbeta3 in a full thickness wound performed on rabbits treated with different topical agents using: (1) saline, (2) Tegaderm occlusive dressing (3) silver sulfadiazine and (4) moist exposed burn ointment (MEBO). The reepithelialisation was 4 days faster in the MEBO group compared with the other therapies with less oedema formation, delayed contraction, less inflammatory cells and the lowest transepidermal water loss (TEWL) resulting in a soft scar. Although alpha-smooth muscle actin (alpha-SMA) was the highest around day 12 in the MEBO group, wound contraction and myofibroblast's activity were the least for the same period probably because of a downregulation of the integrin alphavbeta3. It seems that the effect of MEBO could be more pronounced on force transmission rather then on force generation. Greater insight into the pathology of scars may translate into non surgical treatments in the future and further work in myofibroblast biology will eventually result in efficient pharmacological tools, improving the evolution of healing and scar formation.

Decreased collagen production in chronologically aged skin: roles of age-dependent alteration in fibroblast function and defective mechanical stimulation

Reduced synthesis of collagen types I and III is characteristic of chronologically aged skin. The present report provides evidence that both cellular fibroblast aging and defective mechanical stimulation in the aged tissue contribute to reduced collagen synthesis. The reduction in collagen synthesis due to fibroblast aging was demonstrated by a lower in vitro production of type I procollagen by dermal fibroblasts isolated from skin of young (18 to 29 years) versus old (80+ years) individuals (82 +/- 16 versus 56 +/- 8 ng/ml; P < 0.05). A reduction in mechanical stimulation in chronologically aged skin was inferred from morphological, ultrastructural, and fluorescence microscopic studies. These studies, comparing dermal sections from young and old individuals, demonstrated a greater percentage of the cell surface attached to collagen fibers (78 +/- 6 versus 58 +/- 8%; P < 0.01) and more extensive cell spreading (1.0 +/- 0.3 vs. 0.5 +/- 0.3; P < 0.05) in young skin compared with old skin. These features are consistent with a lower level of mechanical stimulation on the cells in old versus young skin. Based on the findings presented here, we conclude that reduced collagen synthesis in chronologically aged skin reflects at least two different underlying mechanisms: cellular fibroblast aging and a lower level of mechanical stimulation.

Healing and Normal Fibroblasts Exhibit Differential Proliferation, Collagen Production, α-SMA Expression, and Contraction

This study determines the differences in proliferation, collagen production, alpha-smooth muscle actin (alpha-SMA) expression, and contraction between healing and normal fibroblasts. Transected and sham-operated rat medial collateral ligaments (MCL) were used to obtain healing and normal fibroblasts, respectively. It was found that healing fibroblasts in monolayer culture proliferated 1.4-fold faster at 48 h and had 1.7-fold greater protein expression of alpha-SMA than normal fibroblasts. In addition, it was noted that the proliferation of healing fibroblasts in collagen gels was not significantly different from that of normal fibroblasts at 24 h, but it was at 48 h. Furthermore, in collagen gels, healing fibroblasts produced more type I collagen than normal fibroblasts and generated 1.6- and 1.7-fold larger contractile forces at 15 and 20 h, respectively, than their normal counterparts. Taken together, the results of this study show that healing fibroblasts possess a differential proliferation, alpha-SMA protein expression, and contraction than normal fibroblasts.

Matrix metalloproteinases and their clinical applications in orthopaedics

Imbalance in the expression of matrix metalloproteinases and their inhibitors contribute considerably to abnormal connective tissue degradation prevalent in various orthopaedic joint diseases such as rheumatoid arthritis and osteoarthritis. Matrix metalloproteinase expression has been detected in ligament, tendon, and cartilage tissues in the joint. They are known to contribute to the development, remodeling, and maintenance of healthy tissue through their ability to cleave a wide range of extracellular matrix substrates. Their role has been extended to cell growth, migration, differentiation, and apoptosis. In orthopaedics, their clinical applications constantly are being explored. The multiple steps in matrix metalloproteinase regulation offer potential targets for inhibition, useful in drug therapy. The correlation between matrix metalloproteinases and progression in joint erosion presents potential prognostic and diagnostic tools in rheumatoid arthritis. Matrix metalloproteinases also can be incorporated into scaffold design to control the degradation rate of engineered tissue constructs. This current review aims to summarize and emphasize the importance of matrix metalloproteinases and their natural inhibitors in the maturation of musculoskeletal tissue through matrix remodeling and, therefore, in the generation of a new clinical potential in orthopaedics.

Reduced Fibroblast Interaction with Intact Collagen as a Mechanism for Depressed Collagen Synthesis in Photodamaged Skin

This report provides evidence from a number of different approaches (i.e., comparison of cell shape in 1-microm sections of photodamaged versus healthy skin at the light microscopic level; comparison of cell shape and apposition to collagen fibrils in ultrathin sections of the same tissues examined by transmission electron microscopy, and fluorescence staining for adhesion site protein expression and actin filament architecture in frozen tissue sections) that dermal cells in healthy skin are attached to collagen fibrils over a large part of the cell border, have a flattened/spread (two-dimensional) appearance and have abundant actin in their cytoplasm. In contrast, cells in photodamaged skin are often in contact with fragmented collagen or amorphous debris rather than intact collagen, have a collapsed/elongated shape, and have a lower amount of actin. Collagen synthesis is reduced in severely photodamaged skin relative to collagen synthesis in corresponding sun-protected skin (N Engl J Med 329:530, 1993). We hypothesize that fibroblasts in severely damaged skin have less interaction with intact collagen and as a result experience a reduction in mechanical tension. Decreased collagen synthesis is (presumed to be) the result.