Biocompatibility of wound management products: the effect of various monosaccharides on L929 and 2002 fibroblast cells in culture

Probing the role of scaffold dimensionality and media composition on matrix production and phenotype of fibroblasts

Porous sponges, hydrogels, and micro/nanofibrous matrix are most commonly used three dimensional (3D) biomaterials in tissue engineering; however, reciprocal interaction between internal dimensionality of biomaterials and fibroblasts remains largely unexplored. Such studies would have potential to generate valuable insights about wound healing, tissue morphogenesis and homeostasis. To the best of our knowledge this is the first study to evaluate functionality of porous collagen matrix and collagen gels for in vitro culture of fibroblasts while investigating the role of culture media composition in modulating morphology, phenotype, extracellular matrix (ECM)-related gene expression and protein synthesis by fibroblasts. Encapsulation of fibroblasts in collagen gel was found to be more effective for ECM production compared to scaffold-based culture, as evidenced by enhanced collagen type I, elastin, lysyl oxidase, aggrecan gene expression. High glucose media induced spindle like morphology of typical in vivo fibroblasts and enhanced collagen production compared to other media. This variation in biosynthesis in different glucose concentrations was possibly due to endogenous activation of TGF-β or by an increase in ATP consuming anabolic pathways in high glucose concentration.

Effect of a hydrocolloid dressing on first intention healing surgical wounds in the dog: a pilot study

OBJECTIVES

To evaluate the efficacy of a hydrocolloid dressing for the treatment of surgical wounds in dogs.

METHODS

Six healthy young female dogs of medium size and different breed underwent ovariohysterectomy. Histological evaluation was performed on biopsies taken from the edges of the wounds at day 7. The dressing was applied on one half of the wound according to manufacturer's instructions; the second half served as control. Biopsy specimens were fixed in a 10% formalin buffered solution pH 7.4, paraffin embedded and stained with haematoxylin and eosin. For clinical assessment, the presence and quality of exudate, erythema of the surrounding area, swelling and correct apposition of the wound margins were evaluated.

RESULTS

The hydrocolloid dressing was easy to use. The clinical quality of the treated skin wounds was superior to the non-treated ones. Comparison of histological features between treated and untreated wounds showed a more regular organisation of the granulation tissue in the treated wounds, with fibroblasts being aligned parallel to the overlying epidermis. The number of inflammatory cells and the extension of granulation tissue were less prominent and less widespread in treated compared to untreated wounds.

CONCLUSION

The dressing performed very well in terms of adhesiveness and flexibility. It was useful in the management of surgical wounds to avoid contamination and ameliorate the epithelialisation rate and granulation tissue morphology of the surgical scar.

d-Glucosamine-based supramolecular hydrogels to improve wound healing

A simple supramolecular hydrogel based on D-glucosamine, a naturally occurring aminosaccharide, promises new biomaterials for applications such as wound healing.

Polyvalent dendrimer glucosamine conjugates prevent scar tissue formation

Dendrimers are hyperbranched macromolecules that can be chemically synthesized to have precise structural characteristics. We used anionic, polyamidoamine, generation 3.5 dendrimers to make novel water-soluble conjugates of D(+)-glucosamine and D(+)-glucosamine 6-sulfate with immuno-modulatory and antiangiogenic properties respectively. Dendrimer glucosamine inhibited Toll-like receptor 4-mediated lipopolysaccharide induced synthesis of pro-inflammatory chemokines (MIP-1 alpha, MIP-1 beta, IL-8) and cytokines (TNF-alpha, IL-1 beta, IL-6) from human dendritic cells and macrophages but allowed upregulation of the costimulatory molecules CD25, CD80, CD83 and CD86. Dendrimer glucosamine 6-sulfate blocked fibroblast growth factor-2 mediated endothelial cell proliferation and neoangiogenesis in human Matrigel and placental angiogenesis assays. When dendrimer glucosamine and dendrimer glucosamine 6-sulfate were used together in a validated and clinically relevant rabbit model of scar tissue formation after glaucoma filtration surgery, they increased the long-term success of the surgery from 30% to 80% (P = 0.029). We conclude that synthetically engineered macromolecules such as the dendrimers described here can be tailored to have defined immuno-modulatory and antiangiogenic properties, and they can be used synergistically to prevent scar tissue formation.

Biocompatibility of potential wound management products: fungal mycelia as a source of chitin/chitosan and their effect on the proliferation of human F1000 fibroblasts in culture

Aspergillus oryzae, Mucor mucedo, and Phycomyces blakesleeanus cultures were examined as sources of chitin/chitosan. The nitrogen content of the alkali-treated mycelia/sporangiophores of A. oryzae, M. mucedo, and P. blakesleeanus was 2.52, 3.61, and 6.27% w/w, which relates to an estimated chitin content of 37, 52, and 91%, respectively. The effect of these fungal materials on the rate of proliferation of human F1000 fibroblasts in culture was examined. At 0.01% w/v, all three materials exhibited significant (P < .05) proproliferant activity over a period of 13 days. However, at 0.05% w/v, P. blakesleeanus further enhanced cell proliferation, whereas A. oryzae and M. mucedo produced a significant (P < .05) antiproliferant effect. Higher concentrations of P. blakesleeanus (0.1 and 0.5%) caused marked inhibition of F1000 cell proliferation when measured on days 3 and 6. Only the proproliferant effect of these fungal materials appears to correlate to their chitin content. Furthermore, the cytomorphology of the fibroblasts indicated that P. blakesleeanus, and to a lesser extent M. mucedo, possessed cell attractant properties, again correlating with chitin content. If developed for use as wound management materials, the sporangiophores of P. blakesleeanus and the mycelium of M. mucedo could possibly promote the growth of fibroblasts and provide a matrix for their anchorage, thus contributing to the granulation phase of the healing cascade.

A study of hydrogen peroxide generation by, and antioxidant activity of, Granuflex (DuoDERM) Hydrocolloid Granules and some other hydrogel/hydrocolloid wound management materials

The effect of Granuflex Hydrocolloid Granules (0.01-0.50% w/v) on the rate of proliferation of murine (L929) fibroblasts was examined. The dose-response curve showed a significant (P < 0.02) pro-proliferant effect at 0.05%, and a significant (P < 0.02) antiproliferant effect at 0.50%, mirroring the dose-response curve produced by hydrogen peroxide in the concentration range 10(-9) - 10(-4) mol/l. The antiproliferant effect at 0.20% w/v was abolished by catalase, suggesting that the biological activity of Granuflex was mediated by the in situ generation of hydrogen peroxide. Formation of hydrogen peroxide by Granuflex was confirmed by performing the scopoletin-horseradish peroxidase assay in the presence and absence of catalase. The total concentration of hydrogen peroxide detected was about 8 x 10(-6) mol/l (using 0.5% w/v Granuflex) after 48 h at 37 degrees C. In contrast, when hydrogen peroxide itself was added to L929 cultures, a similar antiproliferant activity was observed at concentrations between 10(-4) and 10(-5) mol/l. These results suggested that Granuflex was undergoing autoxidation in the culture medium, and hence that it might possess antioxidant activity. In assays for antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH), Granuflex, and two other hydrocolloid dressings (Comfeel Powder and Bard Absorption Dressing) showed significant ability to reduce DPPH to DPPH2. These three dressings also displayed superoxide scavenging activity in a nitroblue tetrazolium reduction assay. We conclude that, in addition to providing a moist wound-healing environment, Granuflex and certain other hydrocolloids might contribute to the establishment and maintenance of the reducing environment necessary for energy production and hence cell division.(ABSTRACT TRUNCATED AT 250 WORDS)

Biocompatibility of wound management products: a study of the effects of various polysaccharides on murine L929 fibroblast proliferation and macrophage respiratory burst

An in-vitro screening method to examine the biocompatibility of materials used in wound management has been evaluated. This involved the use of a macrophage respiratory-burst assay and a fibroblast proliferation assay to represent respectively the inflammatory and the granulation phases in wound healing. Standard polysaccharides (calcium and sodium alginates, l-carrageenan, chitin, chitosan lactate, chondroitin sulphate and pectic acid) were used as test compounds. None of the polysaccharide samples caused a significant increase in L929 fibroblast cell numbers relative to control after 6 days incubation. The overall effect of exposure of the fibroblast cultures to the alginates, carrageenan and chondroitin sulphate was an extension of lag phase followed by an enhanced rate of cell proliferation in the logarithmic phase. Only calcium and sodium alginates and chondroitin sulphate enhanced the respiratory burst activity of murine macrophages; l-carrageenan and chitosan lactate were markedly inhibitory. The results suggest that a macrophage activity assay should be included as part of an in-vitro screening program to evaluate the biocompatibility of wound management materials and to detect intrinsic biological activity.

Toxicity of L-ascorbic acid to L929 fibroblast cultures: relevance to biocompatibility testing of materials for use in wound management

Fibroblast cultures are often used to evaluate materials intended for medical use, cytotoxicity being taken as an indicator of bioincompatibility. Such an approach has previously been taken with ascorbic acid in determining its value in wound healing. We have now reexamined the toxicity of L-ascorbic acid to L929 fibroblast cells in culture. Concentrations of ascorbic acid between 0.5 mM and 11 mM were tested. At concentrations above 2 mM, ascorbic acid was found to inhibit cell proliferation, with cell viability decreasing as the concentration was increased. This effect could be prevented by the addition of either superoxide dismutase or catalase to the culture medium. Assays of glutathione and glutathione disulfide were carried out on 8 day old cultures exposed for 24 h to the same concentrations of ascorbic acid. A dose-related depletion of glutathione occurred whilst glutathione disulfide levels remained essentially constant. Lactate dehydrogenase and glucose-6-phosphate dehydrogenase activities were induced by ascorbic acid at all concentrations tested but the ratio of NADP to NADPH nevertheless increased as the concentration of ascorbic acid increased. Finally, ATP in cells from 8-day-old cultures became depleted in the presence of ascorbic acid at concentrations in excess of about 5 mM when assayed after 24 h incubation. These biochemical changes and the concomitant cytostatic/cytotoxic effects may be ascribed to the reactive oxygen species produced by the autoxidation of ascorbic acid in the culture medium. Ascorbic acid breakdown products appeared not to be directly involved. In addition, our results suggested that superoxide acted cooperatively with hydroxyl to elicit these effects on the fibroblasts. It is evident from this study that the microenvironment surrounding fibroblasts in culture may differ fundamentally from that surrounding fibroblasts in a healing wound, making it impossible to extrapolate directly to an in vivo situation and hence to make any recommendations from these results concerning the use of ascorbic acid in wound healing.