Cultured vascular endothelial cells secrete a protein factor(s) that promotes the contraction of collagen lattices made with fibroblasts

Adenovirus vector-mediated transfer of the vascular endothelial growth factor cDNA to healing abdominal fascia enhances vascularity and bursting strength in mice with normal and impaired wound healing

BACKGROUND

We hypothesized that adenovirus-mediated transfer of the vascular endothelial growth factor (VEGF121) complementary DNA (cDNA) to murine laparotomy fascial wounds would enhance vascularity and bursting strength.

METHODS

Microfibrillar collagen sponges saturated with adenovirus (Ad) vectors encoding for the human VEGF121 cDNA (Ad(CU)VEGF121.1), a control marker gene (Ad beta gal, AdLuc) or no transgene (AdNull) were sutured to fascial edges during laparotomy closure in normal mice and mice treated with dexamethasone. Endpoints addressed included transgene expression in the fascia and surrounding tissue, the number of blood vessels in the healing wound determined using immunostaining, and wound bursting strength using a calibrated tensinometer.

RESULTS

Transgene expression was detected readily in the fascial edges, but only marginally detectable in neighboring tissues. In normal mice and mice treated with dexamethasone, no differences were observed at 7 days. Strikingly, however, 21 days after wound closure/therapy, significantly more blood vessels were present in the wounds that received the VEGF121 vector compared with controls (normal: AdNull: 4.2 +/- 1.8; Ad(CU)VEGF121.1: 11.2 +/- 1.2; P <.05; dexamethasone: AdNull: 1.4 +/- 0.8; Ad(CU)VEGF121.1: 5.4 +/- 1.2; P <.05), and bursting strength was significantly higher in VEGF121-treated wounds (normal: AdNull: 665 +/- 68 mN/mm; Ad(CU)VEGF121.1: 956 +/- 82 mN/mm; P <.0005; dexamethasone: AdNull: 234 +/- 111 mN/mm; Ad(CU)VEGF121.1: 592 +/- 121 mN/mm; P <.03).

CONCLUSIONS

Adenovirus-mediated gene transfer to healing fascial wounds is achieved readily using a microfibrillar collagen sponge, with transfer of the human VEGF121 cDNA significantly enhancing wound vascularity and bursting strength in normal mice, as well as in mice treated with dexamethasone.

An aqueous extract of the leaves of Chromolaena odorata (formerly Eupatorium odoratum) (Eupolin) inhibits hydrated collagen lattice contraction by normal human dermal fibroblasts

Chromolaena odorata (formerly Eupatorium odoratum) is used as a traditional medicine in Vietnam (Nghiem, 1992), where its Vietnamese common name is "co hoi." While it has been widely considered a weed by agriculturalists (Holm et al., 1991), the aqueous extract and the decoction from the leaves of this plant have been used throughout Vietnam for the treatment of soft tissue wounds, burn wounds, and skin infections. A number of clinical studies done by Vietnamese as well as foreign medical workers has demonstrated the efficacy of this extract on the wound-healing process. In this article, the effect of the Eupolin extract on hydrated collagen lattice contraction by human dermal fibroblasts, an in vitro model of wound contraction, is described. The significant inhibition of collagen gel contraction by Eupolin extract at 50 to 200 micrograms/ml is demonstrated in various concentrations of collagen. When the extract at 50 to 150 micrograms/ml was washed out of the lattices and replaced by fresh medium without Eupolin, the contraction of collagen by cells was resumed. The visualization of cells in the lattices by incubation in a tetrazolium salt for 2 h showed live cells at 50 to 150 micrograms/ml of extract. In contrast, all cells were killed in the higher extract doses of 300 or 400 micrograms/ml. These preliminary results showing the inhibitory effect of Eupolin extract on collagen contraction suggest that a clinical evaluation of its effect on wound contraction and scar quality should be made. This work illustrates that traditional remedies that are used by folk practitioners to improve healing can be examined in a scientific manner using in vitro wound-healing models. It could be that the synergistic properties of components of the natural extract contribute to the positive effects demonstrated on various wound-healing mechanisms.

Cyclic AMP-induced inhibition of collagen lattice contraction by fibroblasts may be attenuated by both cyclic AMP dependent and independent mechanisms

The contraction of collagen lattices made with foreskin fibroblasts in medium containing 1% fetal bovine serum was inhibited by intracellular cyclic AMP-raising drugs including cholera toxin (CT), forskolin, and dibutyryl-cAMP. The inhibition by CT was attenuated by insulin, acidic fibroblast growth factor (aFGF), and transforming growth factor-beta (TGF-beta). All three peptide factors have previously been reported to promote collagen lattice contraction by arterial smooth muscle cells and/or fibroblasts. Incubation of cells suspended in collagen gels with CT and forskolin resulted in a transient rise of the intracellular cyclic AMP levels, which peaked at 2 hr and 30 min, respectively, after drug exposure. Cholera toxin-induced intracellular cyclic AMP increase was attenuated by TGF-beta, but not by aFGF and insulin, when added simultaneously. Thus, TGF-beta may attenuate CT's inhibition on collagen lattice contraction by attenuating CT-induced intracellular cyclic AMP increase, whereas the attenuation by insulin and aFGF on the inhibition of lattice contraction may be mediated by a cyclic AMP-independent mechanism.

Human melanoma cell-derived factor(s) stimulate fibroblast glycosaminoglycan synthesis

Conditioned media from cultures of human metastatic Hs294T melanoma cells contain a factor/factors that promote(s) fibroblast-mediated contraction of collagen lattices, and stimulate(s) fibroblast glycosaminoglycan (GAG) synthesis. Complete medium from melanoma cell cultures stimulated fibroblast hyaluronate synthesis 9.3-fold, and sulphated GAG synthesis 2.6-fold, as measured by 3H-glucosamine incorporation. 35SO4 incorporation into sulphated GAGS was essentially unaltered, the net result being a decrease in the degree of sulphation. Fibroblasts synthesized hyaluronate with an increased molecular weight when grown in the presence of the melanoma-cell culture medium, while the molecular weights of heparan and chondroitin sulphates remained essentially unaltered. Our results indicate that the tumour-cell-derived factor(s) stimulate(s) changes in fibroblast glycosaminoglycan synthesis, and that these changes may facilitate tumour cell invasion in vivo.

Angiogenesis in wound healing

Angiogenesis is an essential component of wound healing. Vessel growth is controlled by the local actions of chemical mediators, the extracellular matrix, metabolic gradients, and physical forces. Manipulation of some of these factors can improve healing in experimental wounds. The clinical potential and specific application of 'angiomodulatory' strategies are discussed.