Comparing the contractile properties of human fibroblasts in leg ulcers with normal fibroblasts.

OBJECTIVE: The tissue contraction phenomenon associated with wound healing is of prime importance for wound closure. Contractile properties of human fibroblasts from chronic venous leg ulcers were compared with those of normal fibroblasts using in vitro models. METHOD: Biopsies were taken from the uninvolved skin of the thigh, the epithelialised ulcer edge and the non-epithelialised ulcer centre in four patients (average age: 78 years). Fibroblasts were obtained by an explant technique and expanded in vitro in Dulbecco's Modified Eagle's Medium supplemented with 10% foetal calf serum and used for the assays at their fourth passage. Intracellular alpha-smooth muscle actin expression (alphaSM-actin) was studied by immunofluorescence labelling of cells cultured in monolayer. Contractile properties were evaluated using three-dimensional collagen lattices. RESULTS: Fibroblasts from the ulcer centre were the richest cells in actin filaments. Both populations of venous ulcer fibroblasts contracted more rapidly and to a greater extent than normal fibroblasts. The peak contractile forces developed by fibroblasts from the ulcer centre and the ulcer edge were 30% and 18% greater than normal fibroblasts respectively. CONCLUSION: Some functions of fibroblasts, in particular the generation of contractile forces and the formation of cytoplasmic actin filaments, seem not to be affected in chronic venous ulcers. DECLARATION OF INTEREST: This study was supported by the Fondation Coloplast pour la Qualite de la Vie of France.

Comparison of different wound dressings on cultured human fibroblasts and collagen lattices.

OBJECTIVE: We compared the effects on cultured human fibroblasts of a new non-adhesive wound dressing, Urgotul, with five other wound dressings. Urgotul is a hydrocolloid dressing; the comparator dressings included impregnated gauze and modern wound dressings. METHOD: Cultures in monolayer were used to study the morphology and growth of fibroblasts. The Bell model of cultured dermis equivalents was used to investigate myofibroblast differentiation. These cultures were labelled a-SM actin and F-actin. RESULTS: Two of the tested dressings induced cytotoxic effects. They were found to inhibit cell growth (greater than 60%) and to disturb cell shape and cytoskeletal differentiation. Urgotul and the remaining three dressings showed no effect on proliferation. However, some of them modified fibroblast morphology and affected F-actin distribution. CONCLUSION: Depending on their nature and components, wound dressings may respect or affect fibroblast behaviour in vitro (proliferation, morphology and a-SM actin and F-actin distribution). The significance of these in vitro observed findings require further investigations.

Autocrine regulation of cord blood-derived human mast cell activation by IL-10.

BACKGROUND: Ligation of the high-affinity receptor for IgE on human mast cells (MCs) induces the release of proinflammatory mediators, including vasoactive amines and cytokines (TNF-alpha, IL-5, and IL-8). Moreover, we have recently shown that IL-10 inhibits the release of proinflammatory mediators by activated MCs. OBJECTIVE: We investigated whether human cord blood-derived MCs (CBMCs) could produce IL-10 and whether this production could inhibit their activation in an autocrine fashion. METHODS: IL-10 synthesis by resting or activated human MCs derived from cord blood progenitors was investigated in cell supernatants or by using immunostaining and RT-PCR methods. In addition, the effect of IL-4 on such synthesis was also studied. Anti-IL-10-neutralizing antibodies were used to investigate the validity of the hypothesis of an autocrine regulation of MCs by IL-10. Finally, the presence of specific receptors for IL-10 was searched on human CBMCs by using flow cytometric analysis. RESULTS: Human CBMCs spontaneously synthesize and release IL-10, and this synthesis is increased after IgE/anti-IgE stimulation. In addition, the presence of IL-10 in resting or in activated MCs was proved by immunostaining. Interestingly, the release of IL-10 was also increased after incubation of the cells with IL-4. Besides, the use of neutralizing antibodies against IL-10 confirmed that IL-10 released inhibited MC activation in an autocrine fashion. Finally, the presence of specific receptors for this cytokine was observed on the membranes of our population of human CBMCs. CONCLUSION: Taken together, our data are in favor of an autocrine regulation pathway through synthesis and release of IL-10 by human MCs. Such an autoregulatory mechanism is, to our knowledge, the first described for these elements.