[Development of non-cellular dermis: a step towards a total artificial skin]. / Mise au point d'un derme acellulaire: un pas vers la peau artificielle totale.

In large cutaneous defects due to severe burns, dermal mesenchyme healing has to be controlled in order to avoid granulation tissue that rapidly leads to important contractures and hypertrophic scars. We report a study about the use of an artificial dermis made of human collagen (I and III) and several glycosaminoglycans. This artificial dermis was grafted on Sprague-Dawley rats after a 9 cm2 skin excision on the back. An identical control area was made just under it, on the same animal. The animals were killed on day 2, 7, 14, 21, 30 and different parameters were studied: clinical study, bacteriological study, histopathological appearance, scanning and transmission electron microscopy, immunological study, physical parameters, UV absorption. Direct and indirect cytotoxicity tests, performed on cell cultures showed no change in the morphology and of the growth of the keratinocytes or of the fibroblasts. A biocompatibility study showed on the early days (day 2, 7, 14) that adherence of artificial dermis to the underlying tissue was good. There was virtually no bacterial colonization. Ultrastructural study showed an important cellular colonization, with an inflammatory appearance at the beginning. After a while, fibroblasts appeared, with synthesis of neocollagen fibers as early as the second week. Histological study showed neovessels in the artificial dermis. Later (day 21, 30) the inflammation was less severe and the amount of endogenous collagen increased.(ABSTRACT TRUNCATED AT 250 WORDS)

[Kinetics and physiopathology of immune depression following severe burns. Experimental study. Benefits of early excision. Role of prostaglandins]. / Cinétique et physiopathologie de la dépression immunitaire après brûlure grave. Etude expérimentale. Bénéfice de l'excision précoce. Rôle des prostaglandines.

The data obtained in a rat model supports the following conclusions. There is a period of normal immune responsiveness surrounding day 6, in spite of peaks of immunosuppression before and after that time. The spleen in burned animals is hypertrophic. This is due to its role as a filter (necrotic particles seen in macrophages) and as a "germ reservoir" (spleen culture studies). Impairment of immune function in spleen cells is important since, before day 6, there is an inhibition of antibody production with no alteration in lymphocyte transformation. After day 6, both functions are impaired. Most important to the clinical treatment of burns, all of these phenomena are diminished or abolished by early removal of the burned tissue. The profile of immune depression in burned rats therefore seems to show two stages: before and after day 6. During the first stage, stress and prostaglandins from burned skin are probably the cause of immune depression: during the second stage burn toxins and prostaglandins from the spleen cells are probably the cause.