Factor XIII of Blood Coagulation Modulates Collagen Biosynthesis by Fibroblasts in vitro

The effect of activated factor XIII (FXIIIa), the transglutaminase of blood coagulation, on some cellular functions was studied in skin and lung fibroblasts in vitro. FXIIIa repressed the overall protein synthesis and mainly collagen synthesis in a concentration-dependent manner and induced modifications in the proportion of the different types of newly synthesized collagen. The repression of collagen synthesis occurred in cells cultured on plastic (-40%), on coated fibronectin (-53%), on coated collagens (-38%) and within a collagen lattice (-16%). Preincubation of the cells with FXIIIa and labelling in its absence also resulted in such an inhibition. However, when embedded into a fibrin lattice cross-linked by FXIIIa, fibroblasts displayed a higher biosynthetic activity than in untreated fibrin gel. These results suggest that FXIIIa acts through a modulation of the cell-matrix interactions.</jats:p

Stéréologie de l’interface dermo-épidermique

The architecture and the plasticity of the dermo-epidermal interface of normal and pathological human skin have been studied by scanning electron microscopy. Biopsies were incubated in a sodium bromide solution to dissociate the epidermis from the dermis. The cleavage plane was located at the level of the lamina densa of the basal membrane as evidenced by optical and transmission electron microscopy. The surface on either side has digital projections, presenting on the epithelial side the relief of the basal cells and on the dermal side the complementary architecture. The highly folded basement membrane can be considerably stretched and its architecture can be modified by two processes. A passive type results from movement transmitted to the basement membrane in response to mechanical stress. An active type, depending upon metabolic remodelling, is illustrated by the dermal downgrowth of basal cell carcinoma.</jats:p

Les compartiments conjonctifs dans les sclérodermies

A combined histological and biomechanical study was performed in patients with localised or systemic scleroderma. The inflammatory reaction was variable in intensity and location, predominating around the superficial vascular plexus, the deep dermo-hypodermal plexus, the paraseptal plexus or in the fasciae. Secondary sclerosis resulted from the lateral fusion of bundles of collagen fibers. Three degrees of intensity of sclerosis were disclosed by our noninvasive technique of tonometry by vertical traction of the skin in vivo. That measurement allowed a follow-up of the evolution of the disease and a control of the therapeutic efficacy.</jats:p

Altération des loci minoris resistentiae du derme dans la photosclérose

The resistance to traction of the dermo-epidermal junction and of the superficial vascular plexus is altered by oral photochemotherapy. The dermo-epidermal junction is weakened when the resistance of vascular walls increases. These modifications are related to the histological alterations occurring during photosclerosis induced by PUVA.</jats:p