H. Bouissou

The elastic tissue of the skin: a comparison of spontaneous and actinic (solar) aging

ABSTRACT: In order to separate the changes of actinic damage from those of simple aging, we studied the elastic fibers in low and high sun‐exposed skins of normal subjects at different ages. Low sun‐exposed skin shows chronologic aging lesions only. These begin at age 30 with a disappearance of oxytalan fibers and with some abnormalities in the reticular and deep dermis; at age 40, aging changes are established: no oxytalan fibers, marked abnormalities, and lysis of elaunic and elastic fibers. In high sun‐exposed skin, age‐related lesions also occur but are associated with more or less precocious elastotic degeneration in reticular and deep dermis. Both types of aging fibers are revealed by the antielastin antibody HB 8, disappear with elastase, but resist collagenase. Actinic elastosis clearly originates from elastin. The two types of change differ in electron microscopic appearance: with spontaneous aging, elastic fibers are desintegrated (loose and porous fibers); in actinic damage, elastotic fibers are thicker and have accentuated microfiabril dense masses. The age‐associated lesions could be due to the activity of protease of fibroblastic origin whereas the elastotic degeneration is probably due to the actinic stimulation of fibroblasts.

Fibroblast changes in cutaneous ageing

With ageing there are progressive modifications in the connective tissue of the dermis. In ten young subjects the collagenous bundles are thick and the fibroblasts are active cells in close contact with collagen fascicles. In ten elderly subjects collagen fibres are fragmented and the fibroblasts are quiescent, without any contact with collagen. In ageing the most important lesion is the destruction of the relationship between fibroblasts and interstitial matrix. A role for fibronectin in this adhesion is suggested: in old subjects the papillary network of fibronectin is poorly developed. Furthermore, in the fibroblast we can see architectural changes in the cytoskeleton; this modification breaks up the cytoskeleton - plasma membrane - fibronectin unit and explains the secretory and metabolic changes observed in ageing, the dysfunction of the cell-interstitial matrix unit, and also the structural changes.

Age-related changes in the elastic tissue of the human thoracic aorta

Thirty human aortas with varying degrees of atheroma graded macroscopically according to the WHO classification were taken at autopsy from subjects of different ages (24-86 years). Study by light microscopy showed aortas with an intact wall (4 subjects, 25-46 years) with a thin intima and regular elastic layers, and aortas with varying degrees of modification of the wall, where the intima was of varying thickness and the elastic fibers showed varying degrees of damage (moderate lesions: 5 subjects, 35-52 yrs; severe lesions: 21 subjects, 26-86 yrs). From each aorta, a 4-cm segment from the tunica media, free of atheromatous lesions, was defatted and subjected to successive treatment with EDTA-Tris, 6 M guanidine-HCl-Tris, 6 M guanidine-HCl-Tris-DTE and collagenase. The residues (EP residues) were subjected to amino acid (AA) analysis and transmission electron microscopy (TEM) study. In the young subject, the AA composition was similar to that of elastin and the TEM images were characteristic of this substance. In the aging subject, an increase in polar AA and a parallel decrease in apolar AA and crosslinks was noted. By TEM, the elastin was seen to be associated with abundant fibrillar material. Trypsin treatment of EP residues gave E residues, whose composition and TEM appearance were similar in all samples, corresponding to the standard composition of elastin and its classic appearance by electron microscopy. We suggest that the fibrillar material removed by trypsin is the morphological reflection of the chemical variations observed in the EP residues. These correspond to contamination of the elastin by a polar protein fraction. This contamination is closely correlated with age but not with the degree of atheroma. Thus the age-related chemical changes in elastin appear to be independent of the onset and evolution of atheromatous lesions. The 10-15 nm diameter of the contaminating fibrillar material suggests that may be the microfibrillar fraction of elastic tissue.

Fibroblasts in Dermal Tissue Repair.: Electron Microscopic and Immunohistochemical Study

ABSTRACT: The cellular dynamics of dermal regeneration were studied in nonsutured cutaneous wounds of female pigs and monkeys with electron microscopy and immunohistochemistry to demonstrate the origin and the development of fibroblasts forming granulation tissue. The results indicate that fibroblasts do not originate from histiocytes but from resting fibroblasts in the wound margins. These resting fibroblasts first become undifferentiated mesenchymal cells termed “X” cells. The “X” cells then multiply, migrate, and invade the wound defect in approximately 3 days, transforming into highly active fibroblasts. The active fibroblasts are endowed with the capacity of further transformation to fibroclasts and myofibroblasts. The latter two cell populations then effectively cause remodeling of newly formed tissue and contraction of wound margins.

Identifying arteriosclerosis and aortic atheromatosis by skin biopsy

Summary Photonic and ultrastructural examination of skin biopsies accurately reflect the condition of vascular walls. A normal skin type 0 is the equivalent of normal vessels, while skin types II and III correspond to arteriosclerotic aortic and coronary vessels. The test is primarily valuable to establish whether a premature arteriosclerosis exists. Estimate of skin lipids — total lipids and total sterols — is a diagnostic test which permits us to establish the degree of atheroma of an individual. Levels of these lipids and the degree of atheroma run parallel. By its histological and biological study, skin biopsy can become an accurate test reliably reflecting the condition of the aorta (atherosclerosis and atheromatosis).

Striae: Morphological aspects of connective tissue

The study of 15 abdominal striae in women aged 25 to 57 shows important histological modifications in the skin. The collagen is fragmented and the ground substance is abundant. Fibroblasts are globular, quiescent, and lose all signs of fibrillar secretion. In the light of the recent biochemical data, our results suggest that the striae are the consequence of fibroblastic dysfunction, due to abdominal distension. Comparison with scarred and normal skin indicate that striae are a special entity belonging to the group of connective dystrophies.

Chronic lathyrism. Effect of β aminopropionitrile on the aortic wall in the adult rat

Summary BAPN did not have the same effect in weaning and adult rats. The BAPN was inactive on the aortic wall of adult rat but it induced clinical symptoms and severe aortic partietal lesions in the weaning rat. The explanation of this different lesions was difficult and some hypothesis were discussed. β Aminopropionitrile (BAPN) fumarate affects connective tissue components, particularly collagen and elastin of the aorta and the skin. These facts have been known since 1952, when Ponsetti and Baird induced aortic aneurism in the rat after acute intoxication with “Lathyrus odoratus” seeds. The precise action mechanism of this toxin was not absolutely clear as has been recalled by Kadar et al (1978) in one of her recent publications. In the growing rat, BAPN caused a defect in collagen and elastic synthesis by inhibiting lysine oxydase, an enzyme indispensable for interfibrillar cross-linking ( Bornstein, 1970 ), (Levene et al, 1959) (Page et al, 1966, 1968, 1972) (Wirtschafter et al, 1962) but it can also effect the glycoaminoglycan metabolism ( Bentley et al, 1970 ), (Hosoda et al, 1967), the aortic wall cells, myocytes (Hosoda et al, 1967) ( Julian, et al, 1971 , Julian, et al, 1971 ) endothelial cells ( Pieraggi et al, 1979 ) and cutaneous fibroblasts ( Bouissou et al, 1974 ) (Hosoda et al, 1967) ( Julian et al, 1973 ). In our previous experimentations ( Bouissou et al, 1978 ), ( Julian, et al, 1971 , Julian, et al, 1971 , Julian, et al, 1972 , Julian, et al, 1976 ) with the young weaning rat, chronic administration of BAPN (lg/kg/day for 9 weeks) did not induce aneurism but considerable lesions of the aortic wall : increased endothelial permeability, dedifferenciation of the myocytes in fibromyocytes, proteoglycan diffusion, changes in the elastic network (breaking, fragmentations or complete lysis of fibers) and late fibrosis (Fig. 1). These changes may be intimately related to those of human aortic arteriosclerosis ( Bouissou et al, 1974 ) ( Julian et al, 1973 ). In these different experimental stages, the greatest aortic partietal changes appeared a few weeks after BAPN treatment was stopped, i. e. in adults rats. These findings raised the problem of the effect of this toxic on the mature aortic connective tissue.

Cutaneous cholesterol and plasma lipoproteins in elderly active and bedridden patients compared with young adults.

This report concerns two groups of elderly patients, one active and the other inactive with cardiovascular histories. Cutaneous and plasma cholesterol (Ch) and the lipoprotein fractions were analyzed in each group and compared with those of a young group. The cutaneous histological ageing type was studied in the three groups. No histological difference was seen to exist between the elderly populations (skin type II), the young group had normal type O skin. A significant difference was seen to exist between the levels of cutaneous Ch of the two elderly groups and that of the young group. Changes in the cutaneous Ch with respect to the ratio (total Ch/HDL Ch) were found to differ in the two elderly groups: the active elderly patients presented a positive correlation as did the young subjects but the inactive patients showed a negative correlation.

Fine structural evidence of increased endothelial permeability in chronic lathyrism

The endothelium of the thoracic aorta of Wistar rats intoxicated with Beta-Aminopropionitrile (BAPN) for 9 weeks was studied. The animals were sacrificed at intervals, from the first to the 9th week of the treatment and 1, 2 and 3 months after the end of the treatment. Changes in the endothelial cells were studied by electron microscopy after staining with uranyl acetate and lead citrate, after impregnation with lanthanum. BAPN increased endothelial permeability, pinocytosis was more active in treated rats than controls, the intercellular junctions widened and cytoplasmic lesions with cell necrosis occurred. These intimal changes were comparable to those observed in man during ageing and in arteriosclerosis.

Chronic lathyrism and atheromatosis in the rat

Temporary chronic administration of Beta-amino-propionitrile (B.A.P.N.) produced morphological and biochemical changes of the aortic wall of rat as well as abnormalities of the plasma lipid levels. A hyperlipidic diet resulted in the blood plasma lipid abnormalities as B.A.P.N. intoxication. Nine weeks of B.A.P.N. followed by 42 weeks of a hyperlipidic diet increased the aortic cholesterol level and induced an atheroma. The diet alone produced only an endothelial lipid overload. The structure of arterial wall played the decisive role in atherogenesis.