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Two different anti-ageing cosmetic actives based respectively, on dermal compartment regeneration and on dermoepidermal reinforcement, have been developed using tissular engineering models. Conjointly use of different innovative three-dimensional models such as reconstructed dermis and skin built with human cells coming from variable aged donors allowed first, a better understanding of matrix modifications due to ageing and second, the screening of active ingredients highly targeted to reverse observed damages. The validity of such three-dimensional models has been then confirmed by in vivo studies on healthy volunteers.

THE MECHANISMS OF ACTION ALREADY KNOWN: In vitro, chondroïtin sulfate ACS4-ACS6 have a dose-dependent inhibiting effect on the catabolism of proteoglycanes and collagen. They also stimulate the synthesis of extracellular matrix macromolecules. The existence of a chondrocyte cyto-protector effect and a potentially chondro-protective effect has also been demonstrated. ANOTHER MECHANISM OF ACTION: A new regulation route of chondrocyte metabolism has been proposed in which the Insulin Growth Factor (IGF-1) impedes the catabolic effects of another cytokine, Interleukin 1 (IL-1), by increasing its antagonistic receptor. This control appears essential in the maintenance extracellular matrix homeostasis. CARTILAGE WITH OSTEOARTHRITIS: Chondrocytes from OA cartilage have the capacity to produce more constituting macromolecules of the extracellular matrix. Conversely, these same cells have a greater catabolic capacity. The enhanced activity of IL-1 and the concomitant decrease in its antagonistic receptors leads to the reduction in macromolecule levels in the extracellular matrix, produced in the Cell-associated matrix of OA chondrocytes. ANTI-CATABOLIC EFFECT: It has been demonstrated that ACS4-ACS6 are capable of neutralizing the enhanced catabolic capacity of activated human OA chondrocytes.

Fibronectin is a dimeric glycoprotein found in the extracellular matrix of most tissues, which can influence processes, including cell growth, adhesion and migration. Fibronectin synthesis has been shown to be overexpressed in hypertension. However, the respective effects of humoral factors, including angiotensin II, versus mechanical factors in vascular remodeling have not yet been clarified. To study fibronectin de novo synthesis in the arterial wall, we have developed a new model for organ culture of rabbit thoracic aorta. Arteries held at their in vivo length were incubated and perfused (40 ml/min) in DME medium containing antibiotics, supplemented with 20% fetal calf serum or with 5% bovine serum albumin. In a series of experiments, angiotensin II (10(-6) M) and indomethacin (10(-5) M) were added to culture media. Vessels were pressurized at 0, 80 or 150 mmHg, and kept for 3 days in incubator at 37 degrees C under 5% CO2. De novo synthesis of fibronectin was detected by immunofluorescence using anti-cellular fibronectin antibodies (1/200). In the absence of angiotensin II and serum, fibronectin was expressed in the sub-endothelium at 80 mmHg, and in the inner media at 150 mmHg. In the presence of serum, fibronectin expression was increased by the high pressure. When angiotensin II was added, a gradient of fibronectin became apparent in the inner media at 80 mmHg with a marked expression at the luminal side. Angiotensin II markedly enhanced fibronectin expression at 150 mmHg, the protein being detected in almost the whole media. Our results indicate that both angiotensin II and transmural pressure can induce fibronectin expression in the arterial wall, and both act synergically.

There are during aging quantitative and qualitative alterations of the macromolecular components of extracellular matrix. The aim of our work was a comparative study of the biosynthesis of fibronectin, an adhesive molecule playing a role in the maintenance of tissue structure and function, with cultures of normal fibroblasts at different passages and the correlation with mRNA levels. There was an increased biosynthesis of fibronectin during fibroblast senescence as well as an increased mRNA coding for fibronectin. This suggests that fibronectin is a biomarker for replicative age.

This study was designed to complete the cell culture test for the cytotoxicity assessment of dental material presented by Christen et al. (1989) and Regad et al. (1989). Two liner materials were selected for this experiment which had already been subjected to both in vivo and in vitro tests. After 2, 7 and 14 days of contact with the test materials, the cell responses were evaluated under the light microscope by their growth pattern and morphological aspects. Cell synthesis of fibronectin and type I and III collagen was studied by immunofluorescence. Surface appearance of the cells in contact with the materials as well as their structures were observed by scanning electron microscopy. This study confirmed the viability of the in vitro cytotoxicity assessment methods with cell cultures. The results also demonstrated the potentials of this method in the early screening of dental materials for their biological compatibility.

It could be demonstrated that plasma and tissue fibronectin (FN) increase with age. Some age dependent diseases as diabetes, osteoarthritis and Werner syndrome produce also an increase of tissue fibronectin biosynthesis. Plasma fibronectin decreases in diabetes and in breast cancer. Alternative splicing of the FN gene appears also to vary with age and in some related pathologies. Nutritional status and UV light also influence FN biosynthesis. It appears therefore that the determination of plasma FN and its isoforms as well as the study of tissue FN may be of interest for the study of chronological aging and related pathologies.

Fibronectins are a class of high-molecular-weight glycoproteins found in a soluble form in blood and other body fluids and in an insoluble form in tissues. Cellular and plasma fibronectins are very similar in structure and properties, but are not identical. Fibronectins are synthesized by a wide variety of cells in vitro including fibroblasts, Schwann cells, chondrocytes, myoblasts, macrophages, hepatocytes and intestinal epithelial cells. They exhibit an affinity for both native and denatured forms of collagen, fibrinogen or fibrin, glycosaminoglycans, proteoglycans and surfaces of many kinds of eukaryotic cells. Fibronectins also bind to bacteria, viral glycoproteins and some protozoan parasites and interact with complement components. As a result of these multiple interactions, fibronectins might act as a non-specific opsonin. Fibronectins have been implicated in a variety of cell functions including cellular adhesion and morphology, cytoskeletal organization, oncogenic transformation, cell migration, phagocytosis, haemostasis and embryonic differentiation.

Studies during recent years have shown the importance of the vascular endothelium in several physiological and pathological circumstances. The culture of endothelial cells has permitted the direct study of endothelial functions. The endothelium is a selective barrier between blood and tissues: the molecules cross it, according to their size, either through the intercellular junctions or through the cells by pinocytotic vesicles. The permeability is modulated by vasomotor agents and modified during endothelial regeneration, especially for the lipids. The endothelium plays a prominent part in the maintenance of the blood flow through its nonthrombogenic properties. It metabolizes circulating thrombogenic substances (arachidonic acid, adenosine diphosphate) and produces potent antiaggregating agents (prostacyclin and adenosine). It may also release a plasminogen activator promoting thrombolysis. The endothelial cells contribute to the formation of the basement membrane by synthesizing collagen and fibronectin, which are involved in platelet adhesion and aggregation to exposed subendothelium. On the other hand, the endothelium has a modulating influence on the local blood flow by producing vasoconstrictors (angiotensin II and III) and vasodilating agents (adenosine and prostacyclin). It is not necessary to elucidate the coordination of these functions and their relationship to the endothelial disorders in vascular diseases.