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Hyaluronic acid, or hyaluronan, is a polymer made of the repetition of a unique disaccharidic unit, D-glucuronic acid and D-N-acetylglucosamine, that can reach a molecular mass of 10(7) daltons. This primitive polymer has emerged as a remarkable extracellular matrix component by its viscoelastic properties, its hygroscopic capacities and the diversity of cell processes it controls. Identified in all vertebrate tissues, more than 50% of acid hyaluronic of the organism is present in skin. Having no protein core, its synthesis is performed through a unique process, depending on enzymatic activity of hyaluronan synthases acting at the internal face of the plasmatic membrane and extruding the nascent polymer to the extracellular medium. This polymer constitutes a scaffold on which a large number of sulfated proteoglycans, up to one hundred, can be linked. These supramolecular structures of considerable size are able to entrap large amounts of water and ions to provide tissues with hydration and turgescence. Hyaluronic acid is recognized by cell membrane receptors, notably CD44 which is the best known. Interaction of hyaluronic acid with its receptors triggers several intracellular signaling pathways regulating proliferation, migration and differentiation. Cell response is largely influenced by the size of the polymer and by that of the fragments generated upon degradation by hyaluronidases or free radicals. Hyaluronic acid is metabolically very active, as, for example, its half-life in skin is less than one day. Detected in epidermis where it could play a role in the control of proliferation and differentiation of basal cells, it is however prominent in dermis in association with versican. The remarkable physicochemical properties of hyaluronic acid as well as the diversity of biological processes it controls largely surpass the primitive character of this polymer.

Hyaluronan (HA) is a key component of the extra-cellular matrix and is involved in several mechanisms of the wound healing process. It is highly hygroscopic and is involved in the visco-elasticity of the skin. The properties of this molecule depend on its molecular weight. Native high molecular weight HA has structural properties whereas HA degradation products (oligomers) stimulate endothelial cell proliferation and migration. HA oligomers modulate inflammatory processes and promote neo-angiogenesis during the different steps of wound healing. HA mediates its biological effects through binding interactions with specific cell-associated receptors (CD44 and RHAMM). The tridimensional structure of HA is variable and acts as a framework for cell adhesion and migration. Thanks to its different physico-chemical properties, hylaluronic acid is very useful in the biomedical field.

Hyaluronic acid (HA), one of the main components of extra-cellular matrix and most notably of the fundamental substance of conjunctive tissues, is not an inert structure. Conversely, it displays important biological properties and plays a significant role in crucial physiological processes especially when cellular plasticity is involved such as inflammation, immune reactions, angiogenesis and would healing. It is also strongly involved in neoplastic cells migration and therefore in metastatic spreading of malignant tumours. These varied physiological functions are related either to interactions with specific or less specific cellular membrane receptors or to the production of HA fragments of different sizes, generated for example by local traumatism or inflammation, fragments displaying specific properties according to their size.

To study the prognostic value of tumour diameter, TNM stage, Führman's nuclear grade and CD44 adhesion molecule expression in renal cell carcinoma (RCC) before the age of 40 years.Nineteen patients under the age of 40 (12 males and 7 females; mean age 30.8 years), undergoing total nephrectomy for RCC were included in this study. Tumour diameter, TNM 1997 stage, and Führman's nuclear grade were defined for each tumour. Standard CD44 adhesion molecule (CD44H) expression was evaluated semiquantitatively by immunohistochemistry on each tumour. The prognostic value of the various variables was determined by Mann-Whitney and Chi-square tests and survival analysis was performed by the Kaplan-Meier method.Six patients (31.5%) died from their cancer with a mean follow-up of 81.4 months. Mean tumour diameter was 9 +/- 4.5 cm. Tumours were Führman I/II in 4 cases, Führman III/IV in 15 cases, T1/T2 in 14 cases and T3/T4 in 5 cases. CD44H expression was high (or = 20%) in 9 cases (47.3%). The prognostic factors identified in this study were: tumour stage (p = 0.01), grade (p = 0.04), venous extension (p = 0.001) and CD44H overexpression (p = 0.003).Prognostic factors of renal cancer in patients under the age of 40 years do not appear to be different from those of older patients. The prognostic factors identified in this study must be validated by multicentre studies based on larger populations.

Immunohistochemistry has been used to evaluate the relationship between the rate of CD44-H antigen expression in breast invasive intracanalicuar and cervical epidermoïd carcinomas and the presence of node metastasis. A total of 36 cases of breast carcinoma and 20 cases of cervical carcinoma was examined. For the two types of carcinoma, the CD44-H molecule was highly expressed in cases with node metastasis; with 50% and 75% median value of CD44-H positive tumor cells respectively for the breast (p0.02) and for the uterine cervix (p0.05) compared to respectively 10% and 37.5% in the cases without node metastasis. The expression of this molecule increases with invasive potential of tumor cells and the use of this antigen for prognostic ends may be possible.

So far no comparative studies have been conducted to know whether physiological influences related to sex hormonal differences affect the age-related changes of the immune system. The aim of this study was to investigate whether pregnancies and sex influence the age-related changes in the peripheral lymphoid compartment and functions of T cells in mice. Using flow cytometry, we examined changes in (Thy1.2+) T cells, (B220+) B cells and (CD11b/Mac-1+) macrophages in the spleen of multiparous and virgin females and males at 2, 8, 15 and 23 months of age. The development of naive (CD44low) and memory (CD44high) cells were investigated in CD4+ and CD8+ T cell subsets. To analyze the age-related changes in functions of T cells, we examined the secretion of some T cell immunoregulatory cytokines (IL-2, IL-4, gamma-interferon and GM-CSF) of in vitro Concanavalin A-activated spleen cells of C57BL/6 mice. Both short term (8 months) and long term (15-23 months) effects of pregnancies were obvious in the age-related changes of the immune system. Short term effect included delayed appearance of memory CD4+ cells and the preserved IL-2 production. At eight months, shortly after pregnancies, both parameters were higher in multiparous females. Later effects of pregnancies were evidenced by a higher level of macrophages (Mac-1+) than in other groups throughout life. The increased gamma-interferon, IL-4 and GM-CSF productions appeared earlier, at 15 months, IL-4 and GM-CSF levels remained higher in multiparous females than in virgin females and males in late adulthood. Sex differences were also noticed: males exhibited lower macrophage levels after one year and gamma-interferon secretion capacity than females in late life. This study underlines that the onset, magnitude and kinetics of the age-related changes in the distribution of immune cells and T cell functions are parity- and sex-dependent. These changes may influence the incidence of age-related diseases and may explain the greater longevity of women, especially the multiparous ones.

Angioplasty has become enormously popular since its introduction in 1979 for the treatment of arterial stenosis at coronary or other sites. The success rate is currently around 95%. Unfortunately, restenosis occurs in 30 to 40% of cases within six months of the procedure. Restenosis is the result of a number of events that are triggered by the angioplasty. These events involve both blood components (platelets, leukocytes, and plasma constituents) and arterial wall components (smooth muscle cells [SMCs], endothelial cells, and the extracellular matrix). Hyaluronate is a high-molecular-weight glycosaminoglycane found in the extracellular matrix of arterial SMCs and endothelial cells. Hyaluronate and its receptors (CD44 and RHAMM or receptor for HA-mediated motility) contribute actively to leukocyte adhesion and infiltration at experimental angioplasty sites. Studies of cell cultures have shown that leukocyte adhesion and migration are inhibited by substances (antibodies, peptides, high levels of hyaluronate) that prevent hyaluronate from binding to CD44 and RHAMM. Hyaluronate expression by arterial SMCs is modulated by the angioplasty-produced arterial lesion. The SMCs that migrate and divide actively at the arterial lesion site are those that express hyaluronate, CD44, and RHAMM. Hyaluronate both stimulates SMC migration via an effect on RHAMM and enhances SMC division via an effect on CD44. In animal studies, administration of high levels of hyaluronate to saturate hyaluronate receptors on leukocytes and SMCs was followed by inhibition of leukocyte infiltration into the damaged arterial wall and by a significant reduction in the arterial neointima. Hyaluronate, a compound with an excellent safety profile, may offer hope for the prevention of restenosis after angioplasty.

Disseminated neuroblastoma frequently show a very poor prognosis. N-myc gene amplification, 1p deletion and lack of CD44 gene expression, are all genetic factors associated with the disease's dissemination. Human neuroblastoma xenografts in nude mice has permitted to characterize, in disseminated neuroblasts, oncogenes overexpression, inactivation of tumor suppressor genes as well as detoxifying genes activation which contributes to increase cellular resistance to chemotherapy. These genetic abnormalities permit to propose a nosology of this very aggressive pediatric solid tumor. Hopefully, this genetic classification could be of great value for new therapeutic approaches.

The prognosis of pediatric neuroblastoma depends both on clinical presentation and on certain cellular and molecular characteristics. At the present time, two hypotheses can be drawn to explain both clinical and biological heterogeneity. In the first hypothesis, neuroblastoma progresses from early to late clinical stages through a classical multistep process linked to an accumulation of molecular abnormalities. In the second hypothesis, neuroblastoma represents an heterogeneous group of unrelated diseases, where most of stages I and II or stage IVS neuroblastomas can rather be considered as benign tumors, and stage IV neuroblastoma as a true malignant proliferation. To ascertain relevant biological factors for the prognosis of the disease, it is uppermost important that all investigators agree on biological criteria for analysis when neuroblastoma tissue is available in screened and unscreened populations. This paper reviews the biological tools available for prognosis in neuroblastoma, the priority for analysis of biological markers according to reliability, feasibility, and reproducibility of analysis procedure, and the conditions of tissue storage for further analysis of these biological markers. The standardized biological evaluation of neuroblastoma will allow, first, to collect sufficient data for multivariate analysis of prognostic factors and, second, to better define the putative links between various forms of the disease.

CD44 gene products are potential markers of aggressiveness in different tumor models, a result which prompted us to study clinical neuroblastoma (NB) specimens. CD44 expression was determined by immunostaining of 52 NB with a monoclonal antibody (J173) directed against an epitope common to all CD44 isoforms. All tumors were from patients (pts) with newly diagnosed NB treated with standardized protocols. They were classified according to international criteria [11]. CD44 immunoreactivity was detected in 37 tumors (71%). CD44 was expressed in 100% of favorable NB stages (1, 2 or 4S), but only 50% of advanced NB (stages 3 and 4) (p = 0.0001), suggesting that the absence rather that the overexpression of CD44 is a signal of tumor aggressiveness. The cumulative event-free survival was significantly longer in pts with CD44-positive tumors as compared to pts with CD44-negative tumors (p10(-5)). More importantly, progression-free survival was also significantly higher in CD44-positive pts within the high-risk group (p0.01). In univariate analyses, we tested the prognostic value of tumor expression of CD44 in comparison with tumor stage, age, tumor histology and presence or absence of N-myc proto-oncogene amplification. All five measures had significant prognostic value. The expression of CD44 and the absence of N-myc amplification were the most powerful predictors of a favorable clinical outcome. In a multivariate analysis of these measures, CD44 expression and tumor stage were the only independent prognostic factors for the prediction of patient survival. NB is the first clinical model described in which tumor aggressiveness correlates with a repression rather than a stimulation of CD44 expression. We recommend the use of CD44 as an additional biological marker in the initial staging of neuroblastoma.

The CD44 group of transmembrane glycoproteins encompasses several isoforms expressed in a variety of tissues. All isoforms are encoded by the same gene on chromosome 11 and are formed by alternative splicing of their mRNA. CD44 isoforms belong to the family of cell adhesion molecules and to the sub-family of the hyaladherins in consideration of their affinity for hyaluronate and their structural homology with the cartilage link protein. The standard form of CD44, CD44H exhibits a high affinity for hyaluronate, plays a role in the uptake and degradation of this glycosaminoglycan and participates in cell locomotion in its presence. In physiology, CD44H plays a role in the homing of lymphocytes into Peyer's patches, in organogenesis and in the degradation of hyaluronate in lung or lymphoid tissue. In pathology, CD44H probably enhances the tumorigenic properties of some lymphomas and melanomas. The variant form CD44E exhibits low affinity for hyaluronate and its role in cell-cell adhesion in epithelia is suspected. The variant form CD44V (or CD44M) confers metastatic properties to rat carcinoma cells and is expressed in human breast and colorectal cancer and in adenomatous polyps.

The coculture of fibroblasts with cancerous cells under the conditions which lead to spheroid formation, allowed the obtention of spheroids composed of a fibroblastic core surrounded by cancerous cells. The fibroblast core was labelled by hyaluronic acid and hyaluronectin. Hyaluronic acid concentration was also measured by enzymoimmunological assay in culture medium where it was found to accumulate during spheroid growth. The composite spheroid technique is a good model system for analysis of cancer cells-fibroblasts interaction in vitro.

Two techniques of affino-immunofluorescence were described to localize hyaluronic acid (HA) on Rat cerebellum tissue sections. The first technique used the direct soluble hyaluronectin (HN)/anti-HN immune complex fixation to tissue-HA. In the second technique, HN fixation was followed by anti-HN antibody binding to HN. Both reactions were blocked by the addition of HA to HN/anti-HN complexes or to HN. The first direct technique is less time consuming and gives more clear-cut results than the second technique. These affino-immunological methods provide a better tool to localize HA in tissues than the classical stainings.

G.F.A. (gliofibrillary acid protein) and hyaluronectin studied here are two antigens defined by the heteroantibodies which appear in the serum of the immunised animal. G.F.A. is associated with gliofilaments and is considered as an astrocyte marker, either normal or tumoral. Hyaluronectin, is found in the Ranvier nodes and at the periphery of neurones. It is not specific to the nervous system. It is found in all tissues and tumors, and in particular marks the intercellular spaces of gliomas, where it is associated with hyaluronic acid for which it has a great affinity. Serum estimation of these Proteins is being undertaken with the view to a clinical application.