Comparative biochemistry of human skin: glycosaminoglycans from different body sites in normal subjects and in patients with localized scleroderma.

OBJECTIVES: The aim of this investigation is to compare the relative proportions of disaccharides of chondroitinase-digestible glycosaminoglycans (GAGs) among the different body sites in control human skin and in the skin lesions of patients with localized scleroderma. METHODS: The disaccharide relative proportions were determined using high-performance liquid chromatography (HPLC). RESULTS: DeltaDi-4S, the main disaccharide unit of dermatan sulphate (DS), was the major skin GAG disaccharide (approximately 70% of the total) in control skin among all different body sites studied here. In scleroderma there was an increase in the relative proportion of both deltaDi-HA, the main disaccharide unit of hyaluronic acid (HA), and deltaDi-diS(B) (alpha-deltaUA(2SO4)-1-->3-GalNAc(4SO4)), derived from DS, and a decrease in deltaDi-4S, as compared with the uninvolved skin or the site-matched control skin. CONCLUSION: DS is the major GAG species in normal skin from different body sites. In addition, our results suggest a decrease and also a structural change in DS and an increase in the proportion of HA in scleroderma skin.

Astroglial cells derived from lateral and medial midbrain sectors differ in their synthesis and secretion of sulfated glycosaminoglycans.

Astroglial cells derived from lateral and medial midbrain sectors differ in their abilities to support neuritic growth of midbrain neurons in cocultures. These different properties of the two types of cells may be related to the composition of their extracellular matrix. We have studied the synthesis and secretion of sulfated glycosaminoglycans (GAGs) by the two cell types under control conditions and beta-D-xyloside-stimulated conditions, that stimulate the ability to synthesize and release GAGs. We have confirmed that both cell types synthesize and secrete heparan sulfate and chondroitin sulfate. Only slight differences were observed between the proportions of the two GAGs produced by the two types of cells after a 24-h labeling period. However, a marked difference was observed between the GAGs produced by the astroglial cells derived from lateral and medial midbrain sectors. The medial cells, which contain derivatives of the tectal and tegmental midline radial glia, synthesized and secreted approximately 2.3 times more chondroitin sulfate than lateral cells. The synthesis of heparan sulfate was only slightly modified by the addition of beta-D-xyloside. Overall, these results indicate that astroglial cells derived from the two midbrain sectors have marked differences in their capacity to synthesize chondroitin sulfate. Under in vivo conditions or a long period of in vitro culture, they may produce extracellular matrix at concentrations which may differentially affect neuritic growth.

Astroglial cells derived from lateral and medial midbrain sectors differ in their synthesis and secretion of sulfated glycosaminoglycans

Astroglial cells derived from lateral and medial midbrain sectors differ in their abilities to support neuritic growth of midbrain neurons in cocultures. These different properties of the two types of cells may be related to the composition of their extracellular matrix. We have studied the synthesis and secretion of sulfated glycosaminoglycans (GAGs) by the two cell types under control conditions and ß-D-xyloside-stimulated conditions, that stimulate the ability to synthesize and release GAGs. We have confirmed that both cell types synthesize and secrete heparan sulfate and chondroitin sulfate. Only slight differences were observed between the proportions of the two GAGs produced by the two types of cells after a 24-h labeling period. However, a marked difference was observed between the GAGs produced by the astroglial cells derived from lateral and medial midbrain sectors. The medial cells, which contain derivatives of the tectal and tegmental midline radial glia, synthesized and secreted ~2.3 times more chondroitin sulfate than lateral cells. The synthesis of heparan sulfate was only slightly modified by the addition of ß-D-xyloside. Overall, these results indicate that astroglial cells derived from the two midbrain sectors have marked differences in their capacity to synthesize chondroitin sulfate. Under in vivo conditions or a long period of in vitro culture, they may produce extracellular matrix at concentrations which may differentially affect neuritic growth

Contribution of heparan sulfate to the non-permissive role of the midline glia to the growth of midbrain neurites.

Radial glial cells and astrocytes are heterogeneous with respect to morphology, cytoskeletal- and membrane-associated molecules and intercellular interactions. Astrocytes derived from lateral (L) and medial (M) midbrain sectors differ in their abilities to support neuritic growth of midbrain neurons in coculture (Garcia-Abreu et al. J Neurosci Res 40:471, 1995). There is a correlation between these abilities and the differential patterns of laminin (LN) organization that is fibrillar in growth-permissive L astrocytes and punctate in the non-permissive M astroglia (Garcia-Abreu et al. NeuroReport 6:761, 1995). There are also differences in the production of glycosaminoglycans (GAGs) by L and M midbrain astrocytes (Garcia-Abreu et al. Glia 17:339, 1996). We show that the relative amounts of the glycoproteins laminin LN, fibronectin (FN) and tenascin (TN) are virtually identical in L and M glia, thus, confirming that an abundant content of LN is not sufficient to promote neurite growth. To further analyze the role of GAGs in the properties of M and L glia, we employed enzymatic degradation of the GAGs chondroitin sulfate (CS) and heparan sulfate (HS). Treatment with chondroitinase has little effect on the non-permissive properties of M glia but reduces the growth-supporting ability of L glia. By contrast, heparitinase I produces no significant changes on L glia but leads to neurite growth promotion by M glia. Taken together, these results suggest that glial CS helps to promote neurite growth and, more importantly, they indicate that a HS proteoglycan is, at least, partially responsible for the non-permissive role of the midline glia to the growth of midbrain neurites.