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

Abstract

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-Dxyloside-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-Dxyloside. 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.

Chondroitin and keratan sulfates have opposing effects on attachment and outgrowth of ventral mesencephalic explants in culture

“…These explants are composed of various neuronal and glial cell types that can each contribute to the adhesion and outgrowth of the explant. For example, the mesencephalic astrocytes present in the explants potentially produce extracellular matrix at concentrations that may affect neuritic adhesion and growth (Meiners et al, 1995; Onofre et al, 2001). The experiments will not have affected the matrix within the explants because only the substrate was treated, but the digestion may have altered the adhesive properties of the other cells in these explants, with possible consequences on the DA neuronal behavior.…”

Sulfated proteoglycans as modulators of neuronal migration and axonal decussation in the developing midbrain

“…Treatment of glial cultures with xyloside, that impairs the synthesis of CSPGs and causes pronounced release of soluble CS, revealed an enormous capacity of medial glia to secrete CS (41). Both treatment with xyloside and addition of exogenous CS-4, the major chondroitin form in midbrain glia (41), showed concentration-dependent, regionally specific effects (42).…”

“…Treatment of glial cultures with xyloside, that impairs the synthesis of CSPGs and causes pronounced release of soluble CS, revealed an enormous capacity of medial glia to secrete CS (41). Both treatment with xyloside and addition of exogenous CS-4, the major chondroitin form in midbrain glia (41), showed concentration-dependent, regionally specific effects (42). Thus, treatment of lateral astrocytes with xylosides resulted in a minor increase in the length of neurites while addition to the same glial type of CS-4 resulted in a U-shaped curve with a significant decrease of neurite length at intermediate concentrations (about 2.5 nM; Figure 2) (42).…”