Nerve growth factor, not laminin, is the major neurite-promoting component in medium conditioned by mouse L929 fibroblast cells

Collagen vitrigel membrane useful for paracrine assays in vitro and drug delivery systems in vivo

We previously succeeded in converting a soft and turbid disk of type-I collagen gel into a strong and transparent vitrigel membrane utilizing a concept for the vitrification of heat-denatured proteins and have demonstrated its protein-permeability and advantage as a scaffold for reconstructing crosstalk models between two different cell types. In this study, we observed the nano-structure of the type-I collagen vitrigel membrane and verified its utility for paracrine assays in vitro and drug delivery systems in vivo. Scanning electron microscopic observation revealed that the vitrigel membrane was a dense network architecture of typical type-I collagen fibrils. In the crosstalk model between PC-12 pheochromocytoma cells and L929 fibroblasts, nerve growth factor (NGF) secreted from L929 cells passed through the collagen vitrigel membrane and induced the neurite outgrowth of PC-12 cells by its paracrine effect. Also, the collagen vitrigel membrane containing vascular endothelial growth factor (VEGF) showed sustained-release of VEGF in vitro and its subcutaneous transplantation into a rat resulted in remarkable angiogenesis. These data suggest that the collagen vitrigel membrane is useful for paracrine assays in vitro and drug delivery systems in vivo.

HNK-1 carbohydrate-mediated cell adhesion to laminin-1 is different from heparin-mediated and sulfatide-mediated cell adhesion

The sulfated HNK-1 carbohydrate present on glycolipids and on several neural recognition molecules has been shown to mediate the adhesion of murine small cerebellar neurons and astrocytes to the extracellular matrix molecule laminin-1. In this study, we characterized the binding of the HNK-1 carbohydrate to laminin-1 extracted from the Engelbreth-Holm-Swarm (EHS) sarcoma and distinguished it unequivocally from binding sites for other sulfated carbohydrates. Electron microscopic analysis of rotary shadowed complexes of laminin-1 and a HNK-1 neoglycoprotein revealed a major binding site on the G domain that comprises the C-terminal globule of the laminin alpha1 chain. The HNK-1 carbohydrate also interacted with placental laminin isoforms containing an alpha chain variant. It bound to the proteolytic laminin-1 fragment E8 comprising the domains G1-G3, but not to fragment E3 that carries the major heparin-binding site on domains G4-G5. No binding was observed to the short arm containing fragments E1XNd or P1. Binding studies with native or denatured laminin E8 fragments and proteolytic or recombinant fragments of the G domain localized the HNK-1 carbohydrate binding site to domain G2. The binding could be clearly distinguished from binding sites for other sulfated carbohydrates such as heparin and sulfatides. Further, the binding could not be abolished by reduction and alkylation or by urea treatment of laminin-1 and was independent of the native conformation of laminin-1 and of Ca2+. The G2 domain is also involved in the adhesion of HNK-1 carbohydrate expressing early postnatal cerebellar neurons and is different from heparin- and sulfatide-mediated cell adhesion to laminin-1. HNK-1 carbohydrate-mediated cell adhesion appears, however, to be dependent on the native conformation of laminin-1 indicating a more complex cellular recognition process.

Functional involvement of sciatic nerve-derived versican- and decorin-like molecules and other chondroitin sulphate proteoglycans in ECM-mediated cell adhesion and neurite outgrowth

We have previously described two proteoglycans from human sciatic nerve which are immunochemically related to the chondroitin sulphate proteoglycans versican and decorin. The chondroitin sulphate of the versican-like molecule and the core protein of the decorin-like molecule have been found previously to be up-regulated after lesioning the adult mouse sciatic nerve. To investigate if the versican- and decorin-like molecules are involved in cell-extracellular matrix interactions, we studied the effect of both molecules on cell adhesion. The versican- and decorin-like molecules, substrate-coated in a mixture with fibronectin, but not with laminin or collagen types I or IV, inhibited the adhesion of several cell lines, neonatal dorsal root ganglion neurons and Schwann cells. The inhibitory activity was concentration-dependent and mediated by the chondroitin sulphate. Furthermore, when different proteoglycans were incubated with fibronectin, only the versican- and decorin-like molecules and the chondroitin sulphate proteoglycan aggrecan, but not the heparan sulphate proteoglycan perlecan, were able to inhibit fibronectin-mediated cell adhesion. The versican- and decorin-like molecules, substrate-coated alone or in a mixture with fibronectin or laminin, were at most slightly inhibitory to neurite outgrowth from PC12 phaeochromocytoma cells and neonatal dorsal root ganglion neurons. In a solid-phase ligand-binding assay the versican- and decorin-like molecules interacted with fibronectin, but not with laminin or collagen types I and IV. Binding of the versican-like molecule to fibronectin and inhibition of cell adhesion by this molecule was mediated via the heparin and cell-binding domains of fibronectin. These observations suggest that binding of the two proteoglycans to fibronectin is involved in the modulation of adhesion of cells to fibronectin.

Tenascin-R (J1 160/180 inhibits fibronectin-mediated cell adhesion--functional relatedness to tenascin-C

Cell adhesion and neurite outgrowth on fibronectin is a multistep process modulated by different extra- and intracellular signals. Fibronectin-mediated cell attachment and spreading can be affected in a negative way by tenascin-C, an extracellular matrix glycoprotein expressed in a temporally and spacially restricted manner during early morphogenesis. Tenascin-R (J1-160/180), consisting of two major isoforms of 160 kDa (tenascin-R 160) and 180 kDa (tenascin-R 180) in mammals, is an extracellular matrix glycoprotein of the central nervous system that shares high structural homologies with tenascin-C. Here we show that in relation to fibronectin-mediated adhesion, the two extracellular matrix molecules are also functionally closely related. When offered as mixed substrata with other extracellular matrix molecules, the two tenascin-R isoforms and tenascin-C derived from mouse brain selectively inhibit fibronectin-dependent cell adhesion and neurite outgrowth, and affect cell morphology of different mesenchymal and neural cells. This effect is partially due to interactions at the substrate level that result in a steric hindrance and/or conformational change of the cell binding sites of the fibronectin molecule. In addition, tenascin-R 180 and tenascin-C interact with cells by an RGD- and beta 1 integrin-independent mechanism, leading to cell rounding and detachment from such substrata. The expression of tenascin-R and tenascin-C in the nervous system at times and locations where fibronectin-mediated cellular processes take place may be related to the role of inhibitory signals in the extracellular matrix in the regulation of cell migration and differentiation in general.

Isolated hepatic granulomas from mice infected with Schistosoma mansoni contain nerve growth factor

Nerve growth factor (NGF) is a neurotrophic factor essential for the development and maintenance of specific neuronal cell populations. In addition, NGF has biological effects on inflammatory cells. The aim of this study was to determine whether NGF is present in chronic inflammation, using isolated hepatic granulomas from mice infected with Schistosoma mansoni as the model. The schistosome granuloma is a complex T-cell-mediated immune response to the egg. Intact granulomas were isolated from the livers of infected mice and examined for the presence of NGF. In homogenized granuloma samples, radioimmunoassay and immunoblotting analyses detected an immunoreactive NGF that had the same molecular mass as that of purified murine NGF (13 kDa). Isolated granulomas cultured in vitro released soluble factor(s) with NGF-like neurite-promoting activity in a rat pheochromocytoma (PC12) bioassay. This activity was partially inhibited by a blocking anti-NGF antibody. There were two potential sources of this NGF-like neurite-promoting activity, either the schistosome egg or the host inflammatory response. Since neither isolated eggs nor soluble egg antigen had neurite-promoting activity, the inflammation was the source of this activity. The inability of the anti-NGF antibody to inhibit completely the granuloma-induced neurite outgrowth in the bioassay signifies that NGF is not the only neurotrophic factor present in these granulomas. The presence of NGF within the granulomas may indicate that NGF has a role in the granulomatous response.

Extension of sympathetic neurites in vitro towards explants of embryonic and neonatal mouse heart and stomach: ontogeny of neuronotrophic factors

In order to establish when target organs first produce neuronotrophic factors, extension of neurites in vitro from sympathetic ganglia (superior cervical and coeliac) of 1-day neonatal mice towards explants of 10-, 11-, 14- and 17-day embryonic and 1-day neonatal atrium and stomach was examined in co-cultures. Longer neurites extended from ganglia towards, than away from, atrial targets at all stages examined, and was most marked towards 17-day embryonic and neonatal explants. Treatment of atrial co-cultures with antiserum to nerve growth factor (NGF) almost totally blocked preferential neurite outgrowth. Directional growth of neurites towards stomach explants in co-cultures was not as pronounced as that towards atrium; extension of neurites was most marked when stomach was provided by 11-, 14- and 17-day embryos. Such outgrowth was only partially blocked by antiserum to NGF, significant preferential extension of neurites towards stomach persisting in the presence of the antiserum. These results indicate that atrium and stomach produce neuronotrophic factors from the earliest ages studied; the evidence indicates that in the case of atrium, NGF predominates but that stomach produces NGF as well as another factor immunologically distinct from NGF. It is of interest that both types of target explanted before they receive sympathetic innervation show evidence of producing NGF in culture.

Oligodendrocyte-derived J1-160/180 extracellular matrix glycoproteins are adhesive or repulsive depending on the partner cell type and time of interaction

We have studied the functional involvement of J1-160 and J1-180 in the interaction between oligodendrocytes and neurons, astrocytes, or L cells in short- and long-term adhesion assays using monoclonal antibodies directed against topographically distinct epitopes on the molecules. Whereas antibodies to mouse liver membranes and monoclonal antibody 597 do not interfere with neuron-oligodendrocyte or astrocyte-oligodendrocyte adhesion after 30 min of coculture, antibodies 596, 619, and 620 interfere with astrocyte to oligodendrocyte and neuron to oligodendrocyte adhesion. The adhesion of L cells to oligodendrocytes is not affected by the antibodies. When neurons or astrocytes are cultured on oligodendrocytes for more than 30 min, monoclonal antibody 619 continues to reduce adhesion of astrocytes to oligodendrocytes after 1 and 2 h. However, during this time period the antibody affects neuron to oligodendrocyte adhesion in a different manner. It does not interfere with adhesion of neurons to oligodendrocytes at 1 h and enhances the adhesion of neurons to oligodendrocytes after 2 h of coculture. After 6 and 24 h of coculture, antibody 619 does not affect the adhesion of neurons or astrocytes to oligodendrocytes, suggesting that other adhesive mechanisms are predominant at later times of interaction. At all times studied, neurons and astrocytes adhered well to the oligodendrocytes. To study the influence of the J1 molecules on neuronal interactions in the absence of other oligodendrocyte-derived cell surface components, purified J1-160 was coated as a substrate and neuron attachment was measured as a function of time. Two hours after plating neurons adhered well to J1-160, as they did to laminin, while cell detachment was subsequently observed from J1-160, but not from laminin. These results implicate J1-160 and J1-180 in a recognition process between oligodendrocytes and neurons or astrocytes, but not fibroblasts. This recognition process appears to merge into adhesion or stabilization of cell contacts for astrocytes and destabilization of cell interactions or repulsion for neurons. It is likely that these two opposite effects in cell behavior elicited by the J1 molecules result from differential intracellular responses to a cell surface trigger possibly mediated by different cell surface receptors and/or different consequences in intracellular signaling networks.

Localization of the nerve growth factor receptor on fetal human Schwann cells in culture

Previous studies have established that Schwann cells (SC) in culture express an NGF receptor. In this study, cultures of fetal human SC were established from fetal nerves and various light microscopic (LM) and electron microscopic (EM) techniques were used to localize the NGF receptor on the SC. Results indicate that NGF receptor is localized to the plasma membrane of the SC. Quantitative digital analysis determined that the distal portion of the SC process had high concentrations of NGF receptor. The possible functional significance of this latter observation is discussed in terms of SC migration and ensheathment of axons.

Detection of a nerve growth factor receptor on fetal human Schwann cells in culture: absence of the receptor on fetal human astrocytes

Cultures of human Schwann cells and astrocytes were established from fetal nerves and brains respectively. The human Schwann cells in culture expressed a nerve growth factor (NGF) receptor as determined by indirect immunofluorescence, autoradiography, and immunoprecipitation. In contrast, the human astrocytes in culture did not have an NGF receptor. Cultures of rat Schwann cells and astrocytes were also established for comparison, with similar results. The rat Schwann cells had an NGF receptor whereas the astrocytes did not. The functional significance of this NGF receptor on Schwann cells, as well as the lack of the receptor on astrocytes, is discussed.