Abstract.We have previously shown that aggregation of microbeads coated with N-CAM and Ng-CAM is inhibited by incubation with soluble neurocan, a chow droitin sulfate proteoglycan of brain, suggesting that neurocan binds to these cell adhesion molecules (Grumet, M., A. Flaccus, and R. U. Margolis. 1993. J. Cell Biol. 120:815). To investigate these interactions more directly, we have tested binding of soluble 125I-neurocan to microwells coated with different glycoproteins. Neurocan bound at high levels to Ng-CAM and N-CAM, but little or no binding was detected to myelin-associated glycoprotein, EGF receptor, fibronectin, laminin, and collagen IV. The binding to Ng-CAM and N-CAM was saturable and in each case Scatchard plots indicated a high affinity binding site with a dissociation constant of ~1 nM. Binding was significantly reduced after treatment of neurocan with chondroitinase, and free chondroitin sulfate inhibited binding of neurocan to Ng-CAM and N-CAM. These results indicate a role for chondroitin sulfate in this process, although the core glycoprotein also has binding activity. The COOH-terminal half of neurocan was shown to have binding properties essentially identical to those of the full-length proteoglycan.To study the potential biological functions of neurocan, its effects on neuronal adhesion and neurite growth were analyzed. When neurons were incubated on dishes coated with different combinations of neurocan and Ng-CAM, neuronal adhesion and neurite extension were inhibited. Experiments using anti-Ng-CAM antibodies as a substrate also indicate that neurocan has a direct inhibitory effect on neuronal adhesion and neurite growth, lmmunoperoxidase staining of tissue sections showed that neurocan, Ng-CAM, and N-CAM are all present at highest concentration in the molecular layer and fiber tracts of developing cerebellum. The overlapping localization in vivo, the molecular binding studies, and the striking effects on neuronal adhesion and neurite growth support the view that neurocan may modulate neuronal adhesion and neurite growth during development by binding to neural cell adhesion molecules.

Barnea et al., 1994;Maurel et al., 1994). It has been expressed on the surface of glial cells binds to the shown that the expression of RPTPβ is restricted to the glycosylphosphatidylinositol (GPI)-anchored recogninervous system. RPTPβ is expressed in cells that have been tion molecule contactin on neuronal cells leading to implicated in neuronal migration and axonal guidance, neurite outgrowth. We describe the cloning of a novel including glial precursors, radial glia and astrocytes (Rauch contactin-associated transmembrane receptor (p190 Canoll et al., 1993). RPTPβ also bears the Caspr) containing a mosaic of domains implicated in HNK-1 carbohydrate epitope that is found in several protein-protein interactions. The extracellular domain neuronal adhesion molecules and was implicated in cell of Caspr contains a neurophilin/coagulation factor recognition and axonal guidance (Rauch et al., 1991). In homology domain, a region related to fibrinogen β/γ, Drosophila, the analogous HRP carbohydrate epitope was epidermal growth factor-like repeats, neurexin motifs found in neural recognition molecules as well as in as well as unique PGY repeats found in a molluscan receptor protein tyrosine phosphatases that are expressed adhesive protein. The cytoplasmic domain of Caspr in the developing nervous system (Desai et al., 1994). It contains a proline-rich sequence capable of binding to was demonstrated recently that loss-of-function mutations a subclass of SH3 domains of signaling molecules.in Drosophila RPTPs result in erroneous pathfinding Caspr and contactin exist as a complex in rat brain of certain motor axons (Desai et al., 1996; Krueger and are bound to each other by means of lateral (cis) et al., 1996). interactions in the plasma membrane. We proposeIn our attempts to identify specific ligands of RPTPβ, that Caspr may function as a signaling component we used soluble, recombinant CAH or FNIII domains of of contactin, enabling recruitment and activation of this receptor phosphatase as specific reagents for the intracellular signaling pathways in neurons. The bindidentification of cellular proteins that bind to RPTPβ. We ing of RPTPβ to the contactin-Caspr complex could have demonstrated that the FNIII repeat binds specifically provide a mechanism for cell-cell communication to glial cells while the CAH domain of RPTPβ binds to between glial cells and neurons during development.neurons or cells of neuronal origin .

The number of clinical trials using mesenchymal stem cells (MSCs) has increased since 2008, but this trend slowed in the past several years and dropped precipitously in 2018. Previous reports have analyzed MSC clinical trials by disease, phase, cell source, country of origin, and trial initiation date, all of which can be downloaded directly from ClinicalTrials.gov. We have extended analyses to a larger group of 914 MSC trials reported through 2018. To search for potential factors that may influence the design of new trials, we extracted data on routes of administration and dosing from individual ClinicalTrials.gov records as this information cannot be downloaded directly from the database. Intravenous (IV) injection is the most common, least invasive and most reproducible method, accounting for 43% of all trials. The median dose for IV delivery is 100 million MSCs/patient/dose. Analysis of all trials using IV injection that reported positive outcomes indicated minimal effective doses (MEDs) ranging from 70 to 190 million MSCs/patient/dose in 14/16 trials with the other two trials administering much higher doses of at least 900 million cells. Doseresponse data showing differential efficacy for improved outcomes were reported in only four trials, which indicated a narrower MED range of 100-150 million MSCs/ patient with lower and higher IV doses being less effective. The results suggest that it may be critical to determine MEDs in early trials before proceeding with large clinical trials.