Extracellular matrix proteins increase the expression of pro-TRH and pro-protein convertase PC1 in fetal hypothalamic neurons in vitro

External clues for neuron development include extracellular matrix (ECM) mo lecules. To explore ECM influence on the early development of peptide pheno type in the CNS, we have compared pro-TRH levels in primary cultures of rat hypothalamic cells plated either on poly-lysine (PL) (control) or on PL pl us one of various ECM molecules at 10 mu g/ml. Fetal day 17 cells plated at a density of 1250/mm(2) were grown in a serum free medium made of Neurobas al medium supplemented with B27 (GIBCO). Cultures, consisting mainly of neu rons, were analyzed at DIV 2. ECM proteins induced morphological effects in agreement with previously published studies. The amount of pro-TRH per dis h, quantified by Western blotting, was increased to 275% for laminin, 191% for fibronectin and 173% for tenascin-C (control = 100%); there was no effe ct of vitronectin. Laminin or fibronectin did not change pro-TRH mRNA or TR H levels but enhanced levels of the pro-protein convertase PCI suggesting t hat the ECM molecules did regulate the translational status of pro-TRH. In conclusion we have shown that some ECM proteins increased pro-TRH level in vitro; this may contribute to the enhancement of pro-TRH levels observed ea rly in vivo in the hypothalamus. (C) 2000 Elsevier Science B.V. All rights reserved.