NUMBER OF ADRENERGIC AND ISLET-1 IMMUNOREACTIVE CELLS IS INCREASED INAVIAN TRUNK NEURAL CREST CULTURES IN THE PRESENCE OF HUMAN RECOMBINANT OSTEOGENIC PROTEIN-1

OP-1, also known as BMP-7, is a member of the TGF-beta superfamily of proteins and was originally identified on the basis of its ability to induce new bone formation in vivo. OP-1 mRNA is found in the developin g kidney and adrenal gland as well as in some brain regions (Ozkaynak et al. [1991] Biochem. Biophys. Res. Commun. 179:116-123). We have tes ted the effect of recombinant human OP-1 on quail trunk neural crest c ultures. The number of catecholamine-positive cells which developed af ter 7 days in vitro in the presence of OP-1 was increased in a dose-de pendent manner, with a greater than 100-fold maximal stimulation obser ved. The increase in the number of catecholamine-positive cells in the presence of OP-1 was paralleled by an increase in the number of tyros ine hydroxylase (TH)-positive cells. In contrast, total and melanocyte cell number were unaffected by the presence of OP-1. The number of Is let-1-immunoreactive cells was also increased by OP-1, but to only abo ut half the value seen for TH. Double label experiments revealed these Islet-1-positive cells were a subset of the TH-positive cells. Inhibi tors of DNA synthesis prevented the OP-1-mediated increase in adrenerg ic cell number, indicating that OP-1 does not act on a postmitotic cel l population. However, labeling studies with bromodeoxyuridine indicat ed that OP-1 did not increase the proportion of the cell population en gaged in DNA synthesis. Thus, the OP-1-mediated increase in adrenergic cell number most likely occurs as a result of the enhanced survival o f a subpopulation of adrenergic precursors or an increase in their pro bability of adrenergic differentiation, but not by increasing the mito tic rate of adrenergic precursors or adrenergic cells themselves. In c ontrast to OP-1, TGF-beta 1 decreased adrenergic cell number. When OP- 1 and TGF-beta 1 were added simultaneously, TGF-beta 1 antagonized the OP-1-mediated increase in adrenergic cell number in a dose-dependent manner. (C) 1995 Wiiey-Liss, Inc.