PROLIFERATION OF GUINEA-PIG TRACHEAL EPITHELIAL-CELLS IN COCULTURE WITH RAT DORSAL-ROOT GANGLION NEURAL CELLS

Neuropeptides secreted by sensory afferent nerves in airways may modul ate growth of airway epithelial cells. To determine whether airway sen sory C-fiber nerves secrete neuropeptides that stimulate airway epithe lial cell proliferation, we measured S-phase traversal in guinea pig t racheal epithelial (GPTE) cells after coculture with rat dorsal root g anglion (DRG) cells. GPTE cells were grown in subconfluent culture on collagen-coated filters for 2 days. DRG cells were harvested from newb orn rat pups and grown in primary culture for 7-10 days in separate we lls. GPTE and DRG cells then were cocultured for 48 h, and 10 mM bromo de-oxyuridine (BrdU), a thymidine analogue, was added in the final 24 h. Control GPTE cells were grown under similar conditions but without DRG cells. Coculture with DRG cells stimulated GPTE cell traversal of S phase. BrdU labeling in cocultured GPTE cells was 42.8 +/- 5.8 compa red with 18.1 +/- 7.2% in control GPTE cells CP < 0.001, n = 6). Cocul ture in the presence of either the neurokinin (NK)(1) receptor antagon ists LY-297911 or CP-99,994, the NK2 receptor antagonist SR-48,968, or the calcitonin gene-related peptide (CGRP) receptor antagonist hCGRP- (8-37) (10(-7) M of each) during coculture attenuated proliferation of GPTE cells. Treatment with all three antagonists together during cocu lture decreased BrdU labeling to 2.4 +/- 0.9% of labeled cells vs. 8.5 +/- 0.5% of labeled cells during coculture without antagonists (n = 4 , P < 0.02). DRG cells in coculture secreted substantial concentration s of CGRP [71.0 +/- 11.3 (+/- SE) pmol/ml], substance P (1.26 +/- 0.35 pmol/ml), and neurokinin A (0.45 +/- 0.10 pmol/ml) (n = 19 for each). Proliferation was stimulated in GPTE cells by treatment with NK1, NK2 , and CGRP(1) receptor agonists in primary culture. We conclude that r at DRG cells secrete neuropeptides that stimulate GPTE cell growth in coculture and that this effect is mediated by NK1, NK2, and CGRP(1) re ceptors. These data suggest that airway sensory nerves may modulate ep ithelial cell proliferation.