Proliferation of guinea pig tracheal epithelial cells in coculture with rat dorsal root ganglion neural cells.

White, Steven R., Allan Garland, Bruce Gitter, Ian Rodger, Linda E. Alger, Jonathan Necheles, April Raila Nawrocki, and Julian Solway. Proliferation of guinea pig tracheal epithelial cells in coculture with rat dorsal root ganglion neural cells. Am. J. Physiol. 268 (Lung Cell. Mol. Physiol. 12) : L957-L965, 1995.-Neuropeptides secreted by sensory afferent nerves in airways may modulate growth of airway epithelial cells. To determine whether airway sensory C-fiber nerves secrete neuropeptides that stimulate airway epithelial cell proliferation, we measured S-phase traversal in guinea pig tracheal epithelial (GPTE) cells after coculture with rat dorsal root ganglion (DRG) cells. GPTE cells were grown in subconfluent culture on collagen-coated filters for 2 days. DRG cells were harvested from newborn rat pups and grown in primary culture for 7-10 days in separate wells. GPTE and DRG cells then were cocultured for 48 h, and 10 mM bromodeoxyuridine (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 compared with 18.1 ± 7.2% in control GPTE cells (P < 0.001, n = 6). Coculture in the presence of either the neurokinin (NK) 1 receptor antagonists LY-297911 or CP-99,994, the NK 2 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 coculture 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 concentrations 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 NK 1 , NK 2 , and CGRP 1 receptor agonists in primary culture. We conclude that rat DRG cells secrete neuropeptides that stimulate GPTE cell growth in coculture and that this effect is mediated by NK 1 , NK 2 , and CGRP 1 receptors. These data suggest that airway sensory nerves may modulate epithelial cell proliferation.