Fig. 9.

dR cells produce potent paracrine promitogenic activity. The potential of different PA wall cells (dS-SMC, dR cells, or fibroblasts) to secrete promitogenic factors was tested by assessing nuclear BrdU incorporation in the coculture experiment using the “source” cells [those from which conditioned medium (CM) was tested] and the “target” cells (those exposed to CM from the source cells and in which BrdU incorporation was evaluated; see methods). After 24 h, serum-free medium conditioned by the dR cells (hatched bars) exhibited the highest promitogenic effect on dS-SMC and adventitial fibroblasts (adv. Fibs) compared with CM from other cell types tested (dS, gray bars; Fib, open bars). Hypoxia (3% O₂, Hyp, closed bars) further augmented this effect [P < 0.05 compared with normoxia (Nor)]. ***P < 0.001, **P < 0.01, *P < 0.05 compared with the effect of Fib-CM or dS-CM.