The presence of growth factors in the middle ear fluid was examined du
ring lipopolysaccharide-induced otitis media (OM) in the chinchilla. T
here was a progressive significant increase in the proliferative activ
ity detected in the LPS-free MEF by five days in culture. We conclude
that Ips indirectly mediates hyperproliferative changes in the middle
ear during OM by inducing growth factors.