Expression of molecular markers for bone formation increases during experimental acute otitis media

Bony tissues are integral parts of the function of the middle ear and the p rotection of adjacent vital structures. To explore the reaction of middle e ar bone to acute otitis media, rats were challenged with Streptococcus pneu moniae and Haemophilus influenzae. Local changes were monitored for up to 1 month. After reverse transcription, competitive polymerase chain reaction was used to determine the expression levels of two molecular markers of bon e formation, osteocalcin and procollagen I, and the two cytokines interleuk in (IL)-6 and tumor necrosis factor (TNF)-alpha, in the bone. Middle ear bo ne responded rapidly to bacterial challenge, and the reaction depended upon the causative agent. On day 1, IL-6 and TNF-alpha transcripts were detecte d in the bone from all middle ears. After a short period of decreased expre ssion of osteocalcin, during which the otitis diagnosis could not be made c linically, the levels of bone formation markers increased dramatically. The maximum levels of these markers were reached on days 6 and 14 for animals challenged with H. influenzae and pneumococci, respectively. Infections ind uced by pneumococci had a longer duration, and after the initial phase the production of osteocalcin and procollagen transcript were significantly hig her in the pneumococcus-infected animals. The results indicate that even in an uncomplicated infection, the bone of the bulla reacts to an acute otiti s media with a short period of inhibited osteoblast activity followed by a longer period of new bone formation. (C) 2001 Academic Press.