Pathohistological study of adriamycin-induced tracheal agenesis in the fetal rat

There have been few studies of tracheal agenesis (TA) because it is an extr emely rare condition and is invariably fatal. However, it is recognised to be associated with a variety of oesophageal abnormalities, including oesoph ageal atresia (OA) and communicating bronchopulmonary foregut malformations (CBPFM). Except for some gross pathological reports, there has been no det ailed histological investigation of this congenital abnormality. Adriamycin -induced TA in fetal rats provides a means of studying this uncommon condit ion, including its relationship to oesophageal abnormalities. TA was induce d in rat features by intraperitoneal injection of adriamycin (2 mg/kg) into timed-pregnant rats on days 6-9. Their 33 fetuses were removed by caesarea n section, cut transversely, and stained after which the slides were examin ed. OA developed in 27/33 adriamycin-treated fetuses, TA occurred in 5. Fou r had type III while the 5th had type II TA. The oesophagus of fetuses with TA acquired tracheal features in the region where both ectopic bronchi ori ginated. Two fetuses with TA also had OA, and 4 had a CBPFM. Other abnormal ities detected involved the gastrointestinal, urinary and cardiovascular sy stems. The association of TA and oesophageal abnormalities suggests that th ere may be a spectrum of abnormalities comprising a number of variants, whi ch may have a common aetiology. The other abnormalities co-existing in this animal model mirror those found in reported cases of human TA. Ultimately, the rat model of OA and TA may give insight into the embryogenesis of thes e malformations.