Thyroid transcription factor-1 expression in the human neonatal tracheoesophageal fistula

Esophageal atresia with tracheoesophageal fistula (EA/TEF) is a relatively common congenital anomaly, but its pathogenesis remains poorly understood. Previous studies using the experimental Adriamycin-induced rat model of EA/TEF suggest that the fistula tract, or "distal esophagus," is derived from respiratory epithelium and expresses the respiratory-specific transcription factor TTF-1. To better correlate the experimental rat model of EA/TEF with the human anomaly, we looked for evidence of a respiratory-derived origin in the neonatal TEF.

After IRB approval, 2 human TEF samples were removed at the time of surgery. The tissue from the fistula tract was trimmed in accordance with what the surgeons deemed to be appropriate for the preparation for a primary anastomosis. The tissues then were processed for reverse transcription polymerase chain reaction (RT-PCR), histology, and immunohistochemistry. Normal embryonic lung cDNA was used for positive controls.

Histologic examination of tissue specimens showed many epithelial tubules within loose connective tissue and a disorganized muscular coat. Thyroid transcription factor one (TTF-1) and hepatocyte nuclear factor 3beta (HNF-3beta) were shown to be present in the tissue specimen by RT-PCR and immunohistochemistry. In addition, FGF-10, a strong morphogen present in the developing lung, and FGF-1 were both present by RT-PCR. The PCR band sizes for both FGF-1 and -10 were appropriate, using human embryonic cDNA as a control, and the bands were confirmed as nongenomic by either placing the PCR primers across a known intron sequence (TTF-1) or by absence of a band in a negative RT control (HNF-3beta, FGF-10, FGF-1).

The presence of TTF-1 in the neonatal TEF shows, for the first time, that parallels may be drawn between the experimental rat model of TEF and the human anomaly at the molecular level. Moreover, these results suggest that the fistula tract in the human neonate is derived from a respiratory cell lineage. This respiratory origin of the human TEF may explain the poor esophageal motility (and subsequent serious respiratory complications) of the distal segment after standard EA/TEF repair.