Background/purpose: Recent work has shown that apoptosis is a key component of the normal development of the foregut. This study was designed to compare the patterns of apoptosis in the normal foregut with those in the fetus developing esophageal atresia and tracheoesophageal fistula (EA-TEF) using 3-dimensional reconstructive techniques.
Methods: Timed pregnant rats that received no treatment (control group) or received Adriamycin intraperitoneally (experimental group) had their embryos removed between days 11 and 14 of gestation. The embryos were sectioned serially and stained with H&E. Three-dimensional reconstructions were made of the foregut and areas of apoptosis were marked on them to facilitate analysis of apoptotic patterns.
Results: Apoptosis was evident in control embryos in the region in which tracheoesophageal separation occurs from days 12 and 12.5. Experimental embryos showed no apoptosis until day 13 when apoptosis was observed immediately posterior to the foregut within the esophageal mesenchyme and in the laryngeal mesenchyme ventral to the foregut.
Conclusions: The pattern, timing and location of apoptosis in rats developing EA-TEF is abnormal. Our work indicates that it is actually a complete lack of apoptosis at the crucial stage of development that leads to this abnormality rather than an alteration in the patterning of apoptosis at this crucial time. The observation of apoptosis only within the mesenchyme raises the possibility that apoptosis in the foregut developing EA-TEF may be a reaction to that abnormal development rather than its cause.