Role of growth factors in oesophageal mucosal healing: A work in progress

Reflux of gastroduodenal contents into the oesophagus results in dynamic cycles of injury followed by cell proliferation and repair. These processes are receiving increased attention due to the high incidence of gastro-oesophageal reflux disease and the rising incidence of adenocarcinoma of the oesophagus. Repeated cycles of injury and repair may lead to abnormal differentiation followed by abnormal growth. This article summarizes the research performed by our group in the field of oesophageal injury and repair. We initially developed an in vivo perfused rabbit oesophagus model that served to study the effects of various components of the gastroduodenal juice on several parameters of oesophageal injury. We have shown that pepsin causes severe morphological oesophagitis at an acidic pH but is ineffective at an alkaline pH. We have also demonstrated that trypsin causes severe morphological oesophagitis at an alkaline pH but not at an acidic pH. Bile salts were found to disrupt the oesophageal barrier at both pH levels. We have also studied the effects of epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) on oesophageal regeneration. We used an ex vivo oesophageal explant model for these experiments. Both EGF and IGF-I cause a dose-dependent increase in oesophageal DNA synthesis, cell proliferation and mucosal growth. These effects are synergistic and can be inhibited by specific tyrphostins. We are currently studying the role of growth factors as therapeutic agents and the role of growth factors in the development of Barrett's oesophagus and adenocarcinoma.