A bio-engineered oesophagus has been created and trailed in mice.
The oesophagus is a part of the gastrointestinal tract that allows food to pass from our mouths to our stomachs. It is a smooth muscle structure that performs peristalsis in order to move food through its lumen. The oesophagus descends through the abdomen posteriorly to the trachea. It enters the abdominal cavity at the T10 vertebra level. The length of the oesophagus within the abdominal cavity before it enters the stomach is only 1.25cm long, it terminates at the cardia of the stomach, at the T11 vertebra level. The oesophagus consists of an internal circular and external longitudinal layer. The external layer is composed of different muscle at different thirds of the oesophagus length. The superior third of the oesophagus is voluntary straited muscle, middle third a mix of both voluntary striated and smooth muscle whereas the inferior third is purely smooth muscle. There are two sphincters in the oesophagus, the upper sphincter which lies between the pharynx and oesophagus, usually this is constricted to prevent the entrance of air into the oesophagus. The lower oesophageal sphincter is the gastro-oesophageal junction which is a physiological sphincter. It is known as a physiological sphincter as it doesn’t contain a specific sphincter muscle. The sphincter instead is formed by 4 things; the angle at which the oesophagus enters the stomach, the walls of the oesophagus in the abdominal section are compressed when there is a positive intra-abdominal pressure, there are folds in the mucosa which help aid the blockage of the lumen at the junction, the right crus of the diaphragm has a “pinch-cock” effect. The nervous innervation of the oesophagus is both from the sympathetic and parasympathetic nervous systems, which come together to form the oesophageal plexus. The parasympathetic trunks and the sympathetic fibres from the cervical and thoracic sympathetic trunks. So, the oesophagus isn’t quite as simple as first seems.
A research team have produced the bio-engineered oesophagus to aid with the treatment of both congenital and acquired oesophageal defects. Currently keeping the oesophagus continuous in patients that have oesophageal defects where tissue is lost/not present, the stomach or GI segment needs to be transported into the chest cavity. These techniques are complex and result in many serious complications.
Oesophageal atresia is a condition that’s treatment could be revolutionised by further research into this area of bioengineered oesophagus. Oesophageal atresia is a congenital defect in which the upper oesophagus isn’t connected to the lower oesophagus, blindly ending instead. This is causes by the abnormal development of the tracheoesophageal septum. TOF (trachea oesophageal fistula) can be common in this condition, where the oesophagus ends by connecting to the trachea. This condition presents immediately after birth with cyanotic attacks, foaming at the mouth and coughing. These babies cannot be fed orally due to the risk of aspirational pneumonia. Curative surgery is performed within 24hours of birth. This depends on the length of the oesophagus that is present, some babies have enough length to allow connection of the two segments of the oesophagus. Whereas others don’t and this results in a gastrostomy tube being surgical placed, this is a tube from the outside of the body going directly into the stomach to allow feed to be passed straight into the stomach, which they require for life. With this later group, this research could completely change how these babies are treated in the future and their future quality of life.
The bio-engineered oesophagus is made from a stripped rats oesophagus, removing the cells to leave a collagen scaffold. Then mice and human early stage muscle and connective tissue cells were added. A 2cm section was constructed and implanted into mice which developed into the local blood supply within a week posttransplant. The new section of oesophagus was capable of muscle contraction. Although still a long way off from being used clinically, this research is a step forward in the treatment of conditions such as oesophageal atresia or other oesophageal defects, where tissue replacement is required.
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