Investigations launched into artificial tracheas

Karolinska Univ. Hospital via Scanpix/Corbis/Reuters

Surgeon Paolo Macchiarini carrying out the first transplant of a bioengineered synthetic trachea in 2011.

One of Europes most prestigious medical universities, the Karolinska Institute in Stockholm, has launched two investigations into the clinical procedures of a doctor famed for performing potentially revolutionary, bioengineered trachea transplants.

Since 2008, Paolo Macchiarini, a thoracic surgeon at the Karolinska Institute, has replaced parts of airways damaged by injury, cancer or other disorders in 17 patients. In the earlier cases, he transplanted parts of tracheas taken from cadavers; in his later work, he transplanted synthetic tracheas. In both procedures, before transplantation, he would treat the tracheas with stem cells taken from the patients bone marrow, which he says helps the transplants to act like biological tissue.

Bioengineering experts contacted by Nature say that Macchiarinis procedures were considered a great leap for their nascent field because tracheas demand a high level of biological function including the ability to defend against the constant assault of inhaled bacteria and to form a seal with the adjoining airway tissue.

Macchiarinis reports were a bright spot for the field, says David Mooney, a bioengineering specialist at Harvard University in Cambridge, Massachusetts.

One of the investigations is being conducted by an external expert in the relevant fields, who is due to report the findings on 15 January. It focuses on the three procedures that Macchiarini carried out at the Karolinska Institute, all of which involve artificial tracheas.

The investigation comes in response to a report filed in August by four thoracic doctors at the affiliated Karolinska Hospital Matthias Corbascio, Thomas Fux, Karl-Henrik Grinnemo and Oscar Simonson who helped to treat the three patients.

The doctors compared results in a paper Macchiarini published in The Lancet (Lancet 378,19972004; 2011), describing the first use of a synthetic trachea seeded with stem cells, with the medical records of the patient. According to the doctors, there are discrepancies.

For example, the Lancet paper says that the synthetic trachea was partly covered by nearly healthy epithelium, indicating the growth of a protective cell layer, whereas the doctors say they could find no evidence in biopsy reports for healthy growth. The paper also says that the implanted trachea showed signs of tight connection with the adjacent tissue and that it was acting like an almost normal airway, whereas bronchoscopy reports note gaps between the trachea and the bronchus, the tube that leads from the trachea to the lungs, and the need for stents to stabilize the airway.

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Investigations launched into artificial tracheas