Stem cells were used
successfully in a 10 year old girl in Sweden to bioengineer vein for
bypass of a blockagein one of the large liver veins (portal vein).
A blockage of portal vein can happen due to various reasons in some children and can lead to portal hypertension and bleeding from the upper gastrointestinal tract, and enlargement of spleen. Upper gastrointestinal bleeding may not manifest any symptoms but still lead to death and disability. In children, this illness may result in repeated hospitalization, absence from school and emotional difficulties. Treatment options include bypass surgery that bypasses the blocked area (to re-establish the blood flow) and normally this means connecting the superior mesenteric and left intrahepatic portal veins using a vein graft.
A deceased or cadaver donor vein graft or a liver transplant would mean life-long anti-rejection drugs and were options that were not considered.
In this new procedure, the research team bio-engineered a vein for the girl using the following technique -
Initially, a 9-cm vein section or graft was obtained from a 30-year old organ donor and the cells from the vein were removed using buffer and enzyme solutions over a period of 12 days.
The vein graft was then treated with antibiotics and a sample piece was tested for the occurrence of nuclei and HLA antigens.
Next, endothelial and smooth muscle cells were prepared from the girl's bone marrow and placed in the vein graft for giving it a new layer of cells that would not work as antigens.
After 2 weeks, endothelial and smooth muscle cells were found in the lumen and walls of the vein graft tissue respectively.
Once the vein was ready, it was used to overcome the blockage by a surgical procedure.
A close follow up was done to see if the graft functioned or if it got re-stenosed. This was done using computerized angiography. To prevent the graft getting clotted, daily aspirin (75 mg) was used for 6 months post-surgery.
The bypass graft instantly provided the patient an efficient blood supply of 25-30 cm/s in the portal vein and 40 mL/s in the artery. Following a revised procedure a year later, the portal blood flow resulted in significant improvement in the patient's physical and mental development and ability. One year after surgery, the patient had a 6 cm height (137 cm to 143 cm) and 5 kg weight increase (30 kg to 35 kg). Though no mental cognition assessment was conducted, the patient's parents described improvement in physical activity (2-3 km walks, simple gymnastics), speech and focus in school.
This study has given encouraging initial results and shown how stem cells may be used in future for bioengineering vein grafts and provides hope to patients especially in difficult situations as it was in this 10-year old girl.
Reference: Transplantation of an allogeneic vein bioengineered with autologous stem cells: a proof-of-concept study; Michael Olausson et al; The Lancet 2012