Antithrombogenic property of bone marrow mesenchymal stem cells in nanofibrous vascular grafts

Craig K. Hashi, Yiqian Zhu, Guo-Yuan Yang, William L. Young, Benjamin S. Hsiao, Karin Wang, Benjamin Chu, and Song Li

PNAS  July 17, 2007  vol. 104  no. 29  11915–11920

Summary:

This study shows an effective method for producing new antithrombogenic cardiovascular grafts. The material used is  is a synthetic polymer that is to be electrospun into a cylindrical shape. These nanofibers are advantageous for cardiovascular grafts because cells can be seated very well on top. 

Looking at the picture on the left, b is the electrospun nanofibers and a,c, and d are images of actual vessels. As you can see, the natural vessels are all aligned in one direction. This is another advantage of the nanofiber grafts, they are able to be aligned similarily to resemble real live vessels. In e, mesenchymal stem cells are seated on the nanofiber and then wrapped around to form a cylindrical structure. 

In vivo studies, the researcher implanted nanofiber grafts with and without MSCs seeded on the grafts. The picture on the right shows the histology samples of the implanted grafts. The ones on the left are the grafts without any MSCs 60 days after implantation and the pictures on the right are the grafts with MSCs. It is noticable that there is much less thrombin buildup in the graft with MSCs. 

Significance:

For the longest time, the holy grail of cardiovascular bioengineering is the ability to produce artificial vessels without the buildup of thrombin along the inside walls. This is a big problem because if blood vessels become damaged, there would be no effective way to transport blood in a manner that closely resembles that of a natural body. There are numerous vascular grafts on the market right now that have a patency of roughly 50% for the next few years that it is implanted into the body. This is obviously not acceptable when the probability of survival of the graft is nothing more than a coin flip. This study made a big impact in the cardiovascular field by implanting mesenchymal stem cells onto the inside walls of nanofiber grafts and showing that these cells do have the ability to prevent thrombin buildup and vessel clogging. And on top of that, these grafts are able to be manufactured at much smaller diameters than current grafts on the market, allowing for more flexibility of vessel sizes depending on the patient.