Antithrombogenic Property of Bone Marrow Mesenchymal Stem Cells in Nanofibrous Vascular Grafts
http://www.pnas.org/cgi/content/full/104/29/11915?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=craig+hashi&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
Craig K. Hashi†, Yiqian Zhu‡, Guo-Yuan Yang‡, William L. Young‡, Benjamin S. Hsiao§, Karin Wang§, Benjamin Chu§,
and Song Li†¶
Nanostructured biomaterial is the main focus not only in this article but also in the field of tissue engineering. First, electrospinning is used to produce such nanofibrous scaffolds made of synthetic polymers, such as poly-L-lactic acid, which are biocompatible, biodegradable, and have configurable mechanical properties. In fact, the use of electrospinning allows the structure and morphology of electrospun scaffolds to be manipulated to resemble ECM, including porosity that allows homing and penetration of cells into the membranes for tissue regeneration. Afterwards, mesenchymal stem cells (MSC) were seeded on the nanofibrous membrane, and the graft was implanted into the common carotid artery of rats via bypass procedure. Sixty days after implantation, the remodeling of vascular grafts was examined in vivo, showing that acellular grafts had significant intimal thickening and inward remodeling in the lumen compared to the MSC-seeded grafts that showed little intimal thickening. This suggests that nanofibrous scaffold alone could not remain patent in the long run, but with MSCs, inflammatory responses induced by the scaffolds could be blocked. Furthermore, cross-sections of the vascular grafts were stained for CD31 and MHC to locate endothelial cells (EC) and smooth muscle cells (SMC), respectively, as well as for collagen and elastin. The well-organized EC and SMC distribution in and the formation of an elastic lamina layer adjacent to the lumen of MSC-seeded grafts represented that in native arteries, insinuating that cellular nanofibrous scaffolds allowed self-assembly and remodeling in vivo and that long-term patency of such vascular grafts could be achieved.
To determine the antithrombogenic property of MSCs in vivo and antiplatelet adhesion property in vitro, short-term experiments were performed to examine the lumen of acellular and cellular grafts. SEM and cross-sectional staining showed that acellular grafts had significant amounts of platelet aggregation and presence of thrombus formation on luminal surface, whereas MSC-seeded grafts exhibited very little platelet aggregation and very minimal thrombus formation on luminal surfaces. In addition, another experiment was done to reveal that heparin sulfate proteoglycans on the MSC surface plays an essential role in resisting platelet adhesion and aggregation. These results suggest that the long-term patency of MSC-seeded grafts was primarily due to the antithrombogenic property and antiplatelet adhesion property of MSCs.
The use of combining artificial nanofibrous vascular grafts and bone marrow mesenchymal stem cells is essential in the field of tissue engineering, especially in treating cardiovascular diseases since cardiovascular disease is the number one killer in the
5 comments:
Has this technology been used in human patients yet? Are there any disadvantages to using marrow mesenchymal stem cells in nanofibrous vascular grafts?
Did the paper talk about clinical practicality? For example is it always feasible time-wise for the patient to use autologous cells since it takes a while to culture the cells and implant them in the scaffold?
Although the acellular scaffold is not as effective, it seems it would be a suitable place-hold until MSC's could be injected into the scaffold to promote healing and integration.
As of now, these vascular grafts have not been used clinically in human patients. However, they are still being tested in rats and sheep, especially long term effects (more than three months), for occlusions. As for practicality, mesenchymal stem cells are obtained from Cambrex and cultured to establish the cell line, allowing for proliferation without differentiation. However, it is still possible that, without proper care, the stem cells may differentiate and lose their antithrombogenic property.
In addition, the acellular scaffold may be used as a suitable place-hold, but it is not necessary to utilize it initially given that there are MSC's available for seeding. If acellular scaffold is implanted, thrombosis is inevitable in a short period of time, and it would just be like the original, clogged artery.
I know for a fact that heparin in the body has a negative charged end which helps to resist protein adhesion. However, given that the cells are implanted into the blood environment, where they are not native too, I’m wondering if the calcification was observed in the device. In blood, there are more than just proteins that can problems for a patient. Given that Ca ++ ions are present, too, checking for calcification is one routine check for biological performance. How was, if at all, was addressed in the research?
With respect to immune responses to foreign cells and the time needed to culture MSCs, I wonder if other methods of obtaining this antithrombogenic property have been considered, perhaps via coatings on PLLA to recruit autologous MSC to the scaffolds.
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