Fabrication of cell microintegrated blood vessel constructs through electrohydrodynamic atomization
John J. Stankus, Lorenzo Soletti, Kazuro Fujimoto, Yi Hong, David A. Vorp, William R. Wagner
I know there have been a couple articles done on electrospun scaffolds, but I found an interesting paper on overcoming cellular seeding problems using an electrospray method. This paper uses electrospun biodegradable poly(ester urethane) urea (PEUU) to mimic the mechanical and architectural environment of native ECV found in blood vessels. The study uses microintegration (or electrohydrodynamic atomization), where cells are electrosprayed while the tubular conduits are being electrospun simultaneously around the cells. This insures that cells are numerous and of equal density throughout the whole construct. Compared to methods that require cell seeding and migration, this method offers full control of cell density. Tubular conduits and vascular SMCs were used (more specific to blood vessel TE). The construct was then cultured and the cellular viability, morphology, count etc. along with mechanical properties were measured.
The paper goes on to describe the synthesis of PEUU as it is a novel polymer that was developed by this lab for the purposes of the electrohydrodynamic atomization. Both the PEUU and SCMs are charged and sprayed through separate nozzles that sit perpendicular to each other to form 8cm conduits which were then cultured in serum for a full day before being removed from the apparatus and sectioned for further culturing (3 days) on TCPS plates or in spinner flasks.
SCM growth and viability was characterized using a MTT mitochondrial activity assay. Both the TCPS plates and spinner flasks showed SMC growth, with spinner flasks showing higher proliferation. The samples were then stained with H&E and analyzed using our friend ImageJ. After four days, cells had normal morphology and began to show signs of cellular spreading.
After 4 days, the biomechanical properties were also characterized. These included: static/dynamic compliances, burst pressure, stiffness index, and suture retention. They were able to model these properties, and these equations can be found in the paper if you’re really interested. In short, the constructs were able to take and average of 1750 mm Hg of pressure (compare to normal blood pressure in hundreds of mm Hg). Stress-stretch responses were all strong, and suture retention forces also seemed to increase with days in culture.
This paper was able to develop a process that has potential for future tissue engineered blood vessel production. Highly cellular tubular conduits were produced using a new microintegration technique that showed high cellularity and strong mechanical properties. SMCs were able to microintegrate into the conduits and proliferate very well. The construct itself was mechanically sound, was suturable, and retained their lumens after compression. The paper also found that constructs cultured on spinner flasks were more promising for TE of blood vessels, but that a non-thrombogenic luminal surface was needed first (for example: luminal seeding).
4 comments:
So this technique seems to do very well as a solution to engineering blood vessels due to its mechanical properties, but what did the paper mention anything about the time factor? It appears that after a certain period of time has passed, the scaffold itself may undergo some sort of degradation and thus the required mechanical properties will be lost.
I agree with Concord's point about time and further tests need to be done long-term to test out this device. Did the paper mention what materials that the scaffolds can be made out with the spinner flask method? Why does the spinner flask method make constructs more suitable for TE blood vessels?
You mention that there is good cellularity and cell spreading. However, did the spraying technique have any effect on the initial viability of cells? It seems that this is a possibility as cell morphology was not normal and cellular spreading was not apparent until four days post-spraying/ sectioning. Also, were there any fatigue tests performed? In the long run, many loading cycles through the scaffold could potentially cause it to yield`and fail.
Is when the PEUU degrades a factor in maintaining the scaffold? How do they know when it will degrade and whether it will still give the same mechanical properties that they tested for, once the PEUU degrades?
Also, did the mechanical properties depend on the diameter of the scaffold? In other words, was there a limit on how big they could make the scaffolds?
I agree with the previous comments that more information on how suitable the product of this method would work in the long run. Maybe electrohydrodynamic atomization can be combined with other scaffold-making techniques, like making multi-layered blood vessels with different cell types.
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