Fabrication of Pulsatile Cardiac Tissue Grafts Using a Novel 3-Dimensional Cell Sheet Manipulation Technique and Temperature-Responsive Culture Surfac
Tatsuya Shimizu, Masayuki Yamato, Yuki Isoi, Takumitsu Akutsu, Takeshi Setomaru, Kazuhiko Abe, Akihiko Kikuchi, Mitsuo Umezu, Teruo Okano
This paper discusses a new method utilized to fabricate pulsatile cardiac grafts that layers cell sheets 3-dimensionally. By applying poly(N-isopropylacrylamide) (PIPAAm), a temperature-responsive polymer, confluent cells will detach as a cell sheet easily by reducing temperature, forgoing any need for enzymatic treatments. The experiment applied this technique on neonatal rat cardiomyocyte sheets in order to construct cardiac grafts. After overlaying 4 layers, the sheets were observed macroscopically to pulse spontaneously. These grafts were then transplanted into subcutaneous tissue of nude rats in vivo, as well as into 3-week-old and 8-week-old rats. The long-term survival of these grafts was confirmed for up to 12 weeks.
Their results showed that when culture temperature was decreased from 37°C to 20°C, the cardiomyocytes detached as a contiguous cell sheet within an hour without any residual cells remaining on the surface. Electrical communication between the layered cell sheets was monitored on TCPS dishes. Beating of the layered cell sheets initially stopped but began to pulsate spontaneously and simultaneously within one week after layering. Surface electrograms were also used to monitor the cardiac grafts after transplantation into the nude rats. However, these showed that the Graft beating rates varied from 13 to 96 bpm and were relatively slow in comparison with host hearts (332±27 bpm, n=5). Transplantation sites were opened 3 weeks after transplantation to examine the functional effectiveness of the grafts. Their analysis showed that the fractional shortening of the grafts increased depending on the number of layers of the cell graft.
3 comments:
What other flat tissues could be made using these kinds of substrates?
Very cool! I wish we had something like PIPAAm-grafted dishes when we culturing the Rex cells for lab! On the other hand, what are the advantages of this technique over bioprinting cell layers? (I've heard that there's been success in printing pulsatile myocardial cell layers with modified inkjet printers. Like the technique described in this paper, bioprinting also bypasses the need for a biodegradable scaffold, as the cells could be directly printed onto collagen membranes.) Layering the cell-sheets sequentially as described in the paper seems really tricky, whereas bioprinting can be automated. Would the PIPAAm method at least be more cost-effective or ensure higher cell viability?
Figuring out how to construct artificial grafts is often the hardest part of the process, because the slightest error in construction will lead to a nonfunctional organ. These PIPAAm based self-layering grafts seem to be a promising way to achieve highly sensitive control of the graft construction process.
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