Using Nature as Scaffolds for Printed and Regenerated Human Tissue
The veins through plants, like this spinach leaf, bear a striking resemblance to the blood vessels in human tissues. Image Source: Flickr User: Stewart
In recent years, you’ve probably heard the buzz about printing and regenerating tissues and organs in the lab. Unfortunately, this work has hit a plateau, mainly because technology for vascularizing organs is lagging behind the technology employed to regenerate the tissues themselves. Without this crucial second piece of the puzzle, the process can’t be utilized widely or effectively.
Researchers tried decellularizing a pig heart and introducing autologous stem cells to repopulate the structure. But it turns out, the supply of pig hearts is woefully insufficient. This technique also poses many ethical questions. Plants, on the other hand, are abundant and host a similar-looking vascular structure to that found within human tissue and organs. Researchers recently decellularized a spinach leaf to grow cardiac tissue.1 As they continue to explore cellular growth methods with innovative lab software, an implantable heart with a spinach backbone may become a reality.
Assessing the Plateau
Losing a vital organ necessitates a lifelong reliance on assistive devices unless you’re the fortunate recipient of an organ transplant. And then, even if you can find a donor, your body may still choose to reject the transplant. Scientists have been exploring alternatives to a classical transplant scenario in hopes of circumventing these common issues.
By implanting the body with autologous tissues or organs rejection rates are drastically reduced and, theoretically, organs may be made to order. To this end, researchers have developed the methods to grow or print numerous organs and mini organs over the past five years.2
Scientists have bioengineered ear replacements that are an infinitely better fit than previous equivalents. By scanning the patient’s existing ear, scientists used innovative lab software to create a 3D rendering of the intact ear. Thereafter, an ear shaped mold was printed and filled with a gel composed of cow ear cells and collagen. After setting for two days, an “ear” pops out that is ready to be populated by your cells.3
Scientists struggled to establish oviduct-like conditions in the lab to research diseases that affect fallopian tubes, but there is a newly established method to grow the epithelial layer of the fallopian tubes. Small, hollow, fallopian-like spheres self-initiate from stem cells under certain environmental conditions. Using innovative lab software, it may be possible to move these from the petri-dish to clinical applications, restoring fertility in women with fallopian tube diseases.4
There have been a number of attempts at mini-kidneys, but recent efforts paid off. The new mini-kidney contains all key cell-types and is grown in a manner that mimics fetal development. This fully-fledged, albeit tiny organ will be used for drug development, disease progression modelling and cell therapy research. With the help of modern lab software, there is the possibility to assess the potential to scale its size for implantation. This will be particularly useful for those undergoing dialysis while waiting for their turn for a transplant.5
This progress is awe-inspiring. However, for these organoids to continue to grow, adequate oxygen, nutrients and growth factors must be present throughout the tissue, and that’s where plant life comes to the rescue.
Overcoming Vasculature Challenges
Tissues throughout the body are not homogenous structures. Blood vessels are woven throughout epithelial tissue and muscle. This vasculature is crucial for the transport of essential molecules but is small and challenging to reproduce in a lab setting. Haphazard induction of angiogenesis may induce tumorigenesis and 3D printing is not precise enough to print capillaries, at least not yet. As mentioned above, full-size organs tend to use a scaffold or template.
Occasionally, an animal organ can be used, but this approach poses many ethical issues. In certain cases, like when human reproductive organs must be generated, a human scaffold is required. This presents a recurrent issue, the donor-base is limited. So researchers sought out a better, organic option. Leaves contain a branched vascular structure that bears a striking resemblance to many human tissues. Researchers decellularized a spinach leaf via a modified detergent perfusion technique. Modifying techniques associated with one species may first be modelled using innovative lab software to ease the transition from one model organism to another. Although the underlying structure may be quite similar, the overlaid tissues are vastly different between plants and vertebrate.
The remaining cellulose structure was assessed to ensure it maintained its transport capacity. After ensuring that the vasculature was sound, human endothelial cells were applied followed by mesenchymal stem cells and pluripotent stem cells derived from cardiomyocytes. Over 21 days, the heart cells demonstrated contractile function. Functional cardiac tissue had finally been grown using plant vasculature as a model. The next step for researchers will involve complex computer models to earnestly assess and design the transition from bench to bedside.
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- “Crossing kingdoms: Using decellularized plants as perfusable tissue engineering scaffolds,” May 2017, http://www.sciencedirect.com/science/article/pii/S0142961217300856 ↩
- “11 Body Parts Grown in the Lab,” January 26, 2016, http://www.livescience.com/53470-11-lab-grown-body-parts.html ↩
- 3D-Printed Ear Created in Lab,” February 20, 2013, http://www.livescience.com/27280-3d-printed-ear-created.html ↩
- “Fallopian tubes grown in a Petri dish,” January 11, 2016, https://www.mpg.de/9814344/fallopian-tubes-organoids ↩
- “Scientists grow mini-kidney in lab,” October 14, 2015, https://www.uq.edu.au/news/article/2015/10/scientists-grow-mini-kidney-lab ↩