The future is looking brighter and brighter when it comes to stem cells and medicine. Stem cells will eventually play a pivotal role in saving lives and curing diseases, along with treating injuries and regenerating our bodies. We are in the early stages of both research and functional use in medical practice.
One of the most intriguing and exciting realms is in bioprinting, or the production of 3-D tissue/organs. Bioprinting involves growing a patient's stem cells in a growth medium in order to have them multiply, then using them to form a "bioink" made out of cell aggregates. This bioink is next placed into cartridges that are essentially syringes with long extension nozzles for printing. Specific software then drives the bioprinter to deposit the bioink cell aggregates into very precise layers. The layers are stacked one upon another and interspersed with hydrogel, a water-based substance that is used as a temporary mold to hold the structure together. The printed tissue is then allowed to grow, and as it matures the hydrogel is removed (usually within the first 24 hours so that this material does not interact with the cells). The finished tissue product can then be used in medical research or as an actual transplanted material for the patient.
Bioprinting is different from traditional tissue engineering that involves culturing cells and subsequently seeding them onto molds or scaffolds. In this more standard model, the mold is designed to look like the intended organ or tissue and is biodegradable. Once the cells mature and produce their own matrix the mold is then removed. It is the timing of the scaffold elimination that is very critical. If removed too quickly the tissue structure can fail. If it degrades too late in the process the tissue may grow into it in a manner that inhibits proper tissue growth and can lead to scarring in patients.
This technology is still in its infancy, as the ability to print tissues has been limited to more basic tissue types. Flat structures such as skin, cartilage, and muscle have been successfully engineered, while tubular structures (blood vessels, trachea, etc.) are a bit more difficult to create. Hollow, non-tubular organs are the next most difficult, such as bladder, stomach, or uterus. And finally, the more solid organs are the trickiest, including the heart, liver and kidneys. These more complex organs involve more cell types, more intricate layering of these cell types, and extensive vascular structure as well.
It is these solid organs that are truly the next frontier in the world of bioprinting. There is some debate as to whether or not we will ever be able to truly create an entire heart or kidney due to the complexity of such organs, and thus the difficulty in matching the minute details as they exist in a functioning human body. We might be able to build a similar organ that functions in the same manner but has differences, most notably in being a simpler design. Another possibility is printing smaller tissue patches that could then be used to repair or augment the body's damaged or diseased organs. An example is engineering a cardiac muscle patch that could then be transplanted to replace an area of heart muscle damaged after a myocardial infarction, or heart attack.
There will no doubt be a time when bioprinted organs take away the need for current transplant surgeries that involve risk to both the recipient and the donor, as well as the potential for rejection and need for immunosuppression.
