3D Bioprinting using Stem Cells

Three-dimensional (3D) bioprinting is a new technology used to create biological constructs, widening the scope of regenerative and therapeutic medicine. Stem cells are self-renewing, remain undifferentiated unless stimulated and have the capability to differentiate into all specialized cell
types. These characteristics make stem cells ideal for use in the production of 3D printed constructs. A biological construct is composed of cells in a scaffold that is compatible, biomimics and can integrate in vivo. Biological structures generated using 3D bioprinting have the potential to alleviate
the need for donor tissue and organs for transplantation. Additionally,these constructs also provide a better way to model disease and test pharmaceuticals.

Regenerative medicine offers even more promises than artificial limbs and body parts. What if instead of having a robotic arm, you could regrow completely your original arm ? Sounds impossible ? It isn’t. Lizard regrow their tails. Axolotls regrow severed legs. We now understand how they do it: stem cells. These pluripotent undifferentiated cells have the power to repair any body part. Using organ culture, stem cells can regrow any organ as fresh as new through. In the future it will be possible to regrow limbs or organs directly on a person, as if the body was simply healing itself.

Recent advances have allowed for three-dimensional (3D) printing technologies to be applied to biocompatible materials, cells and supporting components, creating a field of 3D bioprinting that holds great promise for artificial organ printing and regenerative medicine. At the same time, stem cells, such as human induced pluripotent stem cells, have driven a paradigm shift in tissue regeneration and the modeling of human disease, and represent an unlimited cell source for tissue regeneration and the study of human disease. The ability to reprogram patient-specific cells holds the promise of an enhanced understanding of disease mechanisms and phenotypic variability. 3D bioprinting has been successfully performed using multiple stem cell types of different lineages and potency. The type of 3D bioprinting employed ranged from microextrusion bioprinting, inkjet bioprinting, laser-assisted bioprinting, to newer technologies such as scaffold-free spheroid-based bioprinting. This review discusses the current advances, applications, limitations and future of 3D bioprinting using stem cells, by organ systems.

Bioprinting is a quickly progressing technology, which holds the potential to generate replacement tissues and organs. Stem cells offer several advantages over differentiated cells for use as starting materials, including the potential for autologous tissue and differentiation into multiple cell lines. The three most commonly used stem cells are embryonic, induced pluripotent, and adult stem cells. Cells are combined with various natural and synthetic materials to form bioinks, which are used to fabricate scaffold-based or scaffold-free constructs. Computer aided design technology is combined with various bioprinting modalities including droplet-, extrusion-, or laser-based bioprinting to create tissue constructs. Each bioink and modality has its own advantages and disadvantages. Various materials and techniques are combined to maximize the benefits. Researchers have been successful in bioprinting cartilage, bone, cardiac, nervous, liver, and vascular tissues. However, a major limitation to clinical translation is building large-scale vascularized constructs. Many challenges must be overcome before this technology is used routinely in a clinical setting.