Abstract
With a limited supply of organ donors and available organs for transplantation, the aim of tissue engineering with three-dimensional (3D) bioprinting technology is to construct fully functional and viable tissue and organ replacements for various clinical applications. 3D bioprinting allows for the customization of complex tissue architecture with numerous combinations of materials and printing methods to build different tissue types, and eventually fully functional replacement organs. The main challenge of maintaining 3D printed tissue viability is the inclusion of complex vascular networks for nutrient transport and waste disposal. Rapid development and discoveries in recent years have taken huge strides toward perfecting the incorporation of vascular networks in 3D printed tissue and organs. In this review, we will discuss the latest advancements in fabricating vascularized tissue and organs including novel strategies and materials, and their applications. Our discussion will begin with the exploration of printing vasculature, progress through the current statuses of bioprinting tissue/organoids from bone to muscles to organs, and conclude with relevant applications for in vitro models and drug testing. We will also explore and discuss the current limitations of vascularized tissue engineering and some of the promising future directions this technology may bring.
Highlights
Are organ donors a limited resource, the functional efficacy of donated organs as well as risk of disease and/or infection from deceased individuals greatly limit the number of available tissues for transplantation (Neuberger and Callaghan, 2020; Shah et al, 2020)
human umbilical vein endothelial cells (HUVECs) with human mesenchymal stem cell laden hydrogels printed in osten-like patterns in vitro induced a significant expression of angiogenic markers and an increase in blood vessel per tissue volume density (Figure 6C; Piard et al, 2019). These results demonstrate that proper scaffold design and cell placement during 3D bioprinting is essential for neovascularization (Piard et al, 2019)
The incorporation of vascular networks in engineered tissue constructs, while maintaining tissue integrity, remains a challenge that needs to be addressed before any human implantation applications can happen (Lovett et al, 2009; Sarker et al, 2018). 3D bioprinting offers promising advancements in this field of research by offering its ability to construct complex multi-material tissue architecture with a high degree of resolution
Summary
Are organ donors a limited resource, the functional efficacy of donated organs as well as risk of disease and/or infection (a prominent issue during the COVID-19 pandemic) from deceased individuals greatly limit the number of available tissues for transplantation (Neuberger and Callaghan, 2020; Shah et al, 2020). This section will be followed by an examination of some of the exciting current advances in the most researched areas of bioprinting: bone, muscle, cardiac, liver, and skin and discuss attempts to implant these engineered tissues in vivo. We have chosen this order so that we begin with the vasculature and move our discussion of recent attempts to make bone replacements and the need for vascular conduits to provide nutrients and to remove waste from the printed bones. A prolonged culture period (8 weeks) is still something to be improved upon to allow for urgent use in trauma situations. Luo et al (2020) has recently successfully demonstrated the use of Induced pluripotent stem cells (ihPSC) for TEVG using a PGA scaffold
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