Recent advances in the fabrication of vascularized tissues and blood vessels: A state-of-the-art review

The creation of physiologic flow-friendly tissues for organs and systems and the integration of vascular systems into constructs, such as tissues, represent an important factor for the engineering of functional substitutes that require self-supporting cell scaffolds within biologically relevant geometries. This is crucial if the target organ substitute surpasses 400 μm in any dimension. This review provides a detailed description of the latest developments and persistent issues in this area, focusing on the incorporation of vascular systems into engineered tissues and their capability to sustain large-scale constructs. One of the key contributions of this review is the in-depth explanations of the two advanced techniques utilized in the fabrication of vascular networks through three-dimensional bioprinting, electrospinning, and microfluidic technologies, which markedly altered the approach to and fabrication of vascular structures. By critiquing these techniques from the standpoint of fluid dynamics, the mechanical properties of bioink, and cell biology, the article demonstrates the progress toward the realization of more sophisticated, perfusable networks which imitate the natural blood vessels. Furthermore, this review article has analyzed the persistent problem of integrating the vascular part with the host circulatory system, which is critical for adequate perfusion in engineered tissues. The review provides a thorough analysis of anastomosis, the intricate process by which engineered vessels connect to native vasculature and discusses the biological and physical challenges that impede its success. In addition, the review analyzes the different vascular bioengineering materials with particular emphasis on bioinks that are capable of reproducing the mechanical properties of the actual tissues to improve the biological functions of the cells, which is very important for the engineered large tissue constructs where passive diffusion is insufficient. The novel value of this study is in the investigation of applications involving stem cells, specifically induced pluripotent stem cells and autologous stem cells, for producing endothelial and smooth muscle cells. Furthermore, gene-editing technologies have the potential for tailoring such vascular networks to react to physiological conditions. This review concludes by tabulating the new avenues of future research that encompass design of immunomodulatory biomaterials, dynamic vascular networks, and improved preclinical models that better reflect human physiology. This review gives a useful insight into the future direction of vascular tissue engineering.