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.

Millions of people die every year due to diarrheal related diseases, with infants and the elderly making up the majority of these deaths. Deaths are caused by excessive intestinal fluid and electrolyte secretion and are especially common in impoverished developing countries. Antibiotics have been classically used as a method to treat diarrhea-related pathologies by modulating the gut microbiome. We recently reported that penicillin may protect against disease-induced excessive fluid and electrolyte secretion via a genetics-independent, microbiome-independent mechanism in individual colonic crypt cells. In this study we investigated whether microbial-independent protective effects of penicillin against fluid secretion can be observed in the rat small intestine at the whole-tissue level. Here we report that penicillin has a significant dose-dependent protective effect against fluid secretion in induced models of diarrhea in the microbiome deficient rat small intestine. Penicillin can rapidly bring fluid secretion down to levels comparable to healthy controls. Our results suggest, for the first time, an alternative function for penicillin G as a cost-effective and fast-acting treatment against diarrheal symptoms without dependence on modulating the behavior of the existing gut microbiome.