The important parts of a kidney have been replicated using 3D bio-printing at Harvard University. 
The pioneering development could make “organ transplant lists” obsolete reported 3D Printing Industry. The paper on how this was done was published early this October and its title is Bio-printing 3D Convoluted Renal Proximal Tubules on Perfusable Chips.
Within the structure of a kidney there are nephrons which are responsible for filtering waste from the body as well as absorbing nutrients from the blood, within the nephron are millions of proximal tubules (PT) and these are what make up a kidney.
The way this was done was to place a “PT structure on to a glass slide” and the extracellular matrix (which is what surrounds all cells in the human body) was injected over it. Once this was done the PT was removed from the structure which left a hollow mould where “living cells” were then injected into the space acting as a “guideline for the structure of a PT”. The cells grow and take on the “characteristics of a normal PT” which can then be used for testing new medication.
This process “follows the same sorting-out concept of cell manipulation” and has been used in “bio-printing a miniature heart and kidneys” in this instance the “sorting out” means that by giving cells a form to follow they will “eventually retain the order of the synthetic structure around them” meaning that they can operate as they would in the healthy body.
Jenifer Lewis is a professor at Harvard as well as an essential faculty member at the Wyss Institute for Biologically Inspired Engineering and the “lead researcher” on this project and is a leading name in the world of 3D bio-printing research.
The next challenge will be to organise the PTs into a “vascular structure” progressively constructing the tissue until “it is suitable to be transplanted”. A quote from the research paper said “Three-dimensional models of kidney tissue that recapitulate human responses are needed for drug screening, disease modelling, and, ultimately, kidney organ engineering. Our bio-printing method provides a new route for programmable fabricating advanced human kidney tissue models on demand.”