Bioartificial endocrine organs: at the cutting edge of translational research in endocrinology

Bioartificial endocrine organs comprise classical endocrine glands, and soft (parenchyma) and hard (mineralized) tissue organs involved in endocrine-metabolic regulation. These bioconstructs are one of the newest promises of regenerative medicine, but their bioengineering "on the laboratory bench" and thus, outside the living body (i.e. ex situ) remains a substantial challenge [1, 2]. Based on current concepts [3-5], bioartificial endocrine organs can be engineered ex situ using macroscopic, three-dimensional (3D) scaffolds that mimic the 3D architecture of the native, organ stromal support (here coined organomorphism) reproduced with either natural or synthetic biomaterials. Once pluripotent stem cells, tissue-committed progenitors, and differentiated primary cells are seeded and co-cultured with the organomorphic scaffold, their self-assembly is expected up to the formation of a 3D macroscopic, functional and immuno-tolerant organ, replicating the native one. However, 3D systems exhibiting appropriate flow and trophic performance (bioreactor) are required to maximize homing, survival, growth, and differentiation/transdifferentiation of seeded elements [3, 6, 7]. Embryonic stem cells (ESCs) and induced pluripotent stem cells are also raising hopes as valuable sources to bioengineer human bioartificial viscera [8, 9]; thus, in the near future they may become another option to reconstruct ex situ bioartificial endocrine organs.