Figure 10.

A missing endocrine system MicroFormulator (MES-µF) that could help recapitulate human endocrine regulation in vitro for microphysiological homunculi without the need to implement multiple, interlinked endocrine organs. A) Standard biology uses multiple endocrine organs (Organ₁ to Organ_N) to release numerous hormones (Hormone₁ to Hormone_N) that can engage with a targeted end organ. Instead of recreating the entire network of endocrine organs within an MPS homunculus, the MES-µF (B) combines the function of multiple endocrine organs into a single unit capable of recreating N endocrine organs by the time-dependent delivery of N hormones. The endocrine MicroFormulator contains a variety of vessels that each contain an important chemical messenger for the target organ. The MES-µF would either operate based upon an internally programmed clock or could sense the homeostatic state of the MPS homunculus in its entirety or simply that of a single target organ and adjust the hormone concentrations in a fashion similar to the feedback loops present in normal human biological endocrine modulation.