The ability of brown adipocytes (fat cells) to dissipate energy as heat shows 
great promise for the treatment of obesity and other metabolic disorders. 
Employing pluripotent stem cells, with an emphasis on directed differentiation, 
may overcome many issues currently associated with primary fat cell cultures. In 
addition, three-dimensional (3D) cell culture systems are needed to better 
understand the role of brown adipocytes in energy balance and treating obesity. 
To address this need, we created 3D "Brown-Fat-in-Microstrands" by microfluidic 
synthesis of alginate hydrogel microstrands that encapsulated cells and directly 
induced cell differentiation into brown adipocytes, using mouse embryonic stem 
cells (ESCs) as a model of pluripotent stem cells, and brown preadipocytes as a 
positive control. Brown adipocyte differentiation within microstrands was 
confirmed by immunocytochemistry and qPCR analysis of the expression of the 
brown adipocyte-defining marker uncoupling protein 1 (UCP1), as well as other 
general adipocyte markers. Cells within microstrands were responsive to a 
β-adrenergic agonist with an increase in gene expression of thermogenic UCP1, 
indicating that these "Brown-Fat-in-Microstrands" are functional. The ability to 
create "Brown-Fat-in-Microstrands" from pluripotent stem cells opens up a new 
arena to understanding brown adipogenesis and its implications in obesity and 
metabolic disorders.