Unravelling the developmental roadmap towards human brown adipose tissue

Increasing brown adipose tissue (BAT) mass and activation has been proposed as a potential therapeutic strategy to treat obesity and associated cardiometabolic complications. Given that obese and diabetic patients possess low amounts of BAT, an efficient way to expand their BAT mass would be necessary if BAT is to be useful. Currently, there is limited knowledge about how human BAT develops, differentiates, and is optimally activated. Moreover, to have access to human BAT is challenging, given its low volume and being anatomically dispersed. These constrain makes detailed mechanistic studies related to BAT development and function in humans virtually impossible. To overcome these limitations, we have developed a human-relevant new protocol for the differentiation of human pluripotent stem cells (hPSCs) into brown adipocytes (BAs). Unique to this protocol is that it is chemically-defined to recapitulate a physiological step-by-step developmental path of BAT that captures transient paraxial mesoderm and BAT progenitor states, on its way to reaching the adipocyte stage finally. These hPSC-derived BAs express brown adipocyte and thermogenic markers, are insulin sensitive, and respond to β-adrenergic stimuli. This new protocol is a scalable tool to study human BAs during development.