Dissecting the thermogenic adipose niche

Project Summary/Abstract Adipose tissue plays a critical role in the regulation of whole-body energy metabolism, and adipose dysfunction directly links to the etiology of several commonly seen metabolic diseases, such as type 2 diabetes mellitus and cardiovascular diseases. There are several different adipose depots dispersed throughout the body. White adipose tissue (WAT) is the primary site of the triglyceride storehouse. In contrast, thermogenic fat, which consists of classical brown adipose tissue (BAT) and inducible beige/brite fat, is specialized for thermogenic energy expenditure. In humans, individuals with detectable BAT have a significantly lower prevalence of cardiometabolic diseases, pointing to the metabolic benefits and therapeutic promise of BAT. Thermogenic adipose tissue can rapidly respond to environmental challenges by modulating cellular compositions and cell- to-cell interactions. Such adaptation is key to maintaining metabolic health. Intercellular communications within the thermogenic adipose niche orchestrate adipose tissue development and play an essential role in adipose tissue turnover, expansion, and remodeling in response to external stimuli. To dissect the complex cellular makeup of thermogenic fat, we performed single-cell RNA-sequencing analysis of BAT from mice housed at different temperatures. The results revealed a high degree of heterogeneity of thermogenic adipose niche and showed cold exposure induced dynamic changes of cellular composition in BAT. Importantly, we identified a novel population of adipose progenitor cells (APCs), which was derived from the vascular smooth muscle (VSM) lineage and uniquely expressed Trpv1 (transient receptor potential cation channel subfamily V member 1). Lineage tracing studies demonstrated that the Trpv1-expressing VSM-APCs could proliferate and differentiate into highly thermogenic adipocytes in response to cold stimulation. Work in progress showed that impaired adipogenic differentiation of Trpv1-expressing APCs resulted in reduced expression of thermogenic genes in BAT and WAT, suggesting an important role of these cells in thermoregulation. Additional preliminary data showed that the Trpv1-expressing APCs could respond to local signals and differentiate into thermogenic adipocytes. These exciting findings have led us to propose a model involving intercellular communications in which interplays between the APCs and inductive signals shapes adipocyte differentiation and function. In this proposal, we will test this hypothesis by determining the physiological role of the Trpv1-expressing APCs in metabolic regulation, identifying the endogenous and exogenous stimuli of Trpv1-positive APCs, and mapping the cellular interactome of the thermogenic adipose niche using computational tools and spatial transcriptomic analysis. Successful completion of the proposed studies will provide new insight into the role of intercellular communications in the regulation of adipose tissue development and function.