Visualization of Sympathetic Neural Innervation in Human White Adipose Tissue

Abstract

Obesity, defined as an excess of adipose tissue that adversely affects health, is a major cause of morbidity and mortality. However, understanding the structure and function of human adipose tissue has been limited by the inability to visualize cellular components due to the innate structure of adipocytes, which are characterized by large lipid droplets. Combining the iDISCO and the CUBIC protocols for whole tissue staining and optical clearing, we developed a protocol to enable immunostaining and clearing of human subcutaneous white adipose tissue (WAT) obtained from individuals with severe obesity. We were able to perform immunolabeling of sympathetic nerve terminals in whole white adipose tissue and subsequent optical clearing by eliminating lipids to render the opaque tissue completely transparent. We then used light sheet confocal microscopy to visualize innervation of human WAT from obese individuals in a 3D manner.We demonstrate the visualization of sympathetic nerve terminals in human WAT. This protocol can be modified to visualize other structures such as blood vessels involved in the development, maintenance and function of human adipose tissue in health and disease.