Exploratory investigation of the spatial relationships of collagen and nerves in subcutaneous white adipose tissue (scWAT) using 2-photon microscopy

摘要

In obesity, subcutaneous white adipose tissue (scWAT) is often marked by reduced adipogenesis, hypoxia, adipocytehypertrophy, and impaired lipolysis, all of which contribute to overall metabolic dysfunction. The role of the peripheralnervous system is appreciated in the control of WAT lipolysis; sympathetic denervation in WAT blocks lipolysis to avariety of lipolytic stimuli. Yet, we believe additional processes and work is needed to more fully understand adiposehypertrophy. Obese adipose tissue is fibrotic with excess deposition of collagen, yet there is limited work demonstratingthe impact of fibrosis on overall tissues structure and peripheral nerves of the scWAT. Here we present a multiphotonapproach to image both the peripheral nerves labeled with Alexa 488 and collagen via Second Harmonic Generation(SHG) imaging to investigate the impact of obesity and related fibrosis. The degree of colocalization between the nerveand collagen tissues was examined using both the Pearson’s coefficient and a recently adapted astrophysics technique,the Metric Space Technique (MST). In preliminary findings, both colocalization approaches demonstrated an increasecolocalization of nerve and collagen in the aged and obese mice. The MST technique has multiple output functions thatare used to examine morphological features such as structure of the nerve/collagen network as well as the circularity ofthese structures. Both colocalization techniques showed different in the obese mice and indicated a more diffuse circularnerve/collagen network. Collectively, these metrics provide important quantification of the nerve/collagen interactionand the role of the peripheral nervous function in maintaining appropriate adipose function.