Ex vivo Analysis of Lipolysis in Human Subcutaneous Adipose Tissue Explants

Most studies of human adipose tissue (AT) metabolism and functionality have been performed in vitro on isolated mature adipocyte or in situ using the microdialysis technique (Lafontan, 2012). However, these approaches have several limitations. The use of mature isolated adipocytes is limiting as adipocytes are not in their physiological environment and the collagenase digestion process could affect both adipocyte survival and functionality. While metabolic studies using microdialysis have brought the advantage of studying the lipolytic response of the adipose tissue in situ, it provides only qualitative measures but does not give any information on the contribution of different adipose tissue cell components. Moreover, the number of microdialysis probes that can be used concomitantly in one subject is limited and can be influenced by local blood flow changes and by the molecular size cut-off of the microdialysis probe. Here we present a protocol to assess adipose tissue functionality ex vivo in AT explants allowing the studies of adipose tissue in its whole context, for several hours. In addition, the isolation of the different cell components to evaluate the cell-specific impact of lipolysis can be performed. We recently used the present protocol and demonstrated that fatty acid release during lipolysis impacts directly on a specific cell subset present in the adipose tissue stroma-vascular compartment. This assay can be adapted to address other research questions such as the effects of hormones or drugs treatment on the phenotype of the various cell types present in adipose tissue ( Gao et al., 2016 ).