Seeing the trees in the forest: selective electroporation of adipocytes within adipose tissue

Electroporation has been recently adapted for the transfer of macromolecules into cells of tissues in vivo. Although mature adipocytes constitute < 20% of cells residing in adipose tissue, we hypothesized that fat cells might be susceptible to selective electro-transfer of plasmid DNA owing to their large size relative to other cells in the tissue. Results demonstrate the feasibility of electroporating DNA into mature fat cells with > 99% selectivity over other cells in the tissue. Further experiments used the "adiporation" technique to image the subcellular targeting of fluorescent bioreporter molecules to the nucleus, mitochondria, and lipid droplets of adipocytes within intact adipose tissue. Finally, we utilized fluorescent bioreporters to examine the effects of constitutive activation of the beta-adrenergic signaling pathway in adipocytes. These results demonstrate that overexpression of rat beta(1)-adrenergic receptors alters the cellular morphology of white adipocytes in a fashion that mimics the effects of systemic infusion of beta(3)-adrenergic receptor agonists. Hallmarks of the altered morphology include pronounced fragmentation of the single lipid droplet, repositioning of the nucleus, and induction of mitochondrial biogenesis. These results indicate that activation of beta-adrenergic signaling within adipocytes is sufficient to induce a phenotype that resembles typical brown adipocytes and suggest that in vivo electroporation will allow molecular dissection of the mechanisms involved.