Brown adipose tissue (BAT) is a potential target to treat cardiometabolic disorders because of its capacity to combust glucose and fatty acids for thermoregulation. Its cellular and molecular... Show moreBrown adipose tissue (BAT) is a potential target to treat cardiometabolic disorders because of its capacity to combust glucose and fatty acids for thermoregulation. Its cellular and molecular investigation in humans is hampered by the limited availability of cell material and the heterogeneity of BAT between and within individuals. In this study, monoclonal lines of conditionally immortalized brown preadipocytes (iBPAs) of mouse and human origin were generated. Conditional immortalization was achieved by doxycycline-controlled expression of simian virus 40 large tumor antigen (LT) with a repressor-based Tet-On system. In the presence of doxycycline, both the murine and human cell lines showed long-term proliferation capacity with a population doubling time of similar to 28 h. After switching off LT expression by doxycycline removal and exposure to adipogenic differentiation medium, cells from both species acquired brown adipocyte properties. This was evidenced by the accumulation of multilocular lipid droplets, the upregulation of brown adipocyte markers including uncoupling protein 1 and an increase in lipolysis and oxygen consumption following adrenergic stimulation. Switching off LT expression before the onset of adipogenic differentiation was only critical for inducing adipogenesis in the human iBPAs, while their murine counterparts showed adipogenesis upon exposure to the adipogenic differentiation cocktail regardless of LT expression. When switched to proliferation medium, cultures of adipogenically differentiated human iBPAs de-differentiated and resumed cell division without losing their adipogenic capacity. We suggest that iBPAs represent an easy-to-use model for fundamental and applied research into BAT offering unique experimental opportunities due to their capacity to switch between proliferative and differentiated states. Show less
Cell culture models play an important role in biomedical research and will continue to do so given the growing opposition to vivisection and the limited predictive value of animal models for... Show moreCell culture models play an important role in biomedical research and will continue to do so given the growing opposition to vivisection and the limited predictive value of animal models for human disease. Moreover, cell culture models can be easily established to mimic physiological or pathological processes, which is difficult to accomplish using in silico models. While non-cellular in vitro models are highly suitable for studying simple biochemical processes, cell culture models recapitulate many of the complex regulatory circuits governing protein activity in vivo and hence allow investigation of diverse physiological processes. Also, cell culture models offer the possibility to address fundamental research questions in a much more simplified, specific and controllable manner than can be achieved using in vivo models. Show less
