We previously identified proliferative cells in adipose tissue expressing adipocyte specific genes and preadipocyte specific genes, which were named small proliferative adipocytes (SPA). Furthermore, we found that SPA specifically express proliferin (PLF) and have superior potential for adipogenic differentiation as compared to stromal vascular cells (SVC). In this study, we investigated the role of SPA. A comparison between differentiated SPA (D-SPA) and differentiated SVC (D-SVC) revealed that UCP1 and PLF were strongly expressed in D-SPA. Therefore, we speculated that SPA might be progenitor of beige cells. The real time PCR analyses and the immunohistochemical studies revealed that beige cells associated genes, including UCP1, PPARα and PGC1α were significantly increased in D-SPA. Treatment with pioglitazone and CL316234, a specific β3-adrenergic receptor agonist, converted cultured SPA into cell clusters like beige cells which expressed UCP1 and activation of mitochondrial function confirmed by MitoRed stain. Furthermore, PLF was expressed in beige cells induced by continuous injection of CL316243.
In conclusion, since D-SPA were found to express UCP1 and PLF, which were detected in beige cells, but not WAT, SPA were considered to be a progenitor of beige cells. There might be two lineages of cells in adipose tissue; adipose progenitor cells in SVC and WAT (PLF-), and SPA and beige cells (PLF+). The combination of pioglitazone and CL316423 produced an additive effect of inducing browning in SPA.
K. Taguchi: None. K. Kajita: None. M. Fuwa: None. M. Asano: None. Y. Kitada: None. T. Ikeda: None. T. Ishizuka: None. H. Morita: None.